Spontaneous Droplet Uranium Extraction from Salt Lake Water Natural Falling

Spontaneous Droplet Uranium Extraction from Salt Lake Water Natural Falling | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Spontaneous Droplet Uranium Extraction from Salt Lake Water Natural Falling Xinyu Xue, Xianchun Jin, Lin Lei, Jinyan Du, Fuqiang Wang, Zhihe LONG, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5849443/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Mar, 2026 Read the published version in Nature Sustainability → Version 1 posted You are reading this latest preprint version Abstract Uranium as the nuclear energy fuel is critical for clean and efficient power generation, and its limited terrestrial reserves and environmentally harmful mining practices necessitate the development of alternative resources and sustainable uranium extraction technologies. In this study, we introduce an innovative droplet uranium extraction (DUE) approach, in which naturally falling salt lake water interacts with a three-layer Al-FEP-CTS@CF film, driving an in-situ electrochemical process for spontaneous uranium extraction without external power consumption. The superhydrophobic fluorinated ethylene propylene (FEP) layer induces solid-liquid interfacial interactions, converting falling water kinetic energy into electricity. At the same time, the selective reduction of uranium ions takes place at chitosan (CTS) functionalized adsorption sites on carbon felt (CF), precipitating out uranium peroxide hydrate. The DUE method achieves a high uranium extraction efficiency of 58% for the first droplet of 1000 mg/L uranium aqueous solution and maintains efficiency above 55% for subsequent droplets. The DUE method has an extraction capacity of 1250.6 mg/g, surpassing conventional adsorption methods by ~ 26 times. Field experiments in real salt lake environment with high-salinity condition validate the scalability and adaptability of DUE, successfully extracting final products of MgU 2 O 7 and Na 2 U 7 O 22 from brine water flows. This zero-consumption technology provides a scalable, economical, and environmentally sustainable way for uranium resource exploitation, and can conveniently extend to other aqueous mineral extraction. One-Sentence Summary : We introduce a zero-consumption and scalable Droplet Uranium Extraction (DUE) method that uses naturally falling salt lake water to drive in-situ electrochemical process for spontaneous uranium extraction, successfully validated in high-salinity salt lake environments with the final products of MgU 2 O 7 and Na 2 U 7 O 22 from brine flows. Physical sciences/Energy science and technology/Energy harvesting/Devices for energy harvesting Physical sciences/Materials science/Materials for energy and catalysis/Electrochemistry Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 INTRODUCTION Nuclear energy is widely recognized as a clean and efficient power source, and uranium is the key nuclear fuel [1,2]. Terrestrial uranium resources are finite and unevenly distributed globally, and conventional uranium mining poses significant environmental damage, necessitating the exploration of alternative resources and more sustainable extraction technologies [3]. Among uranium-containing water bodies, e.g. sea, salt lake and underground water, salt lake exhibits elevated uranium concentrations in high-evaporation regions, presenting a promising candidate for uranium extraction [4,5]. Traditional aqueous uranium extraction methods, such as solvent extraction, adsorption, and chemical precipitation, are commonly employed for their simplicity and scalability [6]. Despite their practicality, these methods have low uranium extraction efficiency and rely heavily on large quantities of organic solvents, which may lead to environmental pollution and require prolonged processing time [7]. Recent advancements in electrocatalysis [8–13] and photocatalysis [14] have exhibited potentials for enhancing aqueous uranium extraction efficiency. Electrocatalysis enables the precise reduction of uranium ions in aqueous solution, and also has high efficiency and scalability. Nevertheless, its power supply demands and the need for complex infrastructure pose substantial difficulty to widespread application [15,16]. Photocatalysis utilizes solar energy to extract uranium, providing an environmentally friendly and sustainable method. However, its effectiveness is restrained by low-light condition, alongside slow reaction rate and frequent catalyst replacement [17,18]. Salt lake features naturally or artificially induced water flows descending from higher to lower elevations, and the stream may be a previously untapped energy source for uranium extraction [19]. Besides of the typically low uranium concentrations in salt lake (100–200 µg/L), the high levels of competing ions, such as magnesium (~ 50 g/L), sodium (~ 50 g/L), and potassium (~ 9 g/L), present substantial obstacles to selective uranium extraction [20]. To overcome these challenges, it requires to develop a fundamentally new uranium extraction mechanism of utilizing falling water kinetic energy and highly selective materials that enables efficient sustainable uranium extraction while suppressing interference from co-existing ions [21]. Here, we present a novel droplet uranium extraction (DUE) approach that salt lake water naturally falling on a three-layer Al-FEP-CTS@CF film drives an in-situ electrochemical process for spontaneous uranium extraction without power consumption. The solid-liquid interfacial interactions on the surface of superhydrophobic fluorinated ethylene propylene (FEP) layer convert falling water kinetic energy into electricity. Uranium ions are simultaneously reduced into uranium peroxide hydrate precipitate at chitosan (CTS) selective adsorption sites on carbon felt (CF) with minimal co-deposition of competing impurities. A high uranium extraction efficiency of 58% for the first droplet of 1000 mg/L uranium aqueous solution has been obtained, and the efficiency maintains > 55% for subsequent droplets. The DUE method exhibits an exceptional uranium extraction capacity of 1250.6 mg/g, exceeding traditional adsorption methods by ~ 26 times. The scalability and adaptability of DUE are demonstrated through field experiments conducted in real salt lake environment with highly saline condition. Upon salt lake water naturally falling on a 4-step device equipped with DUE films, uranium is successfully extracted with the final products of MgU 2 O 7 and Na 2 U 7 O 22 . This zero-consumption technology can promote the development of scalable, economical, and environmentally sustainable uranium resource exploitation, and may offer considerable potential for other aqueous mineral extraction at the industrial level. RESULTS Design of DUE approach Salt lake presents a promising and underexplored resource for sustainable uranium extraction, offering distinct topographical and hydrological features ideal for harnessing mechanical energy from descending brine water streams, driven by natural elevation gradients or artificial control. As shown in Fig. 1 a, a multi-step DUE device can be designed and installed on the shore of salt lake like a water conservancy project, and the brine water can flow down the steps with DUE film equipped. The water is segmented into controlled streams and transformed into high-frequency droplets at each step, enabling continuous and scalable operation. Figure 1 b shows the three-layer material configuration of DUE film, consisting of Al electrode as the upper layer, ICP-etched FEP membrane as the middle layer, and CTS@CF as the base. The Al electrode functions as a charge reservoir, resulting in charge separation upon droplet impacting, initiating the in-situ electrochemical processes [22]. The superhydrophobic FEP membrane induces solid-liquid interfacial interactions and facilitates rapid droplet detachment to minimize energy losses [23]. The CTS@CF acts as an active site for the electrochemical reaction of uranium extraction. CTS can selectively adsorb uranium ions (UO 2 2+ ) and reduces interference from competing ions such as magnesium (Mg 2+ ) and sodium (Na + ) [24,25]. The electrochemical reduction of UO 2 2+ can produce less soluble uranium species, thereby enabling efficient uranium extraction. Figure 1 c illustrates the scalability of the film, emphasizing its flexibility and adaptability, which enable seamless deployment across diverse salt lake environments and terrains. Figure 1 d illustrates the color change of CTS@CF before and after DUE, changing from black to bright yellow, visually confirming the successful deposition of uranium species. Furthermore, under UV irradiation, the distinct green fluorescence emitted by uranium species serves as a definitive verification of their presence after DUE [26]. Figure 1 e shows the probable working principle of DUE process, which outlines three steps. In Step I, before impacting on DUE film, the electroneutral droplet naturally falls down. The superhydrophobic FEP membrane, acting as an electret material, retains negative charges to establish an electrostatic potential [27]. UO 2 2+ and competing ions are distributed within the aqueous solution surrounding CTS@CF, and UO 2 2+ ions are selectively adsorbed on CTS functional sites because CTS can preferably bind UO 2 2+ ions through abundant -NH 2 and -OH groups in the structure [28]. In Step II, the droplet fully contacts with FEP membrane. Due to the negative electrostatic potential of FEP membrane, the positive and negative charges in the droplet are separated. The positive charges appear close to FEP and form electric double layers (EDLs), and the negative charges appear on the opposite side [29]. The droplet then spreads to contact with Al electrode and transfers negative charges to the DUE film. The UO 2 2+ ions selectively adsorbed on CTS functional groups are reduced electrochemically to form less soluble uranium species, such as uranium peroxide hydrate precipitate, (UO 2 )O 2 ·2H 2 O. In Step III, the droplet detaches from the surface due to the superhydrophobic properties of FEP membrane. The departing droplet retains positive charges due to charge transfer during the step above, as confirmed in Fig. S1 . The quantity of positive charges carried by droplets is tested across different Weber numbers (We), defined as We = ρDv 2 /γ, where ρ, D, v and γ are respectively the density, diameter, impacting velocity and surface tension of the droplet. It shows an increased in transferred charge from ~ 7 nC to ~ 19 nC as the We number rises from ~ 10 to ~ 80, eventually stabilizing. Many research groups also observe such a phenomenon of departing droplet carrying positive charges [22,30–32]. The process of droplet impacting and departing can be approximately equivalent to providing negative charges to DUE film, which leads to the in-situ electrochemical reduction of selectively adsorbed UO 2 2+ . Figure 1 f shows the comparison of cost and efficiency between recent aqueous uranium extraction methods and our DUE approach. DUE offers very low cost and remarkable energy efficiency, and no external power supply is required. The utilization of natural mechanical energy from salt lake water flows substantially reduces operational costs while maintaining high extraction efficiency. Maximum extraction efficiency of 603.2 mg/Wh has been achieved, which surpasses conventional technologies [9–14] and provides a scalable solution for industrial uranium extraction with minimal environmental influence ( Supplementary Note 1 ). Characterization of DUE film Figure 2 provides a detailed depiction of the material structure and electrical characteristics of DUE film. Figure 2 a shows that the DUE film incorporates a modular three-layer structure, comprising Al electrode (green), superhydrophobic FEP membrane (purple), and CTS@CF (gray). The FEP membrane undergoes ICP etching, forming micro-nano structures that mimic the surface morphology of lotus leaves, as shown in Fig. 2 b and Fig. S2 . The 3D optical surface profile reveals a surface roughness of 0.91 for the FEP membrane, a key factor in its superhydrophobicity, as evidenced by a contact angle of 158° (Fig. 2 c). This engineered surface improves droplet detachment efficiency and stabilizes the Cassie-Baxter state, as demonstrated by confocal laser scanning microscopy in Fig. 2 d, which visualizes the solid-liquid-gas triple-phase contact line [33]. The Scanning Electron Microscopy (SEM) image of CTS@CF is shown in Fig. 2 e, and the fibers have average diameter of 8–10 µm and exhibit three-dimensional porous structure. Energy Dispersive Spectroscopy (EDS) mapping in Fig. S3 confirms that CTS is uniformly coated on the surface of CF. X-ray photoelectron spectroscopy (XPS) analysis in Fig. 2 f and Fig. S4 show that the peaks around 398, 284, and 408 eV of CTS@CF can be attributed to -NH 2 , C-N/C-O/O-C = O, and C = N-O, respectively [10]. Fourier-transform infrared (FTIR) spectra in Fig. 2 g further support these findings, displaying prominent N-H and O-H stretching vibrations at 3406 cm − ¹ and 3157 cm − ¹, along with C = O stretching bands at 1636 cm − ¹ and 1686 cm − ¹ [28]. These functional groups improve the hydrophilicity of CTS@CF, as evidenced by wettability tests in Fig. 2 h, enabling effective interaction with solutions. As shown in Fig. S5 , the high zeta potential ~ 63.4 mV of CTS@CF ensures the relative stability at 100 mg/L initial uranium concentrations [34]. Figure 2 i & j show the electric output of DUE film (area:16 cm 2 , positioned at a 45° incline) under water droplets (10 µL per droplet, 100 mg/L UO 2 (NO 3 ) 2 ·6H 2 O) released from a height of 20 cm and impacting at a frequency of 2.5 Hz. The outputting voltage (open circuit) consistently exceeds 200 V, and the outputting current (short circuit) maintains > 1 mA. By optimizing the external load resistance to ~ 10 4 Ω, the film achieves a power output of approximately 90 mW (Fig. 2 k), reflecting efficient energy utilization. Durability tests performed over 30 days (Fig. 2 l) validate the stability of the film, with outputting voltage keeping > 200 V. The high and stable electric output can efficiently enable the reduction of UO 2 2+ adsorbed on CTS@CF for prolonged periods. We also conduct high-frequency droplet impacting experiments to investigate the adaptability of the film to torrent water condition. It is worth noting that the droplet flow at 100 Hz almost appears as a continuous water flow (Fig. 2 m), similar to salt lake water falling. Under 100 Hz droplet impacting, the output of the film maintains at a stable voltage of ~ 200 V and a stable current of ~ 0.6 mA ( Fig. S6 ). In Fig. 2 n, frequency variation experiments further validate the film's robustness, with voltage output fluctuating around 200 V observed across a wide range of impacting frequencies from 100 Hz to 180 Hz. The output performance of DUE film is influenced by both droplet volume and release height, as shown in Fig. 2 o and Fig. S7 . At 100 Hz, as the droplet volume increases from 1 µL to 10 µL, the voltage output gradually rises and stabilizes at approximately 200 V. As the release height increases from 5 cm to 20 cm, the voltage output steadily increases from 40 V to about 200 V, remaining stable beyond 20 cm. Additionally, FEP membrane with superhydrophobic surface yields the highest voltage (~ 200V) output under high-frequency droplet impacting (Fig. 2 p), outperforming hydrophilic surface (~ 0.08 V) and hydrophobic surface (~ 26 V). These results show that superhydrophobic surface engineering optimizes energy transfer through efficient droplet departing while ensuring the film's stability and efficiency under torrent water conditions, making it ideal for applications in salt lake environments [23]. In-situ analysis of DUE process Figure 3 a shows the in-situ alpha (α) pulse detection system for analyzing the instantaneous uranium extraction quantity during DUE process, which leverages the radioactive decay properties of uranium isotopes (primarily U-238). The experiments here utilize 1000 mg/L UO 2 (NO 3 ) 2 ·6H 2 O aqueous solution, with droplets (10 µL per droplet) released from a height of 20 cm onto the DUE film (area:16 cm 2 , positioned at a 45° incline). The analysis is conducted by using a detector placed parallel to the DUE film, which provides immediate feedback on uranium extraction quantity when α particles composed of two protons and two neutrons are emitted during uranium decay to the stable thorium-234 (Th-234) [35]. The detection system, incorporating a charge-sensitive preamplifier and shaping amplifier, converts α-particle-induced charge signals into voltage signals. The signals are subsequently processed via an analog-to-digital converter, generating quasi-gaussian pulse signals, as shown in Fig. 3 b. By applying a well-defined threshold value, the system can precisely identify and count pulse voltage signals produced by individual α-particles, as shown in Fig. 3 c. This methodology ensures high-resolution and reliable detection of uranium extraction quantity on the DUE film. Measurements are conducted at different droplet counts (1, 5, 10, and 15 droplets) to evaluate the instantaneous uranium extraction quantity in situ, as shown in Fig. 3 d. Each pulse corresponds to a single α-particle emission, directly indicating uranium quantity. Red pulse counts represent uranium extracted on the DUE film, while yellow pulse counts represent the total uranium in the droplets. As shown in Fig. 3 e, by calculating the ratio of red pulse counts to yellow pulse counts, extraction efficiencies of 58%, 56%, 56%, and 55% are recorded upon 1, 5, 10, and 15 droplets, respectively. These results demonstrate very high efficiency of DUE process, and consistent performance across successive cycles emphasizes the reliability of repeated operations. Uranium extraction of DUE film is also confirmed through UV fluorescence imaging, as shown in Fig. 3 f. The CTS@CF exhibits distinct green fluorescence, with intensity increasing proportionally to the number of droplets. This optical evidence closely aligns with α-particle detection results, further validating the success of DUE. The consistent correlation between fluorescence intensity and α-particle counts underscores the robustness and reliability of the monitoring protocol. In contrast, Fig. S8 shows that fluorescence almost cannot be observed on the sample without FEP membrane. For this control sample, only adsorption of uranium can take place on CTS@CF, and no electrochemical process can occur, leading to low uranium extraction efficiency. Ex-situ analysis of DUE process Figure 4 shows the ex-situ analysis of DUE process, including the morphological evolution and physicochemical transformations of uranium species throughout successive droplet extraction cycles. Figure 4 a shows atomic contrast transmission electron microscopy (AC-TEM) images of CTS@CF surface at varying droplet counts, demonstrating morphological changes. After the first droplet impacting, atomic-scale bright spots, marked with red circles, can be observed on CTS@CF surface, indicating the initial capture and reduction of UO 2 2+ as atomically dispersed uranium species on adsorption sites. After the fifth droplet impacting, the dispersed species aggregated into small clusters. After the tenth droplet impacting, the clusters nucleated and crystallized into nanocrystals. After the fifteenth droplet impacting, the nanocrystals subsequently coalesced into nanosheets with an approximate thickness of ~ 7 nm. This morphological change comprises the following sequential stages: (1) adsorption and reduction; (2) aggregation into clusters; (3) nucleation and crystallization; and (4) growth into nanosheets. To demonstrate the chemical changes occurring on CTS@CF surface after one single droplet falls onto the DUE film, we employ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to investigate the valence states and coordination environments of uranium species [11,13,36]. Figure 4 b shows that the U L-edge XANES spectrum exhibits a white-line peak at 17175.7 eV, indicative of electron transitions from U 2p to unoccupied U 6d states. The absorption edge of uranium deposited on DUE film is located between the absorption edges of UO 2 and UO 2 (NO 3 ) 2 , indicating that the valence states of uranium cations are between + 4 and + 6. Fourier-transformed (FT) k²-weighted EXAFS spectra in R-space and k-space with experimental data and fitted curve (Fig. 4 c & d , Supplementary Table 1 ) reveal the local chemical environment of uranium on CTS@CF surface. The oscillation frequency of EXAFS in R-space also differs from UO 2 (NO 3 ) 2 , indicating changes in the oxidation state of uranium and rearrangement of local atomic structures during the electrochemical reaction process. The EXAFS in k-space fitting results show two major peaks at 1.4 Å and 1.8 Å, corresponding to axial oxygen (U-Oax) and equatorial oxygen (U-Oeq), respectively. The coordination number analysis results show that U-Oax has a coordination number of 2.9, and U-Oeq has a coordination number of 3.6. These findings confirm the formation of a stable 3Oax-1U-4Oeq structure on CTS@CF surface. Wavelet transform (WT) analysis in Fig. 4 e and Fig. S9 further supports the reduction of UO 2 2+ by exhibiting intensity shifts by 6 Å⁻¹, which are consistent with changes in the coordination environments of uranium during DUE process. Molecular dynamics (MD) simulations are conducted to provide detailed insights into the physicochemical interactions involved during DUE process ( Fig. S10 ). The mechanistic process of DUE is schematically illustrated in Fig. 4 f. The DUE film carries negative charges from droplet-electricity effect and generates a strong electrostatic field, driving the positively charged UO 2 2+ ions migrating toward the film. The UO 2 2+ ions undergo selective adsorption at the functional sites of CTS and are then reduced through in-situ electrochemical reactions. This effect of electrostatic attraction combined with selective adsorption significantly enhances the reduction efficiency of UO 2 2+ . Figure 4 g shows the potential of mean force (PMF) analysis for the simulated mechanistic process of UO 2 2+ ion migration under an electrostatic field [37]. The results show that after applying the electrostatic field, the surface potential energy of UO 2 2+ ions decreases from − 0.38 kJ/mol to -0.51 kJ/mol, indicating a stronger inclination of ions to adsorb onto CTS@CF. The probability density distribution analysis in Fig. 4 h also reveals that the surface UO 2 2+ ion density increases from approximately 2.5 to 3.5. This further confirms that the electrostatic field at CTS@CF surface more effectively stabilizes UO 2 2+ ions. The mean square displacement (MSD) analysis (Fig. 4 i) indicates that the migration rate of UO 2 2+ significantly decreases after the electrostatic field is applied, with an MSD value of 2000 within 10 ns, compared to 4000 before the field is applied [38]. This observation suggests the formation of a unique stable adsorption layer on the functionalized surface. Radial distribution function (G(r)) analysis (Fig. 4 j) shows a pronounced peak for U-N coordination at ~ 4.2 Å (intensity ~ 2.2), indicating strong interactions between UO 2 2+ and CTS, primarily within a short range (< 5 Å). In contrast, U-C coordination exhibits a lower peak (intensity ~ 1.0) with a broader distribution (6–10 Å), reflecting weaker interactions and lower stability [39]. These findings suggest that the electrostatic field preferentially promotes U-N coordination over U-C interactions, thereby strengthening the binding of UO 2 2+ to CTS and enhancing adsorption. Uranium species extracted A 12-stage experimental equipment is constructed to extract uranium species during DUE process under dynamic flow conditions without external power supply, as shown in Fig. 5 a. The multi-stage design fully enables energy conversion across stages and allows adequate uranium extraction as the water flows through many stages. This experimental setup is also a rehearsal for the field tests in real salt lake environments. The experiment processes a total of 3 L of UO 2 (NO 3 ) 2 ·6H 2 O aqueous solution at varying concentrations, with 100 Hz droplets (10 µL per droplet) impacting. Each stage is equipped with DUE film (16 cm 2 ), and the height between each stage is approximately 20 cm. Each stage ensures smooth water flow, facilitates high-frequency droplet generation, and extends UO 2 2+ interaction time with the DUE film [40]. Figure 5 b shows that at an initial concentration of 100 mg/L, DUE approach achieves a significantly higher uranium extraction capacity (~ 162.3 mg/g within 2 hours and ~ 396.4 mg/g within 12 hours) compared to adsorption method (no FEP membrane), which plateaus at ~ 38.9 mg/g. The uranium extraction quantity is calculated by measuring the concentration of the solution before and after DUE. The uranium extraction efficiency of DUE and adsorption methods with 12 hours is about 84.2% and 8.3%, respectively. At other initial uranium concentrations (5, 50 and 1000 mg/L), superior efficiency of DUE approach compared to conventional adsorption method can also be observed, as shown in Fig. S11 . As shown in Fig. 5 c, at an initial concentration of 1000 mg/L, DUE approach achieves an extraction capacity of ~ 1250.6 mg/g after 12 hours, while the adsorption method exhibits saturation at a capacity of ~ 47.3 mg/g. The extraction capacity of DUE approach surpasses conventional adsorption method by ~ 26 times, underscoring its great application potentials. Uranium extraction quantity during DUE process (1000 mg/L) can also be evaluated by using electrochemical impedance spectroscopy (EIS), as shown in Fig. 5 d. The polarization resistance (Rp) of CTS@CF obtained through fitting decreased over time, from 375.1 Ω to 88.29 Ω, reflecting the progressive formation of conductive uranium species on CTS@CF surface ( Fig. S12 ). This conductive layer enhances electron transfer efficiency and may facilitate sustained extraction performance [10,41]. Visual evidence further corroborates these findings, as shown in Fig. 5 e. Under UV irradiation, after 6 hours of extraction at an initial uranium concentration of 1000 mg/L, the CTS@CF surface exhibits green fluorescence during DUE in the experimental environment. Simultaneously, the visual changes in Fig. 5 f show that the CTS@CF surface changes from black to yellow, while the yellow color of the aqueous solution completely fades, further validating the uranium extraction process. Figure 5 g shows that the pH value does not have a great influence on the extraction efficiency of DUE approach. The uranium extraction efficiency keeps above 80% with pH values ranging from 3 to 9. The selectivity is essential for DUE approach to extract uranium and suppress interference from co-existing ions due to the high levels of competing ions in real salt lake water. Figure 5 h shows the high selectivity of DUE approach towards UO 2 2+ . We test the extraction efficiency of U, V, Fe, Pb, Ca, Mg, and Cr from corresponding aqueous solution (UO 2 (NO 3 ) 2 ·6H 2 O, NH 4 VO 3 , FeCl 3 ·6H 2 O, Pb(NO 3 ) 2 , CaCl 2 , MgCl 2 ·6H 2 O, and CrCl 3 ·6H 2 O) with the same concentration of 100 mg/L. The extraction efficiency of U is higher than 80%, and the extraction efficiencies of other ions such as V, Fe, Pb, Ca, Mg, and Cr are merely 25.8%, 24.9%, 20.5%, 16.0%, 5.3%, and 2.2%, respectively. The high selectivity arises from the selective adsorption of UO 2 2+ on CTS, which is further analyzed using electrostatic surface potential (ESP) simulations ( Fig. S13 & S14 ). For comparison, V 5+ ion is selected as an example, which is widely recognized as a competitive ion for uranium adsorption and typically exists as HVO 4 2− in solution [5]. The CTS exhibits significant negative potential in adsorption site-related regions, with an ESP range of -18.83 to 18.83 kcal/mol. At the adsorption sites, the negatively charged region (blue area) on the CTS strongly attracts the positively charged UO 2 2+ , which features a highly localized positive potential with an ESP value of up to + 409.33 kcal/mol. This pronounced difference in ESP creates a favorable electrostatic environment for binding. In contrast, HVO 4 2− has an ESP range of -249.35 to -124.74 kcal/mol, characterized by a strongly negative potential. The negatively charged regions on CTS surface (blue areas) generate electrostatic repulsion toward HVO 4 2− , preventing stable binding. These findings provide a molecular-level explanation of the mechanism by which DUE films achieve efficient and selective extraction of UO 2 2+ from complex aqueous matrices. Furthermore, as shown in Fig. S15 & 16 , CTS@CF not only enhances the material’s hydrophilicity but also maintains the cleanliness of adsorption sites in natural water environments due to its inherent antibacterial properties, which prevent microbial biofouling and blockage of adsorption sites. Antibacterial tests show inhibition of E.coli and S.aureus , ensuring long-term activity and stability of the adsorption sites [42]. Detailed structural and compositional analyses are conducted to elucidate the extracted uranium species. SEM images in Fig. 5 i reveal obvious flake-like uranium deposits on the CTS@CF surface after 6 hours of DUE process at an initial 100 mg/L concentration. For the adsorption method (no FEP membrane), the surface of CTS@CF remains nearly smooth with minimal precipitate formation, as shown in Fig. S17 . These observations suggest a phase transformation pathway in which UO 2 2+ is reduced and crystallized on CTS@CF during DUE process. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis in Fig. 5 j demonstrates a uniform distribution of uranium across the CTS@CF surface after DUE, with signal intensities markedly higher than those for carbon (C) and nitrogen (N). Additionally, EDS mapping in Fig. 5 k confirms the formation of substantial uranium deposits on the CTS@CF surface and within the interstitial spaces after DUE. FTIR spectra (Fig. 5 l) further support these findings, showing the disappearance of the enhanced C = O stretching vibration peak at 1686 cm − 1 and the emergence of a U-O peak at 894 cm − 1 , indicative of UO 2 2+ adsorption and reduction during DUE [43]. The retention of O-H and N-H stretching peaks between 3406 cm⁻¹ and 3157 cm⁻¹ underscores the critical role of CTS functional groups in coordinating and binding UO 2 2+ during DUE. We then analyze the uranium deposits simply peeled off from the CTS@CF surface after DUE. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) analysis in Fig. 5 m provides further insights, revealing lattice spacing of 0.32 nm in the uranium deposits, corresponding to the (200) crystal plane of uranium peroxide hydrate, (UO 2 )O 2 ·2H 2 O, and confirming the crystalline nature of the extracted uranium. Consistent with these results, EDS image (Fig. 5 n) shows the uniform distribution of uranium and oxygen on the surface of uranium deposits. The valence state of uranium precipitates after DUE is studied through XPS U4f analysis (Fig. 5 o, Fig. S18). The spectrum reveals two primary peaks approximately 11.0 eV apart, along with a smaller peak on the higher binding energy side. The two main peaks at ~ 381.0 eV and ~ 392.0 eV are assigned to U4f 7/2 and U4f 5/2 primary peaks, respectively, while the smaller peak at ~ 398.6 eV corresponds to the satellite peak of U4f 5/2 . The 6.8 eV separation between the satellite peak and the U4f 5/2 primary peak indicates the presence of U(IV) in the uranium extracted after DUE [44]. Fitting results further confirm the dominance of U(IV) content, in sharp contrast to uranium species extracted by adsorption, which are primarily composed of U(VI). Through X-ray diffraction (XRD) analysis in Fig. 5 p, it confirms (UO 2 )O 2 ·2H 2 O as the dominant crystalline phase and also identifies it as the metastudtite. This result is consistent with previous studies where similar species were primarily identified using electrochemical methods [9,10]. Finally, α-particle decay spectra measurements of our samples compared to pure samples (U238, Pu239, Pu238) demonstrate that their radioactivity closely resembles that of U238, further validating the radioactive properties of the post-extraction samples ( Fig. S19 ). Field experiments in real salt lake environment The effectiveness of DUE approach for industrial-scale uranium extraction is demonstrated through field experiments in real salt lake environment with highly saline water condition, as shown in Fig. 6 a. The brine water, representative of the complex ionic composition of saline environments, contains uranium (~ 173 µg/L) alongside competing ions, including Mg 2+ (~ 58.9 g/L), Na + (~ 58.2 g/L), K + (~ 8.5 g/L), and Ca 2+ (~ 2.2 g/L). A 4-step cascading device is positioned beneath the brine water pipeline to enable efficient uranium extraction. By harnessing falling water kinetic energy, the DUE device processes large volumes of brine water continuously across multiple steps, surpassing the limitations of laboratory-scale setups. Figure 6 b shows the detailed structure of the 4-step cascading device, and the height between each stage is ~ 20 cm, equipped with DUE films on each step (area:100 cm 2 ). As shown in Fig. 6 c, during operation, uranium extraction becomes visually apparent as the color of CTS@CF surface changing from black to some yellow spots after 20 hours, and almost all of the surface turns yellow after 40 hours. The distinct green fluorescence observed under UV light confirms uranium extraction. After extraction, the uranium deposits are peeled off from the CTS@CF, dissolved in water, and filtered to yield a concentrated uranium product, as shown in Fig. 6 d. The process is not only environmentally friendly but also operationally simple, requiring no organic solvents and utilizing easily scalable techniques. The final products, observed as fine yellow powders collected on filter paper, exhibit large agglomerated uranium-containing particles, as revealed by SEM imaging (Fig. 6 e). EDS mapping and spectrum in Fig. 6 f & g confirm that U is the dominant element in the final products, with the presence of O, Mg and Na elements. XRD analysis in Fig. 6 h identifies MgU 2 O 7 and Na 2 U 7 O 22 as the predominant crystalline phases. These findings are consistent with previous reports, indicating that UO 2 2+ may firstly be reduced to low-valence uranium species and then react with dissolved oxygen and metal ions under alkaline conditions to form urinates [45]. As the concentrations of Na + and Mg 2+ in salt lake environments are high, these ions likely influence uranium reduction processes, forming valuable intermediates for nuclear fuel production. The modular cascading DUE device allows for site-specific adjustments in dimensions and stage heights, ensuring consistent efficiency across various salt lake environments. The device can also seamlessly integrate into existing industrial workflows, such as lithium extraction and potassium fertilizer production, by using shared saltwater pipelines and infrastructure [46,47]. This integration reduces operational costs and enhances resource utilization, providing a scalable and economically viable solution for uranium extraction. The potential production of uranium from several major salt lakes around the world using the DUE method will be remarkable. Assuming a uranium concentration of ~ 150 µg/L in these salt lakes, and a DUE extraction efficiency of ~ 80%, Qarhan Salt Lake (biggest in Asia, ~ 500 million m³) could produce 60 tU, Great Salt Lake (biggest in North America, ~ 16 billion m³) 1,920 tU, Chott el Djerid Lake (biggest in Africa, ~ 7 billion m³) 840 tU, Salar de Uyuni (biggest in South America, ~ 5 billion m³) 600 tU, and Caspian Sea (biggest in Europe, ~ 78.2 trillion m³) 9.38 million tU. The huge total amount could meet the human demand for clean energy fuel, thereby partially replacing the terrestrial uranium reserves (~ 7.6 million tU globally), demonstrating the great potential of DUE method as a sustainable solution for uranium extraction. Additionally, by simply modifying selective adsorption sites for other metal ions on CF (replacing CTS), this zero-consumption technique can conveniently extend to other aqueous mineral extraction, such as rare earth and noble metal elements. DISCUSSION In summary, an innovative DUE approach is presented as a sustainable solution for spontaneously extracting uranium from mineral-rich salt lake. By leveraging the kinetic energy of descending water droplets, it drives a selective electrochemical process that reduces UO 2 2+ ions while minimizing impurity co-deposition. No external power supply is needed for the DUE process. The three-layer Al-FEP-CTS@CF material has both high efficiency and durability. The extraction efficiency is up to 58% for the first droplet, and keeps higher than 55% for subsequent droplets. MD simulations and advanced characterization techniques, including AC-TEM and XAFS, confirm crystallization of (UO 2 )O 2 ·2H 2 O after DUE. With an extraction capacity of 1250.6 mg/g, surpassing conventional adsorption method by ~ 26 times, the DUE method exhibits great application potentials. The field experiments in real salt lake environment demonstrate its scalability and adaptability at the industrial level, and the final products spontaneously extracted from brine water flows are MgU 2 O 7 and Na 2 U 7 O 22 . This zero-consumption, scalable, economical, and environmentally sustainable technique can promote the development of aqueous mineral exploitation, not only for uranium but also for other metal resources. MATERIALS AND METHODS Fabrication of DUE film The film comprised three components. The top layer was Al electrode with a width of 2 µm and length customizable according to experimental needs, and fixed onto the FEP membrane. Al electrode served as a charge reservoir and initiated the in-situ electrochemical processes. The middle layer was a piece of FEP membrane (Aladdin Shanghai Chemical Co., Ltd.) treated by ICP etching. The membrane was etched for 15 minutes using a mixed gas of argon, sulfur hexafluoride, and oxygen (volume ratio: 1:6:1) (Chengdu Runtai Specialty Gas Co., Ltd.), forming superhydrophobic surface. The bottom layer was CF coated with CTS (Condary Environmental New Materials Co., Ltd.). CF was first soaked in a 1% chitosan acetic acid solution, then neutralized in a 10% sodium hydroxide solution (Shanghai Macklin Biochemical Co., Ltd.), and finally dried at 40°C for 30 minutes to enhance stability. These three layers were precisely aligned and fixed during assembly to ensure the film's overall performance and stability. For fabricating a DUE film with an area of 16 cm 2 , the dimension of Al electrode was 10×0.0002×0.1 cm, 4×2×0.03 cm for FEP membrane, 4×4×0.1 cm for CTS@CF (the specific dimensions were described in terms of length, width, and height). For fabricating a DUE film with an area of 100 cm², the dimension of Al electrode was 25×0.0002×0.1 cm, 10×5×0.03 cm for FEP membrane, and 10×10×0.1 cm for CTS@CF. Characterizations and measurements Surface morphologies and microstructures were observed by using a Zeiss GeminiSEM 300, operating at 5 kV for high-resolution mapping and 15 kV for EDX elemental analysis. A Sensofar NEOX 90 optical profilometer was utilized for measuring the 3D optical surface profiles and assessing superhydrophobicity, while a Nikon A1 laser confocal microscope, equipped with a 532 nm laser, was employed to visualize interactions between uranium-containing water (100 mg/L) and FEP surface. To monitor changes in the contact angle and characterize surface wettability, an OCA-50AF goniometer was utilized. Surface functional groups and bonding states were analyzed using XPS (Thermo Fisher Scientific K-Alpha) and FTIR (Thermo Scientific Nicolet Summit), while the zeta potential of CTS@CF was measured using a Brookhaven zeta potential analyzer. The electric output of DUE film recorded with a Keithley 6517B electrometer, and the amount of positive charge carried by droplets was measured using a Faraday cup (Monroe model 284). For real-time assessments of alpha particle emissions and uranium extraction quantity, an in-situ alpha (α) pulse detection system equipped with CoMPASS software was employed. The surface fluorescence was observed by using a UV flashlight irradiation (wavelength: 365 nm). Microstructural lattice details were explored using AC-TEM (FEI Titan 80–300). Synchrotron radiation experiments conducted at SSRF (BL14W1, Shanghai, China.) collected U L3-edge XAS spectra, which were analyzed with Athena and Artemis software. Electrochemical impedance spectroscopy (EIS) was conducted using a CHI660E workstation over a frequency range of 0.01 to 10⁵ Hz. TOF-SIMS (PHI NanoTOFII) was used for high-resolution analysis of surface element distribution. HAADF-STEM and STEM-EDS (JEOL JEM-ARM300F) provided micro morphology and elemental mapping of CTS@CF. The crystal structure of the extracted uranium was analyzed using XRD (Rigaku SmartLab SE). To measure uranium extraction efficiency, a 1000 mg/L UO 2 (NO 3 ) 2 ·6H 2 O aqueous solution (~ 3 L, DUE film area: 16 cm 2 , stage height: ~ 20 cm) was utilized. The uranium extraction quantity was calculated by analyzing the solution concentration before and after DUE by using Arsenazo III and ICP-OES/ICP-MS. To demonstrate the high selectivity of DUE film, the extraction efficiencies of U, V, Fe, Pb, Ca, Mg, and Cr from corresponding aqueous solution (UO 2 (NO 3 ) 2 ·6H 2 O, NH 4 VO 3 , FeCl 3 ·6H 2 O, Pb(NO 3 ) 2 , CaCl 2 , MgCl 2 ·6H 2 O, and CrCl 3 ·6H 2 O) with the same concentration of 100 mg/L were tested (reagents sourced from Shanghai Macklin Biochemical Co., Ltd.). Adsorption experiments were performed by immersing CTS@CF (without FEP membrane) in the solution under conditions similar to DUE. The effects of initial uranium concentration (5-1000 mg/L) and solution pH (range: 3–9, uranium concentration: 100 mg/L) on extraction performance were systematically investigated. Field-scale experiments demonstrated the industrial feasibility of the DUE method in high-salinity brine water from Qarhan Salt Lake, Qinghai Province, China. The brine water contained uranium (~ 173 µg/L) and competing ions, including Mg 2+ (~ 58.9 g/L), Na + (~ 58.2 g/L), K + (~ 8.5 g/L), and Ca 2+ (~ 2.2 g/L). A 4-step cascading device, positioned beneath the brine water pipeline, was utilized to process large volumes of brine continuously using the kinetic energy of falling water. Each step incorporated a 100 cm² DUE film with a height difference of ~ 20 cm. All salt lake water had not undergone any prior treatment. MD simulations All MD simulations were conducted using the LAMMPS package, with trajectory visualization and analysis performed via VMD software. The systems consisted of CF, UO 2 2+ , H 2 O, and CTS. The OPLS-AA force field was employed for CTS and the electrode. Force field parameters for UO 2 2+ were derived from previous simulation studies [48]. For water molecules, when the electric field was applied, hydrogen atomic positions were constrained using the SHAKE and RATTLE algorithms. Non-bonded van der Waals interactions were modeled with the 12 − 6 Lennard-Jones potential, while electrostatic interactions, including long-range Coulombic forces, were handled via the particle-particle-particle mesh method. The simulation boxes measured 7.38 nm × 4.26 nm × 3.50 nm. They contained CF, 60 UO 2 2+ ions, 3200 H 2 O molecules, and CTS molecules. For the production runs, a time step of 1 fs was adopted, and data were recorded every 1 ps. The systems were minimized by optimizing atomic positions and cell dimensions while maintaining isotropic box lengths. Two independent trajectories of 1000 ps were generated for each system. Equilibration was performed in the microcanonical ensemble at 298 K and 1 bar pressure for 10 ps, followed by a microcanonical ensemble simulation at 298 K for 1000 ps to obtain system parameters. Periodic boundary conditions were applied in all directions. ESP simulations All computations were performed using the Gaussian 16 software package. The TPSSh functional, coupled with the D3BJ dispersion correction, was employed for the calculations [49]. Geometry optimizations and frequency analyses utilized the SDD basis set for uranium atoms and the def-TZVP basis set for other elements. To incorporate solvation effects, the polarizable continuum model (PCM) was applied. Wave function analyses were conducted using the Multiwfn 3.8(dev) program. The extrema of the electrostatic potential (ESP) on the van der Waals surface were determined through quantitative analysis of the electrostatic potential map. Isosurface representations were generated using the VMD visualization tool, based on output files from Multiwfn. Declarations Funding: This work was supported by National Natural Science Foundation of China (11674048 and 52371144), China Academy of Engineering Physics Foundation (YZJJZQ2023019), Sichuan Science and Technology Program (2024NSFSC0143 and 2024YFFK0333), Radiation Oncology Key Laboratory of Sichuan Province (2023ROKF03 and 2024ROKF06) and Natural Science Foundation of Sichuan Province (25QNJJ2559). Author contributions: Conceptualization: X.J., L.L., Y.H., X.Z., and X.X. Methodology: X.J., L.L., L.X., and X.X. Investigation: X.J., L.L, J.D., F.W., and Z.L. Visualization: X.J., L.L., and X.X. Funding acquisition: L.X., Y.H., X.Z., and X.X. Project administration: X.J., L.L., F.W., Y.H., X.Z., and X.X. Supervision: X.Z, and X.X. Writing – original draft: X.J., and X.X. Writing – review & editing: X.J., L.L., L.X., X.Z., and X.X. Competing interests: The authors declare no competing interest. 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Phys. Rev. Lett. 91 , 146401 (2003). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryMaterials.docx SUPPLEMENTARY INFORMATION Cite Share Download PDF Status: Published Journal Publication published 05 Mar, 2026 Read the published version in Nature Sustainability → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5849443","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":414068524,"identity":"ae929c67-41bc-4c7f-b9ed-e154ed4cf04f","order_by":0,"name":"Xinyu Xue","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIie3NsQrCMBCA4SuCk+h6QdRXiBRc9GESAnUp6OggWhDqIrjWtxAEcawU6tIHyKgInQud3ExFHdOOgvnhIIH7OACT6VdjalrfX1iVEO+zXYkU0bAqoVLEeDtF/CBFlGdz6DYls/KphpDAEZQnET9Kx8EwBptIVmsHGtJCt3/lfkHcAZw94HvJ6rWGhtRxkoUFOQSTPFNkWUrUFet1ZY8uoCKMlhGySW3K/bEdJOkAkxj7u+S2ausIvYiUPPxhZ7sW92w2H/WaF3HOdeTd6vNANZZXDgAWVZZMJpPpX3sCrnZSXM61JugAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-1379-6813","institution":"University of Electronic Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Xinyu","middleName":"","lastName":"Xue","suffix":""},{"id":414068525,"identity":"9acc0412-4de2-464b-80f3-a8b31d5fba25","order_by":1,"name":"Xianchun Jin","email":"","orcid":"","institution":"University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Xianchun","middleName":"","lastName":"Jin","suffix":""},{"id":414068526,"identity":"4ff6689c-09f1-4b42-9d93-5ed05321e997","order_by":2,"name":"Lin Lei","email":"","orcid":"","institution":"Institute of Materials, Chinese Academy of Engineering Physics","correspondingAuthor":false,"prefix":"","firstName":"Lin","middleName":"","lastName":"Lei","suffix":""},{"id":414068527,"identity":"9d3c759a-d18a-4a8c-b1d1-7df7e04049b1","order_by":3,"name":"Jinyan Du","email":"","orcid":"","institution":"University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Jinyan","middleName":"","lastName":"Du","suffix":""},{"id":414068528,"identity":"c1c095dd-9a41-4950-b755-3859c2050340","order_by":4,"name":"Fuqiang Wang","email":"","orcid":"","institution":"QingHai Salt Lake Industry Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Fuqiang","middleName":"","lastName":"Wang","suffix":""},{"id":414068529,"identity":"787d210a-3637-48dd-b177-2a8463814d98","order_by":5,"name":"Zhihe LONG","email":"","orcid":"https://orcid.org/0000-0003-3815-2029","institution":"University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Zhihe","middleName":"","lastName":"LONG","suffix":""},{"id":414068530,"identity":"cd988df9-9d9c-4cb4-8151-f1cc133d61cb","order_by":6,"name":"Yongping He","email":"","orcid":"","institution":"QingHai Salt Lake Industry Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yongping","middleName":"","lastName":"He","suffix":""},{"id":414068531,"identity":"b19e2e77-38d0-4229-b808-689a811725cf","order_by":7,"name":"Lili Xing","email":"","orcid":"","institution":"University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Lili","middleName":"","lastName":"Xing","suffix":""},{"id":414068532,"identity":"044e94b6-ec8b-4312-9dcb-faaa669c3858","order_by":8,"name":"Xiaochong Zhao","email":"","orcid":"","institution":"Institute of Materials, China Academy of Engineering Physics","correspondingAuthor":false,"prefix":"","firstName":"Xiaochong","middleName":"","lastName":"Zhao","suffix":""}],"badges":[],"createdAt":"2025-01-17 13:10:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5849443/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5849443/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41893-026-01781-3","type":"published","date":"2026-03-05T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":76105840,"identity":"69604382-04a6-438c-8b44-c2722b765432","added_by":"auto","created_at":"2025-02-12 11:11:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2285882,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign of DUE approach.\u003c/strong\u003e (a) A multi-step DUE device on the shore of salt lake, leveraging brine water falling to enable large-scale uranium extraction. (b) The three-layer material configuration of DUE film. (c) The scalability of DUE film. (d) The color change of CTS@CF surface before and after DUE. (e) The working principle of DUE process. (f) The comparison of cost and efficiency between recent aqueous uranium extraction methods and our DUE approach.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/ad0442a16f3887ff9a89635b.png"},{"id":76105855,"identity":"ae161159-401f-4c81-95a8-659b67edf3af","added_by":"auto","created_at":"2025-02-12 11:11:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1092410,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacterization of DUE film.\u003c/strong\u003e (a) Material structure of DUE film. (b) SEM image of the surface morphology of FEP membrane, complemented by an inset showing EDS mapping of the fluorine element. (c) The 3D optical surface profile of FEP membrane, complemented by an inset showing the droplet contact angle. (d) Laser confocal observations showing the solid-liquid-gas three-phase contact lines on FEP surface. (e) SEM image of CTS@CF. (f) XPS spectrum of CF and CTS@CF. (g) FTIR spectra of CF and CTS@CF. (h) Contact angle tests (10 μL of droplet) of CF and CTS@CF. (i) Voltage output of DUE film (area:16 cm\u003csup\u003e2\u003c/sup\u003e, positioned at a 45° incline) under water droplets (10 μL per droplet, 100 mg/L UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e·6H\u003csub\u003e2\u003c/sub\u003eO) released from a height of 20 cm and impacting at a frequency of 2.5 Hz. (j) Current output. (k) Power output measured across varying load resistances. (l) Long-term stability tests. (m) Photograph of high-frequency droplets impacting at 100 Hz. (n) Voltage output at different droplet frequency. (o) Voltage output at different droplet volume. (p) A comparison of voltage output under different surface wettability.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/da8da0ea088a14546f1ef3f1.png"},{"id":76105842,"identity":"fed952be-83ea-43b4-9769-7e8bd9bc9fd1","added_by":"auto","created_at":"2025-02-12 11:11:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1753286,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIn-situ analysis of DUE process. \u003c/strong\u003e(a) In-situ alpha pulse detection system for analyzing the instantaneous uranium extraction quantity during DUE process. (b) Flowchart of the charge signal processing. (c) A single alpha particle pulse signal, with pulse output and typical threshold shown in the inset. (d) α-particle emission for directly indicating uranium quantity. Red pulse counts: uranium extracted on the DUE film; yellow pulse counts: total uranium in the droplets. (e) DUE efficiency. (f) Fluorescence images of the sample surface under UV irradiation after DUE with different droplet numbers.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/1dfa158701eca0d2b7e49fa4.png"},{"id":76105841,"identity":"9b06e2f4-2be0-4e7f-8800-c45ee3226506","added_by":"auto","created_at":"2025-02-12 11:11:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2261923,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEx-situ analysis of DUE process. \u003c/strong\u003e(a) AC-TEM images of uranium depositions during DUE process. (b) Normalized XANES spectra of uranium samples after one single droplet impacting and XANES data of the reference standards of UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, U\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e, and UO\u003csub\u003e2\u003c/sub\u003e. (c) FT k²-weighted EXAFS spectra of uranium samples in R-space. (d) FT k²-weighted EXAFS spectra of uranium samples in k-space. (e) WT for the k²-weighted EXAFS spectra of uranium samples. (f) Schematic of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e distribution on CTS@CF after droplet impacting. (g) PMF profiles of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e along the z-axis before and after droplet impact. (h) Probability distribution of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e at different surface regions before and after droplet impact. (i) MSD analysis of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e mobility before and after extraction. (j) Radial distribution function (G(r)) analysis of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e interactions with matrix atoms.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/4a03196d8d7e5ebc57c4aab8.png"},{"id":76105872,"identity":"ced461ea-56e0-4a0c-b922-82ba4506d764","added_by":"auto","created_at":"2025-02-12 11:11:47","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2005100,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUranium species extracted.\u003c/strong\u003e (a) a 12-stage experimental DUE equipment for extracting uranium species. (b) Time-dependent uranium extraction quantity at an initial uranium solution concentration of 100 mg/L. (c) Uranium extraction quantity across various initial uranium concentrations. (d) Nyquist plots of the CTS@CF obtained by in situ EIS tests. (e) Fluorescence color change of CTS@CF surface under UV irradiation before and after DUE (1000 mg/L). (f) CTS@CF surface and uranium solution (1000 mg/L) before and after DUE. (g) Uranium extraction efficiency at different pH conditions. (h) Extraction efficiency for U and competing metal ions. (i) SEM image of CTS@CF after DUE. (j) TOF-SIMS image of CTS@CF after DUE. (k) EDS mapping of CTS@CF after DUE. (l) FTIR spectra of CTS@CF before and after DUE. (m) AC-TEM image of uranium deposits. (n) HAADF-STEM image and STEM-EDS mapping of uranium deposits. (o) XPS U4f spectrum of uranium precipitates. (p) XRD pattern of uranium precipitates.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/441dbca11cdd77cc204babff.png"},{"id":76105850,"identity":"f68089ab-d66e-4ba2-86d4-d914288cec13","added_by":"auto","created_at":"2025-02-12 11:11:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2297600,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eField experiments in real salt lake environment. \u003c/strong\u003e(a) A 4-step cascading device with DUE films deployed beneath the salt lake water pipeline. (b) Front and side views of the device. (c) Color changes of CTS@CF after 40 hours of DUE. (d) Peeling off products from CTS@CF. (e) SEM image of final products on filter paper. (f) EDS mapping and (g) spectrum of final products. (h) XRD pattern of final products.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/6354c565828713a896ab1731.png"},{"id":104052987,"identity":"500be69d-7e46-42d6-b0d7-51df69c4174c","added_by":"auto","created_at":"2026-03-06 08:06:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":15478753,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/68b9b209-ca18-4ccf-acfd-86864d9e8a65.pdf"},{"id":76105851,"identity":"d7f194d2-e682-4250-85ad-78d07a94e4a1","added_by":"auto","created_at":"2025-02-12 11:11:46","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1438389,"visible":true,"origin":"","legend":"SUPPLEMENTARY INFORMATION","description":"","filename":"SupplementaryMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-5849443/v1/533387494ce990645860a2a7.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Spontaneous Droplet Uranium Extraction from Salt Lake Water Natural Falling","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eNuclear energy is widely recognized as a clean and efficient power source, and uranium is the key nuclear fuel [1,2]. Terrestrial uranium resources are finite and unevenly distributed globally, and conventional uranium mining poses significant environmental damage, necessitating the exploration of alternative resources and more sustainable extraction technologies [3]. Among uranium-containing water bodies, e.g. sea, salt lake and underground water, salt lake exhibits elevated uranium concentrations in high-evaporation regions, presenting a promising candidate for uranium extraction [4,5]. Traditional aqueous uranium extraction methods, such as solvent extraction, adsorption, and chemical precipitation, are commonly employed for their simplicity and scalability [6]. Despite their practicality, these methods have low uranium extraction efficiency and rely heavily on large quantities of organic solvents, which may lead to environmental pollution and require prolonged processing time [7].\u003c/p\u003e \u003cp\u003eRecent advancements in electrocatalysis [8\u0026ndash;13] and photocatalysis [14] have exhibited potentials for enhancing aqueous uranium extraction efficiency. Electrocatalysis enables the precise reduction of uranium ions in aqueous solution, and also has high efficiency and scalability. Nevertheless, its power supply demands and the need for complex infrastructure pose substantial difficulty to widespread application [15,16]. Photocatalysis utilizes solar energy to extract uranium, providing an environmentally friendly and sustainable method. However, its effectiveness is restrained by low-light condition, alongside slow reaction rate and frequent catalyst replacement [17,18]. Salt lake features naturally or artificially induced water flows descending from higher to lower elevations, and the stream may be a previously untapped energy source for uranium extraction [19]. Besides of the typically low uranium concentrations in salt lake (100\u0026ndash;200 \u0026micro;g/L), the high levels of competing ions, such as magnesium (~\u0026thinsp;50 g/L), sodium (~\u0026thinsp;50 g/L), and potassium (~\u0026thinsp;9 g/L), present substantial obstacles to selective uranium extraction [20]. To overcome these challenges, it requires to develop a fundamentally new uranium extraction mechanism of utilizing falling water kinetic energy and highly selective materials that enables efficient sustainable uranium extraction while suppressing interference from co-existing ions [21].\u003c/p\u003e \u003cp\u003eHere, we present a novel droplet uranium extraction (DUE) approach that salt lake water naturally falling on a three-layer Al-FEP-CTS@CF film drives an in-situ electrochemical process for spontaneous uranium extraction without power consumption. The solid-liquid interfacial interactions on the surface of superhydrophobic fluorinated ethylene propylene (FEP) layer convert falling water kinetic energy into electricity. Uranium ions are simultaneously reduced into uranium peroxide hydrate precipitate at chitosan (CTS) selective adsorption sites on carbon felt (CF) with minimal co-deposition of competing impurities. A high uranium extraction efficiency of 58% for the first droplet of 1000 mg/L uranium aqueous solution has been obtained, and the efficiency maintains\u0026thinsp;\u0026gt;\u0026thinsp;55% for subsequent droplets. The DUE method exhibits an exceptional uranium extraction capacity of 1250.6 mg/g, exceeding traditional adsorption methods by ~\u0026thinsp;26 times. The scalability and adaptability of DUE are demonstrated through field experiments conducted in real salt lake environment with highly saline condition. Upon salt lake water naturally falling on a 4-step device equipped with DUE films, uranium is successfully extracted with the final products of MgU\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eU\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e22\u003c/sub\u003e. This zero-consumption technology can promote the development of scalable, economical, and environmentally sustainable uranium resource exploitation, and may offer considerable potential for other aqueous mineral extraction at the industrial level.\u003c/p\u003e "},{"header":"RESULTS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eDesign of DUE approach\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eSalt lake presents a promising and underexplored resource for sustainable uranium extraction, offering distinct topographical and hydrological features ideal for harnessing mechanical energy from descending brine water streams, driven by natural elevation gradients or artificial control. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, a multi-step DUE device can be designed and installed on the shore of salt lake like a water conservancy project, and the brine water can flow down the steps with DUE film equipped. The water is segmented into controlled streams and transformed into high-frequency droplets at each step, enabling continuous and scalable operation.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003eb shows the three-layer material configuration of DUE film, consisting of Al electrode as the upper layer, ICP-etched FEP membrane as the middle layer, and CTS@CF as the base. The Al electrode functions as a charge reservoir, resulting in charge separation upon droplet impacting, initiating the in-situ electrochemical processes [22]. The superhydrophobic FEP membrane induces solid-liquid interfacial interactions and facilitates rapid droplet detachment to minimize energy losses [23]. The CTS@CF acts as an active site for the electrochemical reaction of uranium extraction. CTS can selectively adsorb uranium ions (UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e) and reduces interference from competing ions such as magnesium (Mg\u003csup\u003e2+\u003c/sup\u003e) and sodium (Na\u003csup\u003e+\u003c/sup\u003e) [24,25]. The electrochemical reduction of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e can produce less soluble uranium species, thereby enabling efficient uranium extraction. Figure\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003ec illustrates the scalability of the film, emphasizing its flexibility and adaptability, which enable seamless deployment across diverse salt lake environments and terrains. Figure\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003ed illustrates the color change of CTS@CF before and after DUE, changing from black to bright yellow, visually confirming the successful deposition of uranium species. Furthermore, under UV irradiation, the distinct green fluorescence emitted by uranium species serves as a definitive verification of their presence after DUE [26].\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003ee shows the probable working principle of DUE process, which outlines three steps. In Step I, before impacting on DUE film, the electroneutral droplet naturally falls down. The superhydrophobic FEP membrane, acting as an electret material, retains negative charges to establish an electrostatic potential [27]. UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e and competing ions are distributed within the aqueous solution surrounding CTS@CF, and UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions are selectively adsorbed on CTS functional sites because CTS can preferably bind UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions through abundant -NH\u003csub\u003e2\u003c/sub\u003e and -OH groups in the structure [28]. In Step II, the droplet fully contacts with FEP membrane. Due to the negative electrostatic potential of FEP membrane, the positive and negative charges in the droplet are separated. The positive charges appear close to FEP and form electric double layers (EDLs), and the negative charges appear on the opposite side [29]. The droplet then spreads to contact with Al electrode and transfers negative charges to the DUE film. The UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions selectively adsorbed on CTS functional groups are reduced electrochemically to form less soluble uranium species, such as uranium peroxide hydrate precipitate, (UO\u003csub\u003e2\u003c/sub\u003e)O\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO. In Step III, the droplet detaches from the surface due to the superhydrophobic properties of FEP membrane. The departing droplet retains positive charges due to charge transfer during the step above, as confirmed in \u003cb\u003eFig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e. The quantity of positive charges carried by droplets is tested across different Weber numbers (We), defined as We\u0026thinsp;=\u0026thinsp;ρDv\u003csup\u003e2\u003c/sup\u003e/γ, where ρ, D, v and γ are respectively the density, diameter, impacting velocity and surface tension of the droplet. It shows an increased in transferred charge from ~\u0026thinsp;7 nC to ~\u0026thinsp;19 nC as the We number rises from ~\u0026thinsp;10 to ~\u0026thinsp;80, eventually stabilizing. Many research groups also observe such a phenomenon of departing droplet carrying positive charges [22,30\u0026ndash;32]. The process of droplet impacting and departing can be approximately equivalent to providing negative charges to DUE film, which leads to the in-situ electrochemical reduction of selectively adsorbed UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e1\u003c/span\u003ef shows the comparison of cost and efficiency between recent aqueous uranium extraction methods and our DUE approach. DUE offers very low cost and remarkable energy efficiency, and no external power supply is required. The utilization of natural mechanical energy from salt lake water flows substantially reduces operational costs while maintaining high extraction efficiency. Maximum extraction efficiency of 603.2 mg/Wh has been achieved, which surpasses conventional technologies [9\u0026ndash;14] and provides a scalable solution for industrial uranium extraction with minimal environmental influence (\u003cb\u003eSupplementary Note 1\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCharacterization of DUE film\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003e provides a detailed depiction of the material structure and electrical characteristics of DUE film. Figure\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows that the DUE film incorporates a modular three-layer structure, comprising Al electrode (green), superhydrophobic FEP membrane (purple), and CTS@CF (gray). The FEP membrane undergoes ICP etching, forming micro-nano structures that mimic the surface morphology of lotus leaves, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cb\u003eFig. S2\u003c/b\u003e. The 3D optical surface profile reveals a surface roughness of 0.91 for the FEP membrane, a key factor in its superhydrophobicity, as evidenced by a contact angle of 158\u0026deg; (Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). This engineered surface improves droplet detachment efficiency and stabilizes the Cassie-Baxter state, as demonstrated by confocal laser scanning microscopy in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, which visualizes the solid-liquid-gas triple-phase contact line [33].\u003c/p\u003e \u003cp\u003eThe Scanning Electron Microscopy (SEM) image of CTS@CF is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, and the fibers have average diameter of 8\u0026ndash;10 \u0026micro;m and exhibit three-dimensional porous structure. Energy Dispersive Spectroscopy (EDS) mapping in \u003cb\u003eFig. S3\u003c/b\u003e confirms that CTS is uniformly coated on the surface of CF. X-ray photoelectron spectroscopy (XPS) analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ef and \u003cb\u003eFig. S4\u003c/b\u003e show that the peaks around 398, 284, and 408 eV of CTS@CF can be attributed to -NH\u003csub\u003e2\u003c/sub\u003e, C-N/C-O/O-C\u0026thinsp;=\u0026thinsp;O, and C\u0026thinsp;=\u0026thinsp;N-O, respectively [10]. Fourier-transform infrared (FTIR) spectra in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003eg further support these findings, displaying prominent N-H and O-H stretching vibrations at 3406 cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup1; and 3157 cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup1;, along with C\u0026thinsp;=\u0026thinsp;O stretching bands at 1636 cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup1; and 1686 cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup1; [28]. These functional groups improve the hydrophilicity of CTS@CF, as evidenced by wettability tests in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003eh, enabling effective interaction with solutions. As shown in \u003cb\u003eFig. S5\u003c/b\u003e, the high zeta potential\u0026thinsp;~\u0026thinsp;63.4 mV of CTS@CF ensures the relative stability at 100 mg/L initial uranium concentrations [34].\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ei \u0026amp; \u003cb\u003ej\u003c/b\u003e show the electric output of DUE film (area:16 cm\u003csup\u003e2\u003c/sup\u003e, positioned at a 45\u0026deg; incline) under water droplets (10 \u0026micro;L per droplet, 100 mg/L UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO) released from a height of 20 cm and impacting at a frequency of 2.5 Hz. The outputting voltage (open circuit) consistently exceeds 200 V, and the outputting current (short circuit) maintains\u0026thinsp;\u0026gt;\u0026thinsp;1 mA. By optimizing the external load resistance to ~\u0026thinsp;10\u003csup\u003e4\u003c/sup\u003e Ω, the film achieves a power output of approximately 90 mW (Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ek), reflecting efficient energy utilization. Durability tests performed over 30 days (Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003el) validate the stability of the film, with outputting voltage keeping\u0026thinsp;\u0026gt;\u0026thinsp;200 V. The high and stable electric output can efficiently enable the reduction of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e adsorbed on CTS@CF for prolonged periods. We also conduct high-frequency droplet impacting experiments to investigate the adaptability of the film to torrent water condition. It is worth noting that the droplet flow at 100 Hz almost appears as a continuous water flow (Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003em), similar to salt lake water falling. Under 100 Hz droplet impacting, the output of the film maintains at a stable voltage of ~\u0026thinsp;200 V and a stable current of ~\u0026thinsp;0.6 mA (\u003cb\u003eFig. S6\u003c/b\u003e). In Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003en, frequency variation experiments further validate the film's robustness, with voltage output fluctuating around 200 V observed across a wide range of impacting frequencies from 100 Hz to 180 Hz. The output performance of DUE film is influenced by both droplet volume and release height, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003eo and \u003cb\u003eFig. S7\u003c/b\u003e. At 100 Hz, as the droplet volume increases from 1 \u0026micro;L to 10 \u0026micro;L, the voltage output gradually rises and stabilizes at approximately 200 V. As the release height increases from 5 cm to 20 cm, the voltage output steadily increases from 40 V to about 200 V, remaining stable beyond 20 cm. Additionally, FEP membrane with superhydrophobic surface yields the highest voltage (~\u0026thinsp;200V) output under high-frequency droplet impacting (Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e2\u003c/span\u003ep), outperforming hydrophilic surface (~\u0026thinsp;0.08 V) and hydrophobic surface (~\u0026thinsp;26 V). These results show that superhydrophobic surface engineering optimizes energy transfer through efficient droplet departing while ensuring the film's stability and efficiency under torrent water conditions, making it ideal for applications in salt lake environments [23].\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eIn-situ analysis of DUE process\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003ea shows the in-situ alpha (α) pulse detection system for analyzing the instantaneous uranium extraction quantity during DUE process, which leverages the radioactive decay properties of uranium isotopes (primarily U-238). The experiments here utilize 1000 mg/L UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO aqueous solution, with droplets (10 \u0026micro;L per droplet) released from a height of 20 cm onto the DUE film (area:16 cm\u003csup\u003e2\u003c/sup\u003e, positioned at a 45\u0026deg; incline). The analysis is conducted by using a detector placed parallel to the DUE film, which provides immediate feedback on uranium extraction quantity when α particles composed of two protons and two neutrons are emitted during uranium decay to the stable thorium-234 (Th-234) [35]. The detection system, incorporating a charge-sensitive preamplifier and shaping amplifier, converts α-particle-induced charge signals into voltage signals. The signals are subsequently processed via an analog-to-digital converter, generating quasi-gaussian pulse signals, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. By applying a well-defined threshold value, the system can precisely identify and count pulse voltage signals produced by individual α-particles, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003ec. This methodology ensures high-resolution and reliable detection of uranium extraction quantity on the DUE film.\u003c/p\u003e \u003cp\u003eMeasurements are conducted at different droplet counts (1, 5, 10, and 15 droplets) to evaluate the instantaneous uranium extraction quantity in situ, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003ed. Each pulse corresponds to a single α-particle emission, directly indicating uranium quantity. Red pulse counts represent uranium extracted on the DUE film, while yellow pulse counts represent the total uranium in the droplets. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003ee, by calculating the ratio of red pulse counts to yellow pulse counts, extraction efficiencies of 58%, 56%, 56%, and 55% are recorded upon 1, 5, 10, and 15 droplets, respectively. These results demonstrate very high efficiency of DUE process, and consistent performance across successive cycles emphasizes the reliability of repeated operations.\u003c/p\u003e \u003cp\u003eUranium extraction of DUE film is also confirmed through UV fluorescence imaging, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e3\u003c/span\u003ef. The CTS@CF exhibits distinct green fluorescence, with intensity increasing proportionally to the number of droplets. This optical evidence closely aligns with α-particle detection results, further validating the success of DUE. The consistent correlation between fluorescence intensity and α-particle counts underscores the robustness and reliability of the monitoring protocol. In contrast, \u003cb\u003eFig. S8\u003c/b\u003e shows that fluorescence almost cannot be observed on the sample without FEP membrane. For this control sample, only adsorption of uranium can take place on CTS@CF, and no electrochemical process can occur, leading to low uranium extraction efficiency.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eEx-situ analysis of DUE process\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the ex-situ analysis of DUE process, including the morphological evolution and physicochemical transformations of uranium species throughout successive droplet extraction cycles. Figure\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ea shows atomic contrast transmission electron microscopy (AC-TEM) images of CTS@CF surface at varying droplet counts, demonstrating morphological changes. After the first droplet impacting, atomic-scale bright spots, marked with red circles, can be observed on CTS@CF surface, indicating the initial capture and reduction of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e as atomically dispersed uranium species on adsorption sites. After the fifth droplet impacting, the dispersed species aggregated into small clusters. After the tenth droplet impacting, the clusters nucleated and crystallized into nanocrystals. After the fifteenth droplet impacting, the nanocrystals subsequently coalesced into nanosheets with an approximate thickness of ~\u0026thinsp;7 nm. This morphological change comprises the following sequential stages: (1) adsorption and reduction; (2) aggregation into clusters; (3) nucleation and crystallization; and (4) growth into nanosheets.\u003c/p\u003e \u003cp\u003eTo demonstrate the chemical changes occurring on CTS@CF surface after one single droplet falls onto the DUE film, we employ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to investigate the valence states and coordination environments of uranium species [11,13,36]. Figure\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003eb shows that the U L-edge XANES spectrum exhibits a white-line peak at 17175.7 eV, indicative of electron transitions from U 2p to unoccupied U 6d states. The absorption edge of uranium deposited on DUE film is located between the absorption edges of UO\u003csub\u003e2\u003c/sub\u003e and UO\u003csub\u003e2\u003c/sub\u003e (NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, indicating that the valence states of uranium cations are between +\u0026thinsp;4 and +\u0026thinsp;6. Fourier-transformed (FT) k\u0026sup2;-weighted EXAFS spectra in R-space and k-space with experimental data and fitted curve (Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ec \u0026amp; \u003cb\u003ed\u003c/b\u003e, \u003cb\u003eSupplementary Table\u0026nbsp;1\u003c/b\u003e) reveal the local chemical environment of uranium on CTS@CF surface. The oscillation frequency of EXAFS in R-space also differs from UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, indicating changes in the oxidation state of uranium and rearrangement of local atomic structures during the electrochemical reaction process. The EXAFS in k-space fitting results show two major peaks at 1.4 \u0026Aring; and 1.8 \u0026Aring;, corresponding to axial oxygen (U-Oax) and equatorial oxygen (U-Oeq), respectively. The coordination number analysis results show that U-Oax has a coordination number of 2.9, and U-Oeq has a coordination number of 3.6. These findings confirm the formation of a stable 3Oax-1U-4Oeq structure on CTS@CF surface. Wavelet transform (WT) analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ee and \u003cb\u003eFig. S9\u003c/b\u003e further supports the reduction of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e by exhibiting intensity shifts by 6 \u0026Aring;⁻\u0026sup1;, which are consistent with changes in the coordination environments of uranium during DUE process.\u003c/p\u003e \u003cp\u003eMolecular dynamics (MD) simulations are conducted to provide detailed insights into the physicochemical interactions involved during DUE process (\u003cb\u003eFig. S10\u003c/b\u003e). The mechanistic process of DUE is schematically illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ef. The DUE film carries negative charges from droplet-electricity effect and generates a strong electrostatic field, driving the positively charged UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions migrating toward the film. The UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions undergo selective adsorption at the functional sites of CTS and are then reduced through in-situ electrochemical reactions. This effect of electrostatic attraction combined with selective adsorption significantly enhances the reduction efficiency of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003eg shows the potential of mean force (PMF) analysis for the simulated mechanistic process of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ion migration under an electrostatic field [37]. The results show that after applying the electrostatic field, the surface potential energy of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions decreases from \u0026minus;\u0026thinsp;0.38 kJ/mol to -0.51 kJ/mol, indicating a stronger inclination of ions to adsorb onto CTS@CF. The probability density distribution analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003eh also reveals that the surface UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ion density increases from approximately 2.5 to 3.5. This further confirms that the electrostatic field at CTS@CF surface more effectively stabilizes UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions. The mean square displacement (MSD) analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ei) indicates that the migration rate of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e significantly decreases after the electrostatic field is applied, with an MSD value of 2000 within 10 ns, compared to 4000 before the field is applied [38]. This observation suggests the formation of a unique stable adsorption layer on the functionalized surface. Radial distribution function (G(r)) analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig23\" class=\"InternalRef\"\u003e4\u003c/span\u003ej) shows a pronounced peak for U-N coordination at ~\u0026thinsp;4.2 \u0026Aring; (intensity\u0026thinsp;~\u0026thinsp;2.2), indicating strong interactions between UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e and CTS, primarily within a short range (\u0026lt;\u0026thinsp;5 \u0026Aring;). In contrast, U-C coordination exhibits a lower peak (intensity\u0026thinsp;~\u0026thinsp;1.0) with a broader distribution (6\u0026ndash;10 \u0026Aring;), reflecting weaker interactions and lower stability [39]. These findings suggest that the electrostatic field preferentially promotes U-N coordination over U-C interactions, thereby strengthening the binding of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e to CTS and enhancing adsorption.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eUranium species extracted\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eA 12-stage experimental equipment is constructed to extract uranium species during DUE process under dynamic flow conditions without external power supply, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ea. The multi-stage design fully enables energy conversion across stages and allows adequate uranium extraction as the water flows through many stages. This experimental setup is also a rehearsal for the field tests in real salt lake environments. The experiment processes a total of 3 L of UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO aqueous solution at varying concentrations, with 100 Hz droplets (10 \u0026micro;L per droplet) impacting. Each stage is equipped with DUE film (16 cm\u003csup\u003e2\u003c/sup\u003e), and the height between each stage is approximately 20 cm. Each stage ensures smooth water flow, facilitates high-frequency droplet generation, and extends UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e interaction time with the DUE film [40].\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003eb shows that at an initial concentration of 100 mg/L, DUE approach achieves a significantly higher uranium extraction capacity (~\u0026thinsp;162.3 mg/g within 2 hours and ~\u0026thinsp;396.4 mg/g within 12 hours) compared to adsorption method (no FEP membrane), which plateaus at ~\u0026thinsp;38.9 mg/g. The uranium extraction quantity is calculated by measuring the concentration of the solution before and after DUE. The uranium extraction efficiency of DUE and adsorption methods with 12 hours is about 84.2% and 8.3%, respectively. At other initial uranium concentrations (5, 50 and 1000 mg/L), superior efficiency of DUE approach compared to conventional adsorption method can also be observed, as shown in \u003cb\u003eFig. S11\u003c/b\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, at an initial concentration of 1000 mg/L, DUE approach achieves an extraction capacity of ~\u0026thinsp;1250.6 mg/g after 12 hours, while the adsorption method exhibits saturation at a capacity of ~\u0026thinsp;47.3 mg/g. The extraction capacity of DUE approach surpasses conventional adsorption method by ~\u0026thinsp;26 times, underscoring its great application potentials.\u003c/p\u003e \u003cp\u003eUranium extraction quantity during DUE process (1000 mg/L) can also be evaluated by using electrochemical impedance spectroscopy (EIS), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. The polarization resistance (Rp) of CTS@CF obtained through fitting decreased over time, from 375.1 Ω to 88.29 Ω, reflecting the progressive formation of conductive uranium species on CTS@CF surface (\u003cb\u003eFig. S12\u003c/b\u003e). This conductive layer enhances electron transfer efficiency and may facilitate sustained extraction performance [10,41]. Visual evidence further corroborates these findings, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ee. Under UV irradiation, after 6 hours of extraction at an initial uranium concentration of 1000 mg/L, the CTS@CF surface exhibits green fluorescence during DUE in the experimental environment. Simultaneously, the visual changes in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ef show that the CTS@CF surface changes from black to yellow, while the yellow color of the aqueous solution completely fades, further validating the uranium extraction process. Figure\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003eg shows that the pH value does not have a great influence on the extraction efficiency of DUE approach. The uranium extraction efficiency keeps above 80% with pH values ranging from 3 to 9.\u003c/p\u003e \u003cp\u003eThe selectivity is essential for DUE approach to extract uranium and suppress interference from co-existing ions due to the high levels of competing ions in real salt lake water. Figure\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003eh shows the high selectivity of DUE approach towards UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e. We test the extraction efficiency of U, V, Fe, Pb, Ca, Mg, and Cr from corresponding aqueous solution (UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, NH\u003csub\u003e4\u003c/sub\u003eVO\u003csub\u003e3\u003c/sub\u003e, FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, Pb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, CaCl\u003csub\u003e2\u003c/sub\u003e, MgCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, and CrCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO) with the same concentration of 100 mg/L. The extraction efficiency of U is higher than 80%, and the extraction efficiencies of other ions such as V, Fe, Pb, Ca, Mg, and Cr are merely 25.8%, 24.9%, 20.5%, 16.0%, 5.3%, and 2.2%, respectively. The high selectivity arises from the selective adsorption of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e on CTS, which is further analyzed using electrostatic surface potential (ESP) simulations (\u003cb\u003eFig. S13\u003c/b\u003e \u0026amp; \u003cb\u003eS14\u003c/b\u003e). For comparison, V\u003csup\u003e5+\u003c/sup\u003e ion is selected as an example, which is widely recognized as a competitive ion for uranium adsorption and typically exists as HVO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e in solution [5]. The CTS exhibits significant negative potential in adsorption site-related regions, with an ESP range of -18.83 to 18.83 kcal/mol. At the adsorption sites, the negatively charged region (blue area) on the CTS strongly attracts the positively charged UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e, which features a highly localized positive potential with an ESP value of up to +\u0026thinsp;409.33 kcal/mol. This pronounced difference in ESP creates a favorable electrostatic environment for binding. In contrast, HVO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e has an ESP range of -249.35 to -124.74 kcal/mol, characterized by a strongly negative potential. The negatively charged regions on CTS surface (blue areas) generate electrostatic repulsion toward HVO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, preventing stable binding. These findings provide a molecular-level explanation of the mechanism by which DUE films achieve efficient and selective extraction of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e from complex aqueous matrices. Furthermore, as shown in \u003cb\u003eFig. S15\u003c/b\u003e \u0026amp; \u003cb\u003e16\u003c/b\u003e, CTS@CF not only enhances the material\u0026rsquo;s hydrophilicity but also maintains the cleanliness of adsorption sites in natural water environments due to its inherent antibacterial properties, which prevent microbial biofouling and blockage of adsorption sites. Antibacterial tests show inhibition of \u003cem\u003eE.coli\u003c/em\u003e and \u003cem\u003eS.aureus\u003c/em\u003e, ensuring long-term activity and stability of the adsorption sites [42].\u003c/p\u003e \u003cp\u003eDetailed structural and compositional analyses are conducted to elucidate the extracted uranium species. SEM images in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ei reveal obvious flake-like uranium deposits on the CTS@CF surface after 6 hours of DUE process at an initial 100 mg/L concentration. For the adsorption method (no FEP membrane), the surface of CTS@CF remains nearly smooth with minimal precipitate formation, as shown in \u003cb\u003eFig. S17\u003c/b\u003e. These observations suggest a phase transformation pathway in which UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e is reduced and crystallized on CTS@CF during DUE process. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ej demonstrates a uniform distribution of uranium across the CTS@CF surface after DUE, with signal intensities markedly higher than those for carbon (C) and nitrogen (N). Additionally, EDS mapping in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ek confirms the formation of substantial uranium deposits on the CTS@CF surface and within the interstitial spaces after DUE. FTIR spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003el) further support these findings, showing the disappearance of the enhanced C\u0026thinsp;=\u0026thinsp;O stretching vibration peak at 1686 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and the emergence of a U-O peak at 894 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicative of UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e adsorption and reduction during DUE [43]. The retention of O-H and N-H stretching peaks between 3406 cm⁻\u0026sup1; and 3157 cm⁻\u0026sup1; underscores the critical role of CTS functional groups in coordinating and binding UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e during DUE.\u003c/p\u003e \u003cp\u003eWe then analyze the uranium deposits simply peeled off from the CTS@CF surface after DUE. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003em provides further insights, revealing lattice spacing of 0.32 nm in the uranium deposits, corresponding to the (200) crystal plane of uranium peroxide hydrate, (UO\u003csub\u003e2\u003c/sub\u003e)O\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO, and confirming the crystalline nature of the extracted uranium. Consistent with these results, EDS image (Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003en) shows the uniform distribution of uranium and oxygen on the surface of uranium deposits. The valence state of uranium precipitates after DUE is studied through XPS U4f analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003eo, \u003cb\u003eFig. S18).\u003c/b\u003e The spectrum reveals two primary peaks approximately 11.0 eV apart, along with a smaller peak on the higher binding energy side. The two main peaks at ~\u0026thinsp;381.0 eV and ~\u0026thinsp;392.0 eV are assigned to U4f\u003csub\u003e7/2\u003c/sub\u003e and U4f\u003csub\u003e5/2\u003c/sub\u003e primary peaks, respectively, while the smaller peak at ~\u0026thinsp;398.6 eV corresponds to the satellite peak of U4f\u003csub\u003e5/2\u003c/sub\u003e. The 6.8 eV separation between the satellite peak and the U4f\u003csub\u003e5/2\u003c/sub\u003e primary peak indicates the presence of U(IV) in the uranium extracted after DUE [44]. Fitting results further confirm the dominance of U(IV) content, in sharp contrast to uranium species extracted by adsorption, which are primarily composed of U(VI). Through X-ray diffraction (XRD) analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig24\" class=\"InternalRef\"\u003e5\u003c/span\u003ep, it confirms (UO\u003csub\u003e2\u003c/sub\u003e)O\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO as the dominant crystalline phase and also identifies it as the metastudtite. This result is consistent with previous studies where similar species were primarily identified using electrochemical methods [9,10]. Finally, α-particle decay spectra measurements of our samples compared to pure samples (U238, Pu239, Pu238) demonstrate that their radioactivity closely resembles that of U238, further validating the radioactive properties of the post-extraction samples (\u003cb\u003eFig. S19\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eField experiments in real salt lake environment\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe effectiveness of DUE approach for industrial-scale uranium extraction is demonstrated through field experiments in real salt lake environment with highly saline water condition, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003ea. The brine water, representative of the complex ionic composition of saline environments, contains uranium (~\u0026thinsp;173 \u0026micro;g/L) alongside competing ions, including Mg\u003csup\u003e2+\u003c/sup\u003e (~\u0026thinsp;58.9 g/L), Na\u003csup\u003e+\u003c/sup\u003e (~\u0026thinsp;58.2 g/L), K\u003csup\u003e+\u003c/sup\u003e (~\u0026thinsp;8.5 g/L), and Ca\u003csup\u003e2+\u003c/sup\u003e (~\u0026thinsp;2.2 g/L). A 4-step cascading device is positioned beneath the brine water pipeline to enable efficient uranium extraction. By harnessing falling water kinetic energy, the DUE device processes large volumes of brine water continuously across multiple steps, surpassing the limitations of laboratory-scale setups. Figure\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003eb shows the detailed structure of the 4-step cascading device, and the height between each stage is ~\u0026thinsp;20 cm, equipped with DUE films on each step (area:100 cm\u003csup\u003e2\u003c/sup\u003e).\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003ec, during operation, uranium extraction becomes visually apparent as the color of CTS@CF surface changing from black to some yellow spots after 20 hours, and almost all of the surface turns yellow after 40 hours. The distinct green fluorescence observed under UV light confirms uranium extraction. After extraction, the uranium deposits are peeled off from the CTS@CF, dissolved in water, and filtered to yield a concentrated uranium product, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003ed. The process is not only environmentally friendly but also operationally simple, requiring no organic solvents and utilizing easily scalable techniques. The final products, observed as fine yellow powders collected on filter paper, exhibit large agglomerated uranium-containing particles, as revealed by SEM imaging (Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003ee). EDS mapping and spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003ef \u0026amp; \u003cb\u003eg\u003c/b\u003e confirm that U is the dominant element in the final products, with the presence of O, Mg and Na elements. XRD analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig25\" class=\"InternalRef\"\u003e6\u003c/span\u003eh identifies MgU\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eU\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e22\u003c/sub\u003e as the predominant crystalline phases. These findings are consistent with previous reports, indicating that UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e may firstly be reduced to low-valence uranium species and then react with dissolved oxygen and metal ions under alkaline conditions to form urinates [45]. As the concentrations of Na\u003csup\u003e+\u003c/sup\u003e and Mg\u003csup\u003e2+\u003c/sup\u003e in salt lake environments are high, these ions likely influence uranium reduction processes, forming valuable intermediates for nuclear fuel production.\u003c/p\u003e \u003cp\u003eThe modular cascading DUE device allows for site-specific adjustments in dimensions and stage heights, ensuring consistent efficiency across various salt lake environments. The device can also seamlessly integrate into existing industrial workflows, such as lithium extraction and potassium fertilizer production, by using shared saltwater pipelines and infrastructure [46,47]. This integration reduces operational costs and enhances resource utilization, providing a scalable and economically viable solution for uranium extraction. The potential production of uranium from several major salt lakes around the world using the DUE method will be remarkable. Assuming a uranium concentration of ~\u0026thinsp;150 \u0026micro;g/L in these salt lakes, and a DUE extraction efficiency of ~\u0026thinsp;80%, Qarhan Salt Lake (biggest in Asia, ~ 500\u0026nbsp;million m\u0026sup3;) could produce 60 tU, Great Salt Lake (biggest in North America, ~ 16\u0026nbsp;billion m\u0026sup3;) 1,920 tU, Chott el Djerid Lake (biggest in Africa, ~ 7\u0026nbsp;billion m\u0026sup3;) 840 tU, Salar de Uyuni (biggest in South America, ~ 5\u0026nbsp;billion m\u0026sup3;) 600 tU, and Caspian Sea (biggest in Europe, ~ 78.2 trillion m\u0026sup3;) 9.38\u0026nbsp;million tU. The huge total amount could meet the human demand for clean energy fuel, thereby partially replacing the terrestrial uranium reserves (~\u0026thinsp;7.6\u0026nbsp;million tU globally), demonstrating the great potential of DUE method as a sustainable solution for uranium extraction. Additionally, by simply modifying selective adsorption sites for other metal ions on CF (replacing CTS), this zero-consumption technique can conveniently extend to other aqueous mineral extraction, such as rare earth and noble metal elements.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn summary, an innovative DUE approach is presented as a sustainable solution for spontaneously extracting uranium from mineral-rich salt lake. By leveraging the kinetic energy of descending water droplets, it drives a selective electrochemical process that reduces UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions while minimizing impurity co-deposition. No external power supply is needed for the DUE process. The three-layer Al-FEP-CTS@CF material has both high efficiency and durability. The extraction efficiency is up to 58% for the first droplet, and keeps higher than 55% for subsequent droplets. MD simulations and advanced characterization techniques, including AC-TEM and XAFS, confirm crystallization of (UO\u003csub\u003e2\u003c/sub\u003e)O\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO after DUE. With an extraction capacity of 1250.6 mg/g, surpassing conventional adsorption method by ~\u0026thinsp;26 times, the DUE method exhibits great application potentials. The field experiments in real salt lake environment demonstrate its scalability and adaptability at the industrial level, and the final products spontaneously extracted from brine water flows are MgU\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eU\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e22\u003c/sub\u003e. This zero-consumption, scalable, economical, and environmentally sustainable technique can promote the development of aqueous mineral exploitation, not only for uranium but also for other metal resources.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eFabrication of DUE film\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe film comprised three components. The top layer was Al electrode with a width of 2 \u0026micro;m and length customizable according to experimental needs, and fixed onto the FEP membrane. Al electrode served as a charge reservoir and initiated the in-situ electrochemical processes. The middle layer was a piece of FEP membrane (Aladdin Shanghai Chemical Co., Ltd.) treated by ICP etching. The membrane was etched for 15 minutes using a mixed gas of argon, sulfur hexafluoride, and oxygen (volume ratio: 1:6:1) (Chengdu Runtai Specialty Gas Co., Ltd.), forming superhydrophobic surface. The bottom layer was CF coated with CTS (Condary Environmental New Materials Co., Ltd.). CF was first soaked in a 1% chitosan acetic acid solution, then neutralized in a 10% sodium hydroxide solution (Shanghai Macklin Biochemical Co., Ltd.), and finally dried at 40\u0026deg;C for 30 minutes to enhance stability. These three layers were precisely aligned and fixed during assembly to ensure the film's overall performance and stability. For fabricating a DUE film with an area of 16 cm\u003csup\u003e2\u003c/sup\u003e, the dimension of Al electrode was 10\u0026times;0.0002\u0026times;0.1 cm, 4\u0026times;2\u0026times;0.03 cm for FEP membrane, 4\u0026times;4\u0026times;0.1 cm for CTS@CF (the specific dimensions were described in terms of length, width, and height). For fabricating a DUE film with an area of 100 cm\u0026sup2;, the dimension of Al electrode was 25\u0026times;0.0002\u0026times;0.1 cm, 10\u0026times;5\u0026times;0.03 cm for FEP membrane, and 10\u0026times;10\u0026times;0.1 cm for CTS@CF.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eCharacterizations and measurements\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eSurface morphologies and microstructures were observed by using a Zeiss GeminiSEM 300, operating at 5 kV for high-resolution mapping and 15 kV for EDX elemental analysis. A Sensofar NEOX 90 optical profilometer was utilized for measuring the 3D optical surface profiles and assessing superhydrophobicity, while a Nikon A1 laser confocal microscope, equipped with a 532 nm laser, was employed to visualize interactions between uranium-containing water (100 mg/L) and FEP surface. To monitor changes in the contact angle and characterize surface wettability, an OCA-50AF goniometer was utilized. Surface functional groups and bonding states were analyzed using XPS (Thermo Fisher Scientific K-Alpha) and FTIR (Thermo Scientific Nicolet Summit), while the zeta potential of CTS@CF was measured using a Brookhaven zeta potential analyzer. The electric output of DUE film recorded with a Keithley 6517B electrometer, and the amount of positive charge carried by droplets was measured using a Faraday cup (Monroe model 284).\u003c/p\u003e \u003cp\u003eFor real-time assessments of alpha particle emissions and uranium extraction quantity, an in-situ alpha (α) pulse detection system equipped with CoMPASS software was employed. The surface fluorescence was observed by using a UV flashlight irradiation (wavelength: 365 nm). Microstructural lattice details were explored using AC-TEM (FEI Titan 80\u0026ndash;300). Synchrotron radiation experiments conducted at SSRF (BL14W1, Shanghai, China.) collected U L3-edge XAS spectra, which were analyzed with Athena and Artemis software. Electrochemical impedance spectroscopy (EIS) was conducted using a CHI660E workstation over a frequency range of 0.01 to 10⁵ Hz. TOF-SIMS (PHI NanoTOFII) was used for high-resolution analysis of surface element distribution. HAADF-STEM and STEM-EDS (JEOL JEM-ARM300F) provided micro morphology and elemental mapping of CTS@CF. The crystal structure of the extracted uranium was analyzed using XRD (Rigaku SmartLab SE).\u003c/p\u003e \u003cp\u003eTo measure uranium extraction efficiency, a 1000 mg/L UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO aqueous solution (~\u0026thinsp;3 L, DUE film area: 16 cm\u003csup\u003e2\u003c/sup\u003e, stage height: ~ 20 cm) was utilized. The uranium extraction quantity was calculated by analyzing the solution concentration before and after DUE by using Arsenazo III and ICP-OES/ICP-MS. To demonstrate the high selectivity of DUE film, the extraction efficiencies of U, V, Fe, Pb, Ca, Mg, and Cr from corresponding aqueous solution (UO\u003csub\u003e2\u003c/sub\u003e(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, NH\u003csub\u003e4\u003c/sub\u003eVO\u003csub\u003e3\u003c/sub\u003e, FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, Pb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, CaCl\u003csub\u003e2\u003c/sub\u003e, MgCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, and CrCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO) with the same concentration of 100 mg/L were tested (reagents sourced from Shanghai Macklin Biochemical Co., Ltd.). Adsorption experiments were performed by immersing CTS@CF (without FEP membrane) in the solution under conditions similar to DUE. The effects of initial uranium concentration (5-1000 mg/L) and solution pH (range: 3\u0026ndash;9, uranium concentration: 100 mg/L) on extraction performance were systematically investigated.\u003c/p\u003e \u003cp\u003eField-scale experiments demonstrated the industrial feasibility of the DUE method in high-salinity brine water from Qarhan Salt Lake, Qinghai Province, China. The brine water contained uranium (~\u0026thinsp;173 \u0026micro;g/L) and competing ions, including Mg\u003csup\u003e2+\u003c/sup\u003e (~\u0026thinsp;58.9 g/L), Na\u003csup\u003e+\u003c/sup\u003e (~\u0026thinsp;58.2 g/L), K\u003csup\u003e+\u003c/sup\u003e (~\u0026thinsp;8.5 g/L), and Ca\u003csup\u003e2+\u003c/sup\u003e (~\u0026thinsp;2.2 g/L). A 4-step cascading device, positioned beneath the brine water pipeline, was utilized to process large volumes of brine continuously using the kinetic energy of falling water. Each step incorporated a 100 cm\u0026sup2; DUE film with a height difference of ~\u0026thinsp;20 cm. All salt lake water had not undergone any prior treatment.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eMD simulations\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eAll MD simulations were conducted using the LAMMPS package, with trajectory visualization and analysis performed via VMD software. The systems consisted of CF, UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e, H\u003csub\u003e2\u003c/sub\u003eO, and CTS. The OPLS-AA force field was employed for CTS and the electrode. Force field parameters for UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e were derived from previous simulation studies [48]. For water molecules, when the electric field was applied, hydrogen atomic positions were constrained using the SHAKE and RATTLE algorithms. Non-bonded van der Waals interactions were modeled with the 12\u0026thinsp;\u0026minus;\u0026thinsp;6 Lennard-Jones potential, while electrostatic interactions, including long-range Coulombic forces, were handled via the particle-particle-particle mesh method.\u003c/p\u003e \u003cp\u003eThe simulation boxes measured 7.38 nm \u0026times; 4.26 nm \u0026times; 3.50 nm. They contained CF, 60 UO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e ions, 3200 H\u003csub\u003e2\u003c/sub\u003eO molecules, and CTS molecules. For the production runs, a time step of 1 fs was adopted, and data were recorded every 1 ps. The systems were minimized by optimizing atomic positions and cell dimensions while maintaining isotropic box lengths. Two independent trajectories of 1000 ps were generated for each system. Equilibration was performed in the microcanonical ensemble at 298 K and 1 bar pressure for 10 ps, followed by a microcanonical ensemble simulation at 298 K for 1000 ps to obtain system parameters. Periodic boundary conditions were applied in all directions.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eESP simulations\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eAll computations were performed using the Gaussian 16 software package. The TPSSh functional, coupled with the D3BJ dispersion correction, was employed for the calculations [49]. Geometry optimizations and frequency analyses utilized the SDD basis set for uranium atoms and the def-TZVP basis set for other elements. To incorporate solvation effects, the polarizable continuum model (PCM) was applied. Wave function analyses were conducted using the Multiwfn 3.8(dev) program. The extrema of the electrostatic potential (ESP) on the van der Waals surface were determined through quantitative analysis of the electrostatic potential map. Isosurface representations were generated using the VMD visualization tool, based on output files from Multiwfn.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was supported by National Natural Science Foundation of China (11674048 and 52371144), China Academy of Engineering Physics Foundation (YZJJZQ2023019), Sichuan Science and Technology Program (2024NSFSC0143 and 2024YFFK0333), Radiation Oncology Key Laboratory of Sichuan Province (2023ROKF03 and 2024ROKF06) and Natural Science Foundation of Sichuan Province (25QNJJ2559).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConceptualization: X.J., L.L., Y.H., X.Z., and X.X.\u003c/p\u003e\n\u003cp\u003eMethodology: X.J., L.L., L.X., and X.X.\u003c/p\u003e\n\u003cp\u003eInvestigation: X.J., L.L,\u0026nbsp;J.D.,\u0026nbsp;F.W., and Z.L.\u003c/p\u003e\n\u003cp\u003eVisualization: X.J., L.L., and X.X.\u003c/p\u003e\n\u003cp\u003eFunding acquisition: L.X., Y.H., X.Z., and X.X.\u003c/p\u003e\n\u003cp\u003eProject administration: X.J., L.L., F.W., Y.H., X.Z., and X.X.\u003c/p\u003e\n\u003cp\u003eSupervision: X.Z, and X.X.\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; original draft: X.J., and X.X.\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; review \u0026amp; editing: X.J., L.L., L.X., X.Z., and X.X.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData and materials availability:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data needed to evaluate the conclusions in this paper are present in the paper or the Supplementary Materials. 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N., Scuseria, G. E. Climbing the density functional ladder: Nonempirical meta-generalized gradient approximation designed for molecules and solids. \u003cem\u003ePhys. Rev. 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In this study, we introduce an innovative droplet uranium extraction (DUE) approach, in which naturally falling salt lake water interacts with a three-layer Al-FEP-CTS@CF film, driving an in-situ electrochemical process for spontaneous uranium extraction without external power consumption. The superhydrophobic fluorinated ethylene propylene (FEP) layer induces solid-liquid interfacial interactions, converting falling water kinetic energy into electricity. At the same time, the selective reduction of uranium ions takes place at chitosan (CTS) functionalized adsorption sites on carbon felt (CF), precipitating out uranium peroxide hydrate. The DUE method achieves a high uranium extraction efficiency of 58% for the first droplet of 1000 mg/L uranium aqueous solution and maintains efficiency above 55% for subsequent droplets. The DUE method has an extraction capacity of 1250.6 mg/g, surpassing conventional adsorption methods by ~ 26 times. Field experiments in real salt lake environment with high-salinity condition validate the scalability and adaptability of DUE, successfully extracting final products of MgU\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eU\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e22\u003c/sub\u003e from brine water flows. This zero-consumption technology provides a scalable, economical, and environmentally sustainable way for uranium resource exploitation, and can conveniently extend to other aqueous mineral extraction.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOne-Sentence Summary\u003c/strong\u003e: We introduce a zero-consumption and scalable Droplet Uranium Extraction (DUE) method that uses naturally falling salt lake water to drive in-situ electrochemical process for spontaneous uranium extraction, successfully validated in high-salinity salt lake environments with the final products of MgU\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eU\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e22\u003c/sub\u003e from brine flows.\u003c/p\u003e","manuscriptTitle":"Spontaneous Droplet Uranium Extraction from Salt Lake Water Natural Falling","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-12 11:11:40","doi":"10.21203/rs.3.rs-5849443/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-sustainability","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"natsustain","sideBox":"Learn more about [Nature Sustainability](http://www.nature.com/natsustain/)","snPcode":"","submissionUrl":"","title":"Nature Sustainability","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"0c2dfbcb-5cab-448b-bd16-21f3e242dfae","owner":[],"postedDate":"February 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":44150855,"name":"Physical sciences/Energy science and technology/Energy harvesting/Devices for energy harvesting"},{"id":44150856,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Electrochemistry"}],"tags":[],"updatedAt":"2026-03-06T08:06:40+00:00","versionOfRecord":{"articleIdentity":"rs-5849443","link":"https://doi.org/10.1038/s41893-026-01781-3","journal":{"identity":"nature-sustainability","isVorOnly":false,"title":"Nature Sustainability"},"publishedOn":"2026-03-05 05:00:00","publishedOnDateReadable":"March 5th, 2026"},"versionCreatedAt":"2025-02-12 11:11:40","video":"","vorDoi":"10.1038/s41893-026-01781-3","vorDoiUrl":"https://doi.org/10.1038/s41893-026-01781-3","workflowStages":[]},"version":"v1","identity":"rs-5849443","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5849443","identity":"rs-5849443","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}