Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors

Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors | 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 Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors Ran Niu, Linhui Fu, Kai Feng, Xinle Zhang, Ling Chen, Jiang Gong, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4489134/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract As the fundamental resource in nuclear energy, uranium is a sword of two sides, due to its radioactive character that could cause severe impact to the environment and living creatures once released by accident. However, limited by the passive ion transport, the currently available uranium adsorbents still suffer from low adsorption rate and capacity. Here, we report a self-driven modular micro-reactor composed of magnetizable ion-exchange resin and adsorbents that can be used to dynamically remove uranium from nonmarine waters. Because of the long-range pH gradient and phoretic flow established by the recyclable ion-exchange resin, the micro-reactor shows a fast uranium adsorption rate and reaches a uranium extraction capacity of 629.3 mg g − 1 within 20 min in 30 ppm uranium solution, as well as good recyclability in repeated use. Numerical simulation result confirms that the phoretic flow and electric field accelerate uranium transport to the adsorbent. Our work provides a new solution for the removal of radioactive uranium with high efficiency and low-effectiveness. Earth and environmental sciences/Environmental sciences/Environmental chemistry/Pollution remediation Physical sciences/Materials science/Soft materials/Colloids Micro/nanomotors Uranium adsorption Diffusion Ion-exchange Phoretic flow Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Uranium is the essential resource of nuclear energy, which is one of the most widely explored greenhouse-gas-free energy 1 , 2 , 3 . However, the radioactive contamination that results from the energy production route causes severe environmental challenges due to its accumulation and harmful effects to living creatures 4 , 5 . Therefore, it is of vital importance to extract uranium from polluted waters in a facile way. Among the various ways to extract uranium, such as electrochemistry 6 , 7 , chemical/biochemical reductive precipitation 8 , 9 , ion exchange 10 , 11 and filtration 12 , adsorption is one of the most commonly used approaches due to its easy operation, low cost and effectiveness 13 , 14 . The key for fast and effective uranium extraction is the design of adsorbents. A variety of adsorbents, including polymeric fibers, polymeric hydrogels, and porous materials have been designed 15 , 16 , 17 , 18 . However, traditional adsorbents rely on the passive diffusion of uranyl ions for adsorption, which is normally low and limits the adsorption kinetics. In addition, most of the adsorbents work in acidic or alkaline condition for best coordination with uranyl ions, which requires the pre-treatment of solution with chemicals and may cause secondary pollution. Therefore, advanced uranium adsorbents with active ion transport and local pH regulation are highly required for fast uranium removal. Micro/nanomotors (MNMs), capable of converting energy from surrounding environments into self-propelled motion, have shown great potential in environmental remediation 19 , 20 , 21 , 22 , 23 , 24 . The active motion of the MNMs promotes the mixing of pollutants and agents, which therefore accelerates the treatment efficiency 25 , 26 , 27 . The development of MNMs has enabled various micromachines that can be actuated by bubble, light or magnetic fields for uranium removal 28 , 29 , 30 , 31 , 32 , 33 . For example, metal-organic frameworks (MOFs)-based micromotor with implementation of Fe 3 O 4 and catalytic platinum nanoparticles shows bubble propelled motion in the presence of H 2 O 2 , as well as motion-enhanced uranium uptake (384 mg g − 1 ) 29 . Pan et al. designed near-infrared light (NIR)-driven nanorobot with amidoxime as adsorption site for uranium capture. The extraction amount of the self-driven nanorobot was increased by about 16.7% during the first 5 min. Both NIR-driven motion and NIR-induced temperature increase contribute to the fast uranium extraction 28 . In our previous work, MOFs-based hydrogel micromotor of magnetic actuation was used for uranium detection and adsorption. The magnetic-actuated motion enhances the contact between uranium and the adsorption site, which therefore accelerates the uranium detection and removal efficiency 34 . However, the short treatment range of MNMs, from electrostatic attraction or short-ranged phoretic flow limits their removal efficiency with adsorption equilibrium reached in more than 1 h. Meanwhile the unavoidable global pH regulation causes secondary pollution as well as increased cost. Therefore, intelligent MNMs with self-locomotion, self-pH regulation and long-range flow are urgently required to solve above problems. In this work, an ion-exchange-based modular microreactor with long-range flow and self-pH regulation is constructed for fast uranium removal. Generally, the ion-exchange unit provides long-range phoretic flow for enhanced uranium diffusion towards the adsorbent, and local pH regulation to enhance the interaction between adsorbent and the uranyl ion. The implemented Fe 3 O 4 nanoparticles on the surface of the ion-exchange resin further enables the magnetic and NIR actuation of the microreactor to adapt to different application environments. Numerical simulation result confirms the enhanced uranium diffusion towards the adsorbent by the flow and local electric field. As a result, uranium adsorption equilibrium is quickly reached within 10 min, as well as a high uranium uptake amount of 629.3 mg g − 1 in 30 ppm uranium solution. Results Construction of magnetic ion-exchange-based modular micromotors. The magnetic ion-exchange-based modular micromotors (mIEX-MMM) for uranium adsorption consists of two fundamental parts, magnetic ion exchange-based micro-fluidic pumps for assembly, motion control and local pH regulation of the adsorbent, and the adsorbents for uranium adsorption (Fig. 1 a). Typically, the mIEX as the central part of the micro-reactor can generate long-ranged pH gradient and electro-osmotic (eo) flow via ion-exchange reaction for the assembly of adsorbents. The eo-flow also accelerates the diffusion of uranium to the adsorbent and increases the uranium concentration around the adsorbent. Meanwhile, the mIEX tunes the local pH environment of the assembled adsorbents for optimal uranium uptake. For magnetic control and recycling, the IEX was coated with a layer of Fe 3 O 4 nanoparticles. SEM and EDS mapping images confirm the successful coating of Fe 3 O 4 nanoparticles on the surface of the mIEX (Fig. 1 b). The magnetic hysteresis loops indicate the superparamagnetic property of the mIEX with the Fe 3 O 4 content of 2.2 and 2.6% for the mAIEX and mCIEX, respectively, calculated from the saturation magnetization (Fig. 1 c and S1). A closed-loop system for the adsorption and desorption of uranium consisting of four parts was designed: (a) uranium adsorption by mIEX-MMM, (b) uranium desorption by Na 2 CO 3 (1.0 M) solution, (c) mIEX-MMM regeneration by 1 M NaOH or HCl solution, and (d) rinse by deionized (DI) water (Fig. 1 d). Thanks to the magnetic property, the mIEX-MMM is easily collected and transferred between different cells by a magnet. Characterization of mIEX. Typically, the mIEX as the central part of the micro-reactor can generate long-ranged pH gradient via ion-exchange reaction, which is alkaline for the anionic IEX (mAIEX, Fig. 2 a) and acidic for the cationic IEX (mCIEX, Fig. S3). Due to the different diffusivities of ions, the pH gradient induces local diffusive electric fields, which is pointing outward for the mAIEX as verified by COMSOL Multiphysics simulation (Fig. 2 d). The electric field acts on the double layer of the negatively charged substrate inducing an in-plane diverging electro-osmotic (eo) flow (Fig. 2 b and 2 e). The flow decays linearly with the radial distance over a radial range of ~ 100 µm. Due to the incompressibility of water, the flow is three-dimensional (Fig. 2 c and Video 1) and the convection leads to the approach of the adsorbent towards the mAIEX. Once the adsorbent is assembled with the mAIEX, the symmetry of flow is broken, leading to the self-propulsion of the assembled structure (Fig. 1 g-I and Video 1). For mCIEX, the assembled adsorbent also breaks the symmetry of electric and flow fields, inducing the self-propulsion of the assembly. The size of the mIEX affects the speed of the assembled structure. At a diameter of 45 µm, the mAIEX-MMM reaches an optimal motion speed of 6.9 ± 2.4 µm s − 1 (Fig. S4a). For the mCIEX-MMM, a maximum speed of 3.8 ± 0.9 µm s − 1 was reached with the mCIEX of diameter 45 µm (Fig. S4b). Motion control of mIEX-MMM. To control the motion of the mIEX-MMM, a 3D Helmholtz coil system with integrated imaging and video recording CCD was assembled (Fig. 3 a). Under a rotating magnetic field \(B (t)={B_0}[\text{s}\text{i}\text{n} (2\pi ft) {B_\text{y}}+\text{c}\text{o}\text{s} (2\pi ft) {B_\text{z}}]\) , where B 0 is the amplitude of the magnetic field, f is the rotation frequency of the field, and t is the time, the mAIEX subjected to a rotational torque rolls forward together with the assembled adsorbents. The direction and speed of the mIEX-MMM can be controlled by the magnetic field. As shown in Fig. 3 b, the mIEX-MMM can be directed by the rotating magnetic field of changeable rotating direction to write letters, such as “HUST” (Video 2). To explore regions where the uranium concentration is higher, the velocity of the mAIEX-MMM can be accelerated by the field strength. Figure 3 c shows typical trajectories of mAIEX-MMM under rotating magnetic field of fixed frequency (2 Hz) and different strengths (≥ 70 Gs) within 1 s. The speed of mAIEX-MMM increases from 21.3 ± 5.9 µm s − 1 to 52.2 ± 8.9 µm s − 1 as the field strength increases from 70 Gs to 130 Gs (Fig. 3 d). When the strength of the magnetic field is fixed at 100 Gs, the speed of mAIEX-MMM first increases with field frequency then decreases as the frequency is above 8 Hz, which is the step-out frequency of the mAIEX-MMM (Fig. 3 e). As the input f further increases, the rotation of the mAIEX-MMM becomes asynchronous with the rotating B ( t ) owing to the increasing resistance, and thus the speed gradually decreases 38 . The speed of mCIEX-MMM shows similar changing trend with that of mAIEX-MMM, and a maximum speed of 29.6 ± 17.3 µm s − 1 is obtained at 100 Gs and 12 Hz (Fig. S5). Under defocused NIR ( λ = 808 nm) irradiation, the convective flow generated on the substrate induces the migration of the mAIEX-MMM towards the light source 39 (Fig. 3 f and Video 2). The speed of the mAIEX-MMM increases as the light intensity is increased, reaching a speed of 10.5 ± 2.4 µm s − 1 under the light intensity of 1.4 W cm − 2 (Fig. 3 g). Figure 3 h shows the typical trajectory of the mAIEX-MMM under NIR light irradiation of 0.7 W cm − 2 within 17 s. Uranium extraction performance of the mIEX-MMM. The uranium uptake performance of the mIEX-MMM was explored. The amidoxime groups in the PM can effectively coordinate with uranyl ions (Fig. 4 a). As shown in Fig. 4 b, the introduction of mAIEX accelerates the uranium uptake of the PM (adsorbent with best adsorption in alkaline solution, Fig. S6a). The adsorption equilibrium of the mAIEX-MMM is reached within 10 min, much faster than that of the pure PM. The adsorption capacity of the PM increases from 223.4 ± 12.1 mg g − 1 to 424.5 ± 16.8, 491.7 ± 12.3 and 629.3 ± 18.7 mg g − 1 as the mass ratio of mAIEX to PM is changed from 0 to 0.5, 1 and 2 (Fig. 4 b). Similarly, the introduction of mCIEX accelerates the uranium adsorption of ZP (adsorbent with best adsorption in acidic solution, Fig. S6b) and the equilibrium adsorption amount increases from 269.5 ± 13.5 mg g − 1 (pure ZP) to 428.3 ± 14.0 mg g − 1 (mCIEX:ZP = 2:1, Fig. 4 c). The kinetic adsorption isothermal is well fitted by pseudo-second-order kinetic model, indicating that the uranium adsorption depends on chemical adsorption 18 (see details in Table S1 and S2). The equilibrium adsorption data were well described by a Langmuir model ( R 2 = 0.99, Fig. S7 and Table S3), indicating the single layer adsorption 40 . To explore the mechanism of the promoted uranium adsorption of adsorbent by the introduction of mIEX, numerical simulations were performed to compare the diffusion of uranyl ions in pure diffusive mode and the presence of phoretic flow produced by the mIEX. As shown in Fig. 4 d and S8 (from Video 3), the transport of ions is remarkably accelerated by the phoretic flow. Moreover, the electric field further promotes the diffusion and accumulation of uranyl ions in the vicinity of the mIEX, which can be seen from the uranyl ion concentration difference in Line 1 (Fig. 4 e) and Line 2 (Fig. 4 f). The local pH regulation via the mIEX further enhances the coordination interaction of the uranyl ions and the adsorbent (Fig. S6). Therefore, both uranyl uptake kinetics and capacity are improved by the ion-exchange induced multiple effects. When rotating magnetic field is applied, the speed of the mAIEX-MMM increases, which helps the PM to explore regions where the uranyl ion concentration is high. Therefore, the uranium uptake of the mAIEX-MMM (mass ratio: 2) slightly increases from 629.3 ± 18.7 mg g − 1 to 728.6 ± 24.9 mg g − 1 and 823.0 ± 29.6 mg g − 1 as the rotation field strength increases from 0 to 80 Gs and 120 Gs (Fig. 4 g). Under NIR-driven motion, the photothermal conversion of the Fe 3 O 4 nanoparticles adsorbed on the mAIEX surface increases the temperature of the adsorbent (Fig. S9), inducing the increment of the uranium uptake to 763.8 ± 23.9 mg g − 1 and 829.8 ± 29.9 mg g − 1 at the NIR intensity of 0.7 W cm − 2 and 1.4 W cm − 2 (Fig. 4 h). The uranium adsorption thermodynamics of mIEX-MMM was examined to deeply understand the photothermal-enhanced uranium capture (Fig. S10, Table S4). Δ H > 0 implies the endothermic nature of the uranium adsorption, and Δ G < 0 means the spontaneous process for uranium adsorption 41 . All these results demonstrate that the photothermal conversion of Fe 3 O 4 nanoparticles can enhance the interaction between the adsorbent and uranyl ions via an increased temperature, therefore the uranium adsorption capacity is increased. The uranium uptake of the PM was confirmed by SEM. As shown in Fig. 5 a and S11, the uranium distributes homogeneously throughout the U-uptake PM and ZP. XPS spectra confirms that uranium was bound on the PM with two additional peaks corresponding to the U 4f observed in the full scan spectrum of U-uptake PM (Fig. 5 b). In the high resolution O1s spectra, the appearance of a new peak at 531.1 eV corresponding to the O = U = O also confirms the binding of uranyl ion with the adsorbent 17 (Fig. S12a). Meanwhile, in the FTIR spectra, the new peak at 905 cm − 1 , attributing to the O = U = O (Fig. S12b), indicates the binding of uranyl ions with the PM. Similar results can be observed on the full scan spectrum of mCIEX-MMM (Fig. S13). The reusability of the mIEX-MMM was evaluated by adsorption-desorption cycles. The adsorption capacity remains above 90% of the initial state and the elution efficiency of two mIEX-MMM stays above 84.0 ± 2.6% (Fig. 5 c and Fig. S14) after five cycles, indicating the outstanding reusability of the adsorbent. To demonstrate the potential of large-scale uranium removal, a closed-loop miniplant that could be modified for industrial application was designed (Fig. 5 d, see details in Fig. S15). This miniplant mainly consists of four cells: (i) uranium adsorption by mIEX-MMM, (ii) uranium desorption by Na 2 CO 3 (1 M) solution, (iii) mIEX-MMM regeneration by 1 M NaOH (for mAIEX-MMM) or 1 M HCl (for mCIEX-MMM) solution, and (iv) mIEX-MMM rinse by DI water. Because of the magnetic response of the mIEX, they can be reclaimed by a magnet and dragged to the neighboring cell through the interconnected channels. Figure 5 d (i) exhibits the adsorption cell, where uranium-contaminated water colored by arsenazo was cleaned by mAIEX-MMM after adsorption. After that, the U-uptake mAIEX-MMM was dragged to the desorption cell which can be easily detected from the color change of the cell (Fig. 5 d ii). After exchanging the treated water from the adsorption cell with new contaminated water, a new cycle could start. The refilling and new cycle of treatment could proceed in parallel with mAIEX-MMM regeneration and rinse under autonomous control. The adsorption and desorption efficiencies were detected via UV-Vis spectra (Fig. 5 e). In this small device, mAIEX-MMM were recycled in the loop of four cells and kept over 78% adsorption efficiency and 90% elution efficiency over five cycles (Fig. 5 f). The competitive uranium adsorption with the existence of other metal cations were explored (Fig. 5 g). In simulated polluted underground water, the existence of Na + , K + , Mg 2+ and Ca 2+ does not show obvious influence on the uranium adsorption capacity of self-driven mAIEX-MMM (mass ratio: 2). A uranium adsorption capacity of 623.5 ± 25.5 mg g − 1 , comparable to that in U-spiked water (629.3 ± 18.7 mg g − 1 ) was detected, indicating the good selectivity of PM to uranium. The distribution coefficient ( K d ) value was calculated to be 9.8 × 10 4 mL g − 1 (Fig. 5 h, see detail in SI), indicating an excellent affinity toward uranyl ions 42 , 43 , 44 . Importantly, the mAIEX-MMM with self-regulated pH and self-generated phoretic flow outperforms most of the reported adsorbents in terms of the uranium adsorption performance (Fig. 5 i). Discussion and Conclusion We have constructed a facile and effective mIEX-MMM for recyclable and scalable uranium removal from nonmarine waters. The microreactors are composed of superparamagnetic Fe 3 O 4 decorated ion-exchange resin for dynamic assembly, pH regulation and flow generation, and U-adsorbents. Once exposed to uranium-contaminated water, the mIEX-MMM adsorbs uranium in a fast and effective way as a result of the phoretic flow and self-propulsion accelerated uranium diffusion and increased local uranium concentration. A high uranium adsorption capacity of 629.3 ± 18.7 mg g − 1 for the self-driven, 823.0 ± 29.6 mg g − 1 for the magnetic-driven, and 829.8 ± 29.9 mg g − 1 for NIR-accelerated modes was achieved. This outstanding uranium removal is significantly higher than that of previously reported microrobots along with traditional adsorbents (Fig. 5 i and Table S5). While the estimated cost of mIEX-MMM is merely $ 0.11–0.14 g − 1 (Table S6-8). Considering that the adsorbent can be recycled for at least 5 times, the cost is only $ 1 per ton of U-contaminated water. With this low cost and simple scalability, the ion-exchange based micromotor provides an inexpensive and sustainable alternative to existing uranium removal approaches. To summarize, thanks to the controllable motion property and the effective design strategies, mIEX-MMM may serve as a fascinating toolbox for the uranium removal, sampling, and investigation. Previous pioneering works have showed active removal of uranium with MNMs. However, limited by the short treatment range of the designed MNMs, the adsorption dynamics is still low. From the viewpoint of practical application, the massive synthesis and scalable setup are important factors that need to be considered more in the design of MNMs. From this aspect, our mIEX-MMM is propelled by phoretic flow induced by reversible ion-exchange, which avoids the use of high-energy/toxic chemical fuels and sophisticated actuation setups. The simple structure and easy scale-up preparation of our mIEX-MMM make massive production and industrial application possible, which ensures cost-effective and seamless integration with current water treatment facilities. In spite of the progress made in this work, further work may investigate the application of designed mIEX-MMM to advanced “capture and reduction” tactic 45 , 46 , 47 to further enlarge the uranium collection in one shot. Materials And Methods Preparation of adsorbents. MIL-88B was prepared by ball-milling method according to the procedures reported in the literature 35 . Briefly, 12.00 g of poly(ethylene terephthalate) powder and 5.00 g of NaOH were firstly added to a ball milling jar (volume: 1.5 L) and operated at 400 rpm for 4 h to form 1,4-benzenedicarboxylic sodium salt. Secondly, 25.25 g of Fe(NO 3 ) 3 ·9H 2 O was added to the ball milling jar and sequentially milled for 3 h. Finally, the obtained orange powder named MIL-88B was centrifugally washed in water for three times and ethanol for twice, and dried at 80°C for 12 h. Polyamidoxime (PAO) was prepared by the amidoximation of polyacrylonitrile (PAN) 36 . Briefly, 5.56 g of NH 2 OH·HCl was dissolved in 60 mL DMF and heated at 45°C under magnetic stirring. Then, 3.82 g Na 2 CO 3 and 0.96 g NaOH were added to the above solution and stirred for another 3 h. Next, 4.24 g PAN was dissolved in the above solution at 65°C. After 24 h, 1.91 g and 0.48 g NaOH were added and reacted for 12 h to form a yellow transparent solution. Preparation of PAO@MIL-88B (PM): 40 mg MIL-88B was dissolved in 1 mL PAO solution (about 70 mg) under ultrasonication, which was then precipitated in water under magnetic stirring. Ultimately, the product was centrifuged, washed with water and freeze-dried for later use. Preparation of ZIF-8@poly(AA-co-AM) (ZP): ZIF-8@poly(AA-co-AM) was prepared according to the previous literature with some adjustments 34 . At first, Zn(NO 3 ) 2 ·6H 2 O and 2-methyl imidazole were added in a breaker containing 300 mL methanol and then heated at 60°C for 24 h. The as-formed white precipitates were washed three times with deionized water and ethanol before drying at 60°C overnight. 60 mg of the obtained ZIF-8 with a diameter of around 1 µm were dispersed in 0.2 mL H 2 O via ultrasonication. Then, 0.709 g AM, 0.645 g AA, 0.015 g cross-linker BIS, and 0.1 g photoinitiator HMPP were added to the above solution in sequence under stirring to form the precursor solution. Next, 0.3 g span80 was added into 30 mL paraffin oil to form the oil phase. After that, the precursor solution was added to the oil phase and the mixture was subjected to mechanical stirring at a speed of 800 rpm for 15 min to emulsify. Then the emulsion was exposed to UV light (intensity: 70 mW cm − 2 ) for 5 min to trigger the in-situ polymerization of the emulsion droplets. Finally, the product was repeatedly washed with hexane and ethanol before use. Fabrication of magnetic-IEX (mIEX). Magnetic IEXs were prepared by functioning IEX with Fe 3 O 4 . Fe 3 O 4 nanoparticles were prepared according to the literature 37 . Briefly, 1.62 g FeCl 3 ·6H 2 O and 1.39 g FeSO 4 ·7H 2 O were mixed with 40 mL of DI water and heated up to 90°C under continuous stirring. Then, 5 mL of 28% ammonia so4ution was slowly mixed with the above solution. Next, 4.4 g sodium citrate was dropped to the solution under stirring. After the solution was cooled down to room temperature, the formed Fe 3 O 4 nanoparticles were separated by a magnet, and washed by ethanol and DI water three times. The synthesized Fe 3 O 4 nanoparticles had a diameter of 8–10 nm and superparamagnetic characteristic (Fig. S16). 50 mg of Fe 3 O 4 nanoparticles were dispersed in 20 mL of DI water assisted by ultrasonication and used for following experiments. To construct mIEX, the AIEX and CIEX were immersed in 20% NaOH solution and 20% HCl solutions to exchange the counterions into OH − and H + , respectively. After washing with DI water to pH ~ 7, the resin particles (200 mg) were mixed with 5 mL of Fe 3 O 4 dispersion under oscillation for 24 h. Finally, the mIEX were collected by a magnet. Numerical simulation. COMSOL Multiphysics package was used to simulate the diffusion and electric fields, as well as fluid flow around mAIEX using Transport of Diluted Species, Electrostatics, and Creeping Flow modules (see details in Note S1). The phoretic flow and local electric field accelerated diffusion of uranium towards the mAIEX-MMS was also modeled by COMSOL Multiphysics (see details in Note S2). Actuation of mIEX-MMM. Self-propulsion: 5.2 µL PM/ZP suspension (2.5 mg mL − 1 ) was first added to a sample cell containing 400 µL deionized water. Then, mIEX suspension (10 mg mL − 1 ) of different volumes was put into the sample cell to reach PM/ZP to mIEX mass ratios of 0, 0.5, 1 and 2. Then the sample cell was quickly covered with a glass slide to avoid contamination by dust. Samples were observed on an upright optical microscope (Carl Zeiss AG, Germany) and the videos were recorded at a frame rate of 30 fps via a CCD camera. All videos were analyzed using Tracker V08.01 and ImageJ software. NIR actuation: firstly, 380 µL of deionized water containing a certain number of mIEX-MMM was dropped into a sample cell mounted on an inverted optical microscope (DMIRBE, Leica, Germany). Next, the sample was irradiated by a NIR laser (λ = 808 nm) with a tilt angle of 45° at different intensities. A data acquisition unit (Keysight 34972A) connected with a thermocouple was used to record the temperature of the mIEX-MMM suspension under NIR irradiation. Magnetic actuation: the magnetic actuation of mIEX-MMM was carried out with a 3D Helmholtz coil system consisting of electric current supplies (HEAS-20 Power Amplifiers, China), DG1022Z arbitrary waveform signal generators, and 3-axis Helmholtz electromagnetic coils. mIEX-MMM were navigated by a rotating magnetic field ( B ( t )) of different directions, intensities B 0 , and frequencies f . Closed-loop miniplant experiment. Closed-loop uranium removal was verified in a miniplant consisted of four treatment cells. Based on the flow design, continuous large-scale uranium removal can be performed via repeated cycle of uranium adsorption (cell I), uranium desorption (cell II), mAIEX-MMM regeneration (cell III), and mAIEX-MMM rinse processes (cell IV). Typically, 1 mL of uranium solution of 30 ppm was first added to cell (I), followed by adding 0.033 mg PM and 0.067mg mAIEX to the uranium-contaminated water to form the mAIEX-MMM for adsorption. After adsorption, mAIEX-MMM was transferred to cell (II) containing 1 M Na 2 CO 3 solution (1.0 mL) by a magnet for desorption. Then the mAIEX-MMM were transferred to the regeneration cell (III), where OH- in mAIEX-MMM was regenerated by 20% NaOH solution (1 mL). Last, the mAIEX-MMM were washed by DI water in cell (IV), meanwhile the reclaimed water in cell (I) was released. The rinsed mAIEX-MMM and another batch of U-contaminated water were added for the next cycle of treatment. Statistical analysis. To ensure the reliability and consistency of the results, data were presented as “mean ± standard errors” resulted from the average of multiple replicate measurements (60–80 for velocity characterization and three for uranium adsorption). Standard errors were calculated by dividing the standard deviation by the square root of the sample size. One-way ANOVA was conducted to characterize the significance of the difference, and the differences were considered significant at P < 0.05. Declarations Declare of Interests The authors declare no competing interests. Acknowledgements The present work is supported by National Natural Science Foundation of China (No. 22102059), and the Innovation and Talent Recruitment Base of New Energy Chemistry and Device (No. B21003). We are grateful to the Analytical and Testing Centre of HUST for access to their facilities. References Chu S, Majumdar A (2012) Opportunities and challenges for a sustainable energy future. Nature 488:294–303 Yuan Y et al (2020) DNA nano-pocket for ultra-selective uranyl extraction from seawater. Nat Commun 11:5708 Tsouris C (2017) Uranium extraction: fuel from seawater. Nat Energy 2:17022 Wei X et al (2024) Phosphate and illite colloid pose a synergistic risk of enhanced uranium transport in groundwater: A challenge for phosphate immobilization remediation of uranium contaminated environmental water. Water Res 255:121514 Schnug E, Lottermoser BG (2013) Fertilizer-derived uranium and its threat to human health. Environ Sci Technol 47:2433–2434 Bales C et al (2023) Removal of trace uranium from groundwaters using membrane capacitive deionization desalination for potable supply in remote communities: bench, pilot, and field scale investigations. Environ Sci Technol 57:11345–11355 Lin T et al (2024) Ion pair sites for efficient electrochemical extraction of uranium in real nuclear wastewater. Nat Commun 15:4149 Dang DH, Novotnik B, Wang W, Georg RB, Evans RD (2016) Uranium isotope fractionation during adsorption, (Co)precipitation, and biotic reduction. Environ Sci Technol 50:12695–12704 Tapia-Rodriguez A, Luna-Velasco A, Field JA, Sierra-Alvarez R (2010) Anaerobic bioremediation of hexavalent uranium in groundwater by reductive precipitation with methanogenic granular sludge. Water Res 44:2153–2162 Amphlett JTM, Choi S, Parry SA, Moon EM, Sharrad CA, Ogden MD (2020) Insights on uranium uptake mechanisms by ion exchange resins with chelating functionalities: Chelation vs. anion exchange. Chem Eng J 392:123712 Hernández J, Ruiz D (2021) Removal of chloride ions from a copper leaching solution, using electrodialysis, to improve the uranium extraction through ion-exchange. J Hazard Mater 420:126582 Zhang W et al (2022) Rapid and manual-shaking exfoliation of amidoximated cellulose nanofibrils for a large-capacity filtration capture of uranium. J Mater Chem A 10:7920–7927 Sholl DS, Lively RP (2016) Seven chemical separations to change the world. Nature 532:435–437 Wang D et al (2018) Significantly enhanced uranium extraction from seawater with mass produced fully amidoximated nanofiber adsorbent. Adv Energy Mater 8:1802607 Yuan Y et al (2019) Ultrafast and highly selective uranium extraction from seawater by hydrogel-like spidroin‐based protein fiber. Angew Chem Int Ed 58:11785–11790 Liang H, Mu Y, Yin M, He P, Guo W (2023) Solar-powered simultaneous highly efficient seawater desalination and highly specific target extraction with smart DNA hydrogels. Sci Adv 9:1677 Wang H, Yao W, Yuan Y, Shi S, Liu T, Wang N (2024) Yeast-raised polyamidoxime hydrogel prepared by ice crystal dispersion for efficient uranium extraction from seawater. Adv Sci 11:2306534 He N et al (2024) Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy. Nat Commun 15:3896 Xu T, Gao W, Xu LP, Zhang X, Wang S (2016) Fuel-free synthetic micro‐/nanomachines. Adv Mater 29:1603250 Wang W, Mallouk TE (2021) A practical guide to analyzing and reporting the movement of nanoscale swimmers. ACS Nano 15:15446–15460 Chen M et al (2021) Programmable dynamic shapes with a swarm of light-powered colloidal motors. Angew Chem Int Ed 60:16674–16679 Kong L, Mayorga-Martinez CC, Guan J, Pumera M (2019) Photocatalytic micromotors activated by UV to visible light for environmental remediation, micropumps, reversible assembly, transportation, and biomimicry. Small 16:1903179 Peng X, Urso M, Kolackova M, Huska D, Pumera M (2023) Biohybrid magnetically driven microrobots for sustainable removal of micro/nanoplastics from the aquatic environment. Adv Funct Mater 34:2307477 Wang Q, Xiang N, Lang J, Wang B, Jin D, Zhang L (2023) Reconfigurable Liquid-Bodied Miniature Machines: Magnetic Control and Microrobotic Applications. Adv Intell Syst 6 Parmar J, Vilela D, Villa K, Wang J, Sánchez S (2018) Micro- and nanomotors as active environmental microcleaners and sensors. J Am Chem Soc 140:9317–9331 Hu Y, Liu W, Sun Y (2021) Self-propelled micro‐/nanomotors as On‐the‐Move platforms: cleaners, sensors, and reactors. Adv Funct Mater 32:2109181 Ye H, Wang Y, Xu D, Liu X, Liu S, Ma X (2021) Design and fabrication of micro/nano-motors for environmental and sensing applications. Appl Mater 23:101007 Chen X, Li H, Yang K, Haleem A, Sun Y, Pan J (2024) Significantly enhanced uranium extraction by intelligent light-driven nanorobot catchers with precise controllable moving trajectory. J Hazard Mater 469:133908 Ying Y, Pourrahimi AM, Sofer Z, Matějková S, Pumera M (2019) Radioactive uranium preconcentration via self-propelled autonomous microrobots based on metal-organic frameworks. ACS Nano 13:11477–11487 Xie H et al (2019) Reconfigurable magnetic microrobot swarm: Multimode transformation, locomotion, and manipulation. Sci Robot 4:8006 Kong L, Ambrosi A, Nasir MZM, Guan J, Pumera M (2019) Self-propelled 3D‐printed Aircraft carrier of light‐powered smart micromachines for large‐volume nitroaromatic explosives removal. Adv Funct Mater 29:1903872 Wang W (2023) Open questions of chemically powered nano- and micromotors. J Am Chem Soc 145:27185–27197 Xing Y et al (2020) Core@satellite janus nanomotors with pH-responsive multi‐phoretic propulsion. Angew Chem Int Ed 59:14368–14372 Zhang X et al (2024) Dual-functional metal-organic frameworks-based hydrogel micromotor for uranium detection and removal. J Hazard Mater 467:133654 He P et al (2023) Mechanochemistry milling of waste poly(ethylene terephthalate) into metal-organic frameworks. Chemsuschem 16:e202201935 Ma C et al (2019) Sunlight Polymerization of Poly(amidoxime) Hydrogel Membrane for Enhanced Uranium Extraction from Seawater. Adv Sci 6:1900085 Li W et al (2022) Self-driven magnetorobots for recyclable and scalable micro/nanoplastic removal from nonmarine waters. Sci Adv 8:1731 Xie M et al (2020) Bioinspired soft microrobots with precise magneto-collective control for microvascular thrombolysis. Adv Mater 32:e2000366 Deng Z, Mou F, Tang S, Xu L, Luo M, Guan J (2018) Swarming and collective migration of micromotors under near infrared light. Appl Mater 13:45–53 Rahmani-Sani A, Hosseini-Bandegharaei A, Hosseini S-H, Kharghani K, Zarei H, Rastegar A (2015) Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid. J Hazard Mater 286:152–163 Li S et al (2019) Graphene oxide based dopamine mussel-like cross-linked polyethylene imine nanocomposite coating with enhanced hexavalent uranium adsorption. J Mater Chem A 7:16902–16911 Li Z et al (2012) Uranium(VI) adsorption on graphene oxide nanosheets from aqueous solutions. Chem Eng J 210:539–546 Li L, Ma W, Shen S, Huang H, Bai Y, Liu H (2016) A combined experimental and theoretical study on the extraction of uranium by amino-derived metal-organic frameworks through post-synthetic strategy. ACS Appl Mater Interfaces 8:31032–31041 Li H et al (2023) Zwitterion functionalized graphene oxide / polyacrylamide / polyacrylic acid hydrogels with photothermal conversion and antibacterial properties for highly efficient uranium extraction from seawater. Adv Funct Mater 33:2301773 Zhang H et al (2019) Three mechanisms in one material: uranium capture by a polyoxometalate-organic framework through combined complexation, chemical reduction, and photocatalytic reduction. Angew Chem Int Ed 58:16110–16114 Li H et al (2019) Powerful uranium extraction strategy with combined ligand complexation and photocatalytic reduction by postsynthetically modified photoactive metal-organic frameworks. Appl Catal B: Environ 254:47–54 Chen Y-R et al (2023) Constructing redox-active 3D covalent organic frameworks with high-affinity hexameric binding sites for enhanced uranium capture. Chem Eng J 459:141633 Additional Declarations There is NO Competing Interest. Supplementary Files Supplementaryinformation.docx Video1.mp4 Video 1 Video2.mp4 Video2 Video3.mp4 Video3 Cite Share Download PDF Status: Posted 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-4489134","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":309160716,"identity":"0d70a2da-c5d8-48d6-84c3-a514b214824e","order_by":0,"name":"Ran Niu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYDACZjBpkwDhsRGvJS0BwiJKCwQcJkGLOTuP2YefO87nGZw/f4DhQ9lhBv7ZDfi1WDbzGM/sPXO72OBGMgPjjHOHGSTuHMCvxeAwjzEDb9vtxA03mBmYedsOMxhIJBDWwvi37VzihvOHGZj/EqsFaPiBxA0HkhmYGYnTwlbMLNuWnDjzRrLBwZ5z6TwSNwhpOX94M+PbNrvEvvMHHz74UWYtxz+DgBYUcACIeUhQPwpGwSgYBaMAFwAA7aJBdhxdUkIAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-7791-3914","institution":"Huazhong University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Ran","middleName":"","lastName":"Niu","suffix":""},{"id":309160717,"identity":"a9837c9c-1492-46a5-9227-542198ec95b9","order_by":1,"name":"Linhui Fu","email":"","orcid":"","institution":"Huazhong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Linhui","middleName":"","lastName":"Fu","suffix":""},{"id":309160718,"identity":"9f7b24a8-959c-44b9-a225-9945ad7602c3","order_by":2,"name":"Kai Feng","email":"","orcid":"","institution":"Huazhong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Feng","suffix":""},{"id":309160719,"identity":"c1ffbf2a-7bbe-4f31-b14b-f6a2be3005c4","order_by":3,"name":"Xinle Zhang","email":"","orcid":"","institution":"Huazhong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Xinle","middleName":"","lastName":"Zhang","suffix":""},{"id":309160720,"identity":"3d0f622e-f2e7-4ca2-891a-f0d31a996e51","order_by":4,"name":"Ling Chen","email":"","orcid":"","institution":"Huazhong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Ling","middleName":"","lastName":"Chen","suffix":""},{"id":309160721,"identity":"cb45f359-54f9-4ea2-882f-37170fc00295","order_by":5,"name":"Jiang Gong","email":"","orcid":"","institution":"School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 China.","correspondingAuthor":false,"prefix":"","firstName":"Jiang","middleName":"","lastName":"Gong","suffix":""},{"id":309160722,"identity":"6f0172a3-c770-4c0f-9770-89c3f73f6cde","order_by":6,"name":"Jin-ping Qu","email":"","orcid":"","institution":"Huazhong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jin-ping","middleName":"","lastName":"Qu","suffix":""}],"badges":[],"createdAt":"2024-05-28 08:01:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4489134/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4489134/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57643471,"identity":"64c683ba-05f5-4f9d-ab19-86b0a9aa4ff2","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2020825,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign and characterization of magnetic ion-exchange-based modular micromotors.\u003c/strong\u003e (a) Schematic of the co-assembly of mIEX and adsorbents (ZP: ZIF-8@poly(Acrylic acid-co-Acrylamide), PM: Polyamidoxime(PAO)@MIL-88B) into autonomous modular microreactor for uranium adsorption. (b) SEM and EDS mapping images of mAIEX. (c) Magnetic hysteresis loops of mAIEX and mCIEX. Inset shows the collection of mAIEX by a magnet. (d) Illustration of the closed-loop system for adsorption and desorption of uranium by mAIEX-MMM.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/2bf3c6879901115d4af3a72c.png"},{"id":57643466,"identity":"d41784fc-0ff1-492a-ab01-e3d0af684ef6","added_by":"auto","created_at":"2024-06-03 18:20:14","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1671701,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacteristics of mIEX\u003c/strong\u003e. (a) Color map of the pH gradient generated by mAIEX on a glass substrate. (b) Decay of the diverging flow velocity with radial distance from the center of the mAIEX. (c) 3D flow generated by the mAIEX (Video 1). COMSOL simulation result of (d) the pH gradient, (e) the electric potential and (f) the flow generated by the ion-exchange process of the mAIEX. (g-i) Images showing the co-assembly of the adsorbent with the mAIEX and the self-propulsion of the assembled structure (Video 1).\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/404391e21795b6c5b53e5cf9.png"},{"id":57643470,"identity":"42c57508-efe6-46e7-879a-d69f8210173d","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1754174,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMotion control of mIEX-MMM\u003c/strong\u003e. (a) Schematic illustration of the 3D Helmholtz coil for motion control of the mIEX-MMM. (b) English letters “HUST” written by mAIEX-MMM controlled by \u003cem\u003exz\u003c/em\u003e-rotating magnetic fields (\u003cem\u003eB\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e=80 Gs, \u003cem\u003ef\u003c/em\u003e=10 Hz, Video 2). (c) Representative trajectories of the mAIEX-MMM under \u003cem\u003exz\u003c/em\u003e-rotating magnetic field of different strengths (\u003cem\u003ef\u003c/em\u003e=2 Hz). The time window for the trajectory is 1 s. Scale bar: 50 μm. Rolling speed of the mAIEX-MMM as a function of (d) the field intensity (\u003cem\u003ef\u003c/em\u003e= 2 Hz) and (e) the field frequency (\u003cem\u003eB\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e= 100 Gs). (f) Schematic illustration of the NIR-driven migration of the mAIEX-MMM. (g) Speed of the mAIEX-MMM under various NIR intensities. (h) Typical trajectory of the mAIEX-MMM under NIR light irradiation of 0.7 W cm\u003csup\u003e-2\u003c/sup\u003e (Video 2).\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/9f170af07078c758b3638654.png"},{"id":57643467,"identity":"56407bb7-665c-4c09-90cb-501ae9467a85","added_by":"auto","created_at":"2024-06-03 18:20:14","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1203680,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUranium adsorption performance of mIEX-MMM\u003c/strong\u003e. (a) The proposed U(VI) capture mechanism by mAIEX-MMM. Uranium uptake by (b) mAIEX-MMM and (c) mCIEX-MMM of different mass ratios of the two components (uranium concentration: 30 ppm). (d) Numerical simulation of ion diffusion driven by pure diffusion and flow-accelerated diffusion. Uranium concentration at (e) line 1 and (f) line 2 as a function of the distance to the right edge. Uranium adsorption capacity of mAIEX-MMM (mass ratio: 2) as a function of (g) the rotating magnetic field and (h) the NIR intensity.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/5aa2874dbb002af6c6a29fa8.png"},{"id":57643474,"identity":"4b9fb813-a78a-41ef-b7c5-27284f35d945","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1321741,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUranyl adsorbing mechanism, recycle and selectivity properties of mIEX-MMM\u003c/strong\u003e. (a) SEM and EDS-mapping images of U-uptake PM. (b) The survey XPS spectra of mAIEX-MMM before and after uranium adsorption. (c) The uranium adsorption capacity and desorption rate of the self-driven mAIEX-MMM (mass ratio: 2) in five adsorption-desorption cycles (elution solution: 0.1 M Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, regeneration solution: 1 M NaOH). (d) Schematic of the closed-loop miniplant including four cells: adsorption, desorption, regeneration and rinse. (e) UV-Vis spectra of the uranium solution before and after different numbers of cycle. (f) Adsorption and desorption efficiencies of the self-driven mAIEX-MMM (mass ratio: 2) in the miniplant under recycled use. (g) Uranium uptake of the self-driven mAIEX-MMM (mass ratio: 2) in simulated contaminated underground water with the co-existence of other metal ions (uranium: 30 ppm, Na\u003csup\u003e+\u003c/sup\u003e: 13.3 ppm, K\u003csup\u003e+\u003c/sup\u003e: 1.7 ppm, Mg\u003csup\u003e2+\u003c/sup\u003e:\u003csup\u003e \u003c/sup\u003e3.6 ppm, Ca\u003csup\u003e2+\u003c/sup\u003e: 28.9 ppm). (h) Distribution coefficient \u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e values of various ions. (i) Comparison of the uranium uptake capacity of mAIEX-MMM (mass ratio: 2) with other adsorbents reported in the literature.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/cfe9558e4d0e05c4e554837e.png"},{"id":60573346,"identity":"d6e3cfb1-f6a9-4c90-a953-84e5a6d9b185","added_by":"auto","created_at":"2024-07-18 10:03:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9702708,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/aae4d67b-5c0c-4c4c-b3c8-90f17277a520.pdf"},{"id":57643473,"identity":"22335b85-5f44-4090-b5ff-0d84dd1ceb9d","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1704891,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/2ba807f6005142b64af56aee.docx"},{"id":57643468,"identity":"0c390dbf-911d-4663-8e17-94fae1585f2b","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":4073817,"visible":true,"origin":"","legend":"\u003cp\u003eVideo 1\u003c/p\u003e","description":"","filename":"Video1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/90e3c7e756a340fb44e50c78.mp4"},{"id":57643475,"identity":"a495609c-ebeb-4ecb-adec-6700c5f981ba","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":3406891,"visible":true,"origin":"","legend":"\u003cp\u003eVideo2\u003c/p\u003e","description":"","filename":"Video2.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/17eac2874206c44fa073140e.mp4"},{"id":57643472,"identity":"6e3da411-8fc5-45aa-afe0-60ea9b32bb9e","added_by":"auto","created_at":"2024-06-03 18:20:15","extension":"mp4","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":3900632,"visible":true,"origin":"","legend":"\u003cp\u003eVideo3\u003c/p\u003e","description":"","filename":"Video3.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4489134/v1/180d4902c1e3c9e46762195a.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors","fulltext":[{"header":"Introduction","content":"\u003cp\u003eUranium is the essential resource of nuclear energy, which is one of the most widely explored greenhouse-gas-free energy\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, the radioactive contamination that results from the energy production route causes severe environmental challenges due to its accumulation and harmful effects to living creatures\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Therefore, it is of vital importance to extract uranium from polluted waters in a facile way. Among the various ways to extract uranium, such as electrochemistry\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e, chemical/biochemical reductive precipitation\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e, ion exchange\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e and filtration\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, adsorption is one of the most commonly used approaches due to its easy operation, low cost and effectiveness\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. The key for fast and effective uranium extraction is the design of adsorbents. A variety of adsorbents, including polymeric fibers, polymeric hydrogels, and porous materials have been designed\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. However, traditional adsorbents rely on the passive diffusion of uranyl ions for adsorption, which is normally low and limits the adsorption kinetics. In addition, most of the adsorbents work in acidic or alkaline condition for best coordination with uranyl ions, which requires the pre-treatment of solution with chemicals and may cause secondary pollution. Therefore, advanced uranium adsorbents with active ion transport and local pH regulation are highly required for fast uranium removal.\u003c/p\u003e \u003cp\u003eMicro/nanomotors (MNMs), capable of converting energy from surrounding environments into self-propelled motion, have shown great potential in environmental remediation\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. The active motion of the MNMs promotes the mixing of pollutants and agents, which therefore accelerates the treatment efficiency\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The development of MNMs has enabled various micromachines that can be actuated by bubble, light or magnetic fields for uranium removal\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. For example, metal-organic frameworks (MOFs)-based micromotor with implementation of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and catalytic platinum nanoparticles shows bubble propelled motion in the presence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, as well as motion-enhanced uranium uptake (384 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e29\u003c/sup\u003e. Pan et al. designed near-infrared light (NIR)-driven nanorobot with amidoxime as adsorption site for uranium capture. The extraction amount of the self-driven nanorobot was increased by about 16.7% during the first 5 min. Both NIR-driven motion and NIR-induced temperature increase contribute to the fast uranium extraction\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. In our previous work, MOFs-based hydrogel micromotor of magnetic actuation was used for uranium detection and adsorption. The magnetic-actuated motion enhances the contact between uranium and the adsorption site, which therefore accelerates the uranium detection and removal efficiency\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. However, the short treatment range of MNMs, from electrostatic attraction or short-ranged phoretic flow limits their removal efficiency with adsorption equilibrium reached in more than 1 h. Meanwhile the unavoidable global pH regulation causes secondary pollution as well as increased cost. Therefore, intelligent MNMs with self-locomotion, self-pH regulation and long-range flow are urgently required to solve above problems.\u003c/p\u003e \u003cp\u003eIn this work, an ion-exchange-based modular microreactor with long-range flow and self-pH regulation is constructed for fast uranium removal. Generally, the ion-exchange unit provides long-range phoretic flow for enhanced uranium diffusion towards the adsorbent, and local pH regulation to enhance the interaction between adsorbent and the uranyl ion. The implemented Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles on the surface of the ion-exchange resin further enables the magnetic and NIR actuation of the microreactor to adapt to different application environments. Numerical simulation result confirms the enhanced uranium diffusion towards the adsorbent by the flow and local electric field. As a result, uranium adsorption equilibrium is quickly reached within 10 min, as well as a high uranium uptake amount of 629.3 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in 30 ppm uranium solution.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e \u003cb\u003eConstruction of magnetic ion-exchange-based modular micromotors.\u003c/b\u003e The magnetic ion-exchange-based modular micromotors (mIEX-MMM) for uranium adsorption consists of two fundamental parts, magnetic ion exchange-based micro-fluidic pumps for assembly, motion control and local pH regulation of the adsorbent, and the adsorbents for uranium adsorption (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Typically, the mIEX as the central part of the micro-reactor can generate long-ranged pH gradient and electro-osmotic (eo) flow via ion-exchange reaction for the assembly of adsorbents. The eo-flow also accelerates the diffusion of uranium to the adsorbent and increases the uranium concentration around the adsorbent. Meanwhile, the mIEX tunes the local pH environment of the assembled adsorbents for optimal uranium uptake. For magnetic control and recycling, the IEX was coated with a layer of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles. SEM and EDS mapping images confirm the successful coating of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles on the surface of the mIEX (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The magnetic hysteresis loops indicate the superparamagnetic property of the mIEX with the Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e content of 2.2 and 2.6% for the mAIEX and mCIEX, respectively, calculated from the saturation magnetization (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and S1). A closed-loop system for the adsorption and desorption of uranium consisting of four parts was designed: (a) uranium adsorption by mIEX-MMM, (b) uranium desorption by Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e (1.0 M) solution, (c) mIEX-MMM regeneration by 1 M NaOH or HCl solution, and (d) rinse by deionized (DI) water (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Thanks to the magnetic property, the mIEX-MMM is easily collected and transferred between different cells by a magnet.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eCharacterization of mIEX.\u003c/b\u003e Typically, the mIEX as the central part of the micro-reactor can generate long-ranged pH gradient via ion-exchange reaction, which is alkaline for the anionic IEX (mAIEX, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) and acidic for the cationic IEX (mCIEX, Fig. S3). Due to the different diffusivities of ions, the pH gradient induces local diffusive electric fields, which is pointing outward for the mAIEX as verified by COMSOL Multiphysics simulation (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). The electric field acts on the double layer of the negatively charged substrate inducing an in-plane diverging electro-osmotic (eo) flow (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). The flow decays linearly with the radial distance over a radial range of ~\u0026thinsp;100 \u0026micro;m. Due to the incompressibility of water, the flow is three-dimensional (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec and Video 1) and the convection leads to the approach of the adsorbent towards the mAIEX. Once the adsorbent is assembled with the mAIEX, the symmetry of flow is broken, leading to the self-propulsion of the assembled structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg-I and Video 1). For mCIEX, the assembled adsorbent also breaks the symmetry of electric and flow fields, inducing the self-propulsion of the assembly. The size of the mIEX affects the speed of the assembled structure. At a diameter of 45 \u0026micro;m, the mAIEX-MMM reaches an optimal motion speed of 6.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig. S4a). For the mCIEX-MMM, a maximum speed of 3.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was reached with the mCIEX of diameter 45 \u0026micro;m (Fig. S4b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eMotion control of mIEX-MMM.\u003c/b\u003e To control the motion of the mIEX-MMM, a 3D Helmholtz coil system with integrated imaging and video recording CCD was assembled (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Under a rotating magnetic field \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(B (t)={B_0}[\\text{s}\\text{i}\\text{n} (2\\pi ft) {B_\\text{y}}+\\text{c}\\text{o}\\text{s} (2\\pi ft) {B_\\text{z}}]\\)\u003c/span\u003e\u003c/span\u003e, where \u003cem\u003eB\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e is the amplitude of the magnetic field, \u003cem\u003ef\u003c/em\u003e is the rotation frequency of the field, and \u003cem\u003et\u003c/em\u003e is the time, the mAIEX subjected to a rotational torque rolls forward together with the assembled adsorbents. The direction and speed of the mIEX-MMM can be controlled by the magnetic field. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the mIEX-MMM can be directed by the rotating magnetic field of changeable rotating direction to write letters, such as \u0026ldquo;HUST\u0026rdquo; (Video 2). To explore regions where the uranium concentration is higher, the velocity of the mAIEX-MMM can be accelerated by the field strength. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec shows typical trajectories of mAIEX-MMM under rotating magnetic field of fixed frequency (2 Hz) and different strengths (\u0026ge;\u0026thinsp;70 Gs) within 1 s. The speed of mAIEX-MMM increases from 21.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 52.2\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as the field strength increases from 70 Gs to 130 Gs (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). When the strength of the magnetic field is fixed at 100 Gs, the speed of mAIEX-MMM first increases with field frequency then decreases as the frequency is above 8 Hz, which is the step-out frequency of the mAIEX-MMM (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). As the input \u003cem\u003ef\u003c/em\u003e further increases, the rotation of the mAIEX-MMM becomes asynchronous with the rotating \u003cem\u003eB\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e) owing to the increasing resistance, and thus the speed gradually decreases\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. The speed of mCIEX-MMM shows similar changing trend with that of mAIEX-MMM, and a maximum speed of 29.6\u0026thinsp;\u0026plusmn;\u0026thinsp;17.3 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is obtained at 100 Gs and 12 Hz (Fig. S5).\u003c/p\u003e \u003cp\u003eUnder defocused NIR (\u003cem\u003eλ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;808 nm) irradiation, the convective flow generated on the substrate induces the migration of the mAIEX-MMM towards the light source\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef and Video 2). The speed of the mAIEX-MMM increases as the light intensity is increased, reaching a speed of 10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4 \u0026micro;m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e under the light intensity of 1.4 W cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh shows the typical trajectory of the mAIEX-MMM under NIR light irradiation of 0.7 W cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e within 17 s.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eUranium extraction performance of the mIEX-MMM.\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe uranium uptake performance of the mIEX-MMM was explored. The amidoxime groups in the PM can effectively coordinate with uranyl ions (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, the introduction of mAIEX accelerates the uranium uptake of the PM (adsorbent with best adsorption in alkaline solution, Fig. S6a). The adsorption equilibrium of the mAIEX-MMM is reached within 10 min, much faster than that of the pure PM. The adsorption capacity of the PM increases from 223.4\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 424.5\u0026thinsp;\u0026plusmn;\u0026thinsp;16.8, 491.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.3 and 629.3\u0026thinsp;\u0026plusmn;\u0026thinsp;18.7 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as the mass ratio of mAIEX to PM is changed from 0 to 0.5, 1 and 2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). Similarly, the introduction of mCIEX accelerates the uranium adsorption of ZP (adsorbent with best adsorption in acidic solution, Fig. S6b) and the equilibrium adsorption amount increases from 269.5\u0026thinsp;\u0026plusmn;\u0026thinsp;13.5 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (pure ZP) to 428.3\u0026thinsp;\u0026plusmn;\u0026thinsp;14.0 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (mCIEX:ZP\u0026thinsp;=\u0026thinsp;2:1, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). The kinetic adsorption isothermal is well fitted by pseudo-second-order kinetic model, indicating that the uranium adsorption depends on chemical adsorption\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e (see details in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e and S2). The equilibrium adsorption data were well described by a Langmuir model (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.99, Fig. S7 and Table S3), indicating the single layer adsorption\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. To explore the mechanism of the promoted uranium adsorption of adsorbent by the introduction of mIEX, numerical simulations were performed to compare the diffusion of uranyl ions in pure diffusive mode and the presence of phoretic flow produced by the mIEX. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed and S8 (from Video 3), the transport of ions is remarkably accelerated by the phoretic flow. Moreover, the electric field further promotes the diffusion and accumulation of uranyl ions in the vicinity of the mIEX, which can be seen from the uranyl ion concentration difference in Line 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee) and Line 2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef). The local pH regulation via the mIEX further enhances the coordination interaction of the uranyl ions and the adsorbent (Fig. S6). Therefore, both uranyl uptake kinetics and capacity are improved by the ion-exchange induced multiple effects.\u003c/p\u003e \u003cp\u003eWhen rotating magnetic field is applied, the speed of the mAIEX-MMM increases, which helps the PM to explore regions where the uranyl ion concentration is high. Therefore, the uranium uptake of the mAIEX-MMM (mass ratio: 2) slightly increases from 629.3\u0026thinsp;\u0026plusmn;\u0026thinsp;18.7 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 728.6\u0026thinsp;\u0026plusmn;\u0026thinsp;24.9 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 823.0\u0026thinsp;\u0026plusmn;\u0026thinsp;29.6 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as the rotation field strength increases from 0 to 80 Gs and 120 Gs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg). Under NIR-driven motion, the photothermal conversion of the Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles adsorbed on the mAIEX surface increases the temperature of the adsorbent (Fig. S9), inducing the increment of the uranium uptake to 763.8\u0026thinsp;\u0026plusmn;\u0026thinsp;23.9 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 829.8\u0026thinsp;\u0026plusmn;\u0026thinsp;29.9 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at the NIR intensity of 0.7 W cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e and 1.4 W cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh). The uranium adsorption thermodynamics of mIEX-MMM was examined to deeply understand the photothermal-enhanced uranium capture (Fig. S10, Table S4). Δ\u003cem\u003eH\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0 implies the endothermic nature of the uranium adsorption, and Δ\u003cem\u003eG\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0 means the spontaneous process for uranium adsorption\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. All these results demonstrate that the photothermal conversion of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles can enhance the interaction between the adsorbent and uranyl ions via an increased temperature, therefore the uranium adsorption capacity is increased.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe uranium uptake of the PM was confirmed by SEM. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and S11, the uranium distributes homogeneously throughout the U-uptake PM and ZP. XPS spectra confirms that uranium was bound on the PM with two additional peaks corresponding to the U\u003csub\u003e4f\u003c/sub\u003e observed in the full scan spectrum of U-uptake PM (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). In the high resolution O1s spectra, the appearance of a new peak at 531.1 eV corresponding to the O\u0026thinsp;=\u0026thinsp;U\u0026thinsp;=\u0026thinsp;O also confirms the binding of uranyl ion with the adsorbent\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e (Fig. S12a). Meanwhile, in the FTIR spectra, the new peak at 905 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, attributing to the O\u0026thinsp;=\u0026thinsp;U\u0026thinsp;=\u0026thinsp;O (Fig. S12b), indicates the binding of uranyl ions with the PM. Similar results can be observed on the full scan spectrum of mCIEX-MMM (Fig. S13).\u003c/p\u003e \u003cp\u003eThe reusability of the mIEX-MMM was evaluated by adsorption-desorption cycles. The adsorption capacity remains above 90% of the initial state and the elution efficiency of two mIEX-MMM stays above 84.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6% (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and Fig. S14) after five cycles, indicating the outstanding reusability of the adsorbent. To demonstrate the potential of large-scale uranium removal, a closed-loop miniplant that could be modified for industrial application was designed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, see details in Fig. S15). This miniplant mainly consists of four cells: (i) uranium adsorption by mIEX-MMM, (ii) uranium desorption by Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e (1 M) solution, (iii) mIEX-MMM regeneration by 1 M NaOH (for mAIEX-MMM) or 1 M HCl (for mCIEX-MMM) solution, and (iv) mIEX-MMM rinse by DI water. Because of the magnetic response of the mIEX, they can be reclaimed by a magnet and dragged to the neighboring cell through the interconnected channels. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed (i) exhibits the adsorption cell, where uranium-contaminated water colored by arsenazo was cleaned by mAIEX-MMM after adsorption. After that, the U-uptake mAIEX-MMM was dragged to the desorption cell which can be easily detected from the color change of the cell (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed ii). After exchanging the treated water from the adsorption cell with new contaminated water, a new cycle could start. The refilling and new cycle of treatment could proceed in parallel with mAIEX-MMM regeneration and rinse under autonomous control. The adsorption and desorption efficiencies were detected via UV-Vis spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). In this small device, mAIEX-MMM were recycled in the loop of four cells and kept over 78% adsorption efficiency and 90% elution efficiency over five cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef).\u003c/p\u003e \u003cp\u003eThe competitive uranium adsorption with the existence of other metal cations were explored (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg). In simulated polluted underground water, the existence of Na\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, Mg\u003csup\u003e2+\u003c/sup\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e does not show obvious influence on the uranium adsorption capacity of self-driven mAIEX-MMM (mass ratio: 2). A uranium adsorption capacity of 623.5\u0026thinsp;\u0026plusmn;\u0026thinsp;25.5 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, comparable to that in U-spiked water (629.3\u0026thinsp;\u0026plusmn;\u0026thinsp;18.7 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was detected, indicating the good selectivity of PM to uranium. The distribution coefficient (\u003cem\u003eK\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e) value was calculated to be 9.8 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e mL g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh, see detail in SI), indicating an excellent affinity toward uranyl ions\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. Importantly, the mAIEX-MMM with self-regulated pH and self-generated phoretic flow outperforms most of the reported adsorbents in terms of the uranium adsorption performance (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei).\u003c/p\u003e"},{"header":"Discussion and Conclusion","content":"\u003cp\u003eWe have constructed a facile and effective mIEX-MMM for recyclable and scalable uranium removal from nonmarine waters. The microreactors are composed of superparamagnetic Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e decorated ion-exchange resin for dynamic assembly, pH regulation and flow generation, and U-adsorbents. Once exposed to uranium-contaminated water, the mIEX-MMM adsorbs uranium in a fast and effective way as a result of the phoretic flow and self-propulsion accelerated uranium diffusion and increased local uranium concentration. A high uranium adsorption capacity of 629.3\u0026thinsp;\u0026plusmn;\u0026thinsp;18.7 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for the self-driven, 823.0\u0026thinsp;\u0026plusmn;\u0026thinsp;29.6 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for the magnetic-driven, and 829.8\u0026thinsp;\u0026plusmn;\u0026thinsp;29.9 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for NIR-accelerated modes was achieved. This outstanding uranium removal is significantly higher than that of previously reported microrobots along with traditional adsorbents (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei and Table S5). While the estimated cost of mIEX-MMM is merely \u003cspan\u003e$\u003c/span\u003e 0.11\u0026ndash;0.14 g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Table S6-8). Considering that the adsorbent can be recycled for at least 5 times, the cost is only \u003cspan\u003e$\u003c/span\u003e1 per ton of U-contaminated water. With this low cost and simple scalability, the ion-exchange based micromotor provides an inexpensive and sustainable alternative to existing uranium removal approaches.\u003c/p\u003e \u003cp\u003eTo summarize, thanks to the controllable motion property and the effective design strategies, mIEX-MMM may serve as a fascinating toolbox for the uranium removal, sampling, and investigation. Previous pioneering works have showed active removal of uranium with MNMs. However, limited by the short treatment range of the designed MNMs, the adsorption dynamics is still low. From the viewpoint of practical application, the massive synthesis and scalable setup are important factors that need to be considered more in the design of MNMs. From this aspect, our mIEX-MMM is propelled by phoretic flow induced by reversible ion-exchange, which avoids the use of high-energy/toxic chemical fuels and sophisticated actuation setups. The simple structure and easy scale-up preparation of our mIEX-MMM make massive production and industrial application possible, which ensures cost-effective and seamless integration with current water treatment facilities. In spite of the progress made in this work, further work may investigate the application of designed mIEX-MMM to advanced \u0026ldquo;capture and reduction\u0026rdquo; tactic \u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e to further enlarge the uranium collection in one shot.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e \u003cb\u003ePreparation of adsorbents.\u003c/b\u003e MIL-88B was prepared by ball-milling method according to the procedures reported in the literature\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. Briefly, 12.00 g of poly(ethylene terephthalate) powder and 5.00 g of NaOH were firstly added to a ball milling jar (volume: 1.5 L) and operated at 400 rpm for 4 h to form 1,4-benzenedicarboxylic sodium salt. Secondly, 25.25 g of Fe(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO was added to the ball milling jar and sequentially milled for 3 h. Finally, the obtained orange powder named MIL-88B was centrifugally washed in water for three times and ethanol for twice, and dried at 80\u0026deg;C for 12 h.\u003c/p\u003e \u003cp\u003ePolyamidoxime (PAO) was prepared by the amidoximation of polyacrylonitrile (PAN)\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. Briefly, 5.56 g of NH\u003csub\u003e2\u003c/sub\u003eOH\u0026middot;HCl was dissolved in 60 mL DMF and heated at 45\u0026deg;C under magnetic stirring. Then, 3.82 g Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e and 0.96 g NaOH were added to the above solution and stirred for another 3 h. Next, 4.24 g PAN was dissolved in the above solution at 65\u0026deg;C. After 24 h, 1.91 g and 0.48 g NaOH were added and reacted for 12 h to form a yellow transparent solution.\u003c/p\u003e \u003cp\u003ePreparation of PAO@MIL-88B (PM): 40 mg MIL-88B was dissolved in 1 mL PAO solution (about 70 mg) under ultrasonication, which was then precipitated in water under magnetic stirring. Ultimately, the product was centrifuged, washed with water and freeze-dried for later use.\u003c/p\u003e \u003cp\u003ePreparation of ZIF-8@poly(AA-co-AM) (ZP): ZIF-8@poly(AA-co-AM) was prepared according to the previous literature with some adjustments\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. At first, Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO and 2-methyl imidazole were added in a breaker containing 300 mL methanol and then heated at 60\u0026deg;C for 24 h. The as-formed white precipitates were washed three times with deionized water and ethanol before drying at 60\u0026deg;C overnight. 60 mg of the obtained ZIF-8 with a diameter of around 1 \u0026micro;m were dispersed in 0.2 mL H\u003csub\u003e2\u003c/sub\u003eO via ultrasonication. Then, 0.709 g AM, 0.645 g AA, 0.015 g cross-linker BIS, and 0.1 g photoinitiator HMPP were added to the above solution in sequence under stirring to form the precursor solution. Next, 0.3 g span80 was added into 30 mL paraffin oil to form the oil phase. After that, the precursor solution was added to the oil phase and the mixture was subjected to mechanical stirring at a speed of 800 rpm for 15 min to emulsify. Then the emulsion was exposed to UV light (intensity: 70 mW cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) for 5 min to trigger the in-situ polymerization of the emulsion droplets. Finally, the product was repeatedly washed with hexane and ethanol before use.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFabrication of magnetic-IEX (mIEX).\u003c/b\u003e Magnetic IEXs were prepared by functioning IEX with Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e. Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles were prepared according to the literature\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Briefly, 1.62 g FeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO and 1.39 g FeSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;7H\u003csub\u003e2\u003c/sub\u003eO were mixed with 40 mL of DI water and heated up to 90\u0026deg;C under continuous stirring. Then, 5 mL of 28% ammonia so4ution was slowly mixed with the above solution. Next, 4.4 g sodium citrate was dropped to the solution under stirring. After the solution was cooled down to room temperature, the formed Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles were separated by a magnet, and washed by ethanol and DI water three times. The synthesized Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles had a diameter of 8\u0026ndash;10 nm and superparamagnetic characteristic (Fig. S16). 50 mg of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles were dispersed in 20 mL of DI water assisted by ultrasonication and used for following experiments.\u003c/p\u003e \u003cp\u003eTo construct mIEX, the AIEX and CIEX were immersed in 20% NaOH solution and 20% HCl solutions to exchange the counterions into OH\u003csup\u003e\u0026minus;\u003c/sup\u003e and H\u003csup\u003e+\u003c/sup\u003e, respectively. After washing with DI water to pH\u0026thinsp;~\u0026thinsp;7, the resin particles (200 mg) were mixed with 5 mL of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e dispersion under oscillation for 24 h. Finally, the mIEX were collected by a magnet.\u003c/p\u003e \u003cp\u003e \u003cb\u003eNumerical simulation.\u003c/b\u003e COMSOL Multiphysics package was used to simulate the diffusion and electric fields, as well as fluid flow around mAIEX using Transport of Diluted Species, Electrostatics, and Creeping Flow modules (see details in Note S1). The phoretic flow and local electric field accelerated diffusion of uranium towards the mAIEX-MMS was also modeled by COMSOL Multiphysics (see details in Note S2).\u003c/p\u003e \u003cp\u003e \u003cb\u003eActuation of mIEX-MMM.\u003c/b\u003e Self-propulsion: 5.2 \u0026micro;L PM/ZP suspension (2.5 mg mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was first added to a sample cell containing 400 \u0026micro;L deionized water. Then, mIEX suspension (10 mg mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) of different volumes was put into the sample cell to reach PM/ZP to mIEX mass ratios of 0, 0.5, 1 and 2. Then the sample cell was quickly covered with a glass slide to avoid contamination by dust. Samples were observed on an upright optical microscope (Carl Zeiss AG, Germany) and the videos were recorded at a frame rate of 30 fps via a CCD camera. All videos were analyzed using Tracker V08.01 and ImageJ software.\u003c/p\u003e \u003cp\u003eNIR actuation: firstly, 380 \u0026micro;L of deionized water containing a certain number of mIEX-MMM was dropped into a sample cell mounted on an inverted optical microscope (DMIRBE, Leica, Germany). Next, the sample was irradiated by a NIR laser (λ\u0026thinsp;=\u0026thinsp;808 nm) with a tilt angle of 45\u0026deg; at different intensities. A data acquisition unit (Keysight 34972A) connected with a thermocouple was used to record the temperature of the mIEX-MMM suspension under NIR irradiation.\u003c/p\u003e \u003cp\u003eMagnetic actuation: the magnetic actuation of mIEX-MMM was carried out with a 3D Helmholtz coil system consisting of electric current supplies (HEAS-20 Power Amplifiers, China), DG1022Z arbitrary waveform signal generators, and 3-axis Helmholtz electromagnetic coils. mIEX-MMM were navigated by a rotating magnetic field (\u003cem\u003eB\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e)) of different directions, intensities \u003cem\u003eB\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e, and frequencies \u003cem\u003ef\u003c/em\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eClosed-loop miniplant experiment.\u003c/b\u003e Closed-loop uranium removal was verified in a miniplant consisted of four treatment cells. Based on the flow design, continuous large-scale uranium removal can be performed via repeated cycle of uranium adsorption (cell I), uranium desorption (cell II), mAIEX-MMM regeneration (cell III), and mAIEX-MMM rinse processes (cell IV). Typically, 1 mL of uranium solution of 30 ppm was first added to cell (I), followed by adding 0.033 mg PM and 0.067mg mAIEX to the uranium-contaminated water to form the mAIEX-MMM for adsorption. After adsorption, mAIEX-MMM was transferred to cell (II) containing 1 M Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e solution (1.0 mL) by a magnet for desorption. Then the mAIEX-MMM were transferred to the regeneration cell (III), where OH- in mAIEX-MMM was regenerated by 20% NaOH solution (1 mL). Last, the mAIEX-MMM were washed by DI water in cell (IV), meanwhile the reclaimed water in cell (I) was released. The rinsed mAIEX-MMM and another batch of U-contaminated water were added for the next cycle of treatment.\u003c/p\u003e \u003cp\u003e \u003cb\u003eStatistical analysis.\u003c/b\u003e To ensure the reliability and consistency of the results, data were presented as \u0026ldquo;mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard errors\u0026rdquo; resulted from the average of multiple replicate measurements (60\u0026ndash;80 for velocity characterization and three for uranium adsorption). Standard errors were calculated by dividing the standard deviation by the square root of the sample size. One-way ANOVA was conducted to characterize the significance of the difference, and the differences were considered significant at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclare of\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eInterests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present work is supported by National Natural Science Foundation of China (No. 22102059), and the Innovation and Talent Recruitment Base of New Energy Chemistry and Device (No. B21003). We are grateful to the Analytical and Testing Centre of HUST for access to their facilities.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChu S, Majumdar A (2012) Opportunities and challenges for a sustainable energy future. Nature 488:294\u0026ndash;303\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuan Y et al (2020) DNA nano-pocket for ultra-selective uranyl extraction from seawater. Nat Commun 11:5708\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTsouris C (2017) Uranium extraction: fuel from seawater. Nat Energy 2:17022\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWei X et al (2024) Phosphate and illite colloid pose a synergistic risk of enhanced uranium transport in groundwater: A challenge for phosphate immobilization remediation of uranium contaminated environmental water. Water Res 255:121514\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchnug E, Lottermoser BG (2013) Fertilizer-derived uranium and its threat to human health. Environ Sci Technol 47:2433\u0026ndash;2434\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBales C et al (2023) Removal of trace uranium from groundwaters using membrane capacitive deionization desalination for potable supply in remote communities: bench, pilot, and field scale investigations. Environ Sci Technol 57:11345\u0026ndash;11355\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin T et al (2024) Ion pair sites for efficient electrochemical extraction of uranium in real nuclear wastewater. Nat Commun 15:4149\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDang DH, Novotnik B, Wang W, Georg RB, Evans RD (2016) Uranium isotope fractionation during adsorption, (Co)precipitation, and biotic reduction. Environ Sci Technol 50:12695\u0026ndash;12704\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTapia-Rodriguez A, Luna-Velasco A, Field JA, Sierra-Alvarez R (2010) Anaerobic bioremediation of hexavalent uranium in groundwater by reductive precipitation with methanogenic granular sludge. Water Res 44:2153\u0026ndash;2162\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmphlett JTM, Choi S, Parry SA, Moon EM, Sharrad CA, Ogden MD (2020) Insights on uranium uptake mechanisms by ion exchange resins with chelating functionalities: Chelation vs. anion exchange. Chem Eng J 392:123712\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHern\u0026aacute;ndez J, Ruiz D (2021) Removal of chloride ions from a copper leaching solution, using electrodialysis, to improve the uranium extraction through ion-exchange. J Hazard Mater 420:126582\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang W et al (2022) Rapid and manual-shaking exfoliation of amidoximated cellulose nanofibrils for a large-capacity filtration capture of uranium. J Mater Chem A 10:7920\u0026ndash;7927\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSholl DS, Lively RP (2016) Seven chemical separations to change the world. Nature 532:435\u0026ndash;437\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang D et al (2018) Significantly enhanced uranium extraction from seawater with mass produced fully amidoximated nanofiber adsorbent. Adv Energy Mater 8:1802607\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuan Y et al (2019) Ultrafast and highly selective uranium extraction from seawater by hydrogel-like spidroin‐based protein fiber. Angew Chem Int Ed 58:11785\u0026ndash;11790\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiang H, Mu Y, Yin M, He P, Guo W (2023) Solar-powered simultaneous highly efficient seawater desalination and highly specific target extraction with smart DNA hydrogels. Sci Adv 9:1677\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang H, Yao W, Yuan Y, Shi S, Liu T, Wang N (2024) Yeast-raised polyamidoxime hydrogel prepared by ice crystal dispersion for efficient uranium extraction from seawater. Adv Sci 11:2306534\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe N et al (2024) Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy. Nat Commun 15:3896\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu T, Gao W, Xu LP, Zhang X, Wang S (2016) Fuel-free synthetic micro‐/nanomachines. Adv Mater 29:1603250\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang W, Mallouk TE (2021) A practical guide to analyzing and reporting the movement of nanoscale swimmers. ACS Nano 15:15446\u0026ndash;15460\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen M et al (2021) Programmable dynamic shapes with a swarm of light-powered colloidal motors. Angew Chem Int Ed 60:16674\u0026ndash;16679\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKong L, Mayorga-Martinez CC, Guan J, Pumera M (2019) Photocatalytic micromotors activated by UV to visible light for environmental remediation, micropumps, reversible assembly, transportation, and biomimicry. Small 16:1903179\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeng X, Urso M, Kolackova M, Huska D, Pumera M (2023) Biohybrid magnetically driven microrobots for sustainable removal of micro/nanoplastics from the aquatic environment. Adv Funct Mater 34:2307477\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Q, Xiang N, Lang J, Wang B, Jin D, Zhang L (2023) Reconfigurable Liquid-Bodied Miniature Machines: Magnetic Control and Microrobotic Applications. Adv Intell Syst 6\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParmar J, Vilela D, Villa K, Wang J, S\u0026aacute;nchez S (2018) Micro- and nanomotors as active environmental microcleaners and sensors. J Am Chem Soc 140:9317\u0026ndash;9331\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu Y, Liu W, Sun Y (2021) Self-propelled micro‐/nanomotors as On‐the‐Move platforms: cleaners, sensors, and reactors. Adv Funct Mater 32:2109181\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYe H, Wang Y, Xu D, Liu X, Liu S, Ma X (2021) Design and fabrication of micro/nano-motors for environmental and sensing applications. Appl Mater 23:101007\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen X, Li H, Yang K, Haleem A, Sun Y, Pan J (2024) Significantly enhanced uranium extraction by intelligent light-driven nanorobot catchers with precise controllable moving trajectory. J Hazard Mater 469:133908\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYing Y, Pourrahimi AM, Sofer Z, Matějkov\u0026aacute; S, Pumera M (2019) Radioactive uranium preconcentration via self-propelled autonomous microrobots based on metal-organic frameworks. ACS Nano 13:11477\u0026ndash;11487\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie H et al (2019) Reconfigurable magnetic microrobot swarm: Multimode transformation, locomotion, and manipulation. Sci Robot 4:8006\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKong L, Ambrosi A, Nasir MZM, Guan J, Pumera M (2019) Self-propelled 3D‐printed Aircraft carrier of light‐powered smart micromachines for large‐volume nitroaromatic explosives removal. Adv Funct Mater 29:1903872\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang W (2023) Open questions of chemically powered nano- and micromotors. J Am Chem Soc 145:27185\u0026ndash;27197\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXing Y et al (2020) Core@satellite janus nanomotors with pH-responsive multi‐phoretic propulsion. Angew Chem Int Ed 59:14368\u0026ndash;14372\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang X et al (2024) Dual-functional metal-organic frameworks-based hydrogel micromotor for uranium detection and removal. J Hazard Mater 467:133654\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe P et al (2023) Mechanochemistry milling of waste poly(ethylene terephthalate) into metal-organic frameworks. Chemsuschem 16:e202201935\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMa C et al (2019) Sunlight Polymerization of Poly(amidoxime) Hydrogel Membrane for Enhanced Uranium Extraction from Seawater. Adv Sci 6:1900085\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi W et al (2022) Self-driven magnetorobots for recyclable and scalable micro/nanoplastic removal from nonmarine waters. Sci Adv 8:1731\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie M et al (2020) Bioinspired soft microrobots with precise magneto-collective control for microvascular thrombolysis. Adv Mater 32:e2000366\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeng Z, Mou F, Tang S, Xu L, Luo M, Guan J (2018) Swarming and collective migration of micromotors under near infrared light. Appl Mater 13:45\u0026ndash;53\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRahmani-Sani A, Hosseini-Bandegharaei A, Hosseini S-H, Kharghani K, Zarei H, Rastegar A (2015) Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid. J Hazard Mater 286:152\u0026ndash;163\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi S et al (2019) Graphene oxide based dopamine mussel-like cross-linked polyethylene imine nanocomposite coating with enhanced hexavalent uranium adsorption. J Mater Chem A 7:16902\u0026ndash;16911\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Z et al (2012) Uranium(VI) adsorption on graphene oxide nanosheets from aqueous solutions. Chem Eng J 210:539\u0026ndash;546\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi L, Ma W, Shen S, Huang H, Bai Y, Liu H (2016) A combined experimental and theoretical study on the extraction of uranium by amino-derived metal-organic frameworks through post-synthetic strategy. ACS Appl Mater Interfaces 8:31032\u0026ndash;31041\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi H et al (2023) Zwitterion functionalized graphene oxide / polyacrylamide / polyacrylic acid hydrogels with photothermal conversion and antibacterial properties for highly efficient uranium extraction from seawater. Adv Funct Mater 33:2301773\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang H et al (2019) Three mechanisms in one material: uranium capture by a polyoxometalate-organic framework through combined complexation, chemical reduction, and photocatalytic reduction. Angew Chem Int Ed 58:16110\u0026ndash;16114\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi H et al (2019) Powerful uranium extraction strategy with combined ligand complexation and photocatalytic reduction by postsynthetically modified photoactive metal-organic frameworks. Appl Catal B: Environ 254:47\u0026ndash;54\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Y-R et al (2023) Constructing redox-active 3D covalent organic frameworks with high-affinity hexameric binding sites for enhanced uranium capture. Chem Eng J 459:141633\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Micro/nanomotors, Uranium adsorption, Diffusion, Ion-exchange, Phoretic flow","lastPublishedDoi":"10.21203/rs.3.rs-4489134/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4489134/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAs the fundamental resource in nuclear energy, uranium is a sword of two sides, due to its radioactive character that could cause severe impact to the environment and living creatures once released by accident. However, limited by the passive ion transport, the currently available uranium adsorbents still suffer from low adsorption rate and capacity. Here, we report a self-driven modular micro-reactor composed of magnetizable ion-exchange resin and adsorbents that can be used to dynamically remove uranium from nonmarine waters. Because of the long-range pH gradient and phoretic flow established by the recyclable ion-exchange resin, the micro-reactor shows a fast uranium adsorption rate and reaches a uranium extraction capacity of 629.3 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e within 20 min in 30 ppm uranium solution, as well as good recyclability in repeated use. Numerical simulation result confirms that the phoretic flow and electric field accelerate uranium transport to the adsorbent. Our work provides a new solution for the removal of radioactive uranium with high efficiency and low-effectiveness.\u003c/p\u003e","manuscriptTitle":"Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-03 18:20:09","doi":"10.21203/rs.3.rs-4489134/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bad947ad-435b-4490-9bcd-f0edcaee588d","owner":[],"postedDate":"June 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":32668826,"name":"Earth and environmental sciences/Environmental sciences/Environmental chemistry/Pollution remediation"},{"id":32668827,"name":"Physical sciences/Materials science/Soft materials/Colloids"}],"tags":[],"updatedAt":"2024-07-18T09:55:27+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-03 18:20:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4489134","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4489134","identity":"rs-4489134","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}