Phosphorus removal performance of spark deposited iron and aluminium metal oxide nanoparticles on polyacrylonitrile membranes

Phosphorus removal performance of spark deposited iron and aluminium metal oxide nanoparticles on polyacrylonitrile membranes | 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 Research Article Phosphorus removal performance of spark deposited iron and aluminium metal oxide nanoparticles on polyacrylonitrile membranes Wei Zhao, Zhengyuan Shang, Yandun Jin, Huipeng Zhou, Jianan Yao, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7514055/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Jan, 2026 Read the published version in Environmental Processes → Version 1 posted 10 You are reading this latest preprint version Abstract Eutrophication of water bodies including lake and river is becoming increasingly serious, and controlling phosphate concentration in such water bodies is the key to solving the eutrophication problem. Adsorption technology provides a more practical solution for phosphate removal due to the advantages of easy operation, low cost, no highly toxic by-products and recyclability. Therefore, in this study, the adsorption method was used to adsorb phosphate from water bodies and the concentration of phosphate after adsorption was determined. Iron-aluminium oxide nanoparticles were prepared by electric spark ablation, and then iron and aluminium oxide composite nanoparticles were deposited on polyacrylonitrile (PAN) membranes using electrostatic spinning to obtain FeAl-ESA@PAN fibrous membranes for phosphorus removal from aqueous environments. Due to the nano constraints of the fibre membrane, the problem of unfavorable recycling and reuse of metal oxides in powder form is effectively solved. It was modified by using magnetic medium Fe, which not only improved the adsorption performance and service life of the adsorbent material, but also reduced the production cost. The adsorption experiments showed that the adsorption capacity of FeAl-ESA@PAN for phosphate was 21.05 mg·g − 1 and the variables such as reaction time, pH and coexisting ions had a significant effect on the adsorption capacity. The influence of FeAl-ESA@PAN on phosphorus removal from lake water was investigated for Qilu Lake (Yunnan, China) as an example, and the total phosphorus removal rate observed was 94.01%, and a series of characterisations indicated that electrostatic adsorption, hydrogen bonding, complexation, and ion-exchange were the main mechanisms of phosphorus removal. Phosphate uptake iron-aluminum oxides electrostatic spinning Eutrophication Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Phosphorus is the raw material for the synthesis of all living cells and is an essential nutrient for plant growth. However, excessive phosphorus in water bodies can cause deterioration of water quality by algal blooms, reduction of oxygen content in water and loss of biodiversity, which can damage the normal function of water bodies and threaten human health (Glibert, 2017 ). According to research, 80% of eutrophication is caused by excessive phosphorus input, so phosphorus is critical factor in controlling eutrophication (Wang et al., 2018 ). Currently, there are many methods to remove phosphate from water bodies, including adsorption (Jin et al., 2024 ), bioremediation (Wang et al., 2022 ), chemical precipitation (Yago et al., 2024 ) and membrane separation (Gao et al., 2019 ). Among them, the adsorption method has the advantages of simple operation, no highly toxic by-products and recycling (Wang et al., 2023 ), especially in the treatment of low concentration phosphate wastewater. Based on this, the research and development of materials with excellent adsorption performance has become a trend. Metal oxides are widely used in wastewater treatment due to their high adsorption activity, high adsorption capacity, and easy to be processed and modified (Ma et al., 2025 ). Among them, aluminium-based materials represented by alumina have strong adsorption properties for phosphate in solution, and are a class of phosphate removers that have been thoroughly studied and practically applied (Huang et al., 2017 ). It is usually believed that the aluminium sites on the surface of activated alumina are first hydroxylated in solution, and with different solution pH, the solid surface non-specifically adsorbs H + or OH − , and the phosphate ions (PO 4 3− ) in solution can be bound to the solid surface by both electrostatic gravitational force or ion exchange (Yin et al., 2024 ). In order to improve the adsorption performance and lifetime of adsorbent materials, it is usually modified with magnetic media.Iron oxides are ubiquitous in natural soils and water bodies, and are inexpensive and biocompatible (Lal et al., 2024 ). Adil et al. (2023) have successfully recovered phosphate from water by using iron-carbon nanotubes (Fe-CNTs). The adsorption capacity of Fe-CNTs is far superior to that of the pristine CNTs. Experimentally, Fe-CNTs have demonstrated a better adsorption capacity than pristine CNTs. Fe-CNT showed a phosphate removal efficiency 7 times higher than that of pristine CNT. Sun et al. ( 2023 ) obtained aluminium-iron biomodified biochar (AFBC) by dual modification of maize biochar with AlCl 3 and FeCl 3 , and achieved a total phosphorus removal rate of 90.97% in rural wastewater treatment. However, the powdered metal oxides are not favourable for recycling and reuse, and in order to solve this problem, blending the metal oxides into the carrier is a good choice. The low-cost electrostatic spinning process is a very attractive technique, which produces nanofibrous membranes with high specific surface area, high porosity, high flux, etc (Wang et al., 2022 ; Wei et al., 2021 ). The process anchors a large amount of metal oxides without altering the chemical properties of the metal oxides (Lee et al., 2018 ), which makes it a good candidate for immobilising the metal oxides. Polyacrylonitrile (PAN) is a common polymer material that has been used in nanotextiles, filtration and metal ion adsorption (HMTShirazi et al., 2022 ; Thimmiah and Nallathambi, 2022 ). In addition, PAN fibres are often used as matrix materials for adsorbents due to their ideal chemical resistance, thermal stability and low flammability (Karimzadeh et al., 2023 ; Nasimi et al., 2020 ). Based on these advantages, PAN was selected as the matrix material for electrostatic spinning in this study. For the choice of porogenic agent (Fakhry et al., 2022 ), this study focuses on polyvinylpyrrolidone (PVP), a water-soluble polymer mainly formed by the polymerisation of vinylpyrrolidone in water or isopropyl alcohol. Its key advantage is that it can be easily removed from nanofibres by heating and boiling (Pourmadadi et al., 2023 ). More importantly, even a trace amount of PVP residue improves the hydrophilicity and solubility of the composite film (HMTShirazi et al., 2022 ), which helps to facilitate the contact of the active sites with the phosphate molecules. Therefore, in this thesis, polymetallic oxide adsorbents were prepared using spark ablation technique and combined with electrostatic spinning technique to immobilise the metal oxides on porous nanofibres to obtain polymetallic oxide composite membranes aimed at: Prepare FeAl bimetallic oxide nanoparticles by spark ablation and immobilise them on modified polyacrylonitrile (PAN) membranes to prepare polymetallic oxide composite membranes. A series of adsorption experiments (pH, co-existing ions, adsorption isotherms, adsorption kinetics, regeneration performance and stability) were performed and the adsorption behaviour and adsorption performance were evaluated. Characterisation was carried out to elucidate the adsorption behaviour and mechanism of FeAl-ESA@PAN for the removal of phosphorus from water. Test the phosphorus removal effect of FeAl-ESA@PAN in lake water bodies to provide new ideas for the management of eutrophication in lakes. 2. Materials and methods 2.1. Materials and chemicals Hydrochloric acid (HCl) and potassium dihydrogen phosphate (KH 2 PO 4 , ≥ 99.5%) were purchased from Chengdu Cologne Chemical Co. Sodium hydroxide (NaOH) was purchased from Sinopharm Chemical Reagent Co Ltd (China). All reagents were analytically pure without further purification. Filters with a pore size of 0.22 µm supplied by Tianjin Pilot Test Equipment Co (China). The gas (2%O 2 + 98%N 2 ) supplied by Kunming Hongfa Deli Gas Co (China). Nano aerosol sintering deposition system (VSP-G1) was supplied by Fosner (Shanghai) Scientific Instruments Co. The UV-Vis spectrophotometer (GENESYS 50) was supplied by Thermo Fisher (USA). Natural water samples were obtained from Qilu Lake, Yunnan Province, China, and were refrigerated. 2.2. FeAl-ESA @PAN composite film preparation In this study, FeAl-ESA nanoparticles were prepared by spark ablation technique. Firstly, the iron electrode was fixed at the cathode of the VSP and the aluminium electrode was fixed at the anode, and the working voltage and current were set to 1.36 KV and 10.4 mA, respectively. Subsequently, the power supply was turned on, the nitrogen-oxygen mixture was passed in (the flow rate of the gas stream was controlled to be 3 L/min), and the instrument was preheated for 2–3 min before the ignition switch was pressed, and the spark was generated between the electrodes, and the electrode material evaporated under the ablation of the spark, and the small vapour cloud reacted with the room temperature of the The small vapour cloud reacts with the carrier gas at room temperature and condenses to form metal oxide nanoparticles. The nanoparticles were deposited on the pre-prepared mixed filter membrane with the direction of the carrier gas, and finally the nanoparticles on the filter membrane were collected to obtain FeAl-ESA. Polyacrylonitrile (PAN) is a polymer with acrylonitrile as the smallest unit, which has the potential to be used in different scientific fields due to its plasticity, low cost and excellent wettability. Many scholars have been working on the preparation of hybrid nanofibres with special functionalities by adding some organic or inorganic components (e.g., nanoparticles). Therefore, in this study, certain amounts of metal oxides and PVP (pore maker) were added to the PAN spinning solution with a view to improving its adsorption characteristics for phosphate. The specific steps were as follows: first, 1 g of PAN, 10 mg of metal oxide nanoparticles, and a certain amount of PVP were dissolved in 10 mL of DMF mixed solution, where PVP (wt%) : PAN (wt%) = 1:1, and then the mixed solution was stirred at 60°C for 2 h on a magnetic stirrer to fully dissolve and mix the spinning solution. Finally, the spinning solution was injected into a 10 mL syringe and spun at a flow rate of 1.2 ml/h at 25 kV. After the spinning was completed, the release paper loaded with nanofibres was removed and treated in hot water at 80°C for 24 h to wash away the PVP. After washing, freeze-drying was carried out for 48 h to finally obtain FeAl-ESA@PAN fibrous membranes. 2.3. Characterisation The surface morphology of the adsorbents was analysed using a scanning electron microscope (SEM, Zeiss Sigma 300, Zeiss GmbH, Germany), and images of the surface morphology of the samples were taken at different magnifications. The specific surface area of the adsorbent was determined using the BET method (Quantachrome-EVO, Florida, USA). The identification of the crystalline phase species of the adsorbent was determined using X-ray diffraction (XRD, Rigaku Ultima IV, Rigaku Rigaku Co., Japan). X-ray photoelectron spectroscopy (XPS, EscaLab250Xi, Thermo Fisher Scientific, USA) was used to examine the elemental composition of the adsorbent surfaces before and after adsorption as well as changes in the chemical state under the following conditions: addition of surface-contaminated carbon C1s (284.80 eV) calibration of binding energies for all spectra, and use of an Al-Kα target (1486.6 eV, 72 W) to read the data. Fourier Transform Infrared Spectroscopy (FTIR) (Nicolet IS 50, Thermo Fisher Scientific) was used to determine changes in the wavelength range of 400–4000 cm − 1 . Zeta potential analyser (SurPASS, Anton Paarl, Austria) was used to study its charge at different pH. Inductively coupled plasma mass spectrometer (ICP, Agilent 5110, Agilent Technologies Ltd., China) measured the residual amount of metal ions in the water after adsorption. 2.4. Adsorption experiments Potassium dihydrogen phosphate (KH 2 PO 4 ) was used to formulate simulated phosphorus-containing wastewater with different concentrations (in terms of PO 4 3− ) in all the experiments. Specifically, 0.06 g /L of adsorbent and a certain amount of phosphorus-containing wastewater were accurately weighed in a 100 mL conical flask. The solution was continuously shaken at 200 rpm for 48 h at room temperature using a thermostatic shaking chamber to ensure that adsorption equilibrium was reached. The adsorbed solution was filtered by 0.22 µm microporous filter membrane, and the residual phosphorus concentration was determined by ammonium molybdate spectrophotometry (GB 11893-89). Each experiment was repeated three times to take the average value, and finally, the removal efficiency η (%) and adsorption capacity q e (mg/g) of the adsorbent on phosphate were calculated according to the equations ( 1 ) and ( 2 ): $$\:\eta\:\:=\:\frac{{C}_{0}\:-\:{C}_{e}}{{C}_{0}}\:\times\:\:100$$ 1 $$\:{q}_{e}\:=\:\frac{\left({C}_{0}\:-\:{C}_{e}\right)V}{m}$$ 2 where C 0 and C e (mg/L) denote the initial concentration of phosphate and the concentration after adsorption equilibrium; V (L) denotes the volume of phosphate solution; and m (g) denotes the mass of adsorbent added. The pH of the solution strongly affects the surface charge of FeAl-ESA@PAN as well as the charge behaviour of phosphate, so it is necessary to investigate the effect of pH on the adsorption behaviour. 0.06 g /L of adsorbent was put into 50 ml of 2 mg/L phosphate solutions having different pH and the phosphate concentration was measured after 48 h of reaction. The desired pH in the reaction system was adjusted by 0.1 mol/L HCl and NaOH. In order to investigate the effect of phosphate adsorption by coexisting ions, 50 ml of 2 mg/L phosphate solution containing certain ion concentrations of NaCl, Na 2 SO 4 , KCl and NaNO 3 was prepared, and 0.06 g /L FeAl-ESA@PAN was added and reacted for 48 hours. In the adsorption kinetics experiments, 0.06 g/L adsorbent was added to 100 mL of 2 mg/L phosphate solution and placed in a shaking chamber at 200 rpm/min for 48 h. The absorbance of the solution was measured by taking samples at certain time intervals. The data were fitted and analysed using quasi-primary kinetics (PFO) (3), quasi-secondary kinetics (PSO) (4) and Elovic's model (ELO) (5) as well as the intra-particle diffusion model (6), which have the following expressions: $$\:ln\left({q}_{e}\:-\:{q}_{t}\right)\:=ln{q}_{e}\:-\:{k}_{1}\text{t}$$ 3 $$\:\frac{t}{{q}_{t}}\:=\:\frac{1}{{k}_{2}{q}_{e}^{2}}\:+\:\frac{t}{{q}_{e}}$$ 4 $$\:{q}_{t}\:=\:\frac{ln\left(1\:+\:abt\right)}{b}$$ 5 $$\:{q}_{t}\:=\:{K}_{d}{t}^{1/2}\:+\:I$$ 6 where q e and q t denote the adsorption capacity (mg/g) at equilibrium and at time t, respectively, and k 1 and k 2 denote the adsorption rate constants for the quasi-primary and quasi-secondary kinetic models, respectively. a (mg/g·min) denotes the rate of adsorption, and b denotes the desorption parameter, which describes the activation energy and the degree of chemical adsorption, mainly. K d (cm/h) denotes the mass-transfer coefficient, I denotes the coefficient related to the thickness of the boundary layer. In the adsorption isothermal experiments, a series of phosphate solutions were prepared at concentrations ranging from 0–3 mg/L, 0.06 g/L of adsorbent was added, and finally the conical flasks were subjected to a shaking chamber at 298 K, 303 K, and 308 K, respectively, with the rotational speed being maintained at 200 rpm/min, and samples were taken after 48 h of adsorption for the measurement of the absorbance. The obtained data were fitted with Langmuir (7), Freundlich (9), and Temkin (10) isothermal models, respectively, and the separation coefficients, R L (8), were calculated using another expression of Langmuir, which are given below: $$\:\frac{{C}_{e}}{{q}_{e}}\:=\:\frac{1}{{q}_{m}{K}_{L}}\:+\:\frac{{C}_{e}}{{q}_{m}}$$ 7 $$\:{R}_{L}\:=\:\frac{1}{1\:+\:{K}_{L}{C}_{0}}$$ 8 $$\:log{q}_{e}\:=\:log{C}_{e}/\text{n}\:+log{K}_{F}$$ 9 $$\:{q}_{e}\:=\:{K}_{T}ln{C}_{e}\:+\:{K}_{T}lnf$$ 10 Where q m (mg/g) denotes the maximum adsorption capacity of the adsorbent for monolayer adsorption, K L denotes Langmuir affinity parameter, R L denotes the separation factor, which can be used to assess the desirability of adsorption, if the R L value is 1, the adsorption process is considered unfavourable, if the R L value is between 0 and 1, the adsorption process is considered favourable, and it can occur spontaneously, and if the R L value is 0, it means that the adsorption is irreversible. K F and n denote the Freundlich parameters of adsorption amount and adsorption strength. K T and f denote the Temkin parameters related to heat of adsorption and binding energy. The desorption experiments were carried out by eluting phosphate from the adsorbent using 10 mmol/L aluminium sulphate as the eluent, and after 4 h, the residual aluminium sulphate solution was washed off by passing 100 mL of deionized water and the regenerated adsorbent was used for the recycle test, which was carried out for six times. 3. Results 3.1. Characterisation of FeAl-ESA@PAN structure The crystal species of FeAl-ESA@PAN were firstly analysed by XRD technique and the results are shown in Fig. 1 A. The spectra of the FeAl-ESA@PAN structure at 2θ = 19°, 32°, 37°, 39°, 45°, 50°, 56°, 60°, 66°, 71°, and 78° are in good agreement with the absorption peaks of JCSD 00-011-0517 (Al 2 O 3 ), corresponding to (111), (220), (311), (222), (400), (331), (422), (511), (440), (531), and (538) planes, respectively, suggesting that aluminium is fully oxidised to cubic γ-Al 2 O 3 during spark ablation, and that the formation of this peak is attributed to the inhibition of α-Al 2 O 3 production by the rapid cooling of the spark discharge (Kang et al., 2023 ). And the diffraction peaks at 2θ = 19°, 31°, 37°, 45°, 56°, 59°, and 66° correspond to (111), (220), (311), (400), (422), (511), and (440) planes, respectively, which correspond well to JCSD 00-039-0238 (Fe 2 O 3 ), confirming the presence of a hexagonal crystalline system of the material, γ-Fe 2 O 3 (Zhao et al., 2023 ). Secondly, the N 2 adsorption-desorption isotherms and the corresponding pore size distributions of FeAl-ESA@PAN were obtained by BET characterisation (Fig. 1 B), and the isotherms conform to the type-IV isothermal curves according to the classification of the International Union of Pure and Applied Chemistry (IUPAC), with the presence of an obvious H3 hysteresis loops, which are thought to be slit pores formed by the stacking of lamellar particles. This indicates the presence of abundant mesoporous structure as well as a small amount of macroporous structure in the material. The adsorbent pore size distribution is relatively broad, but mainly concentrated in 4–8 nm, which is favorable for the adsorption of phosphate by the material (Roy, 2021 ). In addition, the specific surface area and pore volume of the material were 123.553 m 2 /g and 0.308 cm 3 /g, respectively. Finally, the SEM image (Fig. 2 A) shows that the composite membrane consists of numerous nanofibres with uniform diameter and rough surface of the nanofibres, and there are many nanopores, which helps to increase the exposure of the active sites of the metal oxides. The EDS analysis (Fig. 2 B-F) shows that the adsorbent mainly consists of Fe, Al, and O, with the contents of 33.91%, 28.6%, and 37.49%, respectively. The contents of Fe and Al are similar and the elemental mapping shows that the two elements are mixed and evenly distributed. As a result, the metal electrodes have been successfully oxidised and uniformly distributed after spark ablation. 3.2. Adsorption properties of FeAl-ESA@PAN 3.2.1. Adsorption isotherms The isothermal profile relationship between FeAl-ESA@PAN and phosphate was explored for the phosphate concentration range of 0–3 mg/L, (Fig. 3 D). The adsorption capacity did not change significantly with the increase of temperature, indicating that the material is more stable at three temperatures, in which the maximum adsorption capacity occurred at 303 K and reached 203.022 mg/g, then it predicts that FeAl-ESA@PAN has a very good prospect for phosphate removal. However, its adsorption capacity increased with the increase of the initial concentration of phosphate, which was attributed to the fact that the increase of the initial concentration increased the concentration gradient of phosphate on the surface of the adsorbent and in solution, which forced the phosphate to move to a lower concentration, and increased the chances of collision between the phosphate and the active sites on the adsorbent, thus promoting the adsorption process. In order to determine the equilibrium distribution of phosphate between the liquid phase and the solid phase (FeAl-ESA@PAN surface) during the adsorption process, the Langmuir model, the Freundlich model, and the Temkin model were fitted, and the results of the fitting are shown in Fig. 3 A-C. The results show that the Freundlich model is more consistent with the adsorption process of phosphate on FeAl-ESA@PAN than the other models at all three temperatures, which suggests a multilayer distribution of phosphate on FeAl-ESA@PAN (Ma et al., 2021 ). In addition the R L values are all less than 1, which also indicates that the adsorption process is spontaneous. 3.2.2. Adsorption kinetics For the adsorption kinetics of phosphate on FeAl-ESA@PAN, we used PFO, PSO and ELO models for further fitting analysis and the results are shown in Fig. 3 E. The PFO, PSO and ELO models are able to describe the adsorption process very well, as the R 2 reaches more than 0.9. Among them, the ELO model is the one that better describes the experimental data, which suggests that the energy on the FeAl-ESA@PAN surface is non-homogeneous and is dominated by metal ion-pollutant interactions (Chu et al., 2023 ). Compared to the PFO model, the PSO model has a higher fitting coefficient, which confirms the formation of stable chemical bonds between phosphate and adsorbent, such as chelate formation or ion exchange (Kaur et al., 2024 ). Furthermore, the adsorption process was clarified in detail using the intra-particle diffusion model (Fig. 3 E inset), and it is clear that the whole adsorption process is divided into three main phases. From 0 min to 5 min is the rapid adsorption phase, in which the active sites on the adsorbent are still sufficient and phosphate rapidly occupies the active sites on the adsorbent surface, leading to a faster adsorption process. During the period from 5 min to 720 min phosphate starts to diffuse from the surface of the adsorbent to the active sites inside the adsorbent, at this time the phosphate is repulsed by the phosphate adsorbed on the surface which makes the diffusion inside the particles slow, and finally equilibrium is reached due to the scarcity of phosphate in the solution as well as the limited number of adsorption sites of FeAl-ESA@PAN. In addition, the I value is not zero and none of the three stages passes through the origin, which suggests that the adsorption process may also be affected by diffusion through the liquid film in addition to intra-particle diffusion. 3.2.3. pH The pH of the solution strongly affects the surface charge of FeAl-ESA@PAN as well as the charge behaviour of phosphate, so it is necessary to study the effect of pH on the adsorption behaviour. The relevant acid-base equilibrium constants for phosphate in the measured pH range include pKa1 = 2.15, pKa2 = 7.2, and pKa3 = 12.35. When pKa1 < pH < pKa2, phosphate exists mainly as H 2 PO 4 − , whereas when pKa2 < pH < pKa3, it exists mainly as HPO 4 2− . Figure 4 A clearly shows that phosphate removal is higher at pH 5–8. Looking at the overall Fig. 4 B, the equilibrium zata potential is clearly smaller than the initial zata potential value, confirming that there is an electrostatic gravitational force in the adsorption process making the potential change. However, the smaller zata potential but higher phosphate removal at pH between 5–8 may be attributed to the ligand exchange between iron and aluminium oxides over phosphate and the formation of hydrogen bonding between P-OH of HPO 4 2− and M-OH (Liu et al., 2023 ). Whereas Fe 3+ hydrolysis under neutral conditions produces Fe(OH) 3 colloids, which can also immobilise a portion of phosphate by surface precipitation (Negm et al., 2025 ). 3.2.4. Co-existing ions Actual waters contain a wide variety of ions and the most important step in the application of FeAl-ESA@PAN in practice is to understand the effect of various ions on it. The results are shown in Fig. 4 C. It can be seen that cations have less influence on the adsorption efficiency of FeAl-ESA@PAN compared to anions. Among the anions, Cl − and SO 4 2− do not have much effect on the adsorption of phosphate, and SO 4 2− has a higher charge density, but it is easy to form inner complexes with Fe 3+ (e.g., FeSO 4 + ) (Cao et al., 2022 ), and may increase the adsorption sites through surface modification instead. The adsorption sites may instead be increased by surface modification, which exhibits “low competition” characteristics. However, the presence of CO 3 2− and HCO 3 − largely inhibits phosphate adsorption due to the strong competition between the high charge densities and PO 4 3− , which preferentially occupies the ligand-active sites of FeAl-ESA@PAN. The anions surround the positively charged adsorbent active site and the adsorbent double electron layer is compressed, leading to a weakening of the electrostatic adsorption between the adsorbent and phosphate, which further suggests that electrostatic adsorption is also involved in the adsorption process of phosphate by FeAl-ESA@PAN (He et al., 2024 ). In freshwater lakes, the ions with the highest concentrations are Ca 2+ (60–80% of total cations) and HCO 3 − (70–90% of total anions). Since NaCl is abundantly present in natural waters and does not greatly affect the adsorption process, the effects of Ca 2+ and HCO 3 − ion concentrations on the adsorption process were investigated by using different salts composed of Na + and Cl − , respectively. In the ion concentration experiment (Fig. 4 D), the phosphate removal rate basically did not change much with the increase of Ca 2+ ion concentration, and it can be seen that the effect of Ca 2+ ion concentration on the adsorption process is small. Similarly, there was a small decrease in the phosphate removal rate with increasing HCO 3 − ion concentration, but overall, the removal rate did not change much. Therefore it is surmised that the ion concentration has a small effect on the adsorption process of phosphate and it is the ion type (Du et al., 2022 ) that really plays an influential role. 3.2.5 Regeneration performance The reusability of adsorbent is very important for the application of adsorbent in real environment. In this study, aluminium sulphate was used as an eluent to elute phosphate from FeAl-ESA@PAN, and the regenerated adsorbent was used for cyclic tests. The experimental results are shown in Fig. 4 E. After repeating the test for six times, the phosphate removal efficiency of FeAl-ESA@PAN was maintained at more than 95%, which indicates that the adsorbent has good reusability. It was mainly due to the competitive binding of Al 3+ generated from the dissociation of aluminium sulphate with the Fe 3+ /Al 3+ active sites on the surface of FeAl-ESA. Phosphate (PO 4 3− ) binds to the metal sites via internal coordination, whereas Al 3+ preferentially occupies the adsorption sites due to its higher charge density, releasing PO 4 3− via a coordination exchange reaction. The small pH of aluminium sulphate solution, H + protonates the hydroxyl groups on the surface of the adsorbent, weakening the electrostatic attraction with the negatively charged PO 4 3− (Guo et al., 2018 ). And at low pH, PO 4 3− protonates to H 2 PO 4 − and its affinity with the adsorbent decreases. Secondly, the high ionic strength of aluminium sulphate compresses the bilayer to reduce the liquid film mass transfer resistance and [Al(H 2 O) 6 ] 3+ and H 2 PO 4 − form a soluble complex [Al(H 2 PO 4 )] 2+ , promoting the conversion of phosphate from the solid phase to the liquid phase. 3.2.6 Stability One of the most important steps in the application of adsorbents in the real environment is to assess the stability of the adsorbent. Therefore, ICP-OES was used to determine the concentration of metal ions in the system after 48 h of adsorption on FeAl-ESA@PAN series composite membranes, and the metal ion leaching rate was calculated. Figure 4 F demonstrates the leaching rates of various metal ions for FeAl-ESA and FeAl-ESA@PAN series composite membranes. It is obvious that the leaching rate of Al ions after FeAl-ESA was composited in PAN was not significant except for the FeAl-ESA@PAN (1) system, which showed a small increase, and these differences were even negligible. The leaching rate of Fe ions was reduced very significantly after compositing, which indicates that the PAN effectively suppressed the leaching of Fe and Al ions. In the FeAl-ESA@PAN series of composite membranes, the leaching rate of Al ions ranged from 0.06–0.24% and that of Fe ions ranged from 0.09–0.24%. The lowest leaching rate of the two ions is in the FeAl-ESA@PAN (0) system, which is mainly due to its lack of PVP doping resulting in FeAl-ESA being encapsulated by PAN, which is not easy to come into contact with the outside world. However, the leaching rates of metal ions are all low, and the FeAl-ESA@PAN (1) system is the optimal combination considering the adsorption performance. 3.3. Adsorption mechanism The chemical bonds and functional groups of FeAl-ESA@PAN were analysed by FTIR. As shown in Fig. 5 A, the presence of a distinct broad peak at wave number 3423 cm − 1 and a sharp peak at 1625 cm − 1 jointly confirm the presence of abundant hydroxyl groups and adsorbed water molecules on the surface of the material. The strong absorption peak at 1384 cm − 1 corresponds to a bridging hydroxyl vibration, so it is assumed that the oxides in FeAl-ESA@PAN form a multinuclear complex through the action of hydroxyl bridges. The absorption peak at 653 cm − 1 belongs to the characteristic peak of Al-O, and the superposition effect of the Fe-O vibrational modes produces a synergistic response in the same wave number interval, so a peak appears in the table. It can be seen that after the adsorption of phosphate on FeAl-ESA@PAN, a new absorption peak at 1078 cm − 1 appears, which is attributed to the telescopic vibration of P-O in the H 2 PO 4 − or HPO 4 2− groups (Fu et al., 2018 ). This result confirms that phosphate has been successfully adsorbed onto FeAl-ESA@PAN. In addition, the disappearance of the characteristic peak at 1384 cm − 1 and the significant weakening of the characteristic peaks at 3423 cm − 1 and 653 cm − 1 may be attributed to the exchange of hydroxyl groups on the surface with phosphate to form the M-O-P ligand bonding, which suggests that hydroxyl groups on FeAl-ESA@PAN are involved in the adsorption process. The microstructures and elemental compositions of FeAl-ESA@PAN after phosphate adsorption were tested (Fig. 5 B-F), and the results showed that the distribution of phosphate was highly overlapped with that of Al, Fe, and O, which further indicated that the iron and aluminium oxides in FeAl-ESA@PAN played a key role in the adsorption of phosphate. The characteristics of FeAl-ESA@PAN binding to phosphate were further analysed using XPS, and the two curves shown in Fig. 6 A represent the full XPS spectra before and after the adsorption of FeAl-ESA with phosphate, respectively, and it is clear that the characteristic peaks of P2p appeared after adsorption, and Fig. 6 F shows the fine spectra of P2p, which matches with HPO 4 2− and H 2 PO 4 − (Qu et al., 2020 ), which both confirm that the that phosphate was successfully adsorbed onto the surface of FeAl-ESA@PAN, which is consistent with the FTIR analysis. Figure 6 C shows that the two peaks representing M = O (530.26 eV) and M-OH (531.27 eV) in the fine spectrum of O1s before adsorption are significantly reduced in area after adsorption, which suggests that metal oxides, as well as hydroxyl groups, are involved in the adsorption process in FeAl-ESA@PAN. In Fig. 6 D-E, the peaks representing Al 3+ , and Fe 3+ are shifted to higher peak positions after adsorption, and the density of the electron cloud around them decreases, which is mainly due to the complexation reaction between the metal ions and phosphates (Yang et al., 2022 ). Therefore, in combination with the fact that FeAl-ESA@PAN has more electron-rich groups, we believe that the adsorption process occurs electrostatic adsorption, hydrogen bonding, complexation, and ion exchange . 3.4. Practical applications Considering that the leakage of metal ions into the environment may lead to secondary pollution, FeAl-ESA@PAN (1), which has advantages in both adsorption capacity and stability, was chosen for this test in the application of real water bodies. In this experiment, 1L of lake water from Qilu Lake (102°48′53″E, 24°12′13″N) in Yuxi City, Yunnan Province was taken, and its specific water quality indexes are shown in Table 1 ,. Then 2, 4, 6, 8 and 10 g/L of the composite membrane (FeAl-ESA@PAN (1)) were weighed and added into a 100 mL brown conical flask, and then 50 mL of the corresponding lake water was added, and the conical flasks were placed in the oscillation chamber at 200 rpm/min for 48 h. After 48 h of adsorption at room temperature, the sample solution was removed and filtered to measure the absorbance value, and the corresponding adsorption capacity and removal efficiency were calculated, and the results are shown in Fig. 7 . The effect of FeAl-ESA@PAN (1) dosage on the removal of phosphate from natural waters is shown in Fig. 7 , where the removal efficiency of the adsorbent increased from 71.66–94.01% and the adsorption capacity decreased from 42.99 mg/g to 11.43 mg/g as the adsorbent dosage was increased.The adsorption efficiency at a dosage of 3 g/L was 91.66%, which is consistent with the FeAl-ESA@PAN (1) was 91.66% at the dosage of 3 g/L, which was comparable to the adsorption efficiency of FeAl-ESA@PAN (1) for phosphate treatment in ultrapure water (97.78%), which indicated that the adsorption performance of FeAl-ESA@PAN (1) was stable in both natural and ultrapure water bodies. The practical application of the adsorbent needs to consider the economic cost and the efficiency of adsorption, therefore, the optimum dosage is 6 g/L for treating phosphate in natural water. Table 1 Summary of lake water quality indicators TP (mg/L) SRP (mg/L) TN (mg/L) DTN (mg/L) NH 4 + -N (mg/L) Chl-a (mg/L) pH (mg/L) 0.186 0.006 2.12 0.884 0.522 40–50 9–10 4. Conclusion In the present study, an economic as well as environmentally friendly binary metal oxide composite film adsorbent was prepared by a combination of EDM ablation deposition method and electrostatic spinning technique, which effectively solved the problem of agglomeration and non-recyclability of nanoparticles, improved the practical applicability of nanometal oxide adsorbents and was used for the adsorption of phosphate in water bodies. The adsorption of phosphate by the prepared FeAl-ESA@PAN was investigated as the object of investigation, and the characterisation and analysis of FeAl-ESA@PAN was carried out, and the effects of pH, co-existing ions and other factors on its adsorption of phosphate were investigated, and then its adsorption kinetics and the characteristics of adsorption isothermal curves were analysed. Finally, the adsorption mechanism was obtained by characterising the FTIR, EDS and XPS plots before and after the adsorption of phosphate, indicating that electrostatic adsorption, hydrogen bonding, complexation and ion exchange are the main mechanisms for phosphate removal. In order to investigate the removal effect under natural water bodies, water samples from Qilu Lake in Yunnan Province were collected for testing, which confirmed the application potential of FeAl-ESA@PAN, and provided valuable references for the development of highly efficient and economical phosphorus adsorption materials to control eutrophication in lakes, rivers and other water bodies. Declarations Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution W. Z: Investigation, Methodology, Validation, Visualization, Writing-original draft. Z.S.: Data curation, Investigation, Methodology. Y.J.: Formal analysis, Methodology. H. Z.: Visualization. Jianan Yao: Validation.Z. Y.: Validation. Y.Z.: Investigation.F. C.: Supervision, Project administration, Resources, Writing-review & editing. Acknowledgments This research was funded by the National Natural Science Foundation of China “Study on sedimentary processes and changes of heavy metal elements and nutrients in Lake Qilu over the past 200 years” (No. 42271170), Qilu Lake Field Scientiffc Observation and Research Station for Plateau Shallow Lake in Yunnan Province (No. 202505AW340011) and Safety assessment research and demonstration of Water ecosystem in Chenghai lake Under the influence of ecological water replenishment (No.202303AC100019). References Adil, S., Kim, J.-O., 2023. The effectiveness and adsorption mechanism of iron-carbon nanotube composites for removing phosphate from aqueous environments. Chemosphere 313, 137629. http://dx.doi.org/10.1016/j.chemosphere.2022.137629. Cao, S.-Y., Xu, L., Fu, Q.-C., Jin, X., Shi, X., Jin, P.-K., 2022. Effectivity of multiphase Fenton-like system of iron reduction induced by bisphenol a authigenic photoelectron. 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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-7514055","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":513677858,"identity":"619cad9a-4f3f-418a-a2c2-4712c9975bf2","order_by":0,"name":"Wei Zhao","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Zhao","suffix":""},{"id":513677859,"identity":"49971c38-eaa2-47ed-b32c-156458b49454","order_by":1,"name":"Zhengyuan Shang","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Zhengyuan","middleName":"","lastName":"Shang","suffix":""},{"id":513677860,"identity":"fe701573-a5d1-4087-a949-c8953f9aa0d5","order_by":2,"name":"Yandun Jin","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Yandun","middleName":"","lastName":"Jin","suffix":""},{"id":513677861,"identity":"de3847a8-eb6f-42e7-964f-b72139d2e557","order_by":3,"name":"Huipeng Zhou","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Huipeng","middleName":"","lastName":"Zhou","suffix":""},{"id":513677862,"identity":"d93ddf16-32b4-47a7-9c5c-e75338634579","order_by":4,"name":"Jianan Yao","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Jianan","middleName":"","lastName":"Yao","suffix":""},{"id":513677863,"identity":"0d320af7-7f21-44ec-9544-fa77fc5cbaaf","order_by":5,"name":"Zhiyang Yang","email":"","orcid":"","institution":"Yunnan University","correspondingAuthor":false,"prefix":"","firstName":"Zhiyang","middleName":"","lastName":"Yang","suffix":""},{"id":513677864,"identity":"e163d332-806b-4a38-8cfb-93981aeb559b","order_by":6,"name":"Yanbo Zeng","email":"","orcid":"","institution":"Yunnan Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Yanbo","middleName":"","lastName":"Zeng","suffix":""},{"id":513677866,"identity":"e067a94f-930b-4ce3-a89d-2e445f068983","order_by":7,"name":"Fengqin Chang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA00lEQVRIiWNgGAWjYDACCRBhwyAH4bERrSWNwZh0LYkNRGvhn9387OGXBOv0Dbd7DBg+lB0GijQQsOTOMXNjmYT03A13zhgwzjh3GChyAL8WA4kEM2nJH4dzN9zIMWDmbTsMEiGkJf2btETC4XQDkJa/xGnJMZP8kHA4AayFkRgtEjdyyqQZEtINZ95IKzjYcy6dR+IGAS38M9K3Sf5IsJbnu5G88cGPMms5/hkEtIAAMw8DM4PCAQYGIGLgIaweCBh/ALXINxCldhSMglEwCkYiAAAFiELyezRLEwAAAABJRU5ErkJggg==","orcid":"","institution":"Yunnan University","correspondingAuthor":true,"prefix":"","firstName":"Fengqin","middleName":"","lastName":"Chang","suffix":""}],"badges":[],"createdAt":"2025-09-02 06:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7514055/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7514055/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s40710-026-00812-7","type":"published","date":"2026-01-26T15:59:20+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":91423935,"identity":"bb584616-85f5-44a7-8dc0-fd61f491abb8","added_by":"auto","created_at":"2025-09-16 10:50:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":242838,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffraction (XRD) pattern of adsorbent (A); N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms and pore distribution (B).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/918cfd6101b5f77251194fda.png"},{"id":91424722,"identity":"34d5ce71-07e7-4e67-abe7-8cab0342fa20","added_by":"auto","created_at":"2025-09-16 10:58:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":718114,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope images of FeAl-ESA@PAN (A); energy dispersive X-ray spectra (B); EDS elemental mapping (C, D, E and F).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/8d9e4ea429b9f6112096203c.png"},{"id":91424934,"identity":"2b7c6527-1d14-4040-b892-8de03b54596b","added_by":"auto","created_at":"2025-09-16 11:06:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":401255,"visible":true,"origin":"","legend":"\u003cp\u003eIsothermal curve models: Langmuir model (A) ; Freundlich model (B) ; Temkin model (C) . Effect of initial concentration on phosphate adsorption on FeAl-ESA@PAN (D) . Kinetic model of phosphate adsorption on FeAl-ESA@PAN (E) .\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/5932b659afd1005477559764.png"},{"id":91424724,"identity":"229cf163-0497-4e87-9b1b-13f52592f0f7","added_by":"auto","created_at":"2025-09-16 10:58:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":476640,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of initial pH(A) ; zeta potential(B) ; ion type(C) and ion concentration(D) on phosphate adsorption by FeAl-ESA@PAN ; cyclic properties of FeAl-ESA@PAN adsorbed phosphate (E) ; effect of PVP doping on metal leaching rate in FeAl-ESA@PAN/phosphate reaction system (F) .\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/ec53fa3efe6abb5b57bca092.png"},{"id":91423938,"identity":"46a06209-0157-433a-afae-889b87c50df3","added_by":"auto","created_at":"2025-09-16 10:50:18","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":675091,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR patterns of FeAl-ESA@PAN before and after adsorption (A) ; EDS analysis of FeAl-ESA@PAN (B, C, D, E and F) .\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/5a4ac36b5f8c84224e2fb285.png"},{"id":91424935,"identity":"3c58cff0-a436-472d-983a-8cffc22ea390","added_by":"auto","created_at":"2025-09-16 11:06:18","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":615616,"visible":true,"origin":"","legend":"\u003cp\u003eWide scan XPS of (A) FeAl-ESA@PAN and FeAl-ESA@PAN + P, (B) C1s, (C) O1s, (D) Al2p, (E) Fe2p and (F) P2p.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/3c8c48256d1bc13304176537.png"},{"id":91423943,"identity":"b1a0d1b5-248a-43d5-8550-2f89b6295eaa","added_by":"auto","created_at":"2025-09-16 10:50:18","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":109475,"visible":true,"origin":"","legend":"\u003cp\u003eFeAl-ESA@PAN (1) Effect of adsorbent amount on phosphate removal from natural waters.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/f8c516478f79ec2aeae248f1.png"},{"id":101691961,"identity":"b44edb03-caff-4b5b-963a-0cd8250805a7","added_by":"auto","created_at":"2026-02-02 16:16:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4039412,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/018ce581-08c2-4435-8a4a-5011a2a0123c.pdf"},{"id":91423936,"identity":"201b987a-d5f2-4824-9505-d3345ae2e38d","added_by":"auto","created_at":"2025-09-16 10:50:18","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":26804,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-7514055/v1/9b6190942fd8f91716e5f5c5.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Phosphorus removal performance of spark deposited iron and aluminium metal oxide nanoparticles on polyacrylonitrile membranes","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePhosphorus is the raw material for the synthesis of all living cells and is an essential nutrient for plant growth. However, excessive phosphorus in water bodies can cause deterioration of water quality by algal blooms, reduction of oxygen content in water and loss of biodiversity, which can damage the normal function of water bodies and threaten human health (Glibert, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). According to research, 80% of eutrophication is caused by excessive phosphorus input, so phosphorus is critical factor in controlling eutrophication (Wang et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Currently, there are many methods to remove phosphate from water bodies, including adsorption (Jin et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), bioremediation (Wang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), chemical precipitation (Yago et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) and membrane separation (Gao et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Among them, the adsorption method has the advantages of simple operation, no highly toxic by-products and recycling (Wang et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), especially in the treatment of low concentration phosphate wastewater. Based on this, the research and development of materials with excellent adsorption performance has become a trend.\u003c/p\u003e\u003cp\u003eMetal oxides are widely used in wastewater treatment due to their high adsorption activity, high adsorption capacity, and easy to be processed and modified (Ma et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Among them, aluminium-based materials represented by alumina have strong adsorption properties for phosphate in solution, and are a class of phosphate removers that have been thoroughly studied and practically applied (Huang et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). It is usually believed that the aluminium sites on the surface of activated alumina are first hydroxylated in solution, and with different solution pH, the solid surface non-specifically adsorbs H\u003csup\u003e+\u003c/sup\u003e or OH\u003csup\u003e\u0026minus;\u003c/sup\u003e, and the phosphate ions (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) in solution can be bound to the solid surface by both electrostatic gravitational force or ion exchange (Yin et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In order to improve the adsorption performance and lifetime of adsorbent materials, it is usually modified with magnetic media.Iron oxides are ubiquitous in natural soils and water bodies, and are inexpensive and biocompatible (Lal et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Adil et al. (2023) have successfully recovered phosphate from water by using iron-carbon nanotubes (Fe-CNTs). The adsorption capacity of Fe-CNTs is far superior to that of the pristine CNTs. Experimentally, Fe-CNTs have demonstrated a better adsorption capacity than pristine CNTs. Fe-CNT showed a phosphate removal efficiency 7 times higher than that of pristine CNT. Sun et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) obtained aluminium-iron biomodified biochar (AFBC) by dual modification of maize biochar with AlCl\u003csub\u003e3\u003c/sub\u003e and FeCl\u003csub\u003e3\u003c/sub\u003e, and achieved a total phosphorus removal rate of 90.97% in rural wastewater treatment.\u003c/p\u003e\u003cp\u003eHowever, the powdered metal oxides are not favourable for recycling and reuse, and in order to solve this problem, blending the metal oxides into the carrier is a good choice. The low-cost electrostatic spinning process is a very attractive technique, which produces nanofibrous membranes with high specific surface area, high porosity, high flux, etc (Wang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Wei et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The process anchors a large amount of metal oxides without altering the chemical properties of the metal oxides (Lee et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), which makes it a good candidate for immobilising the metal oxides. Polyacrylonitrile (PAN) is a common polymer material that has been used in nanotextiles, filtration and metal ion adsorption (HMTShirazi et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Thimmiah and Nallathambi, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In addition, PAN fibres are often used as matrix materials for adsorbents due to their ideal chemical resistance, thermal stability and low flammability (Karimzadeh et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Nasimi et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Based on these advantages, PAN was selected as the matrix material for electrostatic spinning in this study. For the choice of porogenic agent (Fakhry et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), this study focuses on polyvinylpyrrolidone (PVP), a water-soluble polymer mainly formed by the polymerisation of vinylpyrrolidone in water or isopropyl alcohol. Its key advantage is that it can be easily removed from nanofibres by heating and boiling (Pourmadadi et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). More importantly, even a trace amount of PVP residue improves the hydrophilicity and solubility of the composite film (HMTShirazi et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), which helps to facilitate the contact of the active sites with the phosphate molecules.\u003c/p\u003e\u003cp\u003eTherefore, in this thesis, polymetallic oxide adsorbents were prepared using spark ablation technique and combined with electrostatic spinning technique to immobilise the metal oxides on porous nanofibres to obtain polymetallic oxide composite membranes aimed at:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePrepare FeAl bimetallic oxide nanoparticles by spark ablation and immobilise them on modified polyacrylonitrile (PAN) membranes to prepare polymetallic oxide composite membranes.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eA series of adsorption experiments (pH, co-existing ions, adsorption isotherms, adsorption kinetics, regeneration performance and stability) were performed and the adsorption behaviour and adsorption performance were evaluated.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eCharacterisation was carried out to elucidate the adsorption behaviour and mechanism of FeAl-ESA@PAN for the removal of phosphorus from water.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eTest the phosphorus removal effect of FeAl-ESA@PAN in lake water bodies to provide new ideas for the management of eutrophication in lakes.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials and chemicals\u003c/h2\u003e\u003cp\u003eHydrochloric acid (HCl) and potassium dihydrogen phosphate (KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, \u0026ge; 99.5%) were purchased from Chengdu Cologne Chemical Co. Sodium hydroxide (NaOH) was purchased from Sinopharm Chemical Reagent Co Ltd (China). All reagents were analytically pure without further purification. Filters with a pore size of 0.22 \u0026micro;m supplied by Tianjin Pilot Test Equipment Co (China). The gas (2%O\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;98%N\u003csub\u003e2\u003c/sub\u003e) supplied by Kunming Hongfa Deli Gas Co (China). Nano aerosol sintering deposition system (VSP-G1) was supplied by Fosner (Shanghai) Scientific Instruments Co. The UV-Vis spectrophotometer (GENESYS 50) was supplied by Thermo Fisher (USA). Natural water samples were obtained from Qilu Lake, Yunnan Province, China, and were refrigerated.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. FeAl-ESA @PAN composite film preparation\u003c/h2\u003e\u003cp\u003eIn this study, FeAl-ESA nanoparticles were prepared by spark ablation technique. Firstly, the iron electrode was fixed at the cathode of the VSP and the aluminium electrode was fixed at the anode, and the working voltage and current were set to 1.36 KV and 10.4 mA, respectively. Subsequently, the power supply was turned on, the nitrogen-oxygen mixture was passed in (the flow rate of the gas stream was controlled to be 3 L/min), and the instrument was preheated for 2\u0026ndash;3 min before the ignition switch was pressed, and the spark was generated between the electrodes, and the electrode material evaporated under the ablation of the spark, and the small vapour cloud reacted with the room temperature of the The small vapour cloud reacts with the carrier gas at room temperature and condenses to form metal oxide nanoparticles. The nanoparticles were deposited on the pre-prepared mixed filter membrane with the direction of the carrier gas, and finally the nanoparticles on the filter membrane were collected to obtain FeAl-ESA.\u003c/p\u003e\u003cp\u003ePolyacrylonitrile (PAN) is a polymer with acrylonitrile as the smallest unit, which has the potential to be used in different scientific fields due to its plasticity, low cost and excellent wettability. Many scholars have been working on the preparation of hybrid nanofibres with special functionalities by adding some organic or inorganic components (e.g., nanoparticles). Therefore, in this study, certain amounts of metal oxides and PVP (pore maker) were added to the PAN spinning solution with a view to improving its adsorption characteristics for phosphate.\u003c/p\u003e\u003cp\u003eThe specific steps were as follows: first, 1 g of PAN, 10 mg of metal oxide nanoparticles, and a certain amount of PVP were dissolved in 10 mL of DMF mixed solution, where PVP (wt%) : PAN (wt%)\u0026thinsp;=\u0026thinsp;1:1, and then the mixed solution was stirred at 60\u0026deg;C for 2 h on a magnetic stirrer to fully dissolve and mix the spinning solution. Finally, the spinning solution was injected into a 10 mL syringe and spun at a flow rate of 1.2 ml/h at 25 kV. After the spinning was completed, the release paper loaded with nanofibres was removed and treated in hot water at 80\u0026deg;C for 24 h to wash away the PVP. After washing, freeze-drying was carried out for 48 h to finally obtain FeAl-ESA@PAN fibrous membranes.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Characterisation\u003c/h2\u003e\u003cp\u003eThe surface morphology of the adsorbents was analysed using a scanning electron microscope (SEM, Zeiss Sigma 300, Zeiss GmbH, Germany), and images of the surface morphology of the samples were taken at different magnifications. The specific surface area of the adsorbent was determined using the BET method (Quantachrome-EVO, Florida, USA).\u003c/p\u003e\u003cp\u003eThe identification of the crystalline phase species of the adsorbent was determined using X-ray diffraction (XRD, Rigaku Ultima IV, Rigaku Rigaku Co., Japan). X-ray photoelectron spectroscopy (XPS, EscaLab250Xi, Thermo Fisher Scientific, USA) was used to examine the elemental composition of the adsorbent surfaces before and after adsorption as well as changes in the chemical state under the following conditions: addition of surface-contaminated carbon C1s (284.80 eV) calibration of binding energies for all spectra, and use of an Al-Kα target (1486.6 eV, 72 W) to read the data. Fourier Transform Infrared Spectroscopy (FTIR) (Nicolet IS 50, Thermo Fisher Scientific) was used to determine changes in the wavelength range of 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Zeta potential analyser (SurPASS, Anton Paarl, Austria) was used to study its charge at different pH. Inductively coupled plasma mass spectrometer (ICP, Agilent 5110, Agilent Technologies Ltd., China) measured the residual amount of metal ions in the water after adsorption.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Adsorption experiments\u003c/h2\u003e\u003cp\u003ePotassium dihydrogen phosphate (KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e) was used to formulate simulated phosphorus-containing wastewater with different concentrations (in terms of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) in all the experiments. Specifically, 0.06 g /L of adsorbent and a certain amount of phosphorus-containing wastewater were accurately weighed in a 100 mL conical flask. The solution was continuously shaken at 200 rpm for 48 h at room temperature using a thermostatic shaking chamber to ensure that adsorption equilibrium was reached. The adsorbed solution was filtered by 0.22 \u0026micro;m microporous filter membrane, and the residual phosphorus concentration was determined by ammonium molybdate spectrophotometry (GB 11893-89). Each experiment was repeated three times to take the average value, and finally, the removal efficiency η (%) and adsorption capacity q\u003csub\u003ee\u003c/sub\u003e (mg/g) of the adsorbent on phosphate were calculated according to the equations (\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and (\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e):\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\eta\\:\\:=\\:\\frac{{C}_{0}\\:-\\:{C}_{e}}{{C}_{0}}\\:\\times\\:\\:100$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{q}_{e}\\:=\\:\\frac{\\left({C}_{0}\\:-\\:{C}_{e}\\right)V}{m}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere C\u003csub\u003e0\u003c/sub\u003e and C\u003csub\u003ee\u003c/sub\u003e (mg/L) denote the initial concentration of phosphate and the concentration after adsorption equilibrium; V (L) denotes the volume of phosphate solution; and m (g) denotes the mass of adsorbent added.\u003c/p\u003e\u003cp\u003eThe pH of the solution strongly affects the surface charge of FeAl-ESA@PAN as well as the charge behaviour of phosphate, so it is necessary to investigate the effect of pH on the adsorption behaviour. 0.06 g /L of adsorbent was put into 50 ml of 2 mg/L phosphate solutions having different pH and the phosphate concentration was measured after 48 h of reaction. The desired pH in the reaction system was adjusted by 0.1 mol/L HCl and NaOH. In order to investigate the effect of phosphate adsorption by coexisting ions, 50 ml of 2 mg/L phosphate solution containing certain ion concentrations of NaCl, Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, KCl and NaNO\u003csub\u003e3\u003c/sub\u003e was prepared, and 0.06 g /L FeAl-ESA@PAN was added and reacted for 48 hours.\u003c/p\u003e\u003cp\u003eIn the adsorption kinetics experiments, 0.06 g/L adsorbent was added to 100 mL of 2 mg/L phosphate solution and placed in a shaking chamber at 200 rpm/min for 48 h. The absorbance of the solution was measured by taking samples at certain time intervals. The data were fitted and analysed using quasi-primary kinetics (PFO) (3), quasi-secondary kinetics (PSO) (4) and Elovic's model (ELO) (5) as well as the intra-particle diffusion model (6), which have the following expressions:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:ln\\left({q}_{e}\\:-\\:{q}_{t}\\right)\\:=ln{q}_{e}\\:-\\:{k}_{1}\\text{t}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:\\frac{t}{{q}_{t}}\\:=\\:\\frac{1}{{k}_{2}{q}_{e}^{2}}\\:+\\:\\frac{t}{{q}_{e}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\:{q}_{t}\\:=\\:\\frac{ln\\left(1\\:+\\:abt\\right)}{b}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ6\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$\\:{q}_{t}\\:=\\:{K}_{d}{t}^{1/2}\\:+\\:I$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere q\u003csub\u003ee\u003c/sub\u003e and q\u003csub\u003et\u003c/sub\u003e denote the adsorption capacity (mg/g) at equilibrium and at time t, respectively, and k\u003csub\u003e1\u003c/sub\u003e and k\u003csub\u003e2\u003c/sub\u003e denote the adsorption rate constants for the quasi-primary and quasi-secondary kinetic models, respectively. a (mg/g\u0026middot;min) denotes the rate of adsorption, and b denotes the desorption parameter, which describes the activation energy and the degree of chemical adsorption, mainly. K\u003csub\u003ed\u003c/sub\u003e (cm/h) denotes the mass-transfer coefficient, I denotes the coefficient related to the thickness of the boundary layer.\u003c/p\u003e\u003cp\u003eIn the adsorption isothermal experiments, a series of phosphate solutions were prepared at concentrations ranging from 0\u0026ndash;3 mg/L, 0.06 g/L of adsorbent was added, and finally the conical flasks were subjected to a shaking chamber at 298 K, 303 K, and 308 K, respectively, with the rotational speed being maintained at 200 rpm/min, and samples were taken after 48 h of adsorption for the measurement of the absorbance. The obtained data were fitted with Langmuir (7), Freundlich (9), and Temkin (10) isothermal models, respectively, and the separation coefficients, R\u003csub\u003eL\u003c/sub\u003e (8), were calculated using another expression of Langmuir, which are given below:\u003cdiv id=\"Equ7\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$\\:\\frac{{C}_{e}}{{q}_{e}}\\:=\\:\\frac{1}{{q}_{m}{K}_{L}}\\:+\\:\\frac{{C}_{e}}{{q}_{m}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ8\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$\\:{R}_{L}\\:=\\:\\frac{1}{1\\:+\\:{K}_{L}{C}_{0}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ9\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ9\" name=\"EquationSource\"\u003e\n$$\\:log{q}_{e}\\:=\\:log{C}_{e}/\\text{n}\\:+log{K}_{F}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ10\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ10\" name=\"EquationSource\"\u003e\n$$\\:{q}_{e}\\:=\\:{K}_{T}ln{C}_{e}\\:+\\:{K}_{T}lnf$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e10\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere q\u003csub\u003em\u003c/sub\u003e (mg/g) denotes the maximum adsorption capacity of the adsorbent for monolayer adsorption, K\u003csub\u003eL\u003c/sub\u003e denotes Langmuir affinity parameter, R\u003csub\u003eL\u003c/sub\u003e denotes the separation factor, which can be used to assess the desirability of adsorption, if the R\u003csub\u003eL\u003c/sub\u003e value is 1, the adsorption process is considered unfavourable, if the R\u003csub\u003eL\u003c/sub\u003e value is between 0 and 1, the adsorption process is considered favourable, and it can occur spontaneously, and if the R\u003csub\u003eL\u003c/sub\u003e value is 0, it means that the adsorption is irreversible. K\u003csub\u003eF\u003c/sub\u003e and n denote the Freundlich parameters of adsorption amount and adsorption strength. K\u003csub\u003eT\u003c/sub\u003e and f denote the Temkin parameters related to heat of adsorption and binding energy.\u003c/p\u003e\u003cp\u003eThe desorption experiments were carried out by eluting phosphate from the adsorbent using 10 mmol/L aluminium sulphate as the eluent, and after 4 h, the residual aluminium sulphate solution was washed off by passing 100 mL of deionized water and the regenerated adsorbent was used for the recycle test, which was carried out for six times.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Characterisation of FeAl-ESA@PAN structure\u003c/h2\u003e\u003cp\u003eThe crystal species of FeAl-ESA@PAN were firstly analysed by XRD technique and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA. The spectra of the FeAl-ESA@PAN structure at 2θ\u0026thinsp;=\u0026thinsp;19\u0026deg;, 32\u0026deg;, 37\u0026deg;, 39\u0026deg;, 45\u0026deg;, 50\u0026deg;, 56\u0026deg;, 60\u0026deg;, 66\u0026deg;, 71\u0026deg;, and 78\u0026deg; are in good agreement with the absorption peaks of JCSD 00-011-0517 (Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), corresponding to (111), (220), (311), (222), (400), (331), (422), (511), (440), (531), and (538) planes, respectively, suggesting that aluminium is fully oxidised to cubic γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e during spark ablation, and that the formation of this peak is attributed to the inhibition of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e production by the rapid cooling of the spark discharge (Kang et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). And the diffraction peaks at 2θ\u0026thinsp;=\u0026thinsp;19\u0026deg;, 31\u0026deg;, 37\u0026deg;, 45\u0026deg;, 56\u0026deg;, 59\u0026deg;, and 66\u0026deg; correspond to (111), (220), (311), (400), (422), (511), and (440) planes, respectively, which correspond well to JCSD 00-039-0238 (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), confirming the presence of a hexagonal crystalline system of the material, γ-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (Zhao et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSecondly, the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms and the corresponding pore size distributions of FeAl-ESA@PAN were obtained by BET characterisation (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB), and the isotherms conform to the type-IV isothermal curves according to the classification of the International Union of Pure and Applied Chemistry (IUPAC), with the presence of an obvious H3 hysteresis loops, which are thought to be slit pores formed by the stacking of lamellar particles. This indicates the presence of abundant mesoporous structure as well as a small amount of macroporous structure in the material. The adsorbent pore size distribution is relatively broad, but mainly concentrated in 4\u0026ndash;8 nm, which is favorable for the adsorption of phosphate by the material (Roy, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In addition, the specific surface area and pore volume of the material were 123.553 m\u003csup\u003e2\u003c/sup\u003e/g and 0.308 cm\u003csup\u003e3\u003c/sup\u003e/g, respectively.\u003c/p\u003e\u003cp\u003eFinally, the SEM image (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) shows that the composite membrane consists of numerous nanofibres with uniform diameter and rough surface of the nanofibres, and there are many nanopores, which helps to increase the exposure of the active sites of the metal oxides. The EDS analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB-F) shows that the adsorbent mainly consists of Fe, Al, and O, with the contents of 33.91%, 28.6%, and 37.49%, respectively. The contents of Fe and Al are similar and the elemental mapping shows that the two elements are mixed and evenly distributed. As a result, the metal electrodes have been successfully oxidised and uniformly distributed after spark ablation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Adsorption properties of FeAl-ESA@PAN\u003c/h2\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1. Adsorption isotherms\u003c/h2\u003e\u003cp\u003eThe isothermal profile relationship between FeAl-ESA@PAN and phosphate was explored for the phosphate concentration range of 0\u0026ndash;3 mg/L, (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD). The adsorption capacity did not change significantly with the increase of temperature, indicating that the material is more stable at three temperatures, in which the maximum adsorption capacity occurred at 303 K and reached 203.022 mg/g, then it predicts that FeAl-ESA@PAN has a very good prospect for phosphate removal. However, its adsorption capacity increased with the increase of the initial concentration of phosphate, which was attributed to the fact that the increase of the initial concentration increased the concentration gradient of phosphate on the surface of the adsorbent and in solution, which forced the phosphate to move to a lower concentration, and increased the chances of collision between the phosphate and the active sites on the adsorbent, thus promoting the adsorption process.\u003c/p\u003e\u003cp\u003eIn order to determine the equilibrium distribution of phosphate between the liquid phase and the solid phase (FeAl-ESA@PAN surface) during the adsorption process, the Langmuir model, the Freundlich model, and the Temkin model were fitted, and the results of the fitting are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-C. The results show that the Freundlich model is more consistent with the adsorption process of phosphate on FeAl-ESA@PAN than the other models at all three temperatures, which suggests a multilayer distribution of phosphate on FeAl-ESA@PAN (Ma et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In addition the R\u003csub\u003eL\u003c/sub\u003e values are all less than 1, which also indicates that the adsorption process is spontaneous.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2. Adsorption kinetics\u003c/h2\u003e\u003cp\u003eFor the adsorption kinetics of phosphate on FeAl-ESA@PAN, we used PFO, PSO and ELO models for further fitting analysis and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE. The PFO, PSO and ELO models are able to describe the adsorption process very well, as the R\u003csup\u003e2\u003c/sup\u003e reaches more than 0.9. Among them, the ELO model is the one that better describes the experimental data, which suggests that the energy on the FeAl-ESA@PAN surface is non-homogeneous and is dominated by metal ion-pollutant interactions (Chu et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Compared to the PFO model, the PSO model has a higher fitting coefficient, which confirms the formation of stable chemical bonds between phosphate and adsorbent, such as chelate formation or ion exchange (Kaur et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFurthermore, the adsorption process was clarified in detail using the intra-particle diffusion model (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE inset), and it is clear that the whole adsorption process is divided into three main phases. From 0 min to 5 min is the rapid adsorption phase, in which the active sites on the adsorbent are still sufficient and phosphate rapidly occupies the active sites on the adsorbent surface, leading to a faster adsorption process. During the period from 5 min to 720 min phosphate starts to diffuse from the surface of the adsorbent to the active sites inside the adsorbent, at this time the phosphate is repulsed by the phosphate adsorbed on the surface which makes the diffusion inside the particles slow, and finally equilibrium is reached due to the scarcity of phosphate in the solution as well as the limited number of adsorption sites of FeAl-ESA@PAN. In addition, the I value is not zero and none of the three stages passes through the origin, which suggests that the adsorption process may also be affected by diffusion through the liquid film in addition to intra-particle diffusion.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.2.3. pH\u003c/h2\u003e\u003cp\u003eThe pH of the solution strongly affects the surface charge of FeAl-ESA@PAN as well as the charge behaviour of phosphate, so it is necessary to study the effect of pH on the adsorption behaviour. The relevant acid-base equilibrium constants for phosphate in the measured pH range include pKa1\u0026thinsp;=\u0026thinsp;2.15, pKa2\u0026thinsp;=\u0026thinsp;7.2, and pKa3\u0026thinsp;=\u0026thinsp;12.35. When pKa1\u0026thinsp;\u0026lt;\u0026thinsp;pH\u0026thinsp;\u0026lt;\u0026thinsp;pKa2, phosphate exists mainly as H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, whereas when pKa2\u0026thinsp;\u0026lt;\u0026thinsp;pH\u0026thinsp;\u0026lt;\u0026thinsp;pKa3, it exists mainly as HPO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA clearly shows that phosphate removal is higher at pH 5\u0026ndash;8. Looking at the overall Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB, the equilibrium zata potential is clearly smaller than the initial zata potential value, confirming that there is an electrostatic gravitational force in the adsorption process making the potential change. However, the smaller zata potential but higher phosphate removal at pH between 5\u0026ndash;8 may be attributed to the ligand exchange between iron and aluminium oxides over phosphate and the formation of hydrogen bonding between P-OH of HPO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and M-OH (Liu et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Whereas Fe\u003csup\u003e3+\u003c/sup\u003e hydrolysis under neutral conditions produces Fe(OH)\u003csub\u003e3\u003c/sub\u003e colloids, which can also immobilise a portion of phosphate by surface precipitation (Negm et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\u003ch2\u003e3.2.4. Co-existing ions\u003c/h2\u003e\u003cp\u003eActual waters contain a wide variety of ions and the most important step in the application of FeAl-ESA@PAN in practice is to understand the effect of various ions on it. The results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC. It can be seen that cations have less influence on the adsorption efficiency of FeAl-ESA@PAN compared to anions. Among the anions, Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e do not have much effect on the adsorption of phosphate, and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e has a higher charge density, but it is easy to form inner complexes with Fe\u003csup\u003e3+\u003c/sup\u003e (e.g., FeSO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e) (Cao et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), and may increase the adsorption sites through surface modification instead. The adsorption sites may instead be increased by surface modification, which exhibits \u0026ldquo;low competition\u0026rdquo; characteristics. However, the presence of CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e largely inhibits phosphate adsorption due to the strong competition between the high charge densities and PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e, which preferentially occupies the ligand-active sites of FeAl-ESA@PAN. The anions surround the positively charged adsorbent active site and the adsorbent double electron layer is compressed, leading to a weakening of the electrostatic adsorption between the adsorbent and phosphate, which further suggests that electrostatic adsorption is also involved in the adsorption process of phosphate by FeAl-ESA@PAN (He et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn freshwater lakes, the ions with the highest concentrations are Ca\u003csup\u003e2+\u003c/sup\u003e (60\u0026ndash;80% of total cations) and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (70\u0026ndash;90% of total anions). Since NaCl is abundantly present in natural waters and does not greatly affect the adsorption process, the effects of Ca\u003csup\u003e2+\u003c/sup\u003e and HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e ion concentrations on the adsorption process were investigated by using different salts composed of Na\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, respectively. In the ion concentration experiment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD), the phosphate removal rate basically did not change much with the increase of Ca\u003csup\u003e2+\u003c/sup\u003e ion concentration, and it can be seen that the effect of Ca\u003csup\u003e2+\u003c/sup\u003e ion concentration on the adsorption process is small. Similarly, there was a small decrease in the phosphate removal rate with increasing HCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e ion concentration, but overall, the removal rate did not change much. Therefore it is surmised that the ion concentration has a small effect on the adsorption process of phosphate and it is the ion type (Du et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) that really plays an influential role.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.2.5 Regeneration performance\u003c/h2\u003e\u003cp\u003eThe reusability of adsorbent is very important for the application of adsorbent in real environment. In this study, aluminium sulphate was used as an eluent to elute phosphate from FeAl-ESA@PAN, and the regenerated adsorbent was used for cyclic tests. The experimental results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE. After repeating the test for six times, the phosphate removal efficiency of FeAl-ESA@PAN was maintained at more than 95%, which indicates that the adsorbent has good reusability. It was mainly due to the competitive binding of Al\u003csup\u003e3+\u003c/sup\u003e generated from the dissociation of aluminium sulphate with the Fe\u003csup\u003e3+\u003c/sup\u003e/Al\u003csup\u003e3+\u003c/sup\u003e active sites on the surface of FeAl-ESA. Phosphate (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e ) binds to the metal sites via internal coordination, whereas Al\u003csup\u003e3+\u003c/sup\u003e preferentially occupies the adsorption sites due to its higher charge density, releasing PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e via a coordination exchange reaction. The small pH of aluminium sulphate solution, H\u003csup\u003e+\u003c/sup\u003e protonates the hydroxyl groups on the surface of the adsorbent, weakening the electrostatic attraction with the negatively charged PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e (Guo et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). And at low pH, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e protonates to H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and its affinity with the adsorbent decreases. Secondly, the high ionic strength of aluminium sulphate compresses the bilayer to reduce the liquid film mass transfer resistance and [Al(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3+\u003c/sup\u003e and H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e form a soluble complex [Al(H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e)]\u003csup\u003e2+\u003c/sup\u003e, promoting the conversion of phosphate from the solid phase to the liquid phase.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.2.6 Stability\u003c/h2\u003e\u003cp\u003eOne of the most important steps in the application of adsorbents in the real environment is to assess the stability of the adsorbent. Therefore, ICP-OES was used to determine the concentration of metal ions in the system after 48 h of adsorption on FeAl-ESA@PAN series composite membranes, and the metal ion leaching rate was calculated. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF demonstrates the leaching rates of various metal ions for FeAl-ESA and FeAl-ESA@PAN series composite membranes. It is obvious that the leaching rate of Al ions after FeAl-ESA was composited in PAN was not significant except for the FeAl-ESA@PAN (1) system, which showed a small increase, and these differences were even negligible. The leaching rate of Fe ions was reduced very significantly after compositing, which indicates that the PAN effectively suppressed the leaching of Fe and Al ions. In the FeAl-ESA@PAN series of composite membranes, the leaching rate of Al ions ranged from 0.06\u0026ndash;0.24% and that of Fe ions ranged from 0.09\u0026ndash;0.24%. The lowest leaching rate of the two ions is in the FeAl-ESA@PAN (0) system, which is mainly due to its lack of PVP doping resulting in FeAl-ESA being encapsulated by PAN, which is not easy to come into contact with the outside world. However, the leaching rates of metal ions are all low, and the FeAl-ESA@PAN (1) system is the optimal combination considering the adsorption performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Adsorption mechanism\u003c/h2\u003e\u003cp\u003eThe chemical bonds and functional groups of FeAl-ESA@PAN were analysed by FTIR. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, the presence of a distinct broad peak at wave number 3423 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a sharp peak at 1625 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e jointly confirm the presence of abundant hydroxyl groups and adsorbed water molecules on the surface of the material. The strong absorption peak at 1384 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to a bridging hydroxyl vibration, so it is assumed that the oxides in FeAl-ESA@PAN form a multinuclear complex through the action of hydroxyl bridges. The absorption peak at 653 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e belongs to the characteristic peak of Al-O, and the superposition effect of the Fe-O vibrational modes produces a synergistic response in the same wave number interval, so a peak appears in the table. It can be seen that after the adsorption of phosphate on FeAl-ESA@PAN, a new absorption peak at 1078 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appears, which is attributed to the telescopic vibration of P-O in the H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e or HPO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e groups (Fu et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This result confirms that phosphate has been successfully adsorbed onto FeAl-ESA@PAN. In addition, the disappearance of the characteristic peak at 1384 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and the significant weakening of the characteristic peaks at 3423 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 653 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e may be attributed to the exchange of hydroxyl groups on the surface with phosphate to form the M-O-P ligand bonding, which suggests that hydroxyl groups on FeAl-ESA@PAN are involved in the adsorption process. The microstructures and elemental compositions of FeAl-ESA@PAN after phosphate adsorption were tested (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB-F), and the results showed that the distribution of phosphate was highly overlapped with that of Al, Fe, and O, which further indicated that the iron and aluminium oxides in FeAl-ESA@PAN played a key role in the adsorption of phosphate.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe characteristics of FeAl-ESA@PAN binding to phosphate were further analysed using XPS, and the two curves shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA represent the full XPS spectra before and after the adsorption of FeAl-ESA with phosphate, respectively, and it is clear that the characteristic peaks of P2p appeared after adsorption, and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eF shows the fine spectra of P2p, which matches with HPO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (Qu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), which both confirm that the that phosphate was successfully adsorbed onto the surface of FeAl-ESA@PAN, which is consistent with the FTIR analysis. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC shows that the two peaks representing M\u0026thinsp;=\u0026thinsp;O (530.26 eV) and M-OH (531.27 eV) in the fine spectrum of O1s before adsorption are significantly reduced in area after adsorption, which suggests that metal oxides, as well as hydroxyl groups, are involved in the adsorption process in FeAl-ESA@PAN. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eD-E, the peaks representing Al\u003csup\u003e3+\u003c/sup\u003e, and Fe\u003csup\u003e3+\u003c/sup\u003e are shifted to higher peak positions after adsorption, and the density of the electron cloud around them decreases, which is mainly due to the complexation reaction between the metal ions and phosphates (Yang et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTherefore, in combination with the fact that FeAl-ESA@PAN has more electron-rich groups, we believe that the adsorption process occurs electrostatic adsorption, hydrogen bonding, complexation, and ion exchange .\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Practical applications\u003c/h2\u003e\u003cp\u003eConsidering that the leakage of metal ions into the environment may lead to secondary pollution, FeAl-ESA@PAN (1), which has advantages in both adsorption capacity and stability, was chosen for this test in the application of real water bodies. In this experiment, 1L of lake water from Qilu Lake (102\u0026deg;48\u0026prime;53\u0026Prime;E, 24\u0026deg;12\u0026prime;13\u0026Prime;N) in Yuxi City, Yunnan Province was taken, and its specific water quality indexes are shown in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e,. Then 2, 4, 6, 8 and 10 g/L of the composite membrane (FeAl-ESA@PAN (1)) were weighed and added into a 100 mL brown conical flask, and then 50 mL of the corresponding lake water was added, and the conical flasks were placed in the oscillation chamber at 200 rpm/min for 48 h. After 48 h of adsorption at room temperature, the sample solution was removed and filtered to measure the absorbance value, and the corresponding adsorption capacity and removal efficiency were calculated, and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eThe effect of FeAl-ESA@PAN (1) dosage on the removal of phosphate from natural waters is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, where the removal efficiency of the adsorbent increased from 71.66\u0026ndash;94.01% and the adsorption capacity decreased from 42.99 mg/g to 11.43 mg/g as the adsorbent dosage was increased.The adsorption efficiency at a dosage of 3 g/L was 91.66%, which is consistent with the FeAl-ESA@PAN (1) was 91.66% at the dosage of 3 g/L, which was comparable to the adsorption efficiency of FeAl-ESA@PAN (1) for phosphate treatment in ultrapure water (97.78%), which indicated that the adsorption performance of FeAl-ESA@PAN (1) was stable in both natural and ultrapure water bodies. The practical application of the adsorbent needs to consider the economic cost and the efficiency of adsorption, therefore, the optimum dosage is 6 g/L for treating phosphate in natural water.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of lake water quality indicators\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTP\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSRP\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTN\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDTN\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eChl-a\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003epH\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.186\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.006\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.884\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.522\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e40\u0026ndash;50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9\u0026ndash;10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn the present study, an economic as well as environmentally friendly binary metal oxide composite film adsorbent was prepared by a combination of EDM ablation deposition method and electrostatic spinning technique, which effectively solved the problem of agglomeration and non-recyclability of nanoparticles, improved the practical applicability of nanometal oxide adsorbents and was used for the adsorption of phosphate in water bodies. The adsorption of phosphate by the prepared FeAl-ESA@PAN was investigated as the object of investigation, and the characterisation and analysis of FeAl-ESA@PAN was carried out, and the effects of pH, co-existing ions and other factors on its adsorption of phosphate were investigated, and then its adsorption kinetics and the characteristics of adsorption isothermal curves were analysed. Finally, the adsorption mechanism was obtained by characterising the FTIR, EDS and XPS plots before and after the adsorption of phosphate, indicating that electrostatic adsorption, hydrogen bonding, complexation and ion exchange are the main mechanisms for phosphate removal. In order to investigate the removal effect under natural water bodies, water samples from Qilu Lake in Yunnan Province were collected for testing, which confirmed the application potential of FeAl-ESA@PAN, and provided valuable references for the development of highly efficient and economical phosphorus adsorption materials to control eutrophication in lakes, rivers and other water bodies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflict of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eW. Z: Investigation, Methodology, Validation, Visualization, Writing-original draft. Z.S.: Data curation, Investigation, Methodology. Y.J.: Formal analysis, Methodology. H. Z.: Visualization. Jianan Yao: Validation.Z. Y.: Validation. Y.Z.: Investigation.F. C.: Supervision, Project administration, Resources, Writing-review \u0026amp; editing.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eThis research was funded by the National Natural Science Foundation of China \u0026ldquo;Study on sedimentary processes and changes of heavy metal elements and nutrients in Lake Qilu over the past 200 years\u0026rdquo; (No. 42271170), Qilu Lake Field Scientiffc Observation and Research Station for Plateau Shallow Lake in Yunnan Province (No. 202505AW340011) and Safety assessment research and demonstration of Water ecosystem in Chenghai lake Under the influence of ecological water replenishment (No.202303AC100019).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAdil, S., Kim, J.-O., 2023. The effectiveness and adsorption mechanism of iron-carbon nanotube composites for removing phosphate from aqueous environments. 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Porous electrospun fibers embedding TiO\u003csub\u003e2\u003c/sub\u003e for adsorption and photocatalytic degradation of water pollutants. Environmental science \u0026amp; technology 52, 4285-4293. http://dx.doi.org/10.1021/acs.est.7b06508.s001.\u003c/li\u003e\n\u003cli\u003eLiu, T., Wang, Y., Li, Y., 2023. How pH affects the oxygen reduction reactivity of Fe\u0026ndash;N\u0026ndash;C materials. ACS Catalysis 13, 1717-1725. http://dx.doi.org/10.1021/acscatal.2c05540.\u003c/li\u003e\n\u003cli\u003eMa, H., Zhang, W., Yang, K., Liu, Z., Zhang, W., 2025. Bimetallic MOF nanoparticles decorated on polyacrylonitrile-based electrospun nanofiber membranes for synergistic antibacterial activity and organic dye adsorption. Journal of Environmental Management 376, 124465. http://dx.doi.org/10.1016/j.jenvman.2025.124465.\u003c/li\u003e\n\u003cli\u003eMa, J., Ma, Y., Qian, X., Wang, Z., Chen, Y., Weng, L., Li, Y., 2021. Phosphorus adsorption onto ferrihydrite and predicting colloidal phosphorus transport. Chinese Journal of Eco-Agriculture 29, 85-93. http://dx.doi.org/10.13930/j.cnki.cjea.200461.\u003c/li\u003e\n\u003cli\u003eNasimi, S., Baghdadi, M., Dorosti, M., 2020. Surface functionalization of recycled polyacrylonitrile fibers with ethylenediamine for highly effective adsorption of Hg (II) from contaminated waters. Journal of Environmental Management 270, 110883. http://dx.doi.org/10.1016/j.jenvman.2020.110883.\u003c/li\u003e\n\u003cli\u003eNegm, N.A., Altalhi, A.A., Ahmed, H.M., Mohamed, E.A., 2025. Alginate modified Fe/Al-layered double hydroxide composite role in dual functionality remediation of malachite green dye in textile wastewater: adsorption, kinetic, and process mechanism. 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Adsorption mechanism of As\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e on metal oxides (CaO, \u0026gamma;-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e): a density functional theory study. Applied Surface Science 641, 158472. http://dx.doi.org/10.1016/j.apsusc.2023.158472.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-processes","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"enpr","sideBox":"Learn more about [Environmental Processes](https://www.springer.com/journal/40710)","snPcode":"40710","submissionUrl":"https://submission.nature.com/new-submission/40710/3","title":"Environmental Processes","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Phosphate uptake, iron-aluminum oxides, electrostatic spinning, Eutrophication","lastPublishedDoi":"10.21203/rs.3.rs-7514055/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7514055/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEutrophication of water bodies including lake and river is becoming increasingly serious, and controlling phosphate concentration in such water bodies is the key to solving the eutrophication problem. Adsorption technology provides a more practical solution for phosphate removal due to the advantages of easy operation, low cost, no highly toxic by-products and recyclability. Therefore, in this study, the adsorption method was used to adsorb phosphate from water bodies and the concentration of phosphate after adsorption was determined. Iron-aluminium oxide nanoparticles were prepared by electric spark ablation, and then iron and aluminium oxide composite nanoparticles were deposited on polyacrylonitrile (PAN) membranes using electrostatic spinning to obtain FeAl-ESA@PAN fibrous membranes for phosphorus removal from aqueous environments.\u003c/p\u003e\u003cp\u003eDue to the nano constraints of the fibre membrane, the problem of unfavorable recycling and reuse of metal oxides in powder form is effectively solved. It was modified by using magnetic medium Fe, which not only improved the adsorption performance and service life of the adsorbent material, but also reduced the production cost. The adsorption experiments showed that the adsorption capacity of FeAl-ESA@PAN for phosphate was 21.05 mg\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and the variables such as reaction time, pH and coexisting ions had a significant effect on the adsorption capacity. The influence of FeAl-ESA@PAN on phosphorus removal from lake water was investigated for Qilu Lake (Yunnan, China) as an example, and the total phosphorus removal rate observed was 94.01%, and a series of characterisations indicated that electrostatic adsorption, hydrogen bonding, complexation, and ion-exchange were the main mechanisms of phosphorus removal.\u003c/p\u003e","manuscriptTitle":"Phosphorus removal performance of spark deposited iron and aluminium metal oxide nanoparticles on polyacrylonitrile membranes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-16 10:50:14","doi":"10.21203/rs.3.rs-7514055/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-16T19:41:05+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-19T11:02:20+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-18T08:24:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"250606164062755572757350041025037033702","date":"2025-09-09T10:14:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"54929794905199110192144033785033586740","date":"2025-09-09T08:11:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"129563784239048912673886873519160374106","date":"2025-09-09T07:30:17+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-09T07:06:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-04T13:20:20+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-04T08:54:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Processes","date":"2025-09-02T06:29:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-processes","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"enpr","sideBox":"Learn more about [Environmental Processes](https://www.springer.com/journal/40710)","snPcode":"40710","submissionUrl":"https://submission.nature.com/new-submission/40710/3","title":"Environmental Processes","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2668c4cf-ec92-4621-a4df-392b86d65b26","owner":[],"postedDate":"September 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T16:13:21+00:00","versionOfRecord":{"articleIdentity":"rs-7514055","link":"https://doi.org/10.1007/s40710-026-00812-7","journal":{"identity":"environmental-processes","isVorOnly":false,"title":"Environmental Processes"},"publishedOn":"2026-01-26 15:59:20","publishedOnDateReadable":"January 26th, 2026"},"versionCreatedAt":"2025-09-16 10:50:14","video":"","vorDoi":"10.1007/s40710-026-00812-7","vorDoiUrl":"https://doi.org/10.1007/s40710-026-00812-7","workflowStages":[]},"version":"v1","identity":"rs-7514055","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7514055","identity":"rs-7514055","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}