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Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: The materials studied may be used in the radioactive waste vitrification process. Additionally, the proposed simulation method may be useful in optimizing glass composition and predicting the glass elements migration. Among the many possible applications of iron phosphate glasses, one of them is that they are promising materials in waste vitrification, particularly for radioactive waste. In vitrified form, waste elements should be permanently immobilized in a glass network as they are susceptible to harsh environmental conditions. The self-diffusion of the vitrified material species may limit the potential usefulness of the glasses. This paper presents the possibility of using molecular dynamics simulations to study this process and the substitution of SrO into an iron phosphate glass network. It was evidenced that the self-diffusion mechanism differed significantly depending on whether the glass was in a solid or liquid state. The proposed method also offered a relatively easy prediction of glass characteristic temperatures, such as transformation and flow. We also observed, and here describe, an aggregation process of the glass elements that may drive their crystallization. The obtained results are discussed in light of the experimental and theoretical structural feature literature data. [ABSTRACT FROM AUTHOR]

Iron phosphate (FePO4·2H2O) has emerged as the mainstream process for the synthesis of lithium iron phosphate (LiFePO4), whereas FePO4·2H2O produced by different processes also has a great influence on the performance of LiFePO4. In this paper, FePO4·2H2O was produced by two different processes, in which FeSO4 ferrous and Fe(NO3)3·9H2O ferric were used, respectively. After dehydration under the same conditions, a carbon-coated lithium iron phosphate (LiFePO4/C) cathode material was synthesized by a high-temperature solid phase method. The results demonstrated that FePO4·2H2O contained different impurities due to different raw materials, which led to different particle sizes, specific surface areas, microscopic morphology, and crystal structures. The difference of FePO4·2H2O eventually resulted in the difference of LiFePO4/C cathode materials in micro-morphology and crystal structure, which affected the electrochemical performance. Under the premise of comprehensively considering the cost and quality of FePO4·2H2O, improving the purity of FePO4·2H2O is an important method to improve the electrochemical performance of LiFePO4/C cathode materials. Simultaneously, it is also expected to provide theoretical guidance for the preparation of lower-cost and better-quality LiFePO4/C cathode materials. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recovery of iron phosphate from the leaching slag of used lithium iron phosphate cathode materials is a crucial step to achieve closed-loop recovery of lithium iron phosphate, which has not yet been effectively accomplished. In the study, ultrasonic-assisted sulfuric acid leaching was used to remove impurities in the iron phosphate, to meet the stringent impurity content requirements for battery-grade iron phosphate regarding impurity content. Optimization of leaching conditions involved a sulfuric acid concentration of 0.2 mol·L-1, acid-leaching time of 30 min, power of 50 W, and reaction temperature of 80℃. Under these conditions, the removal efficiencies of Cr, Cu, Ni, and Zn in iron phosphate were 26.09%, 83.0%, 75.9%, and 96.3%, respectively. Simultaneously, the content of impurity elements Cr and Zn concurred with the standard for battery-grade iron phosphate (HG/T 4701-2021), with both 50 ppm and 10 ppm contents. The leaching results indicated the effectiveness of ultrasound in enhancing the removal of impurity elements in iron phosphate within a sulfuric acid solution. Further analyses, including XRD, particle size, TEM, and XPS indicated that the surface of the iron phosphate particles cavitated after ultrasonic acid leaching, resulting in the formation of numerous pores. Additionally, particle collisions led to a reduction in particle size, with no generation of by-products during the process. This innovative approach not only contributed to the removal of impurity elements but also provided insights into the reuse of leaching slag (iron phosphate) and offered guidance for the recovery of metals from waste lithium iron phosphate cathode materials.

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Titanium white waste was used as the iron source to prepare LiFePO 4 cathode material. • The feasibility of whole process was verified by thermodynamic analysis. • The contents of impurities in the product were far below the standard. • The electrochemical performance of the synthesized LiFePO 4 was satisfactory. Large amounts of titanium white waste are generated in the production of titanium dioxide using sulphate method, which in turn can be used to prepare LiFePO 4 cathode material, thereby reducing environmental risks and achieving resource recovery. However, a key challenge lies in the elimination of impurities. In this work, a cost-efficient and straightforward approach based on phase transformation during hydrothermal treatment was proposed to utilize titanium white waste with calcium dihydrogen phosphate for the preparation of LiFePO 4 cathode material. The content of Fe in the leachate was enriched to 81.5 g/L after purification, while 99.9 % of Ti and 98.36 % of Al and were successfully removed. In the subsequent process for Fe/P mother liquor preparation, the losses of Fe and P were only 5.82 % and 2.81 %, respectively. The Fe and P contents of the synthesized FePO 4 product were 29.47 % and 17.08 %, respectively, and the Fe/P molar ratio was 0.986. Crystal phase of the product matched well with standard iron phosphate, and the lamellar microstructure of FePO 4 was uniform with the particle size ranging from 3 to 5 μm. Moreover, the contents of impurities in the product were far below the standard. The initial discharge of LiFePO 4 synthesized by the iron phosphate was 160.6 mAh.g−1 at 0.1C and maintained good reversible capacity after 100 cycles. This work may provide new strategy for preparing LiFePO 4 cathode material from industrial solid waste. [ABSTRACT FROM AUTHOR]

The precipitation method is an efficient, economically feasible, and reproducible synthetic route to cathode materials for lithium-ion batteries with attractive performance characteristics, in particular, lithium iron phosphate (LiFePO4). This paper reviews the mechanisms of the key steps of the synthesis, namely, precipitation of iron phosphate FePO4 followed by its sintering with a lithium-containing raw material to give the LiFePO4 phase. The most probable interactions determining the kinetics of the precipitation process are considered using the data on the dissociation degree of the reacting components. The influence of the nature and concentrations of the commonly used sources of iron (FeSO4, FeCl3, Fe(NO3)3) and phosphorus (H3PO4, NH4H2PO4, (NH4)2HPO4), as well as the precipitation conditions (pH, temperature) on the precipitation efficiency of FePO4 is analyzed. The effect of the nature of the lithium-containing raw material (LiOH, Li2CO3, LiNO3) and the sintering (calcination) temperature on the morphology, phase composition, and electrochemical properties of the resulting LiFePO4 is discussed. The possibility is considered of obtaining spherical particles with high bulk density, which provides high specific and volumetric energy density of electrochemical cells. Based on the relationships established, optimal parameters for the synthesis of LiFePO4 with preliminary FePO4 precipitation step are proposed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mining & Metallurgy. Section B: Metallurgy is the property of Journal of Mining & Metallurgy and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The potential shortage of mineral phosphorus (P) sources and the shift towards a circular economy motivates the introduction of new forms of P fertilizers in agriculture. However, the solubility of P in new fertilizers as well as their availability to plants may be low. In this experiment, we incubated an agricultural soil poor in P (28 mg P2O5 kg-1) for 63 days in the presence of a range of organic and inorganic poorly soluble P forms commonly found in new fertilizers: hydroxyapatite (P-Ca), iron phosphate (P-Fe), phytic acid (P-Org) and a combination of P-Ca and P-Org (P-Mix). Cellulose and potassium nitrate (KNO3) were added to stimulate microbial activity at the beginning of the incubation. We included a positive control with triple superphosphate (TSP) and negative controls with no P application (with and without cellulose and KNO3). We assessed the fate of the different poorly soluble P forms in NaHCO3 extracts (Olsen P) over time as a proxy for plant-available P. Soil microbial biomass, fungal to bacterial ratio, soil respiration, enzymatic activities (ß-glucosidase, arylamidase and acid and alkaline phosphatase), N mineralization and soil pH were also monitored. At the beginning of the incubation, TSP showed the highest Olsen P across all treatments and P-Fe showed higher levels of Olsen P than the other poorly soluble P forms (p < .05). During the incubation, the levels of Olsen P decreased over time for TSP (positive control). Contrastingly, Olsen P increased significantly over time for all the poorly soluble P forms and the negative controls, indicating an increase in plant-available P. Particularly, levels of Olsen P for the P-Org treatment roughly doubled (shifting from 16.5 mg kg-1 to 32.9 mg kg-1) over the whole incubation period. The rate of increase in Olsen P was positively correlated with microbial biomass C:P ratio (p < .01) for all poorly soluble treatments. The higher levels of Olsen P for the P-Org treatment were also explained by a positive correlation with fungal biomass. Our results show that poorly soluble forms of P may be made available to plants under the influence of the microbial community, with a stronger effect on organic P forms. [ABSTRACT FROM AUTHOR]

Among the many possible applications of iron phosphate glasses, one of them is that they are promising materials in waste vitrification, particularly for radioactive waste. In vitrified form, waste elements should be permanently immobilized in a glass network as they are susceptible to harsh environmental conditions. The self-diffusion of the vitrified material species may limit the potential usefulness of the glasses. This paper presents the possibility of using molecular dynamics simulations to study this process and the substitution of SrO into an iron phosphate glass network. It was evidenced that the self-diffusion mechanism differed significantly depending on whether the glass was in a solid or liquid state. The proposed method also offered a relatively easy prediction of glass characteristic temperatures, such as transformation and flow. We also observed, and here describe, an aggregation process of the glass elements that may drive their crystallization. The obtained results are discussed in light of the experimental and theoretical structural feature literature data.

In the current work, we report on the synthesizing of a series of novel nanocomposite materials obtained by functionalizing the SBA-15 silica matrix with anchored iron phosphonate molecules and the following thermal treatment. The obtained results reveal the formation of a unique amorphic layer of Fe-based compounds on the surface of silica walls of SBA-15 channels as a result of the organic groups' decomposition after moderate thermal treatment. Due to their unique structure, represented in an active Fe-containing amorphous coating spread over a large surface area, these materials are of great interest for their potential applications in fields such as catalysis, adsorption, and non-linear optics. The obtained materials remain amorphous, preserving the SBA-15 mesoporous structure up to temperatures of approximately 800 °C, after which the partial melting of the silica backbone is observed with the simultaneous formation of nanocrystals inside the newly-formed glassy mass. All obtained materials were characterized using such techniques as thermogravimetry, transmission and scanning electron microscopy combined with energy dispersive x-ray spectroscopy mapping, Raman spectroscopy, N2 sorption analysis, x-ray diffraction, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and SQUID measurements. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Battery grade iron phosphate was prepared through three processes of nitric acid dissolution, coprecipitation and calcination. In the first stage, iron phosphate slag was dissolved with strong oxidizing acid to obtain iron phosphate solution containing iron and phosphorus. In the second stage, the pH value of iron phosphate solution was adjusted by ammonia water to make the solution precipitate into iron phosphate. In the third stage, the final product anhydrous iron phosphate was obtained through calcination. The calcined products were evaluated by XRD, SEM, particle size distribution and molar ratio of iron to phosphorus. The process research shows that the best process conditions in the first stage are solid-liquid ratio 1∶12, nitric acid concentration 7.6 mol/L, dissolution time 5 h, dissolution temperature 90 ℃,under which the dissolution rate of ferrophosphorus slag is 96.39%. The optimum technological conditions in the second stage are the molar ratio of iron and phosphorus in the solution is 1∶1, the reaction temperature is 80 ℃, pH=1.0, time is 4 h, and the molar ratio of iron and phosphorus in the prepared FePO4 is 0.97. The optimum calcination temperature is 500 ℃,and qualified iron phosphate is prepared. [ABSTRACT FROM AUTHOR]

Iron phosphate@talc (IPT) sorbent was fabricated by precipitation method and utilized for 137Cs, 152+154Eu, and 131Ba sorption from aqueous media. Different analytical apparatuses such as XRD, FT-IR, SEM, and XRF were used to find the structure, morphology, and functional groups of IPT sorbent. Different parameters like shaking time, pH, temperature, and initial metal concentrations were studied. The obtained data reveal that the sorption of 137Cs, 152+154Eu, and 131Ba was pH, time-dependence, and kinetics following pseudo-2nd-order kinetics. The Langmuir and Freundlich equations were used as model isotherms. Thermodynamics parameters were calculated to prove that the sorption reaction was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

A highly organized hexagonal mesoporous iron phosphate framework structure with the designation HMI‐41 was successfully synthesized for the first‐time in a reproducible way using imidazolium‐based ionic liquid as structure directing agent. The unique templating properties of ionic liquid generated a highly ordered well‐crystallized mesoporous matrix having high surface area (445 m2 g−1), thicker pore wall (2.1 nm) and narrow pore size distribution (3.1 nm). The presence of active sites within a tetrahedral framework structure made the novel HMI‐41 catalyst highly effective for phenol hydroxylation in an acidic medium with hydrogen peroxide as the oxidant. The catalyst exhibited outstanding performance, achieving an impressive 80% hydroquinone selectivity and 21% phenol conversion with a hydroquinone‐to‐catechol ratio of seven, which is the highest value ever reported. [ABSTRACT FROM AUTHOR]

In view of the current situation wherein acid resources and valuable components in titanium dioxide waste acid cannot be effectively extracted and are prone to secondary pollution, our research team proposed a new technique consisting of step extraction and the comprehensive utilization of titanium dioxide waste acid. In this paper, the thermodynamics of selective precipitation and the preparation of doped iron phosphate from waste acid were studied. The thermodynamics results show that the content of Al3+, Mn2+, Mg2+, and Ca2+ in the reaction system can be tuned by adjusting the pH during the pre-precipitation process. In the first step, these impurity ions should be settled as much as possible; then, Fe2+ should be oxidized to Fe3+ so as to obtain iron phosphate with higher purity in the next step of the precipitation process. The effects of the reaction temperature, seed crystals, pH value, and P/M on the precipitation process were investigated in detail. The experimental results show that in the reduced state, the optimal precipitation conditions are a temperature of 75 °C, an initial pH value of 4.5, and an optimal P/M molar ratio of 1.1. In the oxidized state, the optimal precipitation conditions are a temperature of 60 °C, a solution pH = 2.5, and a reaction time of 25 min. After calcination, the precipitate mainly consists of iron phosphate, which basically meets the requirements of an iron phosphate precursor. [ABSTRACT FROM AUTHOR]

The purilication and reuse ol titanium dioxide by-product lerrous sullate are ol great signilicance lor improving the added value ol the iron-containing products and the comprehensive utilization of resources. The removal ol manganese and the reuse of iron in titanium dioxide by-product lerrous sullate were studied. The leasibility ol oxidizing Fe2+ to Fe'十 by hydrogen peroxide and oxidizing Mn2+ to Mn02 by potassium permanganate was theoretically analyzed. The effects ol oxidant dosage, pH value ol the solution and reaction time on the removal rate ol manganese were investigated. The experimental results show that the manganese removal rate could reach 99. 9% under the conditions ol KMnO4 dosage 1. 0 times ol the theoretical value, pH value ol 1. 20 and oxide reaction time lor 30 min. The manganese content in the purified ferric sullate solution was reduced to 0. 28 mg/L alter manganese removal treatment The purified solution was used as the iron source to synthesize iron phosphate by liquid-phase precipitation method, and the nanoscale high-purity amorphous iron phosphate dihydrate precursor was obtained, which can be transformed into a-quartz-type iron phosphate alter calcination. [ABSTRACT FROM AUTHOR]

LiFePO4 is a type of cathode material with good safety and long service life. However, the problems of the low Li ion diffusion rate and low electron conductivity limit the application of LiFePO4 in the field of electric vehicles. In this paper, FePO4 with different grain sizes was prepared via the air oxidation precipitation method and then sintered to prepare LiFePO4. The refined grain can shorten the diffusion distance of Li+, accelerate the diffusion of Li+, and improve the diffusion coefficient of Li+. The results show that LiFePO4 with a smaller grain size has better electrochemical performance. The discharge capacity of the first cycle is 151.3 mAh g−1 at 1 C, and the capacity retention rate is 95.04% after 230 cycles. Its rate performance is more outstanding, not only at 0.2 C, where the discharge capacity is as high as 155 mAh g−1, but also at 10 C, the capacity fade is less, and it can still reach 131 mAh g−1. The air oxidation precipitation method reduces the production cost, shortens the production process, and prepares FePO4 with small grains, which provides a reference for further improving the properties of precursors and LiFePO4. [ABSTRACT FROM AUTHOR]

Sulfuric acid method is a critical method to prepare rutile and anatase titanium dioxide. In the preparation process, acid leaching is accompanied by a large amount of iron-containing solid waste, represented by ferrous sulfate waste. If these solid wastes are stored directly without proper treatment, they will cause massive environmental damage and a lot of iron resources waste. The impurity removal and high added value utilization of ferrous sulfate had been studied deeply. Based on those studies, separation impurities from ferrous sulfate waste with various phosphate radical precipitation separation method was further explored. And a new process of preparing iron phosphate (FePO4) electrode material by liquid phase precipitation method was proposed to recover Fe from solid waste. Results showed that recovery of Fe in solid waste achieved 92%; moreover, removal rates of Ti, Mg, and Mn are higher than 95.3%, 78.4%, and 89.2%, respectively. The prepared iron phosphate reached the industrial battery grade (HG/T 4701-2014) standard by liquid phase reaction. The process realized efficient recovery of iron from solid waste and high value-added utilization of iron-containing solid waste. [ABSTRACT FROM AUTHOR]

Abstract Purpose There is a need to develop agricultural practices that mobilize sparingly soluble soil phosphorus (P) due to increasing scarcity of P fertilizer. Interactions of different plant species in the rhizosphere might increase P mobilization, but the underlying mechanisms are still not fully understood. Methods We conducted a pilot study with four plant species (maize, soy, lupin, mustard) grown alone and in combination with maize (intercropping) to investigate how species interact to mobilize P from iron phosphate (FePO4). Root exudates of individual plants were collected and analyzed for low molecular weight organic acid anions (LMWOA) and pH. Results Maize increased its exudation of LMWOA and its biomass P concentration in intercropping, especially when grown together with lupin. This is the first study to show unequivocally that a high LMWOA concentration in the rhizosphere in intercropping is not only caused by high LMWOA release of the companion but also by an increased LMWOA exudation of the main crop. The high release of LMWOA was associated with a higher maize P concentration, indicating that enhanced LMWOA release in intercropping is beneficial for P acquisition of maize. Moreover, lupin and mustard mobilized more P from FePO4 than maize and soy likely through high LMWOA exudation (lupin) and rhizosphere alkalinization (mustard). Conclusion Taken together, we reveal that intercropping with lupin increases the release of LMWOA by maize and concurrently the maize P concentration, suggesting that intercropping is useful for the mobilization of P from FePO4 because it affects the exudation of maize.

[Display omitted] The high binding affinity of iron(oxyhydr)oxides for phosphate has recently been used in medicine to treat hyperphosphatemia, an abnormally elevated phosphate concentration in the blood. For iron(oxyhydr)oxide nanoparticles, the composition of the organic shell has a more significant influence on their interaction with phosphate than is often assumed. This study shows different mechanisms in phosphate binding, using the example of two similar new phosphate-binding agents. We characterized the phosphate-binding behavior of two iron(oxyhydr)oxide-based nanomaterials with similar composition and particle properties and investigated their binding mechanisms by spectroscopic methods. For the often prescribed Velphoro, we demonstrated a phosphate binding capacity of>210 mg/g. A similar active ingredient named C–PAM binds over 573 mg/g. Spectroscopic measurements highlighted differences in the binding mechanism. While Velphoro binds phosphate via surface complexation independent of pH and adsorbent concentration, C–PAM shows a strong concentration dependence. At low concentrations, phosphate is bound via complexation reactions. The iron(oxyhydr)oxide structure was dissolved at higher phosphate concentrations and formed various iron phosphate species. The substances behave differently upon interaction with phosphate, although being very similar in composition and crystal structure. Thus, we demonstrated a crucial influence of the ligands in the shell on the binding mechanism. [ABSTRACT FROM AUTHOR]

Concurrent stabilization of oxyanions such as antimony (Sb), arsenic (As), and heavy metals including lead (Pb) and manganese (Mn) in contaminated soils is difficult because of their diverse chemical properties. Antimony and As are stabilized by sorption with iron oxides while heavy metals are stabilized by phosphate. Hence, iron phosphate can be used to simultaneously stabilize Sb and Pb. Therefore, this study aimed to evaluate the possibility of simultaneous stabilization of Sb and Pb using iron phosphate. A single and a mixed solution of Sb and Pb were reacted with synthesized iron phosphate. Contaminated soil by Sb, As, Mo, Cr, and Mn was treated with iron phosphate, and bioavailable metal concentrations were evaluated by extracting the soil with 0.05 M ammonium sulfate. In a single solution, Sb(III) and Sb(V) sorption rate ranged up to 97% and 65%, respectively. In a mixed metal solution, Sb sorption increased compared to the single solution and Pb removal reached more than 95% in all cases. The sorption of Sb increased as the pH decreased, but the Sb(III) sorption was less affected by the pH than Sb(V). In various pH ranges, Sb(III) and Sb(V) sorption rates increased by 26 ~ 32% and 38 ~ 68%, respectively, compared to the single solution. Especially, Sb(V) sorption significantly increased in the presence of Pb at lower pH because of the lower solubility of iron phosphate. In soil, iron phosphate slightly decreased bioavailable As, Cr, Mo, Sb, and Mn concentrations. Therefore, metalloids and metals can be simultaneously stabilized by iron phosphate both in solution and soil. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycle mixed spent LIBs by their own intrinsic redox properties. • Phosphoric acid is used as leaching agent to promote the formation of FePO 4. • Over 97% of valuable metals and high-purity FePO 4 can be recovered in one step. • The amount of phosphoric acid can be reduced to 0.88 mol/L. The recovery of valuable elements in spent lithium-ion batteries (LIBs) has attracted more and more attention. Efficient recovery of valuable elements from spent LIBs with lower consumption and shorter process is the target that people have been pursuing. In this study, the valuable metals (Ni, Co, Mn and Li) and FePO 4 products are simultaneously recovered from mixed spent LiNi x Co y Mn z O 2 and LiFePO 4 in one step under the optimized condition of 0.88 M H 3 PO 4 , a mass ratio of LFP/NCM of 2:1, a L/S ratio of 33:1 and 80 ℃ for 120 min without additional auxiliary reagents. Over 60 % of acid consumption is reduced and the process of adjusting pH is avoidable. The leaching efficiencies of the valuable elements reach up to 99.1 % for Ni, 98.9 % for Co, 99.6 % for Li and 97.3 % for Mn. Almost all of Fe is precipitated as FePO 4 ·2H 2 O. By means of the empirical model, the research on leaching kinetics demonstrates that the leaching reaction is internal diffusion-controlled with the apparent activation energy of valuable metals less than 30 kJ/mol. Furthermore, the redox reaction mechanism between spent LiBs has been explored. And the intrinsic driving force in the phosphoric acid system is found out. This finding may provide an innovative and selective recycling method for valuable elements from mixed spent LIBs with high economic benefit and fewer environmental footprints. [ABSTRACT FROM AUTHOR]

We aimed to investigate phosphorus (P) mobilization by different plant species from organic and inorganic sources in relation to different P mobilization mechanisms. Knowledge about P mobilization is important for producing crops on P sources other than phosphate rock-derived fertilizers. We conducted a greenhouse experiment with four plant species (maize, soy, lupin, mustard) and three P sources (FePO4, phytate, struvite). We determined pH and phosphomonoesterase activity in the rhizosphere using pH imaging and soil zymography. At harvest, root exudates were analyzed for phosphomonoesterase activity, pH, organic acids, and dissolved organic carbon (DOC). Plants were analyzed for biomass, root length, and P content. Struvite was more plant-available than phytate and FePO4 as indicated by higher plant P contents. Soy had the highest biomass and P content, irrespective of P source. Soy exuded up to 12.5 times more organic acids and up to 4.2 times more DOC than the other plant species. Lupin had a 122.9 times higher phosphomonoesterase activity than the other plant species with phytate. The pH in the exudate solution of mustard was on average 0.8 pH units higher than of the other plant species. P uptake by mustard and soy seemed to have also benefited from large root lengths. Taken together, our study indicates that soy has a particularly high potential to mobilize P from struvite and phytate, while mustard has a high potential to mobilize P from FePO4. Therefore, soy and mustard seem to be good options for agricultural production that relies less on phosphate rock-derived fertilizers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Utilizes titanium extraction tailing as a sustainable source for high-quality iron phosphate production. • Efficient separation of iron and titanium is achieved through co-leaching. • The contents of impurities in the product were far below the standard. • Formation of [Fe(HPO 4) 2 ]- complexes in acid leaching promotes iron dissolution, enhancing the efficiency of iron extraction. This study presents a compelling, eco-friendly methodology for extracting valuable materials from titanium extraction tailing (TET) discharged from the reduction rust process. The process efficiently separates titanium and iron by utilizing a co-leaching technique with sulfuric and phosphoric acids. This method results in a high-grade titanium dioxide (TiO 2) with a purity of 61.57 % and an iron leaching rate surpassing 96 % under the optimal conditions of the liquid-to-solid ratio of 4:1, a leaching temperature of 70 °C, and a specific phosphoric acid to iron molar ratio is 1.1. The subsequent refinement phase involves adjusting the pH to 2.0 using ammonia, coupled with controlled precipitation temperature and ageing time, leading to the production of battery-grade iron phosphate (FePO 4) with a purity of 98.82 %, in line with the stringent HG/T4701-2014 standards. The material's phase analysis and morphological characterization confirm its high crystallinity and minimal impurity levels. Moreover, the co-leaching approach facilitates magnetite dissolution, effectively enriching the rutile content in the leach residue and concurrently minimizing the formation of ammonium sulfate salts, thereby enhancing the purity of the iron phosphate. These technological advancements contribute to resource recovery research and offer new avenues for industrial material production, laying a solid foundation for sustainable industrial applications. [ABSTRACT FROM AUTHOR]

In view of the current situation wherein acid resources and valuable components in titanium dioxide waste acid cannot be effectively extracted and are prone to secondary pollution, our research team proposed a new technique consisting of step extraction and the comprehensive utilization of titanium dioxide waste acid. In this paper, the thermodynamics of selective precipitation and the preparation of doped iron phosphate from waste acid were studied. The thermodynamics results show that the content of Al3+, Mn2+, Mg2+, and Ca2+ in the reaction system can be tuned by adjusting the pH during the pre-precipitation process. In the first step, these impurity ions should be settled as much as possible; then, Fe2+ should be oxidized to Fe3+ so as to obtain iron phosphate with higher purity in the next step of the precipitation process. The effects of the reaction temperature, seed crystals, pH value, and P/M on the precipitation process were investigated in detail. The experimental results show that in the reduced state, the optimal precipitation conditions are a temperature of 75 °C, an initial pH value of 4.5, and an optimal P/M molar ratio of 1.1. In the oxidized state, the optimal precipitation conditions are a temperature of 60 °C, a solution pH = 2.5, and a reaction time of 25 min. After calcination, the precipitate mainly consists of iron phosphate, which basically meets the requirements of an iron phosphate precursor.

Batteries made of charge carriers from Earth‐crust abundant materials (e.g., Na, K, and Mg) have received extensive attention as an alternative to Li‐ion batteries for grid storage. However, a lack of understanding of the behavior of these larger ions in the electrode materials hinders the development of electrode structures suitable for these large ions. In this study, we investigate the impact of alkali ions (Li, Na, and K) on the redox chemistry and mechanical deformations of iron phosphate composite cathodes by using electrochemical techniques and in situ digital image correlation. Na‐ion and Li‐ion intercalation demonstrate a nearly linear correlation between electrochemical strains and the state of charge and discharge. The strain development shows nonlinear dependance on the state of charge and discharge for K ions. Strain rate calculations show that K ion intercalation results in a progressive increase in the strain rate for all cycles. Li and Na intercalation induce nearly constant strain rates with the exception of the first discharge cycle of Na intercalation. When the same amount of ions are inserted into the electrode, the electrode shows the lowest strain generation upon Li intercalation compared to larger alkali ions. Na and K ions induce similar volumetric changes in the electrode when the state of charge and discharge is around 30%. Although the electrode experiences larger absolute strain generation at the end of the discharge cycles upon Na intercalation, strain rates were found to be greater for K ions. Potential‐dependent behaviors also demonstrate more sluggish redox reactions during K intercalation, compared to Li and Na. Our quantitative analysis suggests that the strain rate, rather than the absolute value of strain, is the critical factor in amorphization of the crystalline electrode. [ABSTRACT FROM AUTHOR]

A novel process for the high-value-use of iron from bauxite residue was proposed in this work. The process was trying to use the iron-containing stripping solution generated during resource recycling of bauxite residue to produce battery-grade FePO4·2H2O product. Thermodynamics calculation indicates that Fe and P in the stripping solution mainly existed in the form of FeHPO4+, and the theoretical pH for the conversion reaction from FePO4·2H2O to Fe(OH)3 was 1.72. The optimal condition for the synthesis of FePO4·2H2O using the stripping solution was determined as: reaction pH of 0.8, reaction temperature of 90°C, Fe/P ratio of 1, and reaction time of 24 h. XRD result showed that the synthesized FePO4·2H2O was well-crystallized and perfectly matched with the characteristic peaks of FePO4·2H2O. Moreover, all the parameters of the synthesized iron phosphate meet the quality requirements of battery precursor. [ABSTRACT FROM AUTHOR]

Abstract Iron phosphate, Fe2 (HPO4)3*4H2O, is synthesized at ambient temperature, using the inorganic sol–gel method coupled to the microwave route. The experimental conditions for the gelling of Fe (III)-H3PO4 system are previously defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) investigate the acid–base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q a function of T, are examined for time contact varying in the range 0–72 h. The mass suspensions used for this purpose are 0.75, 1.25 and 2.5 g L−1. The point of zero charge (PZC) and isoelectric point (IEP) are defined using the derivative method examining the variations $$\frac{{{\text{dpH}}}}{{{\text{d}}t}} = f\left( {{\text{pH}}} \right)$$ dpH d t = f pH , at lower contact time. A shift is observed for PZC and IEP towards low values that are found to be 2.2 ± 0.2 and 1.8 ± 0.1, respectively. In acidic conditions, the surface charge behavior of synthesized phosphate is dominated by $$\overline{{ > {\text{POH}}}}$$ > POH ¯ group which pKa = 2.45 ± 0.15. Q against T titration method is performed for synthesized Fe2 (HPO4)3*4H2O in NaCl electrolytes. The maximal surface charge (Q) is achieved at the low solid suspension. Hence, for m = 0.75 g L−1, Q value of 50 coulombs is carried at μ = 0.1 and pH around 12, while charge value around 22 coulombs is reached in the pH range: 3–10. The effect of activation time, Q and pH on sodium insertion in iron phosphate, were fully evaluated. To determine the optimal conditions of the studied process, mathematical models are used develop response surfaces in order to characterize the most significant sodium interactions according to the variation of the pH, Q, the contact time and the contents of the synthesized material.

A bifunctional and high‐efficiency solid acid catalyst(S‐SBC) was prepared from papermaking sludge by calcining and sulfonation with concentrated sulfuric acid. The monoclinic FePO4 was added to assist S‐SBC to improve HMF yield. The structure characterization of S‐SBC and its catalytic performance for 5‐hydroxymethylfurfural(HMF) preparation from fructose, glucose and cellulose were investigated. Metal ions and −SO3H in the S‐SBC had synergistic effects on the HMF yield. The HMF yield from fructose, glucose and cellulose were respectively 90.3 %, 73.7 % and 28.8 % with S‐SBC alone. The combination of monoclinic FePO4 and S‐SBC could effectively improve the yield of HMF from glucose and cellulose. The highest yield of HMF from glucose and cellulose were respectively 89.5 % and 53.3 % with the binary catalysts. The mechanism of the synergistic action of the binary catalysts was proposed. Bronsted acid from metal ions hydrolysis and ‐SO3H, ‐COOH, ‐OH grafted on the surface of biochar promoted hydrolysis of cellulose to glucose, which was then coordinated with Lewis acids and isomerized to fructose. Finally, HMF was obtained by dehydrating from fructose. [ABSTRACT FROM AUTHOR]

[Display omitted] • The optimized V-doped FeP nanoflowers are prepared for enhanced HER. • V doping lowers d-band central position and hydrogen formation energy barrier. • V-FeP shows low overpotentials of 290 mV to deliver 1000 mA cm−2 for 24 h. • Over 100-h stability at 1000 mA cm−2 for water electrolysis is obtained. Reasonable design of hydrogen evolution reaction (HER) electrocatalyst from the perspective of electronic structure is a vital way to optimize the catalytic activity. Mono-metallic iron-based phosphates have been shown to be active toward HER, but their performance remains unsatisfactory despite their abundant reserves and low preparation cost. Here, guided by the d-band center and band structure theories, V-doped FeP nanoflower grown directly on iron foam are constructed. Combining the density functional theory (DFT) simulations with physical characterizations reveal that the enhanced HER activity is mainly attributed to the lowed d-band central position, increased water dissociation capacity, decreased hydrogen formation energy barrier and reduced charge transfer impedance. As a HER catalyst in 1 M KOH, the obtained V-FeP shows low overpotentials of ∼149, ∼246 and ∼290 mV to deliver the current densities of 100, 500 and 1000 mA cm−2 with at least 24 h. When coupled with other highly active oxygen evolution reaction (OER) catalyst (NiFe-LDH/IF), the NiFe-LDH/IF(+) || V-FeP/IF(-) pair also performs a low cell voltage and over 100-h stability at high current density of 1000 mA cm−2, which endows it a large potential in the practical electrolytic water industry. Our work may provide a reference for the enhancement of inert and low-cost HER-active iron phosphide. [ABSTRACT FROM AUTHOR]

Iron phosphate-modified pollen microspheres (pollen@FePO4) were prepared and applied as sorbents for the removal of heavy metals (Cd2+ and Pb2+) from the aqueous solution. Batch sorption studies were conducted to investigate the effects of solution pH, contact time, sorbent dosage, and metal concentration on the adsorption process. The sorption of Cd2+ and Pb2+ ions on pollen@FePO4 corresponds to the pseudo-second-order model and Langmuir isotherm, which is similar to the unmodified pollen. At pH 5.92, pollen@FePO4 offers maximum adsorption capacities of 4.623 and 61.35 mg·g−1 for Cd2+ and Pb2+, respectively. The faster sorption kinetics and higher adsorption capacities of Cd2+ and Pb2+ ions onto pollen@FePO4 than pollen indicates that it might be a promising material for the removal of heavy metal ions in aqueous solutions. The possible adsorption mechanism involves electrostatic and chemisorption for Cd2+ and mainly complexion for Pb2+.

• Selective extraction of chromium can be achieved by co-operation of phosphoric acid and oxalic acid. • Iron phosphate concentrate is yielded as by product from laterite residue. • The oxalic acid addition enhances the dissolution of chromium and iron. • Chromium is recovered by precipitation in the form of phosphate. With the rising demand for nickel and cobalt, laterite residue containing chromium is extensively generated through the laterite hydrometallurgical process, posing a significant burden on environmental protection and the sustainable development of the nickel industry. This study presents a novel and environmentally friendly method for selectively extracting chromium from laterite residue and yielding iron phosphate concentrate. In this method, iron, as the major component, is simultaneously transformed into iron phosphate as solid state, while chromium is extracted into solution by a minimal amount of phosphoric acid. The effects of phosphoric acid and oxalic acid usage, temperature, liquid-to-solid ratio, and leaching time on the transformation and removal were investigated. Thermodynamic analysis and experimental results indicated that the addition of oxalic acid promoted chromium extraction with minimal impact on the transformation of hematite and iron phosphate. The results of SEM, XPS, and XRD revealed the conversion of laterite residue to iron phosphate. At an oxalic acid dosage of 10 %, almost 90 % of the iron remained in the residue as iron phosphate, while over 60 % of the chromium was extracted into the solution, resulting in a chromium concentration of 1.1 g/L. The solution underwent a two-step treatment process, primarily to recycle the soluble iron species. The extracted chromium was captured by adding calcium hydroxide at pH ∼ 3.0 in the form of phosphate. [ABSTRACT FROM AUTHOR]

In this study, we synthesized 5 wt% MoOx and WOx conjugated iron phosphate nanotubes (FeP-NT) catalysts for benzylation of benzene using benzyl alcohol to investigate the role of acid and redox sites. The catalysts were analysed by different techniques along with insitu FT-IR spectroscopy. The 5WOx-FeP-NT catalyst exhibited 100% conversion of benzyl alcohol in 60 min, whereas 5MoOx-FeP-NT catalyst offered only 59% benzyl alcohol conversion in 240 min. The characterization results indicated that high acidity and moderate redox nature of 5WOx-FeP-NT is responsible for better benzyl alcohol adsorption and benzylation activity compared to low acidity and high redox nature of 5MoOx-FeP-NT.

Simple Summary: Arion vulgaris has become a major invasive pest slug in Europe, causing extensive damage to many crops. To control this pest, the use of chemical molluscicides remains the most important. However, despite the proved efficacy, they still have detrimental environmental effects. We performed two double-replicated laboratory studies testing molluscicide pellets with metaldehyde (3% and 5%) and iron phosphate (1%) and found the reluctance of slugs to eat a full lethal dose regardless of whether the poison is stronger or weaker. As a consequence, slugs remain alive and only reduce their herbivory by half; the remaining granules or their parts are the main source of toxic effects of molluscicides in the environment. Moreover, a higher metaldehyde content of the pellets does not lead to lower herbivory. The results showed that a new application of molluscicides could be useful; the application rate should be decreased according to the ability of slugs to eat a certain amount of molluscicide pellets. Arion vulgaris are mostly controlled using chemical molluscicide products, and the detrimental environmental effects of these molluscicides can be reduced by decreasing the number of pellets applied per unit area. The objective of this study was to compare three slug control methods during two double-replicated seven-day laboratory experiments, in which slugs could choose the number of pellets with metaldehyde (3% or 5%) or iron phosphate (1%) and different types of food: leafy plants (lettuce), root vegetables (carrot), a cereal-based diet (oatmeal), or an animal-based diet (dry cat food). Slugs were irrigated and allowed to recover. We found a reluctance of slugs to eat big amounts of pellets and, therefore, to reach a full lethal dose, which resulted in low mortality (the rate was only 2.1%), regardless of whether the poison was stronger or weaker. Herbivory of slugs was in some cases reduced by half, but no treatments resulted in slugs to stop eating. Pellets with 3% metaldehyde were significantly more acceptable than pellets with 5% metaldehyde (uneaten pellets were left). The results showed that the new application of molluscicides could be useful; the application rate should be decreased according to the slugs number and ability of slugs to eat a certain amount of molluscicide pellets. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is limiting nutrient in many soils, and P availability may often depend on iron (Fe) speciation. Colloidal iron phosphate (FePO4coll) is potentially present in soils, and we tested the hypothesis that phytate exudation by Pteris vittata might dissolve FePO4coll by growing the plant in nutrient solution to which FePO4coll was added. The omission of P and Fe increased phytate exudation by P. vittata from 434 to 2136 mg kg−1 as the FePO4coll concentration increased from 0 to 300 mM. The total P in P. vittata tissue increased from 2880 to 8280 mg kg−1, and the corresponding increases in the trichloroacetic acid (TCA) extractable P fractions were inorganic P (860–5100 mg kg−1), soluble organic P (250–870 mg kg−1), and insoluble organic P (160–2030 mg kg−1). That is, FePO4-solubilizing activity was positive correlated with TP, TCA P fractions in P. vittata, TP in growth media, and root exudates. This study shows that phytate exudation dissolved FePO4coll due to the chelation effect of phytic acid on Fe; however, the wider question of whether phytic acid excretion was prompted by deprivation of P, Fe, or both remains to be answered. [ABSTRACT FROM AUTHOR]

Iron phosphates have rich chemical structures with various morphologies and sizes. Since they are environment friendly with good biocompatibility, they have good performances in the fields of catalysis and battery electrode material rising in recent years, as well as in the traditional fields like agriculture and steel. They also have important applications in adsorption, separation and concentration due to their unique structural characteristics. In this paper, iron phosphates are classified based on their common characteristics such as structure, morphology and size, and their application in the past two decades is reviewed, with emphasis on their application in adsorption, separation and concentration of different species. Further, their application in adsorption, separation and concentration of heavy metals is prospected.

Phosphorus (P) deficiency is one of the major factors limiting plant growth in acid soils, where most P is fixed by toxic aluminum (Al). Phosphate-solubilizing bacteria (PSBs) are important for the solubilization of fixed P in soils. Many PSBs have been isolated from neutral and calcareous soils, where calcium phosphate is the main P form, whereas PSBs in acid soils have received relatively little attention. In this study, we isolated a PSB strain from the rhizosphere of Lespedeza bicolor, a plant well adapted to acid soils. On the basis of its 16S rRNA gene sequence, this strain was identified as a Nguyenibacter species and named L1. After incubation of Nguyenibacter sp. L1 for 48 h in a culture medium containing AlPO4 as the sole P source, the concentration of available P increased from 10 to 225 mg L−1 , and the pH decreased from 5.5 to 2.5. Nguyenibacter sp. L1 exhibited poor FePO4 solubilization ability. When the pH of nonPSB-inoculated medium was manually adjusted from 5.5 to 2.5, the concentration of available P only increased from 6 to 65 mg L−1 , which indicates that growth medium acidification was not the main contributor to the solubilization of AlPO4 by Nguyenibacter sp. L1. In the presence of glucose, but not fructose, Nguyenibacter sp. L1 released large amounts of gluconic acid to solubilize AlPO4. Furthermore, external addition of gluconic acid enhanced AlPO4 solubilization and reduced Al toxicity to plants. We conclude that secretion of gluconic acid by Nguyenibacter sp. L1, which is dependent on glucose supply, is responsible for AlPO4 solubilization as well as the alleviation of Al phytotoxicity by this bacterial strain. [ABSTRACT FROM AUTHOR]

Water electrolysis is a promising method for hydrogen production, so the preparation of low-cost and efficient electrocatalysts with a quick and simple procedure is crucial. Herein, iron phosphate (Fe7(PO4)6) was prepared via microwave radiation using ionic liquid (IL) as iron and phosphorus dual-source. This method is simple and rapid, and the product can be directly used as electrocatalysts without further treatment. The experimental results show that the IL can influence the morphology and electrocatalytic performance. Moreover, the addition of carbon nanotubes (CNTs) is favorable for formation of iron phosphate nanoparticles to improve the catalytic activities. As hydrogen evolution reaction (HER) catalyst, this iron phosphate/CNTs exhibits an onset overpotential of 120 mV, Tafel slope of 32.9 mV dec-1, and current densities of 10 mA cm−2 at overpotential of 185 mV. Then, it obtains a good activity for oxygen evolution reaction (OER) with a low onset potential of 1.48 V, Tafel slope of 73.3 mV dec-1, and it only needs an overpotential of 300 mV to drive the 10 mA cm−2. This bifunctional catalyst also shows good durability for HER and OER. This microwave-assisted method provides an outstanding strategy to prepare iron phosphate in a simple and fast process with good catalytic performance for water splitting.

Iron phosphate in the composition of concentrate is a fairly strong chemical compound. However, with the help of gaseous substances, such complex compounds decompose when heated to the required temperature, which contributes to the reduction of not only iron, but also phosphorus. Hydrogen and carbon monoxide were used as gaseous reducing agents. This article describes in detail the thermodynamic analysis of the reduction of phosphorus from iron phosphate, its interaction with hydrogen and carbon monoxide.

Iron phosphate, Fe2 (HPO4)3*4H2O, is synthesized at ambient temperature, using the inorganic sol–gel method coupled to the microwave route. The experimental conditions for the gelling of Fe (III)-H3PO4 system are previously defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) investigate the acid–base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q a function of T, are examined for time contact varying in the range 0–72 h. The mass suspensions used for this purpose are 0.75, 1.25 and 2.5 g L−1. The point of zero charge (PZC) and isoelectric point (IEP) are defined using the derivative method examining the variations dpH d t = f pH , at lower contact time. A shift is observed for PZC and IEP towards low values that are found to be 2.2 ± 0.2 and 1.8 ± 0.1, respectively. In acidic conditions, the surface charge behavior of synthesized phosphate is dominated by > POH ¯ group which pKa = 2.45 ± 0.15. Q against T titration method is performed for synthesized Fe2 (HPO4)3*4H2O in NaCl electrolytes. The maximal surface charge (Q) is achieved at the low solid suspension. Hence, for m = 0.75 g L−1, Q value of 50 coulombs is carried at μ = 0.1 and pH around 12, while charge value around 22 coulombs is reached in the pH range: 3–10. The effect of activation time, Q and pH on sodium insertion in iron phosphate, were fully evaluated. To determine the optimal conditions of the studied process, mathematical models are used develop response surfaces in order to characterize the most significant sodium interactions according to the variation of the pH, Q, the contact time and the contents of the synthesized material. [ABSTRACT FROM AUTHOR]

Many physical and chemical properties of Na+ are very similar to those of Li+, and therefore, some electrode materials for lithium‐ion batteries can also work with sodium ions. As the Na+ ion is larger than Li+, the strains in the host lattice are larger, which can cause deviations in the electrochemical reactions. Herein, mechanical stresses are compared, which are measured by the in situ substrate curvature method during (de)lithiation/(de)sodiation of an FePO4 electrode. The (de)lithiation and (de)sodiation experiments are performed on the same electrode. According to the change of the lattice parameters, during electrode operation, NaxFePO4 particles experience a volume change that is 2.6 times larger than that of LixFePO4. In the measurements, the composite electrode exhibits a change of the stress amplitude between operation with Li and Na by roughly one order of magnitude for 0 < x < 1. Compared with Li+, the mechanical stress evolution during extraction and insertion of Na+ is highly asymmetric. The observed asymmetry in the electrochemical and the mechanical data may be explained by the different energies that are required to move an intermediary amorphous phase away from or toward the crystalline sodium‐rich regions during the (de)sodiation of NaFePO4. [ABSTRACT FROM AUTHOR]

FePO 4 (FP) as a precursor of lithium iron phosphate batteries has been mass-produced in recent years and may face the problem of overproduction. Also, the phosphorus removal process in wastewater treatment plants produces large amounts of sludge containing FP. It is a huge waste of both iron and phosphorus resources if such FP cannot be utilized. This work explores a new strategy for utilizing FP to activate sulfite (S(IV)) autoxidation for simultaneous pollutant degradation and phosphorus release in water. Acid orange 7 (AO7) and several pharmaceutical and personal care products (PPCPs) were chosen as the target pollutants for the FP‒S(IV) system and the influence of pH, FP and S(IV) dosage were investigated. Typically, up to 89.5% AO7 (10 mg L−1) and above 60% PPCPs (10 μM) were oxidized within 90 min by adding 1 g L−1 FP and 2 mM S(IV) into the water at the initial pH 4.0. Results of quenching experiments and electron spin resonance analysis confirmed SO 5 •− as the dominant reactive species for AO7 oxidation. Meanwhile, two stages of phosphorus release from FP were observed along with the AO7 oxidation and their linear correlation over the pH range 3.0–8.0 was proven. The first stage (0–5 min) was thought to be dependent on the initial pH and was obviously faster than the second stage (10–45 min), whose rate increased linearly with S(IV) dosage. Phosphorus released high up to 24.3 μM at 90 min with 4 mM S(IV). Moreover, the mechanisms of FP activated sulfite autoxidation as well as phosphorus release were proposed, and the AO7 degradation pathway was investigated. This study provides a novel possibility for FP waste utilization and potential recovery of phosphorus resources. [Display omitted] • Simultaneous pollutant oxidation and P release were achieved in FePO 4 –S(IV) system. • SO 5.•− was predominately responsible for the removal of acid orange 7. • P release was correlated with the oxidation of acid orange 7 at various pHs. • Mechanisms of S(IV) autoxidation and phosphorus release were proposed. [ABSTRACT FROM AUTHOR]

The recovery and regeneration of FePO 4 from lithium extraction slag (LES) are crucial steps in the closed-loop recycling of waste LiFePO 4 batteries. This necessity arises despite the low commercial value of LES, as conventional recovery methods are cost-prohibitive, leading to insufficient attention to LES recovery. The recent surge in retired batteries has resulted in a significant accumulation of LES, posing serious environmental concerns, however, the high content of Fe and P resources in LES presents a potential value. The study begins with a theoretical analysis, concluding that the reduction leaching of LES is a feasible approach. By integrating this with the Fe powder synthesis route for FePO 4 , it is found that efficient leaching of LES can be achieved using a low concentration of H 2 SO 4 , thereby significantly reducing the recovery cost. This method not only efficiently utilize LES but also alleviates environmental pressure. The thermodynamic analysis sheds light on the mechanism of LES leaching and FePO 4 synthesis, confirming the feasibility of each reaction. Optimal leaching conditions (1.4 times the stoichiometric amount of H 2 SO 4 , 1.5 times the amount of Fe powder, an L/S ratio of 5 mL/g, and a reaction duration of 150 min at 60 °C), under which the leaching rates of Fe and P reached 94.66% and 98.23%, respectively. Additionally, the study introduces a method to remove the main impurity Al in LES, achieving a removal rate of over 99%, reducing its concentration to below 100 ppm. Other impurities, such as Ti, Mn, and Zn, also meet the Chinese Chemical Industry Standard (HG/T 4701-2021). Comparative analyses were conducted between regenerated R-FePO 4 , commercial C–FePO 4 , and untreated LES (r-FePO 4). LiFePO 4 materials derived from these sources were synthesized, followed by an evaluation of their electrochemical performance. The regenerated R-FePO 4 matched the quality of commercial FePO 4 and significantly outperformed r-FePO 4. Additionally, the process proposed in this study yields significant economic benefits, estimating a profit of 719.6 $/t of recycled LES. This research proposes a cost-effective and efficient method for regenerating high-quality battery-grade FePO 4 from LES, offering a significant contribution to the closed-loop recycling of waste LiFePO 4 batteries. • With the assistance of Fe powder, only a small amount of H 2 SO 4 is required to efficiently leach Fe and P resources from LES. • Impurities have been effectively removed, and the impurity content meets the requirements for battery-grade FePO 4. • The regenerated FePO 4 demonstrates excellent electrochemical performance comparable to commercial materials. [ABSTRACT FROM AUTHOR]