Submicron ammonium perrhenate was prepared via vacuum spray freeze drying.The effects of ammonium perrhenate solution concentration,feed pump flow rate and initial drying chamber temperature during vacuum spray freeze drying on the particle size and morphology of ammonium perrhenate and its re-duced rhenium powder were investigated by single-factor experiments and orthogonal experiments.The re-sults of single-factor experiments indicate that the atomizer is blocked due to the crystallization of super-saturated ammonium perrhenate at low temperature when the mass concentration of ammonium perrhenate exceeds 20 g/L.Submicron ammonium perrhenate particles with an average size of<1μm can be obtained only at a concentration of 20 g/L,and the corresponding reduced rhenium powder exhibits good morpho-logical heritability.Orthogonal experimental results show that feed pump flow rate is the key factor(range 78.34%)controlling the proportion of acicular morphology of ammonium perrhenate.The combination of low flow rate(e.g.,5 mL/min),medium-low temperature(e.g.,-50℃)and low concentration(e.g.,10 g/L)can significantly increase the acicular morphology proportion(up to 100%).This study reveals the regulation mechanism of droplet dispersion-crystallization kinetics on grain morphology,providing a basis for process parameter selection in the controllable synthesis of rhenium-based materials.

Using walnut shell biochar(WSBC)prepared by pyrolysis as the carrier,Sb(Ⅲ)was first ad-sorbed from aqueous solution to realize resource utilization.Subsequently,Sb(TPA)MOF@WSBC compo-sites were synthesized in situ with Sb(Ⅲ)adsorbed on the WSBC surface as the metal center and tereph-thalic acid(TPA)as the organic ligand.The microstructure and surface characteristics of the materials were characterized by SEM,XRD,FT-IR,BET,XPS,etc.The effects of adsorbent dosage and wastewater pH value on Sb(Ⅲ)adsorption by three adsorbents(WSBC,Sb(TPA)MOF,Sb(TPA)MOF@WSBC)were comparatively investigated.The adsorption mechanism of the composite toward Sb(Ⅲ)was elucida-ted using adsorption kinetics,thermodynamics,and adsorption isotherm models,and its reusability was evaluated through cyclic regeneration experiments.The results show that the Sb(TPA)MOF@WSBC composite exhibits octahedral Sb(TPA)MOF particles uniformly dispersed and loaded on the WSBC surface.Compared with WSBC and Sb(TPA)MOF,the composite possesses a significantly increased specific sur-face area and pore volume,which can provide abundant adsorption active sites.With the increase of adsor-bent dosage,the adsorption capacity of Sb(Ⅲ)(calculated by unit mass of adsorption material)decreases significantly.With increasing pH value,the adsorption capacity of Sb(Ⅲ)first decreases and then increa-ses.When the initial concentration of Sb(Ⅲ)in the wastewater is 20 mg/L,pH is 8,and the solid-liquid ra-tio of adsorbent to wastewater is 0.5 g/L,the equilibrium adsorption capacity of Sb(TPA)MOF@WSBC composite for Sb(Ⅲ)is 2.9123 mg/g.The adsorption behaviors of three adsorbents all fit the Lagergren second-order kinetic model and the Langmuir adsorption isotherm model,indicating monolayer adsorption.Thermodynamic analysis demonstrates that the adsorption process is spontaneous,exothermic and accom-panied by a decrease in entropy,and lower temperatures are more favorable for the adsorption reaction.In addition,the Sb(TPA)MOF@WSBC composite exhibits excellent recycling stability,and its adsorption mechanism is dominated by hydrogen bonding,Sb(Ⅲ)-πinteraction and coordination complexation.This study provides a novel composite adsorbent for the treatment of antimony-containing wastewater.

The widespread application of lithium-ion batteries(LIB)has led to the generation of massive spent batteries,triggering resource shortages and environmental risks.The recovery of high-value metals(e.g.,Co,Ni,Li)from these spent batteries is of significant economic and environmental significance.However,existing recycling technologies still face challenges in efficiency and sustainability.This paper re-views the latest research progress in pretreatment technologies for spent LIB recycling,covering discharge inactivation,disassembly and mechanical crushing,physical separation(such as eddy current separation,electrostatic separation,and gravity/wind separation),and binder removal.The literatures indicate that a key technical system—ranging from safe discharge treatment,automated disassembly and selective cru-shing for higher black mass recovery,and diversified physical separation for efficient component segrega-tion,down to binder removal which critically determines the efficiency of subsequent hydrometallurgy or flotation—could optimize the efficiency and sustainability of LIB recycling.Furthermore,this paper discus-ses the advantages and disadvantages of each pretreatment technology,along with the limitations and gaps of existing processes.It also outlines future research and industrialization directions,such as constructing a multi-stage integrated″discharge-crushing-screening-pyrolysis-separation″flowsheet to maximize recovery efficiency.This review provides a comprehensive reference for researchers and engineers in the LIB recy-cling field,emphasizing the critical role of pretreatment in building an efficient and environmentally sus-tainable battery circular industry.

In the uninjected LFP cathode sheets,the LFP cathode material is not involved in the charge-dis-charge deintercalation of lithium ions,and its structure remains intact,which provides a stable raw material for the repair of LFP cathode material.The separation of LFP cathode material from current collector alu-minum foil is a key issue in the pretreatment process of electrode repair.In this paper,the domestic tech-nologies for stripping uninjected LFP cathode sheets are systematically reviewed,and the principles,advan-tages and disadvantages of various wet and dry stripping technologies are analyzed and compared.Among them,the pyrolysis stripping method combines wet and dry stripping technologies,and there is no waste water generated.It is an efficient stripping method with industrial mass production prospects.In order to reduce the cost,improve the quality of stripped products and maximize the resource utilization of uninjected LFP cathode sheets,the industrialization of stripping of uninjected LFP cathode sheets must control the process parameters,optimize equipment selection,and reduce environmental pollution.

In aqueous zinc-ion batteries(AZIBs),the VOPO₄·2H₂O cathode material is prone to dissolu-tion due to erosion by free water in the electrolyte during charge-discharge cycles,resulting in severe vol-tage decay and capacity loss.By using its abundant sulfonyl oxygen atoms as hydrogen-bond acceptors,high-concentration LiTFSI can effectively reduce the content of free water and inhibit cathode dissolution.However,its high cost and high viscosity limit its practical application.To address this issue,this study proposes a synergistic replacement strategy for Zn(OTf)₂ electrolyte:Low-cost fructose(Fru)is used to partially replace high-concentration LiTFSI.Under the premise of maintaining a similar total number of hydrogen-bond acceptors,this strategy significantly reduces electrolyte viscosity and cost,optimizes Zn2+transport kinetics,and successfully constructs an optimized electrolyte system of 4.5 m Zn(OTf)₂+11 m Fru+8.5 m LiTFSI(m represents mol/kg H₂O).Systematic comparisons were conducted with 4 m Zn(OTf)₂ and 1 m Zn(OTf)₂+18 m LiTFSI electrolytes.Characterization results via XRD,SEM-EDS,and TEM demonstrate that VOPO₄·2H₂O powder exhibits good crystallinity and a distinct lamellar stacking structure.Immersion experiments show that the VOPO₄·2H₂O powder undergoes obvious dissolution within only 10 min in 4 m Zn(OTf)₂ electrolyte,while no significant dissolution occurs after immersing in the two LiTFSI-containing electrolytes for 10 d.Electrochemical test results indicate that the optimized electrolyte significantly improves the cycle stability and rate performance of the VOPO₄·2H₂O cathode,achieving a capacity retention rate of 95%after 150 cycles at 1 C,which is superior to that of the compara-tive systems.Kinetic analysis further reveals that the optimized electrolyte effectively reduces the charge transfer resistance and significantly improves the Zn2+diffusion coefficient.Raman spectroscopy confirms that in the optimized electrolyte,fructose molecules,with the flexible configuration of their five hydroxyl groups,synergize with abundant hydrogen-bonding sites on LiTFSI to form a dense hydrogen-bond net-work with water molecules,which significantly reduces the free water content,thereby inhibiting the disso-lution and irreversible phase transition of VOPO₄·2H₂O.This work solves the problems of high viscosity and cost of high-concentration LiTFSI electrolyte system through a low-cost and environmentally friendly electrolyte design strategy,provides an effective approach for the structural stabilization of VOPO₄·2H₂O cathode materials in AZIBs,and exhibits promising application potential.

Using CaCO₃,HfO₂ and MgO as raw materials,a series of CaHf_1-xMg_xO_3-δ(x=0.06,0.12,0.18,0.24,δis oxygen vacancy concentration,hereafter referred to as CHM)solid electrolytes were pre-pared by a high-temperature solid-state reaction method.The structure was characterized by XRD and SEM-EDS,the electrochemical performance under various conditions was systematically evaluated by elec-trochemical impedance spectroscopy,and the dominant temperature range of proton conduction was determined via the H/D isotope effect.The results show that all prepared CHM solid electrolyte samples exhibit a single perovskite phase with uniform and dense microstructure,and their relative densities exceed 98%,which is higher than that of the undoped sample.The conductivity of the CHM solid electrolytes first in-creases and then decreases with increasing Mg doping content,reaching an optimum at x=0.12,and in-creases significantly with increasing temperature.In the temperature range of 973~1373 K,the conductivi-ty of CHM solid electrolytes in H2-rich atmospheres(dry H2+wet H2)ranges from 6.94×10^-6S/cm to 2.83×10^-4 S/cm,with activation energies of 0.77~0.96 eV.In O₂-rich atmospheres(dry O₂+wet O₂),the conductivity ranges from 5.87×10^-6S/cm to 1.65×10^-3 S/cm,with activation energies of 1.34~1.49 eV.Meanwhile,a pronounced H/D isotope effect of CHM solid electrolytes is observed in the temper-ature range of 973~1173 K,indicating that proton conduction dominates.Above 1173 K,oxygen-vacancy and electronic conduction become predominant.The chemical diffusion coefficient of H+in the CHM(x=0.12)solid electrolyte ranges from 1.04×10^-6cm²/s to 7.95×10^-6cm²/s within 973~1273 K,with a diffusion activation energy of 70.822 kJ/mol.The above results indicate that Mg-doped CaHfO₃-based so-lid electrolytes exhibit good electrochemical performance and represent promising candidates for application in high-temperature molten metal hydrogen sensors.

The crude sodium tungstate solution obtained from scheelite decomposition contains a certain concentration of fluorine,which easily leads to the concentration of fluoride in smelting wastewater exceeding the national discharge standard.In this study,hydroxyapatite was used as a fluoride-removing reagent,which reacted with fluorine ions to form calcium fluorophosphate precipitate with very low solubility,so as to deeply remove fluoride from the crude sodium tungstate solution.The effects of hydroxyapatite dosage,reaction temperature,solution pH value,reaction time and initial fluoride concentration on the fluoride removal were investigated.The experimental results show that hydroxyapatite has an excellent fluoride-removing performance in the crude sodium tungstate solution.Under the conditions where the fluoride concentration is 0.5~5.5 g/L,the dosage of hydroxyapatite is 1.8 times of the theoretical amount,reaction temperature is 80℃,the solution pH value is 10.5,and reaction time is 60 min,the fluoride removal rate is more than 96%,and the tungsten loss rate in the precipitated slag is less than 0.27%,thereby realizing the high-efficiency removal of fluoride with low tungsten loss.After fluoride removal,the crude sodium tungstate solution is subjected to subsequent ion exchange treatment,and the fluoride concentration in the discharged smelting wastewater meets the national discharge standard.

To improve the tungsten-molybdenum loading capacity of the deactivated organic phase(with N263 as the extractant)in the alkaline extraction section during the preparation of ammonium paratungstate from low-grade complex scheelite,this study adopted the ion exchange method and employed NaCl solution as the ion exchanger to remove harmful anions from the organic phase.The effects of NaCl solution concentration,O/A phase ratio,reaction temperature,single ion exchange duration and the number of ion exchange cycles on the tungsten-molybdenum loading capacity of the organic phase were systematically investigated through single-factor experiments.Furthermore,through counter-current extraction-washingstripping experiments,the tungsten and molybdenum extraction rates of the organic phase after NaCl ion exchange and NH₄HCO₃ conversion were explored,along with an assessment of whether the raffinate and stripping solution meet the requirements of industrial production.The results of single-factor experiments show that the optimal conditions for treating the deactivated alkaline extraction organic phase by the NaCl ion exchange method are as follows:NaCl concentration of 3 mol/L,O/A phase ratio of 1∶1,reaction temperature of 35℃,single ion exchange duration of 3 min,and 7 ion exchange cycles.After the organic phase obtained under these optimal conditions is converted with NH₄HCO₃,its WO₃ loading capacity is increased by 85.49%and Mo loading capacity by 72.56%,compared with those of the deactivated alkaline extraction organic phase.Under the conditions where the O/A phase ratios for extraction,washing,and stripping are 1∶2,1∶0.35,and 1∶2.6 respectively,and other parameters remain consistent with the current industrial production conditions,a comparison of the tungsten-molybdenum extraction performances of different organic phases after 6-stage counter-current extraction,4-stage washing,and 10-stage stripping experiments shows that the organic phase modified by NaCl ion exchange-NH₄HCO₃ conversion achieves extraction rates of 92.12%for WO₃ and 95.31%for Mo.Although these rates remain lower than those of the freshly prepared alkaline extraction organic phase,they increase by 42.46%and 40.08%respectively compared with the deactivated alkaline extraction organic phase without NaCl ion exchange treatment.Its tungstenmolybdenum loading capacity meets the requirements of industrial production,which breaks the restriction of the alkaline extraction section on production output during the preparation of ammonium paratungstate from low-grade complex scheelite.Various indexes of the raffinate and stripping solution obtained after extraction and stripping of the organic phase modified by NaCl ion exchange-NH₄HCO₃ conversion all meet the industrial production requirements.The increased tungsten content in the stripping solution reduces the evaporation energy consumption of the subsequent APT crystallization section,while the decreased tungsten content in the raffinate improves the direct recovery rate of the extraction section.Therefore,the NaCl ion exchange treatment of the deactivated organic phase can effectively reduce the production cost.

To achieve efficient separation and recovery of Ga from sulfuric acid leaching solution of claystone of the coal-aluminum rock series,this study employed Seplite^®LSC-900 gallium-extraction chelating resin for adsorption-desorption experiments on a single Ga solution.The effects of solution pH,adsorption time,types and concentrations of desorbent,and desorption time on Ga adsorption-desorption efficiency were investigated.The microstructure of the resin before and after adsorption was characterized via SEMEDS.Meanwhile,FTIR was employed to analyze the adsorption mechanism of the resin for the sulfuric acid leaching solution of claystone of the coal-aluminum rock series.Additionally,under the optimized adsorption-desorption conditions,the separation efficiency of Ga from other impurity ions in the sulfuric acid leaching solution of claystone of the coal-aluminum rock series was explored.The results show that when the pH value of the single Ga solution is 4 and the adsorption time is 120 min,the Ga adsorption rate reaches approximately 80%.After adsorption,the cross-linked structure of the resin's strip-like fibers increases,and Ga embeds into the pore channels and induces an increase in surface roughness of the pore channels.The adsorption of Ga from the sulfuric acid leaching solution by the resin is attributed to the synergy between electrostatic interaction and chemical coordination.Specifically,the—OH and—NH2 functional groups generate electrostatic interactions with[Ga(SO₄)]⁺,while the O atoms in—OH form Ga—O coordination bonds with Ga.The optimal desorption effect of Ga is achieved when the saturated adsorption resin is eluted with 1.5 mol/L HCl for 1 h,with a desorption rate of about 80%.The results of adsorptiondesorption experiments on the sulfuric acid leaching solution of claystone of the coal-aluminum rock series indicate that LSC-900 gallium-extracting chelating resin exhibits excellent selective adsorption capacity for Ga and Zr.Furthermore,Ga can be almost completely desorbed whereas Zr is difficult to desorb,thus successfully achieving effective separation of Ga from other metal ions in the leaching solution.This study provides technical support for the efficient recovery of Ga from the leaching solution of claystone of the coal-aluminum rock series.

Using hydrochloric acid as a catalyst,selenium and tellurium were recovered from gold-precipitated solution by SO₂ reduction.The effects of concentrated hydrochloric acid dosage,reaction time and H+concentration on the recovery rates of selenium and tellurium were investigated.The phase and morphology of the reduction products were analyzed by XRD and SEM,respectively.Besides,a comparative study was conducted on the effects of sodium sulfite and hydrazine hydrate as reducing agents on the recovery rates of selenium and tellurium from gold-precipitated solution.The results show that when selenium and tellurium are recovered from the gold-precipitated solution via hydrochloric acid-catalyzed SO₂ reduction,the recovery rates of selenium and tellurium reach 99.63%and 97.14%,respectively,under the conditions of a reaction temperature of 85℃,a concentrated hydrochloric acid(36%)dosage of 6%of the volume of the goldprecipitated solution,a reaction time of 4 h,and a H+concentration of 5.1 mol/L.In the reduction products,both selenium and tellurium exist in elemental form,with a strip-like morphology interspersed with particles.When sodium sulfite is used as the reducing agent with a dosage of 7.58 times the theoretical amount,the recovery rates of selenium and tellurium are only 76.88%and 35.71%,respectively.When hydrazine hydrate(80%)is used as the reducing agent with a dosage of 2.5%of the volume of the gold-precipitated solution,the selenium recovery rate reaches 99.38%and the tellurium recovery rate is 92.86%.Comparative analysis indicates that sodium sulfite is not suitable as a reducing agent for selenium and tellurium recovery from the gold-precipitated solution.Although hydrazine hydrate as a reducing agent achieves high recovery rates,it exhibits a relatively high cost.By comparison,the hydrochloric acid-catalyzed SO₂ reduction process for selenium and tellurium recovery from the gold-precipitated solution not only delivers ideal recovery efficiency,but also offers advantages of simple operation and low cost,thus demonstrating greater development prospects.