The O3-type sodium nickel-iron-manganese oxide cathode materials are widely applied in the field of large-scale energy storage systems due to high theoretical capacities，better low-temperature performance，safety performances and so on.The modification of O3-type sodium nickel-iron-manganese oxide cathode materials have been recognized as a key technical approach，by which the cycling performance and fast charging/discharging capabilities of sodium-ion batteries are effectively enhanced.Herein，recent advances in the modification strategies for O3-type cathode materials were systematically summarized，an in-depth analysis of the impacts of element doping，surface coating，high-entropy design，and multiphase design on the material performance was provided，and potential pathways for optimizing these modification approaches were discussed.Through analysis，these modification strategies were found to effectively address irreversible phase transition and low sodium-ion diffusion rate，thereby enhancing the cycling life and fast charging/discharging performance of sodium-ion batteries.Meanwhile，existing limitations，including the high cost of materials and complex synthesis processes，were highlighted in this paper，and perspectives on the future development of high-performance cathode materials for sodium-ion batteries were offered.

Phosphogypsum is a typical solid waste generated from the wet-process phosphoric acid industry.Its safe disposal and high value-added utilization have became critical research directions for the sustainable development of the phosphate chemical industry.Currently，phosphogypsum is primarily used in the production of building materials and supplemented by limited agricultural and chemical applications.However，these routes suffer from low economic efficiency and insufficient consumption capacity.Owing to its chemical reactivity，phosphogypsum can be transformed into functional materials，such as cementitious materials，thermal insulation materials，and adsorbent materials，which offer high value-added and large consumption potential.The current status of traditional phosphogypsum disposal pathways was firstly reviewed.Subsequently，it was focused on the preparation methods and applications of phosphogypsum-based functional materials.Specifically，partial cement was substituted by phosphogypsum-based cementitious materials，in which toxic elements were immobilized through physical encapsulation and chemical reactions.Consequently，these materials were utilized to fill mined-out areas.Phosphogypsum-based thermal insulation materials were characterized by lightweight，thermal insulation，acoustic insulation，and flame-retardant properties.Therefore，broad market prospects were anticipated for these materials.Moreover，phosphogypsum was employed as a low-cost adsorbent for treating wastewater contaminated with heavy metals.In this process，heavy metal ions were effectively removed through adsorption，precipitation，and ion exchange.Compared with conventional utilization pathways，phosphogypsum-based functional materials demonstrated significantly broader application prospects and greater development potential.

Resource utilization of heavy metal-contaminated soil is a key link in the field of soil remediation，among which the preparation of ceramsite by coupling heavy metal-contaminated soil with multi-source solid waste is an innovative approach to achieve waste-to-treat-waste.The research progress on preparation of ceramsite using heavy metal-contaminated soil as the main raw material and coupling it with solid wastes such as sludge，tailings，fly ash and red mud was systematically summarized.It was focused on analyzing the technical principles，process route，heavy metal solidification mechanisms and resource utilization advantages of ceramsite preparation by coupling heavy metal-contaminated soil with multi-source solid waste，revealed the potential pollution risks during the ceramsite preparation process，and put forward corresponding risk control strategies.The technology could realize physical encapsulation and chemical bonding fixation of heavy metals through high-temperature sintering，and endow ceramsite with properties such as light weight，high strength and porous adsorption，thus enabling it to have broad application prospects in construction，water treatment，landscaping and other fields.However，current technologies still faced challenges such as poor compatibility of multi-source solid wastes，high process energy consumption and risks of heavy metal secondary release.Future research needs to further optimize raw material compatibility，reduce energy consumption，and improve the risk assessment system，so as to promote the standardized and large-scale application of this technology.

Membrane distillation technology has broad application prospects in the field of water treatment.However，in the long-term treatment of complex systems containing multiple pollutants，it is difficult for conventional membranes to avoid membrane fouling and wetting.In order to improve the membrane distillation performance of hydrophobic polyvinylidene fluoride（PVDF） membrane，the superhydrophobic modified membrane of F-Si-PCPA-PVDF was prepared by mussel-inspired coating（PCPA） assisting loading of fluorinated silica（F-SiO₂） nanoparticles.The morphology，chemical composition and wetting properties of the modified membrane were characterized，and its membrane distillation performance was investigated by direct contact membrane distillation（DCMD） device.The results demonstrated that the F-Si-PCPA-PVDF membrane exhibited superior hydrophobicity with a high water contact angle of（168.8±0.6）° and low water sliding angle of 2.8°，along with exceptional anti-fouling and anti-wetting capabilities in simulated seawater systems containing typical contaminants such as calcium carbonate（CaCO₃），humic acid（HA），mineral oil（MO），and sodium dodecyl sulfate（SDS）.In the system containing 0.05 mmol/L SDS，the flux of PVDF membranes was declined by 24.27% during the 8 h membrane distillation process.In contrast，the modified membrane maintained a stable flux of （26.97±0.49） kg/（m²·h） while sustaining salt rejection rates above 99.99% throughout the process.

To enhance the value of calcium carbonate and develop its new application market，antibacterial nano-CaCO₃@TiO₂@Ag composites were fabricated by a two-step method using butyl titanate and silver nitrate as shell materials.The effects of reaction temperature，stirring speed，Ag loading capacity，reaction time，and aging time on the silver loading effect and loading mechanism were investigated.The products were characterized by transmission electron microscopy（TEM），scanning electron microscopy（SEM），energy dispersive X-ray spectroscopy（EDS），X-ray diffraction（XRD），X-ray photoelectron spectroscopy（XPS） and Fourier transform infrared spectroscopy（FT-IR）.The results showed that the optimal loading conditions for Ag were as follows：reaction temperature of 30 ℃，stirring speed of 350 r/min，Ag loading capacity of 10%（mass fraction），reaction time of 80 min，without aging time.Under the optimized loading conditions，amorphous TiO₂ was uniformly loaded on the surface of nano-calcium carbonate by forming Ca—O—Ti chemical bonds to form CaCO₃@TiO₂.Then Ag⁺ was adsorbed and reduced under the action of organosilicon molecules to produce 5~10 nm silver particles coated on the surface of CaCO₃@TiO₂，and nano-CaCO₃@TiO₂ @Ag core-shell structure was obtained.The antibacterial tests demonstrated that the antimicrobial performance of nano-CaCO₃@TiO₂@Ag in powder coatings met the class I standard as outlined in GB/T 21866—2008 “Test method and effect for antibacterial capability of paints film”.

The Lop Nur region hosts certain reserves of sulfate-type sedimentary salt deposits.Although its potassium content is not high，it still possesses value for development and utilization.Crystal structure analysis was conducted on this sulfate-type sedimentary salt deposits，along with experimental studies on potassium extraction via leaching.The results indicated that the ore was primarily composed of NaCl and contained substantial amounts of sulfates and their double salts，such as magnesium sulfate，mirabilite，gypsum，polyhalite，kainite，and minor carnallite.The content ranges were 1.9% to 5.3% for K⁺，4.2% to 6.9% for Mg²⁺，and 17.1% to 30.2% for SO₄²⁻（all by mass）.Leaching experiments employing raw brine from Lop Nur，process brines from different stages of potassium sulfate production using Lop Nur salt lake brine，various saturated brines，and deionized water revealed that the raw Lop Nur brine was the superior leaching agent for potassium extraction from this salt deposits.A high sulfate ion content in the leaching agent favored K⁺ dissolution.Among the leaching parameters，the liquid-to-solid ratio exerted the most significant influence on the potassium leaching rate，followed by leaching temperature，with leaching time having the least effect.The optimal leaching conditions using raw Lop Nur brine were liquid-to-solid ratio of 2.0，temperature of 25 ℃，and duration of 45 min.Under these conditions，the K⁺ leaching rate reached 87.6%，and the K⁺ content in the leachate was increased to 2.53 times that of the original brine.These findings provided theoretical support and data for the development and utilization of potassium from sulfate-type sedimentary salt deposits.

In order to explore more utilization approaches of coal gangue and achieve the goal of “treating waste with waste”，in this study，coal gangue was taken as raw material to successfully synthesize the high-molecular composite coagulant，polyaluminium magnesium zinc chloride（PAMZC），through a series of steps，including high-temperature calcination，hydrochloric acid leaching，doping with magnesium and zinc elements，polymerization，and aging.The effects of n（Zn）/n（Al），n（Mg）/n（Al），polymerization pH value and polymerization time on the coagulation performance of PAMZC were explored.FT-IR，XRD，SEM and point-scan spectroscopy were used to characterize the structure and morphology of PAMZC.The results showed that when n（Zn）/n（Al） was 0.25，n（Mg）/n（Al） was 0.15，polymerization pH value was 2.25 and the polymerization time was 4 h，PAMZC had the best coagulation performance.The turbidity of the effluent after coagulation was decreased to 0.97 NTU，and the removal rates of turbidity and total phosphorus reached 99.18% and 88.85%，respectively.FT-IR and XRD indicated that a polymerization reaction occurred among zinc，magnesium and aluminum elements，resulting in the formation of high-molecular polymers with a relatively high degree of polymerization.The SEM results showed that the surface of the structural units of PAMZC was uneven，with intricate pores formed，increasing the number of adsorption vacancies，which was beneficial for enhancing the coagulation performance.PAMZC performed well in the removal of turbidity and total phosphorus，and its effect was significantly better than that of the commercially available PAC.Therefore，PAMZC was also regarded as an efficient phosphorus removal agent.

The specific surface area of MgO is small，and the number of basic sites is limited.The CO₂ adsorption capacity of the MgO is significantly lower than its theoretical potential.Following CO₂ adsorption，MgO tends to become compact，which negatively impacts its cycling stability.Consequently，enhancing the activity and pore structure of MgO and improving its cycling stability are pressing issues for the application of MgO as a CO₂ adsorbent.MgO-based adsorbents were prepared using a solid-phase calcination method combined with NaNO₃ doping，with bischofite and carbide slag as the raw materials.The effect of NaNO₃ doping on the structure and adsorption-desorption performance of the MgO-based adsorbents was investigated through experimental testing and density functional theory.The results indicated that MgO-based adsorbents produced via solid-phase calcination exhibited a low CO₂ adsorption rate.However，the CO₂ adsorption rate of the MgO-based adsorbents doped with NaNO₃ reached a maximum of 24.26%.MgCO₃ was formed and covered on the surface of the MgO-based adsorbent doped by NaNO₃ after CO₂ adsorption.Following CO₂ desorption，the main component of the MgO-based adsorbent became MgO.Notably，the NaNO₃ within the sample remained unchanged after CO₂ adsorption and desorption cycles.Density functional theory calculations revealed that doping with NaNO₃ resulted in a CO₃^2- peak after CO₂ adsorption，and the maximum adsorption energy of CO₂ on the MgO surface was -1.587 eV.MgCO₃ generated on the MgO surface and the doping with NaNO₃ could promote the adsorption and desorption performance of MgO for CO₂.This research offered significant methodological insights and data support for the development of MgO-based adsorbents，holding both substantial academic research significance and practical application value.

Addressing the resource utilization of chicken manure and the management of cadmium pollution in wastewater，using chicken manure as raw material，after synergistic treatment with wet phosphoric acid and potassium hydroxide，biochar（CMBC） was prepared by limited oxygen pyrolysis at 300，500，and 700 ℃ respectively.Fundamental properties of the biochar were analyzed using elemental analysis，specific surface area and pore size distribution analyzers，Raman spectroscopy，X-ray fluorescence（XRF），and Fourier transform infrared spectroscopy（FT-IR）.The adsorption properties and mechanisms of biochar for Cd²⁺ were investigated.The results indicated that when the pyrolysis temperature was increased from 300 ℃ to 500 ℃，significant changes occurred in the physicochemical properties of biochar，including yield，ash content，elemental composition，and pore structure.The specific surface area of CMBC500 reached 141.64 m²/g，with a total pore volume of 0.141 1 cm³/g and an average pore diameter of 4.82 nm，demonstrating that higher pyrolysis temperatures were more conducive to adsorption.Notably，CMBC500 exhibited a maximum adsorption capacity of 99.28 mg/g.However，further increasing the pyrolysis temperature from 500 ℃ to 700 ℃ resulted in minimal changes in both the physicochemical properties and adsorption capacity of the biochar.The adsorption process of Cd²⁺ onto biochar was followed the Elovich equation and Sips model，suggesting a non-homogeneous adsorption process involving diverse mechanisms.With the increases of the initial solution pH，the adsorption capability of Cd²⁺ of biochar was improved.The presence of Ca²⁺ and Mg²⁺ also led to a reduction in adsorption capacity.Based on the adsorption experiment，the adsorption of Cd²⁺ by CMBC was mainly physical adsorption，supplemented by chemical adsorption such as electrostatic interaction，ion exchange，and functional group complexation.

Chromium slag is the solid waste generated during the production of chromium salts from chromite.After deep extraction of chromium and aluminum from the chromium slag，a low-chromium slag is obtained.This low-chromium slag mainly contains valuable metal elements such as iron and magnesium，and has significant recovery value.In order to address the challenge of resource utilization of low-chromium slag， an ammonium sulfate roasting-acid leaching process was proposed.The experiment used ammonium sulfate as the roasting agent.Based on the different thermal decomposition characteristics of MgSO₄ and Fe₂（SO₄）₃ at high temperatures，by precisely controlling the roasting temperature，efficient and selective extraction of magnesium was achieved，while simultaneously promoting the stabilization and enrichment of iron.The results showed that under the optimal process conditions of a baking temperature of 700 ℃，a baking time of 40 min，an ammonium sulfate dosage of 1.5 times the theoretical amount，an acid leaching time of 30 min，and a stirring speed of 500 r/min，the extraction rate of magnesium reached 99.38%，and the mass fraction of iron oxide in the magnesium extraction residue phase exceeded 90%，providing a basis for the high-value utilization of iron.This process enabled efficient separation of magnesium and iron from the low-chromium slag.It provided technical support for the comprehensive utilization of multiple metal elements in chromium slag，and was of great significance for promoting the development of circular economy and reducing environmental pollution.

The phase transformation and influencing factors during the dissolution-recrystallization process of α-hemihydrate gypsum（α-HH） prepared from dihydrate gypsum（DH） via hydrothermal synthesis under saturated vapor pressure conditions were investigated，providing a reference for the hydrothermal preparation of α-HH from phosphogypsum（PG）.Various gypsum sources were employed to examine the effects of heating rate，composition，and pH on the phase transition process，with XRD and SEM used to analyze the crystal transformation.The results indicated that an optimal heating rate of 0.1 ℃/min was determined for the hydrothermal conversion of PG.Within the temperature range of 108~130 ℃，the solubility of CaSO₄ in natural gypsum，washed PG，raw PG，and lime-modified PG generally exhibited an initial gradual increase followed by a decrease before stabilizing，with the phase transition occurring near 118 ℃.At the same holding temperature，raw PG demonstrated slower dissolution-recrystallization rate and lower conversion efficiency compared to natural gypsum and washed PG，whereas lime-modified PG exhibited dissolution-crystallization behavior similar to that of washed PG.Water-soluble impurities in PG were identified as the primary factor hindering the dissolution-recrystallization process. Pretreatment methods such as water washing or lime neutralization could modify the PG′s phase transition behavior to resemble that of natural gypsum.

In response to the challenging issue of treating high-concentration chloride-containing wastewater generated during the production of monopotassium phosphate（MKP），a method for removing chloride ions from wastewater using trioctylamine（TOA） as an extractant was proposed.The effects of factors such as extractant formulation，extraction phase ratio，temperature and time on chloride ion removal rate were investigated，and the conditions for countercurrent extraction stages and stripping were explored.The results showed that under the conditions of an extractant formulation with a volume ratio of TOA，isooctyl alcohol，and kerosene at 2∶1∶7，with a phase ratio of 1∶1，an extraction temperature of 25 ℃，and an extraction time of 10 minutes，chloride ion concentration in the wastewater was decreased from 7500 mg/L to 294 mg/L after three stages of countercurrent extraction，achieving a chloride removal rate of 96.08%.Using 5 mol/L ammonia solution for three stages of countercurrent stripping with a phase ratio of 6∶1，the stripping rate reached 95.43%.The extraction mechanism was analyzed using the slope method and infrared spectroscopy，revealing that the extraction process followed an ion association-ion exchange mechanism，with a chloride-to-TOA molar ratio of 1∶1 in the extracted complex.This study presented an effective method for removing chloride ions from MKP production wastewater，preventing corrosion of equipment during subsequent treatment stages and providing a new approach for the treatment of chloride-containing wastewater in MKP production.

At present，the mainstream method for determining the mass concentration of fluoride ions in solutions is the fluoride ion selective electrode method，which is widely recognized for its advantages of simple operation，rapidity and high accuracy.However，when it is directly applied to the fluorine-containing solution with complex components produced during the treatment of hazardous waste in the aluminum industry，the accuracy will be greatly reduced.In order to improve the measurement accuracy，the prepared standard fluorine-containing solution was used as the research object to study the influence of the total ionic strength adjustment buffer（TISAB） on the analysis results. It was found that the appropriate dosage of TISAB was influenced by the concentrations of fluoride and aluminum ions in the solution.For solutions free of ions that could complex with fluoride，the volume ratio of the sample solution to TISAB could be set at 1∶0.5 for the preliminary test.Based on the preliminary test results，the ratio for the formal measurement could be adjusted by referring to the rule of the optimal volume ratio of different fluoride ion concentrations to TISAB.For solutions containing ions such as aluminum that could form complexes with fluoride，it was necessary to analyze the aluminum ion concentration and determine the dosage of TISAB to be added prior to the measurement.For solutions with an aluminum ion mass concentration higher than 120.0 mg/L，the aluminum ion mass concentration could be diluted to 120.0 mg/L，and the measurement could be performed with the volume ratio of the sample solution to TISAB of 1∶1.If the aluminum ion concentration was high while the fluoride ion concentration was too low，making excessive dilution inappropriate，the aluminum ion mass concentration could be diluted to 240.0 mg/L and the volume ratio of the sample solution to TISAB could be set to 1∶2，with a positive deviation of 4.50% added to the measured results.This method could control the error within 2.00% in the measurement of complex fluorine-containing solutions，and it provided a reference for the accurate determination of other fluorine-containing solutions with complex components.

To solve the problems of difficult separation and insufficient cycle stability of traditional homogeneous polyoxometalate catalysts in iodine ion oxidation reactions， a highly efficient and recyclable green heterogeneous catalyst was developed.The magnetic chitosan composite catalyst MNPs/CS/PMo₁₁V was prepared by using Keggin-type vanadium substituted polyoxometalate H₄PMo₁₁VO₄₀（PMo₁₁V） as the active component and magnetic modified chitosan（CS） as the carrier.The composites were characterized by PXRD（X-ray powder diffraction），FT-IR（Fourier transform infrared spectroscopy），SEM（scanning electron microscope），EDS（X-ray energy dispersive spectrometer），TGA（thermogravimetric analysis），and VSM（vibrating sample magnetometer）.The catalytic oxidation of iodide ion（I^-） was investigated，and the kinetics were analyzed.The experimental results showed that the catalytic activity of the catalyst was 40 times higher than that of the blank，and the catalytic reaction conformed to the quasi-first-order kinetic model.Under the condition of c（H₂O₂）=2.0×10^-3 mol/L，c（I^-）=2.5×10^-3 mol/L，the optimum temperature T=55 °C，pH=2.0，the conversion rate of iodide ion could reach 99.68% in about 80 s.The prepared green catalyst could achieve rapid and simple magnetic separation and recovery within 30 s by applying an external magnetic field， and it still had good catalytic activity after 40 cycles of regeneration.Therefore， the prepared MNPs/CS/PMo₁₁V had excellent cycle stability and could efficiently catalyze iodine ions to produce iodine， which had certain application potential in industrial iodine recovery.

The development of high-performance catalysts play curial role in the field of CO₂ hydrogenation to methanol，however，the formation conditions of crystal phases of catalyst precursors and their corresponding relationships with catalytic performances remain unclear.A series of Cu/ZnO/Al₂O₃ catalysts synthesized at different precipitation temperatures were prepared by co-precipitation method.The prepared catalysts were characterized by XRD，SEM，BET，H₂-TPR and CO₂-TPD.Meanwhile，the catalytic performances of the prepared catalysts in CO₂ hydrogenation to methanol was also investigated in the fixed bed setup.The results indicated that the precipitation temperature had significant effects on the crystal structure，microstructure and interaction of Cu-ZnO species.Low temperature precipitation was conducive to the formation of aurichalcite phase of catalyst precursors and smaller crystalline size.Higher precipitation temperature was conducive to the formation of malachite phase and generating more Cu-O-Zn sites in the catalyst，which were regarded as the active sites for CO₂ hydrogenation to methanol.The catalytic performance of Cu/ZnO/Al₂O₃ catalyst for hydrogenation of carbon dioxide to methanol was probably determined by the catalyst crystalline size and copper-zinc interface.The optimal precipitation temperature was 70 ℃ within the scope of this investigation.Under the reaction conditions of 240 ℃，5 MPa，GHSV of 10 000 mL/（g·h），and feed gas composition of V（CO₂）∶V（H₂）∶V（N₂）=23.5∶70.5∶6（volume ratio），CZA-70 catalyst，which was prepared at optimal precipitation temperature，showed 23.8% of CO₂ conversion，60.9% of methanol selectivity and 0.48 g/（g·h） of methanol space time yield.