Chlorine is a harmful element in the process of zinc hydrometallurgy. During zinc electrodeposition, it will corrode plates and equipment and release toxic gases such as chlorine, resulting in increased production cost and environmental pollution. The sources of chlorine elements in the process of zinc hydrometallurgy and its hazard to the process of zinc hydrometallurgy are briefly introduced. The research and development status, advantages and disadvantages of the main chlorine removal processes such as chemical precipitation, extraction and ion exchange are summarized, and the main research and development directions in the future are pointed out.

Monoclinic lithium vanadium phosphate(Li₃V₂(PO₄)₃, LVP) is considered to be one of the most potential lithium ion battery cathode materials, with high capacity, good safety, long service life, excellent low temperature function and other advantages. However, the low electronic and ionic conductivity of LVP has limited its development. In this paper, the structure and electrochemical reaction mechanism of LVP cathode materials are introduced, the main preparation methods and modification research progress of LVP cathode materials are reviewed, and the future development direction and application prospect of LVP cathode materials are prospected.

As an important secondary resource rich in Nd, Pr, Dy and other rare earth elements, the recycling of NdFeB permanent magnet waste is not only related to the supply security of rare earth strategic resources, but also has great significance for reducing environmental pollution and promoting sustainable development. The source, basic physical and chemical characteristics of NdFeB permanent magnet waste and the recycling technology of rare earth elements are summarized. The basic principles and research progress of fire, wet and other recycling processes are reviewed. The advantages and disadvantages of the technology are analyzed. The future development direction of NdFeB waste recycling rare earth technology is prospeced, in order to promote the technological progress and sustainable development in this field.

Leaching solution with a mass concentration of 256.1 mg/L was obtained by using aqua regia to recover the gold from the CPU, and the gold in the acid leaching solution was recovered by solvent extraction. The effects of extractant type, concentration, extraction time, extraction phase ratio and extraction temperature on the gold extraction were investigated. The results show that with 80% dibutylcarbitol as the extraction agent, the gold extraction rate can reach 99.86% under the condition of V_O∶V_A=1∶4 and room temperature for 10 min. The sponge gold product can be obtained by stripping with oxalic acid. The recovery effect is good. The method has a certain popularization value in the comprehensive recovery of gold-containing electronic solid waste such as CPU.

The recovery of valuable components from waste ternary lithium batteries and the regeneration of electrode materials were systematically studied. The recovery of valuable components such as Ni, Co, Mn and Li was carried out by using the route of acid leaching—impurity removal—co-precipitation—high temperature solid phase synthesis. The effects of H₂SO₄ concentration and H₂O₂ adding dosage on acid leaching were investigated. The pH of the leaching solution was adjusted by NaOH to remove Fe²⁺ and Al³⁺ impurities, and then the cathode material precursor of ternary lithium battery was synthesized and the active material of the precursor was regenerated, and the electrochemical properties of the regenerated cathode material were discussed. The results show that the leaching rates of Ni²⁺, Co²⁺, Mn²⁺ and Li⁺are 99.7%, 99.1%, 97.2% and 99.5%, respectively, using 0.3 mol/L H₂SO₄ and 8%H₂O₂ as acid leaching agents. Under the condition of pH=4.5~6.5, it can completely precipitate and remove impurities such as Fe²⁺ and Al³⁺, and Ni²⁺, Co²⁺ and Mn²⁺ can be completely precipitated to obtain precursors as the pH rises to 10.0. The cathode material can be regenerated by adding lithium source. The electrochemical performance test results show that at 1 C current density, the specific capacity of ternary lithium battery can reach 143.7 mAh/g for 1 discharge cycle. The performance is stable after 100 cycles, and the CV curve has obvious redox peaks, and the cyclic discharge performance is good at different rates.

In order to comprehensively recover the valuable components from decommitted high-nickel ternary lithium batteries,lithium was selectively extracted by sulphation roasting and water leaching, and the water leaching residue was then processed by aging leaching,impurity removal and coprecipitation to prepare nickel-cobalt-manganese hydroxide. The results show that the optimum conditions of sulfation roasting are n(H₂SO₄)∶n(Li)=1.4∶1, roasting temperature of 600 ℃, roasting time of 1 h, and the water leaching rate of Li, Mn can reach 94.36%, 11.03%, respectively, Ni and Co hardly leaching. Under the conditions of acid-ore ratio of 1.74, curing temperature of 120 ℃, curing time of 120 min and liquid volume to solid mass ratio of 7.5 mL/1 g, the aqueous leaching slag is cured and acid leaching. The leaching rates of Li, Ni, Co, Mn, Cu, Fe and Al are 97.86%, 89.16%, 95.09%, 100%, 63.6%, 99.71% and 56.76%, respectively. Under the optimum conditions of pH=3.38, precipitation temperature of 60 ℃ and precipitation time of 60 min, the precipitation rates of Fe, Al and Cu in the solution can reach 100%, 98.07% and 82.51%, respectively. Nickel cobalt manganese hydroxide can be formed by co-precipitation after pH adjustment. Under the optimal conditions of pH=9.44, co-precipitation temperature of 55 ℃ and co-precipitation time of 120 min, the precipitation rates of Ni, Co and Mn can reach 99.6%, 100% and 98.72%, respectively.

In view of the "bimodal" particle size distribution phenomenon of U₃O₈ raw materials, the process concept of rapid dissolution of fine U₃O₈ and continuous dissolution of large U₃O₈ at the bottom of the equipment was put forward, and a tank-type continuous dissolution device was designed. The rationality of the proposed tank-type dissolution device, the feasibility of the continuous dissolution process of U₃O₈ in nitric acid, and its applicability to different raw materials were verified through micro, small-scale,and pilot tests. The results show that under the conditions of the nitric acid concentration of 6 mol/L, dissolution temperature of approximately 60 ℃, and residence time of 40 minutes, U₃O₈ from different sources can be effectively dissolved, the uranium mass concentration in the dissolution solution is 350~400 g/L.

The extraction of lithium from fly ash by roasting activation with sodium carbonate and leaching with sulfuric acid was studied. The effects of mass ratio of fly ash to sodium carbonate, roasting temperature, roasting time, liquid-solid mass ratio, sulfuric acid concentration, acid leaching temperature and acid leaching time on the leaching rate of lithium were investigated. The dynamic analysis of the leaching process was carried out by using the core-shrinkage model. The results show that under the condition of 800 ℃, fly ash and sodium carbonate are mixed and roasted for 180 min according to the mass ratio of 1∶1, and then leaching with 2 mol/L sulfuric acid at 90 ℃ for 120 min, remarkable leaching effect can be obtained, and the leaching rate of lithium can reach 99.97%, the leaching process is mainly controlled by diffusion. The study has a certain guiding significance for the leaching and recovery of lithium from solid waste resources.

The environmental problems caused by the increase in the storage amount of red mud have seriously restricted the development of China's alumina industry, so it is increasingly important to strengthen the comprehensive utilization of red mud. The recovery of sodium and aluminum from the red mud of an aluminum plant in Yunnan by calcification-carbonization method was studied. The calcified and carbonized red mud was characterized by XRD and SEM-EDS. The results show that the optimum conditions of calcification are reaction temperature of 65 ℃, reaction time of 36 h, calcium-sodium ratio of 4/1 and liquid -solid mass ratio of 4/1.Under the conditions, the sodium oxide recovery is the highest, 59.94%. The optimum conditions of carbonization are reaction time of 3 h, reaction temperature of 110 ℃, liquid to solid mass ratio 5/1, carbon dioxide pressure of 1.1 MPa, and the aluminum recovery rate is 16.15%. The hydrated sodium aluminosilicate in the red mud is converted into hydrated garnet during calcification, and sodium is released. Hydrated garnets decompose into CaCO₃, CaSiO₃ and Al(OH)₃ during carbonization. The method can provide a new idea for comprehensive recovery and utilization of red mud.

The extraction performance of gallium in sulfuric acid solution with new alkyl hydroxamic acid DX201 and P204 was studied. The effects of extraction and stripping conditions on gallium extraction performance were investigated. The extraction and stripping isotherms were drawn. The results show that the single-stage extraction rate of gallium is 97.52% under the conditions of V_O/V_A=1/1, extraction temperature of 25 ℃ and extraction time of 15 min in sulfate solution with mass concentration of sulfuric acid of 20 g/L sulfate solution and organic phase composition of 10%DX201+15%P204+75%260^#solvent oil. Using 2.5 mol/L dilute sulfuric acid solution to strip gallium from supported organic phase, the single stage stripping rate of gallium is 94.21% under the conditions of V_O/V_A=2/1, stripping temperature of 25 ℃ and stripping time of 2 min. The extraction rate of gallium in 3-stage countercurrent extraction is 99.64%, and the extraction performance is stable.

The magnetic porous magnesium oxide(m-MgO) was prepared with nano-ferric oxide (Fe₃O₄) as the core and MgCl₂ as the magnesium source, and was used for adsorption of U(Ⅵ) in aqueous solution. The physicochemical properties of MgO and m-MgO were characterized by FT-IR, XRD, VSM and Zeta potential. The effects of solution pH, temperature, and oscillation time on the adsorption of U(Ⅵ) by MgO and m-MgO were investigated. The results show that the optimal conditions for uranium adsorption by MgO and m-MgO are pH=3.5, adsorbent dosage of 10 mg, and oscillation time of 720 min. The adsorption process conforms to the pseudo-second-order kinetic model and the Sips isotherm adsorption model, with a theoretical adsorption capacity of 454.16 mg/g, and the increase of temperature is conducive to the spontaneous adsorption. Therefore, m-MgO is expected to be used to separate and recover uranium from radioactive wastewater.

Electrolysis of Manganese using Ionic liquid choline chloride as additive instead of selenium dioxide, under simulated industrial electrolytic conditions was studied. The electrolytic products were characterized by SEM and XRD, and the electrochemical mechanism of the cathode was analyzed by cyclic voltammetry(CV) and cathode polarization curve(LSV). The results show that the electrolytic product with ionic liquid choline chloride as additive has smooth, dense surface, and has a metallic luster. The addition of choline chloride can promote manganese deposition and inhibit hydrogen evolution. Under simulated industrial electrolysis conditions, the current efficiency is up to 68.1%.

In order to improve the electrochemical performance of stannous sulfide(SnS) anode material for lithium batteries, SNSS/DA precursor was prepared by one-step hydrothermal method with niobium cation and selenium anion doped SnS, and then SNSS/C composite was prepared by heat treatment. The effects of carbon nanolayer and co-doping mechanism on the conductivity and battery cycle stability of SNSS/C composite were investigated. The results show that SNSS/C composites have good coating morphology and carbon coating structure, and the thickness of carbon nanolayer is 10~30 nm. By doping two elements, Nb and Se, the crystal volume can be increased, so that lithium ions can obtain a broader channel in the process of embedding/deembedding, and further enhance the conductivity of the material and the diffusion efficiency of lithium ions. The electrochemical performance of SNSS/C material is excellent, the specific discharge capacity of the first cycle is 814.6 mAh/g, and the Coulomb efficiency is 96.3%.

In order to develop a high efficiency, environmental protection, low energy consumption of heavy metal Cr (Ⅵ) adsorbent magnetic biochar (MBC) was obtained by co-precipitation reaction in a mixture of FeSO₄·7H₂O and FeCl₃·6H₂O with alkali modified biochar as the substrate. polyethyleneimine(PEI) was then used as an amination agent and glutaraldehyde was as a cross-linking agent to produce PEI-functionalized magnetic biochar composites(PEI/MBC) for Cr(Ⅵ) removal, PEI/MBC was characterized by SEM,XRD and FT-IR. The effects of solution pH, adsorbent dosage and competitive ions on the adsorption properties for Cr(Ⅵ) were investigated,the results show that the highest adsorption amount of 105.94 mg/g is achieved under the conditions of initial Cr(Ⅵ) concentration of 50 mg/L, an adsorbent dosage of 0.2 g/L, temperature of 30 ℃ and pH=2. The adsorption was affected by the changes of competitive anions and temperature, the quasi-second-order kinetic equation can well reflect the adsorption behavior of Cr(Ⅵ) on PEI/MBC, and the isothermal adsorption data is consistent with the Freundlich isothermal adsorption model, the adsorption of Cr(Ⅵ) is a spontaneous endothermic process, with ΔG<0, ΔS=144.82 J/(mol·K) and ΔH=39.84 kJ/mol.

The efficient removal of fluoride from zinc smelting waste acid by complex extraction using P204 as the extractant was investigated. The effects of concentration of fluorine and aluminum in aqueous phase, pH, extraction temperature and time on the extraction rate of fluorine and aluminum were examined, The resource utilization of aluminum fluoride was also discussed. The results show that under P204 concentration of 1 mol/L, Al³⁺ concentration in aqueous phase of 0.1 mol/L, F^- concentration of less than 0.025 mol/L, pH=3.0~3.5, extaction time of 8 min and room temperature, the extraction rate of fluorine can reach 96.18%. Using 1.0 mol/L sulfuric acid solution to strip of the fluorine-aluminum-loaded organic phase, the stripping rates for F^- and Al³⁺ are 81.88% and 39.39%, respectively. Cryolite can be obtained by precipitation of stripping solution, and the synthesis of cryolite is more favorable under the condition of pH=4.

The perchlorinated zinc ash contains zinc metal, a small amount of heavy metals and harmful elements chlorine. In order to reduce the chlorine content in the perchlorinated zinc ash, the removal effect of water washing and ammonia washing on the impurities in the perchlorinated zinc ash was compared and studied. The influence of ammonia concentration, liquid volume to solid mass ratio and washing temperature on the precipitation rate of zinc in the ammonia washing process was investigated by single factor test, and the optimal ammonia washing conditions were determined by orthogonal test. The results show that the removal rates of Cl, Na and K are more than 99% and the precipitation rate of Zn is 98.7% under the conditions of ammonia concentration of 0.05%, liquid volume to solid mass ratio of 6 mg/1 L and reaction temperature of 30 ℃.

An economic benefit optimization model for hydrometallurgical equipment control was established, and an optimization algorithm based on Double Deep Deterministic Q-Network (DDQN) model is introduced. At the same time, Residual Network is combined with residual network. ResNet's deep learning capability to realize the detection and early warning of abnormal equipment operation status. The simulation results show that the intelligent control algorithm can not only greatly improve the operating efficiency of hydrometallurgical equipment, but also enhance the stability and reliability of the system and improve the economic benefit of enterprises.