The characteristics, industrial application status and research progress of hydrometallurgy for low grade laterite nickle ore by reduction roasting—normal pressure ammonia leaching and high-pressure acid leaching (HPAL), as well as the development of three generations of HPAL technology are summarized. The nickle-cobalt precipitation and enrichment technology and the application are introduced. The processes advantages and disadvantages of the H₂S precipitation, MgO precipitation, direct NaOH precipitation are analyzed. The effectiveness of new precipitation process with alkali conversion and crystal seed activation has been explored. The development prospect of laterite nickel hydrometallurgical process is also prospected.

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 leaching of silver from failed silver-containing spent catalyst using HNO₃+H₂O₂ system was investigated.The kinetics of the silver leaching process was analyzed using the shrinkage kinematics model of liquid-solid phase reaction.The effects of leaching temperature and nitric acid concentration on the leaching rate of silver were examined.The results show that under the optimal leaching conditions of nitric acid concentration of 1.1 mol/L,leaching temperature of 50 ℃,stirring speed of 300 r/min,n(H₂O₂)∶n(Ag)=1.5∶1,leaching time of 50 min,and liquid volume to solid mass ratio of 4 mL/1 g,the leaching rate of silver can reach 94.18%.The leaching is controlled by the diffusion of the solid film,and the apparent activation energy of the leaching reaction is 15.45 kJ/mol,and the reaction order of hydrogen ion is 1.13.The method can provide reference for the research of efficient resourcing utilization of silver-containing spent catalyst.

The process of synergistic leaching of lithium from waste lithium iron phosphate (LFP) and lithium cobalt oxide (LCO) battery cathode materials was studied, and the feasibility was analyzed by thermodynamics. The influence of various factors on synergistic leaching was investigated,and the leaching slag was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that LFP and LCO can synergistically leach lithium in an acidic system without adding any oxidant or reducing agent. The leaching rates of Li, Co, Fe and P in the cathode materials of waste batteries are 99.99%, 99.99%, 48.00% and 43.77%, respectively, under the optimal leaching conditions of sulfuric acid concentration of 0.7 mol/L, leaching temperature of 40 ℃, leaching time of 60 min, n(LCO)∶ n(LFP)=0.5 and liquid volume to solid mass ratio of 10 mL/1 g. The method can realize the purpose of recovering valuable metals from complex battery cathode materials under low acid conditions, and has certain popularization and application value.

Aiming at the dilute acid of copper smelting as raw material, the selective precipitation of copper and removal of arsenic with oxalic acid was studied. The effects of oxalic acid addition dosage, solution pH, stirring speed, reaction temperature and time on the separation of copper and arsenic were investigated. The results show that under the conditions of H₂C₂O₄/Cu molar ratio of 1.1, solution pH=0.4, stirring speed of 500 r/min, reaction temperature of 25 ℃ and reaction time of 30 min, the precipitation rate of copper is more than 98.5%, and the precipitation rate of arsenic is less than 0.20%, copper and arsenic can be separated efficiently.

In view of the problems of high energy consumption,high equipment requirements and low flexibility in recovering rhenium from processing waste by traditional pyrometallurgical processes,the electrochemical enhanced leaching—precipitation crystallization method was studied to recover high-purity KReO₄ crystals from rhenium secondary resources.The results show that when 22%~24% HNO₃ solution is used as the electrolyte,there is no obvious passivation during the electrolysis process,and the energy consumption is stable at about 3.0 kWh/kg.During the electrolysis,Re atoms at the hexagonal lattice sites on the anode surface lose electrons,combine with hydroxyl groups and transform through low-valent oxidation states of Re to bridge oxygen connected Re(Ⅱ),and finally enter the electrolyte in the form of \mathrm{R} \mathrm{e} {\mathrm{O}}_4^{-} after reacting with the acid.When potassium salt is used as the precipitant to recover Re elements in the electrolyte,under the conditions of crystallization temperature of 25 ℃,precipitant flow rate of 6 mL/min,stirring rate of 500 r/min and crystallization time of 30 min,the precipitated KReO₄ crystals are in the shape of polyhedral spindle,with good uniformity in particle size,high recovery rate and purity of 99.95%,which can meet the requirements for hydrogen reduction to prepare metallic rhenium.The method can effectively recover rhenium processing waste and has certain promotion value.

Solvent extraction is one of the main methods for rare earth separation and purification, but emulsification often occurs in industrial production due to improper control of process conditions. In order to solve the problem, the extraction of rare earth with the surfactant Span 80 as the regulator, P507 as the extractant and kerosene as the diluent was studied. The effects of aqueous pH, stirring speed and water-oil phase ratio on the extraction rate of Er³⁺ and the mass concentration of oil in the raffinate were investigated, and the process parameters were optimized by response surface method. The optimization results show that under the optimal conditions of aqueous pH=3.5, stirring speed of 130 r/min and water-oil phase ratio of 4∶1 for 5 min, the extraction rate of Er³⁺ can reach 95.42%, and the oil concentration in the raffinate is only 1.68 mg/L. The predicted value is in good agreement with the experimental results. The addition of Span 80 can effectively prevent emulsification, and the regulation effect is obvious.

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 efficient utilization of secondary silver-containing resources is of great significance for making up for the shortage of silver ore resources in China, alleviating the contradiction between supply and demand, and ensuring the supply security of national strategic metals. For waste Ag-Cu filler metal, the leaching and separation of copper and silver in the HCl-H₂O₂ system was studied, and high-purity AgCl was prepared. The influence of various factors on the separation effect of copper and silver was investigated. The results show that under the optimized conditions of H₂O₂ excessive coefficient of 1.3, HCl excessive coefficient of 1.4, liquid-solid mass ratio of 11∶1, leaching temperature of 40 ℃, and leaching time of 3 h, the leaching rate of copper can reach 99.38%. The leaching residue is irregular spherical particle with particle size of 2~4 μm. The main phase is AgCl, and the main components are Ag and Cl, with total mass fraction of more than 99%.

The extraction of iron from fly ash by HCl leaching and electrochemical deposition was studied. The micro-morphology and elemental composition of fly ash were systematically analyzed by SEM-EDS,XRF, ICP and XRD, and the key factors in the leaching process and their effects were investigated. The dynamic changes of pH, current density and Fe ion concentration during electrochemical deposition were also discussed. The results show that the iron leaching rate increased with the increase of HCl concentration, liquid volume to solid mass ratio, leaching temperature and leaching time. In the electrochemical deposition stage, pH increases gradually, while current density and Fe ion concentration decrease. The optimal leaching parameters are HCl concentration of 6 mol/L, liquid volume to solid mass ratio (HCl solution to fly ash) of 8∶1, reaction temperature of 90 ℃, reaction time of 90 min. For the electrochemical deposition process, the voltage is 3 V, the optimal pH range is between 0.5 and 1.9, and the final sediment is pure iron.