In order to reduce the content of impurities such as Cu, Fe, Zn and reduce the loss of Ni in crude nickel sulfate solution of copper electrolysis by-products, the process of selective precipitation of copper by Na₂S₂O₃—deep extraction of zinc removal iron—evaporation crystallization was studied for deep purification of the solution, and the key process parameters were optimized. The results show that the precipitation rate of Cu can reach 99.89% and the loss rate of Ni is only 1.22% using Na₂S₂O₃ as precipitator under the optimum conditions of Na₂S₂O₃ excess coefficient of 2.0, solution pH of 5.0, reaction temperature of 85 ℃ and reaction time of 2 h. Using P204 as extracant, the extraction rates of Zn and Fe can reach 99.87% and 99.98%, respectively, and the loss rate of Ni is 2.24% under the optimal conditions of pH=3.0, P204 volume fraction of 25%, saponification rate of 50%, V_O/V_A=1.5/1, extraction temperature of 25 ℃ and extraction time of 10 min. Electroplating grade nickel sulfate crystal products are obtained by evaporation and crystallization of the deeply purified nickel sulfate solution. The quality can meet the national standard GB/T 26524—2023 Class Ⅱ indicators, and can be used as high-quality raw materials for electroplating and other industrial uses.

Preparation of a novel imidazole-based functional resin using polystyrene-divinylbenzene copolymer as the support by chloromethylation reaction and imidazole modification was studied. Adsorption properties and selectivity for uranium by the resin from acidic waste solution were systematically investigated. The results show that the equilibrium adsorption capacity of imidazole-based functional resin is 58 mg/g for uranium containing acidic solution with pH=5 and uranium mass concentration of 90 mg/L. Additionally, the resin has good tolerance to nitrate and chloride ions and high adsorption selectivity for uranium. When the mass concentrations of nitrate and chloride are 20 g/L and 5 g/L, respectively, the uranium adsorption capacity can also reach 57 mg/g. When the mass concentrations of uranium and interfering ions in the solution were both 90 mg/L, the adsorption capacity of imidazole-based functional resin for uranium can reach 44 mg/g, while the adsorption capacity of any single interfering ion (A1³⁺, Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, K⁺, Na⁺) is less than 5.4 mg/g. Furthermore, 0.5 mol/L HNO₃ is used as desorption, the desorption rate is 99.83%.When the imidazole-based functional resin is used to adsorb the actual uranium-containing acid waste liquid from a mine, the adsorption capacity of uranium is 40.2 mg/g, which is superior to that of common 201×7 anion exchange resin.

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.

In response to the issue of low cobalt leaching rate from oxidized copper-cobalt ore in the Kambove mining area of Congo(DRC), the mineralogical characteristics of the ore were analyzed by Mineral Liberation Analysis (MLA), polarized light microscopy, and Scanning Electron Microscopy (SEM). Based on the findings, leaching of cobalt from the ore with sodium pyrosulfite, Fe powder and SO₂ as reducing agents was studied. The influence of different reducing agents and dosage on the leaching effect was investigated. The resluts reveal that the primary copper minerals in the ore are pseudomalachite, malachite, and libethenite, while the main cobalt minerals are copper-cobalt-bearing manganese oxide and heterogenite. The gangue minerals predominantly consist of siltstone, quartz, sericite, and chlorite. The occurrence states of copper and cobalt in the ore are complex, with cobalt minerals being fine-grained and mostly occurring as inclusions. The theoretical leaching rate of cobalt is calculated to be 92.82%. Compared with the three reducing agents, the leaching effect of SO₂ is better. Under the optimal conditions of liquid volume to solid mass ratio of 3∶1, sulfuric acid dosage of 26.7 g/L, SO₂ amount at 1.7 times the theoretical amount, reaction temperature of 38 ℃, and reaction duration of 3 h, the cobalt leaching rate can reach 85.48%, approaching the theoretical maximum. The research results can provide both theoretical and technical support for the efficient utilization of cobalt resources in the Kambove mining area of Congo(DRC).

To address the issue of the efficient separation and recovery of vanadium and gallium from acidic solution system, the physicochemical differences between V(Ⅴ) and Ga(Ⅲ) in the V(Ⅴ)-Ga(Ⅲ)-H₂O system were systematically examined. Through metallurgical thermodynamic simulations, concentration predominance diagrams and species predominance diagrams were generated. Combined with alkali titration experiments and Raman spectroscopy analysis, the optimal lg[C]_T-pH range for vanadium-gallium separation was determined. The results indicate that the ideal pH range is between 2 and 3. In the range, vanadium ions will form large-nucleus anions of vanadium polyoxometalates with a molar fraction of more than 90%, while gallium mainly exists in the form of small-nucleus cations, increasing the chemical state difference between vanadium and gallium in acidic solution system and effectively avoiding the formation of large-nucleus gallium hydroxide precipitates, which is conducive to the separation and recovery of vanadium and gallium in the enriched solution system.

Rare earth resources are easy to produce low concentration rare earth solution or very low concentration rare earth wastewater in the process of development and extraction, which causes problems such as enrichment difficulties, environmental pollution and resource waste. The sources and characteristics of common low concentration rare earth solutions are introduced, and the principles and research progress of enrichment and recovery technologies of low concentration rare earth solutions in recent years are reviewed, including precipitation, solvent extraction, membrane separation and adsorption separation. The advantages and disadvantages of various enrichment and recovery methods are analyzed, future direction for technological development are also outlined.

Magnesium desulphurization wastewater in copper smelting industry contains high concentration of heavy metal ions such as Cu²⁺ and Mg²⁺. The traditional "neutralization—flocculation" process has problems, such as high treatment costs, waste of heavy metal resources and great risk of environmental pollution. In view of the above problems, the two-step precipitation method of "sulfurization and impurity removal—sodium hydroxide precipitation" was studied to recover copper and magnesium from desulfurization wastewater. Firstly, Cu²⁺ was preferentially precipitated by precise placement of sodium hydrosulfide (1.1 times the theoretical amount) to form CuS. Secondly, sodium hydroxide is used to adjust pH and promote Mg²⁺ to produce magnesium hydroxide efficiently. The effects of pH, NaHS dosage, reaction temperature, reaction time and stirring speed on the recovery of copper and magnesium hydroxide were investigated. The results show that the recoveries of copper and magnesium hydroxide can reach over 95% under the optimal conditions. The process technology is feasible, not only reduces the discharge of heavy metals, but also the CuS formed can be used as raw materials for copper smelting production, and magnesium hydroxide can be reused in desulfurization system. A circular economy model of "pollutant treatment—resource regeneration—process closed loop" is constructed, which can provide technical reference for the recycling of wastewater in metallurgical industry.

To address the issue of low ion exchange adsorption performance of natural zeolite caused by the presence of impurities, which makes it ineffective in adsorbing ammonia nitrogen in wastewater, the modification of natural zeolite using inorganic acids, inorganic bases, and inorganic salts was studied. The effects of different initial ammonia nitrogen mass concentration, zeolite particle size, zeolite dosage and reaction time on ammonia nitrogen adsorption performance of natural zeolite were investigated. The adsorption effects of zeolite under different modification conditions on ammonia nitrogen were compared. The results indicate that the ammonia nitrogen adsorption rate of natural zeolite gradually decreases with the increase of zeolite particle size and initial ammonia nitrogen mass concentration, and gradually increases with the increase of zeolite dosage and reaction time. The ammonia nitrogen adsorption effect of zeolite modified by sodium chloride is significantly better than that of zeolite modified by inorganic acids and inorganic bases, as well as other inorganic salts. When the sodium chloride concentration is 0.8 mol/L, the ammonia nitrogen adsorption rate can reach 78.0%, which is 1.64 times that of natural zeolite.

The chemical composition, phase composition, and occurrence state of the main minerals in scheelite hydrochloric acid decomposition residue were systematically studied by a comprehensive mineral analysis system (TIMA), X-ray fluorescence spectrometer (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and other methods. The results indicate that the mineral particles in the hydrochloric acid decomposition residue of scheelite exhibit euhedral to subhedral to anhedral blocky structures. The primary phases identified are tungstic acid, fluorite, quartz, cassiterite, pyrite, molybdenite, arsenopyrite, and vivianite, with their respective mass fractions being 66.93%, 28.22%, 1.12%, 1.26%, 0.3%, 0.07%, 0.2%, and 0.04%. The grain size of tungstic acid is above 110 μm, while the grain sizes of fluorite, quartz, cassiterite, pyrite, molybdenite, and arsenopyrite are mainly concentrated between 5~20 μm. These particles are relatively fine and are either closely intergrown with tungstic acid or encapsulated by it.

The recycling of lithium cobaltate from waste lithium-ion batteries is of great significance for alleviating resource shortage and reducing environmental pollution. L-malic acid/ascorbic acid system was used as leaching agent to recover cobalt and lithium from waste lithium cobaltate batteries. The effects of L-malic acid concentration, ascorbic acid concentration, liquid volume to solid mass ratio, reaction temperature and time on the leaching rates of cobalt and lithium in lithium cobaltate were investigated. The leaching mechanism was discussed through kinetic analysis and SEM characterization. The results show that the optimal leaching conditions are L-malic acid concentration of 0.2 mol/L, ascorbic acid concentration of 0.1 mol/L, liquid volume to solid mass ratio of 0.3 mL/1 mg, reaction temperature of 70 ℃, leaching time of 1 h. Under the conditions, the leaching rates of cobalt and lithium are above 98%. The kinetic analysis shows that the leaching process is mainly controlled by external diffusion. The method is efficient and environmentally friendly, and can provide an important technical reference for the green recovery of lithium cobaltate in waste lithium-ion batteries.