The leachate obtained from the oxidation leach of nickel-cobalt-iron powder with sulfuric acid was taken in the study for preparing iron phosphate. After potential adjustment, Al³⁺ and Cr³⁺ in the leachate were removed by neutralization and precipitation to achieve an efficient separation of Fe²⁺ and Al³⁺. The purified solution was then oxidized and used to prepare ferric phosphate hydrate by iron precipitation with phosphoric acid. Finally, the purified Ni-Co-rich solution was used to prepare nickel-cobalt hydroxide. It is found that firstly, with pH of the leachate at 4.5, 10 min of reaction at 25 ℃ can lead to the removal rates of Al and Cr reaching 100% and 97.15%, with loss rate of Fe at 2.42%; secondly, the obtained purified solution is subjected to 10-min iron precipitation at 25 ℃ with pH of 2.1, resulting in iron precipitation rate of 97.30%, loss rates of Ni and Co at 0.36% and 0.64%, respectively; the precipitate, amorphous iron phosphate with water of crystallization, is then subjected to 2-h calcination at 700 ℃ and converted to anhydrous FePO₄, with both impurity content and iron-phosphorus ratio up to the standard of type I anhydrous iron phosphate in HG/T 4701—2021.

Vanadium slag, as raw material, went through calcified roasting processes in the study, and the thermodynamics and kinetic analysis were conducted for verifying the roasting mechanism. The results show that calcified roasting process mainly includes iron oxidation, oxidative decomposition of olivine and spinel, as well as calcification. Based on theoretical and data analysis, calcium-containing phases are formed in the following sequence: CaV₂O₆, Ca₂V₂O₇, Ca₃V₂O₈, CaSiO₃. At a high temperature, excess CaO reacts with vanadium to generate Ca₃V₂O₈ and CaSiO₃. The oxidation and calcification processes of vanadium spinel are controlled by a third-order reaction, and the apparent activation energy is 282.45 kJ/mol. In the leaching experiment, the leaching rate reaches the maximum after roasting at 860 ℃ for 120 min, which is consistent with the results obtained from theoretical analysis of calcified roasting process.

For recovering the cobalt in a sulfur-cobalt concentrate mainly occurring as isomorphism in pyrite and magnetite, an experimental study was carried out by adopting roasting and leaching process. The results show that the sulfur-cobalt concentrate, at the fineness of -0.074 mm 80%, was firstly roasted at 620 ℃ for 3 h by adding sodium sulfite as an aid at an amount of 5% of the mass weight of sulfur-cobalt concentrate, and then leached for 2 h at 90 ℃ with sulfuric acid at an amount of 20% of the mass weight of sulfur-cobalt concentrate, liquid-solid ratio of 2∶1, leading to a cobalt leaching rate of 85.85%. It is found that sulfur-cobalt concentrate is transformed into hematite after oxidizing roasting, and cobalt in the roasted ore mainly exists in the form of cobalt oxide and cobalt sulfate.

A process for continuous producing lithium carbonate from spodumene was presented based on the processing technique including converting natural spodumene into β-spodumene for roasting, and sulphation roasting. Aspen Plus software was adopted to simulate the whole production process, with the parameters optimized as follows: H₂SO₄ and Li₂O in a molar ratio of 1.1, liquid-solid ratio of 2.0, and temperature for lithium precipitation at 85 ℃. Under the above conditions, lithium carbonate product can be finally produced with purity of 99.55% (in a mass fraction), presenting lithium recovery rate at 87.7%. The energy consumption of natural gas, pure water and steam is 0.42, 6.64 and 0.72 per unit of lithium carbonate product respectively.

Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the micro-mass change during the gold leaching process for exploring the variation of gold leaching rate in cyanide solution. It is found that with a cyanide ion concentration of 55.2 mg/L and the dissolved oxygen concentration in the system increased from 1.5 mg/L to 8.5 mg/L, the leaching rate of gold can be increased from 430.9 ng/(cm²·min) to 514.8 ng/(cm²·min), up 19.5%; with the dissolved oxygen at the mass concentration of 8.5 mg/L, an increase in the cyanide ion concentration from 22.6 mg/L to 55.2 mg/L can lead to the gold leaching rate up to 514.8 ng/(cm²·min) from 60.1 ng/(cm²·min), presenting a 7.6-fold improvement. It is concluded that the gold-leaching rate has something to do with the ratio of cyanide ion concentration to dissolved oxygen concentration . The gold leaching rate is higher with at the room temperature.

In order to clarify the mass transfer law in the process of salt conversion into corresponding acid and base by introducing bipolar membrane and thus to instruct industrial production with it, a model of electrodialysis unit cell with Na₂SO₄ as the raw material was constructed by introducing bipolar membrane (BPM) based on Nernst-Planck and Poisson equations. Key parameters including the number of grids and the capacity of membrane groups of the unit cell were obtained by calculating with COMSOL Multiphysics software. The salt conversion rates in the unit cell with different voltage and feed concentration were calculated based on simulation, and then compared with the experimental data. The results show that with the grid number of 30 000 and the membrane group capacity of negative/positive membrane at 300 mol/m³, the simulated results with the constructed model are in good agreement with the measured data. Based on the corresponding calculation, data of potential distribution, ion distribution and distribution of ion migration flux in the unit cell during mass transfer process were obtained. It is found that the mass transfer rate and energy efficiency of Na₂SO₄ converted into corresponding acid and base by bipolar membrane are mainly influenced by voltage drop and membrane voltage in the unit cell.

An experiment was carried out for extraction of zinc from the tailings of lead flotation by adopting sulfuric acid leaching, and effects of grinding fineness, addition of sulfuric acid, leaching temperature, leach time, stirring speed and liquid-solid ratio on zinc leaching rate were investigated. The results show that the lead flotation tailings with the grinding fineness of -0.074 mm 75% are subjected to 1.5 h leaching at 60 ℃ by adding 15% sulfuric acid with stirring speed at 200 r/min, liquid-solid ratio of 3.0 mL/g, resulting in zinc leaching rate of 90.71%. The obtained leachate has Zn at the concentration of 18.94 g/L, and high content of Cd, Fe, Mn, Ca and Mg, which needs attention in the subsequent purification and enrichment operation.

The effects of continuous and semi-continuous synthesis processes of precursor on the structure and performance of precursor materials and nickel-rich NCM cathode materials were explored. The results show that primary particles of the precursors synthesized by these two processes are quite different in morphology, leading to the difference in structure of primary/secondary particles and electrochemical property of the correspondingly synthesized cathode materials. These two cathode materials present little different performance in a button half cell, but significant difference in a soft pack battery. The nickel-rich cathode synthesized by the semi-continuous process has a lower impedance at a low state of charge, and retains 87.61% of its capacity after 750 cycles at 45 ℃, much higher than the retention rate (77.65%) of the nickel-rich cathode synthesized by the continuous process. It is concluded that the semi-continuous synthesis process for precursor is superior in the production of nickel-rich cathode materials.

The effects of different solid solution time on the mechanical properties, intergranular corrosion (IGC) and microstructure of an Al-Cu-Mg-Ag alloy were investigated by performing tensile testing, IGC tests, and electrochemical corrosion analysis, as well as using transmission electron microscopy, scanning electron microscopy and electron backscatter diffraction techniques. Results show that increasing the solution time from 5 min to 120 min leads to a gradual dissolution of residual second phase and a gradual increase in the size and quantity of Ω phase, contributing to a remarkable improvement in mechanical properties. Meanwhile, the IGC resistance of Al-Cu-Mg-Ag alloy is found to be considerably degraded as solution time is prolonged. The potential difference between the precipitation free zone (PFZ) and the matrix is the decisive factor in accelerating the IGC rate, while the PFZ width has no obvious influence on IGC resistance.

ZL101 alloy was modified by using mechanical stir casting process with an addition of rare-earth Yb at the mass fraction of 0-0.9%, for investigating the effect of Yb content on the microstructure and corrosion resistance of ZL101 alloy. The results show that with the addition of rare-earth Yb at a mass fraction of 0.6%, ZL101 alloy has its α-Al phase changed from coarse dendritic structure without modification to spheroidal dendrite with fine size, regular shape and regular arrangement, also the eutectic Si phase changed from the coarse long strip and needle sheet to the granular and short rod. It is shown that Yb reacts with Al substrate to form Al₃Yb rare-earth phase with long strip structure. With the addition of Yb at 0.6%, ZL101 alloy has its corrosion rate at 13.25 mg/(cm²·d), 37.23% lower than that before the addition of Yb. It can be seen from the corrosion surface observation that increasing Yb content leads to gradual decrease in the number of corrosion products and pits on the corrosion surface of the alloy.