Recovery of magnesium from magnesium-containing wastewater and the preparation of high-purity magnesium oxide by ammonification carbonization method were studied. The effects of carbonization temperature, initial mass concentration of magnesium, CO₂ partial pressure, stirring speed, thermal decomposition temperature and time, and calcination temperature on the magnesium recovery process were investigated. The results show that under the conditions of carbonization temperature of 23 ℃, initial mass concentration of magnesium of 15.4 g/L, CO₂ partial pressure of 0.6 MPa and stirring speed of 560 r/min, the complete carbonization can be achieved by controlling the carbonization end point pH=7 and carbonization time 20 min. In the thermal decomposition stage, the basic magnesium carbonate with good crystal morphology can be obtained at 90 ℃ for 90 min. After further calcination at 700 ℃ for 2 h, the magnesium oxide product with high crystallinity and purity of 99.55% is finally obtained, and its performance can meet the standard requirements of 'industrial light magnesium oxide' (HG/T 2573—2012).

The treatment process of uranium purification and conversion waste liquid involves a continuous circulation system composed of neutralization, extraction, stripping and other units. Its stability is highly dependent on the precise control of small flow in each link, and it is easy to cause system overshoot and oscillation when the parameters of PID controller are adjusted by trial and error method based on experience, which leads to system disorder. In view of the above problems, it is proposed to establish a mathematical model with the key equipment ' lean organic phase pump ' as the control object. Five kinds of PID parameter tuning methods, such as classical Ziegler-Nichols (Z-N) method, improved Z-N method with set point weighting, optimal setting method based on ISTE criterion, critical proportional zone method and relay feedback self-tuning method, are compared and studied. The simulation analysis is carried out by MATLAB and Simulink, and the optimal method is applied to the field for experimental verification. The test results show that compared with the traditional Z-N method, the PI controller based on the optimal setting method based on the ISTE criterion performs best. When the field flow step changes, its key performance indicators are better than other methods, which can fully meet the strict requirements of the process flow. For the small flow control system in the treatment of uranium purification and conversion waste liquid, this method is used to adjust the PI parameters, which can effectively suppress overshoot, speed up response and ensure accuracy, and significantly improve the stability and reliability of the whole process. This study can provide a reference for the controller optimization of similar industrial processes.

The TiCl₃-K₂Cr₂O₇ redox titration method is used to determine the concentrations of Fe²⁺/Fe³⁺ in the solution after oxygen pressure leaching, neutralization, and iron removal of zinc hydrometallurgy. The results show that for samples with high iron concentrations (10-20 g/L), the relative error of this method is controlled within 2%, and the relative standard deviation (RSD) is less than 1%. For low iron concentration samples (around 1 g/L), the relative error remains below the permissible standard. The spike recovery test achieves a recovery rate of 100.1% with RSD of 0.32%. This method effectively improves the accuracy of endpoint judgment by accurately controlling the endpoint of 'tungsten blue'. The interference elements such as copper ions are separated by ammonia water, which reduces the influence of other metal ions on the determination. At the same time, a clear and simple two-step redox procedure is adopted:the excess Ti³⁺ is first oxidized with air to avoid the interference of titanium ions, so that only Fe²⁺ to be measured remains in the system, and then the titration is carried out with potassium dichromate. The titration end point is determined with sodium diphenylamine sulfonate as the indicator. The color of the solution changes from green to purple/blue, and the color change is sensitive and stable, which effectively reduces the subjective error, thus realizing the rapid and accurate determination of Fe²⁺/Fe³⁺ in complex polymetallic solution. This method is especially suitable for high-content iron systems, which can provide a reliable analysis method for zinc hydrometallurgy process control.

Vanadium-containing steel slag is an industrial waste rich in high-value elements and has significant secondary utilization value. Therefore, how to recover vanadium resources from steel slag at low cost and high efficiency is one of the key challenges that China's vanadium industry needs to overcome. The current research status of wet vanadium extraction technology from vanadium-containing steel slag is reviewed. The progress of calcination-leaching and direct leaching processes is introduced. Other new vanadium extraction processes and enhanced auxiliary methods for vanadium extraction are analyzed. Finally, the advantages and disadvantages of various processes are compared, and the future development trends are prospected.

The treatment and resource utilization of titanium-bearing blast furnace slag are the focus and difficult point of research on environmental protection for the iron and steel industry. The research progress on extraction of titanium from titanium-bearing blast furnace slag is reviewed, and the principle, process characteristics, treatment effects, existing problems, industrial prospects and environmental impact of sulfuric acid leaching, hydrochloric acid leaching, organic acid leaching, ammonium sulfate melting, ammonium chloride roasting, alkali melting methods for treatment of titanium-bearing blast furnace slag are analyzed. The technical requirements and development trends of extraction of titanium from titanium-bearing blast furnace slag by hydrometallurgy are prospected.

Using lactic acid solution as the leaching agent, selective leaching of zinc from metallurgical dust collected from a steel plant in Shanxi was investigated. The effects of leaching time, leaching temperature, liquid volume to solid mass ratio and lactic acid concentration on the leaching effect were investigated, and the leaching mechanism was explored. The results show that under the optimal leaching conditions of lactic acid concentration of 3%, leaching temperature of 20 ℃, leaching time of 5 min, and liquid volume to solid mass ratio of 10 mL/1 g, the leaching rates of zinc and iron are 91.56% and 4.69%, respectively, achieving selective leaching of zinc. In the leaching solution, zinc primarily exist in the forms of Zn［CH₃CH(OH)COO］⁺ and Zn²⁺, while in the leach residue, zinc is mainly present as zinc ferrite. The weak acidic environment of the leaching system can effectively suppress the dissolution of iron.

Recovery of active materials from the cathode materials of waste NCM ternary lithium batteries using NaOH-directed dissolution method of oxide films was investigated. The effects of solid mass to liquid volume ratio, temperature, and NaOH concentration on the recovery rate of active materials were examined. The results indicate that under the conditions of solid mass to liquid volume ratio, of 4 g/10 mL, temperature of 65 ℃, and NaOH concentration of 3 mol/L, the complete separation of the active materials from the aluminum foil can be achieved in just 1 minute. The shape of the recovered aluminum foil is intact, and the recovery rate of the active materials can reach 98.6%. The method can achieve complete and efficient separation of aluminum foil and active materials from the cathode material with PAA-NH₄ as the binder, and has certain promotion and application value.

The leaching of zinc and germanium from germanium-rich zinc concentrate by oxygen pressure leaching process was studied. The effects of key factors such as the initial acidity of sulfuric acid, reaction temperature, leaching time, oxygen partial pressure, sodium lignosulfonate addition amount, liquid volume to solid mass ratio, and stirring speed on the leaching rates of zinc and germanium were systematically investigated. The optimal process conditions for oxygen pressure leaching are determined through single-factor experiments as follows:leaching temperature is 160 ℃, leaching time is 150 min, initial acidity of sulfuric acid is 160 g/L, partial pressure of oxygen is 1.2 MPa, addition amount of sodium lignosulfonate is 1 g, liquid volume to solid mass ratio is 8/1, and stirring speed is 600 r/min. Under the conditions, the germanium leaching rate reaches 94.86% and the zinc leaching rate reaches 99.98%. Compared with the traditional atmospheric pressure leaching, the optimized oxygen pressure process can increase the germanium leaching rate by more than 15%, shorten the leaching time by 40%, and also avoid the emission of high-concentration H₂S gas, reducing environmental pollution and providing a technical reference for the comprehensive utilization of valuable elements in zinc concentrate.

Due to its late discovery, wide distribution, large reserves, complex composition, and low grade, the comprehensive development and utilization of clay type lithium mines still lack systematic research. A systematic study was conducted on the optimization of enhanced leaching process parameters for clay type lithium ore in Liuzhi Special District, Liupanshui City, Guizhou Province. The effects of roasting process conditions such as roasting temperature and time, as well as the effects of leaching process conditions such as leaching agent hydrochloric acid concentration, leaching temperature and time, stirring speed, and liquid volume to solid mass ratio on the experimental results were investigated. The results show that roasting can destroy the crystal lattice of minerals such as kaolinite, superphosphate, diopside, and lithium chlorite in clay type lithium ores, which is beneficial for the sufficient contact between lithium containing phases and leaching agents during subsequent leaching processes, thereby improving their leaching efficiency;After high-temperature roasting at 600 ℃ for 90 min, the clay type lithium ore was subjected to optimal leaching conditions of 60 min, leaching temperature of 80 ℃, hydrochloric acid concentration of 4 mol/L, stirring speed of 400 r/min, and liquid volume to solid mass ratio of 6∶1. The lithium leaching rate can reach 93.48% and the leaching effect is good. The method does not require any additives during the calcination process, which can reduce pollution and lower costs. It has certain promotion and application value.

Zircon sand often contains minerals such as kyanite, thorite and thorianite, which contain trace amounts of radioactive elements such as uranium and thorium. During the production of zirconium oxychloride, these radioactive elements are concentrated in the waste residue, which has certain recycling value. To meet the demands of comprehensive utilization and radioactive pollution control of such waste residues, the process conditions for extracting valuable elements such as uranium and thorium from the waste residues were studied, and the effects of different leaching factors and parameters on the leaching efficiency of uranium and thorium were investigated. The results show that under the conditions of sulfuric acid concentration of 4 mol/L, leaching time of 4 h, liquid volume to solid mass ratio of 4∶1, and leaching temperature of 90 ℃, the leaching rates of uranium and thorium reach 99.9% and 88.6%, respectively. The result is better.