In order to find a reasonable disposal method for electrolytic manganese slag (EMS), effect of roasting at medium and high temperature on the content of manganese, sulfur and ammoniacal nitrogen in EMS was explored. The results show that after the EMS is directly roasted at 1 050 ℃ for 60 min, the mass fraction of S in the EMS sample falls from 9.11% to 0.87%, while the mass fraction of Mn goes up from 1.87% to 2.26%. After being washed with water, the EMS sample is then roasted with 3% coal (in mass fraction) at 1 000 ℃ for 60 min. As a result, the mass fractions of S and Mn in the obtained roasted sample drop down to 1.32% and 0.78%, respectively. It is found that after direct roasting process at medium and high temperature, EMS can meet the requirement of mass fraction of S for cement admixture, and also medium and high temperature roasting process can almost remove all ammoniacal nitrogen therein, presenting a good removal effect.

A heap leaching test was carried out for the low-grade copper-cobalt oxide ores from Congo (DRC), and effects of spray intensity, spray acidity and ore particle size on the leaching rates of copper and cobalt were investigated. The results show that both acidity and intensity of spray bring significant impact to the speed and cumulative rates of copper and cobalt leaching, while the ore particle size has little effect on leaching process. And finally, the optimal conditions for heap leaching of low-grade copper-cobalt ore were determined, including spray acidity at 20 g/L, spray intensity of 15 L/(m²·h), and ore particle size of less than 40 mm. It is shown that the cumulative leaching rates of copper and cobalt can reach 90.89% and 82.27%, respectively, after 100 days of heap leaching.

The process and mechanism of removing iron ions from manganese leaching solution by a combination of pyrite and air were explored. The results show that after iron removal by 1 hour of reaction at 25 ℃, with pH of solution at 2.5, addition of pyrite at an amount of 15 g/L, and air flow rate at 2.4 L/min, the left leaching solution has a mass concentration of residual iron ions less than 0.01 g/L, and the manganese recovery rate is higher than 99%. Pyrite as a reducing agent, in combination with air in the solution, creates an active reaction zone around pyrite with the coexistence of Fe³⁺/Fe²⁺ with oxygen, which contributes to the precipitation of iron ions in the form of goethite in the solution for removal.

Nickel, Cobalt and Manganese in the cathode materials of spent ternary lithium-ion batteries were recovered by leaching with a combination of citric acid and hydrogen peroxide. The possible reactions during the leaching process were analyzed, and the effects of factors, including citric acid concentration, mass fraction of hydrogen peroxide, leaching temperature, leaching time and liquid-to-solid ratio on the leaching rates of nickel, cobalt and manganese from cathode materials were also investigated. It is found that after 60 min leaching at 80 ℃ with citric acid at a concentration of 1.5 mol/L, hydrogen peroxide at a mass fraction of 8%, and a liquid-to-solid ratio of 25 mL/g, the leaching rates of nickel, cobalt and manganese are 97.58%, 97.35% and 96.12%, respectively. Then, an antisolvent crystallization method is adopted with ethanol as antisolvent agent to recover metals from the obtained leach liquor, leading to the crystallization rates of nickel, cobalt and manganese at 92.34%, 93.07% and 99.69%, respectively.

An experiment was carried out with a pelletizing and magnetization roasting process for fine-grained specularite to investigate the pelletizing process, as well as the roasting performance and effect of pellets in the process of magnetization roasting. The results show that by adopting a process of fine grinding and pelletizing followed by magnetization roasting with an additionally prepared reducing agent, under the condition of roasting at 810 ℃ for 60 min, and addition of charcoal at an amount of 2.5%, a concentrate grading 49.04% Fe at 76.99% recovery can be obtained. In comparison, with a process of direct pelletizing followed by 60 min magnetization roasting at 650 ℃ with additionally prepared reducing agent and addition of semi-coke at an amount of 3.0%, the concentrate grading 52.95% Fe at 85.07% recovery can be obtained. It is found that the processing technique consisting of direct pelletizing and magnetization roasting is simpler and can bring better processing indicators. It can provide a reference for on-site processing of fine-grained specularite by adopting magnetizing roasting.

A cyanide-free leaching test was performed for the arsenic-carbon bearing gold ore from Laos, and effects of grinding fineness, pH value of pulp, concentration of slurry, and the dosage of golden cicadas environment-friendly leaching agent for gold on gold leaching effect were investigated. The results show that pre-treatment with hydrogen peroxide can improve the leaching rate of gold. With a grinding fineness of -0.074 mm 95% and an agitating speed of 2 000 r/min, the pulp is pre-oxidized with 500 g/t of hydrogen peroxide for 3 h, and then treated by 30 h agitation leaching with addition of lime at an amount of 3 000 g/t and golden cicadas environment-friendly leaching agent for gold at 5 000 g/t, leading to the residue grading 0.25 g/t Au and gold leaching rate of 92.27%. It is shown that this pretreatment with hydrogen peroxide can make gold leaching rate up by 1.96 percentage points.

An experiment study was carried out on a processing technique of reduction leaching of pyrolusite with acidic wastewater from steel mills as the reductant, for comprehensive utilization of pyrolusite and acidic wastewater of steel mills. The results show that 3 hours of leaching at 90 ℃, with FeCl₂ and MnO₂ in a mass ratio of 2.2, liquid-solid ratio of 11∶1 and the acid wastewater at an initial concentration of 2.5 mol/L, can result in the leaching rates of Mn, Fe and Al from the pyrolusite at 97.14%, 95.37% and 41.33%, respectively. And then, Fe³⁺ in the leachate is reduced with scrap iron at an amount of 1.1 times the theoretical amount at a temperature of 80 ℃ for 50 min, leading to the reduction rate of Fe³⁺ up to 99.85%. After Fe³⁺ is reduced to Fe²⁺, the Fe²⁺-containing reducing solution is returned for leaching again, presenting stable leaching results. It is shown that the average leaching rates of Mn, Fe and Al from pyrolusite are 96.75%, 95.31% and 41.18%, respectively.

Vanadium was extracted from vanadium-containing stone coal by adopting a process of sulphuric acid curing and water leaching, and the effects of sulphuric acid curing and water leaching conditions on vanadium leaching rate were investigated. It is found that the vanadium-containing stone coal is firstly subjected to a sulphuric acid curing process at 130 ℃ for 8 h, with an addition of H₂SO₄ at an amount of 25%；and then the obtained product is leached by water at 90 ℃ for 120 min, with liquid-solid ratio of 2∶1, resulting in the vanadium leaching rate of 90.79%. After the vanadium-containing leachate is oxidized with NaClO₃, the vanadium in the oxidized solution is adsorbed with D202, and then the vanadium in the resin is desorbed. The obtained solution after desorption is subjected to calcination, and vanadium pentoxide is produced with a purity up to 99.21%. It is shown that a total recovery rate of vanadium is 85.99%.

Thermodynamic analysis was conducted with HSC Chemistry 9.0 software for removing arsenic by sulfuration from waste acidic solution left after copper electrolysis, and it is found that H₂S could effectively make asenous acid and arsenate in the high-concentrated sulfuric acid system precipitated by sulfuration. Based on the theoretical analysis results, an experiment on arsenic removal of waste acidic solution by sulfuration was carried out to investigate the effects of sulfurizing agent dosage and reaction time on the arsenic precipitation effect by sufuration. Results show that by 30 min-sulfuration with an addition of H₂S at 0.87 times the theoretical amount, the arsenic content in waste acidic solution after precipitation process falls down to 10.68 mg/L from 6 777.52 mg/L, and the removal rates of arsenic, copper and antimony are 99.84%, 99.76% and 99.33%, respectively. The iron and nickel therein are hardly precipitated, and the mass fraction of arsenic and sulfur in the residue of the arsenic removal process are 43.21% and 44.68%, among which the arsenic in the form of arsenic sulfide is in a mass fraction of 42.33%, and S/As in the arsenic sulfide is in a ratio of 2.29. The finally obtained product is a mixture of As₂S₃ and As₂S₅. It is shown that the thermodynamic analysis results differ slightly from the experimental results, but are still of guiding reference for experiments and practice.

The effect of Sc on the microstructure and properties of Al-8.5Zn-2.3Mg-2.4Cu alloy was investigated. It is found that an addition of Sc can make the as-cast Al-Zn-Mg-Cu alloy with obviously smaller grain. As the Sc content (mass fraction) increases from 0 to 0.4%, the grain size of alloy decreases from 107.7 μm to 49.96 μm and the hardness increases from 116.8HV to 130.2HV. After hot-rolling process with large deformation quantity followed by 1 hour of solution heat treatment at 470 ℃, the Sc-containing alloy has higher dislocation density compared to the alloy without Sc addition, and the alloy with an addition of 0.4% Sc has a recrystallization rate dropped from 92.4% to 45.7% due to inhibition of its recrystallization behavior. After 24 hours of aging treatment at 120 ℃, the Al-Zn-Mg-Cu alloy with an addition of 0.4% Sc can be observed to have a large amount of spherical Al₃Sc particles and short rod-like η′ (MgZn₂) particles in dispersive distribution. Based on the plotted a crystal structure of Al₃Sc-MgZn₂ with coherent or semi-coherent interface with α (Al), it can be deduced that the Al₃Sc particles provide heterogeneous nucleation sites for η′ (MgZn₂) phase to promote its nucleation, which can promote precipitation hardening of the alloy.