The pollution of heavy metals in the soil of a zinc smelting site was analyzed, and the influence mechanism of goethite on cadmium migration in the soil was discussed by performing simulation experiments. The results show that the geometric mean values of As, Cd, Cu, Hg and Pb in zinc smelting site soil are 15.9 mg/kg, 1.52 mg/kg, 62.1 mg/kg, 0.108 mg/kg and 167 mg/kg respectively. The average content of Cd is 11.7 times the general value of soil in Hunan Province. It is shown that Cd in the soil has strong migration, and can be infiltrated down to the depth of 6 m or more of the soil. The results of stochastic forest model analysis show that Cd migration in the soil is mainly affected by goethite and silt. Cd in the soil can be adsorbed by goethite and then migrated. The pH value and ionic strength of leachate obviously affect the migration of Cd by goethite in the soil. When the pH of leachate is 6 and the ionic strength is 1 mmol/L, 37.6% of Cd in the soil can be migrated by goethite. Adjusting the pH value and salt ions concentration of soil can change the migration of Cd by goethite in the soil. As a result, the risk of pollution by heavy metals such as Cd in the soil of zinc smelting site can be controlled.

Aiming at the problems of insufficient dissociation degree of mineral monomer and unsatisfactory indices in the leaching process of roasted gold ore in a smelter of Lingbao Gold Group Co Ltd, an ALC mill, for the first time, was applied to fine grinding of roasted gold ore. The results show that with ALC mill used in an open-circuit fine grinding, the filter cake pulped and then milled to a fineness of -38 μm 96% before cyanide leaching, the final cyanide tailings can have its gold grade reduced from 1.72 g/t to 1.42 g/t. As a result, the comprehensive economic benefit can be increased by 8.156 8 million yuan per year.

The effects of low temperature tempering on the microstructure and mechanical properties of Q1100 ultra-high strength steel after pretreatment of normalizing and quenching were studied. The results show that tempered martensite were obtained after normalizing (890 ℃ × 40 min) + quenching (890 ℃ × 30 min) + tempering (185-320 ℃ × 90 min) processes. After tempering at different temperatures, all tested steels have their tensile strength higher than 1 360 MPa, yield strength higher than 1 200 MPa, hardness higher than 400HV3, elongation higher than 13%, and impact energy at -40 ℃ higher than 35.2 J. With the rising of tempering temperature, the tensile strength and hardness gradually decrease, the yield strength first increases and then decreases, the elongation after fracturing increases after an initial slight decrease, and the impact energy at -40 ℃ decreases followed by increase. At a tempering temperature of 230 ℃, the steel in the test has tensile strength of 1 445 MPa, yield strength of 1 238 MPa, hardness of 429HV3, plasticity of 13.8%, and toughness of 47.5 J, which all largely exceed the service standard of Q1100 ultra-high strength steel for construction machinery.

A thick layer of accumulated debris after landslide is distributed on the slope in the middle of site. And the debris will lose stability due to excavation of slope, resulting in an unstable slope. The physical and mechanical parameters of those accumulated debris after landslide were determined by performing indoor tests and inverse analysis. According to the site environmental conditions and the distribution characteristics of rock and soil layers, the overall and local stability and deformation characteristics of slope under different working conditions were analyzed by simulation with software. Also, the stability and development trend of slope in the middle of site were comprehensively evaluated. Based on the stability analysis and evaluation results, a corresponding prevention and control suggestion is put forward.

A foreign copper sulfide concentrate from slag processing was treated by adopting heated sulfuric acid leaching with trivalent iron compound as an oxidant for recovering copper therein. The effects of oxidant dosage, leaching temperature, leaching time, initial concentration of sulfuric acid and liquid-solid ratio on the leaching rate of copper from copper sulfide concentrate were investigated. The results show that with the proper condition, including the oxidant of hematite at an amount of 0.2 g/g ore, leaching temperature of 85 ℃, leaching time of 6 h, liquid-solid ratio at 5∶1, and sulfuric acid with initial concentration of 200 g/L, the copper leaching rate can reach 97.96%. A verification test with different oxidants shows that hematite and magnetite present good oxidability in acid leaching system, leading to the copper in those copper sulfide concentrate leached out at a medium temperature. Also, the higher the purity of trivalent iron compounds, the better the oxidative leaching effect of copper.

In view of the resource characteristics and production status of Ekou Iron Mine of Taiyuan Iron & Steel (Group) Co Ltd, an experimental research was conducted to upgrade iron grade of the concentrate from the second-stage magnetic separation while reducing impurities therein. An optimized flowsheet consisting sequentially of grinding, low-intensity magnetic separation and reverse flotation was adopted in the experiment, resulting in a high-quality iron concentrate grading 69.93% TFe at a recovery of 93.08%, with a yield of 76.33%, while the SiO₂ content was reduced to 1.63%.

A silicothermic process was adopted to extract phosphorus, and the main chemical reactions and Gibbs free energy were clarified by thermodynamic calculation. The feasibility of the process was then verified by performing practical experiments. The main reaction of silicothermic process for phosphorus extraction is as follows: 2 (3CaO·P₂O₅)+5Si+SiO₂ ==== 2P₂(g)+6CaO·SiO₂. The vacuum degree can promote the reaction to proceed in the forward direction, and a reaction system with lower pressure can lead to smaller standard Gibbs free energy of the reaction, leading to silicothermic reduction reaction occuring much easier. Increasing temperature can promote the reaction to proceed in the forward direction, and prolonging reduction time properly at the same temperature can improve the reduction rate of the reaction. After a reaction at 1 250 ℃ for 2.5 h under normal pressure, rough phosphorus (yellow phosphorus) with purity of 95.03% can be obtained by adopting silicothermic process, and the content of residual phosphorus in the dry slag is 1.45%. It is shown that using siliceous reductant in the silicothermic process for preparing yellow phosphorus can avoid the usage of coke, which conforms to low-carbon development strategy.

The microstructure and mechanical properties of A356 aluminum alloy joints were studied after they were processed with technique of T6 heat treatment followed by friction stir welding (T6-FSW) and technique of friction stir welding followed by T6 heat treatment (FSW-T6) respectively. It is found that the nugget zone of T6-FSW joint is composed of dynamically recrystallized fine-grains, but the precipitates are dissolved or coarsened. The transverse tensile strength and elongation of T6-FSW joint are 214 MPa and 5.3% respectively, and an average hardness is 76HV_0.5. The tensile strength and elongation of the nugget zone are 236 MPa and 12.5% respectively, and the impact toughness of the joint is 12.10 J. Abnormal grain growth occurs in the nugget zone of FSW-T6 joint, where fine precipitates with high density are formed. The transverse tensile strength and elongation of FSW-T6 joint are 254 MPa and 8.5% respectively, and an average hardness is 96HV_0.5. The tensile strength and elongation of the nugget zone are 297 MPa and 7.0% respectively, and the impact toughness of the joint is 8.23 J.

As for a kind of low-calcium and low-magnesium stone coal featuring low alkalinity and high content of silica, a process of sulfuric acid curing followed by water leaching was adopted in an experiment, and the effects of grain size, sulfuric acid dosing, curing temperature and curing time on vanadium leaching were investigated. The results show that the leaching rate of vanadium reaches 88.6% when the raw ore with grain size of -0.15 mm was cured at 120 ℃ for 8.5 h by adding sulfuric acid at 20%, and then water leaching at the room temperature for 2 h with liquid and solid at a ratio of 2∶1. During the curing process, the mica structure with the locked vanadium therein is effectively dissociated and soluble vanadium is released. It is shown that the leaching solution has a lower content of silicon (0.08 g/L), significantly reduced compared to the process of direct acid leaching or the process of roasting plus acid leaching, which is beneficial to the subsequent extraction process.

Tests were conducted to compare the performance of detergent FD-602 and nitric acid in cleaning the copper concentrate ceramic filter plate in Tonglushan Mine in Hubei Province. The results show that after being cleaned with FD-602, the ceramic filter plate has cleaner surface and its filter cake also presents uniform adsorption during filtration. After being cleaned using FD-602 and nitric acid, the ceramic filter can produce 6.63 t/h and 5.85 t/h filter cakes on average, with average moisture of 11.21% and 11.58%, respectively. Every ton of filter cake consumes 0.16 kg and 1.78 kg detergent, with the cost of 6.4 yuan and 5.696 yuan, respectively. When the cleaning water collected from the FD-602 cleaning process mixed with domestic water at a ratio of 1∶5 is returned to flotation process, it is shown that there is no obvious influence brought to the flotation performance.