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 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.

The granulated copper slag prepared by dry centrifugal granulation process was taken as oxygen carrier, a thermodynamic analysis and an experimental study were conducted for oxygen absorption and release reactions of copper slag. The effects of oxidation temperature, reduction temperature, particle size of copper slag and CaO addition on the phase composition of copper slag were investigated. The results show that the reactions of oxygen absorption and release of iron oxide in copper slag run step by step, and the granulated copper slag particles have certain capacity of oxygen absorption and release. Oxidation and reduction at higher temperature is beneficial to reactions of oxygen absorption and release of iron oxide in copper slag. Copper slag with smaller particle size is beneficial to the oxygen absorption reaction of FeO and Fe₃O₄, and addition of CaO is beneficial to the oxygen release reaction of copper slag.

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 acid leaching solution of electrostatic precipitator dust from copper smelting has a high concentration of sulfuric acid, in which the iron and arsenic exist in the form of Fe³⁺and As⁵⁺, thus it is decided to adopt arsenic sulfide residue as the precipitant for copper precipitation. Firstly, an experiment was performed on the addition of arsenic sulfide residue in single Cu²⁺ and Fe³⁺ solution with different acid concentrations. Based on that, an experiment was performed for copper precipitation and arsenic leaching in the actual acid leaching solution. The results show that in the process of copper precipitation with arsenic sulfide residue, oxidation and reduction reactions between Fe³⁺ and S^2- occur firstly, which is followed by oxidation and reduction reactions of As⁵⁺ and S^2-, and finally a sulfurization reaction for precipitation of Cu²⁺. When the addition of arsenic sulfide residue is at an amount of 1.4 times the theoretical amount, it is shown that the copper precipitation rate is relatively higher, but the rate of arsenic dissolution is lower.

An interactive orthogonal experiment was carried out. With the metallization rate of the products of fluidized reduction of iron ore powder as dependent variables, reduction temperature, reduction time, gas linear velocity and pressure of reduction as independent variables, the effects of various operating parameters and their interactions on the fluidized reduction of iron ore powder were investigated by means of range analysis and variance analysis. Results show that effects of four factors and their interaction on the metallization rate of fluidized reduction of iron ore powder are in the following descending order: reduction temperature > gas linear velocity > reduction time > pressure of reduction > interaction between reduction temperature and gas linear velocity > interaction between reduction temperature and pressure of reduction > interaction between reduction time and gas linear velocity > interaction between pressure of reduction and gas linear velocity > interaction between reduction temperature and reduction time > interaction between pressure of reduction and reduction time. It is shown that higher reduction temperature is helpful to the combination of iron whiskers, forming a compact structure. A higher gas linear velocity can improve the kinetic conditions of fluidized reduction, which is beneficial to fluidized reduction of iron ore powder.

Based on a summarization of decomposition techniques of scheelite by hydrometallurgical process, the advantages and disadvantages of several decomposition techniques, such as decomposition with hydrochloric acid, soda sintering, pressure boiling of soda, decomposition with sodium hydroxide, decomposition with fluorine salt, decomposition with mixture of sulfuric acid and phosphoric acid, as well as lime sintering conversion followed by decomposition with ammonium bicarbonate were all analyzed. It is concluded that those three techniques, including decomposition with fluorine salt, pressure boiling of soda and decomposition with mixture of sulfuric acid and phosphoric acid, will gradually become the mainstream decomposition techniques for scheelite.

Electrolytic manganese anode slime (EMAS) was processed by adopting sulfur-based reduction roasting and sulfuric acid leaching to separate manganese and lead therein. The effects of roasting temperature, molar ratio of sulfur to manganese, roasting time, particle size of EMAS, stirring speed in leaching, leaching temperature, leaching time, solid-liquid ratio and sulfuric acid concentration on separation of manganese and lead were studied. The results show that with the optimized roasting conditions, including roasting temperature of 550 ℃, molar ratio of sulfur to manganese at 1∶1, roasting time of 50 min, EMAS at particle size of -0.177 mm, and optimized acid leaching conditions including stirring speed of 350 r/min, leaching temperature of 40 ℃, leaching time of 20 min, solid-liquid ratio at 1∶20, and sulfuric acid concentration of 2.5 mol/L, the leaching rate of manganese from EMAS can reach 97.4%, and the concentration of manganese ions in filtrate is 38.84 g/L, while the content of Pb in leaching residue is 45.26%. As a result, the effective separation between manganese and lead can be actualized.

A thermodynamic analysis reveals the phase evolution of main metals in the production of low-grade nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the main influencing factors in the process of sulfidation smelting were analyzed. The thermodynamic calculation shows that with the electroplating sludge grading 6% Cu and 4% Ni, respectively, sulfur gypsum as the sulfurizing agent, the actual addition of sulfur 2.0 times of the theoretical amount, and the smelting atmosphere P(CO)/[P(CO)+P(CO₂)]=50%, the low-grade nickel matter with the expected grade of 57.2% (Cu+Ni) can be produced, with the grade of copper and nickel in the slag lower than 0.2%. It is shown that the direct recovery rate of copper and nickel can reach 99.89% and 96.59% respectively, and the sulfur fixation rate is 77.20%. An industrial application shows that compared with conventional wet metallurgical recovery process, this technique can bring higher metal recovery rate with a green and low carbon process, thus presenting obvious technical advantages.

In order to obtain the optimal concentration of bone glue as a commonly used additive for lead electrolysis and also understand the influence of its colloidal impurities on lead electrolysis, the effects of the concentration of bone glue in the electrolyte, the standing time of bone glue solution and the liquid-solid ratio for purification with activated carbon on lead electrolysis were investigated by evaluating the turbidity of the solution, current efficiency, power consumption and the morphology of precipitated lead. It is found that the optimal concentration of bone glue in lead electrolyte is 0.8 g/L, and colloidal impurities can be removed by resting the bone glue solution for 72 hours or by purifying it with activated carbon in a ratio of 1 000∶1. After purification, lead electrolyte has its current efficiency up to 99.19%. The power consumption of electrolysis declines to 51.79 kW·h/t, and the obtained precipitated lead has a flat and smooth surface.