The influence of magnetite on bioleaching of chalcopyrite by Acidithiobacillus ferrooxidans was systematically explored by electrochemical tests such as open-circuit potential and cyclic voltammetry. Results show that the leaching rate of chalcopyrite can be increased by increasing the addtion of magnetite in the leaching system by undomesticated bacteria. The bacteria after domestication presents enhanced activity. With the addition of magnetite at an amount of 0.5 g, the copper leaching rate can be increased by around 8%. With the addtion of magnetite at an amout over 0.5 g, jarosite is generated during the leaching process, which can worsen the leaching environment, leading to the copper leaching rate just up by about 2%. The open circuit potential of chalcopyrite is always higher than that of magnetite in the system with different concentrations of Fe³⁺. During the galvanic reaction between chalcopyrite and magnetite, chalcopyrite acts as the cathode, which is not conducive to oxidation and dissolution of chalcopyrite. However, Fe³⁺in the solution can increase the corrosion rate of chalcopyrite, leading to an increased leaching rate of chalcopyrite.

To investigate the current situation of heavy metal pollution in a stone coal mine in Hunan Province, the content of Cd, Hg, As, Pb, Cr, Cr (Ⅵ), Zn, Fe, and Mn in water and soil samples was determined by using ICP, and the risk of heavy metal pollution was evaluated by using the Nemerow pollution index and potential ecological hazard index respectively. The results show that concentrations of Cd, Cr (Ⅵ), Zn, Fe and Mn in water are 1.935 5, 0.025 3, 6.024 9, 16.222 0 and 4.214 9 mg/L on average, with pollution indices of 387.10, 5.06, 3.01, 54.07 and 42.15, presenting the pollution degree in the following descending order: Cd>Fe>Mn>Cr (Ⅵ)>Zn; while content of Pb、Zn、Cr、As、Hg and Cd in the soil is 8.51, 38.59, 18.65, 10.01, 0.18 and 3.41 mg/kg on average, with ecological risk coefficient of 2.13, 0.98, 0.85, 18.00, 28.55 and 339.80 on average, presenting pollution degree in the following descending order: Cd>Hg>As>Pb>Zn>Cr. It is shown that the comprehensive potential ecological risk indices of the whole mine is 390.31, indicating a higher ecological pollution risk. The mine area is polluted by several kinds of heavy metals, especially in the downstream areas of waste dump and sedimentation tank.

Mo-Bi bulk concentrate is usually processed with a longer flowsheet at higher cost, and the traditional bismuth smelting processing technique also features longer flow, high energy consumption, as well as lower bismuth recovery. In order to solve those problems, an oxygen-rich hydrochloric acid leaching process was adopted in an experimental study on beneficiation of Mo-Bi bulk concentrate, and the effects of HCl concentration, leaching time and temperature on the leaching rates of Mo and Bi were investigated. It is shown that oxygen-rich hydrochloric acid leaching at 80 ℃ for 6.0 h, with HCl concentration of 3 mol/L, liquid/solid ratio of 3 ∶ 1, and stirring speed of 500 r/min, can result in the Bi leaching rate up to 99.13% and Mo left in the leaching residue. Thus, molybdenum and bismuth can be efficiently separated. The obtained leaching solution is then subjected to purification for purity removal and replacement with iron plate, and the finally obtained sponge bismuth can have purity exceeding 99%.

In order to comprehensively utilize iron-containing dust and consume alkaline residue from petrochemical industry, a sintering pot test was conducted by adding iron-containing dust and the alkaline residue from petrochemical industry into raw materials for sintering. The results show that an addition of iron-containing dust and the alkaline residue from petrochemical industry can not only improve vertical sintering speed, utilization coefficient, yield rate and tumbler index, but also lead to increased content of alkali metals and Zn, as well as falling in the TFe content in the sintered ores. Thus, the sintered ore presents poor reduction performance, and poor low-temperature reduction pulverization indices. It is found that the raw material with the addition of iron-containing dust at an amount of 0.5% and the addition of alkaline residue from petrochemical industry at an amount of 0.05% can meet the requirement for feed to furnace, and also make it possible for the comprehensive utilization of iron-containing dust and consumption of alkaline residue from petrochemical industry.

In order to effectively separate acid, arsenic and copper/zinc from smelting waste acid, a kind of simulated waste acid was taken to be treated by using electrodialysis with bipolar membrane. The effects of running time, acidity, initial concentration of arsenic and copper/zinc on the separation rate of acid, copper/zinc, and arsenic were investigated, and the process was also applied in the treatment of waste acid from copper smelting for verification. Besides, the surfaces of anion exchange membrane, cation exchange membrane and bipolar membrane in electrodialysis after long-term usage were analyzed and characterized. The results show that with the running time more than 80 min, arsenic concentration less than 9 g/L, acidity less than 5% and copper/zinc concentration less than 5 g/L, three kinds of solution respectively containing arsenic, valence metallic salt and acid were obtained. It is shown that the arsenic separation rate is more than 93%, the recovery rate of copper/zinc is more than 96%, and the recovery rate of acid is more than 97%. More than 90% of other metallic ions (such as Na, K, Mg, Ca) in waste acid are trapped in the bipolar membrane salt chamber, thus making inorganic salt ions effectively recovered from waste acid by an open circuit. After nearly two years of application, electrodialysis membrane and bipolar membrane are observed to have no obvious change in the apparent morphology, and no obvious precipitant attached on them.

The furnace slag generated from smelting of South African vanadium-titanium magnetite was taken in an experimental study by adopting direct reduction followed by melting, and then analyzed by XRD to investigate the effect of basicity on the metallurgical properties of the slag, as well as on the separation of iron from slag. Furthermore, the effect of basicity on the melting characteristics and viscosity of the slag were also explored. Results show that melting at 1 450 ℃ with the addition of carbon at an amount of 5%, the slag has its corresponding softening temperature, hemisphere temperature and flow temperature rising gradually with the increase in basicity. With the basicity ranging from 0.9 to 1.2, the melting temperature of slag increases rapidly, and the measured and calculated viscosity of slag presents a trend of an initial decrease followed by increase. When the basicity rising from 0.9 to 1.4, the diffraction peaks of pyroxene and feldspar in the slag climb to the high value and then start to fall, and the relative contents of perovskite and calcium-aluminum spinel gradually increase after an initial decrease. It is shown that the slag with basicity of 1.2 and viscosity of 0.130 Pa·s can present better performance.

Based on the technique for separation and recovery of metal ions in the leaching solution of spent lithium-ion batteries, nickel and cobalt ions were efficiently separated from manganese ions in leaching solution by selective precipitation of sulfide. The effects of pH value, addition coefficient of sodium sulfide, temperature and time for precipitation on the precipitation rates of nickel, cobalt and manganese ions were systematically investigated. The results show that the precipitation rates of nickel, cobalt, manganese and aluminum ions are 99.73%, 100%, 2.77% and 1.24%, respectively, after 6 min-precipitation at 25 ℃ with the addition of sodium sulfide at a coefficient of 1.5 and pH of 5.0. An orthogonal experiment shows that factors of addition coefficient of sodium sulfide, pH value, precipitation temperature and precipitation time have influence on the precipitation rates of nickel ions in a descending order, while the various factors of addition coefficient of sodium sulfide, precipitation temperature, pH value and precipitation time also have influence on the precipitation rates of cobalt ions in a descending order. It is found that the precipitation rates of manganese and aluminum can reach 99.77% and 6.86%, respectively, after a 12 min-precipitation at 70 ℃ with addition of sodium sulfide at a coefficient of 2.5 and pH of 6.0.

In view of interference of the existence of selenium in determination of gold and silver in crude selenium sample, the sample with an addition of concentrated sulfuric acid was firstly heated to remove selenium. Then, sodium chloride solution was added to precipitate silver therein, and the obtained residue after filtration was taken for gold and silver determination using fire assay by gravimetry. Thus, a process of heating with sulfuric acid to remove selenium followed by fire assay gravimetry was established for continuous determination of gold and silver in crude selenium, and the effects of residual selenium, sulfuric acid dosage and heating time on the determination results were also discussed. Furthermore, such continuous determination process was also compared to the industrial standard method in terms of the analysis of gold and silver in crude selenium. By using the proposed continuous method, the relative standard deviations (RSD₇) of gold was within a range of 0.54%-1.30%, and the RSD₇ of silver was within a range of 0.28%-0.39%. The spike recovery of gold was 94.6%-101.3%, and the spike recovery of silver was 96.3%-100.1%. It is shown that the analysis results are consistent with those by industrial standard method. It is concluded that the proposed determination method, being fast and accurate, is suitable for determination of gold and silver in crude selenium.

Experiments on tempering at different cooling rates were conducted for annealed 30CrMnSiA steel to investigate the effect of cooling rate during tempering on the properties of tempered 30CrMnSiA steel and its microstructure evolution. The results show that the cooling rate during tempering has brought slight effect to the hardness, and a certain influence to impact properties of 30CrMnSiA steel. After tempering at 510 ℃, the 30CrMnSiA steel has its surface mainly subjected to compressive stress and the center subjected to tensile stress. A faster cooling rate during tempering will result in a higher residual stress on the surface of the sample. During the tempering process, C element mainly combines with Fe element to form Fe-C compounds, while a trace of C element, together with Cr and Si elements, forms Cr-C compounds and Si-C compounds. It is found that the rapid cooling rate has slight effect on the content and size of carbides.

The effects of different heat treatment regimes on the microstructure and properties of as-cast Mg-5Sn-1.5Al-1Zn-1Si alloy were investigated. The results indicate that during the dissolution of solid, as the dissolution time is prolongsed, the alloy dendrites gradually dissolve and the grains gradually spheroidize. It is shown that the appropriate dissolution parameter is 510 ℃ × 8 h, and the alloy after such treatment has an evenly distributed microstructure, with a trace of precipitation of fine second-phase particles from the matrix, and thus possesses a high elongation rate. The appropriate aging parameter for the alloy is 200 ℃ × 16 h, and due to precipitation and migration of the phases segregating at the grain boundary, the alloy after aging treatment possesses clear grain boundaries and a microstructure with high uniformity, and also has the yield strength up to 136.3 MPa, which is higher than that of the as-cast alloy by 16.5%. After a treatment including 8 hours of solid dissolution at 510 ℃ and 16 hours of aging at 200 ℃, the alloy has its uniformity and dispersion of the microstructure further improved, and its tensile strength and hardness reach to 178.2 MPa and 59.6HB, respectively, up by 21.6% and 23.4% compared to the as-cast alloy.