Digestion behaviors of several single silicon-containing minerals including kaolinite, illite and pyrophyllite in aluminate solution were investigated. The result shows that the digestion rates of kaolinite, illite and pyrophyllite in aluminate solution were influenced by reaction conditions such as temperature. Adopting quantum chemistry theoretical calculation, using CASTEM procedure module, the slab model of kaolinite, illite, pyrophyllite and their ordinary complete cleavage plane (001) were geometry optimized at GGA-PW91 level. The micro-essence of the different reaction activities among kaolinite, illite, pyrophyllite in aluminate solution was opened out. It is found that the reaction activities of kaolinite, illite, pyrophyllite are obviously different and the reaction activity of pyrophyllite is the highest. The Si—O bond strength of illite is the strongest and its Al—O bond strength is comparatively the weakest, so Si in it is the most difficult to be removed. The Si—O bond strength of pyrophyllite is the weakest, so Si in it is relatively easy to be removed. The micro-electron structure of complete cleavage plane and the Si—O bond strength of kaolinite, illite and pyrophyllite are evidently influenced by the existence of OH⁻, of which the surface character and the reduction of Si—O bond strength of kaolinite are influenced most greatly by OH⁻. Therefore, the desilication of kaolinite in alkaline solution at relatively low temperature is easier.

The extraction kinetics of rhenium(Ⅶ) or molybdenum(Ⅵ) with trialkyl amine (N235, R₃N, R=C₈–C₁₀) dissolved in heptane were investigated by constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. The influence of stirring speed, temperature, specific interfacial area, extraction concentration and chlorine concentration on the extraction of both metals was studied. It is concluded that the extractions of Re(Ⅶ) and Mo(Ⅵ) both take place at the liquid−liquid interface, while the extraction regimes are chemically-controlled for rhenium and mixed controlled for molybdenum, respectively. The extraction rate equations and the rate-determining step were obtained under the experimental conditions, and the extraction rate constant of Re(Ⅶ) or Mo(Ⅵ) with N235 was calculated. These obtained kinetics parameters are different between Re(Ⅶ) and Mo(Ⅵ), which provides better possibilities for Re(Ⅶ) and Mo(Ⅵ) separations at proper conditions.

To clarify the role and mechanism of Acidithiobacillus ferrooxidans (A. ferrooxidans) in bio-electro-generative-leaching (BEGL), an experiment was made on the electro-generative leaching of chalcopyrite-MnO₂ in the presence of the bacteria which grew respectively in Fe(Ⅱ) and S⁰ media. A dual cell system with chalcopyrite anode and MnO₂ cathode was used to study the relationship between time and both of electric quantity and dissolved rate of the two minerals in BEGL. The results show that the dissolved rates for Cu²⁺ and Fe²⁺ under the action of the bacteria cultivated by S⁰ medium are almost 2 times faster than those by Fe(Ⅱ). And the leaching ratio for Mn²⁺ and the electric output increase by near 3 times. The oxidation residue of chalcopyrite was characterized by SEM and XRD, whose patterns are similar to those of raw ore in BEGL. The mechanism of anodic reaction for CuFeS₂-MnO₂ leaching in the presence of A. ferrooxidans cultivated by S⁰ medium is proposed as a successive reaction of two independent sub-processes. The first stage is the dissolution of chalcopyrite to produce Cu²⁺, Fe²⁺ and sulfur, and the second stage is bio-oxidation of sulfur, which is the control step of the process. However, dissolution of MnO₂ lasts until the reaction of chalcopyrite stops or the ores exhaust in two types of leaching.

A dual cell system was used to study the electrogenerative leaching sphalerite-MnO₂ in the presence and absence of Acidithiobacillus thiooxidans (A. thiooxidans). The polarization of anode and cathode, and the relationship between the electric quantity (Q) and some factors, such as the dissolved rate of Zn²⁺ and Fe²⁺, and the time in the bio-electro-generating simultaneous leaching (BEGL) and electro-generating simultaneous leaching (EGL) were studied. A three-electrode system was applied to studying anodic and cathodic self-corrosion current, which was inappreciable compared with the galvanic current between sphalerite and MnO₂. The results show that the dissolved Zn²⁺ in the presence of A. thiooxidans is nearly 43% higher than that in the absence of A. thiooxidans; the electrogenerative quantity in the former is about 150% more than that in the latter. The accumulated sulfur on the surface of sulfides produced in the electrogenerative leaching process can be oxidized in the presence of A. thiooxidans, and the ratio of biologic electric quantity reaches 27.9% in 72 h.

The potential—pH diagrams of the Cr-H₂O system at temperatures of 298, 323, 373 and 423 K were established through thermodynamic calculation with coupling of experimental results. The potential—pH diagram at 298 K agrees well with the previously reported results. Based on the potential—pH diagrams of the Cr-H₂O and Fe-H₂O systems, IR spectra and XRD pattern, the existence forms of iron in the potassium chromate were analyzed, and the methods of iron removal were investigated. The results show that the existence forms of iron in the potassium chromate are potassium ferrate. These results are instructive and helpful to the hydrometallurgical processing of chromite ore.

The physicochemical properties are very important in theoretical investigation of aqueous electrolyte solution and industrial design of hydrometallurgical processes. In the green hydrometallurgical process of chromite ore with sub-molten salt medium of KOH, the ternary system of KOH+K₂CrO₄+H₂O is essential to process control and industrial operation. In order to satisfy the needs of both fundamental research and industrial application, the dynamic viscosity (η) and density (ρ) of mixed aqueous electrolyte solution of KOH and K₂CrO₄ were measured over a temperature range from 15 to 60 ℃ by using Ubbelohde-type capillary viscometers and a series of densimeters, respectively. The temperature is controlled to an accuracy of ±0.01 ℃ throughout the experiment with thermostat. The dynamic viscosity and density of the ternary systems are performed as functions of chromate and hydroxide concentration and temperature. The regression equations for viscosity and density are obtained with a least-square method and the calculated values are consistent well with the experimental data. The semi-empirical equation obtained will be helpful and instructive to industrial application.

Na₄EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of sodium aluminate solution, particle size distribution (PSD) and morphology of precipitated gibbsite were investigated using titration method, particle size analyzer and scanning electron microscope (SEM), respectively. The results show that the two additives can accelerate the seeded precipitation rate of sodium aluminate solution. At relatively high concentration, the facilitative effect of EDTA on sodium aluminate solution is more obvious than that of Na₄EDTA. EDTA makes gibbsite particles thinner than Na₄EDTA. The Na⁺ and H⁺ result in  the different effects on the seeded precipitation rate of sodium aluminate solution in spite of the same EDTA anion in the two additives.

In order to precipitate cobalt(Ⅱ) in cobalt chloride solution, a novel method using ozone as the precipitant for its strong oxidability was proposed. The results show that the precipitation reaction is diffusion-controlled. The main factors affecting the oxidation rate such as the stirring speed, solution temperature, ozone partial pressure, initial concentration and flow rate were investigated. The kinetics equation of each condition was established. The results indicate that the oxidation rate is independent of the initial concentration or solution temperature. The oxidation rate increases obviously with increasing the stirring speed. The linear relationship between ozone partial pressure or flow rate and oxidation rate is found.

The concentrations of S₂O₃²⁻ and SO₃²⁻ were measured in gold leaching systems, including thiosulfate system, polysulfide system and the modified lime sulfur synthetic solution (ML) system in the process of chemical reaction. The interactions among S₂O₃²⁻, SO₃²⁻ and S²⁻ were discussed. The behavior mechanism of sulfur-bearing reagents was proposed to describe the process reactions and their Gibbs free energy. The proper quantity oxygen and SO₃²⁻ reduce decomposition of S₂O₃²⁻ and react with sulfur derived from the decomposition of S_X²⁻. So, SO₃²⁻ ions have action to stabilize sulfur-bearing system and are favorable to leach gold.

The effects of arsenic on the cathode polarization process in zinc electrowinning, its kinetics equation, parameters and polarization mechanism were studied by multiple electrochemistry approaches. The experimental results show that, if [As³⁺]≥3 mg/L, electrowinning first enters into stationary passivation range, and then enters into precipitation range, which indicates that the depolarization function of impurity arsenic is zinc electrowinning.

Effect of added Co²⁺(aq) on copper electrowinning was studied using doped polyaniline (Pani) and Pb-Ag(1%) anodes and a stainless steel cathode. The presence of added Co²⁺(aq) in the electrolyte solution was found to decrease the anode potentials. The optimum level of Co²⁺(aq) concentration in the electrolyte, with respect to the maximum saving of power consumption was established. Linear sweep voltammetry (LSV) was used to study the influence of added Co²⁺(aq) on the anodic processes in a copper sulfate-sulfuric acid electrolyte. The oxygen-evolution potential for Pani anode is depolarised at lower current densities (≤0.01 A/cm²) and attains saturation at ρ(Co²⁺)_o≈0.789 g/L; whilst the oxygen-evolution potential for Pb-Ag(1%) anode is depolarised at higher current densities (≤0.02 A/cm²) and attains saturation at ρ(Co²⁺)_o≈1.315 g/L. The preferred orientations of the copper deposits change from (220) to (111) with the addition of 0.394−0.789 g/L Co²⁺ but higher concentrations favor (220) orientation again.