As for a zinc concentrate collected from mineral processing of a lead-zinc ore, an experimental study was carried out to reduce the carbon content therein. With soluble starch as the carbon depressant, a concentrate with Zn grade of 48.71%, carbon content of 0.86% and Zn recovery of 90.28% was obtained from a closed-circuit test. Compared with the on-site indicators, both the Zn grade and recovery of concentrate are increased by using this new process, while the carbon content therein is reduced to less than 1%, showing a remarkable carbon-reduction effect.

High pressure grinding roll (HPGR) was used to comminute a copper smelting slag. An open-circuit test, edge-product cycling test and closed-circuit ball mill test were carried out using HPGR. The particle size of various products were measured, and the grinding results after HPGR were compared with those obtained after jaw crushing. The results show that after copper smelting slag is processed using HPGR and ball mill, the fine particle fraction of the products increases obviously, and the grindability increases by about 36 percentage point. It can be concluded that HPGR approach favors upgrading of grinding efficiency and beneficiation index in processing copper smelting slag.

In order to recover and utilize high value-added iron phosphate waste, an experimental study was carried out by adopting a process consisting of hydrochloric acid leaching, replacement of iron powder for copper removal, and hydrolyzation and chemical precipitation for removal of titanium and aluminum therein. The results show that after 1 h leaching at 60 ℃ with hydrochloric acid concentration of 25%, liquid-solid ratio of 6 mL/g, the leaching rate of iron can be up to 98.7%. And then after 35 min reaction at 60 ℃ with the initial pH of the solution controlled at 0.6, the addition of iron powder at an amount of 0.55 times of the molar number of iron in the leaching solution, the removal rate of copper and titanium can reach 96.2% and 83.6% respectively. By the following process of hydrolyzation and chemical precipitation with sodium fluoride 8 times of the molar number of aluminum, the removal rate of titanium and aluminum can reach 97.6% and 99.3% after 30 min reaction at 40 ℃ with pH of 1.9. It is shown that the content of impurities in the leaching solution meets the requirements for the subsequent synthesis of iron phosphate for batteries.

Experiments were carried out to compare dephosphorization performance of CaCO₃, Na₂CO₃ and CaF₂ in direct reduction roasting process of high-phosphorus hematite. It is found that Na₂CO₃ presents the best dephosphorization performance, followed by CaCO₃. The molecular dynamics simulation was conducted to calculate the distribution of bridging oxygen and the mean square displacement (MSD) of oxygen atoms during the roasting process of the system with three different additives respectively, and the dephosphorization mechanism of CaCO₃, Na₂CO₃, CaF₂ during the direct reduction process of high-phosphorus hematite was explored. The results show that the mechanism of dephosphorization by additives is to inhibit reduction of apatite by increasing the content of free oxygen or the MSD of oxygen atoms in the system and reducing the oxygen atoms shared by Si and P in the system. It is found that the dephosphorization performance of additives is positively correlated with the MSD of oxygen atoms in the system.

Alkali leaching of indium from zinc indium ferrite (ZnFe_2-xIn_xO₄) was strengthened by applying a combination of ultrasound and microwave. The results show that there are not a great amount of solid solution of indium in the octahedral lattice of ZnFe_2-xIn_xO₄, and the maximum solid solution approaches 4.0% in a mass fraction (x=0.088). The leaching rate of indium can be enhanced by the external fields in the following descending order: a combined application of ultrasound and microwave, single application of microwave, application of ultrasound followed by microwave or microwave followed by ultrasound, and single application of ultrasound. It is shown that the leaching rate of indium can be up to 56.6% with a combined application of ultrasound and microwave, but only reach 30.2% by singly applying ultrasound. During the alkaline leaching under the external fields, In³⁺ can be released from the lattice, while the octahedral lattice of zinc ferrite will not collapse. With a combined application of ultrasound and microwave, more In³⁺ can be released, leading to lattice constant becoming much smaller. The XRD spectrum shows obvious reduced intensity and rightward movement of diffraction peaks.

In order to avoid formation of material ring in a rotary kiln caused by kiln phosphoric acid process, a technique of high-temperature consolidation of pellets was proposed, and the effects of types of binder, temperature and time of consolidation on the strength and reducibility of phosphate ore pellets were investigated. The results show that consolidation at a temperature over 800 ℃ with bentonite as binder can lead to the pellets with compressive strength and drop numbers obviously higher than those with sodium humate as the binder. With an addition of carbon at 1.4 times of the theoretical amount, CaO and SiO₂ at a molar ratio of 0.35, an addition of bentonite at an amount of 1.5% of the total material weight, consolidation at 1 000 ℃ for 30 min results in the produced pellets with compressive strength of 345.36 N and drop numbers of 33.50.

A kind of contaminated paddy soil was taken for pot experiment by adding FeSO₄ to investigate the impact of FeSO₄ on the formation of iron plaques on the root surface and the migration of the Cd from Cd-contaminated paddy soil. Results show that with the addition of FeSO₄ increased from 0 to 320 mg/kg, the pH value of the paddy soil tends to decline, maximally by 0.70. The TCLP-Cd content in the potting soil rises to a certain extent compared to the control group. The addition of FeSO₄ significantly reduces the Cd content in leaves, husks, and brown rice, as well as effectively increases the amount of root iron plaque, thus the absorption of Cd in the soil by rice is moderately controlled. However, the addition of external iron resource can bring impact to the pH of soil and bioavailability of Cd, so it is recommended that in practical operation, FeSO₄ should be added with some alkaline restorative materials such as lime to contaminated paddy fields for enhancing the control.

High purity sodium aluminate was prepared with sodium aluminate solution by adopting a process consisting of evaporation, cooling crystallization, and dewatering for purification. The effects of additives on caustic ratio and crystallization products, as well as the function and behavior of sodium aluminate solution during evaporation and crystallization were studied. The results show that with NaOH as an additive, the caustic ratio of the solution system can be increased, and the product from evaporation and crystallization can be converted to NaAlO₂. By using NaAlO₂ as seed crystal and adjusting the caustic ratio of system to 1.36 with NaOH, the product of NaAlO₂ with purity of 88.1% can be obtained after evaporation at 100 ℃ for 2 h with stirring rate of 300 r/min. Then, after 1 h dewatering at 200 ℃ and 1 h purification with alcohol at 100 ℃, a kind of solid NaAlO₂ can be obtained with purity of 93.8% and crystal particles of 5-25 μm.

With aluminum hydroxide powder as raw material, aluminum hydroxide was roasted into α-Al₂O₃, and the phase transformation and microstructure change during the process were investigated. Then, the kinetics of the calcination process was calculated by simulation with multiple scanning method. It is found that the optimum conditions for aluminum hydroxide calcinated into α-Al₂O₃ are as follows: calcination temperature of 1200 ℃, time of 2 h, heating rate of 5 ℃/min. Three endothermic peaks can be observed during the calcination process of aluminum hydroxide, corresponding to three weightlessness stages. In the first stage of reaction, the function of mechanism is G (α)=[(1-α)^-1/3-1]², the average activation energy is 91.16 kJ/mol and the pre-exponential factor is between 17.00×10⁹ and 44.03×10⁹ min^-1. In the second stage of reaction, the function of mechanism is G (α)=α², the average activation energy is 106.2 kJ/mol and the pre-exponential factor is between 7.70×10⁹ min^-1 and 18.60×10⁹ min^-1. In the third stage of reaction, the function of mechanism is G (α)=α^1/4, the average activation energy is 235.42 kJ/mol, and the pre-exponential factor is between 39.94×10⁹ and 50.79×10⁹ min^-1.

Based on the studies of catalytic pyrolysis for high-sulfur waste residue (HSWR), it is found that after 90 min pyrolysis at a temperature of 600 ℃, with Fe₂O₃ as a sulfur fixation agent in a mass ratio of 1.5∶1 with HSWR, the total desulfurization rate can be around 85%. The volatile sulfur-containing complex organic matter in HSWR could be transformed into stable inorganic matter, among which the amorphous sulfur could be transformed into crystalline sulfur with purity over 95%. In the residue left after pyrolysis process for desulfurization, the main components include inorganic salts such as sodium sulfate and carbon black. The exhaust gas is mainly composed of simple molecular organics such as CH₄ and C₂H₄, and a small amount of inorganic compounds such as CO, SO₂, CO₂ and HCl. The pyrolysis process for desulfurization consists of four stages: firstly, the amorphous elemental sulfur is vaporized and then crystallized to form crystal sulfur; secondly, as for the elemental sulfur with attachment of organic matter and in a relatively more stable structure, its bond with the hydroxyl or carboxyl of organic phase is broken, leading to sulfur emitted into the atmosphere; at the third stage, the sulfur-containing organic phase is deactivated at the methylene and submethyl sites to form HCl, H₂S and carbon black, which are then adsorbed by sulfur-fixation agent and converted into sulfate; at the fourth stage, the carbon-carbon bond between nitrogen heterocyclic hydrocarbons becomes unstable after grouping, and is broken into small organic molecules such as CH₄ and C₂H₄, as well as carbon black and a trace of H₂. Meanwhile, C—N/C—NH_x bonds are broken into NO_x/NH₃, and C—S/C—SO₃H bonds are broken into H₂S and SO₂, which are then adsorbed by sulfur fixation agents and converted into sulfate.