A low-grade manganese carbonate concentrate was processed by adopting direct sulfuric acid leaching. The effects of leaching parameters on the leaching rates of manganese, calcium and magnesium were investigated, and changes in phase composition and microstructure before and after leaching process were also discussed. The results show that under the optimized conditions, including acid and ore in a mass ratio of 0.6, liquid-solid ratio of 4∶1, leaching temperature of 60 ℃, and leaching time of 3 h, the leaching rates of manganese and magnesium reach 99.36% and 83.97% respectively, while calcium is hardly leached out and mainly left in the residue as calcium sulfate.

As for a gold-bearing pyrite from Hebei Province, the influence of four oxidants, including H₂SO₄, H₂O₂, HNO₃ and KMnO₄, on its floatability was investigated, and the adsorption of collectors on pyrite was also explored by infrared (IR) analysis and electrochemistry measurement. The flotation test shows that with H₂SO₄, H₂O₂ and HNO₃ as oxidants, moderate oxidation can promote the floatability of pyrite, while the oxidation of KMnO₄ can obviously depress the floatability of pyrite. The IR analysis shows that the effects of these four oxidants on pyrite-collector interaction are in the following descending order: HNO₃>KMnO₄>H₂O₂>H₂SO₄. The oxidation of KMnO₄ may passivate pyrite and reduce its floatability. Electrochemical analysis shows that H₂SO₄ and HNO₃ have obvious oxidation effects on pyrite. By increasing oxidant concentration, the double xanthate formed on pyrite due to its reaction with xanthate will be oxidized by H₂O₂ solution, and the hydrophobic layer on pyrite will be destroyed, leading to the decline of pyrite's floatability.

In a Hunan polymetallic ore concentrator, the tailings with CaF₂ grade of 26.56% exhibit certain economic value. However, due to the influence of residue reagents in the upstream processing of main tungsten-molybdenum-bismuth minerals and the interference of calcium-bearing gangue, it is extremely difficult to recover fluorite from the tailings. A process consisting of selective regrinding, tailings discarding by high intensity magnetic separation, and fluorite flotation was adopted with a new reagent NH-1 as activator of fluorite, CY-63 as collector of fluorite, SWG+SZY as depressant of silicate and micro-fine gangue, and CYAB as depressant of calcareous gangue. As a result, fluorite concentrate with CaF₂ grade of 90.50%, CaCO₃ content of only 1.35% and CaF₂ recovery of 79.50% was finally reclaimed in the closed-circuit test. It is concluded that such tailings resources can be comprehensively utilized by adopting this process.

A thermodynamic analysis based on HSC Chemistry software reveals the phase evolution of main metals in the production of nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the optimal process conditions for obtaining medium-grade nickel matte by sulfidation smelting were also analyzed. Theoretical calculation shows that the electroplating sludge with grades of Cu and Ni at 3.0% and 3.5% respectively is smelted at a temperature of 1 300 ℃, with calcium sulfate as a sulfurizing reagent under a smelting atmosphere with in a volume ratio of 60%-75%, and the actual usage of sulfur 1.6-2.0 times the theoretical value. It is expected that medium-grade nickel matte with Fe content less than 20% can be obtained, and the contents of Cu and Ni in the slag with S ratio in the preferred range can be less than 0.20% and 0.43% respectively. It is shown that recovery rates of Cu and Ni exceed 95% and 90% respectively, and the fixation rate of Cr in the slag is over 99.9%. According to the statistical results of production samples, the distribution behavior of Cu, Ni and Cr is basically consistent with the thermodynamic analysis results. This proves that the established mathematical model has good reliability and is of certain guiding significance for production.

A chrysoberyl-type beryllium ore from Xinjiang, containing 0.102% Be with quartz as the dominant gangue mineral, was taken in an experimental study on sulfuric acid leaching. According to the Box-Behnken experimental design principle, a multivariate regression equation was established by using response surface methodology (RSM) for three influencing factors of leaching effect, including liquid-solid ratio, leaching time and leaching temperature, as well as their interactions. Based on the test of significance of regression equation, the optimum process conditions were determined as follows: roasting temperature of 900 ℃, roasting time of 3 h, sulfuric acid concentration of 50%, liquid-solid ratio of 3.2∶1, leaching time of 4.8 h and leaching temperature of 90 ℃. Under these conditions, the Be leaching rate is predicted to be 89.73%, and an average value is 89.10% based on three parallel experiments, indicating that the established model is accurate. A kinetic model of leaching revealed that the leaching process was controlled by interfacial chemical reactions, with an apparent activation energy at 50.42 kJ/mol.

Multiferroic BiFeO₃ ceramics were synthesized by chemical co-precipitation. The effects of calcination temperature and time on crystal structure, morphology and grain size of products were investigated. Ions of Ba and Ti were doped to modify the properties of BiFeO₃ ceramics for improving ferroelectric and ferromagnetic properties. It is found that compared to the products before doping, the products with Ba doping at an amount of 30% in mass fraction can have the saturation magnetization enhanced from 4.69 emu/g to 4.93 emu/g; while the products with Ti doping at 10% in mass fraction can have the remnant magnetization enhanced from 0.047 emu/g to 0.164 emu/g. The co-doped ceramic samples combine the effects of A-site and B-site doping and exhibit enhanced multiferroic properties.

Bagasse was calcined under an inert atmosphere to produce biochar, which was then mixed with metakaolin and taken to prepare sugarcane bagasse biochar/geopolymer composite microspheres (BGM) by using sodium silicate as an activator. The microstructure of BGM was characterized by XRD, FTIR, BET and XPS, and its adsorption performance for crystal violet (CV) and methylene blue (MB) was also investigated. Results show that the introduction of biochar can enhance the adsorption capacity of metakaolin-based geopolymer microspheres. The adsorption processes of BGM for both dyes follow the pseudo-second order kinetic model. BGM-20 can have theoretically maximum adsorption capacities of 138.031 mg/g for CV and 79.128 mg/g for MB, which can be well-described by the Langmuir isotherm model. Dynamic adsorption experiments revealed that the time required for adsorption of CV and MB by BGM to reach exhaustion exceeded 8 500 min, indicating that BGM can be taken as a fixed-bed adsorption medium material for dye wastewater treatment.

In order to study the high-temperature and high-pressure sintering of binderless tungsten carbide (WC), X-ray diffraction, scanning electron microscopy, universal testing machine, and microhardness tester among others were adopted to characterize the phase composition, microstructure and mechanical properties of the WC samples. The results show that the relative density, hardness and fracture toughness of the samples increase as the sintering temperature rises. It is found that WC sample prepared by sintering at 1 500 ℃ can exhibit excellent comprehensive mechanical properties, with relative density of 99.5%, hardness of 2 885HV, and fracture toughness of 9.50 MPa·m^1/2.

Based on the analysis of patent application trend, major applicants and technological development in recycling of spent lithium iron phosphate batteries by leaching process, a list of key patents of mainstream technologies is presented. The results show that the number of patent applications for recycling of spent lithium iron phosphate batteries by leaching process has been steadily increasing since 2015, and oxidative acid leaching is the mainstream technology at present, with other technologies keeping in pace. However, some outdated technologies are being phased out.

In order to assess stability of the current multi-level mined-out areas in Qijiaojing iron mine in Subei County Bolun Mining Development Co., Ltd.of Western Mining Limited Company, the mine excavation process was simulated with FLAC^3D software to mainly analyze the stress and displacement changes in the mined-out areas after multi-level excavation. The results indicate that the stress in the mined-out areas is predominantly compressive stress, which is primarily concentrated in the roof and pillars of the stope. The maximum compressive stress, approximately 20 MPa, is observed in the pillars of the mined-out area at the 2 150 m level. It is found that the mind-out area has the maximum settlement of 20.30 mm and the maximum horizontal displacement of 7.22 mm, being satisfactorily stable. However, long-term exposure of large-scale mined-out areas may lead to deformation and collapse of pillars. Therefore, regular inspections and reinforcement measures should be taken for the pillars during subsequent production processes.