The phase structure, microstructure and mechanical properties of Fe_46-xNi₂₀Co₂₀Cr₁₀V₄Al_x (x=5, 8, 12, 15) high-entropy alloys with different Al contents (atom fraction, %) were systematically investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and performing uniaxial tensile test. The results show that with the increase of Al content, the phase structure of Fe_46-xNi₂₀Co₂₀Cr₁₀V₄Al_x high-entropy alloys transforms from single-phase structure of face-centered cubic (FCC) to dual-phase structure of FCC and body-centered cubic (BCC). Also, the strength increases and ductility decreases. The Fe₃₄Ni₂₀Co₂₀Cr₁₀V₄Al₁₂ high-entropy alloy annealed at 900 ℃ exhibits an excellent strength-ductility balance, with yield strength, tensile strength and elongation to failure at 593 MPa, 1009 MPa and 32.13%, respectively. With Al content of 5%, the as-cast and annealed high-entropy alloys remain single FCC phase. However, with Al content of 8%, 12% and 15%, the high-entropy alloys all become FCC-BCC phase. The annealing treatment promotes the precipitation of BCC phase, and the proportion of BCC phase increases with increasing annealing temperature.

An experimental study on a metallurgical grade fluorite concentrate with CaF₂ content of 70.34% was conducted to upgrade fluorite concentrate quality by reducing impurities therein. The results of the full process test show that by adopting a process of high intensity magnetic separation for reducing silicon, followed by flotation of non-magnetic minerals for reducing calcium, the experiment produces a fluorite concentrate grading of 91.95% CaF₂ at 76.52% recovery, with a yield of 58.30%. It is shown that the concentrate meets the raw material standards for anhydrous hydrofluoric acid production.

In order to determine a new type of gold leaching system, which can not only bring good leaching effect with low consumption of thiosulfate, but also make the gold in the lixivium to be efficiently recovered, the leaching effects of gold with thiosulfate catalyzed by different combination of metal ions and organic ligands were compared, and then the gold in the lixivium was recovered by resin adsorption. The results indicate that the Ni²⁺-glycine-thiosulfate system can bring good Au leaching effect, showing Au leaching rate up to 89.72% with thiosulfate consumption of 15.28 kg/t. During the gold leaching process in this system, glycine catalyzes the coordination of Au⁺ with S₂O₃^2- and also stabilizes Ni²⁺ under alkaline conditions, and Ni (C₂H₄NO₂)₂⁰ catalyzes the reduction of O₂. When Au is recovered by resin adsorption, Ni ions in the lixivium are hardly adsorbed on the resin, and do not compete with Au ions for adsorption, resulting in Au adsorption rate up to 98.13%. Then, only one-step process is required for desorption of gold-loaded resin, that is, Au can be directly desorbed.

A free fall backfill (FFB) system with high-concentration slurry in a mine was taken as an example to study pipeline parameters and resistance characteristics of FFB system by conducting theoretical analysis, laboratory test and verification with field measurement. The results show that the FFB system has many working procedures, with flowrate for normal backfilling fluctuating within the range of 100-240 m³/h, and the pressure at 1.2-2.2 MPa. The flowrate at specific points of the pipeline presents a quasi-normal distribution, averaging 190 m³/h. There are two characteristic peaks for the pressure, being 1.86 MPa and 3.04 MPa, respectively. The parameters at a single point of pipeline cannot be used to analyze and judge the working conditions, such as pipe blockage and leakage. The pressure difference and flowrate difference between sections of the pipeline present obvious normal distribution, with mathematical statistics expectations of 4.62 m³/h and 0.64 MPa, respectively. The difference in instantaneous flowrate and pressure can be used to judge blockage and leakage of the pipeline. The flow resistance in the laminar-turbulent transition zone predicted by the Swamee-Aggarwal formula is 2.08 MPa/km, which is consistent with the measured value of 2.15 MPa/km.

The effects of Zr content on solidification process of Al-Si-Mg-Mn alloy, and its microstructure and mechanical properties after aging treatment were investigated by means of numerical simulation, microstructure observation and mechanical property testing. The research results reveal that with increasing Zr content, the solidification path of the alloy become significantly different, and grains evolve from initial dendrites to equiaxed grains. After aging treatment at 175 ℃ for 7 h, an addition of Zr can significantly improve the hardness of the alloy. The addition of Zr promotes the precipitation of precipitates at lower aging temperature, which may be attributed to grain refinement of Zr, thus leading to improved diffusion efficiency. The main precipitates of the alloy are β″ phase and Q′ phase during peak aging.

Hydrothermal carbon generated by hydrothermal carbonization of waste jujube branches was activated with zinc chloride as an activator, and a kind of modified biochar was prepared with highly porous and aromatic structure on its surface, which was then used to adsorb Zn²⁺ in aqueous solution. It is shown that for the solution with pH of 9 and initial Zn²⁺ concentration of 30 mg/L, after 80 min adsorption at a temperature of 55 ℃ by adding 700 mg/L modified biochar, the removal rate of Zn²⁺ therein exceeds 99%. The adsorption process is well-fitted to the Freundlich adsorption model, indicating that the adsorption process with the modified biochar is a multilayer molecular adsorption. The removal rate of Zn²⁺ by the modified biochar, after 5 cycles of adsorption and desorption, can still remain over 97%.

The dissolution characteristics and mechanism of heavy metal ions (As, Cr, Cu, Mn, Ni, Pb) and Na⁺, K⁺ in red mud were studied in a simulated natural environment. The results show that the dissolution of heavy metal ions, Na⁺ and K⁺ out of red mud can be promoted by reducing pH value, increasing contact time, raising leaching temperature, and increasing liquid-solid ratio. After dissolution, the characteristic peak values of calcite, magnesium chlorite, gosilicate and triploidite significantly become lower, and elements of As, Cr, Ni, Cu, Mn, Na and K, after dissolution out of red mud, exist in the forms of As₂O₃, Cr³⁺, NiO, CuO, MnO, Na⁺ and K⁺.

In order to solve the problem of parameter selection for smooth blasting in tunnel/roadway excavation, a parameter selection model based on random forest algorithm was constructed. The input parameters in the model include quality classification BQ of surrounding rock, tunnel (roadway) section area and borehole diameter, and the output parameters include minimum burden, borehole spacing and borehole depth. Then, 24 training samples and 7 test samples were used for training and testing of model, and the results show that the relative errors between the output parameters of borehole spacing, minimum burden, borehole depth and the corresponding parameters of test samples are 17%, 8.8% and 22% respectively on average, indicating that the model is good in selecting minimum burden, but less effective in selecting blasthole spacing and blasthole depth.

Aiming at the problem of insufficient sorting of low-grade rock ore in the western Inner Mongolia region, the processing technique and equipment were improved to solve the problems including the concentrate of low-grade rock ore with the grade failing to meet the requirement and the grain refinement. By applying automation and intelligent technologies in new equipment, the processing index can be largely improved, which complies with the requirement for the development of green and intelligent mine. Simultaneously, by implementing remote connection, the connection of remote-control center and remote units can be actualized, facilitating the communication between customers and equipment manufacturers, tracking of equipment operation status, as well as the maintenance of operation indicators and observation of component operation status.

High gradient magnetic separation technique was adopted to separate the (tantalum-niobium)-tin bulk concentrate obtained from gravity separation. The effects of magnetic intensity, pulsating frequency, magnetic rod matrix diameter and rotating speed of ring on (Ta-Ni)/Sn separation efficiency were studied. The test results show that, from the bulk concentrate with grades of Ta, Ni and Sn respectively as 11.65%, 9.33% and 19.59%, the final tantalum-niobium concentrate containing 22.31% Ta, 17.38% Ni and 3.22% Sn can be collected with the recoveries of Ta, Ni and Sn respectively as 95.48%, 92.88% and 8.20%, respectively. Meanwhile, a tin concentrate with Sn grade of 35.87% and Sn recovery of 91.80% can be obtained. The tantalum-niobium and tin minerals can be effectively separated.