A coating of 316L+x%NbC (x=0,5,10,15) was prepared on the surface of 304 stainless steel by laser cladding, and the effect of NbC content on the phase composition, microstructure, micro-hardness and wear behavior of the prepared coating was then investigated. The results show that with NbC content at 5%-15%, the phase composition of coating consists of NbC, Cr₇C₃ and γ-Fe; while the prepared 316L coating by adding NbC has its matric structure significantly refined, and traces of Nb element are dissolved in the phase of γ-Fe, forming a gap solid solution. By adding NbC, the micro-hardness and wear resistance of coating are substantially improved, but the friction coefficient and wear rate are remarkably decreased. It is shown that the coating of 316L+15%NbC has micro-hardness as high as 381HV_0.3, friction coefficient of 0.437 by average (41% lower than the coating 316L), and wear rate of 2.95×10⁶ μm³/ (N·m), (around 50% compared to 316L coating).

An experimental study was carried out to comprehensively recover lead and zinc resources from a refractory pyrrhotite lead-zinc sulfide ore grading 1.84% Pb and 4.53% Zn respectively. And a new ester collector of ZQ-11, in combination with 25^# dithiophosphate, was used to float lead minerals. After that, magnetic separation process was adopted to treat lead flotation tailings for desulfurization, and butyl xanthate was then used to collect zinc minerals from the desulfurized tailings. A closed-circuit test resulted in 89.49% Pb recovery into a lead concentrate grading 62.57% Pb and 3.30% Zn respectively, and 85.79% Zn recovery into a zinc concentrate grading 43.37% Zn and 1.01% Pb respectively. It is concluded that this process can actualize an effective recycle of refractory pyrrhotite-type lead-zinc sulfide ore.

Arsenic-iron slag were treated by using magnetizing reduction for recovering arsenic and iron therein, and the experimental conditions were optimized as follows: roasting at 650 ℃ for 180 min, adding carbon at an amount of 25% and protecting with argon. Under such conditions, the arsenic volatilization rate reached 97.25% and arsenic content in the roasted slag decreased to 0.61%. It is found that arsenic can be recovered in the form of As₂O₃, with purity up to 99.13%, while iron therein is magnetized and can be recovered in the form of Fe₃O₄ by magnetic separation. Therefore, this process can actualize the resource utilization of arsenic-iron slag.

The adsorption of phosphate ions and oleate ions onto CO₃^2- defects on dolomite (104) surface was studied by using density functional theory (DFT) calculation. The results showed that the CO₃^2- defects that were generated due to dolomite dissolution led to the enhancement of the activity of metal atoms on the surface, which was beneficial to the interaction between anions and mineral surface. The adsorption energies of H₂PO₄^- onto calcium atoms on the ideal dolomite surface and the defective dolomite surface were calculated to be -183.30 kJ/mol and -561.24 kJ/mol, respectively. Based on the calculation of density of states, it was found that after adsorption of H₂PO₄^- onto the calcium atoms on the surface of defective dolomite, the adjacent magnesium atoms still had strong activity, and the adsorption energies of oleate ions onto the magnesium atoms on the surfaces of the ideal dolomite and defective dolomite were -52.29 kJ/mol and -489.43 kJ/mol, respectively. Phosphoric acid ions and oleic acid ions were adsorbed together on the surface of dolomite, resulting in the floating of dolomite.

For the copper-containing acidic wastewater generated during underground mining process of a copper mine, a new processing technique consisting of copper recovery by replacement with iron filings, neutralization of alkaline tailings overflow, and treatment of coagulation and sedimentation was studied, and the effects of adding amount of iron filings, replacement reaction time and stirring speed on copper replacement rate were all investigated. And then, experiments on the proportion of required alkaline tailings overflow for neutralization of acidic wastewater and on toxicity characteristic leaching of neutralized sludge were performed, as well as the kinetics of replacement process was also studied. The results show that this new processing technique can produce sponge copper grading 35.6% Cu at 92.7% recovery, and the acidic wastewater after treatment can be up to the standard and directly discharged, with the cost of treatment agent at 0.95 yuan/t. Due to no hazardous waste generated, this processing technique can bring remarkable economic and environmental benefits.

In order to explore the current status of sustainable development of mining enterprises in China in recent years, static and dynamic analysis was performed for ecological efficiency of mining enterprises in 11 different sub-sectors in China from 2012 to 2020, in which SBM-DEA model with undesirable output taken into consideration was adopted in combination with GML index. And regression testing was also conducted in combination with Tobit model for the influencing factors for ecological efficiency. Results show that during the sampling period, the ecological efficiency of mining enterprises was generally trending up, but there was some difference in the efficient frontier, and great difference between each sub-sector. It is found that the technological advancement is the main driving factor for improving ecological efficiency, which is also positively correlated with high degree of interaction with outside world, but negatively correlated with environmental regulations. At last, as for improving ecological efficiency of mining enterprises, some recommendations are proposed for the state, mining sector and mining enterprises.

The influence of Ce³⁺ in the sodium oleate system on the flotation of fluorite and calcite was investigated by flotation test, zeta potential measurement, solution chemistry study and X-ray photoelectron spectroscopy analysis. The results reveal that in the sodium oleate system, Ce³⁺ with a low concentration exists on fluorite surface in the form of CeF₃·0.5H₂O(s) under acidic and neutral conditions, therewith, fluorite can be activated to generate more active sites for the adsorption of sodium oleate. Meanwhile, Ce³⁺ can be adsorbed onto calcite in the form of Ce₂ (CO₃)₃·8H₂O(s). There are more active sites generated as well, but calcite may be depressed as the hydrophilic nature of Ce₂ (CO₃)₃·8H₂O(s) and the spatial site barrier effect of crystalline water hinder the adsorption of sodium oleate. In alkaline pulp, Ce³⁺ is mostly precipitated to form Ce(OH)₃(s) and depresses both fluorite and calcite as Ce(OH)₃ (s) can consume sodium oleate and reduce its adsorption on both minerals.

A self-designed multi-functional rod was adopted to provide a real-time monitoring of surrounding rock stability during the excavation of a metal mine, and the variations of vertical stress of rock stratum and surrounding rock vibration occurrence within the monitoring range of the multi-functional rod during stoping were all recorded. It is found that the stress and peak ground velocity of the surrounding rock are all trending up as excavation area increases, which reflects that more fractures occur inside the surrounding rock, leading to lower degree of stability for the surrounding rock, and the excavation damage zone (EDZ) goes deeper. As for mines supported by top threaded anchor bolts, the EDZ evolution process and caving of rock mass can be more effectively controlled when the thread length of rod is greater than the depth of EDZ. After one month's mining of this stope, it is found that the vertical stress of the rock stratum within the monitoring length of the multifunctional rod increases by 3.9 MPa due to the subsidence of the stratum, and the frequency of vibration occurrence meets the blast vibration standard for safety permit in China. It is shown that the surrounding rock has a good stability based on the comprehensive evaluation.

A flotation experiment was performed with medium grade siliceous and calcareous collophanite from Guizhou Province for determining the optimum technical process and reagent system. With the process flow consisting of three roughing, one cleaning and one scavenging, a high quality phosphate concentrate grading 34.07% P₂O₅ at 75.38% recovery was finally obtained. The adsorption behavior of collector SGC-01 on the apatite surface during the direct flotation process was also investigated by using Zeta potential, infrared spectrum and QCM-D. The results show that SGC-01 can be chemically adsorbed onto apatite in various forms, and presents a better flotation performance compared with sodium oleate.

A₂B₇-type La_xY_3-xNi_9.7Mn_0.5Al_0.3 (x=0.2, 0.4, 0.6, 0.8, 1.0) hydrogen storage alloys with different La/Y ratios were prepared by vacuum melting. The effect of partial substitution of La by Y element on the structure and properties of the alloy was systematically investigated by using XRD, SEM, gas-phase PCT curves and electrochemical charge-discharge cycle curves. The experiment results show that the prepared alloy has Ce₂Ni₇ as its main phase and contains a small amount of Gd₂Co₇, PuNi₃ and LaNi₅ phases. The abundance of main Ce₂Ni₇ phase increases gradually with the increase of La/Y ratio. When the La/Y ratio is 1∶2, the LaY₂Ni_9.7Mn_0.5Al_0.3 alloy has the maximum hydrogen absorption capacity of 1.317%. After 150 charge-discharge cycles, the alloy can have its highest capacity retention rate at 54.2%.