The progress in the research of micro-fine mineral flotation process is reviewed in terms of grinding, pulping, separation, and finally a prospect for the research direction of micro-fine mineral flotation process is presented.

In order to improve the accuracy of flatness pattern recognition, a flatness pattern recognition method based on modified seagull optimization algorithm (MSOA) and Elman network is proposed. The weight threshold of Elman network is optimized with MSOA and then used for flatness pattern recognition. 20 sets of data are chosen for testing, and the obtained results are compared respectively with the flatness pattern recognition results based on BP neural network and traditional Elman network. It is found that algorithm method proposed in this paper has higher accuracy and better effect, with the mean square error lower than other algorithms by two orders of magnitude.

In order to understand carbon performance of the mining sector in Hunan Province, the carbon emissions and carbon performance of the mining sector in Hunan Province were calculated based on the latest statistical data of national economic accounting, and factors influencing carbon performance were analyzed based on the established model. It is shown that the carbon performance of Hunan's mining sector was at a relatively low level from 2010 to 2020, and there was great difference in carbon performance of sub-sectors. Factors of asset size and energy efficiency had a positive impact on carbon performance, while factors of asset liability ratio and energy structure had negative constraints on carbon performance. Achieving economies of scale, improving energy efficiency, optimizing energy structure and maintaining a stable liabilities-to-assets ratio made sub-sectors of non-ferrous metal and gas production and supply in the front rank in terms of carbon performance. However, decreasing returns of scale in sub-sectors of coal mining and washing, as well as unreasonable energy structure and low energy efficiency in coal sub-sector led to the carbon performance of coal sub-sector ranking at the bottom. Consequently, it is suggested that the mining sector in Hunan Province should optimize its energy structure, accelerate low-carbon innovation, and increase various energy efficiency, so as to improve their carbon performance.

Polycrystalline Cubic boron nitride (PCBN) composites were synthesized by adding a certain amount of Al and Ti, with TiN as the main binder. The effects of temperature (1 300-1 600 ℃) on the composition, microstructure and mechanical properties of the PCBN composites sintered with TiN-Al-Ti in combination with CBN were investigated. It is found that the phases of PCBN specimen are mainly composed of BN, TiB₂, TiN and AlN, and almost all Ti reacts with CBN in the sintering process to form TiN and TiB₂ phases. The relative density, flexural strength and hardness of PCBN are generally trending up with the rising of sintering temperature. And composite material with good comprehensive performance can be obtained at a sintering temperature of 1 500 ℃, showing its relative density of 99.1%, flexural strength of 807.8 MPa, fracture toughness of 6.2 MPa·m^1/2, and micro-hardness of 3 233HV.

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.

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%.

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).

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.

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.

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.