A kind of spherical Mn₃O₄ was prepared in situ with manganese sulfate solution as raw material and air as oxidant, and the effects of factors, such as time and temperature of reaction process, the pH value of solution and air flow rate, on the properties of synthesized product were investigated. It is found that under the appropriated conditions, including reaction time of 6 h and reaction temperature of 80 ℃, pH of 9 for the solution and air flow rate at 20 L/min, the synthesized Mn₃O₄ has a micro-morphology of regular nano-spherical particles in a uniform size around 150 nm, showing a high crystallinity and a good dispersion. Its specific surface area is 9.85 m²/g and the tap density is 1.93 g/cm³.

The effect of rolling reduction on the microstructure, damping properties and mechanical properties of ZK60 magnesium alloy were studied. The results show that the damping properties of ZK60 magnesium alloy is improved with the increase of rolling reduction. When the strain amplitude is 0.01%, the Q^-1 value increases from 0.012 7 in as-cast state to 0.015 9 on rolling surface (RD-TD) with the rolling reduction of 50%, 0.020 4 on side section (RD-ND) and 0.018 3 on cross section (TD-ND). With the increase of rolling reduction, the (0002) basal texture strength of the alloy increases from 6.547 with the rolling reduction of 10% to 10.690 with the rolling reduction of 50%, which brings a certain impact to the damping properties of the alloy. The increased recrystallization volume fraction in the microstructure is the main influencing factor for the damping properties.

A kind of refractory hematite-limonite ore containing 0.39% lead, 0.30% zinc and 47.04% TFe was taken to perform carbothermic reduction roasting experiment, and the reduction effect of hematite-limonite ore and the removal rate of lead and zinc in the reduction roasting process were all investigated. The reaction fraction, reaction rate and kinetic parameters of the reduction roasting process were studied by means of thermogravimetric analysis at a constant temperature, and the kinetics of carbothermic reduction roasting of refractory hematite-limonite ore was also discussed. After 60-min roasting at 1 200 ℃ with the reducing agents of carbon and oxygen at a ratio of 2.25, the obtained roasted ore was subjected to low intensity magnetic separation, resulting in the yielded iron concentrate grading 89.63% TFe at 86.09% recovery and the removal rates of lead and zinc up to 98.97% and 91.19%, respectively. The iron minerals are mainly transformed into spherical metallic iron particles with iron purity over 99.4% in micro-zone. The reduction roasting process of iron ore follows the shrinkage boundary control reaction mechanism and shrinkage core model. The apparent activation energy is calculated to be 91.37 kJ/mol, and the pre-exponential factor is calculated to be 18.09 min^-1, indicating that the rate-limiting reaction step is solid-state diffusion. This research can provide reference for removing harmful impurities from similar ores by reduction roasting process.

Aiming at the commercial production problems in the usage of high-temperature reagents for the reverse flotation in Qidashan Concentrator, a new laboratory-prepared combined collector (AG-1) was adopted in the reverse flotation of mixed magnetic concentrate at room temperature (20 ℃). The results show that a reverse flotation flowsheet consisting of one stage of roughing, one stage of cleaning and three stages of scavenging, with pulp pH of 11.5, the dosages for depressant (corn starch), activator (CaO) and collector (AG-1) at amount of 950 g/t.100 g/t and 750 g/t, respectively, can yield an iron concentrate grading 68.13% TFe at 88.43% recovery. XRD patterns and optical microscopy visualization of flotation concentrate and tailings show that AG-1 has good selectivity, and can effectively separate valuable minerals from gangue mineral of quartz. Compared with the single collector of sodium oleate or dodecylamine, AG-1 possesses a lower surface tension and a stronger ability in reducing the surface tension of gas-liquid interface, which can better improve mineral hydrophobicity.

For solving the problems of coarse feed size for grinding and high energy consumption in processing Daye Iron Ore, an experiment was carried out with high pressure roller grinding (HPRG) to mill the fine crushing products. The parameters of pressure between rollers, the water content of feed and the rotational speed at roller surface were optimized correspondingly as 10 MPa, 2% and 0.26 m/s. A closed-circuit test shows that HPRG can obviously reduce grinding energy consumption and improve mineral liberation degree. Jaw crushing and HPRG products were then taken as the feed for grinding-flotation test and it is shown that HPRG can improve flotation recovery, with recoveries of Cu, Fe and S all up by 2.56, 1.93 and 1.44 percentage points, respectively.

A hydrochloric acid leaching process was adopted to recover rare earth from rare earth polishing powder waste. The effects of hydrochloric acid concentration, leaching temperature, leaching time and liquid-solid ratio on the leaching rates of rare earth and main impurity Al₂O₃ were investigated, and the leaching mechanism was also discussed. It is found that the optimal conditions for single-stage leaching with HCl system are as follows: HCl concentration of 8 mol/L, leaching temperature of 80 ℃, leaching time of 3 h, and liquid-solid ratio of 4∶1. Under such conditions, the leaching rates of rare earth and Al₂O₃ are 90.81% and 43.68%, respectively．Based on the comparison of results from single-stage leaching, two-stage leaching and three-stage countercurrent leaching, it is shown that the leaching rate of rare earth by three-stage countercurrent leaching can be up to 98.38%. An increased amount of rare earth in the leaching solution is beneficial to the extraction and recovery of rare earth elements in the next step, thus greatly cutting recovery cost.

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 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.

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 investigate the influence of additive on iron recovery from red mud by using a process consisting of magnetizing roasting and low intensity magnetic separation, a kind of red mud containing high content of iron and aluminum was taken for experiments. It is found that addition of dolomite and phosphogypsum won't bring any effect to iron recovery, but sodium sulfate can bring an obvious activation effect. In the experiment, the roasting process ran at 650 ℃ for 90 min, with the addition of sodium sulfate at an amount of 10%, with total gas flow at a rate of 500 mL/min and CO at a volume fraction of 30%. And then, the obtained calcine, after being ground to a fineness of -0.045 mm 65%, was subjected to a magnetic separation with magnetic intensity of 68.8 kA/m, yielding an iron concentrate with 60.65% TFe grade at 94.01% recovery. The subsequent thermodynamic analysis showed that at the temperature within the tested range, both dolomite and phosphogypsum were conducive to the decomposition of iron olivine rather than iron spinel, while sodium sulfate could work for both.