Mo-Bi bulk concentrate is usually processed with a longer flowsheet at higher cost, and the traditional bismuth smelting processing technique also features longer flow, high energy consumption, as well as lower bismuth recovery. In order to solve those problems, an oxygen-rich hydrochloric acid leaching process was adopted in an experimental study on beneficiation of Mo-Bi bulk concentrate, and the effects of HCl concentration, leaching time and temperature on the leaching rates of Mo and Bi were investigated. It is shown that oxygen-rich hydrochloric acid leaching at 80 ℃ for 6.0 h, with HCl concentration of 3 mol/L, liquid/solid ratio of 3 ∶ 1, and stirring speed of 500 r/min, can result in the Bi leaching rate up to 99.13% and Mo left in the leaching residue. Thus, molybdenum and bismuth can be efficiently separated. The obtained leaching solution is then subjected to purification for purity removal and replacement with iron plate, and the finally obtained sponge bismuth can have purity exceeding 99%.

After iron tailings was subjected to preconcentration followed by magnetizing roasting process, the obtained product was taken in an experiment to be processed respectively by adopting a grinding and magnetic separation process and a combined process of grinding plus magnetic separation followed by flotation process. The roasted ore with TFe grade of 33.19% was processed using a grinding and magnetic separation approach, resulting in an iron concentrate grading 63.04% TFe at 80.04% recovery at a grinding fineness of -0.025 mm 97%. Although the processing flowsheet is simple, it is still hard to achieve such a grinding fineness in commercial practice and the grinding cost is also extremely high. However, a process consisting of grinding, magnetic separation and flotation, with a grinding fineness of -0.025 mm 85%, can produce an iron concentrate grading 65.36% TFe at 73.39% recovery. Therewith, such grinding fineness is commercially practicable and the grinding cost can be obviously reduced.

Flotation tests were conducted for a low-grade copper-nickel sulfide ore with high content of mud and magnesium oxide from Xinjiang. Using sodium carboxymethyl cellulose and sodium silicate as a combined inhibitor, butyl xanthoxanthate and butyl ammonium black as a combined collector, a closed-circuit test with a flowsheet consisting of a Cu-Ni bulk flotation and a Cu/Ni separation produced a copper concentrate grading 25.11% Cu at 79.90% recovery, with MgO content of 2.02%, as well as a nickel concentrate grading 6.98% Ni at 75.01% recovery, with MgO content of 5.32%. It is concluded that effective recovery and separation of copper and nickel can be actualized.

A typical metal mine with a smelter in Hunan Province was taken as an example, and 22 key factors affecting the environmental risk diffusion path of heavy metal pollution area were chosen based on data crawling and on-site case investigation, as well as systematical sorting. Nemerow integrated pollution index (NIPI) of soil was calculated using Nemerow pollution index method, and then was used to aid the identification of key factors. Results show that atmospheric deposition and soil permeability are selected as the environmental risk diffusion path for heavy metal pollution of soil based on the analytic hierarchy process, and the key factors for environmental risk diffusion include distance from pollution source, PM₁₀ content in air, hard cover on ground surface, anti-seepage measures, soil pH value and soil organic matter (SOM) content. It is found that the NIPI of the soil is positively correlated to soil pH value, SOM, PM₁₀, but negatively correlated to the distance from pollution source, hard cover on soil surface and anti-seepage measures. The correlation coefficient fits well with the factor weight (R²=0.63).

To investigate the current situation of heavy metal pollution in a stone coal mine in Hunan Province, the content of Cd, Hg, As, Pb, Cr, Cr (Ⅵ), Zn, Fe, and Mn in water and soil samples was determined by using ICP, and the risk of heavy metal pollution was evaluated by using the Nemerow pollution index and potential ecological hazard index respectively. The results show that concentrations of Cd, Cr (Ⅵ), Zn, Fe and Mn in water are 1.935 5, 0.025 3, 6.024 9, 16.222 0 and 4.214 9 mg/L on average, with pollution indices of 387.10, 5.06, 3.01, 54.07 and 42.15, presenting the pollution degree in the following descending order: Cd>Fe>Mn>Cr (Ⅵ)>Zn; while content of Pb、Zn、Cr、As、Hg and Cd in the soil is 8.51, 38.59, 18.65, 10.01, 0.18 and 3.41 mg/kg on average, with ecological risk coefficient of 2.13, 0.98, 0.85, 18.00, 28.55 and 339.80 on average, presenting pollution degree in the following descending order: Cd>Hg>As>Pb>Zn>Cr. It is shown that the comprehensive potential ecological risk indices of the whole mine is 390.31, indicating a higher ecological pollution risk. The mine area is polluted by several kinds of heavy metals, especially in the downstream areas of waste dump and sedimentation tank.

Experimental studies were carried out for iron recovery from the leaching residue of lateritic nickel ore containing 51.38% TFe and 2.01% S, by adopting processing techniques of centrifugal separation, magnetic separation and magnetic roasting. It is found that the process of magnetic roasting followed by magnetic separation is an efficient technique to recover iron from such leaching slag. It is shown that the process of coal-based reduction followed by low-intensity magnetic separation (LIMS) can produce the concentrate grading 62.77% TFe at 94.04% recovery, and the process of gas-based reduction followed by LIMS leads to the concentrate grading 68.77% TFe at 95.15% recovery, with sulfur content of 0.12% in the impurity, which can meet the quality standard for iron concentrate. Although the process of direct reduction followed by LIMS can produce the concentrate grading 90.89% TFe at 88.90% recovery, it is shown that there is higher content of sulfur in the concentrate.

Fe-Cr-B based wear-resistant coating was prepared on the surface of 45 steel by ultra-high-speed laser cladding. The effects of laser power, scanning speed and powder feeding speed on the aspect ratio and crack of single pass cladding layer were studied by orthogonal experimental method, and the effects of overlap rates on the surface quality of cladded layer was also studied. The optimal process parameters were determined as follows: laser power of 2 300 W, scanning speed of 250 mm/s, powder feeding speed of 24 g/min, and overlap rate of 70%. The results show that the hardness of the coating is between 754HV_0.2 and 831HV_0.2, which is 2.36 times to 2.60 times of the matrix hardness. Under the same conditions, the volume wear of the coating is only 3.64% of electroplated hard chromium coating.

An all-weather moving target detection method by using Retinex algorithm based on HSV color space conversion was proposed for complex situation in a mine, which changed the detection of moving target to the detection of special marker on the moving target, and extracted the original grey image of the target by color space conversion. The histogram of grey distribution was used to judge whether to restore the low-illumination image. And special markers were selected in the scene, and the original image was converted to HSV color space. Then, the corresponding ROI region was selected, and the binary image was obtained based on the threshold value. After smoothing of the data, the Canny operator was used to extract contour information, thus characteristic parameters of the marker was extracted. The practice proves that the characteristic parameters of the markers can be accurately obtained by this method, which can thus solve the problem of connector falling off from mechanical equipment under complex situation. It is shown that this method is of certain practical significance in engineering application.

In view of interference of the existence of selenium in determination of gold and silver in crude selenium sample, the sample with an addition of concentrated sulfuric acid was firstly heated to remove selenium. Then, sodium chloride solution was added to precipitate silver therein, and the obtained residue after filtration was taken for gold and silver determination using fire assay by gravimetry. Thus, a process of heating with sulfuric acid to remove selenium followed by fire assay gravimetry was established for continuous determination of gold and silver in crude selenium, and the effects of residual selenium, sulfuric acid dosage and heating time on the determination results were also discussed. Furthermore, such continuous determination process was also compared to the industrial standard method in terms of the analysis of gold and silver in crude selenium. By using the proposed continuous method, the relative standard deviations (RSD₇) of gold was within a range of 0.54%-1.30%, and the RSD₇ of silver was within a range of 0.28%-0.39%. The spike recovery of gold was 94.6%-101.3%, and the spike recovery of silver was 96.3%-100.1%. It is shown that the analysis results are consistent with those by industrial standard method. It is concluded that the proposed determination method, being fast and accurate, is suitable for determination of gold and silver in crude selenium.

Hollow microsphere BiOBr photocatalyst was synthesized using hydrothermal method. BiOBr photocatalyst doped with different content of Fe were prepared by regulating Fe³⁺/Bi³⁺molar ratio. The crystal structure, morphology, optical and electrochemical properties of Fe-doped BiOBr photocatalyst were characterized respectively. With organic dye Congo red (CR) as the pollutant, its photocatalysis was evaluated by testing the degradation effect of the photocatalyst on the pollutant under visible light irradiation. The results showed that the photocatalytic material with 7% Fe doping exhibited the optimal photocatalytic performance. The degradation efficiency of CR within 180 min of irradiation with 5 W light-emitting diode (LED) was 89.66%, which was much higher than that of undoped BiOBr (62.82%). It is found that the enhanced photocatalytic performance of Fe-doped BiOBr is attributed to the enhanced light absorption and the efficient transfer and separation of photogenerated carriers.