In order to address the problem of slope stability for a valley dumpsite in one mountain area, numerical simulation was conducted with FLAC^3D for the stability of slope under three working conditions, including natural state, rainstorm case and earthquake occurrence. The stability and reliability of the dump under conditions of rainstorm plus seismic was evaluated with introduced Monte Carlo algorithm. Results show that the overall and part of dumpsite slope, under all three working conditions of natural state, rainstorm and earthquake, can be in a stable state, and the overall safety factors present a normal distribution and are mainly within the range of 2.0-2.1, consistent with the numerical simulation results (2.08); under conditions of rainstorm plus seismic, the probability for the overall dumpsite to be unstable is 0, while some parts of dumpsite have a 35.99% probability to be unstable. It is shown that the numerical simulation value and on-site monitoring result present a deviation from 9.8% to 15.4% based on the comparison.

An experiment study was carried out on a processing technique of reduction leaching of pyrolusite with acidic wastewater from steel mills as the reductant, for comprehensive utilization of pyrolusite and acidic wastewater of steel mills. The results show that 3 hours of leaching at 90 ℃, with FeCl₂ and MnO₂ in a mass ratio of 2.2, liquid-solid ratio of 11∶1 and the acid wastewater at an initial concentration of 2.5 mol/L, can result in the leaching rates of Mn, Fe and Al from the pyrolusite at 97.14%, 95.37% and 41.33%, respectively. And then, Fe³⁺ in the leachate is reduced with scrap iron at an amount of 1.1 times the theoretical amount at a temperature of 80 ℃ for 50 min, leading to the reduction rate of Fe³⁺ up to 99.85%. After Fe³⁺ is reduced to Fe²⁺, the Fe²⁺-containing reducing solution is returned for leaching again, presenting stable leaching results. It is shown that the average leaching rates of Mn, Fe and Al from pyrolusite are 96.75%, 95.31% and 41.18%, respectively.

The stability of goafs in a mine was analyzed. Firstly, the current situation of the goafs was investigated in detail to clarify the distribution and volume of goafs. Secondly, the stability variation of goafs before and after backfill was evaluated based on the FLAC^3D simulation results. It is found that there are five main goafs in the mine, which are distributed in the middle section of 700-860 m, with total volume of around 404 500 m³. Currently, the roof of goaf is unstable, posing a greater potential risk of collapse. The rock mass that is not connected together from 1^# to 4^# goaf has concentrated force on it and a plastic zone penetrates through, possibly causing large-scale instability. After the goafs in the middle section of 700-820 m are gradually backfilled, the risk of goaf instability can be gradually eliminated, and production activities in the middle section below 700 m won't be affected. It is recommended that 1^#-4^# goafs should be preferably backfilled to reduce the risk of roof collapse and penetration.

Thermodynamic analysis was conducted with HSC Chemistry 9.0 software for removing arsenic by sulfuration from waste acidic solution left after copper electrolysis, and it is found that H₂S could effectively make asenous acid and arsenate in the high-concentrated sulfuric acid system precipitated by sulfuration. Based on the theoretical analysis results, an experiment on arsenic removal of waste acidic solution by sulfuration was carried out to investigate the effects of sulfurizing agent dosage and reaction time on the arsenic precipitation effect by sufuration. Results show that by 30 min-sulfuration with an addition of H₂S at 0.87 times the theoretical amount, the arsenic content in waste acidic solution after precipitation process falls down to 10.68 mg/L from 6 777.52 mg/L, and the removal rates of arsenic, copper and antimony are 99.84%, 99.76% and 99.33%, respectively. The iron and nickel therein are hardly precipitated, and the mass fraction of arsenic and sulfur in the residue of the arsenic removal process are 43.21% and 44.68%, among which the arsenic in the form of arsenic sulfide is in a mass fraction of 42.33%, and S/As in the arsenic sulfide is in a ratio of 2.29. The finally obtained product is a mixture of As₂S₃ and As₂S₅. It is shown that the thermodynamic analysis results differ slightly from the experimental results, but are still of guiding reference for experiments and practice.

The acid leaching solution of cathode materials from spent lithium iron phosphate batteries was taken as raw material, and iron, phosphorus and lithium elements therein were recovered by adopting an oxidation-precipitation process. The effects of factors, including endpoint pH value of reaction system, reaction temperature, concentration of sodium hydroxide, dripping rate of sodium hydroxide, and the volume ratio of hydrogen peroxide to acid leaching solution, on the precipitation rates of iron and phosphorus and the loss of lithium during the precipitation process were all investigated. Results show that with the endpoint pH value of 2.5, temperature of 75 ℃, sodium hydroxide with concentration of 1.5 mol/L, sodium hydroxide solution at a dripping rate of 7.7 mL/min, and hydrogen peroxide and acid leaching solution in a volume ratio of 1∶60, the average precipitation rates of iron and phosphorus are 99.86% and 98.23%, respectively, and the average loss of lithium is just 1.23%. Under the above-mentioned conditions, iron and phosphorus in the solution can be effectively removed and recycled in the form of iron phosphate, presenting a lower loss rate of lithium. After 5 h-heat treatment at 700 ℃, it is shown that the chemical composition of iron phosphate can meet the industrial standard.

According to the mineral properties of a kind of flake graphite ore in Heilongjiang Province, a new efficient flotation reagent was developed and then adopted in a flotation experiment. Results show that with the new reagent of CYM-11 as a collector, CYQ-01 as a foaming agent, an experiment with a closed-circuit flowsheet consisting of eight-stage regrinding and nine-stage cleaning can yield an graphite concentrate with fixed carbon content of 96.63% at 95.69% recovery, among which the graphite concentrate at a size of +0.15 mm can be produced with a yield of 11.38% and fixed carbon content of 96.04% in mass fraction. It is shown that the large flake graphite can be well protected during the course of mineral processing.

A FeCoCrNiMn high-entropy alloy (HEA) coating was prepared on the 201 stainless steel surface by adopting high-speed laser cladding technology, and then the microstructure, phase distribution, microhardness of FeCoCrNiMn coating, as well as its wear properties in dry sliding condition were all investigated. It is found that such laser cladded FeCoCrNiMn HEA coating consists of a single FCC structure, with no obvious cracks observed. It also forms a good metallurgical bond with the substrate. The microhardness of the coating is around (439±2.1) HV, nearly two times that of 201 stainless steel substrate, and the strengthening mechanisms mainly include strengthening by grain refinement and solid solution strengthening. Also, the FeCoCrNiMn coating presents an obviously better wear resistance than 201 stainless steel, with an average friction factor of 0.246 and a specific wear rate of about 2.59×10^-6 mm³/(N·m). The wear mechanisms for it include adhesive and abrasive wear. It is concluded that such FeCoCrNiMn HEA coating prepared by high-speed laser cladding technology can significantly improve the surface hardness, wear resistance and service life of machine components.

In order to effectively predict blast-induced rock fragmentation, a distribution of normalized rock fragmentation under different conditions was obtained by performing a designed experiment on drilling and blasting of a concrete specimen, and then the rock fragmentation exceeding 40 mm was selected for study. The correlation among variables under different testing conditions was analyzed by using Spearman correlation statistics, and the initial weights and thresholds of the BP neural network were optimized by using the ant colony optimization (ACO) to construct an ACO-BP model. The model was then trained with rock fragmentation by on-site blasting, and tested. Based on the comparison of such prediction mode with BP neural network model, random forest (RF) model and extreme gradient boosting (XGboost) model, it is found that the ACO-BP model is highly reliable in predicting blast-induced rock fragmentation, presenting a root mean square error of 0.13, an average absolute error of 0.11, and a coefficient of determination of 0.92. It is concluded that this model, with higher accuracy in prediction and applicability, can accurately predict blast-induced rock fragmentation.

Surface mechanical attrition treatment (SMAT) was adopted for low-carbon steel materials to achieve surface nanonization, and then the influence of surface nanonization on corrosion resistance of low-carbon steel was also discussed. The results show that due to surface nanonization, the low-carbon steel has a greater plastic deformation on the surface as the carbon content decreases, and the X-ray diffraction of its surface presents obviously wider peaks. It is found that after nanosizing treatment for the surface of low-carbon steel with different carbon content, the lower the carbon content, the rougher the surface and the worse the corrosion resistance.

To explore feasibility of replacing steel ball with porcelain ball in the second-stage grinding of a magnetite ore from Anhui, the feed ore to the second-stage grinding process in the magnetite ore processing plant was taken for study, and single-factor tests were conducted for gradation of porcelain ball in diameter, grinding concentration and filling rate of grinding media. On this basis, researches on grinding kinetics and commercial application were also conducted. The results show that porcelain ball can substitute steel ball as the medium in the second-stage grinding, which can bring in optimized particle size distribution of the milled product. For the feed in a particle size greater than 0.092 mm, the grinding rate of porcelain ball milling is greater than that of steel ball milling；while with the feed in a particle size less than 0.092 mm, the grinding rate of porcelain ball milling is less than that of steel ball milling. The best conditions for porcelain ball milling are finally determined as follows: porcelain balls with diameter of 30 mm, 25 mm and 20 mm in a mass ratio of 1∶3∶1, grinding concentration of 74% and grinding media with filling rate of 40%. The industrial applications with porcelain ball in mill shows the particle size distribution of overflow products can be effectively improved, both unit power consumption and ball consumption reduced by 51.89% and 50%, respectively.