The factors and reasons influencing lime activity are presented, and the influencing mechanism of lime activity for digestion performance of bauxite is also expounded. It is found that the particle size of limestone and calcination temperature are two important factors influencing activity of lime. At a calcination temperature of 1 000 ℃, the activity of lime is as high as 33.5 mL, while with the particle size of limestone increased to 17.5-22.5 mm, the activity of lime increases to 46 mL. The analysis results of scanning electron microscopy show that highly active lime has fine particles with uniform particle size and in a structure of honeycomb with well-developed and interconnected pores. The experiment of bauxite digestion shows that the activity of lime and its adding amount will bring influence to the digestion rate of bauxite and the phase composition of red mud. By adding highly active lime with a C/S ratio of 1.0, the relative digestion rate of bauxite is as high as 98.12%.

An experimental study was carried out on fluoride removal from the wastewater after acid leaching process in one enterprise. In the experiment, zirconia was used in the 1^st-stage reaction and amorphous aluminum hydroxide was adopted in the 2^nd-stage reaction for fluoride removal, and effects of reaction temperature, reaction time and adding amount of zirconia-based reagent on the fluoride removal effect were explored. It is found that both higher temperature and longer reaction time can promote fluoride reduction effect of fluoride removing reagent.1^st-stage reaction ran for 50 min at 75 ℃ with an addition of 50 g/L zirconia-based reagent, the fluoride reduction rate was up to 96% and fluoride mass concentration in the wastewater was reduced from 600 mg/L to 25 mg/L. After that, 2^nd-stage reaction at 70 ℃ ran for 60 min, by adding 5 g/L amorphous aluminum hydroxide, the fluoride mass concentration in the wastewater was down from 25 mg/L to 6.5 mg/L. It is shown that the residue left after fluoride removal process has a good crystal structure and obvious diffraction peak. XRD analysis shows that Na₃AlF₆ is the main component in the residue.

Red mud was pre-treated with process of reduction roasting followed by magnetic separation, and the obtained non-magnetic material was calcined and then dissolved in hydrochloric acid. After that, it was filtered after addition of saturated sodium meta-aluminate polymerizing agent, and then matured to prepare polymeric aluminum chloride (PAC) base liquid, which was used in a purification test. With PAC-base liquid and manganese-containing wastewater in a volume ratio of 1∶120, stirring speed of 140 r/min, pH of 8, reaction temperature of 30 ℃, and addition of polyacrylamide (PAM) at an amount of 20 mg/L, the manganese mass concentration in the wastewater reduced from 325.3 mg/L to 1.5 mg/L after 5 hours of settlement, showing manganese removal rate up to 99.5%. It is shown that the manganese mass concentration in the purified liquid can meet class Ⅰ limit in the national discharge standard.

Based on comparison of cadmium immobilization with 4 types of minerals originated from 14 places in Hunan Province, four kinds of natural and efficient remediation materials (including limestone from Yujiaao of Ningxiang County, low-grade manganese ore from Nanmuchong of Xiangtan County, bentonite from Mazongling of Taoyuan County, and sepiolite from Xingang of Shimen County) were selected. The kinetic rate of cadmium immobilization by these four natural minerals is in the following descending order: bentonite > limestone > sepiolite > manganese ore. The cadmium adsorption by four kinds of minerals increases as the initial cadmium mass concentration increases. With cadmium mass concentration no higher than 10.0 mg/L, the cadmium adsorption by these four minerals is in the following descending order: limestone > bentonite > manganese ore > sepiolite; with cadmium mass concentration exceeding 10.0 mg/L, the cadmium adsorption by these four minerals is in the following descending order: bentonite > limestone > manganese ore > sepiolite. The adsorption behavior follows Langmuir adsorption model, and the maximum adsorption capacities of bentonite, limestone, manganese ore and sepiolite are 29.38 mg/g, 14.51 mg/g, 9.67 mg/g and 5.27 mg/g respectively. With pH of solution within the range of 6 to 9, the removal efficiency of cadmium by four minerals is in the following descending order: limestone > bentonite > manganese ore > sepiolite. It is concluded that the cadmium immobilization with natural minerals is related to chemical composition of minerals, initial cadmium mass concentration, and pH value.

A kind of low-impurity lead electrolyte was prepared with lead ingots, fluorosilicic acid, hydrogen peroxide, bone glue, and β-naphthol as raw materials, and then was used in an experimental research on 14 consecutive cycles of electrolysis to produce refined lead. It is shown that the initial power consumption of lead electrolysis was 52.37 kW·h/t, and 6N high-purity lead was produced in the first two cycles; as the cyclic electrolysis process proceeded, the impurity content and lead ion content in the electrolyte gradually increased, while the mass concentration of fluorosilicic acid gradually decreased, resulting in an increase in the impurity content of precipitated lead. Therefore, the content of Cu, Ag, Fe, Al and other impurities in the precipitated lead all gradually increased after two cycles of electrolysis, and the precipitated lead met the standard for 5N but did not meet the standard for 6N high-purity lead. Furthermore, the power consumption also gradually increased, but remained at a low level of 50 kW·h/t to 70 kW·h/t for each cycle.

An experimental study was carried out for adsorption of ammonia nitride and copper ions in electroplating wastewater by fly ash-based zeolite. Results show that the proper conditions for adsorption of copper ions by fly ash-based zeolite include pH of 8, initial mass concentration of 200 mg/L for copper ions in the solution, adsorption time of 0.45 h, and temperature of 200 ℃; the proper conditions for adsorption of ammonia nitride by fly ash-based zeolite include addition of 8 g/L fly ash-based zeolite, pH of 8, adsorption time of 0.60 h, and initial mass concentration of 150 mg/L for ammonia nitride in the solution. It is found that the adsorption of copper ions by fly ash-based zeolites is a physical adsorption process, and the adsorption of ammonia nitride by fly ash-based zeolites is a combination of ion exchange and physical adsorption.

Aiming at potential emergency discharge required during at-sea testing of deep-sea polymetallic nodules lifting system consisting of pipeline and lifting pump, a theoretical calculation was conducted for the hydraulic system of emergency discharge mechanism for at-sea testing, and also a simulation analysis was conducted with AMEsim. It is found that the reliability coefficient of AMEsim for the system is 0.86. An AMEsim-based hydraulic system model was established for the actuator in an at-sea test at 500 m depth. The simulation results show that the oil pipeline in the hydraulic system is 16 mm in diameter, with the set pressure not less than 10.47 MPa, and the action time of actuator is 6 s. This research results can provide a reference for the design of emergency discharge mechanism.

A free fall backfill (FFB) system with high-concentration slurry in a mine was taken as an example to study pipeline parameters and resistance characteristics of FFB system by conducting theoretical analysis, laboratory test and verification with field measurement. The results show that the FFB system has many working procedures, with flowrate for normal backfilling fluctuating within the range of 100-240 m³/h, and the pressure at 1.2-2.2 MPa. The flowrate at specific points of the pipeline presents a quasi-normal distribution, averaging 190 m³/h. There are two characteristic peaks for the pressure, being 1.86 MPa and 3.04 MPa, respectively. The parameters at a single point of pipeline cannot be used to analyze and judge the working conditions, such as pipe blockage and leakage. The pressure difference and flowrate difference between sections of the pipeline present obvious normal distribution, with mathematical statistics expectations of 4.62 m³/h and 0.64 MPa, respectively. The difference in instantaneous flowrate and pressure can be used to judge blockage and leakage of the pipeline. The flow resistance in the laminar-turbulent transition zone predicted by the Swamee-Aggarwal formula is 2.08 MPa/km, which is consistent with the measured value of 2.15 MPa/km.

With a tailings pond in Lesser Khingan Mountains region as an example, experiments were carried out on tailings embankment respectively by upstream construction with discharged wet metallic tailings, by filling a pond with metallic tailings, and by construction with overflow and underflow of tailings separately from cyclone. It is shown that the embankment construction with overflow and underflow separately from cyclone is superior over other two methods based on comparison. It can not only effectively improve consolidation of the tailings in front of the embankment through drainage, prolong the length of dry beach and increase the strength of the tailings in front of the embankment, but also create a wide sloping sediment, keep the embankment within the freeboard, improve the seepage condition of the dam body, as well as increase the bearing capacity of beach surface and the efficiency of embankment construction. By improving the cycloning process, a scheme including constructing embankment during non-winter seasons and discharging tailings in winter to build a wide sub-dam is proposed, which can solve the previously existing problems to a certain extent, such as sediment beach with high water content and low bearing capacity, as well as inability to build sub-dam with tailings sand. However, both the utilizing rate of coarse sand, the width of sub-dam of high-grade tailings pond and development of frozen soil still need to improve. Finally, it is found that the embankment construction by adopting technique of building wider sub-dam with underflow and overflow of tailings from cyclone combined with geofariform method can effectively resolve the existing problems for tailings dam. Thus, this technique can be promoted as an effective embankment construction scheme with fine-grained tailings in regions with high altitude and cold weather.

The numerical simulation was used to establish a single-hole blasting model, which was then used to simulate the blasting effect with different stemming length. Otsu thresholding technique was adopted for image segmentation, and the data, such as percentage of cracked rock area, fractal dimension of pore structure, and fragmentation of rock mass, were extracted for comparative analysis, so as to explore the influence of stemming length on damage effect under deep-hole blasting. The results show that fractal dimension and percentage of cracked rock area are in an uptrend before falling down as stemming length increases. The fractal dimension reaches the maximum value with stemming length of 3.0 m, and the percentage of cracked rock area reaches the maximum value with stemming length of 1.7 m. Stemming length of 2.2 m can bring the highest number of fragments, and stemming length of 2.0 m can result in the smallest average area of fragments. It is found that the blasting with the stemming length of 2.0-2.2 m can lead to better rock fragmentation effect. As the stemming length increases, the flyrock becomes bigger, and the displacement distance decreases. The research results can be taken as reference in selection of stemming parameters for blasting operation.