The pre-concentration and tailings discarding technique was adopted in the processing of vanadium-titanium magnetite in Panxi region. Based on analysis and summarization, it is found that the ores in the Baima Mine belongs to low TiO₂-grade vanadium-titanium magnetite, and pre-concentration and tailings discarding process can be adopted. As for pre-concentration, medium-intensity magnetic separator (MIMS) is suitable for discarding larger lumps (-300 mm), a process of roughing with MIMS combined with scavenging with MIMS is suitable for discarding small lumps (-40 mm), and wet high-intensity magnetic separator is suitable for discarding coarser-grained ore (-12 mm or-5 mm). As a result, the TiO₂ grade of final discarded tailings can be finally controlled within 2.5%. However, the vanadium-titanium magnetite in Panzhihua, Hongge and Taihe mines have a high grade of titanium, for which it is appropriate to adopt the above-mentioned processes for pre-concentration and discarding of small lump (-25 mm) ores and coarser-grained ores. And after classification of the tailings, the finer fraction is sent for titanium separation, leading to the TiO₂ grade of the final discarded tailings within 3.5%. It is shown that the above-mentioned processing technique and flowchart can greatly discard qualified tailings, which can provide a reference for development and utilization of similar resources.

After lead-zinc separation in a lead-zinc concentrator, the sulfur concentrate produced from the sulfur flotation process is rich in gold and silver. To further improve the pricing coefficient of gold and silver in the sulfur concentrate, mineral processing research was carried out on the pressure-filtered sample of the sulfur concentrate. Mechanical reagent removal by grinding was adopted to eliminate the adverse effect of residual collector on flotation and improve the liberation between gold and silver minerals and sulfur minerals. In combination of a sulfur depressant consisting of sodium sulfide and sodium humate and 25^# aerofloat collector, effective separation and mutual enrichment of gold and silver minerals and sulfur minerals were actualized, and an independent high gold and silver concentrate product was also produced with an Au grade of more than 15 g/t and an Ag grade of more than 200 g/t. Meanwhile, a part of lead and zinc lost in the sulfur concentrate was recovered synchronously, with the total grade of Pb and Zn exceeding 7%. This processing technique not only optimizes the product structure and improves the value realization rate of metallic minerals, but also brings good economic benefits, which is of reference significance.

Aiming at a low-grade sandy kaolin with complex occurrence state in Hunan, a process consisting of pulping, cyclone classification, grinding for desliming and reverse flotation was developed. A closed-circuit test produced a kaolin concentrate grading 28.64% Al₂O₃ with a comprehensive yield of 49.74%, as well as a quartz concentrate grading 93.61% SiO₂ with a yield of 32.24%. It is concluded that minerals such as kaolinite and quartz can be effectively separated, thus comprehensive utilization of resources can be actualized.

The grain growth kinetics of the conversion from fersmite to pyrochlore during high-temperature sintering process was investigated. The results show that the conversion rate of fersmite increases with rising sintering temperature, and the pyrochlore content reaches 96.07% at 760 ℃. At the temperature within the range of 760-880 ℃, the average grain size of pyrochlore increases with the extension of holding time at the same sintering temperature and also increases with the rising of sintering temperature at the same holding time. The grain growth exponents within this temperature range are all greater than 3, presenting a three-dimensional grain growth characteristic. The apparent activation energy of grain growth decreases with rising temperature, making it easier for grain to grow. At the same sintering temperature, the apparent activation energy of grains increases with the extension of holding time, indicating that it is more difficult for grains to grow after the holding time is prolonged. It is concluded that grain growth can be reliably promoted by appropriately increasing the sintering temperature or adding modifiers rather than by merely extending holding time.

To address the technical bottlenecks of both high consumption of materials and energy and low recovery efficiency in traditional pyrometallurgical recycling of high-value copper-bearing solid wastes such as waste printed circuit boards, the slag phase regulation mechanism in cooperative smelting of multi-source copper-bearing solid waste was investigated. An analysis of the quaternary phase diagram of CaO-SiO₂-Al₂O₃-FeO system reveals that when the mass ratio of FeO to SiO₂ ranges from 1/9 to 1/1 and mass fraction of CaO is within the range of 10%-40%, the primary crystal phase regions of molten slag are primarily distributed in the areas of clinopyroxene, wollastonite and spinel, and a theoretical melting point is lower than 1 300 ℃. A prediction model for physicochemical properties of slag demonstrates that the fluidity of the molten slag can be significantly improved by increasing FeO/SiO₂ ratio from 0.5 to 1.0, and the optimal fluidity is achieved with FeO and SiO₂ at a mass ratio of 1.0, which can meet the requirements of industrial smelting. An experiment was performed with the optimized conditions, including FeO and SiO₂ at a mass ratio of 0.8, CaO and SiO₂ at a mass ratio of 0.4, smelting at a constant-temperature of 1 350 ℃ for 1 h, resulting in the obtained slag with the residual copper content therein reduced to 0.18% and copper recovery up to 99.39%. The produced crude copper alloy mainly contained Cu, C, S, Pb, Fe, Sn and other elements. It is concluded that increasing the FeO/SiO₂ ratio can contribute to improving metal recovery, but it can also increase separation difficulty in the subsequent electrolytic refining process.

With ammonia leaching residue from a molybdenum ore in Henan as raw material, a high-temperature oxidative alkali leaching process was adopted to recover molybdenum therein. With Na₂CO₃+NaOH+H₂O₂ as a composite leaching agent at the dosage of 200 L/t, 160 kg/t and 200 kg/t respectively, ammonia leaching residue was leached at 70 ℃, with the solid-to-liquid ratio of 1∶5 and agitation speed of 60 r/min, leading to the leaching rate of molybdenum up to 93.75% and the molybdenum content in the obtained alkali leaching residue reduced to 0.46%. Mechanism analysis reveals that in the composite leaching agent, H₂O₂ can oxidize low-valent molybdenum (MoO_x, where 2≤x<3) and MoS₂ into soluble MoO₄^2-, and Na₂CO₃ can displace molybdenum from insoluble molybdates, while NaOH can maintain a high pH of the solution to inhibit the precipitation of molybdic acid. This composite leaching system can efficiently recover refractory molybdenum from ammonia leaching residue, and also significantly shorten the ammonia leaching process. The approach provides an economically feasible technical route for the utilization of low-grade molybdenum resources.

A chemical phase analysis method for nickel in laterite nickel ore was proposed. Calcium carbonate solution was used to leach nickel from nickel sulfate. Acetic acid-sodium sulfite solution was applied to extract nickel from nickel oxide hosted in manganese minerals, and hydrogen peroxide-ammonium acetate solution was adopted to leach nickel from nickel sulfide. Both the nickel content in each phase and the total nickel content were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The results show that the relative deviation between the sum of nickel contents in each phase and the total nickel content is less than 1%. In addition, the nickel content in each phase is basically consistent with the test results obtained by automatic mineral analyzer. It is verified that this method is accurate and reliable, and can be applied to the nickel phase analysis of laterite nickel ore.

Anode sheets of spent lithium-ion batteries were taken for research, and an L₂₅ (5⁴) orthogonal test was employed to investigate the effects of ultrasonic temperature, ultrasonic time, ultrasonic frequency and solid-liquid ratio on the separation efficiency of graphite and copper foil in a system with an addition of 0.5% surfactant. A system without surfactant was taken as the control group. The results show that the graphite separation efficiency reaches 95.75% in a system with an addition of 0.5% surfactant, by ultrasonic separation at 90 ℃ for 15 min with a frequency of 100 kHz and solid-liquid ratio of 1∶9. The recovered graphite is basically consistent with those of standard graphite in terms of the XRD diffraction peaks and has a low proportion of disordered structure. The recovered copper foil exhibits favorable mechanical properties, with a tensile strength of 180-190 MPa, and its carrier mobility is 35.68 cm²/ (V·s), indicating excellent electrical conductivity.

Based on the databases of China National Knowledge Infrastructure (CNKI) and Web of Science, statistical analysis was conducted on journal papers regarding ammonia nitrogen treatment in weathered crust elution-deposited rare earth tailings from November 2009 to November 2024. CiteSpace was employed to perform visual analysis of the temporal distribution, authors, collaboration networks, research hotspots and research frontiers in this field. The research progress was systematically summarized in the form of knowledge maps, so as to provide research directions and theoretical support for soil ecological restoration and residual ammonia nitrogen pollution control in closed mining areas of weathered crust elution-deposited rare earth ores. The results show that the number of relevant publications exhibited an overall upward trend during the 15-year period. Most high-yield authors were from universities, with research dominated by team collaboration, and the vast majority of authors and institutions were from China. Although different studies had varied focuses, they all centered on ammonia nitrogen treatment and ecological governance of weathered crust elution-deposited rare earth tailings. Soil pollution prevention and ecological restoration have become research frontiers. Future research should strike a balance among treatment efficiency, remediation cost and green sustainable development.

With electrolytic manganese anode slime as raw material and high-purity manganese sulfate as the precursor, manganese tetroxide (Mn₃O₄) particles were prepared via a two-step oxidation method. The response surface methodology was adopted to optimize the processing parameters. On this basis, the effects of surfactants on the particle size, specific surface area and micromorphology of Mn₃O₄ were systematically investigated. The results show that under the optimal conditions including manganese and ammonia in a molar ratio of 1∶2, reaction temperature of 65 ℃ and reaction time of 40 min, the manganese content of the synthesized Mn₃O₄ reaches 71.1%. Surfactants exert negligible impacts on the phase composition and manganese content of Mn₃O₄, but obvious effects on its microscopic surface morphology, specific surface area and particle size. The Mn₃O₄ synthesized by adding polyvinylpyrrolidone presents a quasi-spherical morphology with uniform particles and narrow size distribution. With a particle size of 32.65 nm and a specific surface area of 18.49 m²/g, the synthesized product satisfies the quality standard of high-purity Mn₃O₄ in terms of manganese content.