Lepidolite, crucial for lithium extraction, is primarily processed through flotation. However, conventional flotation inhibitors pose environmental challenges. This study introduces Fe(III) as a selective and eco-friendly inhibitor in lepidolite flotation. We investigated its impact on flotation performance and interaction mechanisms with feldspar, quartz, and lepidolite. Adsorption studies revealed that dodecylamine (DDA) selectively adsorbs onto lepidolite when Fe(III) is present. Consistent contact angle and flotation results showed reduced hydrophobicity and recovery rates for feldspar and quartz, with minimal impact on lepidolite. Zeta potential measurements indicated lower potentials for feldspar and quartz compared to lepidolite. Notably, the addition of Fe(III) altered the isoelectric points of quartz and feldspar, suggesting stronger Fe(III) adsorption on these minerals. Infrared spectroscopy and X-ray photoelectron spectroscopy confirmed reduced DDA adsorption on feldspar and quartz surfaces due to Fe(III) adsorption, while DDA adsorption on lepidolite remained largely unaffected. The mechanism underlying Fe(III)’s selective inhibition on feldspar and quartz involves their more negative surfaces compared to lepidolite, which facilitates Fe(III) adsorption and inhibits DDA adsorption. This study offers insights into mechanisms relevant to systems using metal ions as depressants, providing valuable references for similar research.

In this study, a lean hematite ore was crushed to produce ultrafine particles using a high pressure grinding roll and then pre-concentrated using a high gradient magnetic separator with a steel rod matrix to reduce the ore tonnage for milling and grinding energy consumption. Pilot test results showed that the primary concentrate grade was increased by 6.98 percentage points from the crude ore with 18.34% Fe at an optimum pre-concentration condition obtained using a matrix with a rod diameter and a rod gap that both measure 4 mm. The concentrate recovery reached a maximum of 86.13% with a tailings yield of 37.61%. Primary concentrates were separated further, and clean concentrates with a grade of 67.15% were obtained. In a magnetic field around a matrix rod, the magnetic capturing force on coarse hematite particles was increased, but such force on fine hematite particles was decreased as the matrix rod diameter increased at the same background magnetic field intensity. Considering gravity and viscous resistance of locked particles, the matrix with large diameter rods (e.g., 4 mm) could effectively and completely recover these particles. By contrast, the matrix with small diameter rods (e.g., 1 mm) could efficiently recover fine particles but not coarse particles such as lean-locked particles.

The selection of grinding media significantly impacts the resulting mineral’s liberation degree and grinding quality; this is particularly impactful for granite pegmatite-type quartz. Accordingly, in this study, we investigate the effects of different grinding media on the breakage characteristics of muscovite granite pegmatite-type quartz, focusing also on quartz mineral flotation. An analysis of scanning electron microscope images reveals distinct fracture characteristics among different minerals. Notably, the fractal dimension of mineral fracture roughness in ball-milled products is larger compared to that of rod-milled products, which exhibit a smaller fractal dimension. This fractal dimension serves as a quantitative measure of the microscopic morphology of mineral fractures in the grinding products, establishing a relationship between the roughness of the fractures and the type of grinding medium used. Further analysis of particle size distribution and mineral dissociation indicates that the rod mill produces a higher yield of coarse fractions compared to both ceramic and steel balls, while the fine fraction yield is significantly lower than that of the rod mill and steel balls. Importantly, the rod mill enhances the dissociation degree of quartz, suggesting that it can improve the liberation of mineral monomers and increase the yield of qualified fractions during the grinding process while effectively reducing the phenomenon of overgrinding. Our flotation experiments demonstrate that the recovery rate of quartz using the rod mill is 2.59% and 5.07% higher than that achieved with the ball mill and ceramic mill, respectively. These findings provide theoretical support for the optimization of grinding media and enhancement of mineral flotation recovery.

In order to improve grinding efficiency and weaken over-grinding in the whole grinding process, the new process of “ultra-crushing in HPGR – classified separation” was proposed with an Anshan style hematite ore. The new process was discussed from the aspects of particle size distribution, liberation characteristics, and separation properties. Compared with the conventional impact crusher, there was no significant difference in coarse particles in HPGR. The “Particle Bed Breakage” characteristics of HPGR products are mainly concentrated in the fine particles (−0.18 mm), which is characterized by higher fines content (a yield of 38.43%), higher specific surface area and higher quartz liberation, etc. It’s worth mentioning that, fine-disseminated iron minerals are detached from the quartz mineral under large compressive-stress in HPGR, which is more conductive to the downstream separation. Magnetic separation tests showed the HPGR (−0.18 mm) tailings have the lowest grade of 7.29%, approximately one percentage point less than coarse grinding products. Based on the above analysis, the new process with a 0.18 mm prescreen size for an Anshan style hematite ore is feasible.

The selection of grinding media significantly impacts the comminution of ores, affecting the resulting liberation degree and quality. This is particularly impactful for granite pegmatite-type quartz. Given how mineral liberation is influenced by various factors, the force exerted by the grinding medium affects the particle size distribution and liberation behavior of minerals. Accordingly, in this study we investigate the effects of different grinding media on the breakage characteristics of muscovite granite pegmatite-type quartz, focusing also on quartz mineral flotation. Analysis of scanning electron microscope images reveals distinct fracture characteristics among different minerals. Notably, the fractal dimension of mineral fracture roughness in ball-milled products is larger compared to that of rod-milled products, which exhibit a smaller fractal dimension. This fractal dimension serves as a quantitative measure of the microscopic morphology of mineral fractures in the grinding products, establishing a relationship between the roughness of the fractures and the type of grinding medium used. Further analysis of particle size distribution and mineral dissociation indicates that the rod mill produces a higher yield of coarse fractions compared to both ceramic and steel balls, while the fine fraction yield is significantly lower than that of the rod mill and steel balls. Importantly, the rod mill enhances the dissociation degree of quartz, suggesting that it can improve the liberation of mineral monomers and increase the yield of qualified fractions during the grinding process, while effectively reducing the phenomenon of overgrinding. Our flotation experiments demonstrate that the recovery rate of quartz using the rod mill is 2.59% and 5.07% higher than that achieved with the ball mill and ceramic mill, respectively. These findings provide theoretical support for the optimization of grinding media and enhancement of mineral flotation recovery.

High-purity quartz (HPQ) is a critical strategic raw material for the semiconductor, optical fiber, and renewable energy industries, yet China still faces a shortage of high-grade domestic resources. To systematically constrain the geological characteristics of pegmatite-type HPQ mineralization in the Qinghe area of the Altai orogen, this study adopts a comprehensive research approach integrating petrography, in situ trace-element analysis of quartz, process-mineralogical assessment, beneficiation and purification tests, monazite U–Pb geochronology, and Electrical Resistivity Tomography (ERT) detection. Monazite yields a weighted mean U-Pb age of 370.4 ± 2.7 Ma, indicating emplacement of the mineralized pegmatite in the Late Devonian. Three samples produced purified quartz sand with SiO₂ contents of 99.9951%–99.9975% (4N5 to nearly 4N8). The quartz grains are characterized by sparse inclusions, and low concentrations of critical impurity elements (Al, Ti, Li), satisfying the quality evaluation criteria for high-grade HPQ feedstock. This reconnaissance case study reveals that high-quality quartz occurs mainly in transition and marginal zones of the pegmatite veins as colorless to smoky, saccharoidal or roe-like crystalline aggregates. Minor garnet occurs as an accessory phase within mineralized pegmatites, which is regarded as a preliminary local prospecting indicator for the Qinghe area. ERT geophysical results reveal that the pegmatite ore body extends at depth but is locally truncated by late-stage tectonic structures. Combined with microscopic textures of quartz (i.e., undulose extinction, subgrain formation, and dynamic recrystallization) and regional geological comparisons, we propose that regional ductile shearing and dynamometamorphic overprinting may improve quartz quality in pegmatite. Nevertheless, this metallogenic interpretation requires future verification via extensive beneficiation–purification tests, and wider applicability of the above-mentioned prospecting features needs further sampling from additional pegmatite veins in the Chinese Altai.