Extracting iron while minimizing the health and environmental risks associated with arsenic contamination necessitates the removal of arsenic from arsenic-bearing iron ores to ensure a safe and sustainable supply of this metal for industries. The beneficiation of iron minerals and arsenic-bearing minerals from arsenic-bearing iron ores with a calcification-magnetizing roasting and low-intensity magnetic separation (CMR-LMS) process is investigated in this work. The results show that the process is successful in extracting iron minerals and eliminating arsenic-containing minerals. The roasting involves two key steps: calcification and magnetizing, which change hematite and goethite into magnetite and arsenic-bearing minerals into calcium arsenates. The process’s separation efficiency of the CMR-LMS is closely linked to the parameters such as roasting temperature, roasting time, coke, alkalinity, and the liberation of gangue minerals from iron minerals. Through grinding and secondary magnetic separation, the iron minerals and gangue components, as well as arsenic, in roasted sand can be further separated. The optimum procedure results in a high-grade iron concentrate with an iron assay of 65.65%, an Fe recovery rate of 80.07%, and an arsenic content of 0.085%, while achieving a 93.29% As removal rate from the original ore that has 45.32% Fe and 0.70% As.

Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate (OHA) were used as the collectors through micro-flotation, focused beam reflectance measurement (FBRM) and a particle video microscope (PVM), zeta potential, and the extended DLVO theory. Micro-flotation tests confirmed that LN activated the flotation of cassiterite using the hydroxamic acids as collectors. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to capture in situ data on the changes in size distribution and morphology of cassiterite aggregates during stirring. The FBRM and PVM image results indicated that the addition of LN could promote the formation of hydrophobic aggregates of fine cassiterite, when BHA or HHA was used as the collector, and reduce the dosage of OHA needed to induce the formation of hydrophobic aggregates of cassiterite. The extended DLVO theory interaction energies indicated that the presence of LN could decrease the electrostatic interaction energies (V_edl) and increase the hydrophobic interaction energies (V_hy) between cassiterite particles, resulting in the disappearance of the high energy barriers that existed between the particles in the absence of LN. Thus, cassiterite particles could aggregate in the presence of LN when BHA, HHA, or a low concentration of OHA was used as the collector.

Extensive laboratory and commercial test works have been carried out on wet belt high gradient permanent magnetic separation (WBHGMS) and these works demonstrated that it is effective in purification of non-metallic ores such as quartz and feldspar. The WBHGMS process is achieved with a thin plate-type magnet and its length produces a decisive role in the separation performance. In this investigation, the separation dynamics of particles in the inclined slurry in a high gradient magnetic field and the relationship between magnet length and separation performance were analyzed, and a pilot-scale WBHGMS separator was used to purify a quartz ore to confirm the analysis. The separation results indicate that the magnet length has definitely a dominant control on the separation performance of the separator and its performance is connected with the variables such as magnet inclination angle, belt rotation speed and feed particle size. The iron removal rate was increased with decrease in the Fe₂O₃ grade of non-magnetic product, as the magnet length is increased. Under the optimized operating conditions, the pilot-scale separator produced a non-magnetic product assaying 0.065% Fe₂O₃ at a mass weight of non-magnetic product of 75.51% and an iron removal rate of 75.46% from the quartz ore assaying 0.20% Fe₂O₃. This investigation has provided a detailed description on the optimum design for magnet length in a given WBHGMS separator and it is favorable for the performance improvement of the separator.

The complex mineral composition and heterogeneous intergrowth characteristics of copper–tin polymetallic sulfide ores make it difficult to obtain an appropriate particle-size distribution and sufficient mineral liberation during grinding, which can affect subsequent separation. This study investigated the effects of sodium tripolyphosphate (STPP) as a grinding aid on a copper–tin polymetallic sulfide ore from the Datun Plant in Gejiu, Yunnan, China. Grinding and separation tests, together with mineralogical and surface characterization using MapsMin, SEM-EDS, zeta-potential and contact-angle measurements, and DLVO/EDLVO calculations, were conducted to evaluate the effects of STPP on grinding and subsequent separation. The grinding results showed that, compared with the lime-only condition (0.10 wt% lime), the addition of 0.025 wt% STPP increased the proportion of the target size fraction (−0.15 + 0.019 mm) by 1.76%, without a marked increase in the fine fraction (−0.019 mm) or the coarse fraction (+0.15 mm). Compared with the lime-only condition, the addition of 0.025 wt% STPP increased the grade and recovery of the copper flotation concentrate by 0.20% and 3.54%, respectively, and those of the cassiterite gravity concentrate by 0.44% and 14.31%, respectively. The overall Sn recovery of the combined gravity separation and flotation process increased from 92.58% under the lime-only condition to 93.56% with the addition of 0.025 wt% STPP, but decreased to 92.39% when the STPP dosage was increased to 0.050 wt%. Automated mineralogical analysis showed that STPP addition increased the complete liberation degrees of cassiterite and bornite, while varying degrees of improvement were also observed for other major minerals. With the addition of 0.025 wt% STPP, the maximum particle size decreased from 820.95 to 495.30 μm, and D90 decreased from 374 to 237 μm relative to the lime-only condition. Surface characterization and DLVO/EDLVO analysis indicated that STPP altered mineral surface properties and interparticle interactions, which may have contributed to the observed changes in particle-size distribution and mineral liberation.

A comprehensive and systematic study was conducted to address a series of key technical challenges encountered in the grinding process at a copper mine. These issues included the complex mechanical properties of the feed ore, which led to low grinding efficiency, difficulty in achieving the required grinding fineness for flotation, uneven particle size distribution in the grinding products, and severe occurrences of overgrinding and undergrinding. Based on the semi-theoretical ball diameter formula, the optimal initial ball size distribution for the ball mill was precisely calculated as Φ70:Φ50:Φ40:Φ30 = 15:25:35:25. Through laboratory-scale grinding tests and Discrete Element Method (DEM) simulations, a systematic analysis of multiple indicators under three different ball loading schemes was performed, including the motion state of particles inside the mill, the collision behavior of the grinding media, and the energy distribution. This analysis confirmed the rationality and effectiveness of the literature scheme. Industrial trial results showed the following: the yield of the +0.20 mm fraction decreased by 4.15 percentage points, and the yield of the −0.010 mm fraction and its proportion relative to the −0.074 mm fraction decreased by 10.17 and 19.10 percentage points, respectively. Conversely, the yields of the intermediate separated fraction (−0.20 + 0.010 mm), the easily separated fraction (−0.074 + 0.018 mm) and the −0.074 mm qualified fraction increased by 14.32, 14.13, and 7.29 percentage points, respectively. The grinding technical efficiency improved by 19.55 percentage points. Furthermore, the specific steel ball consumption decreased by 46 g/t, a reduction of 5.07%. The copper concentrate recovery increased by 0.65 percentage points, resulting in an annual increase of 40.51 tons of copper metal, additional revenue of CNY 3.2483 million, and steel ball cost savings of CNY 603,500. Collectively, this optimization generated a total economic benefit of CNY 3.8518 million. By optimizing the ball size distribution, the particle size composition of the grinding products was significantly improved, the flotation indicators were enhanced, and the grinding media consumption cost was reduced, achieving quality improvement and efficiency increase in the mineral processing. This study provides a valuable reference for solving similar grinding problems.

Grinding accounts for a relatively high proportion of the total electrical energy consumption in a mineral processing plant, and research on mill operating power constitutes a key basis for realizing intelligent control and energy conservation of the grinding process. Based on the SAB (semi-autogenous grinding followed by ball mill) circuit of a mineral processing plant, this study developed three sets of explicit mathematical models for ball mill power prediction using multivariate adaptive regression splines (MARS): an initial version containing 105 terms, an advanced version with 21 terms, and a reduced version with 11 terms. The prediction results show that the reduced version, using only 11 terms, attains a coefficient of determination R² = 0.7989 (MAE = 8.96 kW, MAPE = 0.41%), comparable to the accuracy of the initial version (R² = 0.8166). Moreover, the reduced model can be directly embedded into a PLC or an Excel spreadsheet to achieve mill power prediction at the millisecond scale. The proposed explicit model enables real-time prediction of ball mill operating power, allowing the plant to adjust mill operation promptly and reduce operating costs; it also holds important significance for the intelligent control of the grinding process.