Influence of Fine Particles on the Flotation of Sulfide Gold Ore

Objective: To evaluate the influence of fine and ultrafine particles (also called mud) on the flotation of a sulfide gold ore from the Nova Xavantina Mine, located in the state of Mato Grosso, assessing recovery and gold content in the generated concentrate. Theoretical Framework: Gold ore processing presents specific characteristics that differentiate it from other mineral commodities. Sulfide gold ore processing routes may involve, in addition to comminution, concentration steps that exploit differentiating physical and physicochemical properties, such as the difference in specific gravity and hydrophobicity (natural or induced) between the gold-bearing minerals and the gangue minerals. The physical and surface properties of fine particles impose a series of limitations on flotation performance, especially when they coexist with coarse particles. Method: The methodology comprised the collection of samples at the ERO Brasil Nova Xavantina mineral processing plant, carried out by company employees, followed by preparation, chemical characterization (XRF and Fire Assay), granulometric analysis (wet sieving), mineralogical analysis (XRD), and image analysis (SEM/EDS). The ore sample was classified by hydrocycloning to generate three samples with different granulometric distributions, which were subjected to flotation tests in a bench-scale mechanical cell, in rougher and scavenger stages, varying the percentage of solids and pH. Results and Discussion: The sample tested was composed mainly of quartz and pyrite, which explains its high Si and Fe contents. Granulometric analysis indicated a large presence of fine particles (92.53% passing through the 25 µm mesh). Flotation tests indicate that the slime significantly influences the Au content and recovery, thus affecting the selectivity of flotation. The best results were obtained for hydrocyclone overflow samples with 10% solids. Research Implications: The results obtained contribute to the optimization of gold ore processing, typically sulfide ores, assisting in operational decision-making in plants facing problems related to high fines content in the ore, with direct impacts on recovery and Au content. Originality/Value: This work investigated experimentally the effect of slurries on the flotation of sulfide gold ore from a real industrial circuit, providing technical support for improving mineral processing routes and operational practices.