Effect of platy gangue minerals in sulfide flotation: Part I-transport rates

Abstract

Observations from operating flotation plants suggest that the presence of the platy gangue mineral mica leads to significantly reduced concentrate grades. The combined effects of gangue particle shape (platy vs globular) and particle size on flotation has not been systematically investigated. Flotation tests were conducted on ground ore mixed with different amounts of sized mica (platy) or silica (globular) minerals. This essentially allowed us to alter the already present non-sulfide gangue (NSG) composition in a controlled manner and to investigate gangue size and shape effects on flotation recovery. The use of purposefully added mineral particles with narrow size distributions improved our ability to determine the different pathways by which hydrophilic particles of various sizes and shapes are transported through the froth. Cumulative mineral and water recovery data for each composition was used to calculate the degree of NSG entrainment for each ore plus adulterant (mica or silica). Analysis of the degree of entrainment vs adulterant particle size and shape showed that the addition of mica typically results in higher gangue recovery compared to when silica is added at comparable concentrations. The data for recovery when mica was added followed a trend associated with typical entrainment behavior, i.e., there was a decrease in the degree of entrainment with increasing mica particle size up to about 100μ. However, for greater mica size fractions, an increase in the degree of entrainment was observed. The reason for this behavior is discussed in the part II companion to this paper (Bhambhani, T., Farinato, R., Somasundaran, P., Nagaraj, D., 2022. Effect of play gangue minerals in sulfide flotation: Part 2: Mechanisms, Submitted to Minerals Engineering). The entrainment effects of mica were also evidenced to be concentration dependent. For coarser fractions of mica added to the ore pulp, where the degree of entrainment now increases with mica size, an increase in concentration of mica in that pulp resulted in a steeper increase in the degree of entrainment with mica particle size. This suggested second-order effects arising from particle-particle interactions. Similar results were seen with silica; however, deviations in the degree of entrainment vs particle size plots were less pronounced or required greater concentrations to be seen.