The synergistic interaction between dithiophosphate collectors and frothers at the air-water and sulphide mineral interface

Dialkyl dithiophosphates (DTP) are commonly used as primary or secondary collectors in base metal sulfide and platinum group mineral flotation. However, evidence in the literature suggests that, under basic conditions, DTP does not adsorb onto certain minerals. The purpose of this study was to investigate the interactions between DTP or xanthate collectors and frothers at the solid-liquid and air-liquid interfaces. Microflotation and contact time tests showed that DTP synergistically improved recoveries and attachment probabilities of galena and pyrite in the presence of frother. These improvements were not seen for any of the single reagents or, most importantly, for mixtures of a xanthate collector and frother. By measuring the residual collector concentration in solution, it was shown that no DTP adsorbed onto the galena surface and only minimal amounts onto the pyrite surface, either in the presence or absence of frother. In contrast, all of the xanthate collector adsorbed onto both pyrite and galena. Investigations at the air-water interface included surface tension and bubble size measurements. These showed that DTP, unlike xanthate, was weakly active at the air-water interface, but did not show evidence of synergistic interaction with frother. It was concluded that DTP can have an alternative mechanism of flotation enhancement to conventional collectors by adsorbing at the air-liquid interface and not the solid-liquid interface. Various theories of the detailed mechanism are discussed in the paper.