The application and mechanism of high-efficiency depressant Na2ATP on the selective separation of cassiterite from fluorite by direct flotation

Abstract

To achieve the efficient flotation separation of cassiterite from fluorite, an eco-friendly depressant, the disodium salt of adenosine 5′-triphosphate (Na2ATP), was employed for the selective depression of fluorite. The performance of Na2ATP as a depressant in the flotation of cassiterite and fluorite was evaluated by micro-flotation experiments in a sodium oleate (NaOL) system. The flotation tests revealed that Na2ATP significantly depressed the flotation of fluorite compared to that of cassiterite, and excellent separation was achieved using 1.0 mM Na2ATP and 0.14 mM NaOL at pH 8.02. Moreover, the mechanism of the selective depression Na2ATP on the two minerals was revealed by surface analyses, revealing that chemisorption between the phosphate group of Na2ATP and the calcium ions on the fluorite surface was responsible for the selective adsorption of Na2ATP on fluorite, and the significant pre-adsorption of Na2ATP onto the fluorite surface impeded the further adsorption of NaOL. However, because Na2ATP was adsorbed on cassiterite by physisorption, which is relatively weak, the strong chemisorption of NaOL on cassiterite occurred regardless of pre-treatment with Na2ATP. Furthermore, density functional theory calculations revealed that the adsorption mode of Na2ATP to be “horizontal” and to occur at multiple calcium-ion sites on the fluorite surface. In summary, Na2ATP is a suitable high-efficiency depressant for the separation of cassiterite from fluorite by direct flotation.