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

To achieve the efficient flotation separation of cassiterite from fluorite, an eco-friendly depressant, the disodium salt of adenosine 5′-triphosphate (Na 2 ATP), was employed for the selective depression of fluorite. The performance of Na 2 ATP 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 Na 2 ATP significantly depressed the flotation of fluorite compared to that of cassiterite, and excellent separation was achieved using 1.0 mM Na 2 ATP and 0.14 mM NaOL at pH 8.02. Moreover, the mechanism of the selective depression Na 2 ATP on the two minerals was revealed by surface analyses, revealing that chemisorption between the phosphate group of Na 2 ATP and the calcium ions on the fluorite surface was responsible for the selective adsorption of Na 2 ATP on fluorite, and the significant pre-adsorption of Na 2 ATP onto the fluorite surface impeded the further adsorption of NaOL. However, because Na 2 ATP was adsorbed on cassiterite by physisorption, which is relatively weak, the strong chemisorption of NaOL on cassiterite occurred regardless of pre-treatment with Na 2 ATP. Furthermore, density functional theory calculations revealed that the adsorption mode of Na 2 ATP to be “horizontal” and to occur at multiple calcium-ion sites on the fluorite surface. In summary, Na 2 ATP is a suitable high-efficiency depressant for the separation of cassiterite from fluorite by direct flotation.