Flotation of rutile from almandine using sodium fluorosilicate as the depressant

Abstract There is little scientific agreement on the way sodium fluorosilicate (SF) depresses gangue minerals, resulting in a stagnation into in-depth research. Here, we describe a new explanation hoping to advance this step of development. In this study, flotation of rutile from almandine was investigated using SF as the depressant and Styryl phosphonic acid (SPA) as the collector. The study was performed through the measurements of zeta potential, contact angle, and X-ray photoelectron spectroscopy (XPS), in addition to the micro-flotation of single minerals and artificially mixed minerals. The experimental results demonstrated that SF acting in the form of SiF62- at pH 5-6 was a highly selective depressant on almandine, rather than on rutile, leading to a high selectivity for the flotation of rutile. The XPS results revealed a strong interaction between F and active Fe sites on almandine surface, reducing adsorption sites for collector, thereby strongly depressing the flotation of almandine.