Depression of the selective separation of rutile from almandine by sodium Hexametaphosphate

Sodium Hexametaphosphate (SHMP) is widely used as an inorganic depressant of carbonate minerals. But little information if any exists on the proper mechanism of how SHMP depresses silicate minerals. In the study, flotation separation of rutile and its main gangue mineral almandine using a Sodium Hexametaphosphate is investigated. The study was conducted through micro flotation tests of single and artificially mixed minerals. Adsorption mechanism was analyzed through Zeta potential and X-ray photoelectron spectroscopy (XPS) analyses respectively. The flotation tests for single and artificially mixed minerals show that SHMP is an efficient depressant in the separation of rutile ores from almandine as a possible gangue mineral. Zeta potential measurements and XPS analysis indicate that more SHMP was adsorbed on almandine surface as opposed to that of rutile. Fe ions on the surface of almandine were the main active sites for collector adsorption, while the P in (NaPO3)6 is central to the depression process. The adsorption mechanism of sodium Hexametaphosphate on almandine surface was mainly attributed to the electrostatic interaction and chemical bonding. While on the other hand, SHMP seems to have negligible effect on rutile surface.