Utilization of a novel bisphosphonic acid surfactant for reverse froth flotation of magnesite and dolomite

Abstract

Magnesite and dolomite are magnesium-containing minerals with similar crystal structures, making their separation a challenge in production. In this study, the surfactant Dodecane-1,2-diyl bis (dihydrogen phosphate) (DBDP) was discovered to selectively adsorb on dolomite surface and collect dolomite from magnesite. In the single mineral flotation tests, the collector DBDP achieved a recovery difference of more than 45% under neutral condition. In the mixed minerals reverse flotation tests with sodium alginate as an inhibitor, an excellent separation result of increasing MgO grade from 44.30% to 46.13% with a magnesite recovery of 88.19% in the concentrate was obtained. Adsorption mechanism analysis confirmed that DBDP was chemically adsorbed to the Ca and Mg sites on mineral surfaces and was stronger on the surface of dolomite. The DFT calculation further established the O atoms at top of the posphonic acid group acted on the mineral surface by chemisorption, while the O atoms in C-O-P sometimes assisted by electrostatic interaction. Meanwhile, DBDP provided more active O sites on the dolomite surface, resulting in more stable adsorption than magnesite. As a result, DBDP promised an excellent performance in the novel process of removing dolomite from magnesite by reverse flotation.