Selective flotation of calcite and dolomite from apatite using bio-based alternatives to conventional collectors: Castor and mustard oils

Calcium minerals are the main constituents of most sedimentary phosphate ores. These include apatite, calcite, and dolomite. Owing to the similar surface properties of these minerals, their selective flotation is notably intricate. Fatty acids are the mostly employed collectors in calcium minerals flotation. The performance of fatty acids and their selectivity towards minerals depends on their hydrocarbon chain's length, unsaturation number and type, as well as their comprised polar and nonpolar functional groups, amongst others. In the present work, ricinoleic (RA) and erucic acid (EA)'s collecting ability and affinity towards apatite, calcite, and dolomite were investigated. These fatty acids were biobased; extracted from castor and mustard oils respectively. Their performance was monitored alongside two different conventional collectors for an effective evaluation. The castor and mustard oils were characterized and saponified. The critical micellar concentration of the yielded soaps and the commercial collectors was determined, and their chemistry was analyzed. In the framework of fundamental studies, the four collectors were made in contact with pure fluorapatite, calcite, and dolomite. Zeta potential, surface chemistry, and wettability assessments confirmed the adsorption of the fatty acids on the mineral surfaces. The biobased collectors' adsorption at the surface of the three minerals was important yet less selective than the conventional ones. Flotation tests conducted on a sedimentary phosphate ore have affirmed the applicability of the castor oil derived collector in calcite and dolomite flotation (in the presence of phosphoric acid as an apatite depressant). The castor oil collector was able to selectively recover excellent carbonate concentrates, while surpassing the performance of the tested conventional collectors.