The effect of jojoba oil on the surface properties of calcite and apatite aiming at their selective flotation

Abstract

The beneficiation of phosphate ores by froth flotation is the most efficient process used to separate apatite from calcium minerals. However, the similarity of surface properties between apatite and calcite generally leads to non-selective adsorption of reagents, rendering the selective separation of these minerals a problem, demanding a specific approach. The sedimentary phosphate deposit of Itataia, Brazil, studied in this paper, presents a complex mineralogical composition. The bulk flotation of apatite and calcite with anionic collectors in an alkaline medium followed by selective flotation of calcite at pH5.5 using phosphoric acid or citric acid as depressant has been suggested for this ore. In the present work, contact angle measurements were performed to evaluate the behavior of jojoba oil as an alternative collector for the selective separation of apatite and calcite minerals. Jojoba oil is composed mainly of gondoic, erucic and oleic acids. The hydrophobicity studies were undertaken using a computer controlled contact angle goniometer. Additionally, the collector adsorption was evaluated through electrophoretic mobility and FTIR measurements. The results indicated that a high selectivity between calcite and apatite can be obtained by using jojoba oil as a collector at slightly acid medium, without the use of depressants. The most interesting results were achieved with a jojoba oil concentration of 200mg·L−1 at pH6.5, where the apatite was fully hydrophilic while calcite showed high hydrophobicity.