Improved Flotation Separation of Apatite from Calcite with Benzohydroxamic Acid Collector

Apatite (Ca-10(PO4)(6)F-2) is the most important phosphate mineral, and flotation is the main beneficiation method to separate apatite from its major gangue mineral calcite (CaCO3). Till date, fatty acids and their salts have been widely used as collectors in the apatite/calcite flotation separation due to their low cost and strong collecting ability, but their selectivity is limited. Therefore, screening or designing a selective collector becomes the key to the efficient separation. In this work, an attempt was made to utilize benzohydroxamic acid (BHA) as the collector for the selective separation of apatite from calcite without any depressant. The single and mixed binary mineral flotation experimental results prove the excellent selectivity of BHA in the apatite/calcite flotation separation. Zeta potential measurement results indicate a greater affinity of BHA on the apatite surface than calcite, which is also confirmed by the higher adsorption energy of BHA on the apatite surface based on the first-principle density functional theory calculations. The X-ray photoelectron spectroscopy analysis shows that the selective chemisorption of BHA on apatite over calcite is due to the stronger reactivity and the higher density of Ca2+ ion on the apatite surface than calcite. This work shows that surfactants of hydroxamic acid type can be an ideal collector for phosphate mineral flotation.