Effect of HEDP on flotation separation of apatite from calcite using sodium oleate as collector

A depressant hydroxy ethylidene diphosphonic acid (HEDP)was introduced as the depressant for the flotation separation of apatite from calcite using sodium oleate (NaOl) as a collector. The microflotation results show that both apatite and barite have good floatability in the presence of NaOl. The addition of HEDP significantly depresses the calcite flotation while it only slightly affects apatite flotation. Mixed minerals flotation results confirm that the efficient flotation separation of apatite from calcite can be achieved using HEDP as a depressant. Zeta potential measurements indicate that HEDP can interact with both apatite and calcite surfaces. HEDP-treated apatite prevents the NaOl adsorption onto the calcite surface rather than the apatite surface. Considering the molecular structure of HEDP and the atomic arrangement of mineral surfaces, the O(P=O)-O (P=O) distance of HEDP only matches well with the Ca-Ca distance on the calcite surface, which may lead to the stable HEDP adsorption onto the calcite surface instead of apatite surface. In addition, the different anionic groups on apatite and calcite surfaces also cause the various electrostatic repulsive forces with HEDP. Thus, the adsorption of HEDP onto the calcite surface is stronger than that onto the apatite surface, then, the selective depression of calcite can be achieved in the apatite flotation. © 2021, Science Press. All right reserved.