New insights into the influence of mineral surface transformation on the flotation behavior of anhydrite/apatite

Abstract

Apatite is generally associated with calcium-containing minerals such as anhydrite, which are difficult to separate due to their similar surface characteristics. In this study, the influence of anhydrite on the flotation behavior of apatite in a fatty acid system was systematically investigated using micro-flotation tests, solution chemical calculations, and surface chemical analyses based on the theory of flotation solution chemistry. The single and mixed mineral flotation experiments revealed that an increasing concentration of anhydrite in the mixed ore system rises, apatite flotation is inhibited while anhydrite flotation is activated. The solution chemical calculation results demonstrated that in the mixed system of anhydrite/apatite, the surface dissolution of anhydrite in the pulp will change the solution chemistry environment, resulting in a drastic decrease in the number of surfaces located ions on the apatite surface and inhibiting its flotation. Furthermore, when the pH of the solution exceeds 4.3, the surface of anhydrite transformed to apatite, promoting anhydrite flotation. The results of the X-ray photoelectron spectroscopy (XPS) analysis further confirmed that the phosphate ions dissolved by apatite were adsorbed on the anhydrite surface at pH= 9, forming calcium phosphate films. Based on the above test results, a novel flotation process was designed to realize the selective flotation of apatite from anhydrite-rich phosphate ores. This study can serve as a theoretical foundation and a practical reference for the separation of calcium-containing minerals.