The enhanced flotation separation of magnesite and dolomite by introducing chelating reagent EDTA

Abstract

In pulp environment, due to the migration and transformation of dissolved calcium ions, the surface properties of magnesite and dolomite tend to become similar, which in turn leads to difficulties in their flotation separation. In this paper, the chelating reagent EDTA is introduced to eliminate the adverse influence of calcium species and to restore the selectivity of magnesite-dolomite separation using sodium hexametaphosphate (SHMP) as depressant. Flotation experiments demonstrate that, in the presence of ethylenediaminetetraacetic acid (EDTA), the flotation recovery of magnesite increased by 22.14 % compared to using only the depressant SHMP. Zeta potential experiments combined with solution chemistry analysis indicate that the negatively charged hydrolysis species of EDTA can form soluble and stable chelates with positively charged Ca2+ and Ca(OH)+ species, effectively preventing the adsorption and transformation of calcium ions on the magnesite surface. Adsorption measurements directly confirm from a macroscopic perspective that the addition of EDTA reduces the adsorption of the depressant SHMP on the magnesite surface. X-ray photoelectron spectroscopy (XPS) measurements further confirm the phenomenon of calcium ion migration and transformation from the surface of magnesite to dolomite at the microscale, as well as the adsorption mechanisms of EDTA and SHMP on the surfaces of both minerals. Based on the experimental and analytical results, a flotation separation model of the system is established.