A novel method for desulfurization and purification of fluorite concentrate using acid leaching and reverse flotation of sulfide

Abstract

Fluorite, one of the major raw materials for fluoride in China, is mainly associated with sulfide and calcite minerals. The presence of these sulfide and calcite minerals cause the pipe blockage and efficiency loss during the production of anhydrous hydrofluoric acid (AHF). Worldwide, direct flotation techniques are utilized to beneficiate the fluorite into the chemical grades, but their separation efficiency remained limited due to similar flotability behaviors of fluorite, sulfide and calcite in fatty acid. In the present study, a novel method based on the acid leaching and reverse flotation has been envisaged for the purification and desulfurization of fluorite concentrates containing higher concentrations of sulfur and calcium. Leaching tests were performed by using hydrochloric acid, whereas the reverse flotation experiments were performed by using butyl xanthate as the collector and terpenic oil as the foaming agent. Leaching results showed that, calcite mineral dissolved and the fatty acid lost its collecting and foaming activities under the action of hydrochloric acid. The reverse flotation tests demonstrated that weight percent of sulfides, which are the main causes of blockage in AHF production, was substantially reduced from the fluorite concentrate. Interestingly, this method has been successfully implemented in Shizhuyuan fluorite dressing plant in China for the upgradation of fluorite concentrate. Calcite and sulfur contents of the concentrate were reduced from 4% to 0.01% and 0.5%–0.01%, respectively, and the grade of fluorite concentrate improved from 93.2% to more than 97% with a slight loss of fluorite. Furthermore, the safety in production of AHF was ensured with increased profit from the concentrator.