New Insights into the Pre-Concentration of Alunite from a Siliceous ore using Froth Flotation

Alunite is the main non-bauxite source of aluminum. Due to the low Degrees Of Freedom (DOF) of alunite, froth flotation, as a pre-concentration method, is a viable alternative to increase selectivity in downstream processes. The current study was aimed at investigating the pre-concentration of alunite using micro-flotation. In the first step, an optical microscope studies were done to determine DOF of alunite. In the next step, flotation tests were designed. The experiments were performed based on the surface charge differential between alunite and quartz using direct and reverse flotation. In the reverse flotation, Ca⁺² and Ba⁺² were used to activate the quartz surface. Anionic collector was used to float the gangue minerals. The highest grade and recovery using reverse flotation were 34.96 and 81.33%, respectively. In the direct flotation, the surface of alunite was activated using Ba²⁺, Ca²⁺ and F^-. The optimum condition was achieved using F^- as an alunite activator for particles ranged -37+25 µm with the grade of 31.47%. The grade and recovery were 50 and 89%, respectively. All experiments were conducted in Hallimond Tube. During the experiments, several parameters were controlled.