Aluminium-Modified sodium silicate as a selective depressant in Fluorite-Dolomite Flotation: Experimental and DFT analysis

Metal ions, naturally present in flotation pulp, are commonly employed in flotation reagents, serving as vital reagents in mineral separation processes. This study investigated the impact of ASS, a blend of AlCl 3 , sulfuric acid, and sodium silicate (SS), on the flotation separation efficiency of fluorite from dolomite, as well as the underlying interaction mechanism. Micro flotation tests revealed that ASS significantly decreased the flotation recovery of dolomite while exerting negligible influence on that of fluorite. The difference in flotation recovery rates among the two minerals reached 92.00 % with the addition of 103 mg/L of ASS. The artificial mixed mineral flotation tests were also carried out, the recovery rate and grade of F in the concentrate were 86.47 % and 42.79 %, respectively. The formation of the metal complex ASS, resulting from the combination of Al with Si(OH) 4 , facilitated the adsorption of their hydrolysis products on the surface of dolomite. Within the flotation pulp system, the Ca 2+ and Mg 2+ on the dolomite surface selectively interact with the –OH groups in ASS. At the same time, the Al 3+ in ASS selectively bonds with the O atom of the carbonate group exposed on the dolomite surface. This interaction promotes the adsorption of ASS onto the dolomite surface, thereby hindering the adsorption of sodium oleate. The fluorite surface exhibited weaker interactions with ASS, leading to more sodium oleate adsorbed on the surface of fluorite, thereby increasing the hydrophobicity of the fluorite particles, which floated up. As a result, the selective adsorption of the reagents facilitated the flotation separation of fluorite from dolomite.