Al3+ enhanced the depressant of guar gum on the flotation separation of smithsonite from calcite

• Al 3+ combined with GG can achieve the flotation separation of smithsonite from calcite. • Al 3+ enhanced the selectivity of GG on calcite. • The hydrolysates of Al 3+ in the solution system were selectively adsorbed on the surface of calcite. • GG was selectively adsorbed on the surface of calcite by Ca-O and Al-O bond. Naturally, there are similar surface physicochemical and floatability properties between smithsonite and calcite, and their flotation separation has always been challenging. This research studied the function and mechanism of Al 3+ and guar gum (GG) on the flotation separation of calcite from smithsonite through micro-flotation, chemical calculation of solution, adsorption measurement, FT-IR analysis, Zeta potential measurement and XPS analysis. The result of micro-flotation showed that Al 3+ and guar gum as depressant could separate smithsonite from calcite effectively. Results of chemical calculation of solution, adsorption measurement, FT-IR analysis, Zeta potential and XPS analysis measurement indicated that the adsorption difference of Al 3+ and GG on smithsonite and calcite surface was obvious. The hydrolyzate of Al 3+ selectively adsorbed on calcite and provided the Al adsorption sites for GG. GG selectively adsorbed on the calcite surface through Ca-O bond and Al-O bond, which was formed by the O in the phosphate and hydroxyl groups with Ca and Al sites on the calcite surface. Al(OH) 3 and Al 2 O 3 produced by Al 3+ in the solution system were also selectively adsorbed on the calcite surface, and hinder the adsorption of NaOL, finally achieving the flotation separation of smithsonite from calcite.