Selective depression of calcite by sodium phytate in the flotation separation of smithsonite from calcite under an Al-BHA-NaOL collector system

An efficient flotation separation strategy for smithsonite and calcite was established using a ternary collector (ABN) and sodium phytate (SP) at weakly alkaline pH. • Optimized SP-ABN system yields a mixed-ore Zn grade of 36.39% with 62.75% recovery. • XPS, AFM and Zeta potential analyses confirm that SP selectively shields calcite via strong Ca-chelation. • SP forms a dense layer on calcite, effectively blocking the adsorption of the ABN collector via steric hindrance and electrostatic repulsion. This study systematically investigated the selective depression behavior of sodium phytate (SP) in the flotation separation of smithsonite from calcite using an Al-BHA-NaOL collector system (ABN). Although ABN (2.5 × 10 -5 mol/L) exhibited moderate selectivity toward smithsonite under weakly alkaline conditions, calcite remained relatively floatable, resulting in limited separation efficiency. The addition of SP effectively depressed calcite flotation while only slightly influencing smithsonite, thereby significantly improving the separation performance. Under the optimal conditions of pH 8.0 and SP dosage of 21.65 × 10 -6 mol/L, artificial mixed mineral flotation tests produced a concentrate with a Zn grade of 36.39% and Zn recovery of 62.75%. To elucidate the selective depression mechanism, zeta potential measurements, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analysis were performed. The results demonstrated preferentially interacted with calcite rather than with smithsonite, resulting in greater changes in surface charge, surface morphology, and hydrophobicity. XPS analysis revealed a significant shift in the Ca 2p 3/2 peak on calcite after SP treatment, whereas the Zn 2p 3/2 peak of smithsonite exhibited only a negligible change, indicating a much stronger interaction between SP and calcite. SP significantly hindered ABN adsorption on calcite, while its influence on collector adsorption on smithsonite remained limited. These findings indicate that SP as an environmentally friendly selective depressant for calcite provides new insights into the selective regulation of carbonate mineral surfaces, offering a promising strategy for the flotation beneficiation of carbonate-associated zinc oxide ores. Download: Download high-res image (236KB) Download: Download full-size image