Selective flotation of magnesite from calcite using a novel chelating collector MES D30: Insights from DFT calculations and molecular dynamics simulations

MES D30 is a green chelating collector that achieves selective separation of magnesite from calcite. • With only a small amount of sodium silicate, a maximum recovery difference of 76.42% was achieved under optimal conditions. • MES D30 exhibits stable chelating adsorption on magnesite, with a 6.7-fold higher binding energy shift for Mg 2+ than for Ca 2+ . • DFT and MD simulations reveal that stable chelate rings form with Mg 2+ on magnesite, while the hydration layer on calcite hinders effective coordination. Selecting the appropriate collector is key to achieving efficient separation of magnesite and calcite. In this study, MES D30 was used as a green chelating collector, and with a small amount of the inhibitor sodium silicate (SS), efficient flotation separation of the two minerals was achieved. Under optimal conditions of 140 mg/L MES D30, 7 mg/L SS, pH 11.0, and 2000 rpm, the difference in recovery between the two minerals reached 76.42%. Contact angle and zeta potential tests indicate that MES D30 significantly increases the hydrophobicity of the magnesite surface and shifts its potential to the negative, while having a negligible effect on calcite; SEM-EDS analysis shows that 3.4% of the characteristic S element was detected on the magnesite surface, compared to only 0.6% on calcite. FTIR confirmed the interaction of MES D30 with magnesite, while XPS revealed that the binding energy shift of Mg 2+ (1.88 eV) is approximately 6.71 times that of Ca 2+ (0.28 eV), indicating a much stronger chemical interaction and the formation of a stable adsorption on magnesite. DFT and MD simulations further revealed that the active sites of MES D30 form a stable chelate structure with Mg 2+ on the magnesite surface, resulting in a higher binding energy; in contrast, the hydration film on the calcite surface hinders the agent's action, leading to a lower binding energy.