Enhancing malachite flotation: Interface hydration structure and regulation mechanism by bis(2-ethylhexyl)phosphate

As one of the main copper oxide minerals, the strong surface hydrophilicity induces the low recovery of malachite and decreases the utilization efficiency of copper metal. In this work, the interface hydration structure of malachite and regulation mechanism by bis(2-ethylhexyl)phosphate (D2EHPA) were revealed via density functional theory (DFT) calculations, molecular dynamics (MD) simulations, X-ray photoelectron spectroscopy (XPS) analysis, contact angle and Zeta potential measurements. Flotation tests and contact angle measurements showed that D2EHPA exhibited excellent concentration selectivity for malachite against muscovite and quartz, enhanced the malachite recovery to 90.65 % with the dosage of 50 mg/L at pH 7.0, and the contact angle of malachite increased from 23.0° to 111°. Zeta potential analysis confirmed the selective adsorption of D2EHPA on malachite surface, electrostatic attraction occurred between D2EHPA and malachite surface when pH < 8.0. XPS analysis and DFT calculations further confirmed the adsorption of D2EHPA on malachite surface. Moreover, the adsorption of D2EHPA mainly via the chemical bonding between O1 (P=O), O2 (P-OH) and the Cu on malachite surface. MD simulations revealed that the average D2EHPA molecule interaction energy with malachite (−2 0 1) surface was −36.522 kJ/mol, increased the interaction energy of H 2 O on malachite (−2 0 1) surface from −1.293 kJ/mol to −0.824 kJ/mol, decreased the number density of H 2 O molecule towards malachite (−2 0 1) surface from 0.18 Å -3 to 0.12 Å -3 , induced hydrophobicity of malachite surface.