Effect of sodium and calcium ions in salt water on talc fl 2027 Minerals Eng

Talc, a naturally hydrophobic magnesium silicate mineral, often enters flotation concentrates as a gangue mineral, adversely affecting downstream processes. However, the flotation behavior of talc in salt water environments remains less understood. This study investigated the flotation behavior of talc in deionized water, sodium and calcium salt water across varying pH conditions. The flotation results revealed that the recovery of talc in deionized water is pH-independent, which varied in salt water, with a significant decrease in 0.001 mol/L Na+ or Ca2+ salt water at pH 12. The change of talc recovery in different salt water was strongly correlated with its surface wettability. The dissolved Ca2+ and Mg2+ in the inner structure of talc hydrolyzed to form hydrophilic complexes, Ca(OH)+ and Mg(OH)+, and precipitates, Ca(OH)2 and Mg(OH)2, which adsorbed on talc surface and reduced the contact angle. Density functional theory (DFT) calculations demonstrated that cationic complexes, Ca(OH)+ and Mg(OH)+, exhibited stronger adsorption energies with talc (110) surface oxygen atoms, compared to their hydroxide precipitates, Ca(OH)2 and Mg(OH)2, which enhanced talc hydrophilicity at pH 12. These findings provide critical insights into the role of salt water chemistry in talc flotation and offer a theoretical reference for depressing talc in saline flotation systems.