Flotation separation of smithsonite from calcite using depressant sodium alginate and mixed cationic/anionic collectors

Due to the influence factors such as pulp ions and surface conversion, efficient flotation separation of smithsonite from calcite remains a challenge in the actual system. In this paper, the effect of an effective inhibitor sodium alginate (NaAl) on flotation separation of smithsonite from calcite using a mixed cationic/anionic collector of octadecylamine acetate (ODA) and sodium amyl xanthate (SAX) was studied. Flotation results indicate that NaAl is perfectly effective for the separation. The results of adsorption amount measurements show that collector can both adsorb on smithsonite and calcite surfaces by the co-adsorption of ODA-SAX complex even in the presence of NaAl. The strong adsorption of macromolecular NaAl increases the surface hydrophilicity of calcite and may cover the micromolecular collector. The results of zeta potential and spectroscopy (FTIR) analysis confirm that NaAl adsorbs on calcite surface by chemisorption, hydrogen bonding and electrostatic interaction while weakly adsorbs on smithsonite surface by hydrogen bonding and electrostatic interaction. Na2S increases the selectivity of NaAl due to the lower reactivity of Zn on the sulphidized smithsonite surface than that of Ca on the commonly exposed calcite surface.