Using phytic acid as a depressant for the selective flotation separation of smithsonite from calcite

• Phytic acid (PA) was used as depressant in the flotation of smithsonite from calcite. • The floatability of calcite was strongly reduced by PA. • The flotation of smithsonite was slightly affected in the presence of PA. • PA reacted with the Ca sites on calcite and showed stronger adsorption than that on smithsonite. • Calcite surface was covered by PA adsorption layer which inhibited the adsorption of NaOL. The flotation separation of smithsonite from calcite is challenging due to their highly similar surface properties. In this study, phytic acid (PA) was applied as a depressant to achieve the flotation separation of smithsonite from calcite for the first time. Micro-flotation experiments indicated that PA showed a strong depressing effect on calcite flotation while a slight effect on smithsonite at pH 9.5. Smithsonite and calcite could be well separated by flotation in the presence of PA and with sodium oleate (NaOL) as collector. Based on a series of tests including zeta potential, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the selective depressing mechanism of PA was well investigated and explained. It was found that the selective depressing performances of PA on smithsonite and calcite flotation were mainly attributed to the selective adsorption of PA based on the different active sites on minerals surfaces. As for calcite, a high adsorption degree of PA caused by strong reaction with the active Ca + sites exposed on calcite surface inhibited the subsequent adsorption of NaOL. On contrast, the much less PA adsorption occurred on smithsonite surface hardly affected the further adsorption of NaOL. The adsorbed aggregates layer covering on PA-treated calcite surface was also visually observed by atomic force microscope. These findings confirm the excellent selective depressing effect of PA on flotation separation of smithsonite and calcite, providing theoretical and practical reference for the clean flotation of smithsonite.