Investigation into the flotation of malachite, calcite and quartz with three phosphate surfactants

The flotation response of malachite, calcite and quartz to bis (2-ethylhexyl) phosphate (DEHPA), dibutyl phosphate (DBP) and tributyl phosphate (TBP) was evaluated by micro-flotation experiments. The results showed that DEHPA exhibited an impressive flotation selectivity for malachite against calcite/quartz in the pH range of 6.0–9.0 and achieved superior malachite flotation recovery over DBP and TBP. The flotation mechanism of DEHPA to malachite was farther investigated through adsorption, contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The findings inferred that DEHPA reacted with the surface copper atom of malachite via its O atoms of POH and PO to form the hydrophobic surface complexes of Cu(II)-DEHPA. The double active center of the P(O)OH group might be contributed to the stronger affinity of DEHPA and DBP to malachite than that of TBP with the single active center of the PO group. TBP returned the lowest malachite recovery among the three phosphate surfactants, even it has more hydrophobic-carbon atoms than those of DBP.