Selective adsorption of sodium polyacrylate on calcite surface: Implications for flotation separation of apatite from calcite

In this study, the selectively depression effect of sodium polyacrylate (PAAS) on the flotation separation of apatite from calcite was studied. The floatability of apatite and calcite in the absence and presence of depressant PAAS using sodium oleate (NaOL) as collector was investigated by microflotation experiments. The selectively depression mechanism of PAAS was revealed by wettability analysis of the mineral surfaces and X-ray photoelectron spectroscopy (XPS) analysis. The adsorption morphology and adsorption height of the depressant PAAS on calcite surface were observed using atomic force microscope (AFM). The microflotation tests indicated that the floatability of both apatite and calcite was excellent using 1.0 x 10(-4) mol/L NaOL without depressant PAAS. The depressant PAAS had a stronger depression effect on calcite than that of apatite and can achieve flotation separation of the two minerals. Wettability analysis indicated that depressant PAAS can more significantly reduce the contact angle of calcite than that of apatite in the presence of collector NaOL. XPS analysis indicated that the depressant PAAS adsorbed more strongly on the surface of calcite than that of apatite. The depressant PAAS was mainly chemically adsorbed on the surface of calcite by the bonding of the carboxyl group of PAAS and the calcium atom of the calcite surface. AFM observed that PAAS exhibited uniform, dense, point-like adsorption on the surface of calcite with an adsorption height of 4-5 nm.