Synergistic effect and co-adsorption mechanism of a mixed collector on the flotation separation of spodumene from feldspar

Abstract

In this study, the flotation separation of spodumene from feldspar was achieved using mixed collector of sodium oleate (NaOL)/cetyl trimethylammonium bromide (CTAB). Micro-flotation experiments show that the selective flotation separation of the two minerals could not be achieved in the presence of single collector under the pH range of 2–12, but the they could be effectively separated using mixed collector at the NaOL-to-CTAB molar ratio (MR) of 7:1 at pH 6.0 Artificial mixed minerals tests prove the effective flotation separation effect of the mixed NaOL/CTAB at pH 6.0. Analyses of bubble collision-attachment show that when using mixed NaOL/CTAB as the collector, the bubble could quickly form a three-phase contact (TPC) line on spodumene surface (tTPC=396 ms), but the bubble did not form TPC line on feldspar surface (tTPC＞2000 ms), suggesting a much stronger hydrophobic surface of spodumene. Adsorption amount tests show the much higher adsorption density of mixed NaOL/CTAB on spodumene surface than feldspar, moreover, CTAB promoted the NaOL adsorption on spodumene surface, but it hindered the NaOL adsorption on feldspar surface. The surface and thermodynamic parameters (CMC, γcmc, ∆Gm0, Γmax, Amin) obtained from surface analyses demonstrate higher surface activity and denser molecular arrangement in mixed NaOL/CTAB system than that in the individual system, indicating a positive synergistic effect of mixed collector. Pyrene fluorescence spectrum analyses present the lower critical micelle concentration (CMC) value and polarity of the mixed NaOL/CTAB than their individual components, suggesting that the mixture had much stronger hydrophobicity and was more likely to form micelles than single collector. All the tests were conducted at temperature of 25 ℃.