Selective adsorption mechanism of a new combined collector on the surfaces of quartz and potassium feldspar

This study presents a novel methodology for the separation of quartz and feldspar under neutral and weakly alkaline conditions. Ethyl-bis(dodecyl dimethyl ammonium bromide) (Gemini) is introduced as a new collector in the flotation process, combined with sodium oleate (NaOL) to enhance separation efficiency. The investigation focuses on the adsorption mechanism of these combined collectors on mineral surfaces. While the individual collectors, Gemini and NaOL, were ineffective in differentiating between quartz and feldspar, their combination resulted in significantly improved separation outcomes. Flotation tests indicated that at a pulp pH of 7, with Gemini and NaOL at concentrations of 12 × 10-5 mol l-1 and molar ratios of 1:1 and 1:2, the flotation recovery of quartz was 46.51% and 40.57% higher than that of potassium feldspar, respectively. Zeta potential measurements, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy analyses, and molecular dynamics simulations demonstrate that the Gemini collector predominantly influences the flotation performance of quartz and feldspar. NaOL molecules do not directly adsorb onto the quartz surface; instead, they co-adsorb via electrostatic interactions with Gemini, which minimally affects the interaction dynamics. In contrast, NaOL preferentially adsorbs onto the aluminum, silicon, and other reactive sites on the feldspar surface through its -COO functional group, leading to competitive adsorption with Gemini and consequently diminishing Gemini's effectiveness on feldspar. This study elucidates the selective separation mechanism of quartz and feldspar using Gemini and NaOL and aims to provide insights into employing combined collectors in diverse separation scenarios to enhance quartz quality.