Selective depression of feldspar by carboxymethyl starch sodium in the flotation of quartz using polyether amine

The selective flotation of quartz and feldspar under weakly alkaline conditions was investigated, with carboxymethyl starch sodium (CMS-Na) employed as a depressant and polyether amine (PEA) as a collector. Micro-flotation tests demonstrated that CMS-Na exhibited strong selective depression of feldspar while maintaining high quartz recovery. Optimal separation conditions were achieved at pH 9.0 with 30 mg/dm3 CMS-Na and 4.0×10-4 mol/dm3 PEA, resulting in feldspar recovery decreasing sharply to 12.51% while quartz recovery remained high at 92.17%. The selectivity index (SI) increased significantly from 3.03 to 9.07, highlighting enhanced separation efficiency. Spectroscopic analyses, including FTIR, Raman, and XPS, revealed that CMS-Na selectively adsorbed onto feldspar surfaces mainly via coordination with Al-sites, with a small portion additionally forming hydrogen bonds with -Al-OH or -Si-OH, effectively suppressing its flotation. Conversely, CMS-Na exhibited limited interaction with quartz, enabling subsequent PEA adsorption. XPS data further confirmed that PEA adsorption on quartz and feldspar occurs via electrostatic and hydrogen bonding interactions, with CMS-Na selectively inhibiting PEA adsorption on feldspar. These results underscore CMS-Na's role as an environmentally friendly and effective depressant, enabling efficient separation of quartz and feldspar without hazardous chemicals like hydrofluoric acid. This study offers a sustainable approach to mineral resource utilization in industrial applications.