Selective flotation separation of magnesite from dolomite and calcite using the mixed WG plus HEDP depressants

The decalcification of magnesite remains a difficult subject in mineral flotation. In this work, water glass and HEDP (1-hydroxyethylene-1,1-diphosphonic acid, expressed as WG + HEDP) were performed as the mixed de-pressants in magnesite-dolomite-calcite flotation separation. Micro-flotation test was conducted to study the inhibition effect of the mixed depressants, it indicated that 20 mg/L water glass and 15 mg/L HEDP were the optimal dosages because of the maximum differences in flotation recoveries. The inhibition mechanism of the mixed depressants was revealed by ways of zeta potential measurement, contact angle test and X-ray photo-electron spectroscopy (XPS) test. It could be concluded that WG + HEDP could co-adsorb on minerals surface, but they co-adsorbed stronger on dolomite and calcite surface than magnesite. Furthermore, sodium oleate (NaOL) could further adsorb on magnesite but not dolomite and calcite surface, resulting in the differences in wettability and floatability of minerals. At last, the real ore experiment confirmed the effectiveness of WG + HEDP on magnesite flotation.