Synchronous positive flotation separation of magnesite, dolomite, and quartz

Abstract

Herein, single-mineral flotation and artificially mixed-ore flotation of magnesite, quartz, and dolomite in sodium oleate (NaOL) were conducted under different conditions. By regulating slurry pH and adding inhibitors, the synchronous positive flotation desilication and decalcification of magnesite was achieved. At pH 9, 2-phosphate-1,2,4-tricarboxylic acid (PBTCA) facilitated excellent flotation separation and recovered 88.34 % and 8.93 % of magnesite and dolomite, respectively. Moreover, MgO and CaO grades of 46.21 % and 0.91 %, respectively, were achieved. Under these conditions, 3.18 % of quartz was recovered and a SiO₂ grade of 0.45 % was achieved. PBTCA considerably reduced the contact angle and adsorption capacity of dolomite in NaOL, slightly reduced the contact angle and adsorption capacity of magnesite in NaOL. Ca²⁺ and Mg²⁺ did not affect the contact angle of quartz at pH 9, whereas they considerably increased the contact angle at pH 11. Moreover, PBTCA weakly adsorbed on the magnesite surface and did not impact NaOL adsorption therein, strongly adsorbed on the dolomite surface, which was not conducive to NaOL adsorption on the same surface. Ca²⁺ and Mg²⁺ increased the surface electrical properties of quartz and activated its flotation. PBTCA strongly acts on the Ca sites on dolomite surface through chemical adsorption, hindering the adsorption of NaOL on dolomite surface and inhibiting its flotation. It has weaker adsorption on magnesite surface, while NaOL can act on magnesite surface through chemical adsorption and collect magnesite. Among the dissolved components of Ca²⁺ and Mg²⁺, CaOH⁺ and MgOH⁺ were the dominant components for activating quartz flotation and their concentrations were relative to the high flotation recovery of quartz.