Effect of calcium ions on scheelite flotation using mixed collectors

The flotation results show that Ca2+ significantly reduces the flotation recovery of scheelite using single dodecylamine (DDA) or single sodium oleate (NaOL), whereas Ca2+ hardly affects scheelite recovery using mixed collectors DDA/NaOL. Zeta potential measurements and solution chemistry confirm that the zeta potential of scheelite shows a significant positive shift after conditioning of Ca2+, which hinders the adsorption of same positively charged DDA on the mineral surface. Simultaneously, the addition of Ca2+ consumes single NaOL and generates Ca(OL)2. As for DDA/NaOL, the predominant components are RNH3+ and RCOO− at pH 7; they form new highly active complexes through electrostatic attraction, reducing adverse effect of Ca2+. Fourier transform infrared spectroscopy measurements and adsorption measurements further confirm that the pre-adsorption of Ca2+ does not interfere with the adsorption of mixed collectors.