a b s t r a c tFlotation has been used in industry for more than a half century as the primary technique for upgrading phosphate. While the flotation of phosphate was inefficient when oleic acid was used alone as a collector, therefore a mixed collector of oleic acid (HOl), linoleic acid (LA) and linolenic acid (LNA) was employed to improve the recovery of phosphate flotation. The batch flotation results showed that the optimal composition of the mixed collector was 54 wt.% HOl, 36 wt.% LA and 10 wt.% LNA. Additionally, the effect of pH on the mixed collector application was studied while considering the surface tension, contact angle and micro-flotation. The results showed that the mixed collector should be used at a pH of 9.5. Above a pH of 9.5, the adsorption of fatty acids dimers on the apatite surface hindered phosphate flotation. The influence of the mixed collector assembly on apatite flotation was also investigated. It was demonstrated that due to its low critical micelle concentration, a sufficiently hydrophobic apatite surface could be generated at a collector concentration of 60 mg/L. In addition, zeta potential experiments suggested that collector adsorption was governed by chemisorption. FTIR and XPS spectra studies further indicated that the chemical reaction involved the carboxyl groups of fatty acids and Ca species at the apatite surface for each fatty acid in the mixed collector.

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The characteristics of Huimin high phosphorus limonite ore and the beneficiation of this iron ore by sodium-carbonate-added carbothermic reduction, ultrafine grinding and magnetic separation were investigated. Iron particle size in reduced ore without Na2CO3 additive is tiny and the fayalite is abundant. It is indicated that the formation of fayalite is the main hindrance to accelerate the reduction of limonite. With a mass ratio of Na2O3 to ore of 10% additive, the reduction of limonite can be reinforced. The reinforcing affect may be caused by the increase of the reducing reaction activity of FeO and the acceleration of the carbon gasification reaction rate. Fluorapatite were not reduced in the low temperature reduction process and entered to gangue phases, after ultrafine grinding-magnetic separation process, a qualified iron concentrate with 76.47% Fe, a recovery of 73.20% is obtained with simultaneous decrease in the phosphorus content down to 0.25%.

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