Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the low grade of P2O5 and high content of impurities. In order to obtain a qualified phosphate concentrate, the beneficiation of the low-grade phosphate ore is, hence, of great necessity. Many beneficiation techniques can be employed to upgrade the P2O5 grade of phosphate ores based on their characteristics in chemical composition and texture. The flotation process is most widely applied to balance the P2O5 recovery ratio and cost. In this review, the dominant techniques for the beneficiation of phosphate ores are introduced. Moreover, the factors that affect the flotation of phosphate ore, including the properties of mineralogy, flotation reagents (depressants and collectors) and flotation medium, were systematically analyzed.

Abstract:The effects of Ca 2+ , Mg 2+ , Al 3+ , and Fe 3+ on the flotation behaviors of apatite, dolomite and quartz were investigated through a micro-flotation test, and the influence of calcium ions on the flotation of these minerals was further elucidated by solution chemistry study, zeta potential measurement, and X-ray photoelectron spectroscopy (XPS) analyses. The results indicate that an appropriate amount of Ca 2+ and Mg 2+ can improve the floatability of apatite but had a negligible effect on the flotation performance of dolomite, whereas Al 3+ , Fe 3+ , and excessive amounts of Ca 2+ decreased the recovery of apatite and dolomite. The studied metal cations can activate quartz at a particular pH. It can be inferred from solution chemistry and zeta potential measurement that the influence of metal ions on the flotation of different minerals should be attributed to the adsorption of various hydrolysis species on the mineral surfaces. XPS analyses reveal that calcium ions can enhance the adsorption of anionic collector on apatite and quartz surfaces, and there are no apparent changes to be observed on the surface of dolomite in the absence and presence of calcium ions at a concentration of 2.5 × 10 −3 M, which was in good agreement with the micro-flotation results.

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Abstract:The mid-low grade sedimentary phosphate ore, abundant in silicate and carbonate gangue minerals, exhibits a poor processability. It is conventionally enriched using high temperature flotation to remove silicate gangues with fatty acid as a collector. Cottonseed oil has been proved to be an efficient collector for achieving ambient temperature flotation of the sedimentary phosphate ore used in this study. Flotation kinetics was investigated to ascertain the excellent collecting performance of cottonseed oil, as compared with oleic acid, and the phosphate flotation fitted well with the first-order flotation model. Based on the analysis of flotation reagent effect on the direct flotation process using the response surface methodology (RSM), a closed circuit of direct-reverse flotation for stepwise removing silicate and carbonate gangues from the sedimentary phosphate ore was established. Consequently, a required high quality of phosphate concentrate containing 30.16% P 2 O 5 was obtained, with a recovery of 90.90%. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) of the flotation products confirmed that the majority of silicate and carbonate gangues were effectively removed from the concentrate products.

The effect of fatty acid reactive oily bubble as a carrier in apatite flotation is examined by zeta potential, zeta potential distribution, induction time and micro flotation experiments, and further analyzed by the extended DLVO theory. The surface property of fatty acid reactive oily bubbles is determined by the dissociation degree of fatty acid contained in the oil film covered on reactive oily bubbles. Induction time tests show that the fatty acid reactive oily bubble presents a strong collecting power to apatite particles among pH 4.0-11.2, which is also confirmed by the zeta potential distribution and micro flotation experiments. However, the DLVO theory is fail to predict the coagulation at pH 9.01. A hydrophobic interaction is considered in the coagulation between reactive oil bubbles and apatite particles. The superiority of fatty acid reactive oily bubble system was confirmed and illustrated by the extended DLVO theory successfully.

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