Selective flotation separation of apatite from dolomite utilizing a novel eco-friendly and efficient depressant for sustainable manufacturing of phosphate fertilizer

Abstract

Phosphate ores upgraded by froth flotation are widely used as vital raw materials for the sustainable production of phosphate fertilizer to maintain the food supply. In the flotation process, the efficient recovery of apatite from dolomite-bearing phosphate ore for phosphate fertilizer production depends significantly on the use of high-selectivity depressants. At present, traditional depressants used for phosphate ore flotation (e.g., sulfuric acid, phosphoric acid, cellulase enzyme, and β-naphthyl sulfonate formaldehyde condensate) have several disadvantages in practice, such as large dosages, poor selectivity, and high toxicity, resulting in high costs, low efficiency, and potential environmental damage in practice. Therefore, this study proposed a novel eco-friendly depressant, namely, acrylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer (P (AA-AMPS)), for the effective recovery of apatite from dolomite-bearing phosphate ore using a collector, sodium oleate (NaOl). The separation performance and adsorption mechanisms of P (AA-AMPS) onto apatite and dolomite were systematically explored via flotation experiments, infrared spectral (IR) detection, surface electrical characterization, X-ray photoelectron spectroscopy (XPS), and adsorption capacity studies. Micro-flotation results indicated that the addition of P (AA-AMPS) could achieve the efficient separation of apatite from dolomite at pH 8.5 by selectively depressing the dolomite flotation, in which more than 87.4% of apatite was recovered whereas the dolomite recovery was less than 14.7%. Surface analyses demonstrated that much greater amounts of P (AA-AMPS) were adsorbed onto dolomite than apatite, which might be attributed to the intense interaction of P (AA-AMPS) with magnesium sites of dolomite. Furthermore, the pre-adsorption of P (AA-AMPS) substantially prevented NaOl from being adsorbed onto dolomite, thereby strongly depressing its flotation. However, the significant adsorption of NaOl onto apatite contributed to its excellent floatabilty even in the presence of P (AA-AMPS). As a result, P (AA-AMPS) could accomplish the effective removal of dolomite from phosphate ore, as demonstrated by the high-quality apatite concentrate that was produced, which had a P2O5 grade of 38.53% and a MgO grade of 0.85%. Thus, P (AA-AMPS) can be considered as an eco-friendly and efficient depressant in the effective removal of dolomite to obtain clean apatite from phosphate ore via direct flotation for the sustainable manufacturing of phosphate fertilizer.