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The aim of this study was to evaluate the effect of sodium hexametaphosphate (SHMP), a complexing reagent for Ca and Mg ions, on iron ore reverse cationic flotation. Quartz and hematite samples contaminated with both Ca and Mg were subjected to microflotation assays at pH 10.5 with starch and etheramine, which showed that SHMP did not provide selectivity in the separation of these minerals. Zeta potential measurements, Fourier transform infrared spectroscopy of quartz and hematite without and with the studied reagents (starch, amine, SHMP, CaCl2/MgCl2) and published studies in the literature indicated that although the HMP anions removed the Ca and Mg ions from both minerals, it also formed complexes with the Fe3+ ions on the hematite surface, which prevented subsequent adsorption of starch and consequently decreased the selectivity for reverse flotation of iron ore.
Cruz et al. (Sun,) studied this question.