Ethoxylated alcohols as co-collectors in apatite, calcite and dolomite flotation

• Synergistic effect of nonionic fatty alcohol mixed with oleate on calcium mineral flotation. • Separation between phosphate and non-phosphate minerals at pH 4.5 with 20–25% nonionic in the collector mixture. • Better dispersion/dissolution of oleate and its transportation as oleate-fatty alcohol complexes to the mineral surface. • Synergistic and selective effects of nonionic co-collector in the flotation of both a sedimentary and a igneous phosphate ore. The separation of calcium minerals by flotation is difficult without the use of depressants. As an alternative, a mixture of collectors, either ionics or ionic-alcohol mixture, could be used for this mineral separation, and without depressants. It was found that addition of nonionic ethoxylated fatty alcohols to the oleate collector has a synergistic effect on the flotation of apatite, calcite and dolomite at pH 4.5 and 9.5. A potential mineral separation between the phosphate (apatite) and non-phosphate (calcite and dolomite) minerals is only possible at pH 4.5 with 20–25% nonionic in the collector mixture. This synergistic effect on the flotation of the three minerals corresponds to an increase in mineral hydrophobicity resulting from more collector, oleate and/or nonionic, adsorbing on these minerals. It was postulated that the nonionic alcohol forms a complex with oleate, which facilitates the collector dispersion and transport/attachment to the mineral surface resulting in a more dense collector surface packing. The increased collector adsorption using this collector mixture, and therefore synergistic effect on carbonate mineral flotation, could be predicted when the affinity of the oleate-alcohol complex for Ca sites is stronger than that of the oleate alone. The hypotheses on the selective collector adsorption and mineral hydrophobisation depending on the flotation pH were validated using a low-grade complex mineralogy igneous phosphate ore and a simple mineralogy sedimentary phosphate ore.