Use of citric acid and Fe(III) mixture as depressant in calcite flotation

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Calcite, as a gangue mineral, needs to be removed from the target minerals in the flotation. Single depressant citric acid (CA) or Fe(III) species has a limited depressive effect on calcite in the sodium oleate (NaOL) flotation system. In this paper, the floatability of calcite with single depressant (CA or Fe(III)) and mixed depressant (CA /Fe(III)) was studied by microflotation experiments. Solution chemical calculation and X-ray photoelectron spectroscopy (XPS) analysis were used to explain the relevant depressive mechanism. Microflotation experiments indicate that the addition of Fe(III) greatly improves the depressive effect of the depressant CA on calcite. When mixed depressant Fe(III)/CA is used and the depressant dosages of Fe(III) and CA are all 1 × 10−4 mol/L, the recovery of calcite is only 3.9% at pH 8.5. The mixed depressant Fe (III)/CA can be co-adsorbed on the calcite surface. The Fe(III) species in the slurry react with CA species first and then co-adsorbed on the calcium atomic sites of the calcite. Moreover, the Fe(III) species is first adsorbed on the oxygen atom sites of the calcite, and then the Fe(III) species provides the adsorption sites for further adsorption of citric acid. Therefore, the mixed depressant Fe(III)/CA can be adsorbed at both the calcium atomic sites and the oxygen atomic sites of the calcite. The mixed depressant greatly improves the depressive effect on calcite, which is beneficial to the flotation separation of calcite and related useful minerals.