Di/trialkyl phosphate surfactants for the flotation separation of niobite and calcite or quartz: superior collecting capacity and selectivity

Abstract

Selective flotation of niobite is crucial for the efficient utilization of niobium resources. In this study, di(2-ethylhexyl) phosphate (DEHPA) was systematically investigated as a selective collector for niobite flotation. Microflotation experiments demonstrated that DEHPA exhibits strong collecting ability toward niobite in a weakly acidic to neutral pH range (pH 5.0–8.0), resulting in high flotation recovery. Artificially mixed minerals flotation further confirmed that DEHPA enables efficient separation of niobite from calcite and quartz at pH 6 with an initial dosage of 1 × 10⁻⁴ mol/L, indicating its excellent selectivity. Zeta potential measurements revealed a pronounced surface charge shift of niobite after DEHPA adsorption, suggesting specific interfacial interaction. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that DEHPA chemically adsorbs onto the niobite surface through chemical reaction between its O atom(s) of the P(=O)-O⁻ groups and Nb(V) or Fe(II/III) species on niobite surface, generating the Nb(V) or Fe(II/III)-O-P bonds, thereby enhancing mineral hydrophobicity. These results elucidate the selective adsorption mechanism of DEHPA on niobite surface and provide theoretical guidance for the development of efficient phosphate collectors for niobium mineral flotation.

Keywords

di(2-ethylhexyl) phosphate / niobite / calcite / quartz / flotation separation / selective adsorption

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