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The hydroxylamine method involves the synthesis of a new hydroxamic acid collector, i.e., phenylpropyl hydroxamic acid (PHA), from methyl cinnamic hydroxamic acid. Flotation test results show that PHA exhibits good selective collection ability. The adsorption mechanism of PHA is investigated using the zeta potential, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that PHA formed a new Ca–O bond with Ca2+ on the fluorite surface via chemical adsorption. A new five-element chelated hydroxamate group may have formed in Ca on the fluorite surface. The PHA selectivity is fully explained via density functional theory (DFT) calculations, and an adsorption model is established.

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In order to improve the recovery of rare earth elements, finding a collector with a strong selectivity ability had become the focus of research. In this paper, phenylpropyl hydroxamic acid (PHA) was used as a new hydrophobic surfactant collector for the separation of bastnaesite from calcite, and salicylic hydroxamic acid (SHA) was used as a reference collector. The results of a single mineral flotation test with SHA show that the reagent has good collection performance and selectivity. In addition, Zeta potential measurements and FTIR analysis show that PHA is adsorbed on the surface of bastnaesite by chemical adsorption, and the surface state of bastnaesite changes after PHA treatment. By XPS analysis, PHA interacts with Ce, and forms a Ce–O bond with Ce. It is speculated that the hydroxamic acid forms a five-element-chelated hydroxamic group with Ce on bastnaesite surface, so as to improve the hydrophobicity of bastnaesite, and make bastnaesite float more easily out of the pulp. According to DFT calculation, PHA has better adsorption capacity and stronger hydrophobicity than SHA, and shows superior electronic group capacity and chemical reactions that promote its flotation performance.

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