Interaction mechanisms of typical collectors with zircon surfaces and their influence on surface morphology and hydrophobicity for selective flotation

Zircon is the primary mineral that contains the critical metals zirconium and hafnium. However, the extraction of pure zircon from its natural ore is challenging. The inadequate understanding of the interaction mechanisms between traditional flotation collectors, namely n-octyl phosphonic acid (nOPA), octyl-hydroxamic acids (OHA), and oleic acid (OL), with zircon, has hindered the development of highly selective flotation reagents. Therefore, a combination of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Zeta potential tests, contact angle measurements, and flotation tests was employed to elucidate the mechanism of collector adsorption on surface morphology and the chemical bonding interactions at the interface. The AFM, XPS, and DRIFTS results consistently demonstrate that all three reagents can chemically bond with zircon surfaces. nOPA exhibits stronger interactions with zircon compared to OL and OHA, as it coordinates with two zirconium sites to form a monolayer. Zeta potential and contact angle measurements reveal that the surface morphology and weak adsorption, which is driven by weak interactions, contribute to an improvement in hydrophobicity. Flotation results further validate that the three reagents can selectively float zircon in specific pH ranges. The interfacial bonding interactions, which are influenced by weak interactions, play significant roles in the flotation of zircon.