Impact of crystal chemistry properties on the collector-mineral interactions observed for REE orthophosphates and oxides

Abstract

Controlled collector-mineral interaction experiments and detailed X-ray photoelectron spectroscopy characterization were performed on orthophosphate analogues of monazite and xenotime, two major rare earth element (REE) bearing minerals of economic interest. The objective of this work was to investigate the impact of various crystal chemistry parameters on interfacial features observed with collectors of relevance to mineral flotation (oleate, hydroxamate). Characterization of oleate-conditioned surfaces suggested that the collector interaction was independent of the orthophosphate crystalline structure and of site-specific trivalent lanthanide substitution. Hydroxamate results indicated that all structures with trivalent REEs exhibited spectral features with characteristics and degradation behaviour common to that of bulk hydroxamate during prolonged analyses, thought to reflect complexation of the collector specific to the trivalent rare earth cations. Peaks shifted to higher binding energy were observed for CeO2, possibly reflecting the presence of Ce in the tetravalent state. REE3+ and Al3+ orthophosphates also exhibited a unique and robust surface interaction, attributed to the impact of other ions in the mineral lattice (e.g. P5+). Our data suggests that crystal chemistry factors affecting local complexing environment may be as important as the expected selective trivalent chelating capacity of the hydroxamate on the nature and strength of the collector-mineral interaction.