Enhancing Monazite Flotation Performance by Introducing Fe³⁺ to the Solution

Despite the dominance of octyl hydroxamic acid (OHA) in promoting monazite flotation, its limited adsorption on monazite surfaces requires enhancement. This work stands as a systematic study of how the innovative practice of introducing Fe³⁺ to the solution boosted monazite flotation and examines its underlying mechanism. The initial microflotation tests found that at pH 8, the addition of Fe³⁺ drives up the flotation recovery rate of monazite to 72.65%, proving that Fe³⁺ greatly enhanced monazite floatability with OHA. Further analyses revealed that the adsorption of Fe hydrolyzing species onto the surfaces of monazite particles led to an increase in active sites for OHA chemisorption. Through an integrated characterization approach including ζ-potentials, Fourier transform infrared analysis (FTIR), and X-ray photoelectron spectroscopy (XPS), we elucidated the mechanism of how OHA reacted with both Fe³⁺ species and rare earth (RE) active sites and created Ce/La-O-Fe complexes on the surfaces of monazite particles. This process further generates hydrophobic OHA-Fe chelates, thereby boosting the flotation recoveries.