Flotation separation of parisite from calcium-bearing gangue minerals using polyaspartic acid as a depressant

The flotation separation of parisite from calcium-bearing gangue minerals, such as fluorite and calcite, poses a significant challenge in the rare earth ore production process. In this study, an eco-friendly and highly selective depressant polyaspartic acid (PASP) was adopted in the flotation separation of parisite from calcite and fluorite, and its depression mechanism was investigated through various surface analysis and testing methods, including zeta potential tests, contact angle measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The flotation test results indicated that PASP significantly inhibited the flotation of fluorite and calcite, with negligible effect on parisite when using octyl hydroxamic acid (OHA) as a collector at weak alkaline pH. The artificial mixed mineral flotation proved that PASP could achieve effective flotation separation of parisite from calcite and fluorite. Zeta potential tests and FTIR analyses demonstrated that the adsorption of PASP prevented OHA adsorption on calcite and fluorite surfaces, with minimal impact on OHA adsorption on parisite surface. XPS analyses confirmed that PASP was mainly chemisorbed on the surfaces of calcite and fluorite through the chelation reaction between polar groups (–NH– and –COO⁻) of PASP with the Ca²⁺ on these surfaces. AFM clearly showed the agglomerative adsorption of PASP on the surfaces of fluorite and calcite. Thus, PASP could be an efficient depressant for calcite and fluorite in parisite flotation, providing novel insights into addressing rare earth ore flotation challenges.