Hydrolytic polymaleic acid: An environmentally friendly inhibitor for the flotation separation of parisite from calcite and fluorite

[Display omitted] •The flotation separation of parisite from fluorite and calcite was improved by using HPMA as depressant.•HPMA adsorbed on fluorite and calcite surface via chelation of Ca sites with carboxyl group.•HPMA hindered the further adsorption of OHA collector on the surfaces of fluorite and calcite.•HPMA exhibited highly selective inhibitory effect on Ca-bearing gangue minerals flotation. Hydrolytic polymaleic acid (HPMA) was used as a highly selective depressant instead of water glass to achieve the flotation separation of parisite from calcite and fluorite. The inhibitory effect and mechanism of HPMA on fluorite and calcite was investigated using micro-flotation, zeta potential, contact angle measurements, adsorption measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and quantum chemical calculations. The results from single and artificially mixed minerals showed that parisite could be successfully separated from calcite and fluorite by using HPMA as a depressant. Further analysis revealed that HPMA chemically adsorbed onto the Ca2+ active sites of calcite and fluorite, forming a hydrophilic compound, Ca(COOR), which prevented the octyl hydroxamic acid (OHA) collector adsorbing on their surfaces. In contrast, HPMA only weakly physically adsorbed onto the surface of parisite, allowing it to maintain good floatability after conditioning with HPMA. Therefore, HPMA has a potential as an inhibitor for effectively separating parisite from fluorite and calcite in rare earth ore flotation process.