Mechanism analysis and validation of a novel high-efficiency depressant for carrollite-muscovite flotation separation: Experimental and DFT investigations

Cobalt, as a scarce transition metal resource, is widely used in batteries, catalysts, and alloys. Carrollite is an important source of cobalt; however, declining ore grades necessitate pre-concentration via flotation prior to smelting. The separation of carrollite is hindered by muscovite, a common gangue mineral in such ores. Although polymaleic acid (PMA) is widely used as a depressant for silicate gangue minerals, its effectiveness in depressing muscovite flotation has not been systematically investigated. This study introduces PMA to achieve efficient separation of carrollite from muscovite. Flotation tests showed that PMA had a minimal impact on carrollite recovery but significantly depressed muscovite flotation. Particularly in artificial mixed ore flotation, the muscovite content in the concentrate decreased from 25 % to 4.4 %, while the carrollite content remained above 45 %. Adsorption and wettability measurements confirmed the preferential adsorption of PMA on the muscovite surface, thereby significantly enhancing its hydrophilicity. In contrast, PAX (potassium amyl xanthate) primarily adsorbed onto carrollite, and PMA had a negligible effect on carrollite's wettability. These results indicate that PMA is an effective depressant for muscovite, enabling the separation of carrollite, which prompted further mechanistic analysis of its adsorption behavior. Firstly, FTIR spectroscopy detected chemisorption of carboxyl groups onto muscovite, confirmed by the carboxylate stretching vibration at 1609.86 cm⁻¹ . Secondly, DFT simulations and XPS analyses revealed that the carboxyl groups of PMA were deprotonated and formed ionic bonds with surface aluminum sites. The proposed mechanism suggests that PMA forms a hydrophilic barrier layer on the muscovite surface, altering its wettability to depress flotation.