Improving the depression selectivity of fulvic acid for the efficient upgrading of phosphate ores based on nitrification modification: Flotation performance and mechanism insights

Nitrified fulvic acid (N-FA) was synthesized and employed as a green and high-performance dolomite (Dol) inhibitor to remove Dol from apatite (Apa). The flotation results demonstrated that nitrification significantly improved the depression selectivity of fulvic acid (FA), resulting in excellent separation results. The wettability tests and Zeta potential results showed that N-FA had much stronger affinity toward Dol but diminished affinity to Apa in comparation with FA. The adsorption capacity, XPS and SEM-EDS results proved that the –COOH groups of N-FA strongly complexed with Ca²⁺ and Mg²⁺ atoms on Dol, formation of monolayer adsorption. While it physiosorbed on Apa weakly by means of multilayer due to the effect of electrostatic repulsion and steric hindrance. This work provides some new insights for the design of novel carbonate mineral depressant based on chemical modification of carboxylic acid polymer.