High-efficiency molybdenite–galena flotation separation enabled by 4,6-diamino-2-mercaptopyrimidine as a novel selective depressant: Experimental evaluation and surface interaction mechanism

DM was first introduced as a galena depressant for Mo–Pb separation. • DM exhibited high selectivity by strongly depressing galena while exerting minimal effect on molybdenite. • DM chemisorbed on galena through S/N–Pb coordination and markedly reduced surface hydrophobicity. The inherent similarity of the surface physicochemical properties of molybdenite and galena poses a substantial obstacle to their selective flotation separation. In this study, 4,6-diamino-2-mercaptopyrimidine (DM) was investigated as a potential selective depressant for galena. Under conditions of pH 8 and 20 mg/L DM, molybdenite recovery exceeded 98%, whereas galena recovery decreased to 11.25%, corresponding to a separation index of 22.96. A combination of multiscale interfacial characterization methods, including adsorption measurements, electrokinetic and wettability analyses, FTIR, XPS, and DFT calculations, was employed to clarify the interaction mechanism of DM at mineral surfaces. The results collectively indicate that DM exhibits stronger adsorption on galena than on molybdenite, thereby significantly enhancing the hydrophilicity of galena. FTIR, XPS, and DFT analyses further indicate that the selectivity originates from chemisorptive interaction between DM and surface Pb sites through the involvement of its S and N donor atoms. Overall, these findings highlight the considerable potential of DM for the selective flotation separation of molybdenite from galena and provide mechanistic insight into the rational design and optimization of selective flotation strategies. Download: Download high-res image (288KB) Download: Download full-size image