Enhancing copper–molybdenum separation: The role of DMTD in flotation processes

The separation of chalcopyrite and molybdenite in porphyry copper–molybdenum ores is challenging owing to their similar floatabilities, making the use of depressants necessary. Inorganic depressants are commonly employed in the flotation industry to increase the difference in hydrophobicity between chalcopyrite and molybdenite; however, these depressants pose significant environmental risks. Recently, novel organic depressants have attracted considerable interest because of their abundance and low toxicity. This study investigated the use of 2,5-dimercapto-1,3,4-thiadiazole (DMTD), an activator recently employed in copper oxide flotation, as a depressant for the separation of chalcopyrite and molybdenite. Micro–flotation experiments demonstrated that DMTD exhibits a notable selective depression effect, significantly suppressing the flotation of chalcopyrite without adversely affecting the flotation of molybdenite. Furthermore, DMTD maintained its depression effect on chalcopyrite flotation even in the presence of xanthate. Contact angle measurements were used to analyze changes in hydrophobicity, corroborating the micro–flotation results, while SEM-EDS elemental distribution maps further confirmed the selective adsorption of DMTD on the chalcopyrite surface. XPS and AFM analyses were conducted to elucidate the microscale interaction mechanism between DMTD and chalcopyrite. The specific interaction sites on the chalcopyrite surface were identified through changes in elemental binding energies, while the evolution of surface morphology revealed how DMTD interacts with chalcopyrite in the xanthate system.