In the present study, we investigated the replacement of NaCN with pure depressant and depressant systems in the flotation separation of Cu-Mo bulk concentrate supplied by China Molybdenum Co., Ltd on a laboratory scale. The contrast experiments between the developed depressant system and NaCN were conducted in open circuit, and the results indicated that the developed depressant system achieved the similar Cu removal efficiency (cyanide 94.07% and developed reagent scheme 91.34%) and Mo recovery (cyanide 93.61% and developed reagent scheme 93.14%), which exhibited the advantages of environmental compatibility and economic adaptability. The results of FTIR spectra and XPS indicated that the chemical adsorption process may dominate the interaction of depressant with chalcopyrite, and a possible depressant mechanism is predicated along with a postulated adsorption mode for the surface interaction between disodium carboxymethyltrithiocarbonate (DMTC) and chalcopyrite. (C) 2016 Published by Elsevier B.V.