Carboxymethyl cellulose (CMC), a negatively charged polymer, is commonly used as a depressant of talc. However, the separation of pyrite and talc can be deteriorated by the presence of calcium ions, which can facilitate the absorption of CMC onto both talc surfaces and pyrite. In this work, carbonate ions were introduced to solve this problem, and the effects of calcium and carbonate ions on the adsorption of CMC were also studied. Micro-flotation results revealed that CO32-. not only eliminated the inhibition of pyrite by Ca2+ and CMC, but also had no influence on the depression of talc at pH 6-10. The surface-specific study confirmed that the adsorption of Ca-2+ onto talc basal planes at pH 8.5 was negligible and could be improved by the presence of CO32-. The atomic force microscopy analysis showed the correlation between the coverage of CMC onto talc surfaces in the presence and absence of CO32-. A mechanism for the adsorption of CMC onto talc surfaces was proposed based on the morphological differences in the presence and absence of CO32-.