Influence of copper ions and calcium ions on adsorption of CMC on chlorite

The effects of copper ions and calcium ions on the depression of chlorite using CMC (carboxymethyl cellulose) as a depressant were studied through flotation tests, adsorption measurements, ζ potential tests and co-precipitation experiments. The results show that the electrostatic repulsion between the CMC molecules and the chlorite surfaces hinders the approach of the CMC to the chlorite while the presence of copper ions and calcium ions enhances the adsorption density of CMC. The action mechanisms of these two types of ions are different. Calcium ions can not adsorb onto the mineral surfaces, but they can interact with the CMC molecules, thus reducing the charge of the CMC and enhancing adsorption density. Copper ions can adsorb onto the mineral surfaces, which facilitates the CMC adsorption through acid/base interaction. The enhanced adsorption density is also attributed to the decreased electrostatic repulsion between the CMC and mineral surfaces as copper ions reduce the surface charge of both the mineral surfaces and the CMC molecules.