Interaction mechanism of organic carboxylate with kaolinite and montmorillonite: A density functional theory study

Abstract

The covering of aimed minerals by kaolinite and montmorillonite is an important factor leading to poor flotation selectivity. Organic inhibitors with small molecular weights can significantly improve this phenomenon. We selected nine kinds of organic carboxylate inhibitors with small molecules, and the stable adsorption conformations and adsorption energy of nine kinds of carboxylate ions on kaolinite (0 0 1) and montmorillonite Na (0 0 1) surfaces were obtained using DFT calculations. We found that the hydrogen phthalate ion has the strongest interaction with both the kaolinite and montmorillonite surfaces. Finally, a mixed system of acetate-kaolinite (0 0 1) surface and acetate-montmorillonite Na (0 0 1) surface were constructed, and the bond populations between the acetic acid and mineral surface and the atomic Mulliken charges were calculated. The interaction mechanism of small molecular organic carboxylates with kaolinite and montmorillonite were explained directly at the atomic and electronic levels. This work might shed new light on the flotation separation of minerals associated with kaolinite and montmorillonite under the condition of small molecular organic carboxylates as inhibitor. And it provides with a reliable method to select inhibitors before flotation.