New insights into the interaction between monomers from acrylamide-based polymeric flocculants and montmorillonite: A DFT study

Abstract

Montmorillonite (MMT) is the main clay mineral in mine wastewater and also the most difficult fine particles to treat. In order to explore how common acrylamide-based organic polymeric flocculants interact with montmorillonite surfaces on micro scale, three kinds of active monomers of acrylamide-based organic polymeric flocculants were selected, and the microcosmic mechanism between the three active monomers and MMT (001) and (010) surfaces was analyzed by density functional theory (DFT). The simulation results of adsorption energy, charge analysis and partial electronic density of states show that the three studied monomers can be adsorbed on the (001) and (010) surfaces and 2-acryloyloxyethyltrimethyl-ammonium chloride (DAC) adsorbed more strongly than 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), which in turn adsorbed more strongly than acrylamide (AM). The adsorption on (001) surface is more favorable because the three active monomers can be stably adsorbed at both the easy and hard hydration sites on (001) surface, while only stably adsorbed at the hard hydration sites on (010) surface. After adsorption, the stronger the delocalization of the PDOS on the same surface, the shorter the hydrogen bond length and the larger the population value. Electrostatic interaction dominates the adsorption process on the Na-MMT (001) surface, whereas hydrogen bonding dominates the adsorption mechanism on the Na-MMT (010) surface. This research provides theoretical guidance for the design and synthesis of novel selective flocculants.