In order to investigate the interaction of water treatment polyelectrolytes with natural organic matters (NOM) that is an important target to be removed during the coagulation process in drinking water treatment, we perform molecular dynamics (MD) simulations. Poly(diallyldimethylammonium chloride) (polyDADMAC) and poly(epichlorohydrin dimethylamine) (Epi-DMA) are chosen as organic polymeric coagulants for water treatment, and TNB (Temple-Northeastern-Birmingham) humic acid trimer is used for a model NOM. It is found that quaternary ammonium groups in the polyelectrolytes electrostatically interact mainly with carboxylate groups in NOM, whereas phenolic and hydroxyl groups show less electrostatic interaction. Weak intermolecular force (e.g., van der Waals force) and hydrogen bonding also involve in aggregation of polyelectrolytes and NOM molecules. In this study, we analyze the effect of variables such as molecular weight of polyelectrolyte and NOM, pH, presence of inorganic coagulants, and polyelectrolyte/NOM ratio. Interaction pattern and conformation difference between polyDADMAC and Epi-DMA during coagulation are also studied.

Molecular dynamics simulation of cationic polyelectrolytes with natural organic matters

245th National Meeting (2013)

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