Molecular Dynamics Simulation of Dual Polyelectrolyte Coagulation With Natural Organic Matters in Aqueous System

Molecular Dynamic Simulation of Dual Polyelectrolyte Coagulation

with Natural Organic Matters in Aqueous System

Yoon Jung Choi,^a Hyemin Lee,^a Jiwon Jung,^a Sang Hyuck Park^b and Seung Soon Jang^a

^a School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, GA 30332-0245

^b School of Science & Technology, Georgia Gwinnett College, 1000 University Center Lane, Lawrenceville, GA 30043

Abstract

In this research, water treatment using dual-coagulants is examined. Through Molecular Dynamics (MD) simulation, the coagulation process with natural organic matter (NOM) is studied and analyzed at molecular level. Two of polyelectrolytes, Polydiallyldimethylammonium chloride (PDADMAC) and Polyacrylic Acid (PA), are used as two coagulants. Those dual-coagulants are simulated with Humic Acid trimer with Temple-Northeastern-Birmingham (TNB) model. During the simulation, PDADMAC forms complexes with NOM in water phase, which are then further coagulated and flocculated with the secondary polyelectrolyte of the opposite charge. This simulation with two coagulants and NOM was investigated under various conditions of different solvent, ionic strength, and molecular weight of polyelectrolytes. Throughout the extensive simulation and analysis, it was found that the binding of PDADMAC with NOM is mainly due to electrostatic binding. It was also found that, even after the PDADMAC aggregates with NOMs, PDADMAC can still interact with PA through electrostatic interaction.