Investigation of the aggregation and assembly mechanisms of trace organic compounds and dissolved organic matter using a combined approach of molecular dynamics simulations and experiments.

This study constructed generalized molecular models for diverse dissolved organic matter (DOM) components (lipids, peptides, carbohydrates, lignin, tannins, low-molecular-weight aromatics/aliphatics) and trace organic contaminants (TrOCs with positive, neutral, and negative charges). Large-scale molecular dynamics (MD) simulations (100 ns, 39 substances) were performed to elucidate cluster structures, surface properties, and aggregation dynamics, with and without an electric field. Four scenarios (Sce) were designed: (i) Sce-1 including atenolol (ATL) and DOM; (ii) Sce-2 including ATL, sulfamethoxazole (SMZ), carbamazepine (CBZ) and DOM; (iii) Sce-3 with the same composition as Sce-1 under an electric field; and (iv) Sce-4 excluding tannic acid (TAN) and humic acid (HA). Results showed that Ca2+, HA, and TAN act as bridging agents for stabilization, with π-π interactions, van der Waals forces, and hydrogen bonding as key drivers. Average radii of gyration were 4.01, 3.95, 4.25, and 4.22 nm in Sce-1 to Sce-4, respectively, while mean hydrogen bond numbers were 2.16, 0.79, 0.04, and 0.27, indicating more dispersed clusters in Sce-3 and Sce-4. In Sce-1 and Sce-2, short-range Coulombic (Coul-SR, -35,000 kJ/mol) and Lennard-Jones (LJ-SR, -1500 kJ/mol) energies yielded negative total non-bonded energies, forming compact aggregates. Experimental validation using river water confirmed simulation results. Adsorption with MIEX® resin (8 mg/L), followed by persulfate oxidation (0.3 g/L) catalyzed by Fe-Cu-Metal-Organic Framework (0.2 g/L), achieved complete ATL removal (20 mg/L) under an electric field. Fluorescence analysis showed 25.8 % peak intensity reduction. Electric fields disrupt clusters and enhance oxidant-mediated TrOC removal, while pre-removing of bridging molecules reduces cluster size for efficient elimination.