Surface Functionalization of Activated Carbon Cloth for Wastewater Perchlorate Adsorption-Integrated Molecular Modeling and Experimental Energy Analysis

Abstract

Perchlorate (ClO4-) in drinking water is one of the most serious issues relating to drinking water contamination. This work reports both the experimental and computational investigation of wastewater perchlorate adsorption on surfactant-modified activated carbon cloth (ACC) in order to design an efficient water treatment system. Three different types of cationic surfactants including tetramethylammonium (TMA), benzyltrimethylammonium (BTMA), and dodecyltrimethylammonium (DDTMA) were employed in this study, and the ClO4- adsorption capacity of various adsorbents was determined in batch experiments for 24 hours. Among all, DDTMA-ACC exhibits the highest ClO4- adsorption capacity (4.5 times that of pristine ACC), the highest monolayer coverage capacity ( ${\Gamma }_{\max }$ ) value (0.59 mmol/g), an equilibrium adsorption constant ( $K_L$ ) value (35.90 L/mmol), and the lowest $\Delta G_{\text{ads}}$ value (-26.0 KJ/mol), revealing that ClO4- has a stronger affinity for ACC functionalized by DDTMA than ACC functionalized by other surfactants. Molecular dynamics (MD) simulations were also conducted to illustrate the interactions among ClO4-, surfactants, and a model graphite surface underwater environment. The relative number density profiles and cumulative number studies demonstrate that TMA/BTMA tends to form single-layered packing near the graphite surface, while DDTMA prefers to pack in a multilayered fashion. The dense packing behavior of DDTMA on the graphite surface can enhance the ClO4- adsorption, showing good agreement with experimental results.