Removal of Dodecyl Benzenesulfonic Acid by an Amine-Modified Membrane Adsorber

Abstract

The escalating global demand for clean water in the face of scarcity, driven by factors such as urbanization, industrialization, and climate disruptions, presents a critical challenge. The presence of dodecylbenzene sulfonic acid (DBSA) from detergents in water sources further compounds environmental concerns, necessitating effective remediation strategies. In this context, polyvinylidene difluoride (PVDF) membranes were modified via a redox-initiated radical polymerization to impart adsorption capabilities to the membranes. We hypothesized that if PVDF membranes were modified with monomers containing tertiary amine groups, then the PVDF membrane could effectively adsorb DBSA and be regenerable with a sodium hydroxide (NaOH) solution. We modified membranes with 2-(Dimethylamino)ethyl methacrylate (DMAEMA) [monomer] and methacrylic acid (MAAc) [comonomer]. The membranes were characterized using ATR-FTIR, SEM, contact angle goniometry, and BET. By introducing amine groups onto the PVDF surface, effective DBSA attachment was achieved, resulting in an increased DBSA removal rate from 8.9% for unmodified PVDF membranes to 98.9% for the best-performing modified PVDF membranes. The adsorption kinetics followed the pseudo-second-order model and the adsorption isotherms correlated well with the Freundlich model. Thermodynamic analysis revealed the adsorption process to be exothermic. Dynamic adsorption also showed a removal efficiency of 60–65% when using one single membrane coupon in the dead-end filtration cell. The regeneration experiments showed that the removal efficiency gradually decreasing from 97% during the first cycle to 51% by the fifth adsorption cycle. This research underscores the potential of surface modification techniques to impart new separation capabilities to membranes and to assist in the removal of harmful surfactants from contaminated water sources.