Degradation of Simulated Residual Surfactants and Dishwashing Detergents by Dielectric Barrier Discharge Plasma

Abstract

Sodium dodecylbenzen sulfonate (DBS) and linear alkylbenzene sulfonate (LAS) are widely used in dishwashing products. Residual levels of these surfactants are commonly found on the surfaces of dishware following dishwashing. Residual surfactants and detergents can act as potential toxicants and may pose health risks. This study explored the applicability of dielectric barrier discharge plasma (DBDP) for the degradation of residual surfactants in order to minimize their harmful effects. The plasma was generated using 10 kV pulsed DC power supply at different input currents (2.0-3.0 A) and at various inter-electrode gaps (2.0-3.0 mm). Under simulatory treatment conditions, diluted surfactants (DBS and LAS) and DBS-containing dishwashing detergents dispersed on slide glasses were exposed to DBDP for predetermined periods of time. Results indicated that, under optimal treatment conditions of 3.0 A current and 2.0 mm inter-electrode gap, tested surfactants and surfactants in detergents were degraded in the range of 60- 70% following the plasma treatment for 120 min. Modeling of degradation kinetics indicated that Weibull distribution was the best-fit model, and decimal degradation times (δ) were calculated. Pure surfactants were degraded at relatively higher level than surfactants in detergents. Among these anionic surfactants, DBS was more rapidly degraded than LAS by plasma treatment.