Corona discharge plasma-based degradation of simulated residual linear alkylbenzene sulphonate and dodecyl benzene sulfonate surfactants

Abstract

Synthetic surfactants are used in a wide range of products ranging from household cleaning detergents to pesticide formulations. Due to their widespread use, residual surfactants are often released in large quantities into the environment, especially via wastewater and can act as potential toxicants. The present study explored the applicability of a non-thermal plasma, namely corona discharge plasma jet (CDPJ), for the degradation of residual surfactants so as to minimize their harmful effects to aquatic life. The plasma was generated using 20 kV DC power supply, with different input currents (1.00, 1.25 and 1.50 A) and at various electrode-to-sample distances (20, 25 and 30 mm). For degradation treatments, simulated residual surfactants (sodium dodecylbenzene sulfonate [DBS] and sodium linear alkylbenzene sulfonate [LAS]) and DBS-containing dishwashing detergents dispersed on slide glasses were exposed to CDPJ for predetermined periods of time (0-120 min). Results indicated that under optimal treatment conditions of 1.5 A current and 20 mm electrode-to-sample distance, the tested surfactants and surfactants in detergents were maximally degraded to about 57% following the plasma treatment for 120 min. Modeling of degradation kinetics indicated that Weibull distribution was the best-fit model, and decimal degradation times (delta) were calculated for different treatment conditions. The pure surfactants were degraded to a greater extent than surfactants in detergents.