Microwave and ultrasound assisted dual oxidant based degradation of sodium dodecyl sulfate: Efficacy of irradiation approaches and oxidants

The present investigation explores application of microwave and ultrasound for degradation of important surfactant as sodium dodecyl sulfate (SDS). Understanding into the effects of power dissipation, potassium persulfate (KPS) and/or hydrogen peroxide (HP) loadings on the extent of degradation has been presented along with comparison of efficacy of microwave/ultrasound for activation. Under best treatment conditions of power and KPS loading, 99.7 % degradation of SDS at 80 mg/L as initial loading was obtained in only 18 min using the microwave combined with KPS approach. Keeping all operating parameters at the established best, use of KPS and addition of second oxidant as hydrogen peroxide was investigated and observed to enhance the extent and rate of degradation for the microwave with complete degradation of SDS obtained in 12 min. Ultrasound activation of KPS yielded lower efficacy compared to microwave with 95.4 % degradation of SDS obtained in 120 min under the optimized KPS loading as 2 g/L (molar ratio of KPS to SDS, rox, as 26.6), 150 W as power and 323 K as the temperature. The trials with dual oxidant in the presence of ultrasound showed reduced degradation of SDS compared to KPS alone as an oxidant. The analysis of both approaches clearly revealed that microwave assisted degradation of SDS was effective than ultrasound. The observed enhancement in rate and extent of SDS degradation using two oxidants in the case of microwave assisted approach compared to ultrasound, and demonstrated effectiveness of sulfate radical in deciding degradation are the key outcomes of the study. © 2020 Elsevier Ltd