Advanced oxidation of benzalkonium chloride in aqueous media under ozone and ozone/UV systems – Degradation kinetics and toxicity evaluation

This study investigates the degradation efficiency and kinetics of benzyldimethyldodecylammonium chloride (DDBAC) via O3/UV and O3 treatment. A catalytic effect of UV on ∙OH formation was found for the O3/UV treatment. A 91% DDBAC degradation efficiency was achieved within 20 min at an O3 dosage of 0.37 g∙h−1 and pH of 8.0, whereas only 19% DDBAC was degraded for the O3 treatment. A high pH, high O3 dosage and low initial DDBAC concentration are prompting DDBAC degradation for O3/UV and O3 treatment. However, unlike O3 treatment, O3/UV shows a great performance without requiring a high pH and high O3 dosage. Pseudo-first-order reaction kinetics were applicable for all process conditions. The scavenging experiments with tert-butanol confirmed a contribution of ∙OH radicals to DDBAC oxidation for the O3 treatment, while the combined effects of ∙OH radicals and UV photolysis were responsible for the O3/UV treatment. Furthermore, the complex matrix from real wastewater inhibited the oxidation process due to the competition for oxidative species between organic matter and DDBAC. Two Factor Interaction and quadratic statistical models were developed by a central composite design and proven to be precise and reliable to predict the DDBAC degradation process for the O3 and O3/UV treatment. The detoxification tests based on respirometric principles confirmed that the O3/UV system was quite efficient to reduce the toxicity of the aqueous media containing DDBAC, compared to other treatment techniques explored. Compared to the O3 treatment alone, the present study provides a more efficient approach for DDBAC degradation under mild conditions via the O3/UV treatment. © 2020 Elsevier B.V.