Performance assessment of the combined treatment for oxytetracycline antibiotics removal by sonocatalysis and degradation using Pseudomonas aeruginosa

Abstract

A facile method was applied to achieve complete degradation of oxytetracycline to carbon dioxide and water. In most abiotic degradation, it fails to degrade oxytetracycline to non-toxic products and leaves some intermediates. In this study, sonocatalytic degradation was performed to degrade the more toxic oxytetracycline to less toxic intermediates. In addition, the above intermediates was degraded by biological method, by providing these intermediates as carbon source for bacteria. In the sono degradation process, ZnO was used as sonocatalyst material, which was prepared by simple chemical precipitation method. At first 30 min removal of oxytetracycline was achieved by adsorption and following 30 min will be degraded under ultra-sonication. In addition, sodium peroxydisulfate was used to achieve complete degradation of oxytetracycline. For the best degradation, various parameters such as pH, temperature, dosage of ZnO and concentration of peroxydisulfate, were optimized. At a pH 7, temperature of 55 oC, ZnO dosage of 3 g L-1 and peroxydisulfate concentration of 1 g L-1, the removal efficiency is nearly 99% at the end of 60 min for initial oxytetracycline concentration of 2 ppm. After sonocatalytic degradation, the intermediate formed was naphthalene and was confirmed in this study. Pseudomonas aeruginosa was used for biodegradation of intermediates. This strain is best for using various aromatic compounds as carbon source as it can easily break naphthal rings using naphthalene dehydrogenase enzymes. The removal performance of oxytetracycline and intermediates by sono-bio catalytic degradation was also confirmed by analyzing the total organic carbon (TOC) concentration in the test sample.