Effect of different catalysts on mesotrione degradation in water falling film DBD reactor

In this study the effect of different homogenous catalysts and their dosage on mesotrione degradation in water falling film dielectric barrier discharge (DBD) reactor was investigated. Four catalytic systems Mn2+ /DBD, Co2+/DBD, Fe2+/DBD and H2O2/DBD were examined. In order to find optimal conditions various concentrations of catalysts and specific energy density (SED) values were tested in each system. Mesotrione degradation efficiency was determined by HPLC-DAD and mineralization efficiency by TOC value. Degradation products were identified by UHPLC-Orbitrap-MS and compared after finding out the optimal concentration for each catalytic system. All studied catalytic systems have proved to be successful in improving mesotrione removal, but the highest improvement in degradation efficiency was obtained with catalytic system 5 ppm Fe2+/DBD (by 50% for SED 124 kJ/L) and 10 mM H2O2/DBD for improving mineralization efficiency (by 45% for SED 310 kJ/L). Nine degradation products were identified in catalytic DBD treatments. Main degradation products were: glutaric acid, 2-nitro-4-methylsulfonylbenzaldehyde and 2-nitro-4-methylsulfonylbenzoic acid. H2O2/DBD gave significantly different degradation products than other catalytic systems. Dominant degradation products in other systems were not identified in system with hydrogen peroxide, which supported the fact that the highest mineralization efficiency was achieved with peroxide catalytic system. Global toxicity of samples after degradation in each system was determined using Artemia sauna and they could be considered as "non toxic".