Catalytic ozonation of a petrochemical wastewater containing high concentration of dinitrotoluene

Catalytic ozonation of a real industrial wastewater containing recalcitrant nitroaromatic compounds was investigated by different catalysts, and removal of color and COD was tracked over time. The effects of operational parameters such as catalyst type (MnO2, Nano-MnO2, ZnO, SnO2, Fe3O4, nZVI, and diatomite earth), initial pH, ozone dosage, and catalyst dosage on the removal efficiency were studied. Experimental results showed that MnO2 performed significantly better than other catalysts, with Nano-MnO2 resulting in over 80 % COD removal, from 21,750 to 3915 mg/L. Conventional MnO2 catalyst, on the other hand, resulted in only 66 % COD removal. Besides, biodegradability of the recalcitrant initial wastewater improved from 0.29 to 0.88 after 3 h of ozonation. Color removal efficiency was nearly complete (> 99 %) for both conventional and Nano-MnO2. An analysis of complete degradation using GC–MS indicated that 2,4-DNT and other organics were completely removed; whereas, 2,6-DNT was partially degraded. [Display omitted] •Significant improvement in catalytic ozonation of high-COD industrial wastewater•Biodegradability index of wastewater changed from 0.294 to 0.876 upon treatment.•Kinetics of the catalytic ozonation was first order with different k-values.•A pathway for the reaction mechanism during catalytic ozonation has been proposed.