Catalytic ozonation of high concentrations of catechol over TiO2@Fe3O4 magnetic core-shell nanocatalyst: Optimization, toxicity and degradation pathway studies

TiO2@Fe3O4 magnetic core-shell nanocomposite was coupled with ozone for catalytic ozonation of catechol in a batch environment. The catalyst features were characterized using FE-SEM, EDS, XRD, VSM and TEM techniques. The effect of several operating parameters including solution pH, catalyst loading, initial catechol concentrations and scavengers was assessed in parallel with a single ozonation process (SOP). Possible mechanism, intermediates identification and pathway of degradation were also performed. In all experiments, catalytic ozonation showed better performance, compared to SOP in the degradation and mineralization of catechol. The experimental data were in good agreement with pseudo-first-order kinetic model. Over 99% of catechol were removed by TiO2@Fe3O4/O3 system under optimum conditions within 60 min reaction and the mineralization degree was obtained >91%. The entire degradation of 50, 100 and 250 mg/L concentrations was obtained within 30 min treatment by TiO2@Fe3O4/O3. The bioassay and biodegradability tests indicated that the organic matters were removed effectively by TiO2@Fe3O4/O3 process and the biodegradability indices was improved as well. Particularly, hydroxyl radicals were dominant species during catechol degradation in the catalytic ozonation process. After ten consecutive use cycles, the degradation efficiency was reduced slightly (<5.0%) and reach 94.12% in tenth cycle over 60 min reaction. As compared to SOP, a significant synergistic effect was observed between ozone and TiO2@Fe3O4. Overall, application of TiO2@Fe3O4 in catalytic ozonation can be introduced as a successful and promising method for wastewaters treatment containing high concentrations of catechol, because of the simple and easy recovery of catalyst and excellent catalytic activity.