Thermally activated persulfate for gaseous p-xylene removal: Process optimization, mechanism investigation, and pathway analysis

The coupling of wet scrubber with thermally activated persulfate (PS) for the removal of gaseous p-xylene was studied in the present work. The effects of process parameters (i.e., activation temperature, gas flow rate, PS dosage, and absorption solution pH) on p-xylene removal were studied. The removal efficiency increased with the activation temperature and PS dosage, while decreased with the increase of gas flow rate. The inhibition effect was observed when the pH of the reaction system was alkaline due to the existence of NH3(aq) resulting from ammonium translation. P-xylene was efficiently eliminated under the optimal conditions with a maximum removal efficiency of 78.5%. The most important radicals, namely, SO4 − and HO , were investigated by electron paramagnetic resonance, and the selectivity of SO4 − was determined by quenching tests. HO and SO4 − oxidations accounted for 41.3% and 37.4% of the removal of p-xylene, respectively. The contribution of SO4 − increased with the accumulation of H+. Moreover, the absorption solution reused via adding PS and it still showed perfect removal capacity for p-xylene at the end of each cycle. Finally, a possible degradation pathway of p-xylene was proposed based on the measurements of intermediates being detected in the gas and liquid phases.