Efficient removal of VOCs emission from soil thermal desorption via MnCoOx/Kaolin activating peroxymonosulfate in wet scrubber

The heterogeneous advanced oxidation processes coupling with wet scrubber is a promising method for the treatment of VOCs produced by soil thermal desorption. Mn-Co bimetallic oxides/Kaolin (MnCoOx/Kaolin) were successfully synthesized via cation-exchange based impregnation-calcination. The abundant SiO-OH and AlO-OH groups on the Kaolin carrier can inhibit metal aggregation, and the synergistic effect between Kaolin and metal oxide can improve the catalytic performance. The removal rate of benzene via wet scrubber with MnCoOx/Kaolin as catalyst remained above 98 %, which was better than that of single metal oxide. Moreover, the system exhibited significant application effects on the single component (toluene, ethylbenzene, xylene) and BTEX mixture, with the removal rates maintaining at higher than 90 %. The dosing method of PMS was optimized, and the method of continuous dosing of oxidant was proposed instead of one-time dosing. The main active oxygen in the MnCoOx/Kaolin system was sulfate radical, as shown by the results of characterization analysis and quenching experiments. Based on the intermediates identified by GC-MS, a possible degradation pathway of benzene in MnCoOx/Kaolin + PMS system was proposed.