Wet scrubbing-integrated sulfite/UVC photooxidation over Al2CuO4 for efficient methyl mercaptan removal

Methyl mercaptan (MeSH) is a highly odorous sulfur-containing volatile organic compound (VOC) whose gas-phase photochemical removal is constrained by mass transfer, incomplete oxidation, and unstable by-products. Herein, a sulfite/UVC-driven continuous wet-scrubbing advanced oxidation process (Al 2 CuO 4 -S(IV)/UVC) was developed for MeSH removal, in which CaSO 3 served as the slow-release S(IV) source and Al 2 CuO 4 functioned as a dual-pathway initiator under UVC irradiation. Under optimized conditions (0.20 g L −1 Al 2 CuO 4 , 4 mM CaSO 3 , pH 7.0), the system achieved complete MeSH removal within approximately the first 100 min and maintained >90.0% removal over the remaining 380 min of the whole operation, with robust adaptability to variations in pH, inlet concentration, and reagent dosage. Meanwhile, Al 2 CuO 4 facilitated both efficient S(IV) autoxidation under UVC irradiation and a continuous supply of reactive species via the Cu(II)/Cu(I) redox cycle. Mechanistic investigations based on quenching tests, ESR radical trapping, and sulfur-speciation analysis clarified the distinct roles and generation pathways of SO 5 •− /SO 4 •− and • OH. The system further retained >90.0% MeSH removal with sequential addition of S(IV) over 1920 min treatment, demonstrating its feasibility for continuous wet-scrubbing operation. Overall, the Al 2 CuO 4 -S(IV)/UVC wet-scrubbing process provides a promising platform for coupling gas absorption with in situ oxidation, highlighting its potential for the intensified purification of VOCs.