Significantly surfactant-enhanced photochemical conversion of SO2 to sulfates on photosensitive substances

The photochemical conversion of SO 2 to sulfates on 4–(benzoyl) benzoic acid (4–BBA) was investigated deeply in the presence of anionic and cationic surfactants. The types of surfactants determined their effect behaviors, and cationic surfactants can significantly enhance the SO 2 oxidation on 4–BBA under irradiation, as shown by larger SO 2 uptake coefficients and sulfate production. Hydrophilic moieties in cationic surfactants have a greater enhancement effect on the photochemical conversion of SO 2 to sulfates than the corresponding hydrophobic moieties. Cationic surfactants obviously increased the accumulation of H 2 O on the surface, which was proved to be the main factor influencing the SO 2 uptake and the sulfate formation on 4–BBA. SO 2 lifetime and sulfate formation rate in the mixture system of photosensitive substances with surfactants were evaluated to be 2.25 days and 0.09 μg/(m 3 ·h), respectively.