Absorption of H2S from Gas Streams by the Wet Ultraviolet/Persulfate Oxidation Process: Mechanism and Kinetics

A new absorption technology of H 2 S from gas streams by wet the UV/persulfate oxidation process in a photochemical bubbling reactor was developed. A series of studies were implemented to research the technical feasibility of the new H 2 S absorption technology and the effect of technological variables on H 2 S absorption. Research on free radicals, products, and the H 2 S absorption mechanism was also executed. Results showed that the highest H 2 S separation efficiency reached 96.1% under optimal experimental conditions. An increase in UV light power, persulfate concentration, and solution pH enhanced the H 2 S absorption. The increase of the gas flow rate or H 2 S concentration weakened the H 2 S absorption. Reaction temperature showed a dual influence on the H 2 S absorption. Four routes were found in the absorption process of H 2 S. SO 4 – and · OH that were generated by photolysis of persulfate were found to be the leading active species and played major roles in the H 2 S absorption. SO 4 2– and S 0 were the main oxidation products in the liquid phase. With S 2 O 8 2– concentration ≥ 0.02 mol/L, UV light power ≥ 36 W, solution pH ≥ 6.55, and H 2 S concentration ≥ 1500 ppm, the H 2 S absorption process belongs to a fast reaction, which can be further enhanced by improving the mass transfer rate (e.g., increasing gas–liquid contact area and enhancing turbulence in the reactor). With S 2 O 8 2– concentration < 0.02 mol/L, UV light power < 36 W, solution pH < 6.55, and H 2 S concentration < 1500 ppm, the H 2 S absorption process belongs to a moderate speed reaction, which can be enhanced by simultaneously increasing the mass transfer rate and chemical reaction rate.