Energy & Fuels, Vol.34, No.7, 8037-8045, 2020
Absorption of H2S from Gas Streams by the Wet Ultraviolet/ Persulfate Oxidation Process: Mechanism and Kinetics
A new absorption technology of H2S 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 H2S absorption technology and the effect of technological variables on H2S absorption. Research on free radicals, products, and the H2S absorption mechanism was also executed. Results showed that the highest H2S separation efficiency reached 96.1% under optimal experimental conditions. An increase in UV light power, persulfate concentration, and solution pH enhanced the H2S absorption. The increase of the gas flow rate or H2S concentration weakened the H2S absorption. Reaction temperature showed a dual influence on the H2S absorption. Four routes were found in the absorption process of H2S center dot SO4- and (OH)-O-center dot that were generated by photolysis of persulfate were found to be the leading active species and played major roles in the H2S absorption. SO42- and S-0 were the main oxidation products in the liquid phase. With S2O82- concentration >= 0.02 mol/L, UV light power >= 36 W, solution pH >= 6.55, and H2S concentration >= 1500 ppm, the H2S 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 S2O82- concentration < 0.02 mol/L, UV light power < 36 W, solution pH < 6.55, and H2S concentration < 1500 ppm, the H2S absorption process belongs to a moderate speed reaction, which can be enhanced by simultaneously increasing the mass transfer rate and chemical reaction rate.