UV photochemical oxidation of aqueous sodium sulfide to produce hydrogen and sulfur

Sodium sulfide solutions were illuminated with ultraviolet light (λ=253.7 nm) to produce hydrogen and disulfide ion in equimolar amounts. The quantum efficiency for hydrogen production was as high as 27% for a 0.5 M Na2S solution in a batch reactor. While light intensity and sulfide concentration had a pronounced effect on reaction rate, the photochemical process was found to be pH independent within the range 8.5–13.3. A mechanism involving adsorption of bisulfide ion on the inner sleeve of the photoreactor is postulated. Elemental sulfur could be recovered from the disulfide solution via purging with H2S and then filtering. The resulting filtrate was also photoactive, suggesting the possibility of a continuous closed cycle photochemical operation for H2S decomposition into its constituent elements.