Photocatalytic production of hydrogen from sulfide and sulfite waste streams: a kinetic model for reactions occurring in illuminating suspensions of CdS

Abstract Use of a xenon light source to irradiate alkaline aqueous solutions of H 2 S and SO 2 in which CdS is suspended leads to the production of H 2 and thiosulfate. The variations of the reaction rate in response to changes in the concentration of catalyst, sulfide, sulfite and thiosulfate and in pH and temperature were investigated. The kinetic data were analyzed in terms of a Langmuir-Hinshelwood-Hougen-Watson model, in which the rate-controlling step is a surface reaction related to an anodic type reaction. The observed overall activation energy of the reaction (2.52 kcal/mol) is typical of photochemical processes.