Oxidation and photooxidation of sulfide and thiosulfate ions catalyzed by transition metal chalcogenides and phthalocyanine complexes

The catalytic and photocatalytic activities of supported cobalt or zinc pht halocyanine complexes, bulk MoS2, MoS2 deposited on Al2O3, potassium interc alated MoS2 (K-0.33 H2O0.66 MoS2), CdS and polycrystalline nickel phosphoru s trisulfide (NiPS3) have been investigated in the oxidation of sodium sulf ide and Na2S2O3. The phthalocyanine complexes and the metal chalcogenides d o not catalyze, in the absence of light, the complete oxidation of the sulf ide ion to sulfate ion. The final product of the catalytic oxidation is the formed thiosulfate, No oxidation of Na2S2O3 has been registered in the dar k in the presence of any of the catalytic samples, Their activity was enhan ced upon irradiation with visible light. Thiosulfate appears to be the fina l product also of the photooxidation of the sulfide ion catalyzed by metal chalcogenides. They do not catalyze the further photooxidation of Na2S2O3. The only photocatalysts which favour with their presence the oxidation of t he sulfide and thiosulfate ions to sulfate ion, are the zinc phthalocyanine complexes. In this case, the photooxidation process involves singlet oxyge n. (C) 2000 Elsevier Science B.V. All rights reserved.