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

Abstract

The catalytic and photocatalytic activities of supported cobalt or zinc phthalocyanine complexes, bulk MoS 2, MoS 2 deposited on Al 2O 3, potassium intercalated MoS 2 (K 0.33 H 2O 0.66 MoS 2), CdS and polycrystalline nickel phosphorus trisulfide (NiPS 3) have been investigated in the oxidation of sodium sulfide and Na 2S 2O 3. The phthalocyanine complexes and the metal chalcogenides do not catalyze, in the absence of light, the complete oxidation of the sulfide ion to sulfate ion. The final product of the catalytic oxidation is the formed thiosulfate. No oxidation of Na 2S 2O 3 has been registered in the dark in the presence of any of the catalytic samples. Their activity was enhanced upon irradiation with visible light. Thiosulfate appears to be the final product also of the photooxidation of the sulfide ion catalyzed by metal chalcogenides. They do not catalyze the further photooxidation of Na 2S 2O 3. The only photocatalysts which favour with their presence the oxidation of the sulfide and thiosulfate ions to sulfate ion, are the zinc phthalocyanine complexes. In this case, the photooxidation process involves singlet oxygen.