Photo-oxidation Of Inorganic Sulfide And Organic Sulfide Under Visible Light Irradiation

Elimination of inorganic and organic sulfur-containing pollutants from water and air is one of the difficult taskes in environmental science and techology.In this thesis,metal phthalocycanines(MPc)have been used as a photosenstizer for production of singlet oxygen and thereafter for the sulfur-oxidation.MPc and their derivatives are important class of macrocylic compounds that are easily synthesized at low cost and can collect 50% of the energy available in solar spectrum.The use of solar light and molecular oxygen for waste treatment could be an economical and green solution to the environment problem.Five chapters are included in the thesis.Chapter 1 is an introduction about the physical and chemical properties of phthalocycanines.Chapter 2 is a review of the recent progress achieved on the photooxidation of inorganic sulfide and organic sulfide.In Chapter 3,the stability of eleven metal phthalocyanine sulfonates against UV(λ＞320 nm) or visible light(λ＞450 nm)in the presence of TiO₂ semiconductor has been studied in an aqueous medium.In Chapter 4,the photosensitized oxidation of inorganic sulfide in water by molecular oxygen under visible light(λ≥450 nm)irradiation has been examined over an immobilized aluminum tetrasulfophthalocyanine(A1PcTS)on a commercial anionic resin Amberlite IRA 400.In Chapter 5,the photocatalytic degradation of three organic sulfide compounds containing different functionalities has been studied over AlPcTS/resin and PdPcS/organoclay under visible-light irradiation.Although all the MPc dyes were quite photostable in a homogeneous solution,they underwent notably photobleaching in the presence of TiO₂.The degree of dye bleaching was strongly dependent on the central metal in the complex,whereas for each complex the bleaching rate under UV irradiation was much faster than that under visible light irradiation.The spectral analysis showed that the dye photobleaching led to complete destruction of the phthalocyanine ring.In addition,the visible light stability of the dye was greatly affected by physical properties of TiO₂ semiconductor,and the dye photostability could be improved by addition of electron sacrifice such as 4-chlorophenol.During the inorganic sulfide oxidation,the composite catalyst exhibited not only a good capacity for uptake of sulfide ions from water,but also a higher activity for the photosensitized oxidation of sulfide as compared to the unbound AlPcTS.Ionic chromatography analysis showed that sulfite and thiosulfate were the reaction intermediates,which were further oxidized into sulfate as the final product.Five repeated experiments showed that the immobilized sensitizer was reasonably stable and could be repeatedly used for the sulfide oxidation using visible light and molecular oxygen.The effects of experimental parameters such as AlPcTS loading and sulfide concentration were also examined and discussed in the text.During the organic sulfide oxidation,all composite catalysts exhibited a good activity under visible light irradiation.GC-MS analysis showed that sulfone and sulfoxide were the final products of 2-mercapto-benzoic acid,methyl-phenyl-sulfide and 2-propenyl-benzyl-sulfide oxidation.The The effect of operational factors such as the type of catalysts, solvent polarity and pH were systematically studied.Several repeated experiments showed that the immobilized sensitizer was reasonably stable.