Abstract:

Ten dyes with different structures were used to investigate the rules of photocatalytic oxidation degradation of dyes in TiO₂/UV system. The concentration, total organic carbon （TOC） and well as the concentration variations of NO₂^-,NO₃^-,SO₄2^-  and Cl^-in the solution were that most dyes have the similar degrees of degradation and mineralization, except the pH value of the solution as all tested. The results show cationic blue FGL with the strongest adsorption capability, the highest degradation rate and the lowest mineralization rate, that the pH values of most dyes at first decrease and then increase with the exception that the pH value of the reactive brilliant blue X-BR with the lowest degradation velocity continuously decreases, that less than 5 % of N in the solution turns into NO₂^-andNO₃^-and 15%-60% of--SO3Na and  Cl^-respectively turn into SO₄2^-  and Cl^-after the reaction, that both the naphthalene ring and the striazine structure are more stable than the benzene ring, that the naphthalene ring joined to one azo bond is more stable than that joined to two symmetrical azo bonds, and that the benzene ring joined to the azo bond is more stable than that being far from the azo bond.

Key words: dye, TiO₂/UV system, photocatalytic oxidation, degradation