Effect Of Inorganic Anions On Photocatalytic Degradation Of Organic Dye

Researchers paid much attention to photocatalytic reaction with semiconductor particles. However, a few commercial applications of this technology are available at present; one of major reasons is the deactivation of the photocatalyst when photoctalysis is utilized to treat real wastewater. Therefore, effects of inorganic ions on degradation of dyes were studied. In this paper, effects of six common inorganic anions (F^-, I^-, Cl^-, SO₄^2-, H₂PO₄^-, HCO₃^-)on the photoactivity of P25 and TiO₂/zeolite catalyst have been investigated in the photodegradation of Sulforhodamine B(SRB). The particular results are as follows:1. Effects of pH and F^- on photodegradation of SRB on P25 or TiO₂/zeolite is investigated. It is found that the degradation rate of SRB increased with the decrease of pH in the acid media. The degradation rate of SRB on P25 under UV light in presence of F^- is faster than that in absence of F^-. But the degradation rate of SRB on TiO₂/zeolite under UV light in presence of F^- is slower than that in absence of F^-. The degradation of SRB both on P25 and TiO₂/zeolite under visible light is inhibited because of the addition of F^-. Quantities of H₂O₂ formed and change of chemical oxygen demand(CODcr)value were measured during the photodegradation of SRB on P25 or TiO₂/zeolite. Hydroxyl radical and superoxide radical were detected by ESR spectra.2. Effects of anions(I^-, Cl^-, SO₄^2-, H₂PO₄^-, HCO₃^-) on photodegradation of SRB on P25 or TiO₂/zeolite under UV light is investigated. It is found that the five common anions have negative influence on the degradation of SRB on TiO₂/zeolite, on the contrary, four of them besides I^- have positive effect on the degradation of SRB on P25. In addition, quantities of H₂O₂ formed and change of chemical oxygen demand(CODcr)value were measured during the photodegradation of SRB on P25 or TiO₂/zeolite. Hydroxyl radical and superoxide radical were detected by ESR spectra.3. Effects of anions(I^-, Cl^-, SO₄^2-, H₂PO₄^-, HCO₃^-)on photodegradation of SRB on P25 or TiO₂/zeolite under Visible light is investigated. For SRB/P25 system, I^- and Cl^- are found to inhibit the photocatalytic activity of P25, and SO₄^2-, H₂PO₄^- and HCO₃^- have little influence on the reaction. For SRB/TiO₂/zeolite system, I^-, H₂PO₄^- and HCO₃^- have negative effect.