Effect Of Inorganic Anions On Photocatalytic Degradation Of Organic Pollutants By TiO₂/Bentonite

Six inorganic ions F^-,Cl^-,HCO₃^-,SO₄^2-,I^- and H₂PO₄^- were applied to study their effect on the degradation of SRB on TiO₂/bentonite catalysts and were compared with P25. The results show that:1,Under UV light irradiation, if pH value was smaller, the photodegradation rate was faster without fluoride ion by UV-Vis spectra detection. And if pH value was stable, the more fluoride ion concentration was, the faster reaction rate was. On TiO₂/bentonite catalyst, when fluoride ion concentration reaches a definite value, its reaction rate will not change. The effect of fluoride ion on the production of H₂O₂ on P25 and TiO₂/bentonite was different. We detected superoxide radical and hydroxyl radical by EPR technique. The effect of fluoride ion on these two systems was different. These phenomena may be caused by the special structures of TiO₂/bentonite (It was a pillared structure, its BET surface area was bigger and its particle size was 57.9 nm by XRD, the result of TEM was similar with the result of XRD). We used TiO₂/bentonite catalyst for 11 times circularly and continuously. And its photocatalytic reactivity was stable. This phenomenon showed that TiO₂/bentonite catalysts were easier to separate from a dispersion system and their stability was good. It was an applicable catalyst.2,Under UV light irradiation, for TiO₂/bentonite catalysts, Cl^- has little effect on the degradation of SRB. HCO₃^- has an accelerative effect on the degradation of SRB. When SO₄^2- reaches a definite degree, it has an accelerative effect, too. I^- and H₂PO₄^- has a repressive effect on the degradation of SRB. For P25, Cl^- and SO₄^2- have little effect on the degradation of SRB. HCO₃^- and H₂PO₄^- have an accelerative effect on the degradation of SRB. I^- has an repressive effect on the degradation of SRB. The effect of inorganic ions on the degradation of SRB on TiO₂/bentonite and P25 is different. COD was detected to study their mineralization degree. H₂O₂ and EPR spectra were detected to discuss the different effect of inorganic ions on the degradation of SRB on TiO₂/bentonite and P25 primarily.3,Under visible light irradiation, for TiO₂/bentonite catalysts, Cl^- and SO₄^2- have little effect on the degradation of SRB. HCO₃^-, I^- and H₂PO₄^- have a repressive effect on the degradation of SRB. For P25, low Cl^- has an accelerative effect on the degradation of SRB. when Cl^- reaches a definite value, it has a repressive effect. HCO₃^- has a repressive effect on the degradation of SRB. SO₄^2-,I^- and H₂PO₄^- have more repressive effect on the degradation of SRB. To discuss the different effect of inorganic ions on the degradation of SRB, COD was detected to study their mineralization degree, we detected H₂O₂ by UV-vis spectra and active oxygen radicals during the degradation by EPR spectra.