ABSTRACT
The oxidative degradation of rhodamine B (RhB) with hydrogen peroxide activated by iron(II) tetra-(5,6-dichloro-1,4-dithiin)-porphyrazine (abbreviated as FePz(dtnCl(2))(4)) was studied by means of UV-Vis spectra, GC-MS and TOC analysis, in which the effects of pH, light, concentration of hydrogen peroxide and the degraded products of the RhB were investigated. The results indicate that FePz(dtnCl(2))(4) was found to exhibit high catalytic activity to activate hydrogen peroxide for the oxidative degradation of RhB and good stability over a broad pH range under visible light irradiation (lambda>420 nm). The conversions of RhB in 80 min were 99%, 85%, 52% and the TOC removals in 240 min were 91%, 64%, 18% when the initial solutions pHs were 2, 7, 11, respectively. HO(.) radicals were testified to generate in the biomimetic catalytic system both at pH 2 and 7 by means of spin-trapping electron spin resonance. However, control experiment with scavenging of HO() radicals displayed the quite different results at pH 2 and 7. Based on experiment results together with theoretic deduction, a mechanism for RhB oxidation involving two kinds of reactive oxidizing species was proposed, the homolytic cleavage generating the HO(.) radicals and the heterolytic cleavage generating the Pz(.)(+)Fe(IV)=O radicals.
Subject(s)
Ferrous Compounds/chemistry , Hydrogen Peroxide/chemistry , Metalloporphyrins/chemistry , Rhodamines/chemistry , Rhodamines/isolation & purification , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/isolation & purification , Catalysis , Coloring Agents/chemistry , Coloring Agents/isolation & purification , Hydrogen-Ion Concentration , Light , Minerals/chemistry , Oxidation-Reduction , PhotolysisABSTRACT
Bi, C and N codoped TiO2 photocatalysts were prepared by doping TiO2 with BiCl3 and KSCN in a sol-gel process (denoted as (Bi,SCN)-TiO2). The catalyst samples were then characterized by XRD, TEM, diffuse reflectance spectra (DRS), XPS, FT-IR and N2 sorption. Bi, C and N elements were detected both by XPS and elemental analysis, while S element was not found, suggesting that SCN- group may have decomposed during the sol-gel process. The effects of the doping on the properties and photocatalytic activity of the TiO2 were investigated. It was found that the cation and the anion affected the properties of TiO2 differently. The optical absorption onset of TiO2 red shifted in the presence of Bi3+, while long tail occurred in the presence of SCN-. The order of photoreactivity for TiO2 samples was as follow: (Bi,SCN)-TiO2>Bi-TiO2>undoped TiO2>p25 TiO2, whatever under UV or visible light illumination. The high photoreactivity of the doped TiO2 was also discussed.
