Comparative evaluation of anion doped photocatalysts on the mineralization and decolorization of natural organic matter

• Solar photocatalytic oxidation of humic acid.
• Use of bare and anion doped TiO2 specimens in solar photocatalytic treatment.
• Degradation of humic acid was modeled by pseudo first-order kinetic.
• EEM contour plots used for the elucidation of humic fluorophores.

The aim of this study was to assess photocatalytic performance of various anion doped TiO2 specimens on the degradation of natural organic matter represented by humic acids. Nitrogen doped (N-doped), sulfur doped (S-doped) and sulfur–nitrogen co-doped (S–N co-doped) TiO2 specimens were prepared according to a wet impregnation method. Their photocatalytic activities were evaluated with regard to degradation kinetics of humic acid in terms of UV–vis spectroscopic parameters (Color436 and UV254) and dissolved organic carbon (DOC) as indicators of decolorization and mineralization respectively. The presence of different dopants in TiO2 structure ended up differences in terms of decolorization and mineralization kinetics of humic acids. Moreover, use of pure anatase form of TiO2 (Hombikat UV-100) for anion doping came up with higher photocatalytic activity than anion doped TiO2 specimens prepared by using TiO2 composed of mixture of anatase and rutile (Degussa P-25). Humic acid fluorescence excitation emission matrix (EEM) contour plots showed that solar photocatalytic degradation pathway was TiO2 type specific irrespective of dopants.

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