Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO₂ under UV and visible light

Abstract

Commercially available microcrystalline TiO₂ was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe²⁺ doped TiO₂ and Fe³⁺ doped TiO_2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag⁺ doped TiO₂ was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe³⁺ doped TiO₂ was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir–Hinshelwood pseudo–first-order kinetic model. Kinetic measurements confirmed that, Ag⁺ doped TiO₂ was most efficient in the UV range, while Fe³⁺ doped TiO₂ was most efficient in the visible range.

Keywords:

• BET
• XRD
• COD
• DRS
• mineralization
• photocatalysis