Reactive Red 4 Dye-Sensitized Immobilized TiO2 for Degradation of Methylene Blue Dye

Abstract

The purpose of this study is to enhance photocatalytic degradation of cationic methylene blue (MB) dye. A 0.3 g of TiO2 and polymer binder was coated onto a clean glass plate using brush technique to develop an optimum immobilized TiO2 system. A comparison study between immobilized TiO2/PEG (Im/TiO2/PEG) system with and without RR4 sensitizer was carried out under 55-W fluorescent lamp. The photocatalytic degradation of MB was significantly enhanced for RR4 dye-sensitized Im/TiO2/PEG with first-order rate constant was ca. 0.0962 min−1 under 55-W fluorescent lamp. Same observation was observed under visible light irradiation, whereby those RR4-sensitized immobilized photocatalysts system were successfully improved the photocatalytic activity as compared with immobilized photocatalysts without RR4 as sensitizer. The photocatalytic enhancement under Im/TiO2/PEG/RR4 are due to the ability of RR4 dye to become electron (e−) donor for conduction band (CB) of TiO2, thus making TiO2 CB riches with electron, eventually this e− is used to remove MB dye by producing hydroxyl radical. This could be done due to the lower band gap of RR4 compared to the TiO2 itself. Therefore, low energy was needed by electron from valence band of RR4 dye to excite its conduction band. In addition, the LUMO energy for RR4 is higher than TiO2, and this allows electron transferring from the sensitizer to the semiconductor. The value of band gap was measured by using UV-Vis DRS, and the stability of RR4 in the formulation was detected using FTIR spectroscopy by observing the related bond present in the sensitized immobilized.