Photocatalytic Degradation of Dye Acid Orange Seven on Titanium Dioxide Photocatalysts Immobilized on Stainless Steel Coated Layers: Role of Catalyst Loading and Ultrasonic Treatment

Abstract

Supported titanium dioxide (TiO₂) was investigated for potential application in photocatalytic degradation of dye acid Orange 7 in textile wastewater. Two commercial powder photocatalysts, Degussa (P25) and Precheza (AV01), were immobilized on stainless steel plates of dimensions (75 mm × 25 mm) through Electrophoretic Deposition Process (EPD) from aqueous colloidal suspensions of n-TiO₂, c=10 g.L^-1 produced in methanol. Two sets of coated layers were prepared - using ultrasonically treated TiO₂ colloidal suspensions and without ultrasonic treatment. The prepared coated layers were fitted onto a four-hole photocatalytic reactor operating under batch-mode conditions. As a source of UV light, Sylvania LynxS, 11W UV lamps emitting light of wavelength between 320-400 nm with maximum wavelength at λ=355 nm was used. The current study aimed to evaluate the effect of ultrasonic treatment on the catalyst’s colloidal suspension and electrophoretic deposition loading (mg/cm²) on its surface area on the resultant photocatalytic degradation of dye Acid Orange 7. The photocatalytic degradation of the dye was monitored by changes in dye absorbance for 120 minutes at an interval of 30 minutes. Changes in dye concentration were determined by ultraviolet spectrophotometry at λ = 485 nm. The initial concentration of dye Acid Orange 7 used in the experiments was c=1×10^-4 mol. L^-1. The findings show that 61.1 % of dye mineralization was achieved after 120 minutes of photocatalytic degradation. The optimum catalytic loading for maximum photocatalytic degradation was determined at 0.75 mg/cm² for the two commercial powder catalysts - TiO₂ (P25/AV01) in ultrasonically treated TiO₂ (P25) and non-ultrasonically treated TiO₂ (AV01). Ultrasonic treatment of TiO₂ (P25) colloidal suspensions before immobilisation positively influenced its photocatalytic activity, whereas ultrasonic treatment negatively affected the photoactivity of TiO₂ (AV01). Overall, TiO₂ (AV01) proved to be more efficient by 28.6%, compared to TiO₂ (P25). The results show the potential application of UV-TiO₂ treatment model in the remediation of coloured dye Acid Orange textile wastewater.