Nano-photocatalytic Mineralization and Degradation of Dye Acid Orange 7 on Titanium Dioxide Coated Layers in a Batch Mode Plate Photo Reactor: Role of Flow Rate and Inorganic Salts

Abstract

Recently, the environmental impact of discharged untreated dye wastewater has received extensive attention. Herein, the paper investigated the photocatalytic degradation of dye Acid Orange 7 in a batch mode photoreactor fitted with a TiO₂ coated layer of dimensions (10cmí—15cm). The coated layer was prepared by sedimentation from an aqueous suspension of c=5 g.L^-1 and annealed at 300°C. Polychromatic sun beds lamps were used as a source of Ultra Violet (UV) light with maximum intensity at λ= 365 nm. A UV-Vis spectrophotometer monitored changes in dye concentrations at = 485 nm. Photocatalytic degradation of dye Acid Orange 7; c= (2.5í—10^-5 mol. L^-1) was determined by changes in dye concentration under UV light irradiation. The results show that dyes can be effectively degraded by TiO₂photocatalyst and UV light of wavelength 300-400 nm. The effect of flow rate and inorganic salts (sodium carbonate, sodium sulfate) on dye Acid Orange 7 degradation was examined. The maximum absorption wavelength and maximum coefficient of molar absorptivity ) was determined at 485 nm and 20647 dm³.mol^-1.cm^-1. The presence of CO₃^2- ions in the dye solution accelerated photocatalytic degradation by 35.8% and 39.3% after 30 minutes and 60 minutes of photocatalytic degradation. Dye photodegradation was reduced by 76.4% after 2.5 hours of photocatalytic treatment with SO₄^2- ions dissolved in dye solution. Presence of SO₄^2-ions showed no effect. Additionally, a flow rate of 50 lit/hr. was effective by 85.1% compared to 100 lit/hr. after 4 hours of photocatalytic degradation.