Abstract
The aim of the present work is to combine TiO2/Graphene to increase photo-catalytic activity and obtain efficient removal of direct red 23 azo dye without difficult synthesis. Many operating variables which affect the process and some design aspects were studied. Reactor geometry is the main design parameter where slurry rectangular reactor and bubble column were compared with respect to hydrodynamic regimes, overall degradation efficiency and applicability in industrial scale. The removal rate was found to increase with increase in TiO2 concentration, approaching a limiting value at catalyst loads of 3g/L. For rectangular reactor only 0.005g/L of rGO able to enhance the activity of photo-catalysis. However, the optimum concentration of rGO is decreased in the bubble column reactor to be 0.001g/L. In both reactor systems, photocatalytic activity increase significantly by decreasing wavelength of the irradiated lamp from 365 nm to 254 nm. Also, results show the ability of bubble column reactor to treat high concentrations of dye up to 200 ppm. That makes it suitable to be integrated with biological system to convert non-biodegradable contaminates into biodegradable organics. That reduces the operating cost of the process and makes it more applicable in industrial scale. Rectangular reactor has the ability to be modified to use sunlight instead of artificial lamps because of high surface exposed to sunlight. In general the performance of bubble column reactor was better than rectangular reactor because it has excellent mass transfer characteristics, which enhance the efficiency of the process.
Highlights
Treatment of colored wastewater from textile or other industries is a serious problem that has attracted the attention of many researchers during last decades [1]
Combining TiO2 with carbonaceous nanomaterials is being increasingly investigated as a means to increase photocatalytic activity [6]
Industrial treatment of wastewater with various pollutants by photocatalytic oxidation with TiO2 is American Journal of Chemical Engineering 2018; 6(5): 107-120 uncommon because of the fast recombination rate of the photo-induced electron–hole pairs in TiO2 which reduces the efficiency of the photocatalytic reactions significantly, limiting its practical applications
Summary
Treatment of colored wastewater from textile or other industries is a serious problem that has attracted the attention of many researchers during last decades [1]. Because of the increasing levels and complexity of polluted effluents, conventional wastewater treatment technologies are often not sufficient for the purification and disinfection of polluted waters [3]. Processes such as gravity settling, filtration, air stripping, or adsorption to activated carbon are separation processes that leave a waste stream to be treated and disposed [4]. The combination of TiO2 and graphene had been proved to be an effective pathway to improve the photocatalytic activity of TiO2 due to the excellent adsorbability and conductivity of graphene [8]
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