Development of Novel Photocatalytic Reactor for Dye Wastewater Treatment

Abstract

Over the years, industrial development has increased, causing a rapid increase in all form of pollution. A large amount of organic waste released into the freshwater bodies have increased water pollution several folds. In this regard, an effective environmentally friendly process for wastewater treatment is urgently needed, because sometimes it is difficult to degrade different toxic pollutants efficiently by conventional methods. Photocatalytic nanoparticles are an excellent choice for the mineralization of organic pollutants present in wastewater. The use of the photocatalyst nanoparticle into a reactor is also challenging since a light source is compulsory to activate the catalysts. In this work, TiO2, rGO, g-C3N4 and TiO2/rGO/g-C3N4 mixture in two forms: an admixture and chemically synthesized composite photocatalysts were immobilized in polystyrene films and employed as a photocatalytic film. The characterizations were done using SEMEDX, FTIR, XPS, XRD, ICP-OES, BET-Surface area analyzer, particle size analyzer, band-gap analyzer, etc. Initially, the photocatalytic performance of the prepared TiO2 polystyrene film was checked followed by (TiO2, rGO, and g-C3N4)-admixture and then TiO2/rGO/g-C3N4-chemical composite. The photocatalytic oxidation of synthetic dye wastewater (Remazol Turquoise Blue) under ultra-violet and sunlight irradiation was carried out in different types of photocatalytic reactors (batch, scaled-up a batch with recirculation, and multiphase reactors). The reactor volume was varied from 200 to 2900 mL, and the degradation of Remazol Turquoise Blue was confirmed by TOC and HPLC analysis. The optimization of photocatalytic reaction parameters (effect of catalyst loadings, pH, initial dye concentration, light source, polystyrene photocatalytic film thickness, recyclability the film, oxidizing agents, etc), as well as the reactor parameters (recirculation rate, air flow rate, diameter ratio, etc), were investigated in detail systematically. The synergistic effect of the photocatalysts was also analyzed by using the admixture of the photocatalysts, which showed a great significance in this work. The photocatalytic treatment of RTB dye under optimized conditions shows that there was more than 90% decolorization in most of the reactors after 90 min of irradiation. Amongii various reactors used in this study, the multiphase photocatalytic reactor has unique way to utilize the photocatalyst, which makes it novel and efficient. Also, the multiphase reactor showed the best performance since the observed decolourization and degradation were almost same. To make this study cost-efficient and suitable for large scale application, waste polystyrene was used as a substrate material instead of pristine polystyrene. This work presents a simple, easy, economical, and eco-friendly way to deal with the toxic organic pollutants. The photocatalytic reactors used in this work are highly efficient and can be easily scaled up for the industrial-scale application and employed for any other organic pollutant present in the water.