Dye degradation studies using immobilized pristine and waste polystyrene-TiO2/rGO/g-C3N4 nanocomposite photocatalytic film in a novel airlift reactor under solar light

Abstract

Complex dyes are not completely removed in most wastewater treatment plants and thus released into nearby waterbodies posing problems to aquatic life and humans. In this study, a chemically synthesized nanocomposite photocatalyst containing TiO<inf>2</inf>, rGO and g-C<inf>3</inf>N<inf>4</inf> immobilized in a polystyrene film is evaluated for the degradation of the Cu-phthalocyanine complex dye (Remazol Turquoise Blue, RTB) in a multiphase airlift reactor under sunlight. Both pristine and waste polystyrene were used in the synthesis of the film. The characterisation of the powder photocatalyst composite as well as the immobilized photocatalyst film is performed using particle size analyzer, SEM-EDX, BET, XRD, XPS, FTIR, and ICP-OES. The optimization of various parameters affecting the photocatalytic decolourization such as the g-C<inf>3</inf>N<inf>4</inf> quantity in the composite catalyst, catalyst loading, the initial concentration of dye, use of waste polystyrene and catalyst reuse has been studied thoroughly. The photocatalytic treatment of RTB dye under optimum conditions for 90min shows that the decolourization (60%) and degradation (51.43%) as measured by TOC analysis are quite similar. The possible breakdown compounds from the parent molecule after the photocatalytic operation are identified by HPLC-MS. In conclusion, the immobilized nano-composite photocatalyst incorporated into a multiphase airlift reactor, is a very promising system to improve the water quality by TOC reduction, before discharge to nearby natural water sources. © 2019 Elsevier Ltd.