Photocatalytic removal of cationic and anionic dyes in the textile wastewater by H<inf>2</inf>O<inf>2</inf> assisted TiO<inf>2</inf> and micro-cellulose composites

The present study investigated the photocatalytic degradation of cationic (Methylene Blue and Methyl violet) and anionic (Acid violet) dyes present in textile effluent. The banana pseudostem derived Micro-cellulose (MC) and titanium dioxide (TiO2) composites were synthesized and characterised by X-Ray Diffraction (XRD), Fourier Transform Infrared (FT-IR), Diffused Reflectance Spectroscopy (DRS), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). The composite material showed microcrystalline anatase phase of TiO2 with a crystallite size of ≈6 nm. The TiO2 + MC composite were applied to batch reactor for the abatement of dyes in the presence of sunlight. The operational parameters such as pH and initial dye concentration were optimised for complete decolourization of dye molecules. The results of the study demonstrated that the combined hydrogen peroxide assisted photocatalytic degradation (TiO2 + MC + H2O2) removed 99% of Methylene blue (200 mg/L) dye in 150 min with 72% of COD reduction. Whereas, 6 and 7 h reaction time was required for the complete degradation of Acid violet and Methyl violet dyes. The synergy index of combined hydrogen peroxide assisted photocatalytic degradation was 3.54 which suggested positive synergism. The dye degradation mechanism is projected as through the combination of adsorption and direct photocatalytic oxidation by TiO2 + MC composite and oxidation by hydroxyl radicals (OH•).