Photocatalytic decolourisation of a toxic dye, Acid Blue 25, with graphene based N-doped titania

Abstract

This study investigates adsorption of Acid Blue 25 dye and photocatalytic decolourisation with graphene based nitrogen doped TiO₂. The prepared material has been characterised by XRD, BET, DRS, PL, TEM and XPS study. The photocatalytic reaction was carried out after the attainment of adsorption equilibrium between graphene based nitrogen doped TiO₂ and dye. The photocatalyst dose, initial dye concentration and solution pH are found to influence both the processes. The percentage decolourisation increases on increase of amount of catalyst from 95.57% (load: 0.125 g L^-1) to 99.91% (load: 0.75 g L^-1). However, further increase of the catalyst dose to 1.25 g L^-1 leads to decrease in the extent of decolourisation. The decolourisation is favoured by lower dye concentration. The solution pH influences the reaction process and at pH 3.0, the material can decolourise almost 99% of the dye within 180 min of irradiation time. COD results reveal ~99% mineralisation of the dye on 420 min of irradiation. The percentage decolourisation of the dye is higher with graphene based nitrogen doped TiO₂ as compared to NTiO₂ or TiO₂ P25. The adsorption interaction follows the Lagergren first order model and modified Langmuir-Hinselwood model is preferably followed by dye decolourisation.