Removal of Orange II dye from aqueous solution by adsorption and photodegradation with visible light in presence of nitrogen doped titania nanocatalyst

Abstract

The possibility of treating water spiked with an azo dye, Orange II by adsorption and photo-catalytic decolourisation with nitrogen doped TiO₂ has been investigated. The prepared material has been characterised by XRD, BET, TEM, DRS and XPS study. The photocatalytic reaction is carried out after the attainment of adsorption equilibrium between N-TiO₂ and dye. The batch process is chosen to adsorb the dye under different experimental conditions. The photocatalyst dose, initial dye concentration and solution pH have been found to influence both the processes. The percentage decoulorisation increases from 73.42% to 91.32% on increasing the N-TiO₂ dose 0.25 to 1.25 g L^-1. However, further increase of the catalyst dose to 1.50 g L^-1 decreases the extent of decoulorisation (88.29 %). The lower dye concentration favour decolourisation (decreases from 84.24 to 75.43% for dye concentration of 18.0 to 36.0 µmol L^-1). At pH 2.0, N-TiO₂ decolourises almost 84% of the dye within 240 min of irradiation time. COD results reveal ~91% mineralisation of the dye on 360 min of irradiation. The percentage decolourisation of the dye is found to be higher with N-TiO₂ compared to TiO₂ P25. The adsorption process follow the Lagergren first order model while the decolourisation process follow modified Langmuir-Hinshelwood model.