Sonochemical Decolourisation of Reactive Blue 21 and Acid Red 114 in the Presence of TiO2 and Rare Earths

Abstract

The ultrasonic decolourisation of two commonly used textile dyes, Acid Red 114 (AR 114) and Reactive Blue 21 (RB 21), with different chromophoric groups, azo and phthalocyanine respectively, has been studied using TiO2 (consisting of mixture of crystalline and amorphous phases) in the presence of rare earths ions (Pr3+, Ce4+). The characterisation of TiO2 has been done through X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and N2 adsorption techniques. The decolourisation of AR 114 was faster than for RB 21 under all the experimental conditions. Almost complete decolourisation of both dyes was achieved in 5 min in the presence of US+TiO2+Ce. Ce4+ was found to be more effective than Pr3+. The decolourisation reaction followed second order kinetics. The effects of initial dye concentration and amount of TiO2 on the decolourisation of dyes have been found to be in the order; US+TiO2+Ce > US+TiO2+Pr > US+Ce > US+Pr > US+TiO2 > TiO2 >US. The decolourisation rate increased with increase in TiO2 amount and decreased with increase in initial dye concentration.