Decolorization kinetic studies of Congo red catalyzed by Co-doped CdS nanoparticles

Abstract

The Cd0.97Co0.03S nanoparticles were prepared by using a controlled co-precipitation method. The nanoparticles were characterized by using UV-Vis spectra, XRD patterns and TEM image. The blue shift in the band gap of CdS semiconductor was observed with decreasing of the particle size. The XRD patterns prove the zinc-blend-type of Cd0.97Co0.03S nanoparticles. The size of nanoparticles less than 50 nm was confirmed through TEM image. The decolorization kinetics of Congo red catalyzed by prepared nanoparticles was studied under UV and sunlight irradiations. The decolorization study of dye with the initial concentration 20 mg/L shows the pseudo-first order kinetics with the apparent rate constant 1.35×10−2 min−1 at pH 7. The Cd0.97Co0.03S photocatalyst also indicates an excellent reactivity for bleaching of dye under sunlight irradiation with the apparent rate constant of 1.01×10−2 min−1. Degradation of 92–82% of Congo red was obtained in five cycles of reuse of proposed photocatalyst and dissolution of photocatalyst was found to be less than 0.2%.