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International Journal of Chemical Engineering
Volume 2014 (2014), Article ID 270946, 16 pages
http://dx.doi.org/10.1155/2014/270946
Research Article

Effective Photodegradation of Methyl Orange Using Fluidized Bed Reactor Loaded with Cross-Linked Chitosan Embedded Nano-CdS Photocatalyst

1Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
2Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
3State Key Laboratory of Chirosciences, State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Shenzhen, China

Received 12 February 2014; Accepted 29 June 2014; Published 5 August 2014

Academic Editor: Dmitry Murzin

Copyright © 2014 Wai Szeto et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Chitosan-based photocatalyst composites containing CdS nanocrystals with and without glutaraldehyde or epichlorohydrin cross-linking treatments were investigated and the catalyzed photodegradation of methyl orange in aqueous solution was examined. In addition, the effects of catalyst dosage, initial dye concentration, and initial pH of the dye solution on the photodegradation kinetics were investigated. In this study, the effect of initial solution pH was more important than other factors. The photocatalyst composite could remove 99% dye in 80 minutes at pH 4. The catalyst composite was characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), fourier transform infrared (FT-IR), and visible reflectance spectroscopy. The dye removal mechanism of methyl orange involved an initial sorption process followed by photodegradation. The sorption process underwent the pseudo-second order kinetics, while photodegradation followed the Langmuir-Hinshelwood kinetics. Although the glutaraldehyde cross-linked chitosan enhanced the initial dye sorption, the epichlorohydrin cross-linked catalyst composite demonstrated a better overall dye removal performance, especially in the photodegradation step. Both chitosan encapsulated catalyst with and without epichlorohydrin cross-linking demonstrated the same pseudo-first order photodegradation kinetic constant of 0.026 min−1 and the same dye removal capacity. The catalyst composite could be reused but the photocatalytic activity dropped successively in each cycle.