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