Synergy of adsorption and visible light photocatalysis to decolor methyl orange by activated carbon/nanosized CdS/chitosan composite

Activated carbon/nanosized CdS/chitosan (AC/n-CdS/CS) composites as adsorbent and photoactive catalyst were prepared under low temperature (<= 60 degrees C) and ambient pressure. Methyl orange (MO) was chosen as a model pollutant to evaluate synergistic effect of adsorption and photocatalytic decolorization by this innovative photocatalyst under visible light irradiation. Effects of various parameters such as catalyst amount, initial MO concentration, solution pH and reuse of catalyst on the decolorization of MO were investigated to optimize operational conditions. The decolorization of MO catalyzed by AC/n-CdS/CS fits the Langmuir-Hinshelwood kinetics model, and a surface reaction, where the dyes are absorbed, is the controlling step of the process. Decolorization efficiency of MO is improved with the increase in catalyst amount within a certain range. The photodecolorization of MO is more efficient in acidic media than alkaline media. The decolorization efficiency of MO is still higher than 84% after five cycles and 60 min under visible light irradiation, which confirms the reusability of AC/n-CdS/CS composite catalyst.