A comparison between the efficiency of CdS nanoparticles/zeolite A and CdO/zeolite A as catalysts in photodecolorization of crystal violet

The photodecomposition of crystal violet as a wastewater pollutant was studied using bulk CdS, nano CdS, nano CdS/zeolite A and CdO/zeolite A. Zeolite A was synthesized from waste porcelain at low temperature via a two step alkali conversion. Nano CdS/A was then prepared by a precipitation process after ion exchange of Cd2+ into zeolite A. Zeolite matrix was after that removed from the obtained photocatalyst to prepare nano CdS particles. For the sake of comparison, bulk CdS particles were prepared by a conventional precipitation method using Na2S and Cd(NO3)2 solutions. Finally, CdO/A was prepared by wet impregnation of parent zeolite NaA with Cd(NO3)2 solution. FT-IR, XRD and SEM methods were applied for the characterization of the samples. Afterward, the decolorization efficiency of the pollutant, in the presence of mentioned semiconductors, under static irradiation of sun, was compared. The degradation process was monitored during the experimental runs by UV/Vis absorption, COD and TOC concentration determination and HPLC methods. According to the results, nano CdS/A showed the most efficiency in photodecolorization of the pollutant, while no remarkable activity was detected in the presence of bulk CdS. CdO/A and nano CdS particles also showed good activities in photodecolorization of the contaminant.

Research highlights
► Nanoparticles of CdS and CdO form in zeolite A channels.
► Nano CdS/zeolite A shows a better efficiency than the others towards the photodegradation of crystal violet.
► All semiconductors out of the zeolite structure show a smaller photoreactivity.