Simultaneous impregnation-dealumination to produce SnO2-hierarchical zeolite for methylene blue elimination via adsorption-photodegradation

Abstract

Dye-containing wastewater from the textile industry is environmentally harmful. This study investigates the combination of tin oxide and hierarchical zeolite for dye removal through adsorption and photocatalysis. Zeolite has a large surface area; however, it suffers from diffusional limitation due to the small diameter of the micropore. The diffusional problem could be overcome by creating a mesopore using acid treatment. Impregnation of SnO2 using SnCl2 acid solution is estimated to create a hierarchical zeolite, hence the MB removal could improve via adsorption and photodegradation simultaneously. The SnO2-hierarchical zeolites have been prepared using SnCl2 solution in the presence and absence of H2O2. The results show that the acidity of the SnCl2 solution increases the mesopore volume of zeolite from 0.16 to 0.24 mL/g. The SnO2 phase was large and mainly located on the external surface of the zeolite for the sample prepared in the presence of H2O2. In contrast, the SnO2 phase was mainly small and located in the interior, blocking the zeolite's micropore for the sample prepared without H2O2 addition. The sample prepared using H2O2 showed a high MB removal of 97.0 % compared to the sample prepared without H2O2 at 64.4 %, which is not much different from the parent zeolite (52.2 %). The high MB removal can be attributed to the simultaneous removal via adsorption by zeolite and photocatalysis by SnO2 located outside the zeolite's granule, which was exposed to UV-C irradiation. The kinetics follow the Pseudo Second Order model for all samples. The best sample was 0.1 SnO2, with optimized kinetic parameters of qe=29.31mgMBgzeolit and ks=0.08gzeolitmgMB.s. The impregnation method not only spread the tin on the zeolite surface but created a hierarchical zeolite which improved the diffusional transfer and fastened the overall process.

Keywords

• Zeolite
• Mesoporous
• Impregnation-dealumination
• Adsorption-photodegradation
• Methylene blue