Synthesis and characterizations of metal oxide-sulfonic acid functionalized zsm-5 for photocatalytic degradation and adsorption of dimethylarsenic acid

Abstract

TiO2 and ZnO were incorporated into ZSM-5 using titanium tetrachloride and zinc nitrate as the precursors respectively. The functional group of ZSM-5 was further modified using mercaptopropyl trimethoxysilane (MPTS). This method was used to produce a two-in-one composite namely TiO2-ZSM5-SH and ZnO-ZSM5-SH which holds the abilities to degrade organic pollutants as well as to remove them from the environment. Determination of the composition and morphology of all synthesized catalyst complexes were characterized using Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HR-TEM). Results obtained indicated that the average diameters for TiO2-ZSM5-SH particles are 2.398 µm, slightly larger than the diameter of ZnO-ZSM5-SH particles with an average of 1.8067 µm. Both TiO2-ZSM5-SH and ZnO-ZSM5-SH appeared as sphere-like shape and amorphous since both metal oxides were incorporated into the ZSM-5 pores. The compositions of these complexes were proven by the presence of a strong silica absorption band showing the existence of Si-O stretching vibrations and SiO2 asymmetric vibrations in the synthesized complexes. For TiO2-ZSM5-SH, the Ti-O stretching vibration can be seen at 3467.29 cm-1 and at 1637.86 cm-1 while Zn-O absorption band appeared at 455.52 cm-1 in ZnO-ZSM5-SH. The symmetric and asymmetric vibrations of –CH2 and –CH3 indicate the existence of alkyl groups in the ZSM-5. The ability of catalyst complexes synthesized as photocatalyst were applied and tested on the photodegradation of dimethylarsenic acid (DMA) under ultra violet (UV) radiation which showed that these catalyst complexes are proven be able to degrade DMA into less toxic intermediates and are able to adsorb the remaining arsenic species from the aqueous solutions.