Photocatalytic Degradation of Organic Dyes Using Zinc Oxide Nanoparticles.

Abstract

Nanocrystalline zinc oxide particles were synthesized via sol-gel method using zinc acetate as precursor. Calcination temperature was varied to determine its effect on particle size. The resultant samples were subjected to X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR), UV-visible and Scanning Electron Microscopy (SEM) characterization techniques. X-ray diffraction results showed nanocrystalline wurtzite ZnO particles with crystallite size ranging from 16 nm to 30 nm respectively. FTIR detected bands below 1000 cm-1 representing Zn and Zn-O bonds, UV-vis showed absorption of ZnO particles in the ultraviolet range. Band gap energy of synthesized zinc oxide nanoparticles decreased with increasing calcination temperature and increasing crystallite size. Micrographs from SEM showed rice-like microstructure morphology of ZnO nanoparticles. The usage of ZnO nanoparticles as a photocatalyst was also explored in the degradation of Rhodamine B and Methylene Blue using UV-light with particular attention of the effect of particle size and catalyst load on the degradation efficiency of the respective dyes. Reusability of ZnO nanoparticles for photocatalytic degradation was also explored in this work. Results from photocatalytic degradation of Rhodamine B and Methylene Blue showed that nanoparticles calcined at 400 ℃ which has crystallite size of 16 nm had the highest degradation efficiency on both dyes with 93.5 % and 95.4 % degradation on Rhodamine B and Methylene Blue respectively. Results also showed that 0.2 g catalyst load exhibited the highest degradation efficiency with 95.41 % and 97.97 % degradation of Rhodamine B and Methylene Blue dyes respectively. Reusability of ZnO nanoparticles for photocatalytic degradation of RhB and MB over four different cycles showed a decrease in degradation efficiency from one cycle to another.