Synthesis, characterization and catalytic activity of easily recyclable zinc oxide nanobundles

A new self-assembly of ZnO nanobundle has been successfully synthesized in this research by thermal decomposition of zinc oxalate at atmospheric pressure without using any catalyst or solvent at moderate temperature. The XRD analysis showed that the synthesized nanobundles are hexagonal wurtzite-type pure polycrystalline zinc oxide and high resolution transmission electron microscope (HR-TEM) analysis showed that the synthesized nanoparticles size was 0-30 nm, and increases up to 10-70 nm during the bundle formation. To test the catalytic activity of ZnO nanobundles in catalytic ozonation process, 2-ethoxy ethyl acetate (2-EEA) was used as the model organic pollutant. The results show that the presence of ZnO nanobundles in ozonation process could further enhance 39.7% of 2-EEA decomposition and 9.5% of TOC removal. Increase the catalyst loading from 0.2 to 2 g/l would increases the removal rate appreciably. Further increase in the catalyst loading could not enhance the removal rate significantly. Since the direct reaction rate constant (k(D)) was found to be 0.675 M-1 S-1, implying that ozone is not a potential oxidizing agent for 2-EEA direct oxidation, catalytic ozonation is thus necessitated to accelerate the decomposition of 2-EEA by hydroxyl radicals produced in the catalytic ozonation process. AAS analysis showed that zinc ion was not leached from the catalysts in all experiments. The catalytic reusability was investigated up to four successive cycles and found that the catalytic efficiency was not decreased appreciably. The catalytic recyclability of nanobundles are investigated and compared with other nanoparticles such as ZnO and TiO2-P25, and found that nanobundles are easily recyclable when compared to the above said nanoparticles. It is concluded that the nanobundles are effective and easily recyclable in catalytic ozonation process. (C) 2007 Elsevier B.V. All rights reserved.