Synthesis, characterization and application of zinc oxide nano particles for removal of hexavalent chromium
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The present study was conducted to evaluate the adsorption efficiency of synthesized nano zinc oxide (n-ZnO) for the removal of hexavalent chromium (Cr6+). The synthesized sample was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Batch experiment results revealed that low dose (4 g L−1) of n-ZnO was highly efficient at the initial metal concentration of 9 mg L−1 in acidic conditions (pH 2) at 50 °C for the contact time of 90 min. A Langmuir adsorption isotherm model was found to be best fitted indicating a homogeneous surface and the adsorption followed pseudo-second order kinetics. Intra-particle diffusion was not a rate limiting factor in the present study. Thermodynamic study revealed that the adsorption process was endothermic and spontaneous at all the studied temperatures with increasing randomness.
KeywordsCharacterization Chromium Nano zinc oxide (n-ZnO) Removal efficiency Adsorption
The authors are thankful to University Grants Commission, India for providing financial support (UGC-REF. No. 20591, NET-DEC. 2009) and the Institute of Environment and Sustainable Development and Department of Botany, Banaras Hindu University, Varanasi, India for providing necessary infrastructure. The authors also want to acknowledge the Head, Department of Metallurgy, for SEM analysis which was done at the National Microscopy Centre, Department of Metallurgy, Indian Institute of Technology-Banaras Hindu University. The authors are also thankful to three anonymous reviewers whose valuable suggestions significantly increased the level of the present work. I would like to thank Ashutosh Kumar Pandey and Ashutosh Mishra for their assistance in collecting data and material for the preparation of the manuscript.
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