Foam fractionation of ZnO crystal growth and its photocatalysis of the degradation of methylene blue
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Chien-Yen Chena) Department of Earth and Environmental Sciences, National Chung Cheng University, Minhsiung, Chiayi, 62102, Taiwan; and Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, United Kingdom
Chien-Cheng Chen Department of Biotechnology, National Kaohsiung Normal University, Yanchao Township, Kaohsiung County, 82444, Taiwan
Shao-Ju Shih Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Da’an Dist., Taipei 106, Taiwan
Pin-Yun Lin, Pei-Hua Chung, and Jheng-Sian Yang Department of Earth and Environmental Sciences, National Chung Cheng University, Minhsiung, Chiayi, 62102, Taiwan
Akuri Satyanarayana Reddy Department of Chemistry, Graduate School of EEWS, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
Kai-Chien Cheng and Young-Fo Chang Department of Earth and Environmental Sciences, National Chung Cheng University, Minhsiung, Chiayi, 62102, Taiwan (Received 4 January 2012; accepted 28 March 2012)
We report herein the crystal growth of ZnO nanoparticles by the foam fractionation method. In this study, the vertical column height of the foam was fixed and the velocity of the sparging air was varied, and the effect of foam flow rate on the synthesis of ZnO was investigated. The obtained ZnO consisted of aggregated platelets and had differing ultraviolet absorbances. The as-synthesized ZnO was hydrophobic because of the interaction between the anionic head groups of sodium dodecyl sulfate (SDS) and the ZnO under the precipitation conditions. The long chain of the SDS molecule was the cause of hydrophobicity. The contact angle of water was in the range of 95–105° for the obtained ZnO/SDS surface. The photocatalytic degradation efficiency of the as-synthesized (ZnO/SDS) and the calcined ZnO was investigated for methylene blue, and the calcined ZnO retained its activity even after three recycles. I. INTRODUCTION
Advanced oxidation by semiconductor photocatalysis is of increasing importance in the treatment of wastewater due to its ability to destroy a wide range of organic and inorganic pollutants without the generation of harmful byproducts.1 TiO22 and ZnO are important semiconductor photocatalysts; however, the large-scale treatment of water with TiO2 is uneconomical. A suitable alternative is nanosized ZnO, which is available at low cost. ZnO has the same band gap energy (3.2 eV) and follows the same mechanism of photodegradation as TiO2.3 The advantage of semiconductor photocatalysis is that it can be carried a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.179 J. Mater. Res., Vol. 27, No. 19, Oct 14, 2012
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out under ambient conditions and leads to complete mineralization of organic compounds. The use of ZnO has been demonstrated for the degradation of dyes4,5 and other organic contaminants.6 Advanced oxidation processes (AOPs) generate powerful oxidizing OH radicals, which destroy poll
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