RESEARCH NOTES Degradation of Phenol by Simultaneous Use of Gas-Phase Corona Discharge and Catalyst-Supported Mesoporous Carbon Gels Noriaki Sano,* ,† Takuji Yamamoto, ‡ Isamu Takemori, † Seong-Ick Kim, ‡ Apiluck Eiad-ua, ‡ Daisuke Yamamoto, † and Masaru Nakaiwa ‡ Department of Mechanical and System Engineering, Himeji Institute of Technology, UniVersity of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2201, Japan, and National Institute of AdVanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan This note reports an enhancement in the degradation of phenol in aqueous solution by simultaneous use of gas-phase corona discharge and mesoporous carbon gels supporting Ni or Co as catalyst. In this study, a direct-current corona-discharge reactor that consisted of a needle cathode placed above a water film was used. Disk-shaped carbon gel was submerged in the water film under the corona-discharge zone. The degradation rates of phenol by corona-discharge reactor without carbon gels, with plain carbon gels, and with metal-supported (Ni or Co) carbon gels were compared. When Ni or Co was supported on the carbon gel, the phenol degradation was enhanced in this reactor. The degradation of TOC was clearly enhanced by supporting Ni on the carbon gel. Such an effect cannot be realized in the use of TiO 2 -supported silica gel. Introduction There are several techniques using high-voltage electric discharge for the degradation of stable organic compounds in water. 1-10 In such processes, strong reactive species, such as hydroxyl radical OH, are produced by a series of plasma chemistry, and organic compounds are finally mineralized to CO 2 by oxidation by such species. Among these techniques, a method using gas-phase corona discharge that is contacted with treated water has been developed, and information related with this method has been accumulated in the past several years. 3-10 For serious demands for efficient water purification that degrades stable compounds, we still need to continue improving the efficiency of the relevant methods. To improve the efficiency of the advanced oxidation process (AOP), it is common to combine some effects to enhance the reactivity of the process. For example, ozone (O 3 ) oxidation can be conjugated with a TiO 2 photocatalyst to improve the reactivity, 11,12 and then a synergetic effect was realized. For another example, porous solid media was added to O 3 oxidation, and also a synergetic effect was realized. 13,14 Like these examples, a combination of some effects may cause preferable enhancement on reactivity in the water purification process. Although many types of microporous solid, i.e., activated carbon or zeolite, have been extensively applied to water purification as adsorbents, mesoporosity is more desirable than microporosity in order to apply porous solids to supporting materials for catalysts. Carbon gels, which possess developed and controlled mesoporous texture, 15 are considered to be suitable for this purpose. Furthermore, since carbon gels can be formed into various shapes, e.g., rod, bead, or disk, they are applicable to electrode materials. In the present study, we investigated the combination of catalyst-supported mesoporous carbon gels with the corona-discharge reactor as a novel application of mesoporous carbon gels. Experimental Section Corona-Discharge Reactor. The apparatus used in this study is schematically described in Figure 1. A needle cathode was placed above the water surface to generate the corona discharge. The distance between the cathode tip and the water surface was adjusted to 8 mm. The gas component above the water surface was ambient air, and its pressure was atmospheric. To generate the corona discharge from the cathode tip, the treated water was * Corresponding author. Tel.: +81-792-67-4845. Fax: +81-792- 67-4845. E-mail: sano@eng.u-hyogo.ac.jp. † Himeji Institute of Technology, University of Hyogo. ‡ National Institute of Advanced Industrial Science and Technology. Figure 1. Apparatus to degrade aqueous phenol by the corona-discharge reactor with carbon gel disk. 2897 Ind. Eng. Chem. Res. 2006, 45, 2897-2900 10.1021/ie050406q CCC: $33.50 © 2006 American Chemical Society Published on Web 03/10/2006