1. Center for Environmental Technology Research, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Korea, Department of Chemical and Biochemical Engineering, Dongguk University, 3-26 Pil-dong, Chung-gu, Seoul 100-715, Korea, and SK Corporation, 140-1, Wonchon-dong, Yuseong-gu, Daejon 305-712, Korea