1. School of Chemical Engineering, China University of Mining and Technology, Xuzhou 221008, Jiangsu, China
2. School of Resources and Environmental Engineering, Heilongjiang Institute of Science and Technology, 1 Tangchang Street, Daowai District, Harbin 150027, Heilongjiang, China
3. Advanced Chemical Technology Division, Korea Research Institute of Chemical Technology, P.O. Box 107, Yuseong, Daejeon 305-600, Korea