1. a College of Chemical and Biological Engineering , Guilin University of Technology , Guilin 541004 , P.R. China
2. b College of Electronic Engineering , Guilin University of Electronic Technology , Guilin 541004 , P.R. China
3. c Guangxi Key Laboratory of Environmental Engineering , Protection and Assessment , Guilin 541004 , P.R. China
4. d College of Environmental Science and Engineering , Guilin University of Technology , Guilin 541004 , P.R. China