1. School of Chemistry and Chemical EngineeringShandong University of Technology Zibo 255049 P. R. China
2. School of Materials Science and EngineeringShandong University of Technology Zibo 255049 P. R. China
3. State Key Laboratory of Hollow Fibre Membrane Materials and Processes, Department of Chemical EngineeringTianjin Polytechnic University 399 Binshui West Road Tianjin 300387 P. R. China