1. State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering; Tianjin Polytechnic University; Tianjin 300387 P. R. China
2. Dept. of Mathematics; Tianjin Polytechnic University; Tianjin 300387 P. R. China
3. School of Environmental and Chemical Engineering; Tianjin Polytechnic University; Tianjin 300387 P. R. China
4. School of Civil and Environmental Engineering; University of Technology Sydney; NSW 2007 Australia