The endowment of monovalent selectivity to cation exchange membrane by photo-induced covalent immobilization and self-crosslinking of chitosan

In this work, the monovalent selectivity was successfully endowed to conventional cation exchange membrane by photo-induced covalent immobilization and self-crosslinking of chitosan. The chemical and morphological changes of the membrane surface after modification were examined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Then, some electrodialysis experiments for Na+/Mg2+ system and H+/Zn2+ system which were used to simulate the seawater concentration and the hydrometallurgy applications, respectively, were performed to evaluate the monovalent selectivity of the modified membranes. Subsequently, diffusion experiments of NaCl and current voltage curve measurement experiments were also conducted to comprehensively estimate membrane properties, such as diffusion coefficient of NaCl, membrane electrical resistance and limiting current density. Moreover, the influences of some further treatments for increasing charging intensity and compactness of the immobilized chitosan layer, including quarternization or/and cross-linking, on membrane properties, were also investigated and analyzed. These contributed to recognize the dominant factors in selective separation and pave the road for tailoring the modified membranes for some specified applications. Anyway, the experimental results have clearly showed that the modified method put forward in this study was promising due to its facility, low cost and efficiency. (C) 2013 Elsevier B.V. All rights reserved.