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In many applications, the ionic resistance of an ion-exchange membrane shows a strong dependency on the external solution concentration and hydrodynamic environment. It is critical to understand the insights of ion exchange membrane process if its ionic resistance can be simulated accurately. In this paper, we have developed a new model by taking into account both the membrane properties that affect the membrane bulk resistance and hydrodynamic environment that affects the non-ohmic behavior of membrane resistance. The new model not only explains external solution concentration dependency, but also explicitly establishes a relationship between the measured membrane resistance and current density. The modeling results on the direct current (DC) and alternating current (AC) resistance of membranes are compared with experimental data measured under different external solution concentrations and applied to current densities. We demonstrate that the model accurately predicts the behaviors of sulfonated polypoly (2,6-dimethyl-1,4-phenylene oxide) membranes and fumasep ®-FKS and FAS membranes in all cases. The integrative modeling and experimental study provides insights into the ion-exchange membrane synthesis as well as reverse and conventional electrodialysis processes.

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China is currently not only the most populous country on earth, but also the world's largest greenhouse gas (GHG) emitter. As China's population growth continues contributing to the overall global population increase, the country remains a significant player in the global problems related to climate change. The Chinese government however has recognized that a low-carbon economy is in the country's long-term economic and social interests and this is now a key part of its national development strategy. This paper examines the evolution of policies for sustainability in China and explores their compositions, functions and operational mechanisms. Some emerging features and trends of China's development model are examined arguing that they represent a clear shift towards sustainability. Further problems and challenges associated with this change and how they impact on China's policies and strategies are also discussed.