Characterization of membranes in non-steady state
Document typeBachelor thesis
Rights accessOpen Access
Ion exchange membranes (IEMs) have been established as a key component in industrial water desalination and electrolysis processes. Thus, nowadays, they are being studied and developed for application in new energy conversion and storage systems as well as efficient desalination and wastewater treatment processes. Ion permselectivity between counter-and co-ions, the most essential property in IEMs, makes these processes possible and/or efficient. Additionally, ion selectivity between different counter-ions is required for these novel processes to be efficient. However, they show minimal selectivity among monovalent ions, which limits their use in ion separations. Recent studies show that modification of ion exchange membranes with polyelectrolyte multilayers leads to exceptional monovalent/divalent ion selectivities. To better understand the mechanisms of transport of ions through active layers of membrane (polyelectrolyte multilayers) and to be able to perform its predictive modelling one needs to know electrochemical properties of membrane active layers. Their determination is strongly influenced by the multilayer structure of membranes. Conventional linear steady-state techniques yield information on the membrane average properties (involving both active layer and support) alone. In this study, ion-exchange membranes were modified with polyelectrolyte solutions and the prepared membranes were evaluated and characterized using different experimental techniques. The concentration-step technique was used to study the electrochemical properties of active layers of a commercial polymer FujiFilm Type 1 CEM and Type 1 AEM.An experimental set-up was built and the theory of non-steady-state membrane potential was used to analyse the information collected from various modes of experimental measurements.