Srikant S. Kulkarni

Ion Exchange Membranes: Preparation, Properties, and Applications

Membrane science is a relatively new area of applied chemistry and chemical engineering and plays a vital role in the field of alternative energy and separation applications. The field of membrane science is therefore an emerging area with enormous industrial and public health significance. Today, various kinds of separation membranes have been studied and utilized industrially in different processes including reverse osmosis, nanofiltration, ultrafiltration, microfiltration, electrodialysis, and pervaporation. Technical feasibility of all these processes largely depends on membrane and its properties. Among the separation membranes, ion exchange membranes are one of the advanced separation membranes. Therefore, this chapter addresses on different types of ion exchange membranes with reference to their preparation, properties, as well as their industrial applications. Although ion exchange membranes are broadly classified into homogeneous and heterogeneous membranes, this chapter also covers other types of ion exchange membranes such as amphoteric, mosaic, bipolar, interpolymer, and graft and block copolymer membranes. At the end, prospectives and conclusions on the ion exchange membranes have also been highlighted. The relevant literature was collected from different sources including Google sites, books, reviews, and research articles.

Preparation of poly(vinyl alcohol)–silicone based hybrid membranes for the pervaporation separation of water–acetic acid mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle x-ray diffraction and differential scanning calorimetry. A remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen bonding and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as cross-linking agent. The membrane containing 1 : 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10−2kg/m2h at 30°C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values obtained, showing that water permeation is lower than that of acetic acid, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal because of the higher selective nature of membranes. The negative heat of sorption values (ΔH s) for water in all the membranes suggests a Langmuir mode of sorption.