Cation Exchange Membranes
Cation exchange membranes refer to the exchange membranes with cations. Cationic membranes are usually of the sulfonic acid type. Cation exchange membrane can be regarded as a kind of polymer electrolyte. Under the action of water molecules, the cations on the positive membrane dissociate into the water, making the positive membrane negatively charged. Then electricity is applied outside the membrane, and under the action of an electric field, positively charged cations can pass through the cation membrane, while anions cannot pass through due to the same sex repulsion, so it has selective permeability.
Preparation of cation exchange membranes
According to the chemical structure or the connection mode of charge groups, ion exchange membranes can be divided into heterogeneous membranes and homogeneous membranes. In these two kinds of membranes, the charged groups are physically mixed or chemically combined with the membrane matrix, respectively. Heterogeneous membranes are not suitable for high-demand fields, so more research is focused on homogeneous membranes. The following introduces a polystyrene/polyvinylidene fluoride (PVDF) cation exchange membrane manufacturing technology route. That is, the polystyrene/PVDF alloy particles are first sulfonated using the same method as the industrial production of the polystyrene-based strong acid cation exchange resin, and then directly thermoformed to prepare the cation exchange membrane. This technical route realizes the combination of the classic strong acid cation exchange resin sulfonation method and the traditional heterogeneous ion exchange membrane thermoforming process, and fully reduces its manufacturing cost.
Fig. 1 Preparation of the polystyrene/poly(vinylidene fluoride) (PVDF) cation exchange membrane(Lei Y L, et al., 2014)
Renewable energy power systems such as solar and wind are one of the solutions to global warming, but because of their low energy density and intermittent nature, energy storage systems are needed. All-vanadium redox liquid flow batteries (V-RFBs) offer the advantages of higher electric potential and higher energy density and can be a preferred option for energy storage systems. Cation exchange membranes can be a key component for V-RFB energy storage system applications.(Kim J G, et al., 2010)
- Water Desalination
- Industrial wastewater treatment
- Food and pharmaceutical industries
- Lei Y L, et al. Sulfonation Process and Desalination Effect of Polystyrene/PVDF Semi-Interpenetrating Polymer Network Cation Exchange Membrane[J]. Polymers, 2014.
- Kim J G, et al. Application of Psf–PPSS–TPA composite membrane in the all-vanadium redox flow battery[J]. Journal of Industrial & Engineering Chemistry, 2010.