What is the role of the ion exchange membrane?
What is the role of the ion exchange membrane?
Ion-exchange membranes (IEMs) are unique in combining the electrochemical properties of ion exchange resins and the permeability of a membrane. They are being used widely to treat industrial effluents, and in seawater and brackish water desalination.
What is the process of cation exchange?
The process of cation exchange involves penetration of water via resin bead material known as exchange resins. Water ions are typically replaced with other ions that are fixed to these beads. This could result either in deionization or softening of water.
How do you make a cation exchange membrane?
Homogeneous ion-exchange membranes can be prepared by polymerization of monomers that contain a moiety that either is or can be made anionic or cationic, or by polymerization of a monomer that contains an anionic or a cationic moiety, or by introduction of anionic or cationic moieties into a polymer dissolved in a …
What are ion exchange membranes made of?
An ion-exchange membrane is generally made of organic or inorganic polymer with charged (ionic) side groups, such as ion-exchange resins.
How does anion exchange membranes work?
Ion exchange membranes contain high concentrations of fixed charges. They are permeable to ions of opposite charge (counterions) but repel ions of the same charge (coions). Protons are the only exception; they can permeate freely through hydration passages in an anion exchange membrane.
What is ion exchange membrane electrode?
Liquid-ion-exchanger electrodes utilize a liquid ion exchanger that is held in place in an inert, porous hydrophobic membrane. The electrodes are selective because the ion exchangers selectively exchange a single analyte ion.
What causes cation exchange?
Cation-exchange capacity arises from various negative charges on soil particle surfaces, especially those of clay minerals and soil organic matter. Organic matter also makes a very significant contribution to cation exchange, due to its large number of charged functional groups.
How does ion-exchange membranes develop?
More recently homogeneous ion-exchange membranes are produced by either a polymerization of monomers that carry anionic or cationic moieties or by introducing these moieties into a polymer which may be in an appropriate solution or a preformed film.
What is a cationic membrane?
Cation Exchange Membranes are proton-conductive polymer film, also known as electrolyte or ionomer, that allow only protons to cross-over (cation exchange), the key function of proton exchange membrane fuel cells and water electrolyzers. The polymer is chemically resistant and durable.
What are ion selective membranes?
These membranes allow the selective migration of ions while retaining water molecules. The driving force for the ion transport is a difference in free energy between the high saline and low saline solutions. This transport will continue until the equilibrium is reached where the chemical potential of salts is equal.
What is ion-exchange membrane electrode?
How are ion exchange membranes similar to cation exchange membranes?
The anion exchange membranes perform the opposite way compared to cation exchange membranes ( Figure 1-2 ). These selective permeations are carried out by DC current at an electorodialyzer. Similar behavior happens in ion exchange resin. The ion exchange resin is in the granular form and performs as adsorptive exchange of ions ( Figure 2 ).
Why are negative charged groups rejected by the cation exchange membrane?
Since negative-charged groups are fixed to cation exchange membrane, anions are rejected by the negative charge and cannot permeate through the cation exchange membrane ( Figure 1-1 ). This is because cation exchange membranes are only permeable by cations.
How is the ion exchange membrane ionic permselectivity?
Ion exchange membranes have ionic permselectivity and are classified into cation exchange membranes and anion exchange membranes. Since negative-charged groups are fixed to cation exchange membrane, anions are rejected by the negative charge and cannot permeate through the cation exchange membrane ( Figure 1-1 ).
How is anion exchange membrane in an AEM?
Related to point 2 above, the AEMs are generally submerged in aqueous NaOH/KOH solutions to exchange them to the OH − form typically from the supplied/synthesized halide anion forms. Again, the AEM must have the chemical stability to withstand this process.