Q. What are ion selective membranes used in electro dialysis of brackish water. Give examples.

Ans. Electro dialysis for brackish water: The ion selective membranes are used for compartmentalizing in electro dialysis. An ion selective membrane has permeability for only one kind of ions with specific range. A cations selective membrane embedded with negatively charge functional group such as RSO^-₃ RCOO^- permits positively charged ions to pass through it while an anion selective membrane embedded with positively charge functional group such as R₄N⁺ is permeable only to anions. The membranes are generally polystyrene based polymers which are thin and rigid.