Abstract: A combination electrodialysis method and apparatus comprising ultrafiltration membrane cell pairs interposed between a cation-selective membrane and an ion-nonselective membrane. The solution to be treated is fed to one side of the ultrafiltration membrane cell, a concentrating solution is delivered between the cation-selective and ion-nonselective membranes, and an electric field is applied across the assembly. Cations pass through the ion-selective membrane, ions of both polarities and weakly ionized substances pass through the ultrafiltration membrane which rejects the larger sized particles and molecules and anions pass through the ion-nonselective membrane to maintain electrical balance.

Abstract: An electrodialysis method for deacidifying a feedstream comprises a first cell defined by anion-selective membranes and bounded by a pair of cells defined by the anion-selective membranes and a pair of cation-selective membranes. The solution to be treated is fed to the first membrane cell, a basic solution and a concentrating solution are delivered, respectively, to one of the adjacent cells, and an electric field is applied across the assembly. Hydroxyl anions from the basic solution pass into the first cell for neutralizing the acid hydrogen cation while the acid anion passes into one of the adjacent cells through which also flows the basic solution cation to maintain electrical balance.

Abstract: A combination electrodialysis method and apparatus comprising ultrafiltration membrane cell pairs interposed between a cation-selective membrane and an ion-nonselective membrane. The solution to be treated is fed to one side of the ultrafiltration membrane cell, a concentrating solution is delivered between the cation-selective and ion-nonselective membranes, and an electric field is applied across the assembly. Cations pass through the ion-selective membrane, ions of both polarities and weakly ionized substances pass through the ultrafiltration membrane which rejects the larger sized particles and molecules and anions pass through the ion-nonselective membrane to maintain electrical balance.