TABLE OF CONTENTS When hydraulic pressure is applied to one surface of an ion exchange membrane immersed in a salt solution, water permeates through the membrane due to exclusion of salt by the membrane, and salt rejection increases with increasing fixed ion concentration of the membrane. [203] However, the flux of water through the membrane is extremely low though the flux changes slightly with species of ion exchanged ions due to differences in their hydration. [204] As explained in Chapter 3.8, Sollner reported the transport of ions through a mosaic ion exchange membrane in the presence of a concentration gradient of salt. [205] Also, piezodialysis using a mosaic ion exchange membrane may possibily desalinate saline water with a high water flux and high salt rejection. Figure 6.36 shows the results of piezodialysis of a 0.01 moll ?1 KCl solution using a mosaic ion exchange membrane (membrane thickness: about 200 , ion exchange capacities of cation and anion exchange parts are almost the same). [206] The figure shows the change in salt enrichment ratio [ E s = [( C II/ C I) ? 1] 100: C I, concentration of feed solution (high pressure side), C II, concentration of permeate (low pressure side)] and the change in the flux of water through the membrane (volume flux) with the concentration of feed solution, when 0.01 N KCl solution is dialyzed at 30 atm cm ?1. Though the salt...
