Abstract
Using electrodialysis, ion permeation through porous alumina membranes wes examined below and above the isoelectric point, pH6. The pH-dependence of the amount of permeable anions (acidic dye and Cr2O72- ions) was found to agree with that of the ζ-potential. Since a porous alumina membranes in acidic solutions below pH6 have a positive charge, they will adsorbe such anions, which then migrate through the pores toward the anode. Both ζ-potential and permeability were observed to reach maxima at pH4. On the contrary, the behavior of basic dye cations was inverse to that of ζ-potential. Since at pH4, the membrane has the maximum positive charge basic dye cations cannot permeate due to electrostatic repulsion. At pH2 or 9, however, where the positive charge is less, slight permeation is possible.
