The effect of chelation on the selective transport of alkaline-earth metal ions in asymmetric cellulose acetate hyperfiltration membranes
Article first published online: 9 MAR 2003
Copyright © 1977 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 21, Issue 7, pages 1795–1800, July 1977
How to Cite
Lee, K. L., Hopfenberg, H. B. and Stannett, V. T. (1977), The effect of chelation on the selective transport of alkaline-earth metal ions in asymmetric cellulose acetate hyperfiltration membranes. J. Appl. Polym. Sci., 21: 1795–1800. doi: 10.1002/app.1977.070210707
- Issue published online: 9 MAR 2003
- Article first published online: 9 MAR 2003
- Manuscript Revised: 28 APR 1976
- Manuscript Received: 19 MAR 1976
The rejection of calcium and/or magnesium ion by asymmetric cellulose acetate hyperfiltration membranes is increased significantly by formation of the corresponding alkaline-earth metal chelate. Typically solute fluxes are reduced by a factor of 5 consequent to chelation with ethylenediaminetetraacetic acid (EDTA) at pH 6.0. Selective chelation and, in turn, selective transport of magnesium is observed when equimolar solute mixtures corresponding to 1:1:1 magnesium:calcium:EDTA are hyperfiltered. Under these conditions, calcium successfully competes for the stoichiometrically limiting EDTA, and the rejection of magnesium is lower than the rejection observed for the hyperfiltration of the MgEDTA2− complex in the absence of competitive calcium. Alternatively, the rejection of the CaEDTA2− complex is increased under these identical conditions, presumably as a consequence of specific interactions between the available free magnesium and the cellulose acetate membrane. The effects reported here all seem to be related to reductions in solute diffusivity associated with the increased size of the alkaline-earth metal ion complex.