Selective Coagulant Recovery from Water Treatment Plant Residuals Using the Domain Membrane Process
Municipal Water Supply
Published Online: 15 JUL 2005
Copyright © 2005 by John Wiley & Sons, Inc.
How to Cite
Prakash, P. and SenGupta, A. K. 2005. Selective Coagulant Recovery from Water Treatment Plant Residuals Using the Domain Membrane Process. Water Encyclopedia. 1:139–141.
- Published Online: 15 JUL 2005
Let us consider solutions of aluminum sulfate (feed) and sulfuric acid (recovery) in a Donnan membrane cell divided into two chambers by a cation-exchange membrane that allows only cations to migrate from one side to the other but rejects any passage of anions according to Donnan's co-ion exclusion principle (9). At equilibrium, the electrochemical potential of aluminum ion Al3+ ion () in the feed solution will be the same as that in the recovery solution for both aluminum and hydrogen ions, which corresponds to the following Donnan equilibrium condition:
If the ratio is 10, it means is 1000 times greater than . Thus, by maintaining high hydrogen ion concentration in the recovery solution, aluminum ions can be driven from the feed to the recovery side even against a positive concentration gradient, i.e., from a lower concentration region to a higher concentration one.
- reverse osmosis;
- Donnan membrane cell;
- co-ion exclusion