Standard Article

Selective Coagulant Recovery from Water Treatment Plant Residuals Using the Domain Membrane Process

Municipal Water Supply

  1. Prakhar Prakash1,
  2. Arup K. SenGupta2

Published Online: 15 JUL 2005

DOI: 10.1002/047147844X.mw1760

Water Encyclopedia

Water Encyclopedia

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.

Author Information

  1. 1

    Pennsylvania State University, University Park, Pennsylvania

  2. 2

    Lehigh University, Bethlehem, Pennsylvania

Publication History

  1. Published Online: 15 JUL 2005

Abstract

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 (inline image) 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:

  • mathml alt image

If the ratio inline image is 10, it means inline image is 1000 times greater than inline image. 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.

Keywords:

  • reverse osmosis;
  • nanofiltration;
  • ultrafiltration;
  • Donnan membrane cell;
  • co-ion exclusion