Anomalous osmosis

Anomalous osmosis Ion-exchange membranes, polyelectrolytes, and osmosis... 

Nondiffusible ionic species of the poly electrolyte present in the carrier membrane solution of the BAHLM should affect the anomalous osmosis in both sides in the feed-side and strip-side membranes. The disadvantage of conventional osmosis, dilution ot the product, may be obviated if not turned out to the advantage of enrichment of the product. 

Hansen RD, Anderson ML. Anomalous osmosis in dialysis of acids with anion exchange membranes. I E C Fundamentals 1967 6(4) 543-551. 

Anomalous osmosis is apt to occur in a charged membrane with low resistance to solvent flow, a high concentration of fixed charge and in a solution of electrolyte for which the counter-ions and co-ions have a large difference in mobility, such as acids and alkalis. 

M. Tasaka, Y. Kondo and M. Nagasawa, Anomalous osmosis through charged membranes, J. Phys. Chem., 1969, 73, 3181. 

E. Grim and K. Sollner, The contributions of normal and abnormal osmosis to the osmotic effects arising across charged membranes with solutions of electrolytes, J. Gen. Physiol., 1957, 40, 885 -899 M. Tasaka, Y. Kondo and M. Nagasawa, Anomalous osmosis through charged membranes, J. Phys. Chem., 1969, 73, 3181-3188. 

The osmosis described by this equation is called normal osmosis and it is observed in dilute solutions and inert (noncharged) membranes. The osmosis of electrolytes solutions through charged ionic membranes is called anomalous osmosis because in this case the solute diffusion enhances (positive anomalous osmosis) or decreases (negative anomalous osmosis) the solvent transfer. The solvent transfer through a membrane under an electric current across the system is called electro-osmosis [3]. 

Anomalous osmosis presents a similar situation. We expect a certain result, namely, the movement of a liquid in conformity with the laws of diffusion, and get instead movement in the reverse direction so again we say, anomalous osmosis. But again it is some other force, of which we are unaware, which upsets the expected situation and causes diffusion against a concentration gradient. The anomalous osmosis is in full obedience to some other force, which may be an electric potential. 

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