JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
Online ISSN : 1881-1299
Print ISSN : 0021-9592
Research Papers
Adsorption of Organic Acids on Weakly Basic Ion Exchanger: Equilibria
Wataru TakatsujiHiroyuki Yoshida
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JOURNAL FREE ACCESS

1997 Volume 30 Issue 3 Pages 396-405

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Abstract
The adsorption of organic acids on a commercial weakly basic resin, DIAION WA30, which has a single type of fixed functional group, appeared feasible technically. Three different organic acids, acetic acid (R′-COOH), malic acid (R″-(COOH)2) and citric acid (R″′-(COOH)3), were used in this experimental study. The adsorption isotherms depended on the way in which the organic acids dissociated in the solution, but were independent of the initial concentration of organic acids. The theoretical equations for the adsorption isotherms were derived by applying the mass action law. In an acetic acid with one carboxylic group in each molecule, the adsorption isotherm was expressed by a Langmuir-type equation. In a malic acid with two carboxylic groups, the theoretical equation for the adsorption isotherm was derived by considering that R″-COOHCOO and R″-(COO)2 ions reacted with the amino group of the weakly basic resin. When the concentration of the acid in the solution is low (pH > 4), R″-(COO)2 ion mainly contributes to adsorption, and as the concentration is high, the contribution of R″-COOHCOO becomes significant. In a citric acid with three carboxylic groups, the theoretical equation was derived by considering that R″′-(COOH)2COO, R″′-COOH(COO)2 and R″′-(COO)3 ions reacted with the resin. R″′-(COO)3 ion mainly contributes to adsorption at low concentration (pH > 5), and the contribution of R″′-COOH(COO)2 and R″′-(COOH)2COO ions become significant with increasing concentration.
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© 1997 The Society of Chemical Engineers, Japan
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