Adsorption equilibrium equation or carboxylic acids on anion-exchange resins in water

The adsorption of propionic acid and benzoic acid on anion-exchange resins was analyzed, and an adsorption equilibrium equation of carboxylic acids wa s proposed. The adsorption of carboxylic acids on the anion-exchange resins was considered to be the sum of the physical adsorption of the molecule an d the ion-exchange adsorption of the ion, which were independent of each ot her. For the physical adsorption of carboxylic acids, it was conformed to t he Freundlich equation. For the ion-exchange adsorption of carboxylate ions , the equilibrium equation corresponded well with the experimental results for wide ranges of concentration and pH. The equation contains a selectivit y coefficient S-Cl(A), for the chloride ion versus the carboxylate ion, whi ch was considered essentially a constant. The influent of the bicarbonate i on from carbon dioxide in air could also be expressed by the additional equ ilibrium equation with the selectivity coefficient S-Cl(HCO3) for the chlor ide ion versus the bicarbonate ion. Consequently, an adsorption equilibrium equation can estimate the equilibrium adsorption amounts. Even the effect of a coexisting bicarbonate ion is inconsequential when the parameters of t he Freundlich isotherm equation and the selectivity coefficients of the car boxylate ion and the bicarbonate ion in each resin are determined in advanc e. (C) 2001 Academic Press.