No abstract

The adsorption of organic acids on a new weakly basic ion exchanger, highly porous polyaminated chitosan (Chitopearl CCS), which has the primary amino group of chitosan and the primary, secondary, and tertiary amino groups of poly(ethylene imine), 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. These organic acids were adsorbed on the resin by an acid/base neutralization reaction. The adsorption isotherms were independent of the initial concentrations of organic acids. The theoretical equations for the adsorption isotherms were derived by considering the dissociation of organic acids in the solution and the adsorption on each functional group and by applying the mass action law. They correlated the experimental adsorption isotherms and titration curves well. Chitopearl CCS was observed to be a feasible medium for the adsorption of organic acids. Especially in high pH region (low concentration region), Chitopearl CCS could adsorb more organic acids than a commercial ion exchanger, DIAION WA30.

The parallel transport of an organic acid by solid-phase and macropore diffusion within a porous ion exchanger was studied by measuring equilibrium isotherms and uptake curves for adsorption of acetic acid and lactic acid on a weakly basic ion exchanger, DIAION WA30. Experimental adsorption isotherms were correlated by the Langmuir equation. The Langmuir equilibrium constant of acetic acid was close to that of lactic acid, and the saturation capacity of acetic acid was about 84% that of lactic acid. Intraparticle effective diffusivity D eff was determined using the homogeneous Fickian diffusion model. The value of D eff for acetic acid was about 1.5 times lactic acid. Because D eff increased with linearly increasing bulk phase concentration C 0 , D eff was separated to the solid-phase diffusivity D S and the macropore diffusivity D P by applying the parallel diffusion model. The model agreed well with the experimental curves. The values of D S and D P for acetic acid were about 2 and 1.5 times those of lactic acid, respectively. The acetic acid and the lactic acid may be separated by the difference of the diffusion rates.

No abstract

No abstract