(105c) Multicomponent Aqueous Phase Adsorption Equilibria of Organic Acids on Ion-Exchange Resin

Thermal separation of valuable organic acids from biomass fermentation broth requires high investment cost and high energy consumption. Adsorptive separation is advantageous due to its high efficiency, high selectivity, and reduced energy requirement as compared to thermal separation. To investigate adsorptive separation of organic acids from fermentation broth, systematic aqueous phase adsorption equilibrium measurements are carried out with the unary, binary, and ternary systems of acetic acid, butyric acid, and lactic acid on a commercial ion-exchange resin at different solution concentrations and pH values at room temperature. The incorporation of physical property and thermodynamic data into process simulations is crucial for evaluation of adsorbents and improvement of separations processes. Thermodynamic modeling of the adsorption equilibrium data is performed with a newly developed generalized Langmuir (gL) isotherm model for aqueous phase adsorption equilibrium. Taking into account competitive adsorption of adsorbates, thermodynamic, and solution chemistry of organic acids in aqueous solution of different pH, the model precisely captures the unary, binary, and ternary aqueous phase adsorption equilibria experimental data. The gL isotherm representations are also compared against those with conventional Overloading model and Ideal Dilute Solution Theory. The gL isotherm model provides a thermodynamically consistent foundation for multicomponent aqueous phase adsorption equilibria of organic acids in support of subsequent process simulation, development, and design of adsorptive separation units for organic acid separation from fermentation broth.