Adsorption Thermodynamics and Kinetics of Uridine 5′-Monophosphate on a Gel-Type Anion Exchange Resin

Abstract

The adsorption behavior of uridine 5′-monophosphate (UMP) on a gel-type anion-exchange resin SD3 at different temperatures was investigated by the batch method. The dissociation equilibrium of UMP in aqueous solution has been studied. Effects of solution pH, contact time, and initial concentrations of UMP on the adsorption have been discussed. Adsorption equilibrium data had been fitted to three different isotherms including Langmuir, Freundlich, and Sips isotherms, which have been widely used in biosorption processes, and the accuracy for all models has been evaluated by the residual-root-mean-square error. For adsorption kinetics, the adsorption rate of UMP on the resin was interpreted by the Fick model, first- and second-order kinetic models, and the adsorption process was found to be well represented by the Fick model. The solution diffusivities of UMP at different temperatures were estimated by the Wilke-Chang equation. The sorption process was found to be controlled by the intraparticle diffusion. The Fick model and Sips isotherm were chosen to simulate the concentration diffusion of UMP on SD3 resin during the adsorption process. An intraparticle two-dimensional profile of SD3 resin at 0, 1, 4, 15, and 25 min for 293.15, 303.15, and 313.15 K was shown with a satisfactory description of the adsorption process. The thermodynamic parameters such as Gibbs free energy and enthalpy and entropy changes were calculated, and the values indicated that the adsorption process of UMP on SD3 resin was spontaneous and endothermic.