The role of lactic acid adsorption by ion exchange chromatography

Abstract

Background: The polyacrylic resin Amberlite IRA-67 is a promising adsorbent for lactic acid extraction from aqueous solution, but little systematic research has been devoted to the separation efficiency of lactic acid under different operating conditions. Methodology/Principal Findings: In this paper, we investigated the effects of temperature, resin dose and lactic acid loading concentration on the adsorption of lactic acid by Amberlite IRA-67 in batch kinetic experiments. The obtained kinetic data followed the pseudo-second order model well and both the equilibrium and ultimate adsorption slightly decreased with the increase of the temperature at 293-323K and 42.5 g/liter lactic acid loading concentration. The adsorption was a chemically heterogeneous process with a mean free energy value of 12.18 kJ/mol. According to the Boyd_plot, the lactic acid uptake process was primarily found to be an intraparticle diffusion at a lower concentration (,50 g/liter) but a film diffusion at a higher concentration (.70 g/liter). The values of effective diffusion coefficient Di increased with temperature. By using our Equation (21), the negative values of δG°u and δH°u revealed that the adsorption process was spontaneous and exothermic. Moreover, the negative value of δS°u reflected the decrease of solid-liquid interface randomness at the solid-liquid interface when adsorbing lactic acid on IRA-67. Conclusions/Significance:With the weakly basic resin IRA-67, in situ product removal of lactic acid can be accomplished especially from an open and thermophilic fermentation system without sterilization. © 2010 Gao et al.