Adsorption characteristics of malic acid from aqueous solutions by weakly basic ion-exchange chromatography

In this study, we reported the effects of temperature, malic acid loading concentration, and resin dose on malic acid adsorption by IRA-67 in batch experiments. The kinetic data well fitted the pseudo-second-order kinetic model. Both the equilibrium and ultimate adsorption slightly decreased with increased temperature from 303 to 323 K at 74.7 g/L malic acid loading concentration. The malic acid adsorption was revealed as a homogeneous adsorbent process by the Langmuir model and film diffusion process at loading concentrations of 18.2-94.5 g/L malic acid by the Boyd plot. The values of effective diffusion coefficient D-i also increased with the temperature. Based on Eq. (15), the negative values of Delta G degrees and Delta H degrees revealed that the adsorption process was spontaneous and exothermic. The negative value of Delta S degrees also indicated the decrease in the solid-liquid interface randomness at this interface when malic acid is adsorbed by IRA-67. (C) 2012 Elsevier B.V. All rights reserved.