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 Di also increased with the temperature. Based on Eq. (15), the negative values of ΔG° and ΔH° revealed that the adsorption process was spontaneous and exothermic. The negative value of ΔS° also indicated the decrease in the solid–liquid interface randomness at this interface when malic acid is adsorbed by IRA-67.

► Adsorption characters of malic acid onto Amberlite IRA-67 resin are investigated.
► Effects of resin dose, adsorbate loading concentration and temperature determined.
► The adsorption mechanism is a homogeneous adsorbent process by the film diffusion.
► The adsorption is the exothermic and spontaneous process in nature.
► Amberlite IRA-67 resin is promising for malic acid adsorption.