Abstract
BackgroundThe 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 FindingsIn 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° and ΔH° revealed that the adsorption process was spontaneous and exothermic. Moreover, the negative value of ΔS° reflected the decrease of solid-liquid interface randomness at the solid-liquid interface when adsorbing lactic acid on IRA-67.Conclusions/SignificanceWith 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.
Highlights
Lactic acid is a very important organic acid with a wide range of applications in the food, pharmaceutical, leather and textile industries
Information on the kinetics of lactic acid uptake by IRA-67 resin was needed for selecting optimum operating conditions for in situ removal of lactic acid from the aqueous environment
We have described the dynamic equilibrium and thermodynamic evaluation on adsorption of lactic acid by the weakly basic resin IRA-67
Summary
Lactic acid is a very important organic acid with a wide range of applications in the food, pharmaceutical, leather and textile industries. It is classified as GRAS for general-purpose food additives by the FDA of USA. Because of the properties such as mild acidic taste, nonvolatility, lack of odor and bacteriostasis, lactic acid is used as an acidulant, taste enhancer, pH regulator and preservative in the food industry. CaCO3 is one of the traditional additives for product precipitation and neutralization. It is added into lactic acid fermentation broths to neutralize the free lactic acid and to minimize product inhibition. 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
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