title: 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.
  
  
  RESULTS
  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 D(i) 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
  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.
authors.affiliation: Key Laboratory of Industrial Microbiology, Ministry of Education & Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, People's Republic of China. gaoqiang@tust.edu.cn
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.forename: Fabao
authors.initials: F
authors.lastname: Liu
authors.forename: Tongcun
authors.initials: T
authors.lastname: Zhang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Shiru
authors.initials: S
authors.lastname: Jia
authors.forename: Changyan
authors.initials: C
authors.lastname: Yu
authors.forename: Kunyu
authors.initials: K
authors.lastname: Jiang
authors.forename: Nianfa
authors.initials: N
authors.lastname: Gao
mesh_terms: D000327:Adsorption; D000465:Algorithms; D002852:Chromatography, Ion Exchange / Q000379:methods*; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry* / Q000493:pharmacokinetics; D008956:Models, Chemical; D012117:Resins, Synthetic / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D012117:Resins, Synthetic; D019344:Lactic Acid; C046797:amberlite