Recovery of L-(+)-lactic acid by anion exchange resin Amberlite IRA-400

Amberlite IRA-400 anion exchange resin was applied for the recovery of L-(+)-lactic acid from fermentation broth. Adsorption isotherm and breakthrough curves for the separation of L-(+)-lactic acid were obtained at pH 5.0 and 2.0, respectively. Different types of adsorption isotherms were found at pH above and below the pK(a) (3.86) of lactic acid. The isotherm was found to be a Langmuir type at pH 5.0, whereas the isotherm was type II (multilayer adsorption) at pH 2.0. At pH 5.0, the maximum adsorption capacity of the resin, q(m) and dissociation constant, K-d were 222.46 mg/g wet resin and 60.7 mg/ml, respectively. Breakthrough curve for the separation of lactic acid from fermentation broth was also obtained. The maximum adsorption capacity (197.09 mg/g wet resin) at pH 5.0 was much higher than that at pH 2.0 (106 mg/g wet resin). Proper elution and washing conditions were sought by using H2SO4, methanol, ammonia or their mixtures as eluant. When column separation was performed at pH 5.0 by using 50% (v/v) methanol as washing solvent and 1.0 M H2SO4 as eluant, the total yield was 86.21%. However, the total yield was 92.11% when the column separation was performed at pH 2.0 and water was used as eluant. (C) 2002 Elsevier Science B.V. All rights reserved.