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

Abstract

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 p K 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 H 2SO 4, 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 H 2SO 4 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.