Separation Low Concentration Lactic Acid By Adsorption

There is low concentration lactic acid in fermentation residual solution of lactic acid and amino acid. It is hard difficult to separate lactic acid from those solution because of low concentration and complicated constituents.In this thesis, low concentration lactic acid has been separated by adsorption. The macroporous adsorbent was selected to separate lactic acid. Adsorption behaviors and the selectivity were studied by using static methods, including the static equilibrium adsorption, the adsorption thermodynamics properties and the kinetics of adsorption. The good operation conditions, including adsorption, washing, desorption and regeneration, have been confirmed by dynamic adsorption methods. Then lactic acid has been separated from the isoelectric supernatant in monosodium glutamate.The macroporous adsorbent NKA- II was selected to separate lactic acid from the residual solution of fermentation. The adsorbent selectivity is good, which the selectivity coefficient (K) of lactic acid with glutamic acid, alanine acid and glucose in turn equaled to 16.19, 50.72 and 6.67. The adsorption data were correlated with Freundlich isotherm equation and the correlative coefficients (R~2) all exceeded 0.99. Characteristic parameter of this equation n>1. The thermodynamics of adsorption results showed that the process of adsorption expands heat and the change of enthalpy is small. Besides, the kinetics of adsorption behavior of NKA-II was mainly controlled by intra-particle diffusion, and it fit well into the Kannan&Sundaram intra-particle diffusion model.The dynamic adsorption experiments indicated that the best flow rate was 0.8-0.9 SV; the fitting washing condition: at first wash out 0.5 BV at 5.0 SV, then wash out 0.5 BV at 2.5 SV, at last wash out 0.3 BV at 1.0 SV; the good desorption condition: flow rate of desorption was 1.80 SV, the concentration of NaOH solution was 0.35 mol/L, the volume of desorption solution was 0.50BV.Dynamic adsorption results showed that the breakthrough volume of lactic acid and glutamic acid was different, as well as lactic acid and glucose. So macroporous adsorbent NKA-II could be employed as the sorbent to separate lactic acid, glutamic acid and glucose.The recovery rate of lactic acid from isoelectric supernatant was 78.1%～99.1% indicated by corresponding Dynamic adsorption.