Studies On Adsorption Of L-Trp And L-Phe On732Cation-exchange Resins

In this study, the adsorption equilibrium and kinetics of L-tryptophan andL-phenylalanine on732cation-exchange resin were investigated．The experiments and models were used to study the adsorption equilibrium ofL-tryptophan and L-phenylalanine. In the single-component adsorption equilibrium,the results showed that the effects of pH values on the amount of adsorption was notsignificant when the initial pH value of the feed was between3.5and6.5; theexchanging capability of the resin was reduced due to the excess of H+, NaCl, whenthe initial pH value was lower than2.0and when the temperature was25℃~40℃.The mean relative errors of L-tryptophan and L-phenylalanine predicted by theFreundlich equation were between3.64%and4.93%under different pH values andtemperatures, respectively. The parameter k of Freundlich Equation increased with theincrease of pH value and reduced with the increase of temperature; the parameter n ofFreundlich Equation reduced with the increase of pH value and increased with theincrease of temperature.In the binary amino acid mixtures adsorption equilibrium, L-phenylalaninedominated the competitive binding．The empirical extension of the Freundlich modelwas more suitable to represent the adsorption equilibrium for the above binary aminoacid mixtures than that of the Langmuir Competitive Adsorption model(LCA). Themean relative errors of L-tryptophan and L-phenylalanine predicted by the empiricalextension of the Freundlich model were3.74%and3.85%，respectively.The experiments were carried to study the process of fixed-bed adsorptionkinetics of L-tryptophan and L-phenylalanine, and the numerical simulation was usedto study the single-component adsorption kinetics. A mathematical model was built todescribe the single-component adsorption kinetics. The orthogonal collocation methodwas used to simulate the mathematical model in order to predict the breakthroughcurves. The theoretical solution and experimental data were used to verifiy thecorrectness of the model. The effects on breakthrough curves of L-tryptophan werepredicted by the model under different pH, bed height, initial concentration, flow rateand particle radius. The results showed that the model could predict sucessfully whenthe pH value was between1.5and6.5, the initial concentration was between5mmol/L and30mmol/L, the bed height was between6cm and10cm, the flow rate was between0.0054cm/s and0.0542cm/s, the resin particle radiu was between0.035cm and0.125cm. The experimental results of the binary adsorption kinetics showed thatL-phenylalanine was the weak adsorbate, its breakthrough curves had a strip-peak; itcould enhance the role of displacement with increasing the concentration ratio andbed height, while increasing entrance concentration and flow rate would weak the roleof displacement.This paper provided some fundamental information for the further study andapplication.