Adsorption behavior of L-tryptophan on ion exchange resin

A batch method was applied to investigate the adsorption behavior and mechanisms of L-tryptophan (L-trp) on ion exchange resins. HZ-001 and JK006 were proved to be ideal adsorbents due to their large loading capacityand favorable selective adsorption for L-trp. Langmuir, Freundlich, and Dubinin-Radushkevich equations were appliedto simulate the experimental data to describe the adsorption process of L-trp onto HZ-001 and JK006. The maximumloading capacity (at pH 5.0, 30 °C), determined by the Langmuir and Dubinin-Radushkevich models, was close to eachother (833 mg/g vs. 874 mg/g) for HZ-001, while discrepant (833 mg/g vs. 935 mg/g) for JK006. Three diffusion-controlled kinetic models were utilized to analyze the results in order to identify the adsorption mechanism. The adsorptionkinetics of L-trp onto cation exchange resins was investigated under different experimental conditions, including initialsolution pH, temperature, initial L-trp concentration, and adsorbent dosage. Moreover, the diffusion process of L-trponto HZ-001 and JK006 was evaluated at different initial adsorbate concentrations. The thermodynamic parameters, obtained from the kinetic data, demonstrated that L-trp could be adsorbed spontaneously onto both resins.