Isolation of L-theanine from Tea Solution by Cation Exchange Resin in Batch and Fixed Bed Column

L-Theanine, a bioactive compound in tea, was isolated from tea solution using cation exchange resin no.732. The adsorption of L-theanine by cation exchange resin no.732 fit the Langmuir isotherm model and was a monolayer molecular interaction process. Thermodynamic studies revealed that the adsorption of L-theanine by resin no.732 was an exothermic and spontaneous physically driven process. The adsorption capacity was influenced by temperature, initial concentration, and pH. The L-theanine adsorption capacity under conditions at room temperature, pH 4.73, and initial L-theanine concentration 18 g/L was 241.731 ± 3.679 mg/g. The Thomas model was fit to describe the column adsorption data at different flow rates and initial concentrations. The L-theanine adsorbed by resin no.732 could be desorbed by 0.134 mol/L Na₂HPO₄ aqueous solution with a recovery rate of 84.96%. These findings indicate that resin no.732 was a promising material for isolating L-theanine from tea solution.