Adsorption of Tea Polyphenols using Microporous Starch: A Study of Kinetics, Equilibrium and Thermodynamics

Microporous starch (MPS) granules were formed by the partial hydrolysis of starch using α-amylase and glucoamylase. Due to its biodegradability and safety, MPS was employed to adsorb tea polyphenols (TPS) based on their microporous characteristics. The influences of solution pH, time, initial concentration and temperature on the adsorptive capacity were investigated. The adsorption kinetics data conformed to the pseudo second-order kinetics model, and the equilibrium adsorption data were well described by the Langmuir isotherm model. According to the fitting of the adsorption isotherm formula, the maximum adsorption capacity of TPS onto MPS at pH 6.7 and T = 293 K was approximately 63.1 mg/g. The thermodynamic parameters suggested that the adsorption of TPS onto MPS was spontaneous and exothermic. Fourier transform infrared (FT-IR) analysis and the thermodynamics data were consistent with a physical adsorption mechanism. In addition, MPS-loaded TPS had better stability during long-term storage at ambient temperature.