Purification of Polyphenols from Green Tea Leaves and Performance Prediction Using the Blend Hollow Fiber Ultrafiltration Membrane

Abstract

Hollow fiber–based ultrafiltration is used as a tool to enhance purity of polyphenols and in particular epigallocatechin gallate (EGCG), from microfiltered green tea leaves. Polysulfone-polyvinylidene fluoride (PVDF) blend was used to prepare the hollow fibers and membrane M-3 having 6-wt% PVDF in polymer solution with 30-kDa molecular weight cut off, permeability 17.7 × 10−11 m/Pa s with an average pore radius 5.3 nm, was identified as the suitable one. Increase in PVDF in spinning solution made the membrane more porous. The higher cut off membrane suffered from acute pore blocking leading to low flux recovery ratio, high flux decline ratio, and relatively lower polyphenol and EGCG purity. A transport phenomena–based model was formulated to calculate the profiles of permeate flux and concentration of polyphenols in the permeate. The model parameters were evaluated by matching the calculated data with experimental results. Permeation results indicated that 138-kPa transmembrane pressure drop and 30-l/h cross flow rate were desirable operating conditions having high permeate flux 55 l/m2 h with polyphenol purity 88% and EGCG purity 81%.