Pressurized fluid extraction (PFE) of valonea tannin with binary H2O-CO2 and ternary H2O-CH3OH-CO2 systems and phase equilibrium studies

In this study, the effect of binary and ternary systems, solvent/feed (S/F) ratio (20-100 w/w), time (2-3 h) and pressure (10-200 bar) were tested with subcritical and supercritical CO2 to produce valonea tannin from acorn cups. The best yield of phenolic contents (PCs) of the valonea tannin (34.73 ± 0.02 wt%) was obtained by H2O/CO2 binary system under the conditions of S/F = 100 (w/w) at 100 bar for 3 h with supercritical CO2. Phase equilibria of H2O/CH3OH/CO2 ternary system with different solvent fractions at different temperatures and pressures were also imaged in the high pressure view cell, where liquid-liquid-vapor phase behaviors were observed for all ratios of H2O and CH3OH from 60 to 100 °C and 60 to 250 bar. High tannin content isolated in a short time will decrease the waste load and provide great advantage in terms of reducing the cost of the tannin used in leather industry.