Recovery of phenols from autohydrolysis liquors of barley husks: Kinetic and equilibrium studies

The liquid stream generated during the hydrolytic fractionation of barley husks, under conditions maximizing both the solubilisation of xylooligosaccharides and the lignin soluble fraction, was extracted with ethyl acetate to selectively separate the phenolic rich fraction. Further refining of this phenolic fraction is required to achieve a phenolic enriched product which leads to an integral valorisation of the raw material. The equilibrium and kinetics of sorption process onto Sepabeads SP-700 resins of the major components (gallic acid, 3,4-dihydroxybenzaldehyde, vanillic acid, syringic acid, vanillin and p-coumaric) was studied. The adsorption kinetics was found to follow a pseudo-second order model, and equilibrium could be modelled using Langmuir and Freundlich isotherms. The GC-MS analysis of the extracts desorbed by aqueous ethanol showed a final product concentrated in bioactive lignin derived phenolic and hydroxycinnamic acids.