Successful recovery and concentration of vanillin and syringaldehyde onto a polymeric adsorbent with ethanol/water solution

The recovery of purified fractions of vanillin and syringaldehyde (V&S) from an oxidized lignin medium has attracted considerable attention driven by the high added value of these products and the importance of lignin valorization processes in biorefineries. Polymeric resins with high specific area can be a viable option for the adsorption of aromatic compounds in polar solvents and desorption with less polar solvents for their recovery. In this work, mono-component batch and fixed bed adsorption experiments were performed with V&S on Sepabeads SP700 in ethanol:water (90:10, % V/V) solutions to obtain the respective isotherm models at 298 K and 313 K. The adsorption behaviors of V&S were described by Linear and Freundlich models. On the perspective of the real application of Sepabeads SP700 for recovery of V&S, fixed bed was first loaded with an aqueous solution of each compound and then desorption was performed with ethanol: water (90:10, % V/V). More than 84% of each compound was readily desorbed within 6 bed volumes, yielding concentration factors between 19-fold and 67-fold, relative to the inlet feed concentration. The desorption histories at the outlet of the fixed bed were successfully described by the mathematical model comprising the equilibrium isotherms and linear driving force rate equations to describe the diffusional mass transfer inside the resin. This work demonstrates that the adsorption of V&S from aqueous solution into Sepabeads SP700 bed and desorption with ethanol:water (90:10, % V/V) solution is a promising approach for the recovery of these compounds from lignin oxidation mixture. The high level of concentration achieved with this strategy and the type of solvent used is favorable for any further processing step, such as crystallization or spray drying. (C) 2016 Elsevier B.V. All rights reserved.