Recovery of Phenolic Compounds from Switchgrass Extract

The sorption/desorption of gallic acid, a simple phenolic compound, was studied experimentally in a batch system. The motivation for this project was to provide insight into the recovery of phenolic compounds from switchgrass. Recovery of phenolic compounds could enhance the sustainability and economics of biorefining facilities. The sorption/desorption of gallic acid was shown to be qualitatively similar to that of phenolics extracted from switchgrass; so more extensive studies were made using gallic acid as a surrogate for the complex mixtures of phenolic compounds leached from switchgrass. The kinetics indicate that an approximation of equilibrium was reached within 48 h. Activated carbon was demonstrated to sorb gallic acid and phenolics from water and aqueous switchgrass leachate. The loading capacity of activated carbon for the gallic acid-water-activated carbon system increased with temperature for 20 to 60 °C. Ethanol was shown to be a preferable elution agent for desorbing gallic acid from activated carbon. Experimental observations and data from this study provide suitable design information that can be used for preliminary evaluation of conceptual designs of an activated-carbon based packed-bed process for recovery of phenolic compounds from aqueous switchgrass leachate.