(493e) Separation and Recovery of Ionic Impurities From Biomass Hydrolysate by Electrodialysis/Electrodeionization

Electrodialysis (ED) is an electricity-driven membrane separation technique capable of removing ionic species from solution. Electrodeionization (EDI) is a modified version of ED that contains ion-exchange (IX) resin beads within it. EDI is superior over ED under certain conditions as the phenomenon of water splitting on the surface of the IX beads enhances the ionic conductivity of the solution. EDI is also more efficient than conventional IX column because of the in-situ regeneration of the IX resin beads under the applied electric field. ED and EDI are used primarily to produce ultra-pure water for the semiconductor and pharmaceutical industries. Researchers at Argonne National Laboratory have improvised the conventional EDI technology (loose IX resin beads) to resin wafer (RW) based EDI (RW-EDI) by developing ?IX resin wafers?, where IX resin beads are immobilized onto a porous matrix. This novel RW-EDI enables implementation of EDI to wider range of applications than the conventional EDI. Lignocellulosic biomass is one of the major sources of biofuel, which can potentially replace petrochemical based fuel, with a future goal of producing 22 billion gallon of cellulosic ethanol per year. In a typical process, the lignocellulosic biomass is subjected to an acid pretreatment step to rupture the crystalline structure and aid the downstream enzymatic hydrolysis of polysaccharides to sugars. Unfortunately, the pretreatment step generates significant amount of non-ionic (furfural, hydroxymethyl furfural, etc.) and ionic (acidic acid, etc.) impurities along with the residual sulfuric acid that inhibit the downstream processes. The existing sulfuric acid removal technique (limation) is inefficient and requires additional care for handling gypsum. The acetic acid removal techniques are also inadequate in commercial scale. We, at Argonne National Laboratory, are trying to improve the performance of various separation techniques associated with the biomass pretreatment step in order to make the cellulosic ethanol production more efficient. In this context, we have evaluated the application of ED/EDI for the removal of ionic impurities (both sulfuric and acetic acid) from biomass hydrolysate. Both ED and EDI have been used to study the separation of the acids from the synthetic hydrolysate liquor. Different process parameters, such as, flow rate, applied voltage and composition of resin-wafers have been varied to determine the optimum conditions. It has been observed that more than 99 % of the acids could be removed from hydrolysate using ED or EDI. The sugar retention was more than 95 %. Further attempt has been made to recover the sulfuric acid and acetic acid in purified form so that the sulfuric acid could be recycled and the acetic acid could be utilized in other applications.