(637a) Membrane Surface Modification with Polyelectrolyte Multilayers for Ionic Liquid Recovery for Biomass Processing

Ionic liquids (ILs) have often been advertised as versatile solvents with beneficial properties such as low vapor pressure, non-toxicity and excellent solubility for otherwise recalcitrant bio-polymers. As a result of these unique properties, numerous studies have been carried out to use ILs for biomass processing.   High sugar yields during biomass hydrolysis have been reported. However, the high cost of ILs is inhibitory for their application in lignocellulosic biomass processing. Recycle and reuse of ILs are essential to be economically viable. Here we develop membrane reactors that are capable of retaining IL for reuse yet allowing permeation of small sugar molecules.

Ceramic flat sheet ultrafiltration membranes have been modified using layer-by-layer deposition of polyelectrolytes (PEL) involving poly(styrene sulfonate) / poly(allylamine hydrochloride) (PSS/PAH) or poly(styrene sulfonate) / poly(diallyldimethylammonium chloride) (PSS/PDADMAC) to tune the selectivity of these ultrafiltration membranes for rejecting charged species. Additional selectivity for rejecting of IL and allowing permeation of sugar molecules is achieved by varying the number of deposited PEL layers and by selecting an appropriate operating condition.