Monday, April 30, 2007 - 3:40 PM

Comparison of membranes and resins for acetic acid removal from biomass hydrolysates

Silvio Silverio da Silva, FAENQUIL, Rod. Itajuba-Lorena, Km 74.5, Lorena,, Sao Paulo Brazil, Brazil, Ranil Wickramasinghe, Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80525, and James D. McMillan, National Renewable Energy Laboratory, 1617 Cole Boulevard, MS-3511, Golden, CO 80401-3393.

Acetic acid is a compound commonly found in hemicellulose hydrolysates. It is a weak acid that strongly influences the bioconversion of sugar containing hydrolysates. Previous studies have used anion exchange resins to remove acetic acid from different hemicellulose hydrolysates. In this study, the efficiency of an anion exchange membrane was compared to that of an anion exchange resin, for acetic acid removal from a DI water solution and an acidic hemicellulose hydrolysate prepared (neutralized and detoxified) using two different methods.

Comparing results obtained for ion exchange membranes and resins is complicated by the fact that the ion exchange membranes and resins have very different geometries. Here the performance of membranes and resins is compared using the idealized Thomas model. Two dimensionless parameters are used, the relative mass throughput and chromatographic bed number. The relative mass throughput parameter arises naturally from the Thomas solution for ion exchange. The results show that of the two ion exchange materials, the membrane exhibits better performance in terms of capacity and retention of desired sugars. In addition, acetic acid may be eluted at a higher concentration from the membrane thus leading to the possibility of more economical recovery and re-use of the acetic acid using membrane-based ion exchange.