초록
The major goal of this work was to evaluate the ability of two commercially available nanofiltration membranes (NF) to efficiently separate a mixture of carboxylic acids while simultaneously retaining sugars in actual lignocellulosic biomass digestion liquor. The process achieved separation by high sugar rejection (>90%) and low acid rejection (0-40%), with the exception of butyric acid (100% rejection). Lower pH led to a significantly lower acetic and lactic acid rejection. The recovery of acids was further enhanced by operating at low pressure. Salt addition did not have a strong influence on acid and sugar rejection. Integrating separation with digestion recovered 86% of the acid during a 21 day digestion run, reducing acid concentration in the digestate by nearly 90% relative to a control without acid removal. These results demonstrate proof of concept for use of NF based anaerobic membrane bioreactors to recover carboxylic acids produced from the lignocellulosic carboxylate platform.