Assessing nanofiltration and reverse osmosis for the detoxification of lignocellulosic hydrolysates

During hydrolysis of lignocellulosic materials for ethanol production, compounds toxic for fermentation are formed. Ten nanofiltration (NF) and reverse osmosis (RO) membranes with low molecular weight cut-off (150-400 g mol−1) were screened on a flat-sheet plant for their ability to separate C5 and C6 sugars from acetic acid, furfural, 5-hydroxymethyl furfural and vanillin in a model solution. RO led to the highest sugars rejection (>97%) but inhibitors transmission was low. NF membranes, especially NF270, NF- and NF245 (Dow) and DK (GE Osmonics) were found suitable for detoxification with glucose rejection >94% and inhibitors transmission >80%. At high Volume Reduction Ratio, VRR, transmission of inhibitors was still enhanced (>96% at VRR=8 and 10 bars). In these conditions, NF270 gave the highest permeate flux (20 L h−1 m−2) followed by DK, NF- and NF245. However, DK and NF- could be preferred because of lower sugar loss.