Separation of monosaccharides from pretreatment inhibitors by nanofiltration in lignocellulosic hydrolysate: Fouling mitigation by activated carbon adsorption

Lignocellulose pretreatment results in production of hydrolysate consisting of sugars and inhibitors. Previous reports have shown the viability of nanofiltration (NF) of lignocellulosic hydrolysate for simultaneous sugar concentration and inhibitors removal. However, the complexity of real hydrolysate results in severe membrane fouling which greatly hinders the further application of NF in treating biomass hydrolysate. In this investigation, conditioning of real rice straw hydrolysate from dilute acid pretreatment was conducted by three methods (sedimentation, microfiltration (MF) and activated carbon (AC) adsorption) in order to reduce subsequent NF membrane fouling. Results showed that the turbidity , suspended substance (SS) and particle size of SS of the hydrolysate considerably decreased after these three conditioning methods. Only AC adsorption, however, exhibited best performance in terms of increasing the volume reduction ratio (VRR) and decreasing the membrane fouling during NF filtration of rice straw hydrolysate, demonstrating the effectiveness of AC adsorption for hydrolysate conditioning. Further experiments confirmed that removal of phenolics and pigments , the two dominating foulants during NF process, by AC adsorption were most likely responsible for its superior performance compared to sedimentation and MF.