Modeling of the separation of inhibitory components from pretreated rice straw hydrolysate by nanofiltration membranes

► Effective removal of inhibitors and concentration of sugars in rice straw hydrolysate. ► High separation factor using 150Da molecular weight cut off nanofiltration membranes. ► The Donnan steric pore flow model adequate for membrane transport characterization. ► Separation factor of 3 for acetic acid over glucose and xylose and 7 over cellobiose. ► Volume concentration ratio of 4 increased concentration of xylose, glucose, arabinose and cellobiose by 93–151%. The main objective of this work was to remove inhibitors and concentrate sugars in hydrolysates obtained from dilute acid-treated rice straw. The Donnan steric pore flow model (DSPM) was applied for membrane characterization and it captured the membrane transport adequately. The polyamide and polyethylene sulfate nanofiltration membranes of 150Da molecular weight cut-off showed a separation factor of 3 for acetic acid over glucose and xylose and 7 over cellobiose for a simulated mixture at the optimum pH of 3. A separation factor of 3 was also found for the inhibitors hydroxymethyl furfural, ferulic and vanilic acids over sugars. The concentration of rice straw acid hydrolysate by a volume concentration ratio of 4 increased the concentrations of xylose, glucose, arabinose, cellobiose and inhibitor by 100%, 104%, 93%, 151% and 3%, respectively which indicates the membrane can be used for separating the inhibitors from acid-pretreated rice straw hydrolysate while simultaneously concentrating sugars.