Evaluation of alkali resistant nanofiltration membranes for the separation of hemicellulose from concentrated alkaline process liquors

The performance of five polymeric nanofiltration and tight ultrafiltration membranes was investigated during separation of hemicellulose from process liquors containing 200 g/l sodium hydroxide. The effect of pressure and temperature on flux and retention was determined to enable optimization of operating conditions. Retention behavior was further elucidated by calculating retention as a function of molar mass obtained from size exclusion chromatography (SEC) between 100 and 50,000 g/mol. The experimental data show that hemicellulose is almost quantitatively retained at molar masses above 1,000 g/mol. Two of the membranes exhibiting excellent overall hemicellulose retention (around 90%) are most suitable for efficient removal of hemicellulose from the process. The results emphasize the need for accurate retention data from industrial effluents and process conditions.