Solute interactions in the nanofiltration of wood hydrolysates

Abstract

Spent sulfite liquor derived from sulfite pulping is considered as carbon source for bio-based platform chemicals. The spent sulfite liquor containing sugars, hydroxylic acids, furan derivatives and cooking chemicals is currently predominantly combusted to generate energy and to recover the pulping chemicals. In order to improve the economic performance of the whole pulping process a partial material use of the spent sulfite liquor is desirable. The lignosulfonates can be separated by ultrafiltration and be used as concrete plasticizer or as source for phenolic-based hydrogels or performance materials. The carbohydrates and other wood degradation products can be used as energy and carbon source in a fermentation process. In order to improve the fermentation process, the amount of inhibitory compounds, such as furan derivatives and short-chain organic acids needs to be reduced. Intermolecular interactions between different molecules influence the detoxification process by means of nanofiltration. The lignosulfonate interacts with inhibitor components and increase their retention, which is unfavorable for the process efficiency. The interactions between gluconic acid and short-chain organic acids were found to increase the membrane selectivity.