Solute interactions in the nanofiltration of wood hydrolysates

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.MoV4-(01) page 1MoV4-(01) page 4

Intermolecular Interactions in the Membrane Filtration of Highly Alkaline Steeping Lye

The reuse of steeping lye is crucial for the sustainable production of viscose fibers. Steeping lye contains hemicellulose and many alkaline degradation products, such as organic acids, so that its purification can be evaluated in terms of total organic carbon removal. When considering purification by membrane filtration, intermolecular interactions between hemicellulose and organic acids can strongly affect their retention efficiency. Herein, we give more insights into the ultrafiltration and nanofiltration of steeping lye and corresponding model solutions. Furthermore, we studied the impact of total organic carbon concentration, hemicellulose concentration and sodium hydroxide concentration on the membrane performance. Hydrogen bonds between hemicellulose and certain types of hydroxy acids increased the retention of the latter. In contrast, charge based repulsion forces led to a decreased retention of a certain type of hydroxy acids. It can be clearly shown that taking intermolecular interactions into account is highly important for the description of complex multicomponent mixtures. In addition, the results can be extended to other, highly alkaline process streams with organic content, such as Kraft pulping liquors