Intermolecular Interactions in the Membrane Filtration of Highly Alkaline Steeping Lye

Abstract

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.

Low-Molecular-Weight Lignin Recovery with Nanofiltration in the Kraft Pulping Process

“…Compared to the other membranes that have a high lignin retention, NF090801 and SelRO MPF-36 also had relative high fluxes of 37 L/m 2 ·h and 72 L/m 2 ·h, respectively, at a TMP of 35 bar. The fluxes obtained for these two membranes are in line with the literature [ 21 , 29 ]. Thus, these two membranes were selected for concentration studies, the results of which are presented in the next section.…”