Hemicellulose Recovery from Spent-Sulfite-Liquor: Lignin Removal by Adsorption to Resins for Improvement of the Ultrafiltration Process

Abstract

In this work, three polymeric resins were examined as alternatives for the separation of hemicellulose and lignin. The aim was to remove the lignin from spent-sulfite-liquor (SSL) prior to ultrafiltration, producing a hemicellulose-rich retentate with high purity, and increase the capacity of the membrane filtration. The lignin in the SSL was sulfonated; thus, two of the resins were anion exchangers and 1 was hydrophobic. The data from the equilibrium studies and adsorption kinetics were fitted to established models, and the results were interpreted based on these observations. The strongly basic anion exchanger performed best with regard to lignin removal. The adsorption followed the Sips isotherm, indicating that the process was cooperative with chemisorption as the main reaction between the adsorbate and adsorbent based on the kinetics. Regeneration of the adsorbent was also possible, wherein 100 g/L NaCl was sufficient to recover 98% of the lignin. The lignin removal had a positive effect on the ultrafiltration process, in which the flux increased by 38% and the extent of separation between the hemicellulose and lignin rose from 17% to 59%.

Enzymatic Conversion of Different Qualities of Refined Softwood Hemicellulose Recovered from Spent Sulfite Liquor

“…The UFR preparation was purified through precipitation using acetone as the antisolvent [ 16 ]; this preparation was designated as antisolvent-precipitate concentrate (AC). The AC preparation was further purified by two different polymeric resins in series [ 27 ]; the final column permeate was termed adsorption preparation (AD). The concentration and purification procedures are described in Section 3.2 .…”

“…Softwood-based SSL contains AcGGM and its degradation products, but is also rich in lignin and lignin-derived compounds such as lignosulfonates (LS) [ 25 , 26 , 27 ]. It is known that the presence of lignin results in lower enzymatic cellulose saccharification yields due to steric hindrance, non-productive binding of cellulases onto lignin, and enzyme deactivation [ 28 , 29 ].…”

Application Potential of Membrane Processes in the Concept of Lignocellulose Biorefineries

“…In allen Fa ¨llen hatten jedoch Lignin und Galactoglucomannan ein a ¨hnliches Molekulargewicht, wodurch weitere Trennverfahren zur Aufspaltung dieser Komponenten erforderlich waren. Hierzu wurde die Trennung durch Fa ¨llung mit einem Anti-Lo ¨sungsmittel [13] sowie Adsorption [14] getestet. Es wurde festgestellt, dass insbesondere die Anwendung von UF vor der Fa ¨llung mit Anti-Lo ¨sungsmittel vorteilhaft ist, weil sich dadurch der Verbrauch von Anti-Lo ¨sungsmittel verringert und so die Betriebskosten reduziert werden ko ¨nnen.…”

“…Die verbleibenden Polymerverbindungen in der Sulfitablauge sind hauptsächlich Lignosulfonate. Infolgedessen werden die meisten Membranfiltrationsprozesse in diesem Aufschlussverfahren im Wesentlichen für die Konzentration und Fraktionierung von Lignosulfonaten aus der Sulfitablauge verwendet 8.…”

“…Es wurde festgestellt, dass insbesondere die Anwendung von UF vor der Fällung mit Anti‐Lösungsmittel vorteilhaft ist, weil sich dadurch der Verbrauch von Anti‐Lösungsmittel verringert und so die Betriebskosten reduziert werden können. Mit Bezug auf die Adsorption war es vorteilhaft UF als Nachbehandlung einzusetzen, da somit die Konzentrationen in der einlaufenden Sulfitablauge geringer sind, was wiederum zu einer kleineren Adsorptionskolonne, einer geringeren Regenerationshäufigkeit und einem geringeren Regeneriermittelbedarf führt 8.…”