Sulfate and Surfactants as Boosters of Kraft Lignin Precipitation
2009 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, no 10, 5098-5104 p.Article in journal (Refereed) Published
In the spirit of the biorefinery concept, an increasing interest in further utilization of technical lignins outside the pulp mills has arisen. In this context optimization of the precipitation process to increase the yield of the lignin recovered is of great importance. The objectives of this investigation have been to study how specific salts and surfactants affect kraft lignin yield during precipitation and washing. From the results it was seen that additions of sodium sulfate increased the yield of precipitation at elevated temperatures at much lower concentrations than sodium chloride. Earlier studies of the effect of monovalent salts on kraft lignin stability have shown that specific ions either increase or decrease the fort-nation of precipitates during kraft lignin aggregation. Thus, the presented results in this study further strengthen this dependency concerning divalent anions. Regarding the role of surfactants as precipitation enhancers, cationic surfactants gave rise to fast aggregation and relatively high yields. This was found mainly due to attractive electrostatic interactions between the cationic surfactant headgroup and the oppositely charged groups on the kraft lignin macromolecules, introducing an increased degree of hydrophobicity of the lignin and thus a decreased stability. The nonionic surfactants tested affected the system very differently. In some cases the aggregation was fast and the aggregates became relatively large before settling, whereas some surfactants induced the formation of relatively dense precipitates that settled rapidly. Concerning kraft lignin precipitate washing, calcium chloride at concentrations in the millimolar region decreased the lignin losses dramatically.
Place, publisher, year, edition, pages
2009. Vol. 48, no 10, 5098-5104 p.
IdentifiersURN: urn:nbn:se:kth:diva-18428DOI: 10.1021/ie900141sISI: 000266081300053OAI: oai:DiVA.org:kth-18428DiVA: diva2:336475
QC 201005252010-08-052010-08-052011-02-03Bibliographically approved