RECOVERY OF LIGNOSULPHONATES FROM PULPING BLACK LIQUOR VIA BIO-REACTOR FERMENTATION, REACTIVE SOLVENT EXTRACTION AND CHEMICAL PRECIPITATION
S.M. Ghoreishi and A. Nili
Department of Chemical Engineering, Isfahan University of Technology, Iran
(free)
Lignosulphonates are complex polymeric materials that are by-products of wood pulping. The discharge of Lignosulphonates in the pulp mill wastewater due to its high BOD, COD, TSS and color causes a major environmental pollution. Since there are many grades of Lignosulphonates and their commercial industrial applications are numerous, thus the objective of this research was to recover Lignosulphonates as a valuable by-product from black liquor in the Sulphite pulping processes. This recovery not only provides an economical incentive because of a by-product but also eliminates a major environmental problem for the pulping industry. The Lignosulphonates production was carried out via four processes of bioreactor fermentation, solvent extraction, reactive solvent extraction and chemical precipitation. The microorganism used in the biological fermentation was Sacchromyces Cervisiae. In the extraction process methanol, ethanol and 2-propanol were used as the solvent. But in the reactive extraction process, a solvent plus different percentages of a reactive reagent (2-propanol + 3% Cetyltrimethylammonium bromide (CTMAB), 2-propanol + 6% CTMAB and 2-propanol + 12% CTMAB) were used in order to form a chemical complex between Lignosulphonates and reactive reagent (CTMAB).
Lime was used to precipitate Lignosulphonates in the chemical precipitation process. The product quality, purity and yield obtained and also relevant parameters on Lignosulphonates production efficiency in four different processes were compared. The effectiveness of all four processes was investigated and the advantages and technological viability of each process were discussed. Consequently an innovative combined fermentationprecipitation technique was eventually developed for Lignosulphonates production at the bench scale. The results obtained in this study demonstrated that the new method of combined carbohydrates elimination via fermentation followed by lime precipitation due to economical, technological and vast industrial application of produced Lignosulphonates is preferred in contrast to the other individual four methods.
KEYWORDS Black Liquor, Extraction, Fermentation, Lignosulphonates, Microorganism, Precipitation
