Journal of Biotechnology 173 (2014) 19–23 Contents lists available at ScienceDirect Journal of Biotechnology j ourna l ho me page: www.elsevier.com/locate/jbiotec A process for producing lignocellulosic flocs from NSSC spent liquor Thomas Sitter, Farshad Oveissi, Pedram Fatehi ∗ Chemical Engineering Department, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1 a r t i c l e i n f o Article history: Received 17 November 2013 Received in revised form 28 December 2013 Accepted 3 January 2014 Available online 14 January 2014 Keywords: Spent liquor Flocculation NSSC process PEI Biorefinery a b s t r a c t Presently, the spent liquor (SL) of neutral sulfite semi chemical (NSSC) pulping process is treated in the waste water system. In this work, a new process for isolating lignocelluloses from the SL of an NSSC process is proposed and the effectiveness of this process is evaluated on industrially produced SL. The results showed that under the optimal conditions of pH 6, 30 ◦ C and 15 mg/g poly ethylene imine (PEI) concentration in the SL, a maximum of 37% lignin and 37% hemicelluloses could be removed from SL. Alternatively, the dual system of poly diallyldimethyl ammonium chloride (PDADMAC) and PEI (7.5 mg/g each) was evaluated in removing lignocelluloses from the SL; and the results showed that lignin and hemicellulose removals were improved to 47% and 50%, respectively. The turbidity and chemical oxygen demand (COD) of SL, as well as the elemental analysis of generated flocs were also assessed in this work. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Neutral sulfite semi chemical (NSSC) is a semichemical pulping process that produces pulp with a yield of 60–80%, which is 10–40% higher than conventional chemical pulping processes (Malo, 1967). In this process, wood chips are treated with sodium sulfite and sodium bicarbonate and subsequently, the treated wood chips are mechanically disintegrated to produce pulp (Benjamin et al., 1969). However, the disposal or recovery of the spent liquor (SL) gen- erated in the pretreatment stage is a major environmental issue of this process. Due to the presence of lignocelluloses in the SL, it has a high oxygen demand (COD) and in some cases an odor (Malo, 1967). Current practices are to either recover the spent chemicals through ponding for example or treating it in a waste water treat- ment system (Benjamin et al., 1969). Recovery process of SL can be very expensive because SL is very dilute and thus an extensive evaporation is needed. However, the lignocelluloses can be separated from the SL via flocculation (Duarte et al., 2010; Fatehi and Ni, 2011; Graham et al., 2008; Saeed et al., 2011, 2012a,b; Li and Pelton, 1992; Strom and Stenius, 1981; Tian et al., 2010). In fact, flocculation has been applied worldwide to isolate lignocelluloses from var- ious spent liquors, and was proven to be an efficient method to recover the lignocelluloses from the pre-hydrolysis liquor (PHL) ∗ Corresponding author. Tel.: +1 807 343 8697; fax: +1 807 346 7943. E-mail address: pfatehi@lakeheadu.ca (P. Fatehi). of kraft-based dissolving pulp process (Duarte et al., 2010; Saeed et al., 2011, 2012a,b; Negro et al., 2005). A previous study showed that the addition of 0.5 mg/g poly diallyldimethyl ammonium chlo- ride (PDADMAC) to PHL caused 35 wt.% removal of lignin from PHL (Saeed et al., 2012a,b). As the SL and PHL have different composi- tions and their lignocelluloses have different properties, the results of PHL analysis cannot be applicable to the SL. One objective of this study was to investigate the application of flocculation as a means to isolate the lignocelluloses from the SL of an NSSC process. To remove lignin and hemicelluloses from PHL, different dosages of cationic polymer were required in one study, which was attributed to the altered properties of lignocelluloses in the PHL (Liu et al., 2011a,b; Saeed et al., 2012a). Chitosan and PDADMAC have been used as flocculants for various spent liquors of pulping pro- cesses (Fredheim and Christensen, 2003; Guibal and Roussy, 2007; Kekkonen et al., 2002), but the performance of chitosan depends on the pH of the process. Another objective of this research was to investigate how poly ethylenemine, PEI will affect the selectivity in removing lignocelluloses from SL. In fact, PEI was used for the first time to isolate the lignocelluloses from SL. In this paper, a process was proposed for isolating lignocel- luloses from SL and utilizing isolated lignocelluloses. At first, the application of PEI in SL was optimized under different process con- ditions. The formed flocs could be used as an alternate energy source in heat recovery or as organic filler in composites or old corrugated container board production. Subsequently, the ultimate analysis was conducted on the flocs in order to investigate the prop- erties of flocs. In the proposed process, the wasted lignocelluloses 0168-1656/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jbiotec.2014.01.006