Liquid-liquid extraction (LLE) can be used for the recovery of acetic acid from black liquor prior to bioethanol fermentation. Recovery of value-added chemicals such as acetic-, formic- and lactic acid using LLE from Kraft black liquor was studied. Acetic acid and formic acid have been reported to be strong inhibitors in fermentation. The study elucidates the effect of three reaction parameters: pH (0.5~3.5), temperature (25~65 °C), and reaction time (24~48 min). Extraction performance using tri-n-octylphosphine oxide as the extractant was evaluated. The maximum acetic acid concentration achieved from hydrolyzates was 69.87% at 25°C, pH= 0.5, and 36 min. Factorial design was used to study the effects of pH, temperature, and reaction time on the maximum inhibitor extraction yield after LLE. The maximum potential extraction yield of acetic acid was 70.4% at 25.8°C, pH=0.6 and 37.2 min residence time.

Liquid-liquid extraction Black liquor Tri-n-octylphosphine oxide (TOPO) Response surface methodology (RSM)

Luoma P, Vanhanen J, Tommila P, Distributed Bio-Based Economy: Driving Growth, SITRA: Helsinki, Finland (2011).
Aresta M, Dibenedetto A, Dumeignil F, Green Process Synth, 2, 87 (2013)
Um BH, Hanley TR, Korean J. Chem. Eng., 25(5), 1094 (2008)
Zhang YHP, J. Ind. Microbiol. Biotechnol., 35, 367 (2008)
Himmel ME, Biomass Recalcitrance. Deconstructing the Plant Cell Wall for Bioenergy. Blackwell, Oxford (2008).
Rodrigues JAR, Quim. Nova, 34, 1242 (2011)
Dewulf J, Van Langenhoven H, Renewables-Based Technology. Sustainability Assessment. John Wiley & Sons, Chichester(2006).
Um BH, Bae SH, Korean J. Chem. Eng., 28(5), 1172 (2011)
Xu J, Cheng JJ, Sharma-Shivappa RR, Burns JC, Energy Fuels, 24(3), 2113 (2010)
Fengcl D, Wegener G, Wood - Chemistry, Ultrastructure, Reactions. Walter de Gruyter, Berlin (1989).
Klinke HB, Thomsen AB, Ahring BK, Appl. Microbiol. Biotechnol., 66(1), 10 (2004)
Anasthas HM, Gaikar VG, Sep. Sci. Technol., 36(12), 2623 (2001)
Wasewar KL, Yawalkar AA, Moulijn JA, Pangarkar VG, Ind. Eng. Chem. Res., 43(19), 5969 (2004)
Um BH, Friedman B, van Walsum GP, Holzforschung., 65, 51 (2011)
Rickcr NL, Michaels JN, King CL, J. Sep. Proc. Technol., 1, 36 (1979)
Senol A, Chem. Eng. Jpn., 32, 717 (1999)
Sabolova E, Schlosser S, Martak J, J. Chem. Eng. Data, 46, 735 (2001)
Heisel RW, Chem. Eng. Prog., 73, 55 (1977)
Niitsu M, Sekine T, Bull. Chem. Soc. Jpn., 51, 705 (1978)
Wardell JM, King CJ, J. Chem. Eng. Data, 23, 144 (1978)
Hano T, Matsumoto M, Ohtake T, Sasaki K, Kawano Y, J. Chem. Eng. Jpn., 23, 260 (1990)
Reisinger H, King CJ, Ind. Eng. Chem. Res., 34(3), 845 (1995)
Juang RS, Wu RT, Sep. Purif. Technol., 17(3), 225 (1999)
Al-Mudhaf HF, Hegazi MF, Abu-Shady AI, Sep. Purif. Technol., 27(1), 41 (2002)
Wisniewski M, Pierzchalska M, J. Chem. Technol. Biotechnol., 80(12), 1425 (2005)
Sluiter A, Hames B, Ruiz R, Scarlata C, Sluiter J, Templeton D, Determination of Sugars, Byproducts, and Degradation Products in Liquid Fraction Process Samples. In: Laboratory Analytical Procedure (LAP), NREL/TP-510-42623, National Renewable Energy Laboratory, Golden, CO, USA (2006).
Du BW, Sharma LN, Becker C, Chen SF, Mowery RA, van Walsum GP, Chambliss CK, Biotechnol. Bioeng., 107(3), 430 (2010)
Chen WH, Pen BL, Yu CT, Hwang WS, Bioresour. Technol., 102(3), 2916 (2011)
Kabel MA, Bos G, Zeevalking J, Voragen AGJ, Schols HA, Bioresour. Technol., 98(10), 2034 (2007)
Larsson S, Palmqvist E, Hahn-Hagerdal B, Tengborg C, Stenberg K, Zacchi G, Nilvebrant NO, Enzyme Microb. Technol., 24(3-4), 151 (1999)
Hsu TC, Guo GL, Chen WH, Hwang WS, Bioresour. Technol., 101(13), 4907 (2010)
Panagiotopoulos IA, Lignos GD, Bakker RR, Koukios EG, J. Clean Prod., 32, 45 (2012)