Efficient separation of biofuel, lignin and alkali from black liquor by acid precipitation and ethanol extraction for valorization

Efficient separating of organic components and recovering alkali are key technical issues to realize the valorization of black liquor. Acid precipitation and ethanol extraction have been adopted to extract high-quality bio-oil and inorganic salts and to purify lignin in this study. It was found that 64.29% purified lignin with 95.16% analytical purity can be obtained, and only 0.08% ash content existed, 84.02% of the remaining organic matter can be extracted as biofuel which has better performance than the biomass-pyrolysis bio-oil, and 97.31% alkali can be recycled and reused as cooking white liquor. The indicators of wastewater are much smaller than the sewage condensate discharged in traditional alkali recovery systems such as COD, BOD5, pH, etc., and the calcium sulfate generated can further increase the added value of this technology. Compared with the traditional alkali recovery system, Acid-Ethanol extraction systems can obtain $50.14 of extra profits for dealing 1 ton of dilute black liquor, it is expected to update the traditional alkali recovery process, achieve the valorization of black liquor, and support the development of "dual carbon".