abstract
Solutions of a pure organic solvent acidified with 1% sulfuric acid, and some of their aqueous mixtures were used for lignin extraction in the Pinus radiata sawdust delignification. Organic acid solvents including acetic, lactic and citric acids as well as non-acidic compounds such as gamma-valerolactone, 2-methyltetrahydrofuran, glycerol and ethylene glycol were studied. Crude lignin extractions yields (%) ranging between ca. 5-50% were obtained, from which ethylene glycol (33%), gamma-valerolactone (48%) and propylene carbonate (52%) showed the greatest effectiveness. The effect of added water on the lignin extraction was investigated in mixtures of an organic solvent with a variable water content (75%w/w, 50% w/w, 25%w/w and 10% w/w) where it was observed that the yield of extraction decreased with the increased water content. Moreover, the purity of extracted lignins were analyzed by spectroscopic methods (UV and IR). Kamlet-Taft solvent polarity parameters, were determined with the solvatochromic probes 4-nitroaniline, N,N-diethyl-4-nitroaniline, Nile Red and 6-propionyl-2-N,N-dimethylaminonaphthalene (PRODAN), and then correlated to lignin extraction yields to explain the influence of the solute-solvent interactions on biomass delignification. A reasonable correlation was found between the medium polarizability-dipolarity pi* and the effectiveness of the solvent mixture on the extraction of lignin wood.
keywords
DEEP EUTECTIC SOLVENTS; HYDROGEN-BOND DONOR; BIO-BASED SOLVENTS; PREFERENTIAL SOLVATION; COSOLVENT MIXTURES; STRUCTURAL-CHANGES; LIGNIN EXTRACTION; WHEAT-STRAW; GREEN; METHANOL
subject category
Biochemistry & Molecular Biology; Chemistry; Polymer Science
authors
Millan, D; Gonzalez-Turen, F; Perez-Recabarren, J; Gonzalez-Ponce, C; Rezende, MC; Lopes, AMD
our authors
André M. da Costa Lopes
External Researcheracknowledgements
M. C. Rezende and D. Millan thank to Fondecyt projects 1190045 and 11170569 respectively. Andre M. da Costa Lopes thanks his research contract funded by Fundacao para a Ciencia e Tecnologia (FCT) and project CENTRO-04-3559-FSE-000095-Centro Portugal Regional Operational Programme (Centro2020) , under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) .