abstract
Lignin holds significant potential as a feedstock for generating valuable aromatic compounds, fuels, and functional materials. However, achieving this potential requires the development of effective dissolution methods. Previous works have demonstrated the remarkable capability of hydrotropes to enhance the aqueous solubility of lignin, an amphiphilic macromolecule. Notably, deep eutectic solvents (DESs) have exhibited hydrotropic behavior, significantly increasing the aqueous solubility of hydrophobic solutes, making them attractive options for lignin dissolution. This study aimed at exploring the influence of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) on the performance of DESs as hydrotropes for lignin dissolution, while possible dissolution mechanisms in different water/DES compositions were discussed. The capacity of six alcohols (glycerol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol) and cholinium chloride to enhance the solubility of Kraft lignin in aqueous media was investigated. A correlation between solubility enhancement and the alkyl chain length of the alcohol was observed. This was rationalized upon the competition between hydrotrope–hydrotrope and solute–hydrotrope aggregates with the latter being maximized for 1,4-butanediol. Interestingly, the hydrotropic effect of DESs on lignin solubility is well represented by the independent sum of the dissolving contributions from the corresponding HBAs and HBDs in the diluted region. Conversely, in the concentrated region, the solubility of lignin for a certain hydrotrope concentration was always found to be higher for the pure hydrotropes rather than their combined HBA/HBD counterparts.
authors
Sosa, FHB; Abranches, DO; da Costa Lopes, AM; da Costa, MC; Coutinho, JAP
our authors
André M. da Costa Lopes
External Researcher
Dinis O. Abranches
Assistant Researcher
Filipe Hobi Bordon Sosa
Junior Researcher
Groups
G4 - Renewable Materials and Circular Economy
G6 - Virtual Materials and Artificial Intelligence
Projects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
This work was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES), Finance Code 001, FAPESP [Grant 2014/21252-0], CNPq [Grants 169459/2017-9, 200627/2018-0, 310272/2017-3, 140723/2016-1, 169743/2018-7, and 312848/2023-4], Banco Santander S.A., and FAEPEX/UNICAMP and partially developed within the scope of Project CICECO-Aveiro Institute of Materials, Grants UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC). Filipe H. B. Sosa acknowledges FCT, Fundação para a Ciência e a Tecnologia, I.P. for the Researcher Contract CEECIND/07209/2022, under the Scientific Employment Stimulus, Individual Call. André M. da Costa Lopes is thankful for his research contract funded by Fundação para a Ciência 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).