Application and mechanism of carrier facilitated carbohydrate extraction from aqueous solution

• Primary amines as carrier for extraction of neutral sugars from aqueous solutions.
• Organic solvents and ILs are examined with interesting differences in selectivity.
• The extraction mechanism based on a reversible chemical reaction.
• Solvent, temperature, time or concentrations have a decisive effect on selectivity.

Recovery of carbohydrates from aqueous solution represents a problem due to their large, multivalent and flexible structure and their high hydrophilicity. Organic solvents as well as alternative solvents such as ionic liquids are able to extract carbohydrates from aqueous media by the aid of primary amines. The mechanism of the extraction process has been explored by using galactose and its corresponding O-methyl galactoside. The results indicate that the mechanism is based on formation of an adduct between the aldo-structure of the monosaccharide and the primary amine to provide a hemiaminal, which is extracted into the organic phase. The extraction rate can be influenced by variation of temperature, time, and the amount of amine and depends on the structure of the carbohydrate. The selectivity can also be tuned using different types of ionic liquids. This procedure opens the possibility to recover a carbohydrate selectively from a mixture of different carbohydrates.

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