Extraction behavior of nicotinic acid and nicotinamide in ionic liquids

[Display omitted] •The extraction of nicotinamide is driven by hydrophobic interaction.•Hydrogen bonding is the main driving force for the extraction of nicotinic acid.•π–π interaction between ionic liquids and solutes enhances extraction efficiency.•The extraction of nicotinic acid and nicotinamide is affected by steric hindrance. Present work explored the potential of the use of hydrophobic ionic liquids (ILs) for the extraction of high-value products nicotinic acid (NA) and niacinamide from aqueous phase. The extraction efficiency highly depended on the chemical structures of ILs. The increase in the side chain length of the ILs leaded to the decrease of the extraction efficiency due to the steric hindrance. The non-covalent interactions, such as hydrophobic interaction, hydrogen bonding and π–π interaction were the driving forces in the extraction processes. Thermodynamic study suggested that hydrogen bonding was the main driving force for the extraction of NA, while the extraction of niacinamide was mainly driven by hydrophobic interaction. Compared with conventional solvents, ILs exhibited higher extraction efficiency. Furthermore, the ILs can be reused without losing their extraction ability.