Intensification of formic acid from dilute aqueous solutions using menthol based hydrophobic deep eutectic solvents

Abstract

The fermentation of biomass and organic waste streams is the primary source of formic acid production. Formic acid is the hydrogen energy carrier and is used as a hydrogen storage medium in fuel cells. Sustainable production of formic acid makes the hydrogen-fuel cell entirely environmentally friendly and ensures the long-term storage of renewable energy. Therefore, green, economic, and sustainable production and recovery of formic acid are highly demanded. In this study, it was aimed to use a new generation, green, easily prepared, and designer hydrophobic deep eutectic solvents (HDES) for the removal of formic acid via reactive extraction. HDESs obtained by preparing binary mixtures of nonanoic acid, decanoic acid, dodecanoic acid (HBD), and menthol (HBA) were used as diluents; tri-n-octylamine (TOA) and Amberlite LA-2 (Amb.LA-2) were acted as extractants. Experiments were performed to investigate the effect of extractant type and concentration, initial acid concentration, and volume of the organic phase on extraction. Experimental data were presented by calculating the extraction efficiency (E%), distribution coefficient (D), and loading factor (Z). Results demonstrated that the extraction efficiency remained between 10 and 13% when performing physical extraction using M-NA, M-DA, and M-DDA, while TOA was diluted with the same HDESs reached around 90% and with Amb.LA-2 85%. The highest distribution coefficient was obtained that the organic phase consisting of TOA and M-DDA mixture was used. The efficiency of utilized HDESs was in the following order: M-DDA > M-DA > M-NA.