Flow-based recovery of acetic acid from aqueous solutions using bio-derived terpenes as extracting solvents

Abstract

The ability to recover acetic acid and related byproducts from wastewater treatment plants would unlock a sustainable source of important building block-chemicals that are currently derived from fossil fuels. We report here a two-stage flow-based procedure for the extraction and alkaline back-extraction of acetic acid from an aqueous feed solution, using geraniol or eucalyptol as bio-derived organic solvents. In the first stage, acetic acid is extracted from the feed solution into the organic solvent; and, in the second stage, acetic acid is back-extracted into a 2-M NaOHaq solution, leaving a regenerated solvent that may be used for further extractions. Recovery efficiencies of up to 51 % and 37 % were obtained using geraniol and eucalyptol, respectively. By back-extracting acetic acid into a smaller volume of NaOH than the feed solution from which it was extracted, more than threefold enhancements in acetic acid concentration were achieved with respect to the feed solution. Overall acetic acid recovery efficiencies of 57 ±1% and 46 ±2% were obtained for geraniol and eucalyptol, respectively. Both solvents were successfully used for multiple extraction/back-extraction cycles, with geraniol giving a stable concentration of back-extracted acetic acid over the course of ten cycles.