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 three-fold 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.