Experimental investigation on recovery of bio‐based protocatechuic acid using ionic liquids

Abstract

BACKGROUND The production of protocatechuic acid (PCA) (which has significant applications in organic intermediates, chemical reagents, pharmaceuticals, dye synthesis, etc.) by fermentation is a potential replacement to the conventional petrochemical routes of carboxylic acid production. However, the extraction processes of these carboxylic acids from fermentation broths and dilute waste water using organic solvents imply additional environment hazards. Ionic liquids (ILs) have come to the focus because of their superior properties as well as environmentally friendly nature, and are being intensively used for separation processes. The equilibrium extraction efficiency for bio PCA using two imidazolium ILs – 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (bmim‐PF6) – was investigated under isothermal conditions in diluent octanol. The distribution coefficient and extraction efficiency were determined to be much greater than those obtained with traditional extractants and diluents. RESULTS This work is the first of its type to use ILs for PCA isolation. From the equilibrium extraction experiments conducted it was observed, in octanol, that the average distribution coefficients (KD) values for bmimBF4 and bmim‐PF6 were 5.3 and 5.36, respectively, with average extraction efficiencies of 83.84% and 84.08% at a lower IL concentration of 10% by volume, and the findings may be utilised to develop an extraction purification system for PCA separation from aqueous streams. Multiple stages of separation may lead to almost 100% recovery. CONCLUSION PCA was efficiently extracted from aqueous solutions using bmimBF4 and bmim‐PF6 in octanol, providing preliminary practical information and theoretical support for PCA separation, purification and recovery. © 2022 Society of Chemical Industry (SCI).