Expeditious extraction of Congo red dye using a simple mechanism from aqueous solution using green solvent

In the present work, itaconic acid (IA) and tetra butyl ammonium bromide (TBAB) based deep eutectic solvent (DES) was prepared and a simple, rapid, environmentally friendly, and efficacious liquid-liquid microextraction method using synthesized DES, was derived for water-soluble anionic azo dye, Congo red extraction from water samples. The high density (1.21-1.18 g cm-3) of IA-TBAB-based DES, showed the presence of high hydrogen bonding between its components and applicability as a solvent for extraction. The influence of dye concentration, pH, and different doses of DES on percent extraction efficiency was measured. To investigate its extraction potentiality, the partition coefficient was calculated. Under the optimum condition, the percent extraction for Congo red dye from the water sample was found to be 98.5 % at pH 2. The intermolecular interconnection between Congo red dye and DES was scrutinized to understand the extraction process. Synthesized DES manifested high viscosity (>500 cP) mPa·s indicating the substantial hydrogen bonding between the DES constituents. It was noticed that Congo Red dye molecule in zwitterionic form favored partitioning in DES, while in anionic form in water.