Extraction of reactive dyes from aqueous solutions by halogen‐free ionic liquids

Abstract Dyes are commonly used in various industries and unfortunately many of them are discharged into water bodies, causing environmental problems. In the current study, three hydrophobic, halogen‐free ionic liquids were synthesised and their capability as extracting agents was evaluated using four reactive dyes (CI Reactive Blue 4, CI Reactive Black 5, CI Reactive Orange 16 and CI Reactive Red 2). The ionic liquids, immiscible with the aqueous phase, could extract the reactive dyes from aqueous solutions, withdrawing the same amount of weight. The effects of pH and temperature on the extraction process were also studied. Trioctylmethyl ammonium ethylenediaminetetraacetate displayed a high extraction efficiency (99%), where only 33 mg of ionic liquids extracted 50 mg of CI Reactive Blue 4. Fourier Transform–infrared spectroscopy was used to screen the interaction between the ionic liquid and CI Reactive Blue 4 during the extraction stage.