Recoverable deep eutectic solvent-based aniline organic pollutant separation technology using choline salt as adsorbent

Removing aniline pollutants from organic waste-liquid rapidly and effectively has become an environmental problem owing to the high toxicity of aniline. Traditional aniline-separation methods have been limited by the complex techniques and high economic cost. In this study, green renewable Choline chloride (choline-salt, [N_1,1,1C₂OH]Cl) were used as new adsorbents for the removal of aniline by forming choline-based deep eutectic solvents (Choline-DESs) and displayed an excellent aniline removal efficiency. The mechanism of this separation technique is to remove aniline by forming a choline salt-aniline DES. The efficiency of [N_1,1,1C₂OH]Cl in removing aniline after regeneration and reuse five times was maintained. The adsorption capacity of [N_1,1,1C₂OH]Cl for aniline was observed at different temperatures (25–50 °C) and the adsorption process was spontaneous and endothermic. The amount of aniline adsorption was modelled by the adsorption isotherm and thermodynamics. The Freundlich model showed that the adsorption mechanism between aniline and choline-salt is controlled by entropy rather than a change in enthalpy. The data indicated that the Choline-DESs have much higher adsorption capacity (>278.5 mg/g) than conventional adsorbents. The high adsorption capacity, simple synthesis technique, and excellent reusability make choline-salt an attractive adsorbent for the removal of aniline from organic waste-liquid.