Study of the experimental and microscopic mechanism of the removal of phenolic compounds from wastewater based on hydrophobic deep eutectic solvents

Abstract

Dephenolisation has been a key environmental concern; therefore, separating and recycling phenolic compounds from wastewater can reduce environmental harm and the consumption of resources, respectively. Herein, we selected three hydrogen bond acceptors (HBAs) and three hydrogen bond donors (HBDs) with excellent industrial prospects, which were widely sourced, and combined them as nine hydrophobic deep eutectic solvents (HDESs) to perform liquid–liquid extraction (LLE) experiments and molecular simulation studies on model wastewaters containing phenol and catechol. The preliminary screening of HDESs was carried out by conducted with quantum chemical simulations using σ-Profiles, and the microscopic mechanism of the extraction process using HDESs was analysed through molecular dynamics (MD) simulations based on radial distribution function, spatial distribution function, mean square displacement and interaction energy results. Guided by the above molecular simulation results, experimental studies on LLE using HDESs were further conducted to determine the optimal conditions of the experimental operation, including the types and ratios of HBAs and HBDs, feed ratios between the HDESs and model wastewater, and extraction temperatures. The experimental studies revealed that the extraction efficiency of octanoic acid − geraniol (molar ratio 1:3) on a 0.6 % (mass concentration) phenol and catechol model wastewater at 25℃ could reach > 96 %. Moreover, the results were consistent with that of MD simulation. The above methodologies provide a reliable basis for resolving similar problems.