Adsorption of pharmaceuticals and personal care products by deep eutectic solvents-regulated magnetic metal-organic framework adsorbents: Performance and mechanism

Abstract

The ecological and human health threats brought by emerging pollutants are increasingly serious. Development of efficient removal methods is urgent. Herein, seven deep eutectic solvents (DESs) composed by quaternary ammonium salts and lactic acid or glycolic acid were synthesized and used to regulate magnetic (Fe3O4) metal organic framework (MUiO-66-NH2) composites. The obtained nanoparticles (named as DES-MUiO-66-NH2) were used as adsorbents to adsorb pharmaceuticals and personal care products (PPCPs). Langmuir isotherm model and pseudo-second-order kinetics model were suitable to analyze the adsorption process of DES-MUiO-66-NH2 to PPCPs, indicated that the adsorption of PPCPs was chemisorption on homogeneous surface of DES-MUiO-66-NH2 adsorbents. Under the optimal conditions, the adsorption capacity of DES-MUiO-66-NH2 toward ofloxacin and mefenamic acid reached up to 97.60 and 79.22 mg/g, respectively. Mechanism exploration indicated that DES-MUiO-66-NH2 selectively adsorbed PPCPs through electrostatic interaction, chelation, π-π stacking, hydrophobic interaction and hydrogen bonding. Density functional theory proved the chelation through theoretical calculation. Selective experiments manifested that the structures of DESs directly determined the specificity of DES-MUiO-66-NH2 for different PPCPs, and the investigation of structure–activity relationship provided new ideas for designing efficient tailor-made adsorbents for PPCPs. The proposed PPCPs removal approach focused on the guiding role of DESs in selective adsorption. And this green DESs regulation idea provided more options for the synthesis of high-efficiency and functional adsorbents for emerging pollutants.