Highly efficient removal of glyphosate from water by hierarchical-pore UiO-66: Selectivity and effects of natural water particles

Abstract

The selective removal of glyphosate (GP) from aqueous environments is crucial for ensuring human health and environmental sustainability. The preparation of hierarchical-pore MOFs and the reasonable regulation of the pore size are effective strategies for achieving selective removal. In this study, we applied hierarchical-pore UiO-66 analogues (HUiO-66s) synthesized by the template technique through a mild method for the removal of GP from water. The results showed that the maximum adsorption capacity of HUiO-66s was as high as 400 mg/g, which is higher than that of most reported adsorbents. Notably, HUiO-66s showed the highest adsorption rate and distribution coefficient for GP in a multivariate system containing different organophosphorus pesticides and antibiotics, exhibiting suitable selective adsorption performance for GP. Furthermore, GP adsorption onto HUiO-66-2 (prepared from 2 mL of MOF-5 template) did not affect the presence of competing anions and humic acids. Naturally occurring particles in the water body had an enhanced (i.e., Al₂O₃, sepiolite, and montmorillonite), reduced (i.e., illite and SiO₂), or insignificant (i.e., kaolin) effect on the GP adsorption rate of HUiO-66-2. Further analysis based on the bulk adsorption results and microscopic characterisation indicated that the pore structure synergistically occurred with metal-ligand bonding, hydrogen bonding, and electrostatic interactions, which together determined the GP adsorption. Overall, the high adsorption and apparent adsorption selectivity of HUiO-66s facilitated the rapid separation and removal of GP in complex aqueous environments. Our findings provide insights into the transport and fate of MOFs and contaminants in natural aquatic systems.