A highly efficient and recyclable zirconium-based metal organic framework for the effective removal of nanoplastics from multiple aqueous environments

Owing to the widespread dispersion and recalcitrant degradation of Nanoplastics (NPs), there is a dearth of efficient methods for removing NPs from multiple aqueous environments in sake of controlling their pollution and threats to organisms. UIO-66 is a distinctive porous metal-organic framework (MOF) material constructed from zirconium clusters and terephthalate linkers which needs to be explored for the removal of NPs from water. In this study, ethylenediamine tetramethylene phosphonic acid (EDTMP) was successfully grafted onto the surface of UIO-66, resulting in stable and efficient UIO-66-EDTMP composite. The adsorbent stability was tested in multiple mediums including water, seawater, pH gradient and organic solvents. Compared with pristine UIO66, UIO-66-EDTMP has significantly improved stability which ensures excellent NPs removal. Batch studies indicate that UIO-66-EDTMP has the capacity to adsorb 100 nm polystyrene (PS) microspheres up to 487.225 mg center dot g-1 under optimum conditions of pH= 5 and 298 K within 120 minutes. The main factors affecting the adsorption process (pH, reaction time, initial concentration, interfering ions, fulvic and humic acids) were explored and critically characterized, demonstrating successful functionalization of the UIO-66-EDTMP and efficient removal of NPs. Furthermore, kinetic models, isotherm and thermodynamic models illustrate that adsorption process follows the quasi-second-order kinetics model and endothermic in nature. The adsorption and removal mechanism involved synergistic effects of electrostatic interactions, hydrogen bonding, van der Waals forces, 1c-1c conjugation and pore capillary forces. UIO-66-EDTMP demonstrates exceptional recycling even after 10 cycles and excellent stability and adsorption capacity even in the presence of multiple aqueous samples with different pH, interfering ions, fulvic and humic acids. The immobilization and functionalization of UIO-66EDTMP are expected to function as an efficient trapping agent for NPs in multiple aqueous environments.