Defect density of zirconium determines its binding sites and force to antibiotic resistance genes

Abstract

Covalent binding between phosphate and Zirconium (Zr) based nanomaterials (NMs) leads to highly selective adsorption of phosphate, and thus Zr-based NMs may provide ideal adsorbents to control antibiotic resistance genes (ARGs) containing phosphate group. This study investigated the adsorptive interactions of ARGs and Zr-based NMs, i.e., hydrous zirconium oxide (HZO), UiO-66, and defect rich UiO-66 (Dr-UiO-66). Dr-UiO-66 had a higher adsorption rate and capacity (0.87 min⁻¹ and 3.59 mg/g) compared with HZO (0.07 min⁻¹ and 0.43 mg/g), and UiO-66 (0.87 min⁻¹ and 1.67 mg/g). The results demonstrated that defection sites provided more active sites for ARGs adsorption and improved the adsorption performance, which was further proved by various characterization methods. Molecular dynamic simulations revealed that the sorption energy between ARGs and Dr-UiO-66 was lower than that between ARGs and HZO, indicating that the potential covalent binding force may formed between Dr-UiO-66 and ARGs, when each Zr lost one BDC ligand in the molecular cluster. The Dr-UiO-66 exhibited excellent adsorption and selectivity in removing ARGs, even when high concentrations of Cl⁻/NO₃^–/SO₄²⁻ ions were present. Although high concentration PO₄³⁻ (5 mM) significantly hindered the adsorption of ARGs, the ARG removal performance of Dr-UiO-66 is unlikely to be inhibited by PO₄³⁻ in real application scenarios with relatively low PO₄³⁻ (0.1 mg/L). When 0.1 g Dr-UiO-66 was used to treat 200 mL simulated wastewater containing 1 μg/mL tetM gene initially, the concentration of tetM gene in the effluent could be reduced to below detection limit of the qPCR method. The results indicated that the Dr-UiO-66 hold promise as a selective and effective adsorbent for removing ARGs from contaminated waters.