Metal-organic frameworks (MOFs)-based on ZIFs for glyphosate remediation in aqueous effluent: synthesis, characterization, and adsorptive performance

Abstract

Glyphosate is the most widely used herbicide worldwide. This non-selective, water-soluble organophosphorus compound can reach surface and groundwater due to its soil mobility, contributing to aquatic contamination. Chronic exposure has been linked to adverse human health effects. These concerns have increased interest in remediation techniques, with adsorption standing out for its efficiency, simplicity, and low cost. Among adsorbents, metal-organic frameworks (MOFs), particularly zeolitic imidazolate frameworks (ZIFs), are of great interest due to their high surface areas, porosity, and thermal and chemical stability. In this study, Cu, Co, and Ni-based ZIFs were synthesized using 2-methylimidazole as the ligand, to apply them in the adsorption of the herbicide glyphosate from aqueous media. Adsorption experiments showed a low influence of pH and equilibrium was reached within 8 h. The kinetics followed a pseudo-second-order model, suggesting a predominant chemisorption mechanism. The isotherms fitted well to the Langmuir model, with maximum adsorption capacities (Q_max) of 33.99, 58.49, and 64.73 mg·g⁻¹ for CuZIF, CoZIF, and NiZIF, respectively. The differences in performance were attributed to the electronic and structural properties of the metal ions, which influence the affinity toward the functional groups of glyphosate and the formation of coordination bonds. The results are comparable to those reported for widely studied MOFs, with the advantage that the synthesized materials present simple, cost-effective, and environmentally friendly synthesis routes. Therefore, the developed ZIFs demonstrate high potential for application in the remediation of glyphosate in aqueous effluents.