Amine-Functionalized MIL-101(Cr/Fe) Grafted onto Dowex Resin for Enhanced Adsorptive Removal of Malathion Insecticide from Aqueous Solutions: Insights into Metal-Center Effects and Host-Guest Interactions

Abstract

Abstract In this study, two novel metal-organic framework (MOF) composites, Amine-Functionalized MIL-101(Cr) and MIL-101(Fe) grafted onto Dowex resin, were synthesized via an in-situ solvothermal method for the highly efficient removal of Malathion insecticide from aqueous solutions. The integration of MOF nanoparticles onto the Dowex resin resulted in a significant improvement in the maximum adsorption capacity (Q m ), increasing from 88.93 mg/g in Dowex resin to 216.6 mg/g for Cr-BDC-NH₂@Dowex, and reaching an unprecedented value of 357.1 mg/g for Fe-BDC-NH₂@Dowex. Adsorption experiments were conducted to evaluate the effects of contact time and initial malathion concentration using 1 g of the adsorbent at an optimal pH of 7 and a temperature of 25 °C. The adsorption of malathion onto the amine-functionalized composites followed the Pseudo-second-order kinetic model (R 2 ≥ 0.988) and the Langmuir isotherm (R 2 ≥ 0.99), suggesting a chemisorption mechanism dominated by monolayer coverage. The small atomic radius of the Fe 3+ ion in Fe-BDC-NH₂@Dowex resulted in a coordination-strained and cracked morphology transforming the bead into a three-dimensional, sponge-like adsorbent with high adsorption capacity. This research not only introduces a novel class of adsorbents for malathion remediation but also demonstrates adsorption capacities not previously documented in the literature.