Mechanistic insights into MIL-101 composites for efficient arsenic removal in near-neutral waters

The development of adsorbents that combine high capacity with strong interference resistance remains a challenge for arsenic remediation in near-neutral industrial wastewater. Herein, we designed three functionalized MIL-101(Fe) composites – Si@Fe-MOF, L@Fe-MOF, and Fe/La-MOF – using silica incorporation, layered double hydroxide (LDH) assembly, and bimetallic synergy, respectively. This multi-faceted strategy aimed to overcome the inherent limitations of pristine MOFs, such as insufficient active sites. Under near-neutral conditions (pH = 7), the bimetallic Fe/La-MOF composite exhibited an exceptional adsorption capacity of 1708 mg/g for As(V), with a removal rate of 98.6%. Systematic characterization and modeling revealed that the adsorption process on all composites is governed by chemisorption. Mechanistically, the incorporated components enhance performance through distinct pathways: Si – OH groups provide additional binding sites, while La doping and Fe-La synergy create high-affinity bimetallic centers for selective arsenic complexation. This work provides a theoretical foundation and effective strategies for designing high-performance, stable adsorbents for treating arsenic in complex aquatic environments.