Design of defective MIL-100(Fe)-incorporated membranes for continuous As(V) removal via adsorptive filtration

The incorporation of MIL-100(Fe), a conventional metal–organic framework (MOF), into polymeric membranes exhibits promising traits, including high stability and a large surface area. However, agglomeration is a persistent issue that significantly reduces the number of active adsorption sites for As(V) removal. Therefore, an improved adsorptive membrane was fabricated in this work using defective MIL-100(Fe), which contains coordinatively unsaturated metal sites, to address these adsorption limitations. The best-performing membrane, designated PPSU/MILBA-6 and containing 6 wt% defective MIL-100(Fe), exhibited superior performance relative to the other membranes, with a water permeance of 18.84 L/m2․h․bar and an overall porosity of 58.54%. In batch adsorption tests, the maximum capacity of the PPSU/MILBA-6 membrane reached 20.0 mg As(V)/g at pH 7.5 with a dosage of 0.5 g/L—significantly higher than that of the membrane with pristine MIL-100(Fe), at 11.66 mg As(V)/g under identical testing conditions. This enhancement was attributed to the increased number of adsorptive sites and improved material compatibility. The kinetic profile of the PPSU/MILBA-6 membrane indicated physisorption at initial As(V) uptake, and adhered to the Freundlich Isotherm, exhibiting multilayer adsorption until saturation, owing to the presence of non-uniform active sites. Furthermore, the membrane consistently produced permeate with As(V) concentrations below 10 µg/L for 10 h, maintaining an adsorption capacity of 0.4 mg As(V)/g. This performance demonstrates its potential for real-world decontamination in compliance with the USEPA standard, while highlighting its good performance for effective removal of As(V).