Facile synthesis of micro and nano sized iron based metal organic frameworks for optimization of effective metronidazole removal

The widespread application of antibiotics has led to pollution of aquatic systems with long-lasting pharmaceutical residues that pose serious environmental hazards and encourage antibiotic resistance. Metronidazole (MNZ), which belongs to the class of nitroimidazoles used widely, can commonly be traced to occur in water bodies as it possesses high persistence in the environment. To address this issue, this study reports the synthesis of micro and nano sized MIL-101(Fe) metal-organic frameworks (MOFs), or mMIL-101(Fe) and nMIL-101(Fe), by solvothermal and ultrasonic-assisted solvothermal methods, respectively. Comprehensive physicochemical characterization confirmed the successful synthesis of highly porous materials, with mMIL-101(Fe) exhibiting octahedral crystals with average size 2.3 µm and nMIL-101(Fe) existing as nanoparticles with size around 78 nm. BET surface area measurements yielded outstanding values of 4102 m²/g for mMIL-101(Fe) and 2411 m²/g for nMIL-101(Fe). Adsorption performance against MNZ was systematically optimized using Response Surface Methodology (RSM). Adsorption isotherm experiments revealed a closer fit to the Langmuir model, reflecting monolayer adsorption. Notably, the maximum adsorption capacities were as high as 333 mg/g for mMIL-101(Fe) and a improving 555 mg/g for nMIL-101(Fe), compared to most reported MOF-based adsorbents. Furthermore, reusability tests revealed that there was only a 6% loss of adsorption capacity after five cycles of adsorption-desorption, reflecting the material's structural stability and reusability potential. These findings position both mMIL-101(Fe) and nMIL-101(Fe) as efficient adsorbents for the elimination of MNZ from water contamination, which hold potential applications in future advanced water treatment technologies.