Facile synthesis of MIL-100 metal-organic framework via heatless technique for the adsorptive treatment of cationic and anionic pollutants

Abstract

The facile synthesis of an iron-based metal-organic framework, MIL-100(Fe) has been successfully conducted via a heatless water-based technique. The unique features have been evaluated with respect to the X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis, Fourier transform infrared spectroscopy, and zero point of charge measurement. The adsorptive potential was examined using the cationic (methylene blue, MB) and anionic (naproxen, NPX) water pollutants. The synthesized MIL-100(Fe) sample, MIL-100(FeSO4), owned a crystalline microporous-mesoporous structure, with a large BET surface area of 1984 m2/g and total pore volume of 1.096 cm3/g. The equilibrium data best conformed to the Langmuir-Freundlich isotherm and pseudo-second order kinetic model, with the maximum adsorption capacity for MB and NPX of 568.1 mg/g and 148.8 mg/g, respectively. Thermodynamic analysis revealed the favorable energetics (ΔG 0), endothermic (ΔH > 0 for MB) and exothermic nature (ΔH < 0 for NPX) of the adsorption process. Negligible degradation of the adsorptive performance was recorded under high ionic strength solutions and simulated wastewaters. MIL-100(FeSO4) demonstrated great regenerative potential by ethanol stripping for at least 5 regeneration cycles. The present findings provide an invaluable insight into the green synthesis technique of MIL-100(Fe), with high upscaling prospects. Imparted with different surface anionicity and electrically neutral functional sites, MIL-100(FeSO4) has emerged to be a potent adsorbent for the successful treatment of both cationic and anionic water pollutants, even under high-strength water samples with complex water matrices.

Keywords

• Adsorption
• Dye
• Mechanism
• MIL-100
• MOF
• Pharmaceutical