Highly Efficient and Simultaneous Removal of Cr(VI) and Imidacloprid through a Ferrocene-Modified MIL-100(Fe) Composite from an Aqueous Solution

A novel nanocomposite [Fc-MIL-100(Fe)] was constructed by combining ferrocene (Fc) with the porous structural metal-organic framework [MIL-100(Fe)]. The proposed composite material could simultaneously and efficiently remove hexavalent chromium [Cr(VI)] and imidacloprid and reduced strongly noxious Cr(VI) to weakly noxious trivalent chromium [Cr(III)]. The removal efficiencies of the composite material for Cr(VI) and imidacloprid could reach 95% after 15 h. The adsorption process was determined by kinetics, isotherms, and thermodynamics. The results demonstrated that the adsorption kinetics of Cr(VI) followed the pseudo-second-order model mainly by chemisorption; meanwhile, the adsorption of imidacloprid by the material conformed to the pseudo-first-order kinetics, which indicated that physical adsorption was the main process. Additionally, the intraparticle diffusion model revealed that the uptake of imidacloprid and Cr(VI) occurred via intraparticle diffusion at the composite material. The adsorption procedure for Cr(VI) was fitted to the Langmuir model (R2 = 0.995) via monolayer adsorption, and that for imidacloprid was fitted to the Freundlich model (R2 = 0.995) due to multilayer or heterogeneous adsorption. The thermodynamic research confirmed that the adsorption procedure was exothermic and spontaneous. Infrared spectroscopy, X-ray photoelectron spectra, and the pH effect implied that intermolecular hydrogen bonding and electrostatic interaction played a crucial role during the removal process. Fc-MIL-100(Fe) also exhibited long-term stability and satisfactory regeneration and reusability. Therefore, this method may enhance an environmentally friendly and prospective approach for concurrently removing imidacloprid and Cr(VI) from wastewater.