Room-temperature synthesis of MIL-100(Fe) and its adsorption performance for fluoride removal from water

A novel strategy of room-temperature synthesis of MIL-100(Fe) with organic amine as deprotonating agent was proposed. The as-prepared solid product was denoted as R-MIL-100(Fe). The material was systematically characterized via XRD , FT-IR, XPS and SEM. The effects of operation parameters such as initial fluoride concentration, reaction time, initial pH and co-existing anions on the fluoride adsorption performance of the synthesized R-MIL-100(Fe) were studied. The maximum fluoride adsorption capacity of R-MIL-100(Fe) was as high as 23.53 mg/g at 298 K in the fluoride solution. The results indicate that the adsorption process of fluorine on R-MIL-100(Fe) belongs to surface adsorption and intraparticle diffusion . An excellent fluoride adsorption performance of R-MIL-100(Fe) was observed in a wide pH range of 4–10. The co-existing anions including Cl - , NO 3 - and SO 4 2- almost had no negative effects on the adsorption performance of R-MIL-100(Fe). However, the present of CO 3 2- or HCO 3 - brought an obvious reduction of F - adsorption capacity of R-MIL-100(Fe). Thermodynamic study results illustrate that the adsorption process was an exothermic chemisorption . Chemical combination of iron and fluorine was confirmed by FT-IR and XPS. The strong combination brings the excellent F - adsorption performance of MIL-100(Fe). R-MIL-100(Fe) was successfully regenerated and recycled five cycles with an excellent regeneration ability and recyclability.