Cation Exchange Superparamagnetic Al-Based Metal Organic Framework (Fe3O4/MIL-96(Al)) for High Efficient Removal of Pb(II) from Aqueous Solutions

A cation-exchange metal–organic framework sorbent with high adsorption capacity, active anionic surface, available adsorptive sites, good response in magnetic field and also available enclosed space between the particles for encapsulation of the analyte was in situ prepared by magnetization of a metal organic framework structure of aluminum named as MIL-96(Al). The units of magnetic MIL-96(Al) was synthesized by embedding method under hydrothermal condition and well characterized. The mechanism of sorption can be the electrostatic interaction between the anionic structures of the adsorbent with hydrated Pb2+ ions. The high percent of OH groups on the surface of Fe3O4/MIL-96(Al) led to high adsorption capacity (>301.5 mg g–1) of the sorbent for Pb2+ ions in aqueous media. The thermodynamic study of Pb2+ adsorption onto the sorbent surface demonstrated that the process was spontaneous, exothermic and physical. The face-centered central composite design was applied for optimizing the adsorption conditions, and the effective parameters were obtained as pH of 6.92, amount of sorbent of 32.4 mg and adsorption time of 25 min.