Facile green synthesis of novel iron asparate (Fe-LAA) MOF for adsorptive mitigation of lead (Pb) from water

Abstract

A newly reported metal organic framework (MOF), designated as Fe-LAA, was successfully synthesized through a one-step facile and green co-precipitation method. Subsequently, Fe-LAA showed effective adsorptive ability to remove the highly toxic inorganic lead (Pb2+) ions from water. The developed MOF with amine functionalization showed enhanced surface properties which were explored in detail employing various standard analytical techniques, namely, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy and zeta potential analysis. The enhanced pore volume (vp = 0.24 cm3/g) and specific surface area (SBET > 250 m2/g) of the developed MOF compared to the non-modified structural counterpart, MIL88A (SBET: 91 m2/g, vp = 0.13 cm3/g), was successfully illustrated. The maximum Langmuir Pb uptake capacity was determined as 508.2 mg/g at 25 °C. An established mass transfer model, premised on pore-diffusion and adsorption, was utilized to analyze the adsorption kinetics and estimate the optimum effective pore diffusivity (Dp) as well as the mass transfer coefficient (kf). Furthermore, the convective and diffusive time scales (τc and τd) were evaluated to explain the transport characteristics of the solute contaminant. The adsorbent proved to be selective and reusable (over multiple cycles). The significant role of Pb groups in the MOF structure in maintaining strong electronic interaction with lead moieties was reported. Overall, the present study showcases the development and application of novel Fe-LAA MOF as an effective adsorbent for the treatment of Pb in contaminated aqueous medium.