Removal of some heavy metal ions from water using novel adsorbent based on iron oxide-doped sol-gel organic-inorganic hybrid nanocomposite: Equilibrium and kinetic studies

Abstract

Anew magnetic inorganic-organic hybrid adsorbent (M-N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD)-(3-glycidoxypropyltrimethoxysilane (GPTS)) was successfully synthesized via sol-gel method upon the combination of iron oxide nanoparticles and inorganic silica framework precursors (GPTS and TSD). The newly synthesized M-TSD-GPTS adsorbent was applied for the removal of several heavy metal ions from aqueous media. It was then characterized for its structure and composition by Fourier transform infrared, energy-dispersive X-ray spectroscopy, and scanning electron microscopy analyses. The mechanism of the adsorption process onto the magnetic organic grafted silica network may be mainly described by electrostatic interactions between the negatively charged functionalities over the adsorbent and the positively charged metal ions. Therefore, it was seen that metal ion removal was strongly dependent on the pH and adsorbent dosage, which were studied to express their influences on the overall efficiency. Adsorption kinetics and isotherms were conducted, and the adsorption mechanism was tested by two simple kinetic models pseudo-first and second order, and the kinetic parameters of the models were calculated and discussed. Langmuir and Freundlich isotherms were applied as well for this purpose. Appropriate adsorption capacities were obtained for Cd 2+ (50.25 mg/g), Co 2+ (30.86 mg/g), Cr 3+ (23.25 mg/g), Ni 2+ (28.90 mg/g), Pb 2+ (69.44 mg/g), and V 3+ (30.39 mg/g). Finally, the evaluation of the adsorption capability of the newly devised magnetic adsorbent showed that this material is a good candidate for all the examined metal ions.