Surface functionalization of GO with MgO/MgFe2O4 binary oxides: A novel magnetic nanoadsorbent for removal of fluoride ions

In the present works, we have successfully synthesized novel magnetic MgO-MgFe2O4 nanocomposite anchored onto graphene oxide (GO) substrate (MgO-MgFe2O4/GO) and MgO-Fe2O3 nanocomposite by hydrothermal methods. The prepared GO based nanocomposites were used as efficient adsorbents for removal of fluoride ions from aqueous system. The formation, morphology, size, crystalline phases, surface area and magnetic behaviors of these prepared nanocomposites were characterized by FE-SEM, HR-TEM, XRD, FT-IR, Raman, BET and VSM analytical techniques. From XRD, confirmed that GO based nanocomposite achieved a magnetic performance by forming new spinel MgFe2O4 crystal structure instead of alpha-Fe2O3 phase. It was observed that presence of GO not only plays a significant role in the structural transformation but also enhance the surface area of the nanocomposites. Batch adsorption studies were carried out to investigate the influence of various parameters such as adsorbent dosage, contact time, pH and initial concentration of solution towards removal of fluoride ions. The maximum uptake capacity of MgO-MgFe2O4/GO for fluoride ions removal is found to be 34 mg g(-1) which is higher as compared to that of MgO-Fe2O3. From the kinetic study, it is observed that the adsorption of fluoride ions onto the adsorbent surface follows pseudo second order kinetic equation and obeys the Langmuir isotherm model. Thermodynamic study indicates that the adsorption process was the endothermic in nature. The mechanism of adsorption of fluoride onto the adsorbent surface includes electrostatic interactions, anion exchange, and inner-sphere complexation.