Proficiency of Graphene Oxide in Adsorption of Zn(II) Ions from Aqueous Solution

Graphene oxide proficient adsorption of metals are often affected by preparation method. Graphene oxide was prepared using atypical modified hummers method for adsorptive removal of Zn2+ from aqueous solution. The experimental data fitted into the Langmuir isotherm. The reaction was irreversible, but had a small energy of adsorption which was indicated by Freundlich isotherm model. Tempkin model and Dubinin Radushkevich revealed a physical adsorption process driven by a slow adsorptive process. The Pseudo 2nd order had the best correlation coefficient at 0.9958 while Langmuir was 0.9545. Elovich function indicated a non-spontaneous reaction, while the intra-particle diffusion was not the rate-determining step. The slow adsorption rate in pseudo 1st order correlated with the small energy of adsorption shown by Freundlich isotherm, and correlated the small boundary layer thickness shown by intra particle diffusion. All adsorptive functions showed that some other competing mechanisms were existing. XRD showed an increased number of graphene layers, d-spacing and improved crystallite size. FTIR data showed the oxygen containing groups on the graphene oxide surface. Hence, the study showed that the prepared graphene oxide proficiently adsorbed Zn2+ and affected by method of synthesis.