Functionalized magnetic graphene oxide composites for selective toxic metal adsorption

Abstract

In this work, composites of magnetite and graphene oxide were modified with amino groups to improve chromium selectivity in a multielement solution containing Cd(II) and Cu(II) ions. The results achieved from characterization techniques such as Fourier transform infrared, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy, confirmed the effectiveness of the synthesis and evidenced different moieties able to promote metal adsorption. Comparing the unmodified composites with the silanized one, it was observed an enhancement in Cr(VI) uptake of 86% relative to Cd(II) and 23% relative to Cu(II). This effect was attributed to the hard-hard interactions of Cr(VI) with nitrogen and to the presence of NH3+ groups that improve the adsorption of chromium negative species. The metal adsorption by the composites followed the Langmuir isotherm model and a pseudo-second order kinetic, and the surface charge played an important role in the adsorption. Finally, reuse experiments showed an adsorption of approximately 100% of Cr(VI) over 5 cycles, underlining the remarkable stability of the produced amino grafted material.