Magnetic GO/Fe3O4 for rapid malachite green (MG) removal from aqueous solutions: a reversible adsorption

Abstract

Magnetic GO/Fe₃O₄ was synthesized using co-precipitation of Fe²⁺ and Fe³⁺ composited with graphene oxide (GO) in alkaline conditions. SEM, XPS, FTIR, N₂ adsorption and VSM techniques were employed to characterize the surface peculiarities of GO/Fe₃O₄ and it was then used for removal of malachite green (MG). The key influencing factors on adsorption, such as mass ratio of GO, pH value and dosage of GO/Fe₃O₄, were investigated. The Freundlich isotherm was well fitted to the experimental data, suggesting GO/Fe₃O₄ has more than one type of reactive site. By comparing the adsorption of anionic dyes and cationic dyes onto GO/Fe₃O₄, it was concluded that GO/Fe₃O₄ could be extensively applied to take up cationic dyes mainly for electrostatic interaction. In addition, the spent GO/Fe₃O₄ was almost 100% recovered in a water bath at 80 °C. An ultraviolet-visible (UV-vis) spectrophotometer and an atom adsorption spectrophotometer (AAS) were used to determine leached GO and Fe ions discharged into the treated solutions. Low leaching showed that magnetic GO/Fe₃O₄ is a stable environmentally-friendly material.