Chemically grafting Cu(ii)-Schiff base complex on magnetic graphene oxide–cobalt ferrite (GO/CoFe2O4) nanocomposite for the selective and ultrafast removal of toxic anionic dyes and dichromate–chromate anions from water

Abstract

In this study, a copper(II) Schiff base complex was chemically grafted to a magnetic graphene oxide–cobalt ferrite (GO/CoFe₂O₄) composite using 3-aminopropyltriethoxysilane as a linker. The composition and microstructure of the resulting Cu(Schiff base)-GO/CoFe₂O₄ composite were confirmed using Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and surface area measurements. The adsorption ability of the composite towards different dye solutions was investigated. The results revealed that the composite adsorbed 100% of all anionic dyes, such as methyl orange (MO), bromocresol purple (BC), orange(II) (OR), titan yellow (TY), congo red (CR), and indigo carmine (IC), within short times. Furthermore, the nanocomposite could also selectively adsorb anionic dyes from cationic/anionic binary mixed dye solutions. It has also been developed as a potential adsorbent material for the efficient removal (ca. 100%) of anionic species containing toxic Cr(VI) (e.g. Cr₂O₇²⁻ and CrO₄²⁻) from aqueous solutions. The dye adsorption isotherm was well described by the Langmuir isotherm model and exhibited a maximum adsorption capacity of 129.87 mg g⁻¹. In addition, the Cu(Schiff base)-GO/CoFe₂O₄ composite exhibited a high ability to separate from the aqueous solution by an external magnetic field, and it was regenerated by several adsorption/desorption processes. Based on these results, the Cu(Schiff base)-GO/CoFe₂O₄ nanocomposite can act as a reusable effective adsorbent for the fast removal of diverse anionic dyes from aqueous solutions.