Fabrication of magnetic iron Oxide@Graphene composites for adsorption of copper ions from aqueous solutions

Liquid-phase adsorption of Cu²⁺ ions onto magnetic Fe₃O₄@graphene oxide (GO) composites, prepared by a co-precipitation approach, has been investigated. This synthesis method is capable of depositing highly crystalline Fe₃O₄ nanoparticles onto GO sheets. The adsorption temperature and the weight ratio of Fe₃O₄ nanoparticles to GO sheets are found to be crucial factors affecting the adsorption performance. The pH value of the aqueous solution has a strong influence on the adsorption capacity of Cu²⁺ ions. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) adsorption models were adopted to fit the adsorption isotherms. The deposition of magnetite enhances the equilibrium rate constant (Langmuir model) and the adsorption energy (D-R model). The analysis of thermodynamic parameters reveals that the adsorption of Cu²⁺ ions is a favorable and spontaneous process. However, a moderate density of magnetite onto GO substrate is essential for the design of Fe₃O₄@GO adsorbents for efficient removal of metal ions from an aqueous solution.