Synthesis of CS-Fe₃O₄/GO nanocomposite for adsorption of heavy metal in aqueous environment

In this study, magnetic material based on graphene oxide (GO) was developed for enhanced adsorption capacity for heavy metals. The Fe₃O₄nanoparticles were combined with the GO material using a chitosan (CS) binder to obtain the CS-Fe₃O₄/GO nanocomposite. The adsorption capacity of this nanocomposite was evaluated by removing heavy metals including Ni²⁺ions. When GO was composed with Fe₃O₄and CS, the GO films were densely covered with ferromagnetic particles, which were bound and densely distributed on the GO film surface due to the interaction between GO and CS. The optimal conditions for the complexation of Ni²⁺and 4-(2-pyridyl azo)-rezoxine (PAR) are 1 ml Ni²⁺, 2 ml PAR 100 mg l^-1,pH= 6 (adjusted with 0.7 ml of the 0.1 M K₂HPO₄solution) and a complexation time of 20 min. After 50 min of adsorption, the Ni²⁺removal efficiency of the CS-Fe₃O₄/GO nanocomposite reached 81.21% and the corresponding adsorption capacity was 2.03 mg g^-1. The Ni²⁺removal process followed the first-order model and Freundlich isotherm. This process was spontaneous (ΔG^o< 0) and an exothermic process (ΔH^o= -1128.875 J·mol^-1). In addition, the factors affecting this process were investigated, including thepHsolution, the dosage of the CS-Fe₃O₄/GO nanocomposite and the initial Ni²⁺concentration. The CS-Fe₃O₄/GO nanocomposite showed a potential adsorption capacity in removing Ni²⁺at low concentrations from wastewater.