Amino-Fe 3 O 4 -functionalized graphene oxide as a novel adsorbent of Methylene Blue: kinetics, equilibrium, and recyclability aspects

Abstract

Graphene oxide (GO) was synthetized from graphite oxidation via the modified Hummers method. Afterwards, the GO was functionalized with diethylenetriamine (DETA) and FeCl₃ to obtain the novel amino-iron oxide functionalized graphene (GO-NH₂-Fe₃O₄). FTIR, XRD, SEM with EDX, and Raman spectroscopy were performed to characterize both GO and GO-NH₂-Fe₃O₄. The GO-NH₂-Fe₃O₄ was then evaluated as adsorbent of the cationic dye Methylene Blue (MB); analysis of the point of zero net charge (pH_PZC) and pH effect showed that the GO-NH₂-Fe₃O₄ pH_PZC was 8.2; hence, the MB adsorption was higher at pH 12.0. Adsorption kinetics studies indicated that the system reached the equilibrium state after 5 min, with adsorption capacity at equilibrium (q_e) and kinetic constant (k_S) of 966.39 mg g⁻¹ and 3.17∙10⁻² g mg⁻¹ min⁻¹, respectively; moreover, the pseudo-second-order model was better fitted to the experimental data. Equilibrium studies showed maximum adsorption capacity of 1047.81 mg g⁻¹; furthermore, Langmuir isotherm better fitted the adsorption. Recycling experiments showed that the GO-NH₂-Fe₃O₄ maintained the MB removal rate above 95% after 10 cycles. All the results showed sorbent high adsorption capacity and outstanding regeneration capability and evidenced the employment of novel GO-NH₂-Fe₃O₄ as a profitable adsorbent of textile dyes.