Amino-Fe3O4-functionalized graphene oxide as a novel adsorbent of Methylene Blue: kinetics, equilibrium, and recyclability aspects.

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 (pHPZC) and pH effect showed that the GO-NH2-Fe3O4 pHPZC 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 (qe) and kinetic constant (kS) 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.