Preparation and recycled simultaneous adsorption of methylene blue and Cu2+ co-pollutants over carbon layer encapsulated Fe3O4 /graphene oxide nanocomposites rich in amino and thiol groups

To find an efficient material to simultaneously remove the co-existed ionic dyes and toxic metal ions, in this paper, carbon layer encapsulated Fe3O4 /graphene oxide nanocomposites rich in amino and thiol groups (Fe3O4 @C /GO) was fabricated. With methylene blue (MB) and Cu2+ as two different models of pollutants, the effects of time, initial concentration, pH values, and adsorbent dosage on the adsorption capacity of GO/ Fe3O4 @C were conducted, respectively. A pseudo-second order rate model best simulated the kinetic adsorption process for both MB and Cu2+ among the pseudo-first order, pseudo-second order, and Weber and Morris intra-particle diffusion models. The adsorption data were better fitted with the Langmuir adsorption isotherm model than Freundlich equation for both MB and Cu2+ adsorption. The monolayer adsorption capacities analyzed from Langmuir model were 116.50 mg.g(-1) and 76.86 mg.g(-1) for MB and Cu2+, respectively. In MB-Cu2+ binary system, resulted from the smaller separation factor (SF) value of MB than Cu2+, MB had a suppression effect on Cu2+ ions binding during the simultaneous adsorption process. But for the MB simultaneous adsorption and preloading, the impact of Cu2+ ions on the MB adsorption capacity was almost negligible. Besides these important results, the easily magnetically separation and good regeneration property of Fe3O4 @C /GO further indicated a kind of stable and efficient adsorbent with great potential in sewage treatment, while being very adaptable when compared with other magnetic carbon-based adsorbents.

Automated summary

The Fe3O4@C/GO nanocomposites exhibited efficient adsorption capacities for MB and Cu2+, with the pseudo-second order rate model best simulating the kinetic adsorption process and the Langmuir adsorption isotherm model providing a better fit for the adsorption data. The presence of MB in a binary system had a suppression effect on the binding of Cu2+ ions during simultaneous adsorption, but had almost negligible impact on the adsorption capacity of MB when preloaded with Cu2+ ions.