Modified expanded graphite/Fe3O4 composite as an adsorbent of methylene blue: Adsorption kinetics and isotherms

A magnetic expanded graphite (MEG) composite was synthesized by the explosive combustion method using black powder. Successful expanded graphite coating of iron oxide nanoparticles (Fe3O4) was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The expanded volume and specific surface area (S-BET) of the expanded graphite were 300.0 mL/g and 34.8 m(2)/g, respectively, and the crystalline particle sizes of Fe3O4 were around 100-400 nm. In addition, the Fe3O4 and MEG exhibited magnetic properties, with a magnetic saturation of 72.1 and 17.5 emu/g, respectively. The adsorption kinetics of methylene blue (MB) dye were consistent with a pseudo-second-order model (R-2 = 0.9999). The data obtained fit the Langmuir (R-2 = 0.99906) and Redlich-Peterson (R-2 = 0.99998) isotherm models, with a maximum MB adsorption capacity of 78.06 mg/g. The Redlich-Peterson isotherm equation best fit the adsorption experiment datasets examined in this study.

Automated summary

A magnetic expanded graphite (MEG) composite was successfully synthesized using explosive combustion method, with iron oxide nanoparticles (Fe3O4) coated on the expanded graphite. Both Fe3O4 and MEG exhibited magnetic properties, and the adsorption kinetics of methylene blue dye followed a pseudo-second-order model with a maximum capacity of 78.06 mg/g. The Redlich-Peterson isotherm equation was found to best fit the adsorption experiment datasets in this study.