In this study, magnetic graphene oxide freeze-dried (MGO-FD) nanocomposite was
synthesized using a simple hydrothermal method. It was applied for removal of RhB (a
cationic dye) from aqueous solutions. In order to find the optimum conditions, the effects of
some parameters such as content of GO-FD in nanocomposite, adsorbent value, pH, and
contact time on the adsorption efficiency were investigated. Pseudo-first-order and pseudosecond-order kinetics models, Langmuir and Freundlich isotherm models, and thermodynamics of adsorption were also studied. It was found that adsorption kinetics was best
described by the pseudo-second-order model and adsorption equilibrium data were well
fitted to the Langmuir isotherm model with the maximum monolayer adsorption capacity
of 126.58 mg/g. The estimated values of thermodynamics parameters such as ΔG˚, ΔH˚, and
ΔS˚ indicated that the sorption process has an endothermic and spontaneous nature. The
values of ΔG˚ approved that the adsorption of RhB on MGO-FD is physisorption. The
synthesized adsorbent with a high surface area (720.09 m2
/g) and suitable adsorption capacity (113.92 m2
/g) presents a high efficiency adsorbent in removal of cationic dyes from
water. Reusability of MGO-FD was also evaluated and results showed that the adsorption
capability of the adsorbent is not significantly changed after eight cycles and can be used as
economical adsorbent for cationic dyes.