Investigation of methylene blue adsorption from aqueous solutions with different carbon nanocomposites

In this study, adsorption of methylene blue dye from aqueous solutions was studied using two different nanocomposite materials as graphene oxide-clay (GO-C) and graphene oxide-pumice (GO-P). The experimental studies were carried out on the effect of composition ratio, adsorption kinetics, adsorption isotherms and adsorption thermodynamics together with the effect of solution pH. The adsorption systems for both nanocomposite materials reached equilibrium within about the first 30 min, and the obtained equilibrium concentrations were 78.4 and 21.2 mg/g, respectively, for GO-C and GO-P. It has been concluded that pore diffusion is not only controlling mechanism for the diffusion of dye molecules and the chemisorption was determined as the rate-limiting step. The maximum adsorption capacities for GO-C and GO-P were determined as 89.28 and 22.57 mg/g, respectively, according to results from the Langmuir isotherm model. Thermodynamic findings revealed that the adsorption systems have an endothermic nature. Adsorption capacities significantly increased above pH 8, reaching their maximum values at pH 12 (140.81 ve 142.32 mg/g for GO-C and GO-P, respectively).