Kinetics and thermodynamics of methylene blue adsorption onto black plum seed-based graphene oxide

The kinetics and thermodynamics of methylene blue adsorption from aqueous solution was studied using low-cost biomass graphite (CVDM) and graphene oxide (SGO) derived from black plum seed. The effects of pH in the range of 2.2-12.5, adsorbent dosage in the range of 25-100 mg and solution temperature in the range of 28.7-90 degrees C were studied. The optimum conditions were recorded at pH 4.8, dosage of 25 mg and solution temperature of 70 degrees C. The pseudo-second-order model demonstrated the best fit to experimental data (R2 -> 1 and SSE = 3.69), rapid rate constant (Ks = 0.0868 g/mg.min) and empirical adsorption capacity of 4.12 mg/g. The adsorption of methylene blue onto SGO increased with solution temperature to 70 degrees C before it decreased, suggesting a weakening of the attractive adsorbent-adsorbate forces due to collisions among methylene blue molecules.