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

Abstract 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 °C were studied. The optimum conditions were recorded at pH 4.8, dosage of 25 mg and solution temperature of 70 °C. The pseudo-second-order model demonstrated the best fit to experimental data ( R 2 → 1 and SSE = 3.69), rapid rate constant ( K s = 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 °C before it decreased, suggesting a weakening of the attractive adsorbent-adsorbate forces due to collisions among methylene blue molecules.