KOH ratio effect, characterization, and kinetic modeling of methylene blue from aqueous medium using activated carbon fromThevetia peruvianashell

The adsorption of methylene blue (MB) onto activated carbon with different potassium hydroxide (KOH) ratios was studied to determine the effect of the ratio on activated carbon's removal efficiency, kinetics, and surface area. The KOHTPS-activated carbon was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, SEM-EDX, Brunauer-Emmett-Teller surface area, and pHpzc, and a quantum chemical description was calculated for the MB molecule, which yielded energies associated with HOMO (−8.43 eV), LUMO (−4.12 eV), and total energy (−27,475.76 kcal/mol). For the batch adsorption of MB, a concentration of 100 mg/L was used. The results show that adsorption followed the Freundlich isotherm as multilayer adsorption, while the kinetics indicated a 720 min equilibrium time of adsorption and a pseudo second order kinetic model. The maximum adsorption capacities for the removal of MB were 2298.08 mg g−1, 704.22 mg g−1, and 684.93 mg g−1 for KOH to TPS ratios of 1:1, 2:1, and 3:1, respectively. The surface area increased as the ratio of KOH increased, indicating that the KOH to TPS ratio of 3:1 was the best adsorbent for removal of MB with a percent removal efficiency of 97.83% and a higher surface area.