Thermal regeneration study of high surface area activated carbon obtained from coconut shell: Characterization and application of response surface methodology

Thermal regeneration of an activated carbon obtained from the coconut shell (AC) and saturated with methylene blue (MB) was studied using response surface methodology (RSM). Regeneration efficiency was optimized by MB adsorption capacity of regenerated activated carbon (RAC). Conditions obtained for optimal regeneration were: temperature of 635 °C, N₂ flow of 100 cm ³ min^-1 and time of 0.5 h, resulting in MB adsorption capacity of 457 mg g^-1. The characterization of the RAC was performed from the TGA, N₂ adsorption isotherms, SEM, FT-IR, XPS, Boehm method and pH_drift. The TGA analysis showed that the physisorbed MB molecules evolved during the heating, while the chemisorbed molecules become polymerized on the activated carbon. The RAC was essentially microporous and it had BET surface of 1726 m² g^-1. The chemical surface analyses showed significant changes in the functional group amount and indicating the functionalization of the RAC with nitrogen from the MB.