Microwave-assisted regeneration of activated carbon

▸ Highlight the regeneration of activated carbons by microwave heating. ▸ Evaluate the effects of microwave irradiation to the physical and chemical properties. ▸ Short regeneration time of 2–5min. ▸ Outline the heating phenomenon and propose mechanism. ▸ Good preservation of porosity structure and adsorptive properties. Microwave heating was used in the regeneration of methylene blue-loaded activated carbons produced from fibers (PFAC), empty fruit bunches (EFBAC) and shell (PSAC) of oil palm. The dye-loaded carbons were treated in a modified conventional microwave oven operated at 2450MHz and irradiation time of 2, 3 and 5min. The virgin properties of the origin and regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue (MB). Microwave irradiation preserved the pore structure, original active sites and adsorption capacity of the regenerated activated carbons. The carbon yield and the monolayer adsorption capacities for MB were maintained at 68.35–82.84% and 154.65–195.22mg/g, even after five adsorption–regeneration cycles. The findings revealed the potential of microwave heating for regeneration of spent activated carbons.