A rapid regeneration of methylene blue dye-loaded activated carbons with microwave heating

The present work reports an investigation for examining the impact of microwave irradiation on the regeneration of orange and mangosteen peels based activated carbons loaded with methylene blue dye. The efficacy of the regeneration study was analysed by determining the carbon yield and amount of MB adsorbed in successive adsorption–regeneration cycles. The spent activated carbons were heated in a modified conventional microwave oven at the irradiation time of 2 and 3 min. The physical properties of the regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was tested by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue as dye model compound. Equilibrium data were simulated using the Freundlich, Langmuir, Dubinin–Radushkevich and Temkin isotherm models. The findings revealed the potential to regenerate orange and mangosteen peels based activated carbons by microwave irradiation. The adsorption uptakes and carbon yield of the regenerated activated carbons could maintain at 238.89–267.91 mg/g and 75.41–76.69%, even after five adsorption–regeneration cycles.

► 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 2–3 min.
► Outline the heating phenomenon and propose mechanism.
► Good preservation of porosity structure and adsorptive properties.