Adsorption of naphthalene from aqueous solution on coal-based activated carbon modified by microwave induction: Microwave power effects

• Microwave radiation was an efficient method of modifying activated carbons.
• Microwave modification enhanced the basicity and decrease oxygen groups of CAC.
• MCAC was effective and fast removing naphthalene from aqueous solution.
• Naphthalene adsorption on MCAC is a spontaneous and exothermal adsorption process.

To remove polycyclic aromatic hydrocarbons effectively, coal-based activated carbon (CAC) was produced by various microwave power modification. Original and modified CAC (MCACs) were characterized by N2 adsorption method, scanning electron microscopy, X-ray photoelectron spectroscopy, Boehm method, and point of zero charge determination. Their adsorption behavior of naphthalene was also investigated. Adsorption equilibrium isotherms, adsorption kinetics, and thermodynamics of naphthalene adsorption on CAC and MCACs were generated. Microwave modification enhanced the basic surface groups of MCACs, extended their Brunauer–Emmett–Teller surface area and pore volume, and varied their distribution of surface oxygen groups. Surface area, pore volume, and functional groups of MCACs were positively related to their naphthalene-adsorption capacity. The adsorption equilibrium of naphthalene on CAC and MCACs needed only 40 min, and this adsorption was fast. Adsorption isotherms revealed that the Freundlich model was applicable to the adsorption process. The adsorption kinetics of naphthalene onto adsorbents was described by pseudo-second-order kinetic model. Naphthalene adsorption was found to a spontaneous and exothermal adsorption process. All these results showed that microwave radiation was an efficient and rapid method of modifying activated carbons. Moreover, MCACs was a promising low-cost and fast adsorbent that can be used to remove naphthalene from aqueous solutions.

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