Enhanced PAHs adsorption using iron-modified coal-based activated carbon via microwave radiation

As an effective adsorbent, coal-based activated carbon (CAC) was modified with iron through microwave radiation to adsorb polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. The effects of iron nitrate concentration, microwave power, and microwave radiation time on CAC were investigated. The optimum modification conditions were as follows: iron nitrate concentration, 0.05 M; microwave power, 300 W; and microwave radiation time, 5 min (designated as 0.05Fe-MCAC). CAC and 0.05Fe-MCAC were characterized using scanning electron microscopy, nitrogen adsorption-desorption, surface acidity and basicity tests, and Fourier transform infrared spectroscopy. The adsorption capacities of PAHs were also determined. After modification the following phenomena occurred: pore structures developed; BET surface area increased from 686.06 to 1079.67 m(2) g(-1); the number of oxygen-containing groups decreased; and basicity was enhanced. The PAHs adsorption capacity of 0.05Fe-MCAC was higher than that of CAC. The altered texture and chemical properties of 0.05Fe-MCAC played an important role in PAHs adsorption. The pseudo-second-order models of CAC and 0.05Fe-MCAC fitted well. The PAHs adsorption of 0.05Fe-MCAC owned lower activation energy and greater stability than that of CAC. Results indicated that iron-modified CAC via microwave radiation is a promising and efficient adsorbent of PAHs from aqueous solutions. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.