Impacts of controlled microwave field irradiation on o-cresol and p-cresol adsorption capability of activated carbon.

To access the feasibility of microwave in promoting adsorbability of carbonaceous adsorbents, microwave irradiation on activated carbon (AC) was conducted at powers of 400-800 W and duration of 10 min. Accordingly, the temperature rising of AC under microwave field were studied. Moreover, the alterations in physicochemical properties of AC and impacts on cresol isomer adsorption were investigated. Results indicated that the heating curve of AC displays the initial fast temperature rising stage and the final slow stage. Additionally, the bulk temperature at irradiation terminal increases with microwave power. The temperature rising further increases the pores with a diameter range of 1.00-6.00 nm of AC; it also increases the oxygenic functional groups of AC after irradiation at 400 W and 800 W, but decreases that of AC after irradiation at 640 W. The saturation adsorption capacity of o-cresol and p-cresol on the irradiated AC rises with elevated temperature. Additionally, the cresol isomer adsorption kinetics on the irradiated AC follows the Elovich model. The above-mentioned equilibrium and kinetics suggest that the cresol isomer adsorption on the irradiated AC is dominant by chemisorption. Finally, the optimum irradiation power for o-cresol and p-cresol adsorption is 800 W and 400 W, respectively, thereby fabricating AC with developed pores and abundant oxygenic functional groups. Accordingly, the saturation adsorption capacity of o-cresol and p-cresol reaches up to 111.11 mg·g-1 and 95.97 mg·g-1, respectively. Overall, microwave irradiation is a viable option to promote cresol isomer adsorption on AC.