Effective adsorption of phenol from aqueous solutions on activated semi-coke

Abstract

To explore an alternative adsorbent, a type of activated semi-coke was prepared by the activation with NaOH. The adsorption ability in removing phenol from aqueous solutions was explored through the utilization of a batch adsorption process. The effects of the initial phenol concentration, the adsorbent dosage, and the contact time on the adsorption capacity of the activated semi-coke were investigated. It was shown that the adsorption reached equilibrium in 60 min and the removal efficiency increased with the corresponding increase in the initial phenol concentration, activated semi-coke dosage, and contact time. The surface structure properties of the activated semi-coke were characterized by N2 adsorption isotherms. It was found that the activated semi-coke samples were essentially macroporous and that the BET surface area of activated semi-coke was 354.21 m2 g−1. Scanning electron microscopy images indicated that the surface of the activated semi-coke possessed a high development of pores. The adsorption kinetics were investigated according to four theoretical models (pseudofirst order, pseudosecond order, intraparticle diffusion, and fractionary order), and the adsorption process was well-defined by the pseudosecond order kinetics model. The adsorption equilibrium of phenol onto the activated semi-coke was determined. Experimental data were fitted to three two-parameter models (Langmuir, Freundlich, and Temkin) and three three-parameter models (Redlich–Peterson, Sips and Toth). The analysis indicated that the experimental data of the adsorption more closely resembled the three-parameter models compared to the two-parameter models, and the Sips isotherm model was determined to be the most appropriate model for the adsorption of phenol from aqueous solutions.