BET, FTIR, and RAMAN characterizations of activated carbon from waste oil fly ash

Abstract

Activated carbon (AC), a porous material with high pore volume, attracts increasing attention owing toits potential applications in several fields. The development of a porous structure in AC marginally relies on boththe treatment methods and the type of precursor. Thus far, both renewable and nonrenewable precursor sources havebeen used to synthesize AC with high surface area and pore volume. This study presents the synthesis of AC viaphysicochemical treatment of waste oil fly ash (OFA), a waste material produced from power plants. The aim was toproduce AC by adding surface pores and surface functional groups to the basal plane of OFA. Toward this objective,OFA was first chemically leached/activated with various combinations of H2 SO4 and H3PO4 , and then physicallyactivated with CO2 at 900 °C. The chemical activation step, synergistically combined with CO2 activation, resulted inan increase of 24 times the specific surface area of the OFA. The maximum increase in surface area was obtained forthe sample physicochemically treated with 100% H2 SO4 . Moreover, the spectroscopic analysis confirmed the presenceof acid functional groups after the chemical treatment step. To explore the surface heterogeneity, adsorptive potentialdistribution in terms of surface energy was also discussed as a function of the surface coverage. Following chemicalactivation, the OFA surface became heterogeneous. A major portion of the AC showed surface energy in the rangeof 40–50 erg/K, which was further increased as a result of physical activation at a higher temperature. Thus, thesynergism created by physicochemical activation resulted in a material with high surface area and pore volume, andexcellent adsorption characteristics. From the findings of this study, it was concluded that OFA is a cost-effective andenvironmentally benign precursor for the synthesis of AC.