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

Abstract

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