Use of Unburned Carbon in Fly Ash as Precursor for the Development of Activated Carbons

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of carbonaceous waste products from coal combustion. The carbonaceous residue in fly ash, unburned carbon (UC), is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this paper demonstrates the potential for converting unburned carbon from coal combustion waste to activated carbons. The three parent UC samples that were examined, have surface areas between 30-40 m 2 /g. After steam activation at 850°C, the unburned carbon samples generated activated carbons with microporous structure and surface areas up to 443 m 2 /g. Despite the low particle size of the UC samples, the solid yields are relatively high, since the UC has been previously devolatilized in the combustor. The inherent porosity of the UC samples is highly mesoporous, with the mesopore volume accounting for ~ 66% of the total pore volume. The activation process promotes the development of micropores, with the micropore volume accounting for over 60% after steam treating.