Comparison of activated carbon produced from natural biomass and equivalent chemical compositions

• Decomposition of biomass material strongly depends on the mineral content.
• High mineral content reduced the surface area of the activated carbon.
• Fitting with equivalent composition depends on quantity of extraneous material.
• Equivalent and calculated areas were close for waste tea based activated carbon.
• Adding cellulose and hemicellulose to the biomass can increase the surface area.

Activated carbon was prepared from natural biomass (almond shell, waste tea, tomato stems and leaves) and also from commercial lignin, cellulose and hemicellulose by the chemical activation method using concentrated phosphoric acid as the activation agent. Further activated carbon was generated by the same method using biomass equivalent mixtures of commercial lignin, cellulose and hemicellulose as the precursor. Thermogravimetric analysis of the biomass was performed and the tomato leaves showed a significantly different decomposition profile compared with the other biomass, reflecting the higher proportion of extraneous material present. The activated carbon produced from each natural biomass was characterised in terms of its surface area and pore volume. The surface area values of the activated carbon produced from the waste tea and its equivalent composition were similar. The waste tea had the lowest ash content (3.45%). Comparison of the surface area measured on the other biomass materials and their equivalent compositions, showed noticeable differences. It was concluded that extraneous components particularly mineral matter in the biomass might have a significant impact on the surface area created during the heat treatment process. In general, mesopore rich material was produced with the starting materials except when commercial lignin was the precursor. Variation of the surface area of the activated carbon between the equivalent chemical composition and calculated values using commercial composition was in the range 5.34–11.43%.