carbonizationactivation

Carbonization activation refers to the two-stage production of activated carbon from carbonaceous precursors by carbonization followed by activation. In carbonization, the material is heated in an inert atmosphere to drive off volatile components, leaving a carbon-rich char. Activation then develops porosity and increases surface area, producing activated carbon with a high adsorption capacity.

Activation methods include physical activation, using steam or carbon dioxide at high temperatures (commonly 800–1000°C), which selectively burns away portions of the char to create micropores and mesopores. Chemical activation involves impregnating the precursor with dehydrating agents such as potassium hydroxide (KOH), zinc chloride (ZnCl2), or phosphoric acid (H3PO4) and heating at lower temperatures (roughly 450–900°C); the activating agent is later washed away, yielding a porous carbon.

Precursor materials range from biomass (wood, nutshells, shells, agricultural waste) to coal and synthetic polymers. The choice of precursor and activation method determines pore structure, surface area, and yield. Typical surface areas for activated carbons span 500–1500 m2/g, with a predominance of micropores that enhance adsorption of gases and small molecules.

Applications are broad: gas and water purification, solvent recovery, odor control, catalysis supports, and energy storage as electrodes in supercapacitors or batteries. Factors influencing performance include carbonization temperature, activation temperature and time, impregnation ratio (for chemical activation), and moisture content of the precursor.

Environmental and safety considerations include energy use, chemical handling in chemical activation, and effluent treatment. Ongoing research aims to optimize porosity, reduce cost, and lower environmental impacts.