The disclosure relates to methods and apparatuses for forming activated carbon from feedstock particles comprising a carbon feedstock and at least one activating agent. The feedstock particles are contacted with a plasma plume generated by the combination of RF and DC power sources. The feedstock particles may flow in a cyclonic pattern in the plasma plume for increased residence time. The carbon feedstock may be a carbon precursor material or a carbonized material. The feedstock particles are contacted with the plasma plume at a temperature and for a time sufficient to carbonize and/or activate the feedstock particles.