Development of porosity in combined phosphoric acid-carbon dioxide activation Original Research Article

Five activated carbons with different porosity, prepared by chemical activation of peach stones with phosphoric acid, have been further activated in a carbon dioxide gas flow at 825 °C for different periods of time to cover a wide range of burn-off. The porosity of all activated carbons was determined by adsorption of N2 (77 K), CO2 (273 K) and n-C4H10 (273 K). The main effect of gasification with carbon dioxide is similar to that described for other carbons, namely the creation and widening of existing pores, the predominance of one or another being a function of burn-off. However, since activation with phosphoric acid may produce very different pore size distributions, a common carbon dioxide activation process may produce very different effects, which range from the development of only micropores to the development of only mesopores, thus enhancing the differences among the initial chemically activated carbons.