Activated carbon from cherry stones by chemical activation: Influence of the impregnation method on porous structure

Cherry stones are utilized as a precursor for the preparation of activated carbons by chemical activation with phosphoric acid (H3PO4). The activation process typically consists of successive impregnation, carbonization, and washing stages. Here, several impregnation variables are comprehensively studied, including H3PO4 concentration, number of soaking steps, H3PO4 recycling, washing of the impregnated material, and previous semi-carbonization. The choice of a suitable impregnation methodology opens up additional possibilities for the preparation of a wide variety of activated carbons with high yields and tailored porous structures. Microporous activated carbons with specific surface areas of ∼800 m2 g−1 are produced, in which > 60% of the total pore volume is due to micropores. High surface areas of ∼1500 m2 g−1 can be also developed, with micropore volumes being a 26% of the total pore volume. Interestingly, using the same amount of H3PO4, either carbons with surface areas of 791 and 337 m2 g−1 or only one carbon with a surface area of 640 m2 g−1 can be prepared. The pore volumes range very widely between 0.07–0.55, 0.01–0.90, and 0.09–0.79 cm3 g−1 for micropores, mesopores, and macropores, respectively.