Characterization study of char and activated carbon prepared from raw and extracted rockrose

Abstract

Using raw rockrose ( Cistus Ladaniferus, L.) and rockrose extracted into petroleum ether, the effect of extraction on the thermal behaviour and chemical-physical properties of chars and activated products was studied. Chars were prepared by heat treatment of the starting materials under dynamic and isothermal conditions over the temperature range 200–1000°C. Activations of two carbonized products, which were obtained at 600°C, was accomplished in air, CO 2, or steam at 850°C until burnoff 40%. Techniques used were thermogravimetry, gas adsorption, mercury porosimetry, density measurements and FT-IR spectroscopy. Extraction delayed the rockrose pyrolysis, as inferred from the thermal behaviour of the starting materials and by the composition and texture of the chars prepared between 200–600°C. At higher temperatures, extraction reduced the ash content of chars and mitigated the loss produced in the surface area and the microporosity. Differences in textural properties of activated carbon depended on the starting material and the activating agent, being especially significant between air and CO 2 or steam. The FT-IR spectra of the carbonized and activated products displayed absorption bands compatible with the presence in the materials of surface olefinic CC double bonds, aromatic rings, and oxygen functional groups.