Nutshells as granular activated carbons: physical, chemical and adsorptiveproperties

Nutshells from seven different sources (pistachio, hazelnut, almond, black walnut, English walnut, macadamia nut, pecan) were converted to granular ac tivated carbons (GACs) by carbon dioxide activation. A portion of the GACs were oxidized with compressed air and the physical (yield, surface area, at trition), chemical (pH, surface charge) and adsorptive (organics uptake, me tal ion uptake) properties of both oxidized and non-oxidized carbons were d etermined. Differences in uptake of organics, especially of polar compounds , were found between GACs made from almond shells, the group consisting of black walnut shells, English. walnut shells and pecan shells, and macadamia nutshells. Oxidation had its greatest effects on pH, surface charge and up take of metal ions. The changes due to oxidation were found to be independe nt of carbon source material. GACs with specific properties can be produced with judicious selection of carbon precursor and oxidative treatment. (C) 2001 Society of Chemical Industry.