Production of special activated carbon from lignite for environmental purposes

A treatment technique involving three sequential stages (demineralisation, activation and sulphur dispersion) was developed for the production of suitable activated carbons from Greek lignite. Demineralisation included three steps of acid treatment and samples received were characterised by X-ray diffraction (XRD). A two-stage activation procedure (pyrolysis under nitrogen, followed by activation under carbon dioxide atmosphere) was used for the production of activated samples. Sulphur impregnation of activated carbons was performed by heating with high purity elemental sulphur flakes under nitrogen flow at temperatures up to 600 °C. SEM and line scattering techniques were used to evaluate sulphur distribution in the impregnated activated carbons. Adsorption of N2 at 77 K and CO2 at 298 K was used for the characterisation of products. Sulphur impregnated activated carbon samples were proven unreactive and stable at the flue gases temperature.