Activated Carbons from Residue after Supercritical Extraction for Removal of Nitrogen Dioxide

The aim of this study was to obtain activated carbons by physical activation of the waste left after supercritical extraction of marigold and hops, provided by the Institute of New Chemical Syntheses in Pulawy (Poland). The precursors were first subjected to carbonisation at 500oC in nitrogen atmosphere. The chars were next subjected to physical activation at 700 and 800oC in carbon dioxide atmosphere. The effect of activation temperature on the physicochemical properties of the adsorbents prepared has been tested. The carbonaceous materials were characterised by low-temperature nitrogen sorption as well as determination of the number of surface oxygen groups. The sorption properties of the chars and activated carbons obtained were characterised by nitrogen dioxide adsorption. The results have shown that activated carbons are characterised by low developed surface area varying from 2 to 413 m2/g and show alkaline character of the surface. It has been proved that appropriate choice of the activation parameters and the presence of steam have a positive effect on adsorption of nitrogen dioxide by activated carbons obtained. The highest sorption capacity toward nitrogen dioxide in wet conditions was 72.1 mg/gads, while in dry conditions it was 38.7 mg/gads. The results have also shown that future research should be aimed at the optimum choice of the temperature of activation or activating agent in order to significantly improve the textural parameters of the activated carbons.