Activated carbons have been obtained by physical activation of residue left after supercritical extraction of hops. The effect of pyrolysis temperature on the physicochemical properties of the adsorbents prepared was tested. The carbonaceous materials were characterised by low-temperature nitrogen sorption, determination of pH and the number of surface oxygen groups. The thermal properties of the chars and activated carbons were identified by thermogravimetric analysis and differential thermogravimetry. The products of thermochemical treatment of the starting hops were carbonaceous adsorbents of specific surface area ranging from 2 to 416 m 2 g-1 , showing definitely basic character of the surface and moderate thermal stability as evidenced by a considerable mass loss at about 300-400°C. The results obtained in our study have proved that residue left after supercritical extraction of hops (or similar plant materials) can be cheap, easily accessible and promising precursor for activated carbons. The results have also shown that future research should be aimed at the optimum choice of the temperature of carbonation and activation in order to significantly improve the textural parameters of the activated carbons as well as their thermal stability.
Carbonaceous adsorbents were obtained from the residue after supercritical extraction of marigold subjected to physical activation and used as nitrogen dioxide and iodine adsorbents. The effect of carbonisation and activation temperature on the textural parameters, acidbase character of the surface and sorption properties of the activated carbons was tested. The materials obtained were activated carbons of low-developed surface area varying from 2 to 206 m 2 /g, showing clearly basic character of the surface. The results proved that proper selection of the carbonisation and activation procedure of the residue after supercritical extraction of marigold permitted obtaining carbonaceous adsorbents with good capacity toward liquid as well as gas inorganic pollutants. The effectiveness of NO 2 removal was found to depend to large extent on the conditions of adsorption. The preliminary wetting of the adsorbent bed was shown to significantly increase the amount of pollutants removed.
A series of carbonaceous adsorbents was obtained by physical and chemical activation of pistachio nut shells. The effect of activation method on the textural, acid-base and adsorption properties of the materials obtained was tested. The materials prepared were characterized by iodine and methylene blue removal at room temperature. Depending on the procedure of activation, the final products were microporous activated carbons of surface area varying from 530 to 1204 m 2 /g, exhibiting diverse acidic-basic surface character. The results obtained in this study prove that a suitable choice of the activation procedure for agricultural waste materials permits production of low-cost adsorbents characterized by very high adsorption capacity towards iodine and methylene blue (1280 and 400 mg/g, respectively).
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