Thermal analysis of activated carbon obtained from residue after supercritical extraction of hops

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 m2 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.