Adsorption of SO2 onto waste cork powder-derived activated carbons

Three activated carbon samples have been prepared by thermal (ACchar ), physical (with CO2, ACCO2) and chemical (with KOH, ACKOH) activation of waste cork powder. Cork was characterized by thermogravimetric, elemental and proximate analyses, and activated carbons were characterized by elemental and proximate analyses, adsorption–desorption of N2, acid/base and Boehm’s titration and FTIR (ATR) spectroscopy. A commercial activated carbon sample (ACcom) was subjected to the same characterization program for comparison purposes. Activation of cork conducted to an increase in BET surface area and pore volume in the sequence: ACchar < ACCO2 < ACKOH, getting close to those of ACcom, and to an increase in surface acidity in the sequence: ACchar < ACCO2 ACcom < ACKOH. The four adsorbents were tested in the adsorption of SO2, where ACKOH presented the highest adsorption capacity, while ACchar and ACCO2 presented similar behaviors, comparable to that of ACcom. Adsorption equilibrium was successfully fitted to Langmuir and Freundlich isotherms. Desorption experiments demonstrated how SO2 strong adsorption was favored when decreasing surface acidity.