Upgrading waste tires by chemical activation for the capture of SO₂

Abstract

Waste tires have been upgraded as activated carbon by chemical activation with KOH at different KOH:tire ratios, 0:1, 0.5:1, 1:1 and 4:1, namely AC-0, AC-0.5, AC-1 and AC-4 and characterized in terms of elemental and proximate analyses, nitrogen adsorption/desorption, acid/base and Boehm titrations. An increase in activating agent:tire ratio resulted in an increase in the fixed carbon content, surface area and pore volume, and a decrease in surface basicity and sulfur content. The so-prepared materials were tested in the adsorption of SO₂, as an important pollutant from fuel combustion, using a thermogravimetric analyzer. The final adsorption capacity followed the trend AC-0 < AC-0.5 <AC-1 < AC-4, matching that of increasing surface area and pore volume, while adsorption affinity was impacted by both textural and acid/base properties. A kinetic model with statistical validation based on Ritchie's equation successfully matched the transient uptake data, where larger rate constant values were obtained for those carbons presenting higher surface basicity.