Amine-modified waste tires for CO₂ capture and resource utilization

In this study, waste tires (WTs) were chosen to prepare an adsorbent material for carbon dioxide (CO₂) capture to reduce their huge amount of waste. To improve the CO₂ selectivity, the WT powder was amine-modified using tetraethylenepentamine (TEPA) or polyethyleneimine at different loading levels [2.5, 5, 10, and 15% (w/w)]. The optimum condition to develop a high-performance CO₂ adsorbent material was found to be the use of 10% (w/w) TEPA-modified WT (WT10T) with a CO₂ flow rate of 70 mL min^-1 under ambient temperature and atmospheric pressure. Based on the kinetic study of WT10T, Avrami's model fitted well with the experimental data, suggesting both physisorption and chemisorption of the CO₂. When desorbed at 60 °C under vacuum pressure, the WT10T showed a reusability of more than 10 successive adsorption cycles. Additionally, the adsorbed CO₂ in WT10T could be directly converted to value-added chemicals or fuels, such as ethylene, methane, carbon monoxide, and hydrogen, via an electrochemical reaction. Accordingly, this study shows a challenging way on how to both utilize waste materials as adsorbents and reduce the WT level from rubber industries.