Utilization of waste tire derived activated carbon as CO₂ capture and photocatalyst for CO₂ conversion

The aims of this research were to prepare activated carbon (AC) impregnated with tetraethylenepentamine (TEPA) for use in carbon dioxide (CO₂) capture and to then develop the AC-TEPA sorbent with titanium dioxide (TiO₂) as a catalyst for photocatalytic reduction. The AC was impregnated with TEPA at three loading levels (2.5, 5, and 10% [w/w]) and then examined for its CO₂ adsorption capacity under an ambient temperature and atmospheric pressure. The use of 5% (w/w) TEPA-impregnated AC (AC_5T) provided the highest CO₂ adsorption capacity and long-term operation with a regeneration ability for up to 10 cycles. Then, AC_5T-doped TiO₂ (AC_5T-TiO₂) was prepared as a photocatalytic reduction catalyst, since the presence of carbon and nitrogen in AC_5T could reduce the band gap energy and so enhance the photocatalytic reduction. In addition, the CO₂-saturated AC_5T was used as a CO₂ source that could be directly converted to valuable chemicals using the AC_5T-TiO₂ catalyst under photocatalytic reduction. Products were obtained in both the liquid (methanol) and gaseous (methane, carbon monoxide, and hydrogen) phases. Accordingly, the challenge of this research was to make valuable products from CO₂ and to manage waste tires, following the circular economy concept.