Valorization of waste polyethylene terephthalate plastic into N-doped microporous carbon for CO2 capture through a one-pot synthesis.

Valorization of waste polyethylene terephthalate (PET) plastic into microporous carbon with N-doping treatment was successfully performed in a one-pot synthesis and the N-doped microporous carbon was used for CO2 capture, which can mitigate plastic pollution and climate change simultaneously. The PET-derived microporous carbon developed by KOH activation and urea treatment in a one-pot synthesis at 700 °C exhibited the highest CO2 adsorption uptake of 6.23 mmol g-1 at 0 °C and 4.58 mmol g-1 at 25 °C (1 atm). The Langmuir and pseudo second-order models displayed well-fitting relationships with equilibrium and kinetic experimental data obtained in this study. The N-doped microporous carbon showed high CO2 selectivity over N2, implying that it is feasible for treating flue gases (10% CO2 and 90% N2) at 50 °C. In addition, the CO2 uptake was not only affected by micropores but also related with nitrogen and oxygen functional groups. Compared to the porous carbon prepared by two-pot synthesis where KOH activation and urea treatment were conducted separately, the porous carbon prepared by one-pot synthesis had higher oxygen contents and higher CO2 adsorption uptake. All of findings implied that the N-doped microporous carbon was successfully developed from waste PET plastic for capturing CO2 and can play a promising role in both sustainable waste management and environmental protection.

Double-Layer Structured CO2 Adsorbent Functionalized with Modified Polyethyleneimine for High Physical and Chemical Stability.

CO2 capture using polyethyleneimine (PEI)-impregnated silica adsorbents has been receiving a lot of attention. However, the absence of physical stability (evaporation and leaching of amine) and chemical stability (urea formation) of the PEI-impregnated silica adsorbent has been generally established. Therefore, in this study, a double-layer impregnated structure, developed using modified PEI, is newly proposed to enhance the physical and chemical stabilities of the adsorbent. Epoxy-modified PEI and diepoxide-cross-linked PEI were impregnated via a dry impregnation method in the first and second layers, respectively. The physical stability of the double-layer structured adsorbent was noticeably enhanced when compared to the conventional adsorbents with a single layer. In addition to the enhanced physical stability, the result of simulated temperature swing adsorption cycles revealed that the double-layer structured adsorbent presented a high potential working capacity (3.5 mmol/g) and less urea formation under CO2-rich regeneration conditions. The enhanced physical and chemical stabilities as well as the high CO2 working capacity of the double-layer structured adsorbent were mainly attributed to the second layer consisting of diepoxide-cross-linked PEI.