Human activities have greatly contributed to the rise in CO₂ concentrations, making carbon capture and storage (CCS) technology an essential method for reducing CO₂ emissions. Solid amine adsorbents are vital materials for the future of CCS technologies, known for their high selectivity, excellent adsorption capacity, and low regeneration energy demands. However, their widespread use is still limited due to high production costs and limited cyclic stability.

Figure 1. The strategy of in-situ utilization of coal fly ash from coal-fired power plants for CO₂ capture, utilization, and storage (CCUS)

Professor Zuotai Zhang’s research team from the School of Environmental Science and Engineering at the Southern University of Science and Technology (SUSTech) has introduced a groundbreaking strategy that employs coal fly ash, a byproduct of coal-fired power plants, as a precursor material for synthesizing solid amine adsorbents supported by AlOOH (denoted as PEI@AlOOH). These adsorbents not only exhibit superior CO₂ capture performance during the flue gas CO₂ capture process but also contribute to a diminished carbon footprint and reduced overall capture costs.

Their paper, titled “Transforming coal fly ash into climate solutions: AlOOH-supported solid amine adsorbents for cost-effective and ultranegative CO₂ emissions,” has been published in Environmental Science & Technology.

The researchers successfully synthesized porous AlOOH materials by extracting NaAlO₂ from coal fly ash. This material is characterized by a rich pore structure, interlayer water, and surface hydroxyl groups. Utilizing this material as a support, they subsequently loaded polyethyleneimine (PEI) to prepare the PEI@AlOOH adsorbent.

Under simulated coal-fired flue gas conditions, the adsorbent demonstrated a CO₂ adsorption capacity of 178 mg/g. After 30 cycles at 150 °C in a CO₂ regeneration atmosphere, the CO₂ uptake of PEI@AlOOH showed only a 4.11% decline. This remarkable stability is attributed to the abundant interlayer water and surface hydroxyl groups within the AlOOH support, which effectively inhibit the formation of urea at elevated temperatures, thereby significantly enhancing the adsorbent’s cyclic stability.

Figure 2. The CO₂ adsorption performance and cyclic stability of PEI@AlOOH

Through an in-depth life cycle assessment and economic analysis, the team determined that the carbon footprint of the PEI@AlOOH is substantially lower than that of conventional silica-based and resin-based solid amine adsorbents, emitting merely 190 kg of CO₂ per ton of CO₂ captured. Additionally, the combination of reduced material costs, superior performance, and enhanced stability positions PEI@AlOOH as a highly cost-effective solution for carbon capture, emphasizing its significant potential for widespread application.

Figure 3. Life cycle assessment and economic cost analysis of PEI@AlOOH

This work provides a novel and technically robust framework for addressing CO₂ emissions from coal-fired power plants, with promising implications for future applications. It offers critical insights for the continued advancement and commercialization of carbon capture technologies.

Research Assistant Professor Xuehua Shen from the School of Environmental Science and Engineering is the first author of the paper. Professor Zuotai Zhang and Xuehua Shen are corresponding authors, with SUSTech serving as the first corresponding institution.

Paper link: https://doi.org/10.1021/acs.est.5c10968

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