Key Takeaways & Executive Findings
- •• • Amine-functionalized hierarchical porous carbon spheres (0.2PW-K-CNF-PEI) achieved a CO2 adsorption capacity of 1.03 mmol/g at 100 °C, demonstrating effective capture at typical flue gas temperatures. • • The CO2 diffusion coefficient reached 0.0495 min−1, indicating rapid mass transfer due to retained macropores (total pore volume 0.0030–0.0066 cm3/g after amine loading). • • At 80 °C, the material exhibited superior selective CO2 adsorption of 44 mg/g, crucial for separating CO2 from flue gas mixtures. • • The synthesis method (ash self-templating and particle self-assembly) simultaneously created pores and loaded amines, increasing adsorption sites while preserving structural stability, offering a scalable route for waste-derived adsorbents.
Abstract
To address the high CO2 emission proportion in the industrial sector, distillers' grain waste was converted into biochar for CO2 adsorption from flue gas. Raw biochar suffers from weak pore adsorption and poor selectivity at elevated temperatures. This study employed ash self-templating and particle self-assembly to create hierarchical pores and simultaneously load amine groups onto distillers' grains-derived biochar, yielding amine-functionalized hierarchical porous carbon spheres. The amine loading significantly increased, providing more CO2 adsorption sites, while retaining macroporosity (total pore volume 0.0030–0.0066 cm3/g after amine loading), which enhanced morphological stability and CO2 mass transfer. The optimal sample, 0.2PW-K-CNF-PEI, exhibited a CO2 adsorption capacity of 1.03 mmol/g at 100 °C, a CO2 diffusion coefficient of 0.0495 min−1, and a selective adsorption capacity of 44 mg/g at 80 °C. This work offers a solution for valorizing distillers' grain by-products and capturing CO2 from low-temperature flue gas.
1. Introduction
Industrial CO2 emissions, primarily from fossil fuel combustion, necessitate efficient carbon capture technologies. Solid adsorbents like biochar are promising due to their low cost and sustainability, but unmodified biochar suffers from poor porosity and surface inertness, leading to low CO2 uptake and selectivity. Physical activation methods are energy-intensive and yield carbons with low CO2 selectivity, while chemical activation can create high-surface-area carbons but often requires harsh conditions. Amine functionalization introduces nitrogen groups that chemically bind CO2, enhancing selectivity and enabling adsorption at elevated temperatures (50–100 °C), matching flue gas conditions. However, amine loading often blocks pores, drastically reducing surface area and pore volume, which hampers adsorption kinetics and capacity.
This study addresses the bottleneck by employing ash self-templating and particle self-assembly to create hierarchical pores in distillers' grains-derived biochar while simultaneously loading amines. This approach preserves macroporosity, facilitating CO2 diffusion, and increases amine loading, providing abundant chemisorption sites. The resulting amine-functionalized hierarchical porous carbon spheres demonstrate enhanced CO2 adsorption capacity, kinetics, and selectivity at relevant temperatures, offering a cost-effective and sustainable solution for CO2 capture from industrial flue gas.
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ZHOU Rui, CHEN Jing, HE Jinglin, WANG Weihao, SU Hui, WANG Bangda, JIN Ziheng, JIANG Xia (2026). Synergistic Effect of Hierarchical Pores and Amine Functionalization on CO2 Adsorption Performance by Distillers' Grains-Derived Biochar Spheres. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202605020
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Frequently Asked Questions
What is the specific CO2 adsorption capacity and operating temperature for the best-performing material?
The optimal sample, 0.2PW-K-CNF-PEI, achieved a CO2 adsorption capacity of 1.03 mmol/g at 100 °C, with a diffusion coefficient of 0.0495 min−1.
How does the material maintain pore structure after amine loading, and why is that important?
The synthesis method retains part of the macroporous structure, with total pore volume remaining between 0.0030 and 0.0066 cm3/g after amine loading. This preserves pathways for CO2 diffusion, enhancing mass transfer and adsorption kinetics.
What is the CO2 selectivity performance at typical flue gas temperatures?
At 80 °C, the material exhibited a selective CO2 adsorption capacity of 44 mg/g, indicating effective separation of CO2 from other flue gas components.
What is the significance of using distillers' grains as a precursor?
Distillers' grains are a low-cost waste by-product from the liquor industry. Utilizing them for biochar production addresses waste management while providing a sustainable feedstock for CO2 adsorbents, contributing to circular economy principles.
What are the potential limitations or challenges for scale-up?
While the study demonstrates promising lab-scale performance, scale-up would require optimization of the self-assembly and amine loading processes to ensure uniformity and cost-effectiveness. The retention of pore structure and amine stability under repeated adsorption-desorption cycles also need further investigation.
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