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<p>This study advances a sustainable pressurized-CO<sub>2</sub> activation route that transforms waste Bangladeshi jute sticks into ultrapure (&gt; 99%) highly microporous biochar for energy-efficient carbon capture. Activation at 800&#xa0;°C with CO<sub>2</sub> pressures up to 10&#xa0;bar for 1&#xa0;h in a custom Inconel reactor, combined with CHN, XRF, SEM–EDX, XRD, N<sub>2</sub>/CO<sub>2</sub> sorption with detailed ultra-microporosity analysis, and Raman spectroscopy, establishes a pressure–structure–property map in which pressure tunes the heteroatom content and pore architecture. Contrary to the conventional yield–porosity trade-off in physical activation, we observed a simultaneous increase in both the yield and porosity with increasing CO<sub>2</sub> pressure. A mechanistic hypothesis has been proposed, wherein deep CO<sub>2</sub> penetration and pressure-assisted CO<sub>2</sub>/CO reactions nucleate new micropores within macroscopic channels while preserving the carbon framework; this is consistent with porosity and particle size distribution analysis. At 800&#xa0;°C and 10&#xa0;bar CO<sub>2</sub>, the process delivered a 57.4 wt% yield, 1182 m<sup>2</sup>&#xa0;g<sup>–1</sup> total surface area (of which 844 m<sup>2</sup>&#xa0;g<sup>–1</sup> was contributed by regular micro/mesopores and the remaining 29% was from ultramicropores), and a total pore volume of 0.4746 cm<sup>3</sup>&#xa0;g<sup>–1</sup> (with a&#xa0;13% contribution from ultramicropores). The yield was ~ 20 wt% higher than that of atmospheric activation. All five samples exhibited high CO<sub>2</sub> uptake, ranging from 141 to 149&#xa0;mg&#xa0;g<sup>–1</sup>, owing to the dominant ultra-microporosity. As pressurized CO<sub>2</sub> activation is the least energy-intensive method among the common routes (e.g., steam or chemical activation), it enables scalable, low-cost sorbent manufacture and low-grade-heat regeneration, advancing energy-efficient post-combustion capture. The stability and tunable micro-and ultramicroporosity of the material also support adsorption-based cooling, energy storage, and gas separation. Overall, valorizing agricultural residues via pressurized-CO<sub>2</sub> activation provides a low-footprint route for sustainable porous carbon manufacture and the deployment of adsorption-based CO<sub>2</sub> capture in emerging-economy industrial clusters.</p> Graphical Abstract <p></p>

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Functionalized biochar with pressurized CO2 activation: toward superior porosity, yield, and CO2 capture efficiency

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月20日

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  • Md. Amirul Islam,
  • Bidyut Baran Saha

摘要

This study advances a sustainable pressurized-CO2 activation route that transforms waste Bangladeshi jute sticks into ultrapure (> 99%) highly microporous biochar for energy-efficient carbon capture. Activation at 800 °C with CO2 pressures up to 10 bar for 1 h in a custom Inconel reactor, combined with CHN, XRF, SEM–EDX, XRD, N2/CO2 sorption with detailed ultra-microporosity analysis, and Raman spectroscopy, establishes a pressure–structure–property map in which pressure tunes the heteroatom content and pore architecture. Contrary to the conventional yield–porosity trade-off in physical activation, we observed a simultaneous increase in both the yield and porosity with increasing CO2 pressure. A mechanistic hypothesis has been proposed, wherein deep CO2 penetration and pressure-assisted CO2/CO reactions nucleate new micropores within macroscopic channels while preserving the carbon framework; this is consistent with porosity and particle size distribution analysis. At 800 °C and 10 bar CO2, the process delivered a 57.4 wt% yield, 1182 m2 g–1 total surface area (of which 844 m2 g–1 was contributed by regular micro/mesopores and the remaining 29% was from ultramicropores), and a total pore volume of 0.4746 cm3 g–1 (with a 13% contribution from ultramicropores). The yield was ~ 20 wt% higher than that of atmospheric activation. All five samples exhibited high CO2 uptake, ranging from 141 to 149 mg g–1, owing to the dominant ultra-microporosity. As pressurized CO2 activation is the least energy-intensive method among the common routes (e.g., steam or chemical activation), it enables scalable, low-cost sorbent manufacture and low-grade-heat regeneration, advancing energy-efficient post-combustion capture. The stability and tunable micro-and ultramicroporosity of the material also support adsorption-based cooling, energy storage, and gas separation. Overall, valorizing agricultural residues via pressurized-CO2 activation provides a low-footprint route for sustainable porous carbon manufacture and the deployment of adsorption-based CO2 capture in emerging-economy industrial clusters.

Graphical Abstract