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<p>Biomass-derived activated carbons are attractive adsorbents for carbon dioxide capture because they combine low precursor cost, chemical robustness, moisture tolerance, and tunable microporosity. Here, sunflower stem pith, an agricultural residue with a naturally porous cellular structure, was converted to activated carbon through nitrogen carbonization followed by alkali hydroxide activation using either KOH or NaOH. Carbonization temperature and time-controlled char yield, and the progressive removal of lignocellulosic functional groups, while the activation chemistry determined the final pore architecture. The highest BET surface area was obtained for the NaOH-activated sample prepared from the 500&#xa0;°C/120 min char (AC-4, 2948 m<sup>2</sup>g<sup>− 1</sup>), whereas the corresponding KOH-activated sample (AC-2) showed a lower BET surface area (2268 m<sup>2</sup>g<sup>− 1</sup>) but a higher micropore-to-total-pore-volume ratio (0.78) and a smaller average pore diameter (2.08&#xa0;nm). CO<sub>2</sub> adsorption measurements at 25&#xa0;°C up to 8&#xa0;bar demonstrated that AC-2 outperformed the NaOH-activated analogues and the commercial activated carbon, reaching 13.92 mmol g<sup>− 1</sup> at 8&#xa0;bar, compared with 10.87 mmol g<sup>− 1</sup> for AC-4 and 4.58 mmol g<sup>− 1</sup> for the commercial sample. The adsorption capacity decreased with increasing temperature, and the isosteric heat analysis was consistent with exothermic physisorption. These findings show that the CO<sub>2</sub>-capture performance of biomass-derived activated carbons should be optimized by pore-size engineering and micropore accessibility rather than by BET surface area alone. Sunflower pith is therefore a promising regional precursor for low-cost carbon adsorbents, especially for pressure-swing adsorption scenarios where high-pressure working capacity is important.</p>

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Micropore-engineered activated carbons from sunflower pith for enhanced CO2 capture

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Sahand Saeidi Harzand,
  • Alp Yürüm

摘要

Biomass-derived activated carbons are attractive adsorbents for carbon dioxide capture because they combine low precursor cost, chemical robustness, moisture tolerance, and tunable microporosity. Here, sunflower stem pith, an agricultural residue with a naturally porous cellular structure, was converted to activated carbon through nitrogen carbonization followed by alkali hydroxide activation using either KOH or NaOH. Carbonization temperature and time-controlled char yield, and the progressive removal of lignocellulosic functional groups, while the activation chemistry determined the final pore architecture. The highest BET surface area was obtained for the NaOH-activated sample prepared from the 500 °C/120 min char (AC-4, 2948 m2g− 1), whereas the corresponding KOH-activated sample (AC-2) showed a lower BET surface area (2268 m2g− 1) but a higher micropore-to-total-pore-volume ratio (0.78) and a smaller average pore diameter (2.08 nm). CO2 adsorption measurements at 25 °C up to 8 bar demonstrated that AC-2 outperformed the NaOH-activated analogues and the commercial activated carbon, reaching 13.92 mmol g− 1 at 8 bar, compared with 10.87 mmol g− 1 for AC-4 and 4.58 mmol g− 1 for the commercial sample. The adsorption capacity decreased with increasing temperature, and the isosteric heat analysis was consistent with exothermic physisorption. These findings show that the CO2-capture performance of biomass-derived activated carbons should be optimized by pore-size engineering and micropore accessibility rather than by BET surface area alone. Sunflower pith is therefore a promising regional precursor for low-cost carbon adsorbents, especially for pressure-swing adsorption scenarios where high-pressure working capacity is important.