CO₂ Adsorption on Nanocomposite Pollen-Derived Carbons: Synergic Effect of KOH Activation and MgO Incorporation

Novel nanocomposites synthesized with pollen grain, as a precursor, were tested for CO₂ adsorption performance. The pollen-derived carbons were obtained by direct calcination (PC), calcination followed by KOH-chemical activation (PCKOH), and MgO incorporation using high-energy ball-milling (PC-MgO and PCKOH-MgO). All the as-prepared materials were texturally, morphologically and structurally characterized by N₂ physisorption, scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD); CO₂ adsorption/desorption was measured by thermogravimetry. The four materials were able to adsorb CO₂ at 30 ºC and 1 bar, but PCKOH-MgO, with the high surface area (12.4 m² g^-1), total pore volume of (0.13 cm³ g^-1) and microporosity, was the best (2.06 mmol g^-1 and percentage of adsorption (Q_ad) = 9.06%, at 1 bar). This result is due to the synergic effect of both synthesis methods. Neither temperature (from 30 to 100 ºC), nor pressure (from 1 to 15 bar), improved the adsorption process of PCKOH-MgO. CO₂ desorption times at 300 ºC were 47 min for PCKOH-MgO and 30 min for the other adsorbents, showing the possibility of cycling. Based on the obtained results, the PCKOH-MgO activated carbon nanocomposite stands as a promising adsorbent to be potentially used for industrial CO₂ capture applications and to contribute to long-term solutions to avoid dangerous climate-change and reduce CO₂ emissions.

Keywords:
pollen-derived carbons; KOH-chemical activation; MgO ball milling incorporation; textural properties; CO₂ adsorption/desorption