Enhanced CO2 capture using sustainable biomass-derived activated carbon from desert date seed husk: Adsorption Isotherms, selectivity, and RSM optimization

The development of cost-effective and sustainable adsorbents for carbon dioxide (CO 2 ) capture remains a critical challenge in mitigating greenhouse gas emissions. In this study, the husk of desert date seeds, an abundant agricultural waste, was successfully converted into high-performance activated carbon (HDDS-AC) via KOH activation. Response surface methodology based on a central composite design (RSM–CCD) was used to systematically evaluate and optimize the effects of calcination temperature and holding time on the textural properties of the synthesized carbons. The optimized HDDS-AC prepared at 850 °C for 120 min exhibited a high BET surface area of approximately 2000 m 2 g −1 . N₂ physisorption analysis revealed a well-developed porous structure with a high total pore volume (1.246 cm 3 g −1 ) and a narrow average pore width in the range of 2–50 nm, indicating dominant meso/microporosity. Structural and morphological characterization using SEM, TEM, XRD, and TGA confirmed the formation of a highly porous, predominantly disordered carbon framework with sufficient thermal stability. At 273.15 K, the achieved experimental CO 2 uptake was 4.61 mmol g −1 , with CO 2 /N 2 and CO 2 /CH 4 selectivities up to 3.72 and 2.25, respectively. Isosteric heat of adsorption analysis yielded approximately 22 kJ mol −1 for CO 2 , indicating a physisorption-dominated mechanism with stronger CO 2 surface interactions than for CH 4 and N 2 . Equilibrium isotherm analysis showed that the Langmuir model best describes the adsorption behavior (R² = 0.968), with a maximum adsorption capacity of 6.71 mmol g⁻¹ . The results demonstrate that HDDS-AC is a competitive, low-cost, and sustainable adsorbent for CO 2 capture. • Sustainable activated carbon from desert date seed husk via a simple, cost-effective method. • RSM optimization produced high S(BET (∼2025 m² g⁻¹) and microporosity (0.90 nm). • High CO₂ adsorption capacity of 4.61 mmol g⁻¹ at 0 °C with strong selectivity over CH₄ and N₂. • Moderate isosteric heat of CO₂ adsorption (∼22 kJ mol⁻¹), indicating a physisorption-dominated mechanism.