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 (CO2) 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 m2 g−1. N₂ physisorption analysis revealed a well-developed porous structure with a high total pore volume (1.246 cm3 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 CO2 uptake was 4.61 mmol g−1, with CO2/N2 and CO2/CH4 selectivities up to 3.72 and 2.25, respectively. Isosteric heat of adsorption analysis yielded approximately 22 kJ mol−1 for CO2, indicating a physisorption-dominated mechanism with stronger CO2 surface interactions than for CH4 and N2. 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 CO2 capture.