Optimizing the synthesis of nanoporous activated carbon from date-palm waste for enhanced CO2 capture

Abstract

Optimizing process parameters is essential for developing high efficacy carbonaceous adsorbents. This study investigated carbon dioxide (CO2) capture using activated carbon (AC) synthesized from date-palm leaflets. Key process parameters—pyrolysis temperature, residence time, and KOH-to-carbon (KOH/C) impregnation ratio—were systematically varied to synthesize highly nanoporous AC for enhanced CO2 uptake. Instead of relying on an intuitive selection of process variables, the optimization process was implemented using Response Surface Methodology (RSM) protocol, which provided a structured and effective strategy for process optimization. Over twenty different AC samples were synthesized and evaluated for their CO2 adsorption capacities. The optimal conditions, identified as 700 °C, 1.5 h, and a 3:1 (KOH/C) impregnation ratio, yielded AC with exceptional CO2 uptake capacities of 6.71 mmol/g at 0 °C and 4.214 mmol/g at 25 °C, outperforming most previously reported biomass-derived ACs. This superior performance is attributed to the well-developed nanoporous structure and high nitrogen content of the optimized sample, as confirmed by N2 adsorption isotherms, elemental analysis, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The optimized AC demonstrated excellent stability over multiple adsorption–desorption cycles. Additionally, a high isosteric enthalpy of adsorption (35 kJ/mol at 0.2 mmol/g) further confirmed preferential CO2 adsorption at energetically favorable nanopore sites. This study underscores the potential of date-palm leaflets as a sustainable and abundant precursor for synthesizing high-efficacy AC for carbon capture.