Dual valorization of seaweed-industry wastes into mechanically robust activated carbon pellets for CO2 capture

The dual valorization of seaweed-industry waste into mechanically robust activated carbon (AC) pellets for carbon dioxide (CO 2 ) adsorption in the flue gas streams provides a sustainable solution to mitigate global CO 2 emissions and industrial waste burdens. Therefore, this study addresses the limited research regarding the detailed conversion of dual seaweed-industry waste streams into AC pellets for CO 2 adsorption. In this work, raw seaweed waste was prepared, then synthesized into AC via KOH activation, followed by pelletization using a binder from carrageenan waste to develop AC pellets, which were then evaluated for detailed CO 2 adsorption performance. The kinetic mechanism of CO 2 adsorption was also investigated. The optimal parameters for AC development were a precursor:KOH weight ratio of 1:2 and an activation temperature of 700 °C. Under these conditions, the produced AC exhibited a BET surface area of 783.67 m 2 /g, microporosity exceeding 74%, and an average pore diameter of 2 nm. The breakthrough time and CO 2 adsorption capacity reached approximately 26 min and 0.79 mmol/g, respectively, at 25 °C, with a mixed-gas flow rate of 200 mL/min and a CO 2 concentration of 15%. The Avrami kinetic model provided the best fit for describing the CO 2 adsorption mechanism. The results of this study provide practical guidance for academia, industry, and policymakers to mitigate waste burdens and CO 2 emissions, in line with Sustainable Development Goals 9, 13, and 15. This work also demonstrates that seaweed-industry waste can be transformed into CO 2 adsorbents, providing a scalable strategy for climate action and a sustainable circular economy. • Seaweed-industry waste was converted into AC pellets for CO 2 adsorption. • Textural properties and surface chemistry of AC were characterized. • CO 2 adsorption, regeneration, and stability of AC pellets were evaluated. • AC pellets retained CO 2 adsorption capacity after 10 regeneration cycles and 180 days. • The Avrami model best described CO 2 adsorption kinetics.