Valorization of Seaweed Industrial By-Product as a Binder for Developing Activated Carbon Pellets for CO₂ Adsorption

The valorization of industrial by-products rich in valuable compounds is a significant global focus in biomass conversion, waste mitigation, and the circular economy. Activated carbon (AC) powder is unsuitable for CO₂ adsorption in its original form; as such, it should be converted into pellets to improve handling, mechanical properties, and practical application for CO₂ capture. This study investigated the utilization of carrageenan by-products as a binder in the development of AC pellets for CO₂ adsorption. The by-product was prepared and characterized, and its properties were compared to those of the primary product, carrageenan. For further characterization, the AC pellets were subjected to compressive strength testing prior to CO₂ adsorption, followed by FTIR, TGA, SEM-EDX, and Raman analyses, which were conducted before and after CO₂ adsorption. The performance of CO₂ adsorption was assessed using a fixed-bed adsorption column at various temperatures ranging from 25 to 55 °C. The findings indicated that the binder demonstrated properties akin to carrageenan as the primary product, yet its gel strength was roughly four times lower. The AC pellets exhibited a compressive strength of 3.68 MPa, demonstrating satisfactory structural integrity. The AC pellets showed effective CO₂ adsorption at 25 °C, achieving a breakthrough time of ~ 15 min and an adsorption capacity of 20.47 mg CO₂/g adsorbent. The carrageenan by-product is a viable and low-cost binder for developing AC pellets for CO₂ adsorption. Ultimately, its utilization enables the practical conversion of AC powder into pellets for CO₂ adsorption, while simultaneously reducing waste from the seaweed industry.