Enhanced Assembling of N-and-K-Riched Macroalgae as Carbon Adsorbent for CO₂ Capture with Ni(NO₃)₂/KOH as Co-Catalysts

Porous-activated carbons have drawn great attention due to their important role in CO₂ capture. Ni(NO₃)₂/KOH, as co-catalysts under different temperatures, were studied to obtain porous graphitized carbon from Sargassum horneri feedstock. The results indicated that the properties of the porous graphitized carbon generated at 850 °C were greatly enhanced, showing a large specific surface area of 1486.38 cm³·g⁻¹ with narrowly distributed micropores (~0.67 nm) and abundant functional groups, which endowed high CO₂ uptake; moreover, the high CO₂ uptake was mainly attributed to the synergistic effect of Ni(NO₃)₂ and KOH, both in chemical modification and pore formation. The fitted values of the four kinetic models showed that the double exponential model provided the best description of carbon adsorption, indicating both physical and chemical adsorption. It is worth noting that carbon could be reused four times in the adsorption/desorption procedure in this research with good stability. This work focuses on the high-value-added comprehensive utilization of macroalgae, which not only is important for high-performance adsorbent preparation but also has positive benefits for the development and utilization of macroalgae resources.