(600c) Low-Cost Nitrogen-Doped Activated Carbon Derived from Naturally Occurring Waste Leaves and Microalgae for CO2 Capture

This work puts forward an effort to optimize the production of efficient and cost-effective carbon-based CO2 adsorbents through hydrothermal carbonization (HTC) and subsequent activation of inexpensive and natural precursors; biomass (Citrus Aurantium waste leaves) and microalgae (Spirulina). We optimized the parameters of the HTC procedure (biomass/microalgae weight ratio, reaction temperature, and reaction time) to generate hydrochars with the high mass yield, and optimally incorporated nitrogen functional groups. Hydrochars were further activated (via the ZnCl2/CO2 activation), resulting in Nitrogen-doped (microalgae) activated carbons with both (i) high nitrogen content and (ii) ultra-microporous structure, features that synergistically work together to greatly increase the CO2 adsorption capacity of the activated carbons. Our elemental and molecular analysis suggests the incorporation of stable pyridinic nitrogen groups within the carbon matrix to yield a higher density of N-doped active sites responsible for i) strong interaction between the activated carbon surface and CO2 molecules and ii) increasing the number of total ultra-micropores with smaller average pore diameter (Davg) during the activation. The resulting naturally derived optimized CO2 adsorbent (AC-180-4-1) exhibits one of the highest CO2 adsorption capacity (8.43 mmol/g) and has the potential for widespread implementation and scale-up which is critically required to enable efficient carbon capture.