Biobased derived nanoporous carbon for hydrogen isotope separation

Abstract

Nuclear fusion as a clean energy source is an approach proposed to solve the expected global energy crisis. Deuterium an isotope of hydrogen, is required as fuel but its conventional separation process is highly energy-intensive. However, selective separation of D2 from H2 gas mixtures using nanoporous materials is a promising solution. To this end, cost-effective nanoporous carbon from agricultural waste has been developed (peanut shell, ginkgo leaf, and metasequoia leaf). Porosity, morphology, and compositional properties of the developed carbon were investigated and compared with commercial activated carbon. The developed carbon achieved a specific surface area of 692 m2/g and a specific pore volume of 0.387 cm3/g with narrow pore size distribution. Hydrogen and deuterium adsorption isotherms were studied at various temperatures (25 K, 40 K, 60 K, and 77 K) for all carbons. D2/H2 selectivity using the ideal adsorption solution theory of equimolar composition and pressures of D2 and H2 was carried out. The D2/H2 selectivity in ginkgo leaf-derived carbon achieved a selectivity value of 4.1 at 25 K, higher than other biomass-derived carbons and commercial activated carbon. Additionally, the heat of adsorption of D2 and H2 for all carbons was evaluated. A large difference between these values was observed in ginkgo leaf-derived carbon. This difference is three times larger than commercial activated carbon, leading to a higher rate of interaction between D2 and carbon than that between H2 and carbon due to rich Ca content in carbon. Thus, metal residues in biomass carbon seem to play a significant role in selective separation of D2 over H2.