Functional Activated Biocarbons Based on Biomass Waste for CO₂ Capture and Heavy Metal Sorption

Inexpensive porous activated biocarbons were prepared from biomass and agriculture waste following the method of thermal and hydrothermal carbonization and activation with superheated water vapor. The activated biocarbons were characterized by nitrogen adsorption-desorption at 77 K, SEM, XRD, Raman spectrometry, FTIR spectroscopy, determination of particle size, and elemental composition by XRF. The specific surface area was in the range of 240-709 m²/g, and the total pore volume was from 0.12 to 0.43 cm³/g. The percentage of microporosity in activated biocarbons was 89-92%. These activated biocarbons have been used for CO₂ and heavy metal sorption. Activated biocarbons based on pine cones and birch prepared by thermal carbonization and activation with superheated water vapor had the highest ability to capture CO₂ and amounted to 6.43 and 6.00 mmol/g at 273 K, as well as 4.57 and 4.22 mmol/g at 298 K, respectively. The best activated biocarbon was characterized by unchanged stability after 30 adsorption and desorption cycles. It was proved that the adsorption of CO₂ depends on narrow micropores (<1 nm). Activated biocarbons have also been analyzed as effective adsorbents for removing Cu²⁺, Zn²⁺, Fe²⁺, Ni²⁺, Co²⁺, and Pb²⁺ ions from aqueous solutions. Activated biocarbons are effective adsorbents for the removal of lead and zinc ions from aqueous solutions.