CO₂ capture by microporous carbon based on Brazil nut shells

The increase in burning, deforestation, and the exorbitant use of fossil fuels have contributed to the increase in carbon dioxide emissions; this gas is responsible for the intensification of the greenhouse effect and radical climate changes. In this way, it becomes necessary to find alternatives to reduce its emission. Porous carbon materials synthesized from lignocellulosic waste can be employed in technologies for capture and utilization of CO₂ due to the advantages such as selectivity, low-cost synthesis, high surface area and pore volume, and thermal and chemical stability. Considering the availability of Brazil nut biomass residues in the Amazon region, this article proposes to synthesize activated carbon from the lignocellulosic residue using physical and chemical activation methods for CO₂ capture. The analysis of N₂ adsorption-desorption isotherms proves the predominance of a microporous structure when using the two synthesis methods described here. In physical activation, the surface area was 912 m²/g, while, in chemical activation, it was 1421 to 2730 m²/g. The sample treated via the chemical method (BS6-K1) showed better performance in CO₂ adsorption, with adsorption results of 3.8 and 6 mmol/g of CO₂ at 25 ℃ and 0 °C, respectively, at 101 kPa. CO₂ adsorption capacity is due to the high volume of ultramicropores. It is believed that the microporous carbon material synthesized from Brazil nut residues is an alternative precursor for carbon materials used as CO₂ capture.