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Cigarette filters were utilized as carbon source for the production of solid carbon acid catalysts. In this study, the process of carbonization and simultaneous sulfonation via hydrothermal treatment was employed. The catalysts were prepared by mixing cigarette filters and sulfuric acid at temperatures of 100, 150, and 190 °C for durations ranging from 2 to 8 h. It was observed that the highest conversion of oleic acid occurred when the catalyst was synthesized at 190 °C for 4 h. The optimized conditions for the esterification reaction using this catalyst included an oleic acid to methanol molar ratio of 1:12, a catalyst loading of 5 wt%, and a temperature of 100 °C for 1 h. Additionally, the catalyst was successfully reused four times without significantly impacting the reaction yield. These findings highlight a promising approach for the utilization of waste materials, with immediate implications for waste management practices and positive environmental impacts., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

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 CO 2 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 CO 2 capture. The analysis of N 2 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 m 2 /g, while, in chemical activation, it was 1421 to 2730 m 2 /g. The sample treated via the chemical method (BS6-K1) showed better performance in CO 2 adsorption, with adsorption results of 3.8 and 6 mmol/g of CO 2 at 25 ℃ and 0 °C, respectively, at 101 kPa. CO 2 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 CO 2 capture., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)