Produção de carbonos porosos a partir de resíduo de podas de árvores

Abstract

The management of urban trees is inherent to every city and produces waste that is often lost and misallocated. In large cities such as the city of Natal, in Rio Grande do Norte, Brazil, the production of pruning waste reaches more than 18 tons weekly, which implies the allocation of a large area in landfills for disposal. Disposal in vacant lots contributes to eutrophication and visual pollution. As pruning residues are lignocellulosic materials, an alternative to add value to this residue and give it a more appropriate destination is to use it as a raw material for activated biochar. The term biochar has also been used for charcoal produced from lignocellulosic residues, previously this term was used only for charcoal intended for use in soil conditioning or CO2 sequestration. In this work, activation and pyrolysis occurred simultaneously; Mango Tree Residue (Magnifera indica) and Pruning Residue (various unidentified species) were used as precursors, KOH was used as activating agent, pyrolysis temperatures of 450°C and 550°C were used, which were maintained for 1 hour, and no gas flow was used; then, the activation product was washed with an HCl solution in order to remove the remaining activating agent and its derivatives. The products obtained were characterized by XRD, FTIR, CHN and adsorption of N2 and CO2. NO adsorption tests were carried out in dry air for all samples and for the Mango Tree Waste biochar sample produced at 550°C (M550 LVD) the test was also carried out in air atmospheres with 50% and 75% humidity, besides nitrogen atmosphere. The activated biochars showed similar compositions. The pyrolysis temperature was the factor with the greatest influence on the characteristics of the biochars: those produced at 550°C exhibited larger specific areas and more developed microporosity. Regarding NO adsorption tests in dry air, the M550 LVD sample had the highest adsorption result (83.91%). However, in air atmospheres with 50% and 75% humidity the adsorption results decreased to 54,55% and 25,82%, repectively, indicating a possible interaction of H2O molecules with the functional groups present on the biochar surface. The NO adsorption in nitrogen atmosphere showed the lowest result (0.83%), indicating the need for O2 for the NO adsorption mechanism