Theoretical and experimental evidences for the formation of carbonate anion radical (CO3-center dot) in the atmosphere

Autor(es)

Bihain, Murielly Fernanda Ribeiro ; Oh, Laura Beatriz Camargo ; Teixeira, Keila Cardoso ; Cavallini, Grasiele Soares ; Pereira, Douglas Henrique

• Tipo de documento: Artigo Científico
• Fonte: ATMOSPHERIC POLLUTION RESEARCH; v. 14, n. 6, p. 6-pg., 2023-06-01.

Resumo

Troposphere is the lowest layer where the oxidation reactions responsible for the atmospheric self-purification of contaminants occur, which are initiated mostly by hydroxyl radicals (HO center dot). In this context, the objective of the present work was to carry out theoretical and experimental studies on the formation of the carbonate anion radical (CO3-center dot) in the atmosphere and evaluate the spontaneity of chemical reactions that occur at molecular. Experimental tests to evaluate the formation of CO3-center dot in the atmosphere were conducted using rainwater samples containing 5, 10, and 15 mg L-1 of sodium carbonate, and the addition of methylene blue dye was used to indicate the formation of the CO3-center dot by monitoring its degradation. Exposure of the samples to solar radiation led to a greater degradation of the dye in rainwater samples with higher concentrations of bicarbonate. The determination of the alkalinity of the samples revealed that the predominant chemical species in the medium was the bicarbonate anion and that the increase in its concentration promotes the formation of CO3-center dot. As a result of the simulation of the reactions with the radicals (OH)-O-center dot, (OOH)-O-center dot, and CO3-center dot at the level of theory MP2/6-311++G (2df,p), it was obtained that the formation of the radical CO3-center dot is possible (HO center dot + CO32- -> HO- + CO3-center dot and HCO3- + HO center dot -> H2O + CO3-center dot). The simulations were carried out in aqueous phase with implicit solvent, in the gas and showed the same trends. Furthermore, the reactions involving CO3-center dot with atmospheric molecules are spontaneous (Delta(r)G(298) < 0) for electron-rich groups as H2S compounds, indicating that the radical CO3-center dot can react with some atmospheric molecules, and thus contribute to the atmospheric oxidation mechanisms. (AU)

• Processo FAPESP: 13/08293-7 - CECC - Centro de Engenharia e Ciências Computacionais
• Beneficiário: Munir Salomao Skaf
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs
• Processo FAPESP: 17/11485-6 - Desenvolvimentos computacionais e teóricos baseados em métodos ab initio e na Teoria do Funcional de Densidade
• Beneficiário: Rogério Custodio
• Modalidade de apoio: Auxílio à Pesquisa - Regular