Characterization of Cuban and Brazilian natural zeolites by photoacoustic spectroscopy and electron paramagnetic resonance

• Autor(a) principal: LARA-BERNAL,ARLEM
• Data de Publicação: 2022
• Outros Autores: SILVA,MARCELO G. DA, MOTA,LEONARDO, MARÍN,ERNESTO, CORDEIRO,THALLIS C., SILVA,EDSON C. DA, VIANA,DANIEL A., VARGAS,HELION, POLIDORO,JOSÉ CARLOS, MELLO-MONTE,MARISA BEZERRA DE
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Anais da Academia Brasileira de Ciências (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652022000100401
• topic: Characteristic diffusion time; natural zeolites; nonradiative relaxation time; phase resolved method; Racah parameters

Abstract This report describes the photoacoustic and electron paramagnetic resonance investigations of Brazilian and Cuban zeolites. Photoacoustic optical absorption measurements indicate the presence of iron (Fe 3 +) ions with their respective transition bands for both zeolites. Two species of manganese (Mn 2 + and Mn 3 +) were identified in the Cuban sample and the electronic transitions assigned. Iron and manganese ions were confirmed through nonradiative relaxation ( τ) and characteristic diffusion ( τ β) times evaluation, whose values were found to be τ BRA = 5.40 ms, τ CUB = 4.60 ms, τ β BRA = 387 μs and τ β CUB = 305 μs. Crystal field (Dq- BRA/Dq- CUB = 1048 cm − 1/945 cm − 1) plus Racah (B- BRA/B- CUB = 457 cm − 1/813 cm − 1 and C- BRA/C- CUB = 3655 cm − 1/2496 cm − 1) parameters were assessed as well. Paramagnetic resonance corroborated Fe 3 + ions present in the Brazilian zeolite occupying sites showing axial and/or rhombic symmetry distortions. For the Cuban sample, results reveal the characteristic hyperfine sextet lines of Mn 2 + overlapping the Fe 3 + line. Values of Landé factor and isotropic hyperfine splitting constant were found to be 2.0 and 9.7 mT, respectively. This tells us that the Mn 2 + lies in octahedral symmetry probably replacing calcium ions and point towards an ionic bonding character of the Mn 2 + and its surroundings.