Determination of Zn Speciation, Siting, and Distribution in Ferrierite Using Luminescence and FTIR Spectroscopy

0542441 - ÚFCH JH 2022 RIV US eng J - Journal Article
Olszówka, Joanna Elżbieta - Lemishka, Mariia - Mlekodaj, Kinga - Kubát, Pavel - Rutkowska-Żbik, D. - Dědeček, Jiří - Tabor, Edyta
Determination of Zn Speciation, Siting, and Distribution in Ferrierite Using Luminescence and FTIR Spectroscopy.
Journal of Physical Chemistry C. Roč. 125, č. 17 (2021), s. 9060-9073. ISSN 1932-7447. E-ISSN 1932-7455
R&D Projects: GA ČR(CZ) GA17-00742S
Institutional support: RVO:61388955
Keywords : Fourier transform infrared spectroscopy * Ions * Luminescence
OECD category: Physical chemistry
Impact factor: 4.177, year: 2021
Method of publishing: Limited access

A methodology for the analysis of the siting of Zn2+ ions in extra-framework cationic sites of silicon-rich zeolite was developed and demonstrated on Zn-ferrierite samples (Si/Al 8.5, Zn/Al 0.04-0.33). This methodology is based on the FTIR spectroscopy of antisymmetric tetrahedral-octahedral-tetrahedral (T-O-T) vibrations of the zeolite framework perturbed by Zn2+ ions, combined with a complementary approach based on Zn2+ luminescence monitored by laser-induced time-resolved luminescence spectroscopy. Three vibration bands in the FTIR spectra of antisymmetric T-O-T vibrations of dehydrated zeolite reflect Zn2+ ligation in three extra-framework cationic sites of ferrierite zeolite. The band at 935 cm-1 corresponds to Zn2+ ions in the α-site of ferrierite, the band at 917 cm-1 correspondsto ions in β-site, and the band at 902 cm-1 correspondsto Zn2+ ions in the γ-site. The extinction coefficient for quantitative analysis of Zn2+ ions in cationic sites was estimated and exhibited the same value for Zn2+ cations in all cationic sites, ϵ = 49.1 ± 3.8 cm·μmol-1. In all Zn samples, Zn2+ siting in the β-site prevails, while Zn2+ ions in the γ-site are of low population or negligible. Time-resolved luminescence showed that bare Zn2+ ions in the extra-framework cationic sites can be distinguished from Zn2+ ions in ZnO by a decay time which is several magnitudes longer and a high sensitivity for quenching. The luminescence spectrum of Zn-ferrierites is composed of three bands at 545, 480, and 425 nm attributable to Zn2+ ions in the α-, β-, and γ-site with luminescence coefficients (for semiquantitative analysis) ζα = 10.1, ζβ = 9.4, and ζγ = 8.8 mmol/g of Zn2+ ions in the α-, β-, and γ-sites, respectively. The analysis of Zn ions in ferrierites showed that ZnH-ferrierites exclusively contain Zn2+ ions in cationic sites. In the case of the ZnNa-FER sample with maximum Zn loading (Zn/Al 0.33), a small amount of Zn-oxo species can be formed.
Permanent Link: http://hdl.handle.net/11104/0319851