Local structure of highly dispersed lead species incorporated within zeolite: experimental and theoretical studies

Zhanpeisov, Nurbosyn U.; Ju, Woo-Sung; Iino, Kiyoshi; Matsuoka, Makoto; Anpo, Masakazu

doi:10.1163/156856703765694345

Cited by 9 publications

(8 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the fitted R for the Pb–O1 path for the pH 6 sample of 2.28 Å is consistent with the 2.30 Å distance fitted by Ju et al in a Pb-ZSM-5 system. The fitted CN (2.5) of this scattering path is ∼3, suggesting a 3-fold O coordination, consistent with the triangular configuration of the oxygen base of the distorted PbO 4 tetrahedron of PbO·(H 2 O) [M-1 (Figure S7a)]. Although this triangular oxygen configuration has been previously reported, the Pb–O 2 scattering (path 2 in this study) is novel.…”

Section: Resultssupporting

confidence: 86%

“…The fitted CN (2.5) of this scattering path is ∼3, suggesting a 3-fold O coordination, consistent with the triangular configuration of the oxygen base of the distorted PbO 4 tetrahedron of PbO·(H 2 O) [M-1 (Figure S7a)]. Although this triangular oxygen configuration has been previously reported, the Pb–O 2 scattering (path 2 in this study) is novel. The PbO 4 tetrahedron and the further PbO·(H 2 O) type surface precipitation were first identified on the surface of the ZSM-5 system during data analysis and fitting conducted in this study.…”

Section: Resultssupporting

confidence: 86%

See 1 more Smart Citation

Spectroscopic and Modeling Investigation of Sorption of Pb(II) to ZSM-5 Zeolites

et al. 2020

View full text Add to dashboard Cite

Methyl tert-butyl ether (MTBE) was used as a replacement for Pb in gasoline before it was found to be harmful, and for this reason, these two contaminants often coexist in groundwater at older fueling facilities. ZSM-5 is a well-characterized synthetic zeolite that shows promise in the removal of organic contaminants from water. While numerous studies have quantified the adsorption of metal to hydrophilic zeolites, few have investigated the mechanisms for adsorption to hydrophobic zeolites such as ZSM-5. In this study, batch adsorption tests and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses were conducted to investigate the adsorption of Pb to ZSM-5 in the presence and absence of MTBE. Batch adsorption studies showed that MTBE did not significantly impact Pb adsorption. EXAFS analyses revealed two Pb binding mechanisms: (1) precipitation as a PbO•(H 2 O) type surface coating and (2) adsorption of Pb at Si surface sites. The PbO•(H 2 O) type surface coating is more stable at pH 6 due to the formation of solid-phase hydroxide minerals, while the Pb to Si surface site occupancy is constrained by the availability of silanol sites on the surface. Our study provides an understanding of the mechanisms of precipitation and/or adsorption of Pb to hydrophobic zeolites and new insights into the synthesis and/or modification of zeolites to target the removal of cocontaminants from water and wastewater.

show abstract

Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 86%

Spectroscopic and Modeling Investigation of Sorption of Pb(II) to ZSM-5 Zeolites

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Other important examples are lead‐containing zeolites with framework Pb II species; these compounds are promising photocatalysts in denitrification (de‐NO x ) reactions 4. 5 Despite the considerable effort that has been devoted to the synthesis and characterization of these interesting materials, there is still no well‐defined model to explain the observed catalytic properties. As the heteroatoms are postulated to be the active sites for the oxidation reactions, accurate information on their coordination environment and electronic structure is of fundamental importance for understanding the catalytic behavior of the heteroatom‐substituted zeolites and for designing new materials with predetermined properties.…”

Section: Calculated Energies [Kj Mol−1] For the Hydrolysis Reactions mentioning

confidence: 78%

“…The Pb II center appears to be a special case. In agreement with X‐ray absorption near‐edge structure (XANES) and FT‐EXAFS measurements on Pb II /ZSM‐5, our results indicate that triply coordinated Pb II species are preferred within the zeolite framework 5. In fact, a Pb II center in a tetrapodal configuration was not found, because the atom is too big to retain the tetrahedral coordination.…”

Section: Calculated Energies [Kj Mol−1] For the Hydrolysis Reactions mentioning

confidence: 99%

Formation of Heteroatom Active Sites in Zeolites by Hydrolysis and Inversion

Sokol

French

et al. 2006

Angew Chem Int Ed

View full text Add to dashboard Cite

Following the discovery of the titanosilicalite zeolite TS-1 and its remarkable catalytic properties in selective oxidation reactions with aqueous H 2 O 2 , [1] there have been several reports on the possible use of other heteroatom-substituted zeolites. Of particular interest are tin and zirconium silicalites, which are efficient catalysts in the hydroxylation of phenol with aqueous H 2 O 2 .[2] Germanium-containing silicalites, as well as a number of Ti-Ge-Si zeolites, showing catalytic activity toward oxidation with H 2 O 2 , have also been successfully synthesized. [3] Other important examples are leadcontaining zeolites with framework Pb II species; these compounds are promising photocatalysts in denitrification (de-NO x ) reactions. [4,5] Despite the considerable effort that has been devoted to the synthesis and characterization of these interesting materials, there is still no well-defined model to explain the observed catalytic properties. As the heteroatoms are postulated to be the active sites for the oxidation reactions, accurate information on their coordination environment and electronic structure is of fundamental importance for understanding the catalytic behavior of the heteroatom-substituted zeolites and for designing new materials with predetermined properties.Herein, we propose a new model for the formation of active sites in silicalite, which is based on the hydrolysis and inversion of tetrahedral sites in the zeolitic framework. We demonstrate that the inversion mechanism can help to stabilize the active sites, as well as increase their accessibility to guest molecules in the zeolite pores. This model is in agreement with early experimental studies on TS-1, [6] which suggested that hydrolysis of a TiÀOÀSi bridge forces the titanium atom to move away from its tetrahedral configuration to a new more "external" relaxed position. In contrast, current models make a strong distinction between the modes of incorporation of titanium atoms: in zeolites they occupy tetrapodal sites within the framework, while in mesoporous materials they are grafted onto the silica surface and have a tripodal coordination environment.[7] Our calculations show that both configurations are realized within zeolites and that the hydrolysis-plus-inversion mechanism is the missing link between them.The characteristic features of this model are closely related to a number of structures in silica. For example, it has been postulated that the hydrolysis step during silica synthesis occurs through an S N 2 mechanism with inversion of a silicon tetrahedron.[8] A similar mechanism was reported for the formation of positively charged oxygen-vacancy defects (E' centers) in a-quartz and amorphous silica.[9] It was suggested that the E' center undergoes a distortion to a stable puckered configuration, which is accompanied by a large relaxation of the silicon atoms adjacent to the oxygen vacancy. Recently, Sokol et al. advanced the hydrolysis-plusinversion model for the stabilization of intrinsic defects, for example, vicinal disilan...

show abstract

“…Photocatalytic conversion over various photocatalysts, such as titanium dioxide (TiO 2 ) [1][2][3], zeolites incorporated with transition metal ions (Cu + , Ag + , Pb 2+ ) [4][5][6][7], was recently applied to remove atmospheric NO x ; thereinto, TiO 2 became the most widely used photocatalyst because of its non-noxious and stable chemical properties. Researchers have fully studied the kinetics of this reaction [8] and used various materials as supporter to enhance the efficiency of TiO 2 under UV light irradiation [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic oxidation of NO x over visible-light-responsive nitrogen-doped TiO2

Zhou

Tan

Zhao

et al. 2007

Korean J. Chem. Eng.

View full text Add to dashboard Cite

In order to utilize visible-light in photocatalytic conversion of NO x , nitrogen atoms were doped in commercially available photocatalytic TiO 2 powders by impregnating method. The crystal structures of TiO 2 were not changed after calcination process. Analysis by X-ray photoelectron spectroscopy (XPS) indicated that N atoms were incorporated in the bulk phase of TiO 2 as N-Ti-O linkages. A significant shift of the absorption edge to a lower energy and a higher absorption in the visible-light region were observed. These N-doped TiO 2 powders exhibited photocatalytic activity of the oxidation of NO x under visible-light irradiation. The sample mixed with 20 wt% ammonium carbonate and calcined in 600 o C showed best photocatalytic activity and its activity can be restored by rinsing with water after longterm operation.

show abstract

Local structure of highly dispersed lead species incorporated within zeolite: experimental and theoretical studies

Cited by 9 publications

References 27 publications

Spectroscopic and Modeling Investigation of Sorption of Pb(II) to ZSM-5 Zeolites

Spectroscopic and Modeling Investigation of Sorption of Pb(II) to ZSM-5 Zeolites

Formation of Heteroatom Active Sites in Zeolites by Hydrolysis and Inversion

Photocatalytic oxidation of NO x over visible-light-responsive nitrogen-doped TiO2

Contact Info

Product

Resources

About