Rare Gas Adsorption to Silver-Exchanged Zeolites

Qian Wang,Shuming Peng,Shulong Wen,Zheng Huang,Fanhua Hao

doi:10.1155/2015/342525

Abstract

The adsorption of rare gas atoms to silver aluminosilicate has been investigated using density functional theory (DFT) with the local density approximation, generalized gradient approximation, and dispersion correction. The adsorption energies of rare gas atoms to the honeycomb lattice of silver aluminosilicate were calculated, and the results are discussed. The relationship between the electric charge density distribution and the adsorption energy is discussed. It indicates that the xenon atom has the most electrons to affect the van der Waals dispersion, so it has the highest minimum charge density, strongest polarization, most spacious spherical scope, and most favorable adsorption on silver zeolites.

Highlights

Rare gas adsorption technology is important to detect and prevent the leakage of radioactive isotopes, including radioactive xenon isotopes in the products of radio nuclides [1,2,3]
To reasonably describe the structure of silver-exchanged zeolite, a silver aluminosilicate (AgSiAlO4) system was derived from the kaolinite structure, in which the protons were replaced by silver ions, some of the water molecules were removed, and the alumina-octahedron changed to tetrahedron with four oxygen atoms around each aluminum atom
The results show that the effect of van der Waals forces on the geometry of silver aluminosilicate is very small

Summary

Introduction

Rare gas adsorption technology is important to detect and prevent the leakage of radioactive isotopes, including radioactive xenon isotopes in the products of radio nuclides [1,2,3]. Rare gases exhibit unique adsorption properties on silver-exchanged zeolite molecular sieves; in particular, the adsorption heat of xenon on silverexchanged zeolite is significantly higher than that on the sodium zeolite molecular sieve [9]. It is important to study the adsorption of rare gas atoms on silver-exchanged zeolite molecular sieves for the development of rare gas collection, separation, and purification. Kaolinite has the formula Al4(Si4O10)⋅(OH) and is composed of silica-tetrahedron and alumina-octahedron sharing oxygen atoms. The layered structures composed of tetrahedron and octahedron have negative charges, and protons H+ are distributed among the layers to ensure electrical neutrality. Zeolite molecular sieves prepared with kaolin as the raw material have the advantages of large size, good thermal stability, and low price

Methods

Results

Conclusion