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Titolo:
Structure and ion exchange properties of tunnel type titanium silicates
Autore:
Clearfield, A;
Indirizzi:
Texas A&M Univ, Dept Chem, College Stn, TX 77843 USA Texas A&M Univ College Stn TX USA 77843 t Chem, College Stn, TX 77843 USA
Titolo Testata:
SOLID STATE SCIENCES
fascicolo: 1-2, volume: 3, anno: 2001,
pagine: 103 - 112
SICI:
1293-2558(200101/02)3:1-2<103:SAIEPO>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
NEUTRON POWDER DIFFRACTION; CRYSTAL-STRUCTURES; POROUS TITANOSILICATE; PHARMACOSIDERITE; GERMANATES; PHASES; CS+; K+;
Keywords:
titanium silicates; tunnel structures; ion exchange;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
24
Recensione:
Indirizzi per estratti:
Indirizzo: Clearfield, A Texas A&M Univ, Dept Chem, College Stn, TX 77843 USA Texas A&M Univ College Stn TX USA 77843 e Stn, TX 77843 USA
Citazione:
A. Clearfield, "Structure and ion exchange properties of tunnel type titanium silicates", SOLID ST SC, 3(1-2), 2001, pp. 103-112

Abstract

A large number of titanium silicates are known to exist in the mineral realm and recently a considerable literature has developed concerned with the synthesis and properties of these and related compounds. This paper describes two such families that have tunnel structures filled with cations that may easily be exchanged. A sodium titanosilicate of ideal formula, Na2Ti2O3(SiO4)(2). 2H(2)O, is tetragonal and built up of Ti4O4 cubane-Iike structures linked together by silicate groups in the a and b directions in the form of a square. In the c-axis direction, the cubane groups are linked by oxo-groups to form a framework enclosing tunnels parallel to the c-axis direction. The several ion exchange sites were identified based upon X-ray diffraction studies and the reason for the great affinity of this compound for Cs+ elucidated. The second family of compounds have the general composition M3H(TiO)(4)(SiO4)(3). 4H(2)O (M = alkali metal cation) and have the pharma-cosiderite structure. The sodium or potassium phases are selective for Sr2+ and Cs+. These compounds are cubic and have similar Ti4O4 cubane-like groups. In this case, the connectivity via silicate groups extends along all threecrystallographic axes equally. This change in crystal system has a profound effect upon the ion exchange behavior. This effect, as well as the effectof germanate substitutions for silicate, will be described. (C) 2001 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

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Documento generato il 18/11/17 alle ore 03:38:28