A new framework topology in the dehydrated form of zeolite levyne.

0003-004X/13/1112\u20132063$05.00/DOI: http://dx.doi.org/10.2138/am.2013.4583 2063 A new framework topology in the dehydrated form of zeolite levyne Rossella Arletti1, Giovanna Vezzalini2, Simona Quartieri3, Fernando C\ue1mara1 and Matteo Alvaro4,* 1Dipartimento di Scienze della Terra, Universit\ue0 di Torino, via Valperga Caluso n. 35, 10125 Torino, Italy 2Dipartimento di Scienze Chimiche e Geologiche, Universit\ue0 di Modena e Reggio Emilia, via Giuseppe Campi, 183, 41125 Modena, Italy 3Dipartimento di Fisica e Scienze della Terra, Universit\ue0 di Messina, Viale F. Stagno D\u2019Alcontres, 31, 98122 Messina, Italy 4Dipartimento di Scienze della Terra e dell\u2019Ambiente, Universit\ue0 degli Studi di Pavia, Italy; and International Research School of Planetary Sciences, Universit\ue0 G. d\u2019Annunzio, Chieti, Italy A bstract The thermoelastic behavior and structural evolution of a natural levyne-Ca [(Ca7.8 Na2.2K1.1)\u3a311.1 Al20.0Si34.2O108 c551.5H2O; R3m; a = 13.377(4) \uc5, c = 22.870(1) \uc5, V = 3544.1(3) \uc53] were studied by both T-resolved synchrotron X\u2011ray powder diffraction (SR-XRPD) between room temperature and 800 \ub0C, and by conventional-source high-temperature single-crystal X\u2011ray diffraction (SC-XRD). Above 230 \ub0C, water loss and reallocation of extraframework cations induce the straining and consequent breaking of T-O-T bridges in the D6R, with resulting migration of tetrahedral cations to new tetrahedral sites. The new tetrahedra share an edge with the previously occupied tetrahedra. This phenomenon gives rise to a new topology, which coexists to about 40%, with the original one. The new framework consists of a sequence of a novel zeolitic cage (described as a 20-hedron formed by fourteen 6mR and six 4mR) and two consecutive cancrinite cages along [0001]. This topology, which is reported in the database of the hypothetical zeolite structures as 166_2_293, belongs to the ABC-6 family and can be described by the following sequence of 6-rings: ABCBCACAB, to be compared with that of levyne AABCCABBC. In the new topology the extraframework cations are distributed over 3 new sites: one at the center of the 6mR a5 [0001] shared by the two cancrinite cages, one near the center of the 6mR a5 [0001] at the base of the new cage, and a last one in a 6mR window of the new cage. The 8mR bidimensional channel system originally present in levyne is therefore absent in the new topology and hence molecular diffusion is likely to be partially hindered in the dehydrated form. The phase transition is not completely reversible, at least in the short term, as only partial rehydration was demonstrated

Ce-exchange capacity of zeolite L in different cationic forms: a structural investigation

Cerium exchange by microporous materials, such as zeolites, has important applications in different fields, for example, rare earth element recovery from waste or catalytic processes. This work investigated the Ce-exchange capacity of zeolite L in three different cationic forms (the as-synthesized K form and Naand NH4-exchanged ones) from a highly concentrated solution. Chemical analyses and structural investigations allowed determination of the mechanisms involved in the exchanges and give new insights into the interactions occurring between the cations and the zeolite framework. Different cation sites are involved: (i) K present in the original LTL in the cancrinite cage (site KB) cannot be exchanged; (ii) the cations in KD (in the 12-membered ring channel) are always exchanged; while (iii) site KC (in the eight-membered ring channel) is involved only when K+ is substituted by NH4+, thus promoting a higher exchange rate for NH4+ -> K+ than for Na+ -> K+. In the Ce-exchanged samples, a new site occupied by Ce appears in the centre of the main channel, accompanied by an increase in the number of and a rearrangement of H2O molecules. In terms of Ce exchange, the three cationic forms behave similarly, from both the chemical and structural point of view (exchanged Ce ranges from 38 to 42% of the pristine cation amount). Beyond the intrinsic structural properties of the zeolite L framework, the Ce exchange seems thus also governed by the water coordination sphere of the cation. Complete Ce recovery from zeolite pores was achieved

Opposite effect of acute and subchronic treatments with Ferula hermonis on copulatory behavior of male rats

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Dehydration dynamics of levyne: evidence for a new zeolite topology

The thermal induced structural modifications of a natural levyne were studied by both time-resolved synchrotron X-ray powder diffraction between room-T and 800°C, and by conventional-source high- T single crystal X-ray diffraction. Above 230°C, a new topology rises, coexisting in a percentage of about 50% with the original one. The new framework consists of a sequence of a new zeolitic cage (described as a 20-hedron formed by fourteen 6mR and by six 4mR) and two cancrinite cages along [0001]. The new topology – reported in the database of the hypothetical zeolite structures as 166_2_293 – belongs to the ABC-6 family and can be described with the sequence ABABABCBC, to be compared with that of levyne AABCCABBC

La malayaite della Val Vigezzo (Novara)

First occurrence for Italy of well developed crystals of malayaite is reported. Its chemical formula is Ca1.04Sn0.97Si1.01O5. Refined cell parameters from XRPD are a= 7.155(2), b= 8.904(2), c= 6.642, beta= 113\ub02'(2)

Dehydration dynamics of levyne: evidence of a new zeolite topology

The high temperature behaviour of natural zeolite levyne was studied by in situ SR-XRPD. Water loss induces the cation migration toward the framework to obtain a better coordination, forcing the breaking of some T-O-T bridges and the consequent formation of new bonds and of a new structure. The 8mR bidimensional channel system of levyne is absent in the new topology and hence the molecular diffusion should be partially hindered in the dehydrated form

ARCHAEOMETRICAL STUDIES OF ROMAN IMPERIAL AGE GLASS FROM CANTON TICINO.

An archaeometrical study of Roman glass finds recovered in the Canton Ticino area was performed after the finding of traces of possible glass-working at Muralto near Locarno. The aim of this work is to provide chemical characterization of these glass varieties—never analysed before—and to compare the results obtained with those for glass of the same period coming from other sites (Aquileia, Augusta Praetoria and Modena). The chemical data shows that the composition of Canton Ticino glass remained the same from the first to the fourth century AD. Moreover, the large amounts of Sb used as a decolouring agent in these samples represents a peculiar trait

Borosilicate and aluminosilicate pollucite nanocrystals for the storage of radionuclides

Cesium can be encapsulated in crystalline aluminosilicates or borosilicates of ANA framework type byhydrothermal synthesis from alkaline solutions at a temperature as low as 115 \ub0C. No miscibility gap isobserved in the borosilicate\u2013aluminosilicate solid solution. The presence of cesium in the synthesis batchslightly decreases the yield of incorporation of boron in the silicate framework. Nanocrystals from 25 to50 nm are formed in most of the synthesis conditions