Ion-Exchange-Induced Transformation and Mechanism of Cooperative Crystal Chemical Adaptation in Sitinakite: Theoretical and Experimental Study

Abstract

The microporous titanosilicate sitinakite, KNa2Ti4(SiO4)2O5(OH)·4H2O, was first discovered in the Khibiny alkaline massif. This material is also known as IONSIV IE-911 and is considered as one of the most effective sorbents for Cs+ and Sr2+ from water solutions. We investigate a mechanism of cooperative crystal chemical adaptation caused by the incorporation of La3+ ions into sitinakite structure by the combination of theoretical (geometrical–topological analysis, Voronoi migration map calculation, structural complexity calculation) and empirical methods (PXRD, SCXRD, Raman spectroscopy, scanning electron microscopy). The natural crystals of sitinakite (a = 7.8159(2), c = 12.0167(3) Å) were kept in a 1M solution of La(NO3)3 for 24 h. The ordering of La3+ cations in the channels of the ion-exchanged form La3+Ti4(SiO4)2O5(OH)·4H2O (a = 11.0339(10), b = 11.0598(8), c = 11.8430(7) Å), results in the symmetry breaking according to the group–subgroup relation P42/mcm → Cmmm.

The AM-4 Family of Layered Titanosilicates: Single-Crystal-to-Single-Crystal Transformation, Synthesis and Ionic Conductivity

“…The Raman spectra of lintisite with L3 and kukisvumite with K3 forms are shown at Figure 14 a,b, respectively. The Raman data of the AM-4 family compounds have not previously been published and the assignments of the bands were made using analogy with structurally-related titanosilicates [ 8 , 47 , 76 , 77 , 78 ]. In general, the spectra of kukisvumite and lintisite are very close, and differ only by small shifts and in the intensity of different bands.…”

“…The bands at 716 (713), 690, 670 (663) and 627 (627) cm −1 in the lintisite (kukisvumite) spectra and the bands at 711 (708), 671 (683), 658 and 627 (622) cm −1 in the L3 (K3) spectra are mainly attributed to the vibrations of the bridging Si–O–Si linkages of Si 2 O 6 chains [ 80 ]. The bands at 567 (568), 545 s (533), 496 (494 s), 474 (475 s), (468) 437 and 421 (423) cm −1 in the lintisite (kukisvumite) spectra and bands at 569 (563), 532 (528), 497 (494), 475 (470 s), 437 (463) and 418 cm −1 in the L3 (K3) spectra are related to the bending vibrations of Si–O bonds in SiO 4 tetrahedra and different modes of stretching vibrations of Ti–O bonds in TiO 6 octahedra [ 8 ]. The low intensity bands at 379 (382) and 349 (366) cm −1 and relatively intense bands at 325 s (321) and 277 (271, 279) cm −1 plus in the lintisite (kukisvumite) spectra and bands at 379 (376) and 351 w (362), 325 s (319), 277 s (273 s) and 260 cm −1 in the L3 (K3) spectra correspond to the bending vibrations of Ti-O-Si and Ti-O-Ti bonds [ 81 , 82 , 83 ].…”

“…Figure 14a,b, respectively. The Raman data of the AM-4 family com previously been published and the assignments of the bands were m with structurally-related titanosilicates [8,47,[76][77][78]. In general, the spec and lintisite are very close, and differ only by small shifts and in the in bands.…”

“…Ion exchangers are of special interest, especially meso- and microporous zircono-, niobo- and titanosilicates, which in many respects are similar to zeolites, but are more stable in aggressive media [ 3 ]. Such materials are already widely used in industry for applications including extracting radionuclides from liquid radioactive waste (LRW) [ 4 , 5 , 6 , 7 , 8 ], gas separation [ 9 , 10 , 11 ], water treatment [ 12 ], as catalysts [ 13 , 14 , 15 ], nanofiber filters, mineral−organic nanocomposites for drug delivery, bio-sensors, optical filters, materials for electronics, mechanics and other purposes [ 16 , 17 ].…”

A Synthetic Analog of the Mineral Ivanyukite: Sorption Behavior to Lead Cations

“…In contrast to othertitanosilicates discovered in the Khibiny Massif or Lovozero Massif (Kola Peninsula, Russia)-such as lintisite, zorite and sitinakite [2][3][4][5][6][7]-the synthetic of ivanyukite was was known prior to its mineralogical discovery, being obtained by D. Chapman and A. Roe in 1990 [8] under the name name 'grace titanium silicate' (GTS). For their synthesis process, the authors had used Ti(OC 2 H 5 ) 4 as a source of Ti.…”