A titanosilicate with the ideal formula, Na2Ti2O3SiO4·2H2O, containing unidimensional channels, was synthesized hydrothermally and converted to the hydrogen form by acid treatment. The hydrogen form was partially ion exchanged by sodium ions to obtain a 50% sodium ion exchanged phase. The crystals of the sodium phase, NaHTi2O3SiO4·2H2O, retain the symmetry and unit cell parameters of the parent disodium compound, space group P42/mcm, a = b = 7.832(1) Å, c = 11.945(2) Å, and Z = 4. The sodium ions are located on the ac faces of the crystal while the water molecules occupy the channels. Ion exchange of the acid form by potassium ions leads to a phase with a maximum potassium to proton ratio of about 2. In the acid, H2Ti2O3SiO4·1.5H2O, and potassium phases, K0.5H1.5Ti2O3SiO4·1.5H2O and K1.38H0.62Ti2O3SiO4·H2O, the a and b axes are doubled while the c-axis dimension is retained. These doubled dimensions were transformed to a primitive tetragonal cell which has a volume twice that of the parent sodium form. The crystals belong to the space group P42/mbc with a = 11.039(1) Å, c = 11.886(1) Å for the acid phase, a = 11.015(1) Å, c = 12.017(1) Å for the K1.38H0.62 phase, and a = 11.0604(3) Å, c = 11.9088(3) Å for the K0.5H1.5 phase. The number of molecules in the unit cell in these three cases is 8. In the acid form, the channels are occupied by the water molecules, which are involved in hydrogen bonding among themselves as well as with the framework oxygens. In the K0.5H1.5 phase, all the K+ ions are in the center of the tunnel. For the K1.38H0.62 phase, about 35% of the total potassium ions are located at the center of the channel and are bonded to the silicate oxygens. The remaining ions are found near the framework which is close to the positions of the sodium ions of the ac faces in the parent compound. These ions are bonded to both the framework and water oxygen atoms. The titanium atoms in all the phases are octahedrally coordinated, and they are grouped as clusters of four. These clusters are linked by the silicate groups along the a and b directions and by Ti−O−Ti bonds along the c directions. This structural data provide a basis for explaining the observed ion exchange behavior and ion selectivity.

A novel metastable layered titanium phosphate has been synthesized by the treatment of layered titanates (Na2Ti3O7 and Na4Ti9O20) with 1–2 M phosphoric acid solution at 120–150 °C. Based on the data of 31P MAS NMR and IR spectroscopy, x-ray powder diffraction, and thermal and elemental analysis, the formula Ti2O3(H2PO4)2 · 2H2O was assigned to the novel compound. The layered nature of the compound was confirmed from n-alkylamine intercalation and the ion exchange behavior toward alkali, alkaline earth, and some transition metal ions.

A zirconium trisilicate compound, with composition K(2)ZrSi(3)O(9).H(2)O (1), was prepared under mild hydrothermal conditions and was structurally characterized by using its X-ray powder diffraction data. The compound crystallizes in the space group P2(1)2(1)2(1) with a = 10.2977(2) Å, b = 13.3207(3) Å, c = 7.1956(1) Å, and Z = 4. The asymmetric unit consists of a metal atom, a trisilicate group, and three lattice positions corresponding to two cations and a water oxygen atom. In the structure, the Zr atom is octahedrally coordinated by the six terminal oxygens of the trisilicate group. The trisilicate groups exist as linear chain polymers connected to each other through the Zr atoms. This arrangement leads to channels and cavities in the structure that are occupied by the cations and water molecules. The K(+) ions in compound 1 were exchanged for Cs(+) ions in two steps. In the first case about 50% of the K(+) ions were exchanged to give a compound with composition K(0.9)Cs(1.1)ZrSi(3)O(9).H(2)O (2). Compound 2 was then loaded with additional Cs(+) ions which resulted in a phase K(0.5)Cs(1.5)ZrSi(3)O(9).H(2)O (3). These exchanged phases retain the crystal symmetry of compound 1, but their unit cell dimensions have expanded as a result of large Cs(+) ions replacing the smaller K(+) ions. Structure analyses of the exchanged phases show that the cations found in the cavities of compound 1 are highly selective for Cs(+) ions. A small amount of Cs ions also go to a site in the large channel that is very close to that occupied by the water oxygen in compound 1. In the absence of Cs, this site is filled with water molecules. The second cation found in the channel of 1 is partially occupied by water and K(+) ions. The K(+) ions in compound 1 were completely exchanged for Na(+) ions, and the compound thus obtained, Na(2)ZrSi(3)O(9).H(2)O (4), was treated with Cs(+) ions in a manner similar to that carried out for compound 1. The low Cs(+) ion phase, Na(0.98)Cs(1.02)ZrSi(3)O(9).H(2)O (5), and the high Cs(+) ion phase, Na(0.6)Cs(1.4)ZrSi(3)O(9).H(2)O (6), show ion distributions very similar to compounds 2 and 3 except for the fact that in the Na phases a small amount Cs(+) ion also goes to the second cation site. Compound 1 on heating releases the lattice water and transforms into a hexagonal phase, K(2)ZrSi(3)O(9), corresponding to the mineral wadeite. In the high-temperature phase the silicate group exists as a condensed cyclic group and the K(+) ions are sandwiched between trisilicate groups. A possible pathway for this conversion is also discussed.

New crystalline phases of fibrous titanium(IV) oxophosphates were prepared hydrothermally from titanium(IV) chloride in phosphoric acid solutions. The influence of several factors (concentration of reagents, molar ratio P:Ti in the reaction mixture, and reaction times) was studied. A phase diagram of the system is given. On the basis of elemental and thermal analysis, X-ray powder diffraction, 31 P MAS NMR, and IR spectroscopy, the formula Ti 2 O-(PO 4 ) 2 ‚2H 2 O was assigned to the novel compounds. The new phases (π-TiP and F-TiP) have different structures. The crystal structure of F-TiP was solved from X-ray powder data and was shown to be of the framework type with tunnels parallel to the c-axis direction. The absence of n-alkylamine intercalation processes for both compounds and other physical and behavioral similarities suggests a framework type structure for π-TiP also. The ion-exchange behavior toward alkali and alkaline earth ions was studied.