Vibrational Spectral Analysis of Natisite (Na2TiSiO5) and its Structure Evolution in Water and Sulfuric Acid Solutions

Abstract

Natisite (Na2TiSiO5) is a layered sodium titanosilicate containing TiO5 square pyramids. The structure evolution of natisite in water and acid solutions is the basis for its potential applications. With Na2SiO3 as the silicon source, natisite with the shape of the square sheet was selectively prepared from the hydrothermal method with 14.3 mol/L NaOH solution at 240 °C. Natisite has 20 Raman active modes and 22 infrared active modes from the first-principles calculations within density functional theory, and the calculated Raman and infrared spectra agree well with the experimental ones. The characteristic Raman peak at 844 cm−1 is caused by the symmetric stretching of the apical Ti–O bond in the TiO5 unit, assigning to A1g and B2g modes. Natisite remains relatively stable in water with a sodium leaching percentage of lower than 6%. When washing with sulfuric acid solutions, the interlayer spacing of natisite is reduced due to the extensive removal of sodium ions, and an intermediate composed of SiO4 and newly formed TiO6 units may be formed. Moreover, after washing with water and acid solutions, 95.5%, 63.4%, and 35.2% of Na, Si, and Ti in natisite can be leached in total, respectively, resulting in the structural disintegration of natisite.

New Approaches for Pb(II) Removal from Aqueous Media Using Nanopowder Sodium Titanosilicate: Kinetics Study and Thermodynamic Behavior

“…The FTIR spectrum recorded in the range of 400-2000 cm −1 (Figure 3) for the Na2TiSiO5 nanopowder is in correlation with literature data [17,30]. The major absorption bands correspond to the asymmetric and symmetric stretching vibrations (at 850.6 cm -1 assigned to the asymmetric stretching of Ti-O-Ti bridges, at 912.2 cm −1 assigned to the asymmetric stretching of Si-O-Ti bridges and at 576.2 cm −1 assigned to the asymmetric stretching of Si-O-Si bridges [17,19,30,31]. The XRD spectra permitted the röntgenographic deceleration of the Na 2 TiSiO 5 by its specific interference at 2.86 Å, 3.30 Å, and 1.77 Å and indexing of additional low-angle reflections-110, 101, 200, 002, 211, 220, and 301 (JCPDS 01-086-1615) [26][27][28][29].…”

“…The FTIR spectrum recorded in the range of 400–2000 cm −1 ( Figure 3 ) for the Na 2 TiSiO 5 nanopowder is in correlation with literature data [ 17 , 30 ]. The major absorption bands correspond to the asymmetric and symmetric stretching vibrations (at 850.6 cm −1 assigned to the asymmetric stretching of Ti–O–Ti bridges, at 912.2 cm −1 assigned to the asymmetric stretching of Si–O–Ti bridges and at 576.2 cm −1 assigned to the asymmetric stretching of Si–O–Si bridges [ 17 , 19 , 30 , 31 ].…”

“…This can be carried out by transferring the heavy metal ions from the aqueous media to the solid phase via the adsorption process [ 17 ]. A strong affinity between the solid phase and the targeted metal ions is required in order to bind them irreversibly under ambient conditions; at the same time, it is important to have the ability to release them under different conditions, so that it can be regenerated for further use [ 18 , 19 , 20 , 21 , 22 ]. Some different solid phases have been found useful in the removal of heavy metals from aqueous media, such as metal oxides, activated carbons, clay minerals, biosorbents, and zeolites [ 7 , 21 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ].…”

“…AM-1 is the first member of the group and sodium titanosilicate, Na 2 TiSiO 5 is one of the compounds included in the group. It is known that the Na 2 TiSiO 5 has three polymorphic modifications, two tetragonal and one orthorhombic [ 18 , 19 ]. Titanosilicates materials with their framework and layered structures have the highest adsorption potential and a high ion-exchange rate.…”