Comparative Structural, thermodynamic and electronic analyses of ZnAlAn− hydrotalcite-like compounds (An−Cl−, F−, Br−, OH−, CO32− or NO3−): An ab initio study

Anion Selectivity of Layered Double Hydroxides: Effects of Crystallinity and Charge Density

“…[38,39] NO 3 -ions in the interlayer space in a flat orientation at a high Mg/Al ratio would be in a highly stabilized state due to their preferable size and the strong interaction among NO 3 -ions, the LDH host layers, and interlayer water. That interaction would be similar to hydrogen bonds, as suggested in simulation studies, [20] and the shape and size of the NO 3 -anion would significantly affect such an interaction.…”

“…This is the reason why different selectivities for NO 3 -were reported previously. [19][20][21][22][23][24][25][26][27][28] In the literature, the interlayer space of LDHs containing NO 3 -decreases when the Mg/Al ratio exceeds 3 (d 003 changes from about 0.90 nm to about 0.80 nm), [33][34][35][36] and a computational calculation shows that NO 3 -ions change their orientation from tilted to flat when the Mg/Al ratio exceeds 3. [36] When the Mg/Al ratio is greater than 3, electrostatic interactions may not be strong enough to intercalate bulky ions such as the SO 4 2-ion preferentially.…”

“…[9,10,[13][14][15][16][17][18] However, the selectivity of LDHs for nitrate is generally considered not to be high, and a large number of studies have reported that anions with a higher charge density tend to be more preferentially intercalated into LDHs. [6][7][8]19,20] According to a report by Miyata, [19] the order of exchange selectivity for monovalent anions in the case of Mg-Al LDHs (Mg/ Al = 2.3) is OH -> F -> Cl -> Br -> NO 3 -> I -, and according to a report by Costa et al, [20] the order of exchange selectivity based on a computational simulation with Zn-Al LDHs (Zn/Al = 2) is CO 3 2-> OH -> F -> Cl -> Br -> NO 3 -. It is therefore very questionable whether LDHs could be used as nitrate adsorbents.…”

Theoretical studies of the interaction of terephthalate anion in MgAl-layered double hydroxides

“…In this work ab initio calculations were done to provide a clear and more detailed picture of the arrangements of TA in the interlayer region and the interaction between the anion and the hydroxyl layers as the charge layer increases. This work is grounded in previous theoretical works based on DFT of layered materials produced recently (Costa et al, 2008), (Costa et al, 2010), (Costa et al, 2011), (Costa et al, 2012a), (Costa et al, 2012b), (Vaiss et al, 2009), (Vaiss & I., B. J., Leitão, A. A., 2011), (Vaiss et al, 2013).…”

Theoretical study of the anion exchange properties and the thermal decomposition of Zn5(OH)8(NO3)22H2O and Zn5(OH)8(NO3)22NH3

“…Therefore, the interlayer anion and intermolecular interactions in those hydrotalcite-like compounds were studied and it could be concluded that the anionic hydration plays a major role in the structure stabilization (Costa et al, 2012a(Costa et al, ,2012b. In the present work, we extend the use of this methodology to investigate some thermal features of Zn 5 (OH) 8 (NO 3 ) 2 •2H 2 O and Zn 5 (OH) 8 (NO 3 ) 2 •2NH 3 such as dehydration and ZnO formation and the anion exchange thermodynamics of Zn 5 (OH) 8 (NO 3 ) 2 •2H 2 O with fluoride, chloride, bromide and iodide.…”