Anion-Exchange Reactions of Layered Double Hydroxides: Interplay between Coulombic and H-Bonding Interactions

Abstract

The NO3 −- and Cl−-containing layered double hydroxides (LDHs) of Mg with Al interact weakly with anions in solution under equilibrated conditions and yield a type V isotherm. The uptake of anions under nonequilibrated conditions varies monotonically with the layer charge when the outgoing anion is NO3 −, whereas it goes through a maximum when the outgoing anion is Cl−. These observations suggest that Coulombic interactions play a dominant role in Cl−-LDHs, whereas weak interactions governing the mode of intercalation of NO3 − ions influence the exchange reactions of NO3 −-LDHs. These studies have significant implications for the remediation of insidious anions by LDHs.

Boosting the Supercapacitive Behavior of CoAl Layered Double Hydroxides via Tuning the Metal Composition and Interlayer Space

“…32 Å (with octadecyl sulfate in the interlayer space). Before the insertion of the surfactant moieties, the pristine CoAl−CO 3 LDHs was exchanged to a CoAl−NO 3 form because of the ease in replacing nitrate for other monovalent anions . Afterwards, a family of n ‐alkyl sulfates with increasing number of carbons were exchanged: SO 4 2− , ES − (ethyl sulfate), OS − (octyl sulfate), DS − (dodecyl sulfate) and ODS − (octadecyl sulfate), with 0, 2, 8, 12 and 18 carbon atoms, respectively.…”

Magnetic, Luminescent Eu‐Doped Mg–Al Layered Double Hydroxide and Its Intercalation for Ibuprofen

“…The strong n 3 stretching vibrations (1384 cm À1 ) of interlayer nitrate ions indicates the presence of ibuprofenate and nitrate ions in the LDH gallery. [40] Thermal analysis: The structural stability of the compounds was examined by thermogravimetry as shown in Figure 7. Thermal decomposition of the (Mg 2 Al 1 )-(CO 3 2À ) sample generally proceeded through three typical steps: [41] desorption of the physically adsorbed water molecules and partial interlayer water (27-150 8C), dehydroxylation of the layers (150-250 8C), and decarbonylation of the interlayer carbonate ions (250-550 8C).…”

Effect of Nickel-Containing Layered Double Hydroxides and Cyclophosphazene Compound on the Thermal Stability and Flame Retardancy of Poly(lactic acid)

“…The LDH structure is described with the ideal formula [M II 1−x M III x (OH) 2 ] intra [A m− x/m ·nH 2 O] inter , where M II is a divalent cation and M III is a trivalent cation. A m− denotes an organic or inorganic anion with negative charge m. LDHs have a wide range of applications in many fields, for example, as catalysts or catalyst precursors, 22,23 ion exchangers, 24 adsorbents for environmental contaminants, 25,26 and media for gas diffusion and adsorption. 27,28 The interlayer spacing of LDHs can vary depending on the size of the intercalated anions.…”