Preparation of Cd/Al layered double hydroxides and their intercalation reactions with phosphonic acids

Abstract

Layered double hydroxides (LDHs) containing cadmium as the divalent metal and aluminium as the trivalent metal have been prepared by coprecipitation from a mixed metal nitrate solution, and were obtained with nitrate and carbonate as the counter anions, and as single crystalline phases. XRD patterns show that these LDHs are isostructural with synthetic hydrotalcite, with interlayer spacings of 8.24 and 7.54 Å for Cd/Al/NO 3 and Cd/Al/CO 3 LDHs, respectively. These compounds were intercalated with phenylphosphonic acid (PPA) and 2-carboxyethylphosphonic acid (CEPA). Intercalation is confirmed by XRD, where increased interlayer spacings were observed for the intercalation compounds. Interlayer distances of 14.59 Å were observed for the PPA intercalation compounds, independent of the original counter anion. CEPA intercalated LDHs present interlayer spacings of 11.74 Å for Cd/Al/CEPA obtained from Cd/Al/NO 3 LDH and a double interlayer distance of 11.35 and 12.21 Å for Cd/Al/CEPA obtained from Cd/Al/CO 3 LDH. IR and NMR measurements suggest that this double interlayer spacing is due to the interaction of CEPA to the layers through both of its extremities, i.e. a phosphonate and a carboxylate interaction.

Synthesis and Thermal Decomposition of Mn–Al Layered Double Hydroxides

“…On the other hand, the use of the combination of various divalent and trivalent metal ions was reported for the synthesis of new M 2+ -M 3+ LDHs (15)(16)(17)(18)(19)(20)(21)(22) (24). The Ni-Mn LDH was synthesized, in which the added Mn 2+ was oxidized to Mn 3+ under alkaline condition during the synthesis of LDH (25).…”

Review of the synthesis of layered double hydroxides: a thermodynamic approach

“…The non-anion exchange methods include the delamination-restacking method 27 and LDH reconstruction method [28][29][30][31][32][33][34] . Metals that have been reported as constituents of LDH layers as well as some claimed in patents 9,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] are shown in Figure 1.…”

Probing the interaction between di- and tri-functionalized carboxy-phosphonic acid and LDH layer structure

“…The absence of this band for all the hybrid compounds is an indication of the formation of PO 3 2À groups which present some ionic interactions with the positive layers [26]. We observe the other characteristic bands of phosphonate groups (PO 3 2À ) in the 1000-1200 cm À1 region [24][25][26][27][28].…”