PREPARATION OF CD AL LAYERED DOUBLE HYDROXIDES AND THEIR INTERCALATION REACTIONS WITH PHOSPHONIC-ACIDS/

Layered double hydroxides(LDHs) containing cadmium as the divalent met al and aluminium as the trivalent metal have been prepared by coprecip itation from a mixed metal nitrate solution, and were obtained with ni trate and carbonate as the counter anions, and as single crystalline p hases. XRD patterns show that these LDHs are isostructural with synthe tic hydrotalcite, with interlayer spacings of 8.24 and 7.54 Angstrom f or Cd/Al/NO3 and Cd/Al/CO3 LDHs, respectively. These compounds were in tercalated with phenylphosphonic acid (PPA) and 2-carboxyethylphosphon ic acid (CEPA). Intercalation is confirmed by XRD, where increased int erlayer spacings were observed for the intercalation compounds. Interl ayer distances of 14.59 Angstrom were observed for the PPA intercalati on compounds, independent of the original counter anion. CEPA intercal ated LDHs present interlayer spacings of 11.74 Angstrom for Cd/Al/CEPA obtained from Cd/Al/NO3 LDH and a double interlayer distance of 11.35 and 12.21 Angstrom for Cd/Al/CEPA obtained from Cd/Al/CO3 LDH. IR and NMR measurements suggest that this double interlayer spacing is due t o the interaction of CEPA to the layers through both of its extremitie s, i.e. a phosphonate and a carboxylate interaction.