Intercalation and grafting of hydrogen phosphates and phosphonates into synthetic hydrotalcites and ac-conductivity of the compounds thereby obtained

A well crystallized Zn-Al-CO3 hydrotalcite-like compound was obtained by co-precipitation of Zn(lI) and Al(III) hydroxycarbonates from 'homogenous solution'. The carbonate was converted into the chloride form via a gas-solid reaction. The chloride ions of the hydrotalcite obtained, Zn0.65Al0.35(OH)(2)Cl(0.35)0.4H(2)O, were then fully exchanged with H2PO4-, HPO42- and C6H5PO3H- anions and the materials produced were characterized for their composition, X-ray diffraction patterns and thermal behaviour. The a.c. conductivity was determined at 100 degrees C, in the 50-90% relative humidity (R.H.) range and in the 30-100 degrees C range at 50% relative humidity. At 100 degrees C and 50% R.H., the a.c. conductivity was found to decrease with the increasing base strength of the intercalated anion, being similar to 10(-5) and similar to 10(-6) S cm(-1) for the H2PO4- and grafted hydrotalcites. A similar trend was observed for the a.c. conductivity of hydrotalcite exchanged with CO32-, SO42-, Cl-, HCOO- and C6H5COO- anions.