INFLUENCE OF pH ON PHOSPHATE INTERCALATION IN ZINC–ALUMINUM LAYERED DOUBLE HYDROXIDE Mohamed BADREDDINE a , Ahmed LEGROURI b, *, Allal BARROUG a , Andre DE ROY c1 and Jean-Pierre BESSE c2 a Laboratoire de Chimie-Physique, Faculte des Sciences Semlalia, Université Cadi Ayyad, B.P. S15, Marrakech 40001, Morocco b School of Science and Engineering, Al Akhawayn University, B.P. 104, Ifrane 53000, Morocco; e-mail: a.legrouri@alakhawayn.ma c Laboratoire des Materiaux Inorganiques, UPRES-A 6002, Universite Blaise Pascal (Clermont-Ferrand II), 63177 Aubiere-Cedex, France; e-mail: 1 deroy@cfdvs3.univ-bpclermont.fr, 2 jpbesse@chimtp.univ-bpclermont.fr Received June 19, 1997 Accepted January 15, 1998 The exchange of chloride ion by phosphate ions in [Zn–Al–Cl] layered double hydroxide was inves- tigated using X-ray diffraction and infrared spectroscopy. The effects of the pH of the solution con- taining the phosphate ions on the ion exchange was studied. The best sample in terms of crystallinity, was obtained at pH 8. This sample was further characterized by scanning electron microscopy and microanalysis. Key words: Layered double hydroxides; Ion exchange; Hydrotalcite phase; Phosphates. Layered double hydroxides (LDH)s, also called anionic clays or hydrotalcite-like com- pounds 1 , are layered solids which have a stacking of positively charged octahedral sheets. The net positive charge, which is due to substitution of trivalent by divalent metal ions in the brucite-like metal hydroxide M(OH) 2 , is balanced by an equal nega- tive charge of the interlayer solvated anions. The LDH compounds can be represented by the general formula 2 : [M 1-x II M x III (OH) 2 ] x+ [X x/m m- ⋅n H 2 O] x– symbolized by [M II –M III –X], where M II = Mg 2+ , Zn 2+ , Mn 2+ ,…; M III = Al 3+ , Cr 3+ , Fe 3+ ,…; X m– = Cl – , NO 3 - , CO 3 2- , … and x varies between 0.20 and 0.33 (refs 3,4 ). These materials have received considerable attention in recent years due to their potential technological applications in various domains such as catalysis, electrochemistry, separation technology, and medicine 5–11 . This attention results from the layered struc- Layered Double Hydroxide 741 Collect. Czech. Chem. Commun. (Vol. 63) (1998) * The author to whom correspondence should be addressed.