A THERMAL-DECOMPOSITION STUDY ON THE INTERCALATION OF TRIS-(OXALATO)FERRATE(III) TRIHYDRATE INTO A LAYERED (MG AL) DOUBLE HYDROXIDE/

The present study details the results of the reaction between tripotas sium tris-(oxalato) fen-ate(III) trihydrate, K3Fe(C2O4)(3) . 3H(2)O (r eferred to hereafter as Fe(Ox)(3)) and the layered double hydroxide (L DH) of initial composition Mg6Al3.4(OH)(18.82)(CO3)(1.51) (NO3)(0.36) . 4.5H(2)O via a conventional ion-exchange process. Powder X-ray diffr action studies (PXRD) indicated that the reaction products were all am orphous and microcrystalline. The polyphasic nature of the reaction pr oducts (as evidenced by PXRD) was thought to derive from the presence, in all cases, of the tris-(oxalato) ferrate(III) complex both on the surface of individual crystallites and within the interlayer regions o f the LDH host. In addition some residual LDH host may also be present which was thought to add to the polyphasic nature of the reaction pro ducts. Simultaneous thermogravimetric analyses (TG) and differential t hermal analyses (DTA) for the reaction products of the suggested that the tris-(oxalato) ferrate(III) complex intercalated intact, but with the loss of the water of crystallisation and potassium counter ions. T he mechanism for intercalation was thought to involve the removal of t he LDH interlayer carbonate and water molecules in a similar manner to that observed in LDH-[organic acid] thermal reactions. (C) 1998 Elsev ier Science B.V. All rights reserved.