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 tripotassium tris-(oxalato) fen-ate(III) trihydrate, K3Fe(C2O4)(3) . 3H(2)O (referred to hereafter as Fe(Ox)(3)) and the layered double hydroxide (LDH) 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 diffraction studies (PXRD) indicated that the reaction products were all amorphous and microcrystalline. The polyphasic nature of the reaction products (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 of 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 products. Simultaneous thermogravimetric analyses (TG) and differential thermal 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. The mechanism for intercalation was thought to involve the removal of the LDH interlayer carbonate and water molecules in a similar manner to that observed in LDH-[organic acid] thermal reactions. (C) 1998 Elsevier Science B.V. All rights reserved.