Original ArticlesIntercalation of α,ω-Alkyldiamines into Layered α-Titanium Phosphate from Aqueous Solutions
Introduction
α-Titanium phosphate, Ti(HPO4)2·H2O (α-TiP), is a lamellar solid with a basal spacing of 7.6 Å, which presents chemical and structural properties adequate for use as an ionic exchanger [1].
The intercalation of n-alkylamines into layered phosphates has been described as an spontaneous process where every –NH2 group of the organic compound reacts with a hydrogen of the solid forming a stable interaction 2, 3, 4, 5, 6, 7, 8. The reaction was carried out by exposing the solid to the vapour of the alkylamines or in aqueous media with solutions of alkylamines 9, 10, 11.
The intercalation of α,ω-alkyldiamines in layered materials has been studied previously [6]. In the α-zirconium phosphate 12, 13, 14, the intercalation reactions occur stepwise according to the “moving boundary” model, with the formation of a number of intermediate intercalation compounds of formula Zr(HPO4)2·xNH2(CH2)nNH2·H2O (0 < x < 1) before obtaining the fully intercalated phases (x = 1). α-TiP and α-ZrP are isostructural 15, 16, 17. The a and b parameters of the α-TiP unit cell, which determine the dimensions of the layer, are slightly smaller than those of the α-ZrP. This work presents a systematic study of the α-TiP evolution during the intercalation of linear α,ω-alkyldiamines.
Section snippets
Materials
All chemicals were of reagent grade (Aldrich) and used without further purification. α-TiP was synthesized as previously reported by Alberti et al. [18]. The crystalline solid obtained was washed with water until all chloride was eliminated (AgNO3 test), dried at 50°C, and then ground to a particle size of less than 0.03 mm.
Intercalation Procedure
0.5 g of α-TiP was equilibrated for 48 h with 50 cm3 diamine aqueous solutions (1 to 20 meq alkydiamine/g α-TiP) at 25.0 ± 0.1°C following the batch method. Saturated
Intercalation and Hydrolysis Reactions
In alkaline medium, α-TiP can lose HPO42− groups by hydrolytic attack. Fig. 1 shows the hydrolysis degree of the material as a function of the solution pH after the intercalation process. The ratio P/Ti measured from the solid intercalates agrees with the amount of phosphate groups released. At pH < 5.5 the hydrolysis is negliglable and increases in a marked way with increasing pH. This fact must be taken into account when calculating the composition of the solids obtained.
Fig. 2 shows
Conclusions
The intercalation of α,ω-alkyldiamines into α-TiP provides materials formulated as Ti(HPO4)2·NH2(CH2)nNH2·H2O. The reaction takes place with the formation of a monolayer of extended diamine molecules in a trans-trans conformation tilted at an angle of 71° to the phosphate layer. The packing parameters are very close to 1. For lower diamine content intercalation phases the average inclination degree decreases as well as the interlayer distance.
Acknowledgements
We wish to gratefully acknowledge the financial support of CICYT (Spain), Research Project No. MAT94-0428.
References (20)
- et al.
J. Inorg. Nucl. Chem.
(1976) - et al.
J. Inorg. Nucl. Chem.
(1979) J. Inorg. Nucl. Chem.
(1981)- et al.
Mater. Res. Bull.
(1990) - et al.
Solid State Ionics
(1989) - U. Costantino, J. Chem. Soc. Dalton Trans. 402...
- et al.
J. Chem. Soc. Faraday Trans. 1.
(1985) - et al.
Z. Naturforschg.
(1967) - E. Rodrı́guez-Castellón, S. Bruque, and A. Rodrı́guez-Garcı́a, J. Chem. Soc. Dalton Trans. 213...
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