Synthesis and characterization of the inorganic ion exchanger based on titanium 2-carboxyethylphosphonate
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Synthesis and characterization of the inorganic ion exchanger based on titanium 2-carboxyethylphosphonate Anatoly I. Bortun, Lyudmila Bortun, and Abraham Clearfield Department of Chemistry, Texas A&M University, College Station, Texas 77843
Enrique Jaimez, Mar´ıa A. Villa-Garc´ıa, Jos´e R. Garc´ıa, and Julio Rodr´ıguez Departamento de Qu´ımica Org´anica e Inorg´anica, Universidad de Oviedo, 33071 Oviedo, Spain (Received 10 July 1996; accepted 29 November 1996)
An inorganic ion exchanger based on titanium 2-carboxyethylphosphonate (TiPC) has been synthesized by reaction between solutions of TiCl3 and 2-carboxyethylphosphonic acid at elevated temperature. The solid was characterized by chemical analysis, 31 P MAS NMR, x-ray powder diffraction, IR spectroscopy, and TG analysis. It was found ˚ and that TiPC is a highly crystalline layered solid with the interlayer distance 13.1 A, exhibits a high thermal stability. The intercalation of n-alkylamines and the ion exchange properties of TiPC toward alkali, alkaline earth, and some transition metal cations have been studied. The exchanger shows high affinity to alkaline earth metal cations and some di- and trivalent cations.
I. INTRODUCTION
During the last decades an active research has been undertaken in different laboratories, in order to find new selective ion exchangers and adsorbents. As a result of the intensive work done, a wide variety of synthetic inorganic compounds exhibiting ion exchange properties were found, specifically, metal hydrous oxides, insoluble acid salts of polyvalent metals, heteropolyacids, metal ferrocyanides, etc.1–5 Some of these compounds, due to their high thermal stability, resistance to oxidation and radiation, and good selectivity to certain ions, appear as promising materials capable of operating in extreme conditions (high radiation, temperature, pressure, presence of oxidants and organic solvents, high concentration of background electrolytes, etc.),1,3 in which organic ion exchange resins fail to work efficiently. Moreover, synthetic inorganic ion exchangers, with the exception of silica gel and some zeolites, have not yet found such a wide application as organic resins. This is probably due to the technical problems related to their preparation in granulated form and, also, to the lack of diversity of functional groups. The ion exchange functional groups found in inorganic adsorbents were limited to metal hydroxides, phosphates, arsenates, silicates, sulfides, etc.1,3 Inorganic exchangers containing in their structure –COOH, –SO3 H, or related complexing groups were not reported. In the last two decades the situation has changed drastically after finding a new class of inorganic compounds, namely, layered inorganic oxides or phosphates covalently pillared with organic molecules.6 A great variety of such “mixed” inorganicorganic compounds with different types of functional groups has been synthesized.7–16 A study of their prop1122
http://journals.cambridge.org
J. Mater. Res., Vol. 12,
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