Synthesis and characterization of a new crystalline tin(IV) arsenophosphate ion exchanger

Abstract

A new crystalline layered inorganic ion exchanger tin(1V) arsenophosphate with the formula Sn(HAs04)(HP04) . H 2 0 has been prepared by refluxing the amorphous precursor. This exchanger has been characterized by X-ray powder pattern, chemical analysis, IR spectra, and thermal dehydration. Its ion exchange behaviour towards sodium ions is reported. The exchanger has an exchange capacity of 5.36 mequiv./g for Na'. The performance of tin(1V) arsenophosphate is compared with crystalline tin(1V) phosphate and arsenate.Key words: cation exchanger, crystalline tin(1V) arsenophosphate, ion exchange, thermal behaviour, X-ray studies. Introduction Over the years efforts have been directed towards synthesizing crystalline inorganic ion exchangers of the type M(1V) (HXO&. H 2 0 (M = tetravalent metal and X = P, As), primarily for a better understanding of their ion exchange reactions (1,2). These materials also have great potential for use as membranes for proton conduction, as superion conductors and as catalysts (1, 3). Crystalline materials are preferred over amorphous exchangers because of their high ion exchange capacity and resistance towards hydrolysis.Every layered material is expected to have its own characteristic behaviour towards diffusion of the counter ions and thermal properties. However, among several known insoluble acid salts of tetravalent metals, a-layered zirconium phosphate (a-ZrP) and its other salt forms have received the maximum attention. In this series of compounds two new mixed layered materials, namely, zirconium-titanium phosphate (4, 5 ) and zirconium arsenophosphate (6) have been synthesized and studied for their ion exchange properties. These mixed salts are reported to be isomorphous with the parent single salts, nevertheless, they do show some variations in ion exchange and thermal a-Zirconium arsenophosphate is obtained in almost complete miscible phases though it contains two anions of different sizes.Ion exchange studies on a-tin(1V) phosphate (a-SnP) and a-tin(1V) arsenate (a-SnAs) (7) reveal that they behave more or less in a similar fashion but in some respects differently from a-ZrP and other similar compounds. Thus, it is of sufficient interest to synthesize crystalline tin(1V) arsenophosphate to determine how the presence of two anions of different dimensions affects the crystalline structure, vis-a-vis the ion exchange and thermal properties of the material. Crystalline tin(1V) arsenophosphate has been synthesized and the reproducibility and chemical stability of the exchanger checked. Its ion exchange behaviour towards sodium ions is reported together

A new electron exchange material Ti(IV) iodovanadate: Synthesis, characterization and analytical applications

“…It is for these reasons, there has been a revolutionary growth in the field of synthetic ion exchange materials [2]. Many studies have been done for their preparation, properties and analytical applications but most ion exchange materials show poor ion exchange capacity and selectivity for metal ions and low thermal and chemical stability [3][4][5][6][7][8][9]. Acidic salts of tetravalent metal ions with the general formula M(IV) (HXO 4 ) 2 ·nH 2 O [where M represents Zr(IV), Ti(IV), Sn(IV), etc.…”