โ Scribed by G. Alberti; M. Casciola; U. Costantino; M.L. Luciani
No coin nor oath required. For personal study only.
Titration curves of fibrous cerium(IV) phosphate with alkali and alkaline earth metal ions show that the ion-exchange processes occur without phase transition. The exchanger displays a wide range of acidities like an amorphous or semi-crystalline material. About 30 ok of exchangeable protons are much more acidic than the others. In these sites, the exchanger prefers counter ions that have a large ionic radius, while several inversions occur at high metal ion loadings. Furthermore, the shapes of the Na+/K' and Na+jCs+ isotherms also indicate that there are about 30 % of sites where the counter ions that have the largest ionic radius are preferred. Separations factors and Kd vaiucs for various cations at difhercnt concentrations have been determined and a marked selectivity for Pbzi, Ba'+, Ag" and Tit has been found. The selectivity for Pbzi was investigated for the full range of Composition of the exchanger and the Hf,4Wi isotherm was obtained. The unusual selectivity of fibrous cerium(IV) phosphate for certain cations should lead to some useful practical applications. The batch anaiytical separation of Ca*+-PW+ at low pH values has shown that Pb'+ is selectively exchanged aIso in presence of large amounts of Cat+.
In a previous paper in this seti&, the syntheses, chemical composition, X-ray powder diffraction patterns and some ion-exchange properties of c&urn(W) phosphates of various crystalhnities were described. One of these materials was found to have a defmite chemical composition (CeO, -P205 -4&O),
and a fibrous structure. The chemical formula of-the anhydrous product is CefHPO~),, while the formula Ce(HPO&-3&O was suggested for the hydrated product. This formula has recently been supported by infrared spectrosc~py'*~ and is in good agreement-with the experimental ion-exchange capacity (5.2 mequiv./g, that is, two exchangeable protons per formula-weight). Herman and Ctedrfidd4 recently reported the synthesis of a sim-
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Some investigations on the preparative procedure of fibrous thorium phosphate are reported. This new inorganic ion exchanger has been characterized on the basis of chemical analysis, thermal stability and ion-exchange properties with alkali metal ions. The ion-exchange capacity for Na+ is 3.7 mequiv