Sorption of trivalent metal ion on fibrous cerium(IV) hydrogenphosphate

Thermodynamics of trivalent metal ions/ hydrogen ions exchange on a fibrous cerium(IV) hydrogenphosphate have been investigated by the micro-amount up take. Selectivities for trivalent metal ions increase in the order; La3+<Y3 +<Eu(3+)much less than Sc3+. The standard enthalpy change and entropy chang e of the ion exchange reaction increase in the order of Eu3+ <La3+ <Y3+ <Sc 3+ and Eu3+ <Sc3+ <La3+ <Y3+, respectively. An enthalpy - entropy compensat ion relation holds except for Sc3+ ion. X-ray diffractometry and thermal an alyses were also conducted the ion-exchanger phase for the macro-amount upt ake. The maximal interlayer spacings were observed around the metal loading of 0.5mmol/g and the weight loss for the adsorbed and interlayer water at the low metal loading increased in the order; Sc3+ <La3+ <Eu3+ <Y3+. In the case of scandium ion, the formation of insoluble scandium phosphate was co nfirmed by the DTA peak at 255 degrees C and characteristic peaks to Sc(PO4 ). 2H(2)O in the XRD pattern.