Synthesis characterisation and applications of some inorganic ion exchangers

Abstract

Recently, the interest in inorganic ion-exchangers has been revived with the need for the separation of ionic components in radioactive wastes at high temperatures. Inorganic ion-exchangers are the only materials that can be used for such applications due to their high selectivity and remarkable stability against high radiation levels. Inorganic ion-exchangers based on tin(lV) and zirconium have been synthesized, characterised and studied for their analytical applications. Due to better ion-exchange characteristics, double salts of zirconium Le., zirconium antimonophosphate and zirconium phosphotungstate are being reported as novel materials with good ion exchange characteristics. Synthetic procedures have been optimized to prepare good quality lon-exchangers possessing workable particle geometry, chemical and thermal stabHities. These ion-exchangers have been characterised as weakly acidic ion exchangers Studies like ion-exchange capacity for alkali and alkaline earth metal ions, distribution coefficients for a number of metal ions, effect of heat treatment on ion-exchange capacity, chemical composition, thermal and chemical stabilities have been done on the newly synthesized ion-exchangers. Structural studies of these materials and some of those prepared earlier like tin (IV) antimonoarsenate have been carried out with the help of X-ray powder patterns, Infrared analysis and response to thermal treatment upto 900quot C. Analysis of the X - ray diffractograms of tin(IV) antimonoarsenate reveals that crystaUinityof the ion-exchanger is due to weak Vanderwaals forces holding the structure in shape, because of the reason that the structures lose crystallinity when subjected to a temperatute as low as 60quot C. A decrease in the crystalline character continues upto 300quot C and at 600quot C, reorientation of the structure is observed. Exchange kinetic studies have been done on one of these ion. exchangers to understand the exchange reaction mechanism.