Ion exchangers in radioactive waste management: Natural Iranian zeolites

Five samples of natural zeolites from different parts of Iran were chosen for this study. In order to characterize and determine their structures, X-ray diffraction and infrared spectrometry were carried out for each sample. The selective absorption properties of each zeolite were found by calculating the distribution coefficient (Kd) of various simulated wastes which were prepared by spiking the radionuclides with 131I, 99Mo, 153Sm, 140La and 147Nd. All the zeolite samples used in this study had extremely high absorption value towards 140La; clinoptolite from Mianeh and analsite from Ghalehkhargoshi showed good absorption for 147Nd; clinoptolite from Semnan and clinoptolite from Firozkoh showed high absorption for 153Sm; mesolite from Arababad Tabas showed good absorption for 99Mo; and finally mesolite from Arababad Tabas, clinoptolite from Semnan and clinoptolite from Firozkoh could be used to selectively absorb 131I from the stimulated waste which was prepared. The natural zeolites chosen for these studies show a similar pattern to those synthetic ion exchangers in the literature and in some cases an extremely high selectivity towards certain radioactive elements. Hence the binary separation of radioactive elements could easily be carried out. Furthermore, these zeolites, which are naturally occurring ion exchangers, are viable economically and extremely useful alternatives in this industry.