URANIUM SORPTION FROM AQUEOUS-SOLUTIONS ON SODIUM-FORM OF HEU-TYPE ZEOLITE CRYSTALS

The uranium sorption from aqueous solutions (concentration range 50-20 .000 mg/l) by the sodium-form (Na-form) of HEU-type zeolite crystals ( particle-size < 20 mu m) has been investigated by means of a batch-typ e method. The INAA, RI-XRF, powder-XRF, SEM-EDS and FT-IR techniques w ere used for the study of the experimental products. The absolute uran ium uptake by the material reached the value of 11.68 mg/g in the case of initial concentration 20,000 mg/l. On the other hand the K-d-value s indicated that the relative uranium uptake. and consequently the per centage of removal, is higher for concentrations below 100 mg/l. The u ranium uptake by the zeolite is attributed to different sorption proce sses such as ion-exchange adsorption and surface precipitation, taking place both to the interior and the surface of the crystals and strong ly depending on the pH of the solutions. The investigated zeolitic mat erial was sufficiently resistant at the low initial pH of the solution s with dealumination phaenomena only observed in the case of the most acidic solution used.