Iodine sorption capacity and retention stability under gamma-irradiation:A comparative study on silver-impregnated zeolite and pristine zeolite
Gunjan Verma, Deepak Tyagi, Nicy Ajith, Devanshu Das, Ashok Kumar Sahu, K. Umadevi, K. K. Swain, Salil Varma, P. A. Hassan, A. K. Tyagi
Abstract
In this study, we aimed to investigate the iodine uptake capacity of silver-impregnated zeolite (Ag 0 -zeolite) prepared with 8.5 % (w/w) silver content as compared to pristine zeolite and evaluated their iodine retention capability under gamma radiation exposure. The silver and iodine estimation in zeolite matrix were carried out by PXRD , EDS and INAA . The kinetics studies indicated a faster rate of iodine sorption in Ag 0 -zeolite as compared to pristine zeolite. The iodine uptake capacity of Ag 0 -zeolite was found to be almost 5.8 times higher than that of pristine zeolite by gravimetric measurements. Further, in Ag 0 -zeolite, a significant enhancement in iodine sorption was observed at 100 °C as compared to 30 °C. The INAA on iodine loaded Ag 0 -zeolite after removing loosely bound iodine showed the presence of ∼100 mg/g adsorbent of iodine majorly in the form of silver iodide . The stability of entrapped iodine in Ag 0 -zeolite/zeolite matrix was evaluated after irradiating the samples under gamma radiation over a period of 6 months at a dose rate of 1 Gy/h (total dose 4.32 kGy). A small amount of iodine desorption was observed from Ag 0 -zeolite/zeolite, which could be attributed to removal of physically adsorbed iodine from the matrix as no sign of disintegration of silver iodide was detected in the post irradiated samples. The physicochemical characterization indicated no noticeable changes in crystal structure, morphology and chemical state of silver/iodine upon gamma exposure. Overall, the study suggested that gamma irradiation didn’t change the physicochemical characteristics as well as iodine retention properties of developed Ag 0 -zeolite.