The volatilization of iodine species over dilute iodide solutions

Iodine immobilization by materials through sorption and redox-driven processes: A literature review

Radioiodine-129 (¹²⁹I) in the subsurface is mobile and limited information is available on treatment technologies. Scientific literature was reviewed to compile information on materials that could potentially be used to immobilize ¹²⁹I through sorption and redox-driven processes, with an emphasis on ex-situ processes. Candidate materials to immobilize ¹²⁹I include iron minerals, sulfur-based materials, silver-based materials, bismuth-based materials, ion exchange resins, activated carbon, modified clays, and tailored materials (metal organic frameworks (MOFS), layered double hydroxides (LDHs) and aerogels). Where available, compiled information includes material performance in terms of (i) capacity for ¹²⁹I uptake; (ii) long-term performance (i.e., solubility of a precipitated phase); (iii) technology maturity; (iv) cost; (v) available quantity; (vi) environmental impact; (vii) ability to emplace the technology for in situ use at the field-scale; and (viii) ex situ treatment (for media extracted from the subsurface or secondary waste streams). Because it can be difficult to compare materials due to differences in experimental conditions applied in the literature, materials will be selected for subsequent standardized batch loading tests.

Mechanochemically synthesized mesoporous alumina: An advanced sorbent for post-processing concentration of 131I for cancer therapy

High radioactive concentration of ¹³¹I in the form of ¹³¹I[NaI] solution is essential for preparation of large-dose therapeutic capsules used in the management of thyroid cancer. In this communication, we report the synthesis of mesoporous alumina sorbent (surface area = 292 ± 28 m²/g, mean pore diameter = 6.8 ± 0.7 nm) by a novel solid state mechanochemical approach and its utilization in post-processing concentration of ¹³¹I. The overall yield of ¹³¹I after the concentration procedure was >90% and ¹³¹I[NaI] solution could be obtained with appreciably high (1.7 TBq/mL) radioactive concentration, suitable for use in nuclear medicine. The promising results obtained in this study would stimulate greater utilization of this new class of sorbents in sample preparations by solid phase extraction procedures for societal benefits.

Translocation of (125)I, (75)Se and (36)Cl to edible parts of radish, potato and green bean following wet foliar contamination under field conditions

Specific translocation factor values (ftr) for (129)I, (79)Se and (36)Cl following foliar transfer are still missing from the IAEA reference databases. The translocation of the short-lived isotopes, (125)I, (75)Se, and (36)Cl, to radish, potato and green bean edible parts was measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors obtained for (125)I ranged from 0.8 to 2.6% for radish, from 0.1 to 2.3% for potato and from 0.1 to 2.6% for bean. The translocation factors obtained for (75)Se ranged from 6.3 to 21% for radish, from 1.6 to 32.6% for potato and from 7.7 to 22.8% for bean (values similar to Cs or even higher). The translocation factors obtained for (36)Cl were close to those for (75)Se and ranged from 4.3 to 28.8% for radish, from 0.5 to 31.5% for potato and from 4.3 to 16.3% for bean. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount was probably volatilized. Selenite internal transfer was significant and possibly followed the sulfur metabolic pathway. Chloride was very mobile and quickly diffused throughout the plant. The translocation factors varied with the growth stage and depended on the development state of the edible tissue and its associated sink strength for nutrients and assimilates. For radish, translocation was high during the early vegetative stages. For potato, wheat and bean, a major peak in translocation was seen during the flowering growth stage and the concomitant growth of potato tubers. An additive effect of successive contamination events on translocated elements was shown in radish but not in bean and potato. The highest translocation value obtained for an acute contamination event was shown to be an adequate, conservative indicator of chronic contamination in absence of specific values. Due to the absence of rain leaching during the experiment this study probably provides translocation values among the highest that could be recorded.

Translocation of 125I, 75Se and 36Cl to wheat edible parts following wet foliar contamination under field conditions

Apart from radiocaesium and radiostrontium, there have been few studies on the foliar transfer of radionuclides in plants. Consequently, specific translocation factor (ftr) values for (129)I, (79)Se and (36)Cl are still missing from the IAEA reference databases. The translocation of short - lived isotopes, (125)I and (75)Se, and of (36)Cl to wheat grain were measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors ranged from 0.02% to 1.1% for (125)I (a value similar to Sr), from 0.1% to 16.5% for (75)Se, and from 1% to 14.9% for (36)Cl. Both (36)Cl and (75)Se were as mobile as Cs. The phenomenological analysis showed that each element displayed a specific behavior. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount probably volatilized. Selenite internal transfer was significant and possibly utilized the sulphur metabolic pathway. However bio - methylation of selenite may have led to increased volatilization. Chloride was very mobile and quickly diffused throughout the plant. In addition, the analysis underlined the importance of plant growth responses to annual variations in weather conditions that can affect open field experiments because plant growth stage played a major role in ftr values dispersion. The chronic contamination results suggested that a series of acute contamination events had an additive effect on translocated elements. The highest translocation value obtained for an acute contamination event was shown to be a good conservative assessment of chronic contamination if data on chronic contamination translocation are lacking. The absence of rain leaching during the experiment meant that this investigation avoided potential radionuclide transfer by the roots, which also meant that radionuclide retention on or in the leaves was maximized. This study was therefore able to obtain accurate translocation factors, which are probably among the highest that could be recorded.

Uptake and depuration of 131I by the macroalgae Catenella nipae--potential use as an environmental monitor for radiopharmaceutical waste

A study was initiated to establish the suitability of the macroalgae, Catenella nipae as an environmental surveillance monitor for radiopharmaceutical waste discharges to aquatic environments. A series of experiments were conducted to establish the radioactive iodine ((131)I) concentration factor, and uptake and depuration characteristics of C. nipae. The steady state concentration factor was estimated to be 630+/-80 mL g(-1), with an uptake half-time of 160+/-20 min. Elimination of (131)I was found to follow a two phase model, the first having a rapid elimination rate with a half-time of <1 min, followed by the second phase with a half-time of 3.2 days. Application of the Michaelis-Menton model allowed calculation of an estimate for activity concentration of (131)I in environmental waters from C. nipae sampling devices in the Brisbane River estuary, Australia. The results suggest that C. nipae may be used as an environmental radioactive waste sentinel.