Reaction condition effects on Re(VII) sorption kinetics at the zerovalent iron-water interface

Rhenium;Zero valent Iron

Lenell, Brian Angelo ; Arai ; Yuji

关键词: Rhenium;    Zero valent Iron;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/90875/LENELL-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Long lived technetium-99 (99Tc) (t1/2: 2.1 x 105 yr) is one of the major radionuclide risk drivers in low level radioactive waste (LLW) at U.S. Department of Energy sites. Cementitious waste technology (CWT)is presently being used to immobilize LLW. Blast furnace slag is presently being added to the CWT formulation to promote reductive precipitation of the dominant risk driver, pertechnetate, 99Tc(VII)O4- to the sparing soluble 99Tc(IV). Some previous studies show that a variety of hazardous elements immobilized by slag can still remain mobile and leach out of the cement systems. Therefore, use of additional reducing agents should be tested. Because LLW is in caustic brine (high nitrate) solutions, it is a challenging task to reduce 99Tc(VII)O4-. This study evaluated the reducing capacity of zero valent iron (ZVI) as a potential reducing agent in the CWT. Using perrhenate (Re(VII)O4-) as a chemical analogue for 99Tc(VII)O4-, batch Re(VII) sorption experiments were conducted in ZVI as a function of pH (8.2-10.2) and nitrate concentration (0-0.1M). Zero valent iron was effective in reducing Re(VII) to Re(IV), and the initial (< few hrs.) Re sorption was rapid at the ZVI-water interface followed by a slow uptake. Although the extent of Re sorption decreased with increasing pH and nitrate concentration, ZVI immobilized Re(VII) by as much as 10% at pH 10.2. The results suggest that ZVI can be a potential reducing agent to improve the performance of CWT to immobilize 99Tc(VII)O4-.