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Arai, Yuji Lenell, Brian Angelo 2016-07-07T21:14:26Z 2016-07-07T21:14:26Z 2018-07-08T09:15:33Z 2016-03-25 2016-05 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-. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01 The student, Brian Lenell, accepted the attached license on 2016-03-24 at 13:23. The student, Brian Lenell, submitted this Thesis for approval on 2016-03-24 at 13:28. This Thesis was approved for publication on 2016-03-25 at 10:09. DSpace SAF Submission Ingestion Package generated from Vireo submission #9120 on 2016-07-07 at 14:16:19 Made available in DSpace on 2016-07-07T21:14:26Z (GMT). No. of bitstreams: 2 LENELL-THESIS-2016.pdf: 2452635 bytes, checksum: 3c68aa6874ede8d506c6c4feeed704bf (MD5) LICENSE.txt: 4209 bytes, checksum: b602197ad4663853d6ecd6d2b95c0395 (MD5) Previous issue date: 2016-03-25 Embargo set by: Seth Robbins for item 93229 Lift date: 2018-07-07T21:14:52Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Embargo set by: Seth Robbins for item 93229 Lift date: 2018-07-07T21:18:16Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Limited Restriction Lifted for Item 93229 on 2018-07-08T09:15:33Z. application/pdf http://hdl.handle.net/2142/90875 en Copyright 2016 Brian Lenell Rhenium Zero valent Iron Reaction condition effects on Re(VII) sorption kinetics at the zerovalent iron-water interface text text Natural Res & Env Sci Natural Res & Env Sciences University of Illinois at Urbana-Champaign Thesis M.S.