Radiochimica ActazvutsponmihgecaWTSA 66/67, 129-131 (1994) © R. Oldenbourg Verlag, München 1994 Applications of Functionalized Azaphosphanes as Novel Scavenging Agents for Tc0 4 By Kattesh V. Katti*· Prahlad R. Singh"- b , Kavita K. Katti", Wynn A. Volkert a ' b c and Alan R. Ketring" * Department of Radiology, Center for Radiological Research, b Missouri University Research Reactor, University of Missouri-Columbia and c Research Service, H. S. Truman Memorial VA Hospital, Columbia, Missouri, USA Technetium-99 / Scavenging / Azaphosphanes / Waste management A bstract Azaphosphanes functionalized with different organic substitu- ents have been shown to selectively scavenge T c O j in the presence of different concentrations of anions (NOi, Cl~, OH") and cations (Pd 2+ , Pt 2+ , Fe 3+ ). The fundamental coordination chemistry of the azaphosphane-based ligand systems with Re included detailed NMR spectroscopic and X-ray structural in- vestigations which has provided important insights that may aid in the application o f new azaphosphane ligands for scavenging specific transition metals. The aforementioned studies, clearly show the potential for the application o f this new class of main group monomers and polymers in the treatment of liquid wastes containing " Tc 0 4 for use in waste management procedures. Introduction Remediation of radioactive waste is of prime impor- tance since it is recognized by the public as one of the leading environmental issues of our time. The problem extends to a wide diversity o f radioactive contaminants in various forms, including ground water and storage solutions containing various solvents. While removal of a variety of radioisotopes from waste streams in the environment is essential, removal o f techne- tium-99 ("Tc) is considered to be one of the most im- portant factors since it makes up a significant portion o f the radioactive nuclides remaining in radioactive wastes after decay periods of hundreds of years [1, 2], Therefore, there is world-wide concern about the environmental contamination of "Tc. Considerable quantities o f "Tc have been accumulated and are being produced in nuclear reactors in amounts equaling ap- proximately 1 kg per ton o f uranium. Approximately 10% of the mass of the fission products are made up of "Tc since fission yield is 6.13% [2, 3]. Although the radiotoxicity of "Tc is not extremely high, it poses a major concern because of its long half-life (2.13 zyxwvutsrqponmlkjihgfedcbaWVUTSRPONMLKIHFEDCBA Χ10 5 years). For the aforementioned reasons, a major goal is to limit the discharge of "Tc to the lowest possible level. * Address and Author for correspondence: Dr. Kattesh V. Katti, Center for Radiological Research, University o f Missouri, Allton Building Laboratories, Room 106, 301 B. Loop 70 West, Columbia, MO 65203. Consequently it is essential to develop efficient meth- ods to remove "Tc from a variety of vehicles, ranging from high-level liquid wastes to low levels of radio- activity in ground water. Central to the discovery of new and efficient tech- nologies for the removal of "Tc from various media is the development of the fundamental coordination chemistry of technetium and related elements. It has been recognized that TcC>4 is one of the most stable and unreactive forms of Tc. This chemical form of technetium is very mobile and exhibits little interac- tion with inorganic species in the geosphere [4]. How- ever, reduced forms of "Tc (for example, Tc(IV) or Tc(V)) may be strongly absorbed and exhibit minimal migration. Even though the oxidation of "Tc 0 2 (a major chemical found in spent reactor fuel) to "TCO4 in aerobic aqueous media is relatively slow, over many years a large percentage will be converted to "TcO^ [1, 2]. The task of removing technetium as "TcO^ with a high degree of efficiency and selectivity is for- midable but also quite critical. In this context we have explored the possibility of using phosphinimine-based ligands (e.g.; R3P=N-SiMe 3) for the selective scav- enging of technetium as "TCO4. This choice of phos- phinimine class of ligands is based on the fact that these ligands can donate 1, 2 or up to 4 electrons to most early transition metals to stabilize the metal com- plexes in their high/ highest oxidation states [5—11], M aterials and methods All chemicals were obtained from Aldrich Chemical Company and all reagents and solvents were o f re- agent grade. Technetium-99m ( T c ) was eluted from a "Mo/ 99m Tc radionuclide generator (Mallinckrodt, Inc.). Scavenging of w,n Tc04 with Ph3P=N-SiMe3 Between 1—5 ml of organic solvents (i.e., CHC1 3 , CH2 C1 2 , CCL,, THF or toluene) containing Ph3P=NSiMe3 (0-100 mg/ ml) were mixed with 1 - 5 ml of aqueous solutions containing approximately 3.7 MBq (0.1 mCi) of TcC>4 and other anions. "™Tc04 was obtained from a " M o / T c generator supplied by Mallinckrodt Medical, Inc. For the par- 143 Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/29/15 7:15 AM