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Description
Technetium-99 (99Tc), a troublesome radioisotope prevalent in nuclear liquid waste, poses significant environmental and human health hazards due to its long half-life, high fission yield, and high environmental mobility. The latter is particularly relevant because, in addition to a fission product in nuclear power plants, the isotope 99mTc is used in radiodiagnostics and is continuously released into the environment in trace amounts. Highly water-soluble pertechnetate (TcO4–) in particular is the dominant species in oxygenated groundwater and thus poses an increased risk. In this work, perrhenate (ReO4−) is used as a non-radioactive surrogate for TcO4− to evaluate sequestration performance under high chloride/nitrate matrix conditions. Hence, 99Tc removal is the subject of extensive research, and various methods have been investigated, including graphene-based materials, layered double hydroxides (LDHs),benzene-aminoguanidinium Ligands, and functionalized metal–organic frameworks (MOFs).In this context perrhenate is particularly interesting as it can serve as a non-radioactive surrogate for pertechnetate.
Here we report on the synthesis of oligo(ethylene glycol) guanidinium salts and their capability for the selective removal of oxoanions form an aqueous environment by precipitation. The exceptionally low water solubility over a wide pH range was exploited to achieve perrhenate removal rates of up to 98%, even in the presence of a high excess of chloride and nitrate ions. Under basic conditions, the synthesized bis-guanidinium salts can be regenerated and used for renewed precipitation of oxoanions. X-ray structural analyses were performed on suitable single crystals and used to derive structure-activity relationship.