Non-volatile organic analysis of uranium ore concentrates

Abstract

In support of nuclear safeguards and non-proliferation efforts, Oak Ridge National Laboratory is responsible for characterizing uranium ore concentrate (UOC) samples obtained from two ore mining and milling sites. A sorptive extraction method has been developed for analysis of non-volatile organic compounds that might be used to identify characteristics of the purification process by which uranium was separated from these ores. This method utilizes Gerstel Twister® stir bars coated with polydimethylsiloxane to extract organic components from aqueous media. A slurry of UOC is extracted with the Twister® stir bar in 20 % methanol/80 % water containing deuterated internal hydrocarbon standards. Following extraction of non-volatile organics, the Twister® stir bar is analyzed directly in the inlet of a gas chromatograph fitted with a quadrupole mass spectrometric detector. Results have been consistent and have shown excellent recoveries of internal standards, with the average recovery being 97.5 %. Both qualitative and quantitative differences have been identified between the two sources of UOC utilizing this method. One source contained an increased concentration of amines which commonly are used in the recovery and purification of ores. Amines that were identified in this UOC source include dioctylamine, triisoctylamine, and Alamine® 336, a common industrial complexant. Also, when comparing both sources, the same UOC source contained various decanol and C20 compounds. Based on the results from this study, non-volatile organic analysis of UOC using sorptive extraction with Twister® stir bars and GC–MS is a tool that can be used to facilitate sourcing of unknown UOC.