Technitium-99 (99Tc) is a primary fission product of 235U, 233U, and 239Pu and is a major constituent of radioactive waste. 99Tc is commonly found as pertechnetate (TcO4-), an anion that does not readily adsorb to natural sediment and is extremely mobile in environmental water systems. With concerns that radioactive waste may be leaking from sub-surface storage tanks and potentially reaching groundwater, developing detection methods for TcO4- is important. Rhenium (Re)/perrhenate (ReO4-) has been identified as a nonradioactive surrogate for Tc/TcO4-. Electrochemical detection offers several advantages for detection due to its low cost, capability to be miniaturized, and ease of use. However, a simple electrochemical technique like anodic stripping voltammetry (ASV) for ReO4- or TcO4- has not been fully investigated. This is likely due to the extreme cathodic potential needed for the deposition step. In this work, we use ASV with a boron-doped diamond (BDD) electrode for the detection of ReO4-. BDD has a wide electrochemical potential window, enabling the deposition of ReO2 for ASV. Control studies included optimization of the deposition potential and time as well as several calibration experiments. The optimal parameters for this work were a -1.9 V deposition potential at a deposition time of 5 min. A calibration curve ranging from 1 µM-100 µM of ReO4- at the optimal parameters showed two linear ranges from 1-10 µM and 15-100 µM. Their respective R2 values were 0.985 and 0.987. The 1-10 µM linear range had a limit of detection (LOD) below 1 µM. Greater sensitivity was exhibited in the 15-100 µM range. Comparative studies were completed on glassy carbon (GC) but it was severely outperformed by the BDD. These values illustrate a possibility of applying ASV with BDD for TcO4- in future work, and a potential detection platform to ensure safety at radioactive waste storage sites.

Anodic stripping voltammetry of perrhenate and pertechnetate on boron-doped diamond

ACS Spring 2022

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