Electrochemical Oxidation of Terbium(III) in Aqueous Carbonate Solutions

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Radiopharmaceuticals are widely implemented in the therapy and diagnosis of cancers. Since such radiotherapy is a relatively new method it’s still researched intensively to further improve the currently used techniques. 177Lu is a radionuclide used for cancer therapy with its decay of β- particles accompanied by photons suitable for SPECT imaging. A possibly improved alternative was found for 177Lu, namely 161Tb. The decay properties of 161Tb are very similar compared to those of 177Lu, however the main advantage is the amount of Auger electrons emitted per decay, 161Tb emits 16x more Auger electrons per decay. These Auger electrons are a desired type of emitted particles as they have a high linear energy transfer (LET), being able to damage unwanted tissue at a short range. 161Tb can be produced by neutron capture of 160Gd in a nuclear reactor. The difficulty of 161Tb production lies in the purification from the stable target material 160Gd. The separation of different lanthanides can be facilitated by selectively changing the oxidation state of the one to be extracted. The selective electrochemical oxidation of Tb3+ in aqueous carbonate solutions is investigated in this thesis. The quantification of produced Tb4+ by the measured current response at the working electrode during oxidation was not possible, because the measured current was caused by both the oxidation of Tb3+ and the oxidation of water to oxygen gas. For this reason the electrochemical reduction of Tb4+ was investigated with the goal of indirectly quantifying Tb4+ by reducing it back to Tb3+. Several parameters were varied to determine the influence on the electrochemical oxidation of Tb3+ in aqueous carbonate solutions. The concentrations of Tb and K2CO3 were investigated and optimized. The influence of pH was found to be crucial regarding the stability of Tb4+ complex. Furthermore kinetics was researched by varying the temperature. In addition to these, two types of flow cells were used for the electrochemical oxidation of Tb3+ to see the impact of electrode surface ratio on the system. To test the influence of the flow on a general electrolytic system, exploratory experiments were run using a dilute sulfuric acid in combination with a Pt working electrode. Finally, as a second type of cell which differs from the standard bulk electrolysis cell, a divided cell was tested. The counter electrode was separated from the rest of the cell using a semi-permeable membrane, preventing possible back reduction and therefore improving the efficiency. The two types of membranes tested were a CoralPor® frit and a more standard porous glass frit. For both membranes the resistance resulting from the separation was determined.
Original languageEnglish
QualificationMaster of Science
Awarding Institution
  • KU Leuven
  • Geboes, Bart, SCK CEN Mentor
  • Cardinaels, Thomas, Supervisor
  • Binnemans, Koen, Supervisor, External person
Date of Award30 Jun 2021
StatePublished - 30 Jun 2021

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