Abstract
M.Sc.
Radionuclides exist in the environment because of natural and human activities that are an essential part of our lives. Nuclear processing, medicinal applications (using isotopes) and electric power production by nuclear stations are few examples of human activities that result in production of radioactive waste (RAW). The nuclear power stations in our world have to store their waste in such a manner that the present and future generations are protected from harmful radiations and this is a challenge. Exposure to RAW can result in severe, diverse and irreversible consequences such as damage of the ecosystem, pollution, cancers, birth mutations, to mention just a few. Solvent extraction (SE) technique is currently used to purify large volumes of secondary liquid waste before they are released to the environment or stored. However, even after the SE purification, highly radioactive liquid waste is given off. This highly radioactive liquid waste is solidified in a glass matrix (vitrification). In an attempt to reduce the disposal of large volumes of secondary RAW generated during the purification technology, this study was initiated to investigate the possibility of using multiwalled carbon nanotubes (MWCNTs) as part of the SE technique. As the main nuclear liquid extraction processes involve tributyl phosphate (TBP), the MWCNTs were linked to TBP, polymerised to give a MWCNTs-TBP polymer that was tested in the nuclear environment. This polymer should possess good chelating properties due to the inclusion of the phosphate and should be a good absorbent as MWCNTs are promising absorbent carbon materials. To test the hypothesis of the study MWCNTs-TBP polymer was tested for uranium extraction. The MWCNTs-TBP polymer gave a zero Kd value which indicates that the adsorption capacity of the polymer to remove radionuclides from waste streams was not successful. The MWCNTs were then tested for iodine-131 extraction whereby they were compared with single walled carbon nanotubes (SWCNTs) and double walled carbon nanotubes (DWCNTs). In this test SWCNTs gave a Kd value of 81694 mL/g which proved that they can be used in nuclear waste applications.