Date of Award
Spring 5-10-2024
Degree Type
Thesis
Degree Name
Master of Science Chemical Sciences
Department
Chemistry and Biochemistry
Committee Chair/First Advisor
Dr. Daniel Ferreira
Second Advisor
Prof. Bharat Baruah
Third Advisor
Prof. Huggins Msimanga
Abstract
The Fukushima Daiichi Nuclear Power Plant meltdown in Japan resulted in the release of radionuclides into the environment. Soil in neighboring prefectures has been reported to be among the most contaminated. Since the event in 2011, a large volume of soil has been collected and stored in temporary storage facilities, awaiting decontamination. Numerous methods have been used and employed to remediate these soils, but most methods do not achieve the 90% removal target set by the Japanese government for safe disposal. Among all reported methods, the ion-exchange technique has been reported to be cost-efficient and effective. A study by Tamura et al. employed the use of various ions to exchange cesium ions and reported that among all ions explored magnesium ions were more likely to replace cesium ions. However, after about two hours due to the high affinity of cesium ions for the clay minerals, cesium replaced magnesium. This required the use of agents that could keep the cesium ions in solution after desorption. Sodium tetrakis(4-fluorophenyl)-borate (Na-TFPB) showed to be a good precipitating agent to keep cesium ions in solution. However, TFPB is expensive and therefore alternative precipitating agents have been explored by Baruah et al.. The exploration of Silicotungstic acid (STA), Phosphotungstic acid (PTA) and Molybdovanadophosphoric acid (MVPA) has shown promise but the results from the study have a setback in terms of establishing a mass balance for cesium ions before and after the remediation process was applied. This was mainly attributed to the use of a hot-block digester which resulted in incomplete digestion of the soil samples. In this work, the use of a microwave digester was explored to serve as an alternative to the hot-block digester and the use of pure vermiculite clay for both remediation and serial applications was explored using STA and TFPB. The results showed that the microwave digester contributed to the total digestion of both pure vermiculite and the actual Fukushima clay, which contributed to a more realistic result. Also, the results showed that the precipitating agent Silicotungstic acid is well able to replace TFPB and provide a more cost-effective alternative to the remediation of radiocesium from radiocesium-infused soils.