Novel Remediation Techniques for Radioactively Contaminated Land

Abstract

90Sr is a radionuclide produced in high yield during nuclear fission and is a key contaminant within the environment, including as a contaminant in groundwater at nuclear sites. As a result, there is an increasing demand for novel, cost effective and low waste producing remediation techniques to prevent 90Sr migration to the far field. This present study investigates the application of novel materials for the removal of stable Sr as a proxy for 90Sr from groundwater, namely: nano-zerovalent iron, biomagnetite, Carbo-Iron and hydroxyapatite. The uptake of Sr is studied as a function of time, Sr concentration in solution and pH. Experiments were carried out with and without the presence of sediment, in order to assess the applicability of the materials in complex environmental systems. In this case, the environmental system was a simplified analogue for the nuclear site of Sellafield, Cumbria, using sediment collected from the area and a representative artificial groundwater. The results indicate that HA and nZVI are better suited for Sellafield Sr remediation than iron nanoparticles, which have their efficiency for Sr uptake greatly reduced in a sediment system. Hydroxyapatite is observed to have similar affinity for Sr in the presence of sediment, achieving a 50.1% removal of 1mM Sr in solution after 28 days. XRD analyses of the HA system showed significant Sr removal but no Sr incorporation into the HA, but did identify the coprecipitation of strontianite (SrCO3) with calcite. ESEM EDS also confirmed the formation of strontianite in nZVI experiments, which exhibited lower Sr concentrations in solution. Overall, it is likely that most Sr was removed from solution by carbonate precipitation induced by the high calcium carbonate concentration in the artificial groundwater, rather than uptake by the materials tested. Although not a permanent solution for in-situ remediation, carbonate coprecipitation could lead to a viable remediation technique with further research.

Date of Award	31 Dec 2017
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Katherine Morris (Supervisor) & Jonathan Lloyd (Supervisor)