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|Title: ||Studies on metal-humic interactions|
|Authors: ||Hall, Anthony|
|Issue Date: ||1993|
|Publisher: ||© Anthony Hall|
|Abstract: ||The favoured option for disposal of low and intermediate level radioactive waste is
burial deep underground. In the safety assessment of deep disposal facilities a
possibility which has to be considered is the eventual penetration of the engineered and
natural barriers by ground water. Unfortunately humic and fulvic acids, present in most
natural waters, can combine with radionuclides to produce metal complexes which are
potentially more mobile in the environment than the original radionuclides from which
they are formed. Migration of such complexes via groundwater and/or subsequently
surface water routes could result in accelerated release of radionuclides to the biosphere.
Quantitative knowledge of the extent of possible metal humate and fulvate interactions
is therefore of considerable importance.
In this study the complexation of Ni, Eu and Ce by humic and fulvic acids present in
both ground and surface waters has been investigated. In most studies, to simplify the
chemistry involved, humics and fulvics are separated from the water in which they
occur before determination of their complexation properties. However, the severe
conditions employed in the extraction process could conceivably alter the very
properties to be measured. Accordingly the complexation properties of humics and
fulvics present in a surface water have been studied both before and after extraction.
The major part of this study was undertaken using a High Performance Size Exclusion
Chromatographic technique especially developed to facilitate determinations on nonextracted
materials. A fluorescence technique was also investigated as a more rapid
alternative but was found to be of limited applicability.
Complexation parameters were derived using a strong and weak site model.
The effects of side reactions, ionic strength, pH, ligand type and nature of the cation
were taken into account. With respect to measured stability constants, no major
differences between ground and surface waters or extracted and non extracted materials
were found. However, measured capacities of humics and fulvics for metals showed
some variation according to the nature of the material and the system.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University|
|Appears in Collections:||PhD Theses (Chemistry)|
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