Thesis-1998-Stephens.pdf (5.08 MB)
Studies on the transport of metal humic complexes through porous media
thesis
posted on 2017-06-28, 11:27 authored by Sarah L. StephensHumic substances are ubiquitous in nature, constituting the major fraction of organic
materials present in soils. They are polymeric, polyelectrolytes and are known to form
water soluble complexes with metals. Whilst their metal complexing ability has been
widely studied, few studies have been conducted on their ability to transport metals
through the terrestrial environment. Laboratory studies were undertaken to investigate
those factors which may affect the transport of metal-humic complexes through
columns of porous geological media. In the main, intact Clashach sandstone columns
were used. The transport studies concentrated on europium (¹⁵²Eu) complexed to
humic material radiolabelled with ¹²⁵I, so that the measurement of both species was
facilitated at low concentrations. In order to measure the sorption of both the metal
and humic species along the column and in the effluent, a computer operated dual
detector instrument was designed and built. Initial studies comparing two methods of
introducing the complexes onto packed sand columns viz. injection and flooding
suggested that for tracer studies both methods were acceptable. However for metal
complex migration studies insufficient activity was recovered from the injection
technique to produce meaningful results. The effect of humic coating, and the presence
of iron within the column, on the recovery of various metal humate complexes from
both packed and intact columns were investigated. The presence of humic materials
greatly increased the recovery and mobility of the europium, but was found to retard
the mobility of cadmium and zinc. The presence of iron both naturally occurring in the
column materials and added to the packed columns as goethite was shown to greatly
retard the mobility of europium, cadmium and zinc. The effect of flow rate and column
length on the recovery of europium humate from Clashach sandstone cores was also
studied. Europium recovery was found to be related to the flow rate through the
column, suggesting a kinetically controlled sorption step. Europium recovery was not
found to be directly related to the column length as a high proportion of the metal is
sorbed within the first few centimetres. The recoveries and mobilities of europium
humate complexes were then modelled using a simple model. Batch equilibrium
experiments were conducted to determine the extent of sorption of metal humate
complexes on both natural sands and on crushed Clashach sandstone of differing
surface areas.
History
School
- Science
Department
- Chemistry
Publisher
© Sarah Louise StephensPublisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
1998Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en