Abstract:
The increasing concerns regarding emerging contaminants in aquatic ecosystems provide
a need to understand the role surface chemistry plays in the fate and transport of pollutants. The
overarching aim of this thesis has been to investigate adsorption of selected emerging pollutants
to colloids and elucidate how these surface interactions influence their fate and mobility in
aquatic systems. Research presented here advances our understanding of pollutant-colloid
interactions and provides a methodology for systematic fate and transport studies.
In Chapter 1, the diverse and rich research revolving around emerging contaminants and
the natural environment are demonstrated. Strides have been made in trying to understand
pollutant fate and transport in an aqueous environment. Adsorption to natural and man-made
surface appears to be dependent on pH, electrolyte/ionic strength, functional group, and
competing molecules on the removal of ECs from the aqueous phase. Chapter 2 focuses on the
theory behind instruments used for data collection throughout this thesis. It highlights a surface
sensitive laser spectroscopy technique called second harmonic generation, dynamic light
scattering, surface tensiometery, and gravimetric analysis using quartz crystal microbalance.
Chapter 3 addresses questions relating to fundamental parameters of magnetic colloids with the
potential to serve as a remediation tool for industrial cationic dye removal from water. The
influence of aggregation on the effectiveness of colloids as a remediation tool is discussed.
Chapter 4 presents research questions regarding fate and transport of pharmaceuticals. The
binding affinity and adsorption mechanisms of pharmaceuticals onto colloidal NOM and model
colloidal NOM is explored. Chapter 5 is dedicated to the development of an analytical tool to
detect pollutants at low concentrations in aqueous solution. This final chapter also discusses
future direction and potential research projects.
Using a variety of spectroscopic tools, fundamental and practical insights have been
gained throughout this thesis. Major results include, but not limited to, (1) determination of
aggregation of particles in the presence of man-made pollutants and (2) characterization of
binding mechanisms involved in the adsorption of pharmaceuticals to model natural colloids.
The first major results show significant aggregation of magnetic particles (MP) occur in aqueous
solution upon the adsorption of malachite green (MG). Treating aggregation as a linear function
of dye concentration enabled the development of a modified Langmuir model to determine
binding affinity. Using this model, binding affinity of MG onto MP has been determined to be –
39.8 (± 0.7) kJ/mol.
The second major results demonstrate that amlodipine (AMP) and carbamazepine (CBZ)
adsorb to colloidal natural organic matter (NOM) with binding affinities of –41.2 (± 0.7) and –
38.2 (± 0.7) kJ/mol, respectively. AMP and CBZ have also been found to adsorb to polymeric
based magnetic particles functionalized with –COOH and –NH2 with binding affinities on the
same order of magnitude as colloidal NOM. This study reveals adsorption to –COOH and –NH2
functionalized particles is not limited to electrostatic interactions.
The research in this thesis also include development and application of analytical
methods, such as a quartz crystal microbalance (QCM) to detect water pollutants in the nano- to
micro-molar concentration range. Results indicate MG and AMP can be detected with QCM
functionalized with a self-assembled monolayer (SAM) from aqueous solution at initial
concentrations as low as 91 nM. Future QCM research will explore other environmentally
relevant functionalized SAMs, as well as, NOM surfaces. Also, preliminary adsorption
experiments involving emerging contaminants binding to hydrophobic surfaces will help to
better understand hydrophobic binding interactions.