RESEARCH - ENVIRONMENTAL SURFACE AND COLLOID PROCESSES LABORATORY

Natural organic matter (NOM) governs the behavior of chemical contaminants in natural and engineered systems and I have devoted significant effort at evaluating a range of NOM-regulated processes.  NOM can be roughly divided into two pools comprised of heterogeneous humic substances that resist characterization and molecules of known structure that share functionality with humic substances but owing to their known structure they are more readily evaluated. 

My work with NOM focusses on improving our understanding of their influence on particle behavior and contaminant fate.  To this end, we have evaluated how NOM alters particle interactions because as they interact with these surfaces they change their interfacial properties. For example, our recent work with silver nanoparticles demonstrates that humic substances interact with the particle surface and that this interaction enhances particle stability and minimizes dissolution. With organic acids of known structure, we demonstrated that even small molecules (e.g., maleate) induce steric effects and that small differences in molecular orientation at interfaces results in different particle behavior.  Our work evaluating the influence of NOM on contaminant binding demonstrated the underlying surface structure of the oxide dominates interactions with lead as the adsorbed NOM influence is modest and does not appear to reflect differences in NOM structure.

Another area of research focusses on seeking sustainable outcomes associated with the management and disposal of large-volume wastes, such as membrane concentrate, lime softening sludge, arsenic-laden adsorbent materials and coal combustion byproducts. Our recent work with arsenic-laden adsorbents demonstrates the potential for arsenic release into municipal waste landfills exceeds that predicted through regulatory leaching tests, reflecting the influence of biological and chemical processes not accounted for in these tests.  We are investigating the recovery of Rare Earth Elements from acid mine drainage (AMD) using stabilized flue gas desulfurization materials and although in its preliminary stages this work demonstrates potential as an approach to mitigate the harmful environmental effects of AMD while recovering marketable products.