group works in

two areas:

Humic materials are the breakdown products of plant and animal matter in the environment. They are found in virtually all soils and natural waters and they interact extensively with other soil components and man-made pollutants. Humics are highly complex substances that cannot be categorized on the basis of chemical structure alone. They are generally operationally defined, based on their solubility in aqueous solution.

Our interest in humics is focused on their solution behavior, especially the way in which they aggregate when exposed to different solution conditions. This depends, among other things, on the pH, the presence of cations (especially metals), the presence of other dissolved species, the concentration of the humics, and the temperature.

Humic substances determine to a large extent how metals and xenobiotics migrate through soil and water. We study them with a variety of techniques, including fluorescence spectroscopy, surface tension measurements, chromatography, conductance measurements, pyrolysis-GC-MS, NMR, and dynamic light scattering.

We are also interested in the use of bulk humics for the decontamination of polluted water.

Our studies of surface active agents are focused on non-ionic surfactants, especially the interesting clouding phenomenon observed with solutions of these compounds.

Micellar solutions of non-ionic surfactants display an inverse temperature–solubility relationship: when they are heated to a characteristic temperture known as the cloud point, they undergo phase separation. The surfactant aggregates formed are large enough to scatter visible light and give the solutions a milky appearance. After some time they settle to the bottom of the vessel, forming a separate surfactant-rich layer.

Our interests lie mainly in the mechanism of the clouding process and the structure of the aggregates formed. Many curious phenomena, including "preclouding", "declouding', and "reclouding" are observed when the surfactants aggregate. The nature of these episodes depends on seemingly small details of their molecular structure.

We aim to elucidate the causes of the various phenomena, using spectroscopy, surface measurements, and chromatography.

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