Kalliat T Valsaraj
Vice President of Research & Economic Development
Charles & Hilda Roddey Distinguished Professor; Ike East Professor
Room 130 David Boyd Hall
Louisiana State University
Baton Rouge, LA 70803
- PhD, Vanderbilt University, 1983
- MSc, Indian Institute of Technology, Madras, 1980
- BSc, University of Calicut, India, 1978
- Environmental Chemical Engineering
- Atmospheric Chemistry
- Wastewater treatment
- Modeling the fate & transport of contaminants in all three environmental media (air, water & soil/sediment)
Research in the Valsaraj group involves several areas of environmental, chemical & materials engineering.
Left to right: B Boyett, X Shu, I Woodson, P Avij,
M Skapura, A Heath, F Ehrenhauser & A Hansel.
Not pictured: C Bourdon & B Redmond
Chemistry of aqueous surfaces in the atmospheric context
Aqueous surfaces such as thin water films on aerosols, water droplets (fog, mist, dew, rain) & frozen precipitation (snow, ice) exist in the atmosphere. In most cases they have very high surface area to bulk volume ratio. A number of gas phase atmospheric trace gases (e.g., semi-volatile & volatile hydrophobic organic compounds) adsorb & react with gas phase oxidants (hydroxyl radical, singlet oxygen, ozone, nitrate radical, etc.) at these surfaces. These heterogeneous, multiphase processes are important in tropospheric chemistry. Our group uses a variety of techniques to probe the heterogeneous chemistry of several polycyclic aromatic hydrocarbons (PAH) on aqueous surfaces. These include falling droplet reactor (figure 1) & thin film flow reactors (figure 2a & b). We also collaborate with the groups of Professor Bin Chen (LSU Chemistry) & Prof Collin Wick (Louisiana Tech) on Molecular Dynamics & Monte Carlo simulations of PAHs at the air-water interfaces. This work is supported by the National Science Foundation.
Fog processing of organic compounds in the near- surface atmosphere
Fog is a near surface cloud with water droplets condensed on sub micron particles. The typical size of fog droplets are 1 to 50 microns & are therefore high surface area. Sunlight induced photochemistry in these systems can help to process most inorganic & organic species via oxidative reactions to form secondary organic aerosol precursors. It is also well known that a large fraction of organic carbon in fog is not spectated. To understand these problems, our group is engaged in both field collection & analysis of fog waters. We use active cloud water collectors (figure 3). We then use a variety of analysis techniques (GC/MS, HPLC/MS, ICP/MS) (figure 4,5, 6) to understand the composition of fog waters. This work is supported by the National Science Foundation.
We have also built an operational fog reactor (figure 7) in our laboratory to study the smog-fog-smog cycle. This instrumented set up is useful in obtaining rite constants & mechanisms of organic transformations in fog.
Mercury sequestration in contaminated sediments
Mercury is an ubiquitous pollutant in many Louisiana streams & lakes. Fish advisories exist for many of the lakes. Mercury comes mainly from power plants & other industrial processes & gets converted to easily assimilable methyl mercury in fish. It is therefore necessary to not only sequester mercury in the sediment but also prevent it's methylation. Our group has been involved in the above task by the use of an "active" sediment cap composed of Mackinawite. We use sediment microcosms (figure 8) to study the fate & transport of mercury through sediment caps. This work is supported by the Department of Interior through the Louisiana Water Resources Research Institute.
Aerosol transport of oil and dispersant components from a deep sea oil spill
During the Deep Water Horizon Spill a substantial amount of crude oil, as well as chemicals (dispersant) to combat the spill were set free in the Gulf of Mexico. This scenario (figure 9) can repeat in future accidents as well. This research investigates the contribution of the aerosolization of semi-volatile components of crude oil via bursting bubbles on the sea surface. Preliminary experiments from our laboratory have lent credible evidence for this process. Ejection rates of alkanes (C>15) from collected oil mousse samples & model mixtures are being assessed in a small-scale bubble reactor (figure 10) via GC-MS in the absence & the presence of dispersants & pure surfactants. The generated particulate matter are being characterized for its organic & inorganic constituents with SEM, ICP-MS, GC-MS & X-ray microscopy.
Photochemical reactors for waste treatment
Our on-going research in this area involves the use of highly ordered three-dimensional structures such as photonic crystals of titania for photocatalytic applications. These photonic crystals can influence electromagnetic waves in a manner similar to electrons in semiconductors. Fabricating them on optical fibers & using them in a monolith configuration is a vast improvement in current designs of photochemical reactors (figure 11).