CAREER: Heterogeneous Reactions and Groundwater Flow in Reactive Porous Media

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

0134545 Devlin This work proposes to use granular iron, a low alloyed steel reclaimed from the scrap metal, as a model reactive porous medium to evaluate the following hypothesis: the hypothesis applies to media found in natural settings, such as sulfides and iron oxides, and has important implications for engineered in situ passive treatment systems as well as natural attenuation. The granular iron medium functions abiotically, simplifying the experimental designs and analysis. The emphasis of this work is with reactions involving organic pollutants in groundwater, and the processes selected for investigation as part of this program are: (1) reactivity discrimination between different classes of organic compounds and kinetics of reaction in systems with finite reactive surface availability, (2) sensitivity of hydraulic conductivity to precipitate accumulation, (3) relative importance of precipitate accumulation rates compared with corrosion rates to assess overall porosity loss/gain rates, (4) modeling of reactive transport with the appropriate kinetic models and (5) assessing and quantifying the effects of surface carbon on reactivity. The investigations are supported in the modeling and spectroscopic aspects by collaborators in Canada, and in the effects of surface carbon by Peerless, Michigan, a manufacturer of the material. Novel experimental techniques and approaches are incorporated into the investigations as listed above: (1) Reactivity experiments will be conducted in a batch reactor especially designed to minimize mass transfer effects and abrasion of particles at the same time. This will be accomplished by adhering the particles to a glass encased magnetic rod suspended in the reactor vessel. Competition experiments will provide evidence of reactive sites shared by different compound classes; (2) corrosion rates will be estimated by 2 independent methods (measurement of hydrogen production rates and electrochemically) and compared; (3) precipitation rates of anaerobic processes will be estimated from surface area changes and mass accumulations and the results compared; (4) changes to hydraulic conductivity will be investigated by examining columns connected to a common manifold so that more than one flow path is available should hydraulic conductivity changes occur to the reactive medium and (5) surface carbon investigations will be conducted in flow through batch reactors modified from earlier experiments (1 above). This technique will permit a distinction to be made between mass losses due to sorption from those due to reaction.