(511m) Effect Of Geometry On The Reaction Rate Distribution Over A Mesh Electrode Surface

A novel approach to in situ groundwater remediation uses expanded titanium mesh electrodes as the reactive substrate in a permeable reactive barrier format. Mesh electrodes were selected because of the large permeability to flow oriented normal to the electrode sheet, and because current is readily distributed to the large-scale structure. The distribution of reaction conditions over the electrode surface at the length scale of the mesh aperture (ca. 1 mm) directly impacts the process effectiveness and sustainability by concentrating activity to specific regions on the electrode surface.

Determination of the current density (and thus reaction rate) distribution to a sufficient spatial resolution by experimental methods was not feasible. Consequently, a three-dimensional computational fluid dynamics (CFD) model of the system was developed. The electrochemical potential was assumed to be constant over the electrode surface, simplifying the reduction kinetics of the contaminant species (hexahydro-1,3,5-trinitro-1,3,5-triazine; RDX). Modeling results were validated using physical data from complimentary experiments. The model results identified key regions on the surface where sharp gradients in the local reaction and transport conditions formed. Strategies to lessen these gradients by modifying the geometry were evaluated using the CFD model. The modifications deemphasized regions within the mesh aperture channels, which resulted in predictions of larger mass flux reduction rates through the domain and increased effectiveness factors of the surface reaction. Theses findings impact the interpretation of system performance and the future design of electrode materials.