Effect of polyaniline-coated galvanized steel electrodes on electrokinetic sedimentation of dredged mud slurries

An experimental study on electrokinetic improvement of dredged marine sediments to accelerate their sedimentation for land reclamation purposes is presented. Electrokinetic stabilization is currently used to improve soils; however, its use on soils with marine sediments with low permeability is still questionable due to the deterioration of anodes caused by an electrolysis reaction. A number of traditional methods are employed in literature to reduce the corrosion degradation of metals, such as painting, galvanizing, and conversion coating. Conducting polymers, e.g., polyaniline, are of engineering interest due to their properties such as ease of preparation and their high environmental stability in protecting metals from corrosion. For this purpose, the anodes used in the electrokinetic testing cell herein were coated with polyaniline to investigate the effect on electrokinetic stabilization of the dredged mud. Two series of experiments were performed using a polyaniline-coated galvanized steel anode, and two series of experiments with noncoated galvanized steel anodes were also carried out as a control. Depending on the applied voltage, the settlement and electroosmotic permeability of the dredged mud varied during the process. Polyaniline coating increased the power consumption during the electrokinetic stabilization compared to the case where the same electric potential was applied using the uncoated electrodes. However, when 5 V electric potential was applied to the soil through the polyaniline coated anode, its settlement and electroosmotic permeability were equivalent to what was observed with the 30 V electric potential applied through the noncoated anode, with 3 times less energy consumption.

Electroosmosis of Dilute Electrolyte Solutions in Microporous Media

The multiphysiochemical transport in electroosmosis of dilute electrolyte solutions (<1mM) through microporous media with granular random structures has been modeled in this work by our numerical framework consisting of three steps. First, the three-dimensional microstructures of porous media are reproduced by a random generation-growth method. Then the effects of chemical adsorption and electrical dissociation at the solid-liquid interfaces are considered to determine the electrical boundary conditions, which vary with the ionic concentration, the pH, and the temperature. Finally the nonlinear governing equations for the electrokinetic transport are solved by a highly efficient lattice Poisson-Boltzmann algorithm. The simulation results indicate that the electroosmotic permeability through the granular microporous media increases monotonically with the porosity, the ionic concentration, the pH and the environmental temperature. When the surface electric potential is higher than 50 mV, the permeability increases with the electric potential exponentially. The electroosmotic permeability increases with the pH exponentially, but with the temperature linearly. The present modeling results may improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems, and help guide the design of porous electrodes in micro energy systems.