Lockheed Martin Energy Research Corporation Research Articles

Effect of electrode configurations on phase equilibria with applied electric fields1This research was supported by the Environmental Management Science Program, Office of Environmental Management, US Department of Energy, under contract DEAC05-96OR22464 with Lockheed Martin Energy Research Corporation.1

Applying an electric field to some boiling binary mixtures has been shown experimentally to increase the separation factor by as much as 10%. In this work, an electric field was applied across the interface of boiling mixtures of 2-propanol–water via electrodes located in the vapor and the liquid. The shape and separation of the electrodes and the strength and polarity of the electric field were altered to investigate their effect on the vapor mole fraction, the current, and the vapor temperature. The results show that greater voltage differences, in the absence of excessive electrical current, lead to higher concentrations of 2-propanol in the vapor. However, it was found that varying the electrode separation at a given potential difference, and thus the electric field strength, has little effect on the vapor composition. The effects of the applied potential difference are reduced with elevated current and under conditions where liquid dynamics such as dripping, splashing, or jetting provide an opportunity for charge to be transferred between the electrode in the vapor and the liquid. It is also shown that directing the electric field from the vapor to the liquid produces a lower current, and the effect on the composition is larger. These findings, in combination with calculations of the interface charge density, suggest that improvements in the separation efficiency achieved by an applied potential difference are not due to effects of the electric field in the bulk fluids, but rather are induced by charge accumulation at the vapor–liquid interface.

DISPLACEMENT OF A HYDROCARBON OIL FROM A METAL SURFACE USING A SURFACTANT SOLUTION*

ABSTRACT Separation of oils from solid surfaces is important in cleaning and degreasing operations. Water and oils are immiscible requiring the use of an additive which is miscible with water yet has an affinity for oils. Surface active agents, known as surfactants, have this property, being miscible with water while having an affinity for hydrocarbons. In some cases, surfactant solutions displace oils from a solid surface (i.e., remove oil by replacing the oil/solid interfacial area with surfactant solution/solid interfacial area). The presence of alkalinity as well as surfactant concentration is known to affect the ability of a surfactant solution to wet the solid surface and displace the oil. Experiments have been performed to determine quantitatively the effects of surfactant concentration and pH on the displacement of an oil from a metal surface. The displacement is measured in terms of the contact angle formed by the oil on the solid surface in the presence of the surfactant solution, the amount of time needed for the surfactant solution to cause part of the oil to detach from the solid surface, and the volume of the detached oil. Measuring the contact angle of the oil as a function of time shows that surfactant concentration and pH affect the displacement of oil from a metal surface. Increasing the pH of a solution of Triton X-100, a non-ionic surfactant, enhances oil displacement. Increasing the surfactant concentration also enhances oil displacement. The volume of oil which detaches from the solid surface increases with increasing pH and increasing surfactant concentration. * Research supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S. Department of Energy under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation and the Department of Chemical Engineering at the University of Tennessee, Knoxville, Tennessee.

Modeling the Electrokinetic Decontamination of Concrete

The decontamination of concrete is a major concern in many Department of Energy (DOE) facilities. Numerous techniques (abrasive methods, manual methods, ultrasonics, concrete surface layer removal, chemical extraction methods, etc.) have been used to remove radioactive contamination from the surface of concrete. Recently, processes that are based on electrokinetic phenomena have been developed to decontaminate concrete. Electrokinetic decontamination has been shown to remove from 70 to over 90% of the surface radioactivity. To evaluate and improve the electrokinetic processes, a model has been developed to simulate the transport of ionic radionuclei constituents through the pores of concrete and into the anolyte and catholyte. The model takes into account the adsorption and desorption kinetics of the radionuclei from the pore walls, and ion transport by electro-osmosis, electromigration, and diffusion. A numerical technique, orthogonal collocation, is used to simultaneously solve the governing convective diffusion equations for a porous concrete slab and the current density equation. This paper presents the theoretical framework of the model and the results from the computation of the dynamics of ion transport during electrokinetic treatment of concrete. The simulation results are in good agreement with experimental data. * Managed by Lockheed-Martin Energy Research Corporation, Inc. for the U.S. Department of Energy under contract DE-AC05-84OR21400