Ozone is widely used to deactivate microorganisms and remove organic contaminants in water industries. However, interest also exists in using radical species, which are stronger oxidants than ozone, in such processes. One means of producing radical species is by corona discharge. This work investigates the use of a novel pulseless corona-discharge system for the removal of organic substances. The method combines corona discharge with electrohydrodynamic spraying of oxygen, forming microbubbles. Experimental results show that pulseless corona discharge effectively removes organics, such as phenol and methylene blue, in deionized water. The corona-discharge method is demonstrated to be comparable to the direct use of ozone at a high applied voltage. The results also show that a minimum applied voltage exists for an effective operation of the corona-discharge method. In this work, the minimum applied voltage is approximately 4−4.5 kV over a 3-cm distance between the electrodes. The kinetic rate of phenol degradation in the reactor is modeled. Modeling results show that the dominant species of the pulseless corona-discharge reactor are hydroxyl radical and aqueous electron. Several radical species produced in the pulseless corona-discharge process are identified experimentally. The major species are hydroxyl radical, atomic hydrogen species, and ozone.

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The mechanism of electrostatic spraying of insulating fluids, such as air or organic solvents, into relatively conductive fluids, such as water, is investigated in this work. Experiments with air sprayed into water through an electrified capillary showed that the pressure inside the capillary increases, reaches a maximum, and then decreases as the applied voltage is increased. The initial pressure increase is due to the electric stress on the fluid interface, while the decrease is due to the Coulombic electrohydrodynamic flow generated near the end of the capillary. It is shown that electric fields can cause simultaneous pumping, spraying, and mixing of fluids. This phenomenon is demonstrated for air and kerosene in water.On Ctudie dans ce travail le mecanisme de Keywords: electrostatic spraying, gas-liquid dispersions, liquid-liquid dispersions, microbubbles, microdrops lectric-field-driven processes have been known for many E years. Common industrial applications are solid-solid separations in the mining industry, coalescence of water-inoil emulsion in the petroleum industry, and removal of solid particles from exhaust gases in various technologies. Ptasinski and Kerkhof (1 992) reported several advantages of direct utilization of electrical energy, especially in multiphase systems. These advantages result from the fact that electrical energy supplied to the system interacts selectively with an interface and, to a lesser degree, with the bulk. This interaction may lead to increased rates of heat or mass transfer across an interface.Many chemical, biochemical, and environmental processes, such as extraction, distillation, stripping, flotation, and oxidation, depend upon the creation of multiphase dispersions consisting of a discontinuous phase-in the form of particles, drops, or bubbles-dispersed in a liquid, gaseous, or supercritical continuous phase. In most of these applications, the objective is to increase the surface area of contact for efficient transport of chemical species from one phase to another. In general, the performance of such systems is enhanced as the dispersed drop or bubble size is decreased. Traditional devices make use of mechanical agitation with various types of impellers to contact two or more phases. These devices provide kinetic energy to the bulk liquid, wasting a large fraction by viscous dissipation. Liquid-liquid and gas-liquid systems formed by mechanical agitation usually contain dispersed drops or bubbles in the millimeter-size range. By providing the energy required to create fine drops and bubbles right at the interface, electrostatic spraying is far more efficient than mechanical systems. Micron-sized drops or bubbles can be efficiently generated by electrostatic spraying. Recent results by Scott and Wham (1989), Scott et al. (1994), and *Author to whom correspondence may be addressed. E-mail address:+Managed by Lockheed Martin Energy Research Cop. tsourisc @ ornl .gov Tsouris et al. (1997) show that electrostatic-spraying processes may be much more efficient than conventi...

The objective of this work is to investigate bubble generation of air in water through electrified metal capillaries. Many important factors that affect the formation of bubbles, including capillary size, capillary tip configuration, electrode distance, and flow rate, are studied. It is found that the bubble size decreases with increasing applied voltage and decreasing airflow rate. A dimensional analysis of the system parameters is also pursued. The dimensionless numbers are correlated into an empirical model that can be used for the prediction of the bubble size as a function of the applied voltage and airflow rate. It is found that the bubble size decreases with decreasing Reynolds number and increasing Weber number. Three different modes of bubble formation are observed:  a spraying mode obtained at low airflow rate and high applied voltage, a dripping mode observed at high flow rate and low applied voltage, and a mixed spraying−dripping mode.

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