Environmental Engineering Reference
In-Depth Information
wide applications in various technological areas, including incineration of waste
and special medical uses. Many plasma applications are based on the possibili-
ty of introducing a high level of electric energy into the plasma. This leads to the
creation and maintenance of an ionized gas containing active atomic particles: elec-
trons, ions, excited atoms, radicals. These particles can be analyzed by a variety of
techniques, and therefore a plasma can used not only in energetic systems, but also
in measuring instruments. In particular, plasma-based methods of spectral analy-
sis are widely practiced in metallurgy. In these methods a small amount of metal
in the form of a solution or powder is introduced into a flowing discharge plasma,
and spectral analysis of the plasma makes it possible to determine the metal com-
position. The accuracy of spectral determination of admixture concentration with
respect to a primary component is of the order of 0.01-0.001%. On the basis of the
optogalvanic method [1, 2], one can increase this limit significantly.
The number of plasma applications is increasing with time and these appli-
cations are included in new aspects of human activity. Plasma applications in
medicine started several decades ago and are based on the mechanical or chemical
action of a plasma on a living object. For example, a plasma knife, which is a thick
plasma flux, is used similarly to a knife in surgery. The action of a plasma as an
active medium may be of various types because of the existence of many plasma
forms. In particular, destruction of medical waste, including bandages, medical
cotton, and other disposable materials, by using an arc plasma proceeds similarly
to combustion of these materials in an oven, but the plasma setup is more compact
and excludes dangerous products, but it is also more expensive. Nevertheless, plas-
ma methods are more favorable in practice than combustion of medical materials
in an oven. A not so powerful plasma is used for decontamination and sterilization
of medical tools. Because a plasma contains various active particles, such as elec-
trons, ions, metastable atoms and molecules, and radicals, it is applied in wound
healing, dermatology, and dentistry, where the plasma kills microbes and does
not destroy living tissue. Of course, a suitable plasma form and a certain current
regime must be used for each case and follows from the corresponding study. In
addition, plasma technology is used for production of specific medical materials
and devices.
Plasma processing for environmental applications is developing in two direc-
tions. The first is decomposition of toxic substances, explosive materials, and other
hazardous wastes, that can be decomposed in a plasma into their simple chemical
constituents. The second is improvement of air quality. A corona discharge of low
power is used for this purpose. This gas discharge generates active atomic particles
such as oxygen atoms. These atoms have an affinity for active chemical compounds
in air, and react with them. Such discharges also destroy microbes, but present no
hazards to humans because of low concentrations of these particles.
Plasmas are currently widely employed in industry, and their range of application
is increasing continuously [10-12, 15]. The usefulness of plasmas in technology
can be ascribed to two qualities: Plasmas make available much higher tempera-
tures than can be achieved with chemical fuel torches; and a large variety of ions,
radicals, and other chemically active particles are generated therein. Therefore, ei-
