Liquid water medium aqueous wastes

Like supercritical carbon dioxide, supercritical water is a very interesting substance that has strikingly different properties from those of liquid water. For example, recent experiments have shown that supercritical (superfluid) water can behave simultaneously as both a polar and a nonpolar solvent. While the reasons for this unusual behavior remain unclear, the practical value of this behavior is very clear It makes superfluid water a very useful reaction medium for a wide variety of substances. One extremely important application of this idea involves the environmentally sound destruction of industrial wastes. Most hazardous organic (nonpolar) substances can be dissolved in supercritical water and oxidized by dissolved 02 in a matter of minutes. The products of these reactions are water, carbon dioxide, and possibly simple acids (which result when halogen-containing compounds are reacted). Therefore, the aqueous mixture that results from the reaction often can be disposed of with little further treatment. In contrast to the incinerators used to destroy organic waste products, a supercritical water reactor is a closed system (has no emissions). 

Environmental Waters and Waste Waters. This medium is multi-phasic and covers a wide range of constituents, including aqueous and nonaqueous liquids and dissolved and suspended solids. The protocol (Figure 3) is limited to solvent-extractable organic compounds however, not all compounds will be recoverable and/or stable under the protocol s methods. An overall scheme was developed and incorporated in the protocol to link the variety of components of this medium to the other protocols. 

Foamed emulsions are disperse systems with two disperse phases (gas and liquid) in the disperse medium (surfactant solution). Water foamed emulsions are formed when foams or aqueous surfactant solutions are used to clean up oil deteriorated surfaces, in the process of oil flotation of waste waters, in firefighting when the foam contacts various organic liquids and in the processes of chemical defoaming (foam destruction by antifoams). Individual foamed emulsions can have practical importance e.g. a foamed emulsion of bitumen is used in road coating foamed emulsions from liquid fuels are used as explosives. 

There are several processes that have been proposed for the direct combustion (oxidation or gasification) of coal within a liquid medium, and three of these are described as follows. The Zimpro process is based on the oxidation of crushed coal suspended in an oxygen-saturated hot-pressurized aqueous medium and is an outgrowth of an attempt to produce oxidized chemical products from paper mill wastes and the development of wastewater reclamation systems. The process involves the injection of high-pressure air into a slurry of hot water and coal under high pressure. High rates of oxidation occur at temperatures between 200°C and 350°C (390°F and 660°F) the exact temperature required to complete oxidation with reasonable residence time is dependent on the coal. Since the energy released is used to vaporize water, there is a direct relationship between the liquid temperature and the reactor pressure to which the air used for oxidation must be compressed. 

---