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Carbon Dioxide for use in Acid -Base neutralization systems Page 1 of 2 <br />~1~174D~ ~~ ~ ~ ~~~,. <br />~.~ ~~. ~ ~ ~~,-.m~ _ - <br />I~IIa~ySIS ?.~I <br />There are many chemicals available on the market today that are suitable for use as neutralization chemicals. <br />The most commonly used chemicals are discussed in an article available here, and are in use for good reason. <br />Carbon Dioxide C02 <br />Carbon Dioxide (COQ: The third most concentrated gas found in earth's atmosphere (preceded by nitrogen <br />and oxygen) COZ is it self not an acid. COZ forms carbonic acid (HZC03) when dissolved in water; and it is <br />carbonic acid that leads to the neutralization of alkalinity in solution. Carbon dioxide is not easy to use and its <br />use is limited. However, for some applications COZ can be a very effective choice. The most appealing feature <br />of COZ is that it will not lower the pH of water below 7.0 (for practical purposes). Additionally COZ is not <br />corrosive as a gas, however, since COZ is heavier than air asphyxiation is always a hazard. Carbon dioxide can <br />be difficult to use because the gas must be dissolved into solution to be used. This requires the use of a <br />carbonator, or some method to dissolve the gas into solution. Generally a tall tank must be used to ensure that <br />there is sufficient fluid pressure to promote the dissolution of COZ in water. Significant out-gassing will occur, <br />which is not a problem unless the process also requires the settling of solids. <br />The architecture of a system that uses a gas neutralizing chemical is much different than that which uses a liquid <br />chemical. Therefore the use of COZ should be limited to unidirectional systems only (i.e. neutralizing alkaline <br />materials only). Bi-directional systems using COZ require the use of a liquid chemical for the alkaline chemical <br />and a gas for the acidic chemical. <br />Because of our unique design our pH adjustment systems can all be configured to use either liquid mineral acids <br />(such as sulfuric acid) or carbon dioxide. The efficacy of COZ as a neutralizing agent should be confirmed in a <br />laboratory, or through pilot testing, before use. <br />li,icl. to Ncutrnlii~:aiim Chrmicnls... <br />,I Hor„e, About Us Technical Articles System Examples <br />Digital Analysis Corporation <br />PO Box 95 <br />716 Visions Drive <br />Skaneateles, NY 13152 <br />315-685-0760 <br />315-685-0766(fax) <br />http:lJwww.phadjustment.com/CarbonDioxide.htm 11/11/04 <br />