Performance of Pollutant Adsorbents (2001-2003)
 
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The Ion Chromatography system seen here is one of the analytical techniques used at the GCI to measure low indoor concentrations of acetic acid and similar gases from construction and display materials. Photo: James Druzik.

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To measure the capacity of adsorbents for single and combinations of gases, permeation and diffusion tubes are used to deliver set concentrations under controlled conditions. Here, laboratory air is preconditioned, the flow rates carefully measured, and adsorbents exposed for periods of from 2 to 4 months. Photo: Jeffrey Levin.

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The packed gas tube on the right contains pellets of adsorbent spaced between white, irregular pieces of Teflon. The path of the gas flow is sufficiently mixed that when coupled with a very long residence time all of the pollutant has had time to react with the adsorbent. Photo: Jeffrey Levin.

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In this set-up, finely powdered and granular adsorbents are exposed to 2 ppm formic acid at 50% RH for 12 weeks. Periodically samples are removed for monitoring the progress of the exposure. Samples are analyzed using thermalgravimetry (TG), differential thermal analysis, and evolved gas analysis in one operation. Separately, total weight % carbon, nitrogen, hydrogen, and sulfur are analyzed to support the TG analysis. Photo: Jeffrey Levin.

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For a special type of material called a "chemisorbent," a known quantity of gas is passed through a bed of chemisorbent until the pollutant breaks through the bed and can be measured at the outlet. On the right is about 2 grams of purple-red Purafil. On the left is the same material now brownish-black after reacting with about 11 weight % acetic acid. In the middle, 14.5 weight percent of formic acid has exhausted the potassium permanganate (the brownish-black material) and then proceeded to react further with the alumina substrate (the white efflorescence). Photo: Jeffrey Levin.