TAILIEUCHUNG - ADSORPTION OF ORGANIC COMPOUNDS

Understanding of the transport and attenuation of chemicals in the subsurface is fundamental to effective management of risks posed by chemicals and their possible impact on groundwater resources. A risk assessment approach to groundwater protection incorporates the three-stage combination of source, pathway and receptor. All three must be considered and understood to arrive at a balanced view of the risks to health of groundwater users. Informed consideration of the pathway, which in the context of this monograph means transport through the groundwater system, is vital. Such consideration not only includes consideration of the general and local hydrogeologic characteristics. | CHAPTER 13__ ADSORPTION OF ORGANIC COMPOUNDS Vernon L. Snoeyink . Ivan Racheff Professor of Environmental Engineering Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign Urbana Illinois R. Scott Summers . Professor of Environmental Engineering Civil Environmental and Architectural Engineering University of Colorado Boulder Colorado Adsorption of a substance involves its accumulation at the interface between two phases such as a liquid and a solid or a gas and a solid. The molecule that accumulates or adsorbs at the interface is called an adsorbate and the solid on which adsorption occurs is the adsorbent. Adsorbents of interest in water treatment include activated carbon ion exchange resins adsorbent resins metal oxides hydroxides and carbonates activated alumina clays and other solids that are suspended in or in contact with water. Adsorption plays an important role in the improvement of water quality. Activated carbon for example can be used to adsorb specific organic molecules that cause taste and odor mutagenicity and toxicity as well as natural organic matter NOM that causes color and that can react with chlorine to form disinfection byproducts DBPs . NOM is a complex mixture of compounds such as fulvic and humic acids hydrophilic acids and carbohydrates. The aluminum hydroxide and ferric hydroxide solids that form during coagulation will also adsorb NOM. Adsorption of NOM on anion exchange resins may reduce their capacity for anions see Chapter 9 but ion exchange resins and adsorbent resins are available that can be used for efficient removal of selected organic compounds. Calcium carbonate and magnesium hydroxide solids formed in the lime softening process have some adsorption capacity and pesticides adsorbed on clay particles can be removed by coagulation and filtration Chapters 6 and 8 . The removal of organic compounds by adsorption on activated carbon is very important in water purification and .

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