Organic Chemical Adsorption

Factors of Soil Formation. McGraw-Hill, New York. 

Schnitzer, M and H.-R. Schulten. 1998. New ideas on the chemical make-up of soil humic and fulvic acids. In Future Prospects for Soil Chemistry (P. M. Huang, ed.). Soil Science Society of America Spec. Publ. 55, Madison, WI. 

Distinguish between soil organic matter, humus, and soil biomass. 

Give representative SOM contents for Mollisols, Aridisols, Oxisols, and His-tosols. Justify the SOM content of each in terms of the factors of soil formation. 

Explain why the SOM content of soils in a given climatic zone tends to be higher in fine-textured soils than in coarse-textured soils, 

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Adsorption usually increases as pH and temperature decrease. Chemical reactions and forms of chemicals are closely related to pH and temperature. When pH and temperature are lowered many organic chemicals are in a more adsorbable form. The adsorption process is also influenced by the length of time that the AC is in contact with the contaminant in the water. Increasing contact time allows greater amounts of contaminant to be removed from the water. Contact is improved by increasing the amount of AC in the filter and reducing the flow rate of water through the filter. 

Adsorption beds of activated carbon for the purification of citric acid, and adsorption of organic chemicals by charcoal or porous polymers, are good examples of ion-exchange adsorption systems. Synthetic resins such as styrene, divinylbenzene, acrylamide polymers activated carbon are porous media with total surface area of 450-1800 m2-g h There are a few well-known adsorption systems such as isothermal adsorption systems. The best known adsorption model is Langmuir isotherm adsorption. 

Many organic electrode processes require the adsorption of the electroactive species at the electrode surface before the electron transfer can occur. This adsorption may take the form of physical or reversible chemical adsorption, as has been commonly observed at a mercury/water interface, or it may take the form of irreversible, dissociative chemical adsorption where bond fracture occurs during the adsorption process and often leads to the complete destruction of the molecule. This latter t q)e of adsorption is particularly prevalent at metals in the platinum group and accounts for their activity as heterogeneous catalysts and as... 

The key features of soot are its chemical inertness, its physical and chemical adsorption properties, and its light absorption. The large surface area coupled with the presence of various organic functional groups allow the adsorption of many different materials onto the surfaces of the particles. This type of sorption occurs both in the aerosol phase and in the aqueous phase once particles are captured by cloud droplets. As a result, complex chemical processes occur on the surface of soot particles, and otherwise volatile species may be scavenged by the soot particles. 

Winters and Lee134 describe a physically based model for adsorption kinetics for hydrophobic organic chemicals to and from suspended sediment and soil particles. The model requires determination of a single effective dififusivity parameter, which is predictable from compound solution diffusivity, the octanol-water partition coefficient, and the adsorbent organic content, density, and porosity. 

Adsorption Partition Coefficients. Experimental KQC values were used when available otherwise, the K values were estimted. We used a correlation between aqueous solubility (Cs t) and Koc that contained data for pesticides and a group of polar and nonpolar organic chemicals collected by Kenega and Goring (18) and Smith et al. (3) ... 

Table III illustrates the impact of adsorption on the leaching of organic chemicals in the soil. A water input of 305 cm was used, which is equivalent to a full year of precipitation in the eastern United States. In a soil with a field capacity of 30%, the water would penetrate 1017 cm. Mirex with a very large Kqc is practically immobile after a full year of precipitation, it is still on the surface. It is likely that any compound adsorbed this strongly would be carried off the land surface by soil erosion instead of being leached into the soil. In contrast, DBCP, which is very weakly adsorbed, penetrates the soil profile almost as far as the water does.

Hamaker, J. W. Thompson, J. M. "Adsorption" Chapter 2 in "Organic Chemicals in the Soil Environment" Marcel Dekker New York, 1972. 

Carrizosa MJ, Hermosin MC, Koskinen WC, Cornejo J (2004) Interactions of two sulfonylurea herbicides with organoclays. Clays Clay Miner 52 643-649 Celis R, Hermosin MC, Cornejo J (2000) Heavy metal adsorption by functionalized clays. Environ Sci Technol 34 4593-4599 Chappell MA, Laird DA, Thompson ML, Li H, Teppen BJ, Johnston CT, Boyd SA (2005) Influence of smectite hydration and swelling on atrazine sorption behavior. Environ. Sci Technol 39 3150-3156 Chiou CT (1989) Theoretical considerations of the partition uptake of nonionic organic compounds by soil organic matter. In Sawhney BL, Brown K (eds) Reactions and movement of organic chemicals in soils. Soil Science Society of America, Madison, WI, pp 1-29... 

Zielke RC, Pinnavaia TJ, Mortland MM (1989) Adsorption and reactions of selected organic molecules on clay mineral surfaces. In Sawhney BL, Brown K (eds) Reactions and movement of organic chemicals in soils. Soil Science Society of America, Madison, WI, pp 81-97... 

Since sorption is primarily a surface phenomenon, its activity is a direct function of the surface area of the solid as well as the electrical forces active on that surface. Most organic chemicals are nonionic and therefore associate more readily with organic rather than with mineral particles in soils. Dispersed organic carbon found in soils has a very high surface-to-volume ratio. A small percentage of organic carbon can have a larger adsorptive capacity than the total of the mineral components. 

Chiou CT. 1989. Partition and adsorption on soil and mobility of organic pollutants and pesticides. In GerstI Z, ed. Ecological studies, Vol. 73. Toxic organic chemical in porous media Second international workshop on behavior of pollutants in porous media. Bet Dagan, Israel, June 1987. 

Table 15. Freundlich and Soil Adsorption Coefficients of Organic Chemicals and Metals... 

Blum, DJ. W., Suffet, I.H., and Duguet, J.P. Quantitative structure-activity relationship using molecularconnectivity for the activated carbon adsorption of organic chemicals in water. Water Res., 28 687-699,1994. 

Xia, G. and Ball, W.P. Adsorption-partitioning uptake of nine low-polarity organic chemicals on a natural sorbent. Environ. Scl Technol, 33(2) 262-269,1999. 

Calvet R (1989a) Adsorption of organic chemicals in soils. Environ Health Perspect 83 145-177 Calvet R (1989b) Analyse du concept de biodiponibrlite d une substance dans le sol. Sci Sol 26 183-201... 

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