Lab_Report - Kow

Lab_Report - Kow - Physical & Chemical Principles of...

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Physical & Chemical Principles of Environmental Engineering CGN 6933-05 Fall Semester, 2005 1 Experimental Determination of the Octanol-Water Partition Coefficient for Acetophenone and Atrazine OMATOYO K. DALRYMPLE Department of Civil & Environmental Engineering University of South Florida, Tampa, USA Octanol-water partition coefficient (K ow ) values were determined for acetophenone and atrazine in the lab. Each compound was dissolved in water to a known concentration and placed in an octanol-water system and allowed to equilibrate. Concentration in the aqueous phase was then determined by use of a UV-visible spectrophotometer. Based on a simple mass balance, the concentration in the octanol phase was determined and the K ow was calculated as the ratio of the concentration in the octanol phase to the concentration in the aqueous phase at neutral pH. The results are presented as both K ow and log(K ow ). In general, the values are in good agreement with those reported in the literature. The results are discussed in terms of further understanding of the possible behavior and fate of the chemicals in the environment. KEYWORDS: Partition coefficient; log K ow ; acetophenone; atrazine. INTRODUCTION The octanol-water partition (K ow ) coefficient can be viewed as the hydrophilic-lipophilic balance of a substance. It is a measure of the tendency of the substance to prefer an organic or oily phase rather than an aqueous phase. The K ow of a substance can be measured in a laboratory and provides an important indication of the chemical’s ability to partition itself in the environment between an organic phase, such as fish and soil, and an aqueous phase. Partition coefficients are used extensively in chemical and environmental engineering to determine the behavior and fate of chemicals. The octanol-water partition coefficient is recognized by the US government and some international organizations as a physical property of organic pollutants equal in importance to vapor pressure, water solubility and toxicity. One of its most important applications is the determination of bioconcentration factors of pollutants for aquatic life, and as such, it is considered a required property in studies of new or problematic chemicals (US EPA, 2004). In general, pollutants with low K ow values (e.g., less than 10) may be considered relatively hydrophilic (especially if Henry’s Law constant is also low); they tend to have high water solubility, small soil/sediment adsorption coefficients, and small bioconcentration factors for aquatic life. Conversely, chemicals with high K ow values (e.g., greater than 10 4 ) are very hydrophobic and adsorb to soil/sediments and tend to bioaccumulate. In this experiment, the K ow for acetophenone and atrazine was determined. Acetophenone is the simplest aromatic ketone and is used as an intermediate for pharmaceuticals, agrochemicals and other organic compounds. It is also used as a solvent for plastics, resins, cellulose ethers, and esters. Atrazine is a herbicide used
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Lab_Report - Kow - Physical & Chemical Principles of...

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