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19 SOLUBILIZATION AND BIODEGRADATION OF OCTADECANE IN THE PRESENCE OF TWO COMMERCIAL SURFACTANTS Le T. Thai, Research Assistant Walter J. Maier, Professor Department of Civil and Mineral Engineering University of Minnesota Minneapolis, Minnesota 55455 INTRODUCTION Compounds are usually only biodegraded when they are dissolved in an aqueous solution or at least in direct contact with water.1"6 Accessibility is a particular concern with hydrocarbons that have low aqueous solubility because in a soil environment, they will tend to sorb or partition to the soil matrix, or form separate organic phases in the pore spaces. In order to enhance biodegradation of these compounds, it is necessary to accelerate their desorption and/or solubilization rate. Desorption and/ or solubilization can be accelerated with the addition of surfactants, which have been shown to be effective in enhancing desorption and solubilization of hydrophobic compounds.7,8 Surfactants, or surface active agents, are amphipathic molecules consisting of a polar/hydrophilic head and a nonpolar/hydrophobic tail. When added to water, a surfactant molecule may dissolve as a monomer, adsorb at an interface with its hydrophobic end pointing away from the water, or aggregate with other surfactant molecules into clusters called micelles.910 The first two forms dominate below the critical micelle concentration, and the third above. The critical micelle concentration (CMC) corresponds to the surfactant concentration at which micelles are formed. Micelles are organized aggregates of surfactant molecules with the molecules' hydrophobic groups directed toward the interior of the aggregates and their hydrophilic groups directed toward the water.10 The CMC value is unique for each surfactant and temperature. Furthermore, at the CMC, there are sharp breaks in many physical properties of the surfactant solution such as its electrical conductivity and surface tension.10 Surfactants can enhance the apparent solubility of a hydrophobic compound through at least two mechanisms. The first mechanism is dominant below the critical micelle concentration. It involves the "association" of the hydrophobic compound with the hydrophobic groups of the surfactant molecules. The second mechanism is important above the CMC and involves the partitioning of the hydrophobic compound into the hydrophobic/nonpolar centers of the surfactant micelles." While surfactants' ability to enhance desorption and solubilization of hydrophobic compounds has been studied by many researchers,912 the effect of surfactants on biodegradability has been less thoroughly studied. The purpose of this research was to characterize both the potential for enhancement of solubilization of a sparingly soluble compound through surfactant addition, and the potential for enhancing rates of biodegradation. MATERIALS AND METHODS Solubility Enhancement Experiments Solubilities of octadecane were measured in a series of solutions containing from 5 to 300 mg/L of surfactants. Octadecane (purity = 99%) was obtained from Aldrich Chemical Company, Milwaukee, WI. Carbon-14 octadecane, labelled in theC-1 position (specific activity: 3.6 mCi per mmol; purity > 98%) was obtained from Sigma Chemical Company, St. Louis, MO. Triton X-l 14 (manufactured by Rohm and Haas) was also obtained from Sigma Chemicals, St. Louis, MO; Corexit 0600 was obtained from Exxon Chemical Company, Houston, TX. Surfactants were used as received without further purification. Hexane was obtained from Fisher Scientific Co., Pittsburgh, PA. Acrodisc HT Tuffryn 0.2 /tm polysulfone membrane filters (manufactured by Gelman) were obtained from Fisher 47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 167
Object Description
Purdue Identification Number | ETRIWC199219 |
Title | Solubilization and biodegradation of octadecane in the presence of two commercial surfactants |
Author |
Thai, Le T. Maier, Walter J. |
Date of Original | 1992 |
Conference Title | Proceedings of the 47th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,43678 |
Extent of Original | p. 167-176 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
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Description
Title | page 167 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | 19 SOLUBILIZATION AND BIODEGRADATION OF OCTADECANE IN THE PRESENCE OF TWO COMMERCIAL SURFACTANTS Le T. Thai, Research Assistant Walter J. Maier, Professor Department of Civil and Mineral Engineering University of Minnesota Minneapolis, Minnesota 55455 INTRODUCTION Compounds are usually only biodegraded when they are dissolved in an aqueous solution or at least in direct contact with water.1"6 Accessibility is a particular concern with hydrocarbons that have low aqueous solubility because in a soil environment, they will tend to sorb or partition to the soil matrix, or form separate organic phases in the pore spaces. In order to enhance biodegradation of these compounds, it is necessary to accelerate their desorption and/or solubilization rate. Desorption and/ or solubilization can be accelerated with the addition of surfactants, which have been shown to be effective in enhancing desorption and solubilization of hydrophobic compounds.7,8 Surfactants, or surface active agents, are amphipathic molecules consisting of a polar/hydrophilic head and a nonpolar/hydrophobic tail. When added to water, a surfactant molecule may dissolve as a monomer, adsorb at an interface with its hydrophobic end pointing away from the water, or aggregate with other surfactant molecules into clusters called micelles.910 The first two forms dominate below the critical micelle concentration, and the third above. The critical micelle concentration (CMC) corresponds to the surfactant concentration at which micelles are formed. Micelles are organized aggregates of surfactant molecules with the molecules' hydrophobic groups directed toward the interior of the aggregates and their hydrophilic groups directed toward the water.10 The CMC value is unique for each surfactant and temperature. Furthermore, at the CMC, there are sharp breaks in many physical properties of the surfactant solution such as its electrical conductivity and surface tension.10 Surfactants can enhance the apparent solubility of a hydrophobic compound through at least two mechanisms. The first mechanism is dominant below the critical micelle concentration. It involves the "association" of the hydrophobic compound with the hydrophobic groups of the surfactant molecules. The second mechanism is important above the CMC and involves the partitioning of the hydrophobic compound into the hydrophobic/nonpolar centers of the surfactant micelles." While surfactants' ability to enhance desorption and solubilization of hydrophobic compounds has been studied by many researchers,912 the effect of surfactants on biodegradability has been less thoroughly studied. The purpose of this research was to characterize both the potential for enhancement of solubilization of a sparingly soluble compound through surfactant addition, and the potential for enhancing rates of biodegradation. MATERIALS AND METHODS Solubility Enhancement Experiments Solubilities of octadecane were measured in a series of solutions containing from 5 to 300 mg/L of surfactants. Octadecane (purity = 99%) was obtained from Aldrich Chemical Company, Milwaukee, WI. Carbon-14 octadecane, labelled in theC-1 position (specific activity: 3.6 mCi per mmol; purity > 98%) was obtained from Sigma Chemical Company, St. Louis, MO. Triton X-l 14 (manufactured by Rohm and Haas) was also obtained from Sigma Chemicals, St. Louis, MO; Corexit 0600 was obtained from Exxon Chemical Company, Houston, TX. Surfactants were used as received without further purification. Hexane was obtained from Fisher Scientific Co., Pittsburgh, PA. Acrodisc HT Tuffryn 0.2 /tm polysulfone membrane filters (manufactured by Gelman) were obtained from Fisher 47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 167 |
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