Influence of surfactant sorption on the removal of phenanthrene from contaminated soils

Laboratory column flushing experiments were conducted to remove phenanthrene from contaminated soils by Triton X-100 (TX100) with an aim to investigating the effect of surfactant sorption on the performance of surfactant-enhanced remediation process. The effluent concentration of phenanthrene from soil columns showed strong dependence on the sorption breakthrough curves of TX100. The removal of phenanthrene from contaminated soils was enhanced only when the sorption breakthrough of TX100 occurred and the influent concentration of TX100 was greater than the critical enhanced flushing concentration (CEFC). The sorption of surfactant onto soils and the subsequent partitioning of contaminants into soil-sorbed surfactant had a significant effect on the solute equilibrium distribution coefficient (KD) and thus the flushing efficiency for phenanthrene. A model was developed to predict KD and CEFC values for simulating the performance of surfactant-enhanced flushing for contaminated soils. These results are of practical interest in developing effective and safe surfactant-enhanced remediation technologies.     

Enhanced desorption of phenanthrene from contaminated soil using anionic/nonionic mixed surfactant

A new approach using an anionic/nonionic mixed surfactant, sodium dodecyl sulphate (SDS) with Triton X-100 (TX100), was utilized for the desorption of phenanthrene from an artificial contaminated natural soil in an aim to improve the efficiency of surfactant remediation technology. The experimental results showed that the presence of SDS not only reduced the sorption of TX100 onto the natural soil, but also enhanced the solubilization of TX100 for phenanthrene, both of which resulted in the distribution of phenanthrene in soil-water systems decreasing with increasing mole fraction of SDS in surfactant solutions. These results can be attributed to the formation of mixed micelles in surfactant solution and the corresponding decrease in the critical micelle concentration of TX100 in mixed solution. The batch desorption experiments showed that the desorption percentage of phenanthrene from the contaminated soil with mixed solution was greater than that with single TX100 solution and appeared to be positively related to the mole fraction of SDS in surfactant solution. Thus, the anionic/nonionic mixed surfactants are more effective for the desorption of phenanthrene from the contaminated soil than a single nonionic surfactant.     

Correlations between experimental and predicted equilibrium distribution coefficient of chlorobenzene and chlorophenol compounds in soil-water systems using partial solubility parameters

Many pesticides are degraded to become chlorinated aromatic compounds in soils. Equilibrium distribution of chlorobenzene and chlorophenol compounds in soil-water systems of Yangmingshan loam, Pingcheng silty clay loam and Annei silty loam was studied with the integral distribution equilibrium equation involving the partial solubility parameters of the chemicals. If the adsorption of chemicals on soils is partitioning in soil organic matter surrounding the soil mineral particles, the absorption constant (Kd) of a chemical in soil-water system could be stated as the distribution coefficient (or partition constant, Koc) of the chemical in the two adjunct immiscible phases--water and soil organic matter. The distribution coefficient (Koc) of chemicals calculated from the integral distribution equilibrium equation agrees well with the experimental adsorption coefficient (Kd, or experimental Koc) of chemicals determined in this study, for all the three different types of soils in water according to multiple-regression analysis. Reference data of Karger or Tijssen are employed to estimate the Koc for both polar and non-polar chemicals. The integral distribution equilibrium equation can exactly describe the distribution behavior of nonionic compound of chlorobenzenes and chlorophenols in soil-water systems.     

Effects of SOM, surfactant and pH on the sorption-desorption and mobility of prometryne in soils

Sorption and desorption of the herbicide prometryne in two types of soil subjected to the changes of pH and soil organic matter and surfactant were investigated. The sorption and desorption isotherms were expressed by the Freundlich equation. Freundlich K_f and n values indicate that soil organic matter was the major factor affecting prometryne behavior in the test soils. We also quantified the prometryne sorption and desorption behavior in soils, which arose from the application of Triton X-100 (TX100), a nonionic surfactant and change in pH. Application of TX100 led to a general decrease in prometryne sorption to the soils and an increase in desorption from the soils when applied in dosages of the critical micella concentration (CMC) 0.5, 1 and 2. At the concentration below the CMC, the non-ionic surfactant showed a tendency to decrease prometryne sorption and desorption. It appeared that TX100 dosages above CMC were required to effectively mobilize prometryne. Results indicate that the maximum prometryne sorption and minimum prometryne desorption in soils were achieved when the solution pH was near its pK_a. Finally, the influence of TX100 on the mobility of prometryne in soils using soil thin-layer chromatography was examined.     

Synergistic solubilization of polycyclic aromatic hydrocarbons by mixed anionic-nonionic surfactants

Water solubility enhancements of naphthalene (Naph), acenaphthylene (Acen), anthracene (An), phenanthrene (Phen) and pyrene (Py) by micellar solutions of single and mixed anionic-nonionic surfactants were measured and compared. Effects of typical inorganic ions, such as NH(4)(+), Na(+) and Mg(2+) coexisted with the organic pollutants (in soils) on water solubilities of polycyclic aromatic hydrocarbons (PAHs) in the presence of single and mixed surfactants were also investigated. Solubilities of PAHs in water are greatly enhanced in a linear fashion by each of Triton X-100 (TX100), Triton X-305 (TX305), Brij 35, and sodium dodecyl sulfate (SDS). Solubility enhancement efficiencies of surfactants above the critical micelle concentration (CMC) follow the order of TX100>Brij 35>TX305>SDS. PAHs are solubilized synergistically in mixed anionic-nonionic surfactant solutions, especially at low surfactant concentrations. The synergistic power of the mixed surfactants is SDS-TX305>SDS-Brij 35>SDS-TX100. Synergistic effect of a given mixed-surfactant solution on different PAHs also appears to be linearly related to the solute logK(ow). The noted synergism for the mixed surfactants is attributed to the formation of mixed micelles, the lower CMC of the mixed-surfactant solutions, and the increase of the solute's molar solubilization ratio or micellar partition coefficients (K(mc)) because of the lower polarity of the mixed micelles. Suitable quantity of inorganic cations can enhance the solubilization capacities of anionic-nonionic mixed surfactants, the effect being Mg(2+)>NH(4)(+)>Na(+). The water solubility of pyrene was slightly increased by anthracene and significantly increased by 1,2,3-TCB in the presence of SDS-Brij 35. Mixed surfactants may improve the performance of surfactant-enhanced remediation of soils and sediments by decreasing the applied surfactant level and thus the remediation cost.     

Solubilization of DNAPLs by mixed surfactant: reduction in partitioning losses of nonionic surfactant

Efforts to remediate the dense nonaqueous phase liquids (DNAPLs) by mobilizing them face with risks of driving the contaminants deeper into aquifer zones. This spurs research for modifying the approach for in situ remediation. In this paper, a novel solubilization of DNAPLs by mixed nonionic and anionic surfactant, Triton X-100 (TX100) and sodium dodecylbenzene sulfonate (SDBS), was presented and compared with those by single ones. Given 1:40 phase ratio of DNAPL:water (v/v) and the total surfactant concentration from 0.2 to 10gl(-1), mixed TX100-SDBS at the total mass ratios of 3:1, 1:1 and 1:3 exhibited significant solubilization for the DNAPLs, trichloroethene (TCE), chlorobenzene (CB) and 1,2-dichlorobenzene (1,2-DCB). The solubilization extent by mixed TX100-SDBS was much larger than by single TX100 and even larger than by single SDBS at the ratios of 1:1 and 1:3, respectively. TX100 partitioning into the organic phase dictated the solubilization extent. The TX100 losses into TCE, CB and 1,2-DCB phases were more than 99%, 97% and 97% when single TX100 was used. With SDBS alone, no SDBS partitioned into DNAPLs was observed and in mixed systems, SDBS decreased greatly the partition loss of TX100 into DNAPLs. The extent of TX100 partition decreased with increasing the amount of SDBS. The mechanism for reduction of TX100 partition was discussed. TX100 and SDBS formed mixed micelles in the solution phase. The inability of SDBS to partition into DNAPLs and the mutual affinity of SDBS and TX100 in the mixed micelle controlled the partitioning of TX100 into DNAPL phase. The work presented here demonstrates that mixed nonionic-anionic surfactants would be preferred over single surfactants for solubilization remediation of DNAPLs, which could avoid risks of driving the contaminants deeper into aquifers and decrease the surfactant loss and remediation cost.     

Phenanthrene partitioning in sediment–surfactant–fresh/saline water systems

The objective of this study was to investigate the influence of salinity on the effectiveness of surfactants in the remediation of sediments contaminated with phenanthrene (PHE). This is an example of a more general application of surfactants in removing hydrophobic organic compounds (HOCs) from contaminated soil/sediment in saline environments via in-situ enhanced sorption or ex-situ soil washing. Salinity effects on surfactant micelle formation and PHE partitioning into solution surfactant micelles and sorbed surfactant were investigated. The critical micelle concentration of surfactants decreased, and PHE partition between surfactant micelles and water increased with increasing salinity. Carbon-normalized partition coefficients (K_ss) of PHE onto the sorbed cationic surfactant increased significantly with increasing salinity, which illustrates a more pronounced immobilization of PHE by cationic surfactant in a saline system. Reduction of PHE sorption by anionic surfactant was more pronounced in the saline system, indicating that the anionic surfactant has a higher soil washing effectiveness in saline systems.     

Sorption of the fumigant 1,3-dichloropropene on soil

The fumigant 1,3-dichloropropene (1,3-D) is considered a major replacement to methyl bromide, which is to be phased out of use in the United States by 2005. The main purpose of this study was to evaluate soil-water partitioning of 1,3-D in two California agricultural soils (Salinas clay loam and Arlington sandy loam). The partition coefficients (Kd and Kf) were determined by directly measuring the concentration of 1,3-D in the solid phase (Cs) and aqueous phase (Cw) after batch equilibration. In the Salinas clay loam, the Kf of cis-1,3-D in adsorption and desorption isotherms was 0.47 and 0.54, respectively, with respective values of 0.39 and 0.49 for trans-1,3-D. This slight hysteric effect suggests that a different range of forces are involved in the adsorption and desorption process. Since n was near unity in the Freundlich equation, the Freundlich isotherms can also be approximated using the liner isotherm. At 25 degrees C, the Kd of the 1,3-D isomers in both soils ranged from 0.46 to 0.56, and the Koc (organic matter partition coefficient) ranged from 58 to 70. The relatively low Kd values and a Koc that falls within the range of 50-150, suggests that 1,3-D is weakly sorbed and highly mobile in these soils. Understanding the sorption behavior of 1,3-D in soil is important when developing fumigation practices to reduce the movement of 1,3-D to the air and groundwater.     

Effect of a cationic surfactant on the volatilization of PAHs from soil

Purpose

Cationic surfactants are common in soils because of their use in daily cosmetic and cleaning products, and their use as a soil amendment for the mitigation and remediation of organic contaminated soils has been proposed. Such surfactant may affect the transfer and fate of organic contaminants in the environment. This study investigated the effect of a cationic surfactant, dodecylpyridinium bromide (DDPB), on the volatilization of polycyclic aromatic hydrocarbons (PAHs) from a paddy soil.

Materials and methods

The volatilization of PAHs from moist soil amended with different concentrations of DDPB was tested in an open system. The specific effects of DDPB on the liquid?Cvapor and solid?Cvapor equilibriums of PAHs were separately investigated in closed systems by headspace analysis.

Results and discussion

DDPB affects both liquid?Cvapor and solid?Cvapor processes of PAHs in soil. At DDPB concentrations below the critical micelle concentration (CMC), movement of PAHs from the bulk solution to the gas?Cliquid interface appeared to be facilitated by interaction between PAHs and the surfactant monomers adsorbed at the gas?Cliquid interface, promoting the volatilization of PAHs from solution. However, when DDPB was greater than the CMC, volatilization was inhibited due to the solubilization of PAHs by micelles. On the other hand, the formation of sorbed surfactant significantly inhibited the solid?Cvapor volatilization of PAHs.

Conclusions

The overall effect of the two simultaneous effects of DDPB on liquid?Cvapor and solid?Cvapor processes was a decreased volatilization loss of PAHs from soil. Inhibition of PAH volatilization was more significant for the soil with a lower moisture content.     

Removal of vaporous naphthalene using polyoxyethylenated nonionic surfactants

Previous research has demonstrated that an anionic surfactant can increase the solubility of the vapor phases of both naphthalene and sulfur dioxide in water. This study examines the feasibility of removing polycyclic aromatic hydrocarbons (PAHs) during gas absorption by adding the polyoxyethylenated nonionic surfactants tetraethylene glycol monodecyl ether (C10E4), octaethylene glycol monodecyl ether (C10E8), and octaethylene glycol monotetradecyl ether (C14E8), to water. The apparent solubility and absorption rates of naphthalene in surfactant solution were slightly higher than in pure water at a concentration lower than the critical micelle concentration (CMC). However, the apparent equilibrium naphthalene solubility increased linearly in proportion to the concentrations of nonionic surfactants because of the solubilization effect of micelles at concentrations above the CMC. The solubilization effect exceeded that of the reduced mass transfer coefficient, increasing the rate of absorption of vaporous naphthalene. For the four surfactants, the capacity to solubilize naphthalene was in the order C10E4 > C14E8 > C10E8 > sodium dodecyl sulfate (SDS) and was related to the hydrophile-lipophile balance values of the surfactants. The enrichment factors, which can express the degree of naphthalene solubility in solution, were 6.09-14.2 at a surfactant concentration of 0.01 M for the three polyoxyethylenated nonionic surfactants. Empirical findings confirm that adding nonionic surfactants increases the absorption efficiency of hydrophobic organic compounds (HOCs) using spray or packed tower.     

Effect of phosphate addition on the sorption-desorption reaction of selenium in Japanese agricultural soils

Desorption levels of soil-sorbed selenium (Se) were studied by adding phosphate to 22 typical Japanese agricultural soils. Soil-soil solution distribution coefficients of Se (Kd-Se) were measured using a batch process as an index of Se sorption level, adding 75Se as a tracer. After the Kd measurement, extraction of soil-sorbed 75Se with a 0.1 M or 1 M Na2HPO4 solution followed to determine the amount of 75Se desorbed by the phosphate. When the 0.1 M Na2HPO4 solution was used, 18-70% of soil-sorbed Se was extracted (average: 47%). However, when the 1 M Na2HPO4 solution was used, 27-83% of soil-sorbed Se was extracted (average: 57%). The observed 75Se desorption percentage indicated the maximum Se removability by phosphate addition. The desorption percentage of Se with 1 M Na2HPO4 correlated with Kd-Se values, suggesting that the soil sample with higher Kd-Se contained more reactive components for phosphate-sorption than the soil sample with lower Kd-Se. To evaluate the effect of phosphate concentration on the Se sorption, the Kd-Se was measured for two typical soils under different levels of phosphate (0.1-10 mM PO4). The Kd values were decreased by phosphate addition for both soils. The Kd decrease was observed even for just 1 mM PO4. The phosphate addition with 1 mM PO4 is the same level as in P fertilizer applied to paddy fields in Japan. Therefore, it was suggested that Se desorption should occur in Japanese soils due to the phosphate input.     

Equilibrium partitioning of PCB congeners in the water column: Field measurements from the Hudson River

The environmental behavior of hydrophobic organic compounds in water is driven by partitioning between dissolved and sorbed phases. Partitioning behavior of a compound is often based on empirical relationships to other properties of the chemical, such as water solubility and octanol-water partition coefficients, but actual partitioning in the environment may differ significantly from such predictions. We conducted intensive studies of the distribution of PCBs in the fresh water portion of the Hudson River, using sensitive capillary-column gas chromatography methods to calibrate and resolve quantitations for 90 PCB congeners in 48 samples at 10 locations. A linear equilibrium model of PCB congener partitioning, when corrected for temperature and suspended-matter organic carbon content, provides a good representation of phase distribution. When particulate-phase concentrations are predicted from dissolved concentrations with a two-phase model, the predictions are unbiased for the majority of samples and the average percent difference between observed and predicted particulate concentrations is ±43 percent. Estimated in situ partition coefficients show systematic differences from partition coefficients predicted from octanol-water partitioning. Partitioning to colloids appears to be a significant component of total concentration for mono- and dichlorobiphenyls, but not for more highly chlorinated congeners.The colloidal fraction may still cause significant overestimation of the bioavailable fraction for more hydrophobic congeners when a two-component model is used.     

Non-steady state partitioning of dry cleaning surfactants between tetrachloroethylene (PCE) and water in porous media

Trapped organic solvents, in both the vadose zone and below the water table, are frequent sources of environmental contamination. A common source of organic solvent contamination is spills, leaks, and improper solvent disposal associated with dry cleaning processes. Dry cleaning solvents, such as tetrachloroethylene (PCE), are typically enhanced with the addition of surfactants to improve cleaning performance. The objective of this work was to examine the partitioning behavior of surfactants from PCE in contact with water. The relative rates of surfactants partitioning and PCE dissolution are important for modeling the behavior of waste PCE in the subsurface, in that they influence the interfacial tension of the PCE, and how (or if) interfacial tension changes over time in the subsurface. The work described here uses a flow-through system to examine simultaneous partitioning and PCE dissolution in a porous medium. Results indicate that both nonylphenol ethoxylate nonionic surfactants and a sulfosuccinate anionic surfactant partition out of residual PCE much more rapidly than the PCE dissolves, suggesting that in many cases interfacial tension changes caused by partitioning may influence infiltration and distribution of PCE in the subsurface. Non-steady-state partitioning is found to be well-described by a linear driving force model incorporating measured surfactant partition coefficients.     

Surfactant solubilization of hydrophobic compounds in soil and water

Reductions in the apparent soil-water partition coefficients (K_d ^*) for 28 polychlorinated biphenyls (PCBs) caused by the surfactant sodium dodecylsulphate (SDS) in the aqueous phase were studied. Above the critical micelle concentration (CMC) of the surfactant, K_d ^* was reduced by 2–3 orders of magnitude, but even far below CMC at environmentally relevant surfactant concentrations significant reductions in K_d ^* were observed. The plot of the soil-water partition coefficient (K_d) divided by K_d ^* versus the concentration of SDS allowed for the calculation of monomer (K_mn ^oc) and micellar (K_mc ^oc) surfactant-water partition coefficients normalized to organic carbon for each PCB congener. K_mn ^oc values were comparable with published values for the partition of PCBs between natural dissolved organic matter and lake water. K_mc ^oc values were up to 30 times higher than K_mn ^oc values and comparable with published octanol-water distribution coefficients. The findings of the present study underline the potential of surfactants at concentrations below their CMC to mobilize otherwise strongly bound hydrophobic compounds in soil-water systems.     

Partitioning of polycyclic aromatic hydrocarbons to solid-sorbed nonionic surfactants

The partition of hydrophobic organic compounds (HOCs) into solid-sorbed surfactant has a crucial role in describing and predicting the distribution of HOCs in solid-water-surfactant systems. The experimental results of this study indicated that the partition coefficients of polycyclic aromatic hydrocarbons (PAHs) into the solid-sorbed surfactant (Ksm) increased with an increase in the sorption amount of surfactants onto solid and reached a stable maximum value (Km sm) at the sorption of surfactants in saturation state, at which the solid surface was completely covered with the surface micelle (or admicelle). The fitted Km sm values for PAHs with different surfactants were found to have a good linear relationship with the corresponding partition coefficient of PAHs to surfactant micelles in solution (Kmc), and then a model was developed to describe and predict the distribution of PAHs in solid-water-surfactant systems. These results are of practical interest for developing effective and safe surfactant-enhanced remediation technologies.     

Antimony mobility in Japanese agricultural soils and the factors affecting antimony sorption behavior

The mobility of antimony (Sb) in Japanese agricultural soils was studied by radiotracer experiments using 124Sb tracer. The soil-solution distribution coefficients (Kd) of Sb were measured for 110 soil samples. These Kds ranged from 1 to 2065 L kg(-1); the geometric mean was 62 L kg(-1) excluding one extremely high value, 2065 L kg(-1). Experimental measurement of Kd showed a decrease with both increasing pH and increasing phosphate concentration. The latter suggested that one aspect of the Sb sorption phenomena in Japanese soil was influenced by specific adsorption of anions such as phosphate. However, other aspects could not be explained by this specific adsorption mechanism, because only 20-40% of soil-sorbed Sb could be extracted by phosphate solution.     

Determination of solid-liquid partition coefficients (Kd) for the herbicides isoproturon and trifluralin in five UK agricultural soils

Isoproturon and trifluralin are herbicides of contrasting chemical characters and modes of action. Standard batch sorption procedures were carried out to investigate the individual sorption behaviour of 14C-isoproturon and 14C-trifluralin in five agricultural soils (1.8-4.2% OC), and the soil solid-liquid partition coefficients (Kd values) were determined. Trifluralin exhibited strong partitioning to the soil solid phase (Kd range 106-294) and low desorption potential, thus should not pose a threat to sensitive waters via leaching, although particle erosion and preferential flow pathways may facilitate transport. For isoproturon, soil adsorption was low (Kd range 1.96-5.75) and desorption was high, suggesting a high leaching potential, consistent with isoproturon being the most frequently found pesticide in UK surface waters. Soil partitioning was directly related to soil organic carbon (OC) content. Accumulation isotherms were modelled using a dual-phase adsorption model to estimate adsorption and desorption rate coefficients. Associations between herbicides and soil humic substances were also shown using gel filtration chromatography.     

Surfactant-induced mobilisation of trace metals from estuarine sediment: implications for contaminant bioaccessibility and remediation

The mobilisation of metals (Al, Fe, Cd, Cu, Mn, Ni, Pb, Sn, Zn) from contaminated estuarine sediment has been examined using commercially available surfactants. Metal release by the anionic surfactant, sodium dodecyl sulphate (SDS), increased with increasing amphiphile concentration up to and above its critical micelle concentration (CMC). Metal mobilisation by the bile acid salt, sodium taurocholate, and the nonionic surfactant, Triton X-100, however, did not vary with amphiphile concentration. SDS was the most efficient surfactant in mobilising metals from the sample, and Cd, Cu and Ni were released to the greatest extents (12-18% of total metal at [SDS] > CMC). Metal mobilisation appeared to proceed via complexation with anionic amphiphiles and denudation of hydrophobic host phases. Surfactants may play an important role in the solubilisation of metals in the digestive environment of deposit-feeding animals and, potentially, in the remediation of metal-contaminated soil and sediment.     

Sorption of isoxaflutole diketonitrile degradate (DKN) and dicamba in unsaturated soil

When analyzing the sorption characteristics of weakly sorbing or labile pesticides, batch methods tend to yield a high margin of error attributable to errors in concentration measurement and to degradation, respectively. This study employs a recently developed unsaturated transient flow method to determine the sorption of isoxaflutole's herbicidally active diketonitrile degradate (DKN) and dicamba. A 20-cm acrylic column was packed with soils with varied texture that had been uniformly treated with 14C-labeled chemical.The antecedent solution herbicide in equilibrium with sorbed phase herbicide was displaced by herbicide-free water, which was infiltrated into the column. Sorption coefficients, Kd, were obtained from a plot of total herbicide concentration in the soil versus water content in the region where the antecedent solution accumulated. DKN Kd values were approximately 2-3 times (average Kd = 0.71 L kg-1) greater using the unsaturated transient flow method as compared to the batch equilibration method in clay loam (Kd = 0.33 L kg-1), but similar for the two methods in sand (0.12 vs 0.09 L kg-1) soils. Dicamba Kd values were 3 times greater using the unsaturated transient flow method as compared to the batch equilibration method in the clay loam soil (0.38 vs 0.13 L kg-1), however, the Kd values were the same for the two methods in the sand (approximately 0.06 L kg-1). This demonstrates that to determine sorption coefficients for labile hydrophilic pesticides, an unsaturated transient flow method may be a suitable alternative to the batch method. In fact, it may be better in cases where transport models have overpredicted herbicide leaching when batch sorption coefficients have been used.     

Solubilization of nitrotoluenes in micellar nonionic surfactant solutions

A key factor in selecting surfactants to enhance chemical or biological transformation or physical removal of an organic pollutant from contaminated soil is knowledge of the pollutant's solubility behavior in the surfactant solution. This study investigated the influence of nonionic surfactant structure on the solubility of 4-nitrotoluene (NT), 2,3-dinitrotoluene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, and 2,4,6-trinitrotoluene (TNT) at room temperature. For a series of alkyl phenol ethoxylates (Tergitol NP-8 to NP-40), decreasing the ethoxylate chain length increased the solubility of these nitrotoluenes by a factor of two or less in 10 g l(-1) surfactant solutions, but did not significantly change their molar solubilization ratios (MSR, e.g. 0.02 for TNT) or their micelle-water partition coefficients (K(m), e.g. 3.4 for TNT). For Tergitol NP-8 solutions ranging from 1.0 to 12.4 g l(-1), no enhancement in NT solubility was found, suggesting that the cloud point was reached. The MSRs for Tween 80 were higher than those of Tween 20 and the MSRs of Brij-58 were higher than those for Brij-35. When comparing solutes, NT had the highest solubility and MSR (0.28-0.41), while TNT had the lowest solubility and MSR (0.02-0.03). A linear relationship between K(m) values and octanol-water partition coefficients based on Triton X-100 predicted the logK(m) values within 0.5 of their measured values. A linear solvation free energy correlation for K(m) suggested the importance of solute volume and effective hydrogen bond basicity in the partitioning process while implying that the nitrotoluenes are solubilized in a polar portion of the micelle.