Biosurfactant-enhanced solubilization of NAPL mixtures.

Remediation of nonaqueous phase liquids (NAPLs) by conventional pump-and-treat methods (i.e., water flushing) is generally considered to be ineffective due to low water solubilities of NAPLs and to mass-transfer constraints. Chemical flushing techniques, such as surfactant flushing, can greatly improve NAPL remediation primarily by increasing the apparent solubility of NAPL contaminants. NAPLs at hazardous waste sites are often complex mixtures. However, the equilibrium and nonequilibrium mass-transfer characteristics between NAPL mixtures and aqueous surfactant solutions are not well understood. This research investigates the equilibrium solubilization behavior of two- and three-component NAPL mixtures (containing akylbenzenes) in biosurfactant solutions. NAPL solubilization is found to be ideal in water (i.e., obeys Raoult's Law), while solubilization in biosurfactant solutions was observed to be nonideal. Specifically, the relatively hydrophobic compounds in the mixture experienced solubility enhancements that were greater than those predicted by ideal enhanced solubilization theory, while the solubility enhancements for the relatively hydrophilic compounds were less than predicted. The degree of nonideality is shown to be a nonlinear function of the NAPL-phase mole fraction. Empirical relationships based on the NAPL-phase mole fraction and/or micelle-aqueous partition coefficients measured in single-component NAPL systems are developed to estimate values for the multicomponent partition coefficients. Empirical relationships that incorporate both the NAPL-phase mole fraction and single-component partition coefficients yield much improved estimates for the multicomponent partition coefficient.

Mathematical modeling of air sparging for subsurface remediation: state of the art.

A review of published mathematical models used to simulate air sparging is provided. Applicability of the models, efforts to test the models using experimental data and contributions of modeling efforts to the practice of air sparging are also discussed. Compartmentalized lumped-parameter models and multiphase flow models have dominated air-sparging modeling efforts. In essence, each class of models requires the assumption of a continuum over some model domain. Each approach has significant benefits as well as some inherent disadvantages. Based on the literature, both lumped-parameter modeling and multiphase-flow modeling have been successful in improving our theoretical understanding of the air-sparging process and in facilitating practical development of sparging systems. Lumped-parameter models are simpler to use, and can lend considerable insight to sparging operations. Multiphase flow models have the potential to offer a more realistic simulation of the airflow process, but may require a considerable amount of data collection for model input. The literature suggests that for any air-sparging model to be useful for field applications, detailed model calibration is necessary. It is recommended that models incorporate, in some fashion, the diffusion and dispersion of contaminants to macro-scale air channels, and nonequilibrium interphase mass transfer of contaminants. These mass-transfer-limited processes are frequently listed as causes for the "tailing" of vapor-extraction effluent contaminant concentrations that are frequently observed during field applications. However, time-varying mixing of relatively clean and contaminated vapors in the extraction system may also explain this tailing. Geophysical imaging techniques and inverse modeling combined with air-sparging pilot tests and measurement of traditional hydrogeologic parameters may allow for successful modeling efforts.

Clinical endoscopic evaluation of the gastroduodenal tolerance to (R)- ketoprofen, (R)- flurbiprofen, racemic ketoprofen, and paracetamol: a randomized, single-blind, placebo-controlled trial.

Ketoprofen, a nonsteroidal anti-inflammatory drug (NSAID) of the 2-arylpropionic acid class, causes gastroduodenal hemorrhages and erosions in 10-15% of patients. The (S)- enantiomer exhibits most of the anti-inflammatory properties, with concomitant gastrointestinal toxicity. The (R)- enantiomer, however, was recently found to have analgesic properties independent of prostaglandin inhibition. Seventy-two healthy male volunteers not receiving NSAIDs, alcohol, or anti-ulcer drugs, were enrolled in a randomized, investigator-blind, placebo-controlled trial to evaluate the gastroduodenal tolerance of (R)- ketoprofen 100 mg b.i.d., (R)- flurbiprofen 100 mg b.i.d., racemic ketoprofen 100 mg b.i.d., and paracetamol 1,000 mg b.i.d. Gastroduodenal endoscopies at baseline and after 2.5 days of dosing were used to detect newly occurring hemorrhages and erosions. Adverse events were also recorded. The incidence of submucosal hemorrhages was 4/16 in the (R)- ketoprofen group, 5/16 in the (R)- flurbiprofen group, 12/16 in the racemic ketoprofen group, 1/16 in the paracetamol group, and 1/8 in the placebo group. The incidence of erosions was 2/16 in the (R)- ketoprofen group, 4/16 in the (R)- flurbiprofen group, 10/16 in the racemic ketoprofen group, 0/16 in the paracetamol group, and 2/8 in the placebo group. The differences in hemorrhages and erosions among treatments were statistically significant (gastric hemorrhages P = 0.0008; duodenal hemorrhages P = 0.00062; gastric erosions P = 0.0004; duodenal erosions P = 0.0062, Kruskal-Wallis test). At 100 mg b.i.d., (R)- ketoprofen caused fewer gastroduodenal hemorrhages and erosions than racemic ketoprofen (P = 0.019, P = 0.0112, P = 0.0097, P = 0.0139 for gastric, duodenal hemorrhages and gastric, duodenal erosions, respectively). The difference between 100 mg b.i.d. (R)- ketoprofen and 100 mg b.i.d. (R)- flurbiprofen was not statistically significant. The dissociation between analgesic and anti-inflammatory properties for (R)- ketoprofen suggests that it may represent a unique analgesic with a favorable safety profile.

Preclinical enantioselective pharmacology of (R)- and (S)- ketorolac.

Many of the nonsteroidal anti-inflammatory drugs (NSAIDs) are marketed as racemic mixtures, composed of (R)- and (S)- enantiomers. Racemic NSAIDs are potent cyclooxygenase (COX) inhibitors only through the action of the (S)- enantiomers, as the (R)- enantiomers do not exhibit COX inhibition. However, the (R)- enantiomer of ketoprofen exhibits potent analgesic activity and minimal ulcerogenic potential. To extend these observations, we examined the (R)- and (S)- enantiomers of RS- ketorolac, (S)- ketorolac exhibited potent COX1 and COX2 enzyme inhibition, whereas (R)- ketorolac was > 100-fold less active on both COX subtypes. Both enantiomers did not affect norepinephrine or serotonin uptake sites, and nitric oxidase or lipoxygenase activities, nor did they demonstrate any affinity for opioid receptors (mu, delta, or kappa). In experimental models, (S)- ketorolac exhibited about 10-fold greater activity than (R)- ketorolac in the murine phenylquinone writhing model. In this model, morphine sulfate was effective at much lower doses, however, and neither (R)- nor (S)- ketorolac showed any morphine-sparing effect. In the rat gait test for analgesia in the foot paw after injection of brewers yeast suspension, neither (R)- nor (S)- ketorolac affected paw volume. However, both provoked changes in gait scores, the (S)- enantiomer being 30-fold more potent than the (R)- enantiomer. A similar reduction was observed with respect to ulcerogenic potential, measured by direct microscopic changes after test conclusion. These findings suggest that (R)- ketorolac may possess analgesic activity that is independent of COX inhibition and may be associated with reduced ulcerogenic potential compared to effects exhibited by (S)- ketorolac.