Nonpolar Organic Compounds Research Articles

Preparations of organobentonite using nonionic surfactants

Due to hydrophilic environment at its surface, natural bentonite is an ineffective sorbent for nonpolar nonionic organic compounds in water even though it has high surface area. The surface properties of natural bentonite can be greatly modified by simple ion-exchange reactions with large organic cations (cationic surfactants) and this organobentonite is highly effective in removing nonionic organic compounds from water. Cationic surfactant derived organobentonites have been investigated extensively for a wide variety of environmental applications. In this study, the preparation of organobentonite using nonionic surfactants has been investigated for the first time. Results indicate that nonionic surfactants intercalates into the interlamellar space of bentonite and may demonstrate higher sorption capacity than cationic surfactant. It is possible to create large interlayer spacing and high organic carbon content organobentonite by use of nonionic surfactants with suitable balance between the hydrocarbon and ethylene oxide chain lengths. In addition, nonionic surfactant derived organobentonites are more chemically stable than cationic surfactant derived organobentonites.

Survey of volatile organic compounds associated with automotive emissions in the urban airshed of São Paulo, Brazil

The Metropolitan Region of São Paulo (MRSP), Brazil, is one of the largest metropolitan areas in the world (population 17 million, approx.) and relies heavily on alcohol-based fuels for automobiles. It is estimated that about 40% of the total volume of fuel is ethanol with some vehicles using pure ethanol and others a gasoline/ethanol blend. As such, São Paulo is an excellent example of an oxygenates-dominated airshed of mobile sources and is most likely indicative of the future in heavily populated areas in the US such as Los Angeles where “oxy-fuels” are becoming an important replacement for the conventional pure petroleum-based fuels. In this work, we surveyed the ambient air to identify and quantify the organic compounds associated with the evaporative and exhaust emissions of these fuels and to begin to understand the potential for human exposure. Because this was an initial test without detailed prior knowledge of the airshed of the area, we applied two different air sampling methods for various time periods to assess the ambient concentrations of a variety of polar and nonpolar volatile organic compounds (VOCs). For quality assurance (QA), we collected all the samples in duplicate (whole-air samples in Summa canisters and adsorbent-based samples on Perkin-Elmer Air Toxics tubes) at various flow rates to test performance. All samples were collected over identical time frames, typically for 1-, 2-, and 4-h periods per day at six different locations over a period of 1 week. Overall São Paulo results demonstrate that mean concentrations of single-ring aromatics are 2–3 times higher, volatile aldehydes are 5–10 times higher, and simple alcohols 10–100 times higher as compared to results of a recent study performed by EPA in the Los Angeles basin. C 4–C 11 n-alkanes were only slightly elevated in São Paulo.

FINGERPRINTING OF THE DEVELOPMENT OF AEROBIC COMPOSTING PROCESSES OF AGRICULTURAL WASTES BY ON-LINE COMBINATION OF LIQUID CHROMATOGRAPHY AND MASS SPECTROMETRY

Liquid chromatography (LC) was employed in conjunction to mass spectrometry (MS) to develop a straightforward LC-MS procedure for monitoring the variation of functionalized nonpolar organic compounds during the development of an aerobic composting process of agricultural wastes. The LC separation was performed by a reversed-phase microbore HPLC octadecyl-silica column, which was eluted by a linear acetonitrile gradient in water. The reversed-phase HPLC column was connected on-line to a triploquadrupole mass spectrometer by an atmospheric pressure ionization interface. Weighed amounts of agricultural wastes sampled at different time intervals during the aerobic composting process were extracted by dichloromethane and analyzed by LC-MS. The resulting fingerprinting offered a means to monitor the variations of functionalized nonpolar compounds during the aerobic process and indicate the presence of compounds that are not degraded by the biotranformation, such as ursolic acid and β-sitosterol.

Organophilicity of MCM-41 adsorbents studied by adsorption and temperature-programmed desorption

In this paper, the organophilic property of MCM-41 was studied and compared with hydrophobic silicalite-1 using adsorption and temperature-programmed desorption (TPD) methods. The surface heterogeneity of MCM-41 was evaluated in terms of activation energy for desorption ( E d) and isosteric heat of adsorption ( q st) . Results show that MCM-41 has a higher affinity to polar organic compounds than to non-polar organics while silicalite-1 has a higher affinity to non-polar organic compounds than to polar organics. This organophilic behaviour of MCM-41 is attributed to its surface heterogeneity.

Supercritical fluid extraction of the non-polar organic compounds in meteorites

The carbonaceous chondrite meteorites contain a variety of extraterrestrial organic molecules. These organic components provide a valuable insight into the formation and evolution of the solar system. Attempts at obtaining and interpreting this information source are hampered by the small sample sizes available for study and the interferences from terrestrial contamination. Supercritical fluid extraction represents an efficient and contamination-free means of isolating extraterrestrial molecules. Gas chromatography-mass spectrometry analyses of extracts from Orgueil and Cold Bokkeveld reveal a complex mixture of free non-polar organic molecules which include normal alkanes, isoprenoid alkanes, tetrahydronaphthalenes and aromatic hydrocarbons. These organic assemblages imply contributions from both terrestrial and extraterrestrial sources.

Polar and non-polar volatile organic compounds (VOCs) in urban Algiers and saharian sites of Algeria

For the first time, polar and non-polar organic compounds from C 4 to C 20 have been identified and quantified in one urban and two saharan sites located in Algeria. They were collected on adsorption traps filled with graphitic carbons and analyzed by high-resolution gas chromatography–mass spectrometry after thermal desorption. More than 190 compounds released by man-made and biogenic sources or formed in air by degradation of photochemical smog precursors were identified in the city center of Algiers. Some of them were never reported before. During our determinations, high levels of pollution characterized the city. Transport of anthropogenic pollutants together with some biogenic emission from date palm trees was mainly responsible for the levels of VOCs measured in Melika oasis located at the entrance of the Sahara desert. Background tropospheric levels of VOCs were instead detected in Bouchene sandy site of the Sahara desert where no biogenic sources were present.

Steam- or carbon dioxide-activated carbons from almond shells: physical, chemical and adsorptive properties and estimated cost of production

A series of steam- or carbon dioxide (CO 2)-activated, granular activated carbons (GACs) were made from almond shells using six different activation or activation/oxidation conditions for each series. Unoxidized/oxidized pairs of GACs were compared among treatments and to two commercial GACs in order to determine the relative value of the carbons. Comparative terms included yield, surface area, attrition, surface charge, copper ion (Cu 2+) uptake, adsorption of a mixture of six polar and non-polar organic compounds and an estimated cost of carbon production. Of the six conditions investigated for steam activation, two treatments consisting of a 1 h pyrolysis at either 700°C or 800°C, followed by a 2 h activation at 800°C with the introduction of water at a rate of 7.0 ml/min were the best overall performing unoxidized/oxidized pairs in terms of copper ion or organics adsorption, respectively. Of the six conditions investigated for carbon dioxide activation, a treatment consisting of a 1 h pyrolysis at 700°C, followed by a 2 h activation at 800°C using a 75% CO 2/25% N 2 gas mixture was the best overall performing unoxidized/oxidized pair. Our estimated costs of production indicate that steam-activated, unoxidized and oxidized carbons appear to be the most economical GACs to manufacture and also the most economical for removal of copper ions and organic compounds.

Comparison of nutshell granular activated carbons to commercial adsorbents for the purge-and-trap gas chromatographic analysis of volatile organic compounds

Granular activated carbons (GACs) made from agricultural by-products were investigated as adsorbents for short path thermal desorption gas chromatographic analysis of selected polar and nonpolar organic compounds. GACs made from macadamia nut, black walnut and hazelnut shells were compared to four commercially available adsorbents, namely, Tenax TA, Carboxen 569, Carbosieve SIII and coconut charcoal for their properties in purge-and-trap analysis. Adsorption values and breakthrough volumes were calculated for compounds from C 3 and C 6–C 10. GACs derived from macadamia nut shells were found to adsorb and desorb between 80% (benzene) and 277% (ethylbenzene) more acetone (C 3), benzene (C 6), toluene (C 7), ethyl- (C 8), n-propyl- (C 9), or sec.-butylbenzenes (C 10) purged from water at the 100 ppb level than the commercial adsorbents tested.

Gas chromatography study of retention of organic compounds on silica with an attached layer of hydrophobic groups

Silica adsorbents with bonded C 16H 33, n-C 6F 13(CH 2) 3, tert.-C 6F 13(CH 2) 3 or n-C 3F 7(CH 2) 3 groups were prepared by the reaction between hydroxylated silica (Silochrome) and corresponding N-(organodimethylsilyl)morpholines. These adsorbents, as well as silica with bonded phenylpolysiloxane which was prepared by multilayer attachment of phenyltrichlorosilane, were investigated by means of gas chromatography at zero surface coverage. Thermodynamic functions (Gibbs energies, entropies and heats of adsorption) were shown to change significantly with chemical nature and structure of attached groups. On the basis of the investigation of the adsorption of cyclic compounds we proposed that the mechanism of interaction between non-polar organic compounds and silanized silicas is absorption to the bonded layer. Dispersive and specific components of intermolecular interaction in adsorption have been estimated by several techniques.

Application of the simplified toxicity identification evaluation procedures to a chemical works effluent

Toxicity of a Chemical Works effluent from the Southeast China to the Daphnia magna was compared to determine the most representative aqueous fraction for simplified toxicity identification evaluation (TIE) studies. Toxicity characterization procedures revealed that the primary toxicant(s) was a nonpolar organic compound. Toxicity was recovered through C 18 solid-Phase extraction and concentration steps. Gas chromatography-mass spectroscopy of these concentrates revealed the presence of chlorobenzene, nitrobenzene, naphthalene, 1-chloro-3-nitrobenzene, 1-chloro-4-nitrobenzene, 2-naphthol and aniline. The mass balance approach of TIE implicated the seven chemicals as the primary toxicants. The simplified TIE procedures can save our cost and time. The significance of the TIE results may indicate a more widespread problem what chemical(s) has priority to be controlled when being discharged.

Competitive adsorption of sulfolane and thiolane on clay materials

Groundwater samples directly beneath a waste disposal site have been shown to contain a higher concentration of sulfolane and a relatively low concentration of thiolane. The sulfolane is a source compound of thiolane, a reduced form of sulfolane. In subsequent analyses of groundwater samples, these compounds have been detected from all of the monitoring wells in the study area. Since these compounds are present together in an aquifer, a possible competition, that can happen in such a system, has been investigated. Thiolane is a nonpolar heterocyclic organic compound whereas sulfolane is a weakly acidic dipolar solvent. As expected, thiolane adsorbs more strongly onto clay than sulfolane in a single solute system. For regression of bisolute system using Matlab to obtain Q (maximum number of moles of solute adsorbed per unit weight of adsorbent), k1 (constants related to the energy of adsorption for sulfolane), and k2 (constants related to the energy of adsorption for thiolane), the k1 value (sulfolane) is smaller than the k2 value (thiolane) which reflects that thiolane is more strongly adsorbed than sulfolane. This is strongly consistent with the result obtained from single solute system. The Q for the sulfolane and combined data is the same that indicates that the sulfolane data is dominantly fitted because the concentrations of sulfolane are much greater than those of thiolane in the experiments. In combined data regression, the suppression of sulfolane adsorption on clay was also observed by the presence of thiolane.

The solubility of toluene in aqueous salt solutions

The solubility of toluene has been measured in distilled water, and in various inorganic salt solutions. Values of the Setschenow constant, KS, which quantify toluene solubility versus salt concentration, have been determined for each salt. Values of KS are compared to the activity of water for the salt solutions. Data from this study, consistent with earlier data, suggests that the effects of salts upon toluene solubility are non-additive. This contrasts the additive behavior of inorganic salts upon the solubility of nonpolar organic compounds, such as benzene and naphthalene, reported in the literature. Specific interaction between slightly polar toluene and ions in solution is suggested as a possible explanation for the non-additive effect of salts on the solubility of toluene.

A Case Study on Identifying the Toxicant in Effluent Discharged from a Chemical Plant

Three phase procedures of toxicity identification evaluation (TIE) were conducted using Daphnia magna to identify the toxicant in effluent discharged from a chemical plant in Nanjing. Phase I toxicity characterization procedures suggested nonpolar organic compounds were responsible for the whole effluent toxicity. In phase II toxicity identification procedures, the effluent toxicity was recovered by C 18 solid-phase extraction and concentration steps. Gas chromatography–mass spectrometry (GC/MS) of the concentrate indicated that benzopyrone and phenol were present in the effluent at sufficient concentrations to cause the effluent toxicity. In phase III toxicity confirmation procedures, benzopyrone and phenol mixture tests and mass balance determinations with toxic units (TU) confirmed these compounds were the key toxicants accounting for 44.6% and 32.9% of the whole effluent toxicity, respectively.

32-Week Holding-Time Study of SUMMA Polished Canisters and Triple Sorbent Traps Used To Sample Organic Constituents in Radioactive Waste Tank Vapor Headspace

Two sampling methods [SUMMA polished canisters and triple sorbent traps (TSTs)] were compared for long-term storage of trace organic vapor samples collected from the headspaces of high-level radioactive waste tanks at the U.S. Department of Energy's Hanford Site in Washington State. The two methods were found to provide generally equivalent results. Because safety, quality assurance, radiological controls, and somewhat complex sample custody arrangements frequently precluded rapid analysis, the long-term stability of the sampling media during storage needed to be addressed. Samples were analyzed with a gas chromatograph/mass spectrometer (GC/MS) using cryogenic preconcentration or thermal desorption sample introduction techniques. SUMMA canister samples were also analyzed for total non-methane organic compounds (TNMOC) by GC/flame ionization detector (FID) using EPA Compendium Method TO-12 . The 31 target organic analytes studied represented compounds with widely varying polarities and volatilities. To verify the long-term stability of the sampling media, multiple samples were collected in parallel from a typical passively ventilated radioactive waste tank known to contain moderately high concentrations of both polar and nonpolar organic compounds. Two sets of sorbent trap samples were collected to compare the effects of storage under refrigerated (−20 °C) and room temperature conditions. Analyses for organic analytes and TNMOC were conducted at increasing intervals over a 32-week period to determine whether any systematic degradation of sample integrity occurred. Analytes collected in the SUMMA polished canisters generally showed good stability over the full 32 weeks with recoveries at the 80% level or better for all compounds studied. The TST data showed some loss (50−80% recovery) for a few high-volatility compounds even in the refrigerated samples; losses for unrefrigerated samples were far more pronounced with recoveries as low as 20% observed in a few cases. Long-term stability for the other compounds studied was deemed to be generally satisfactory at the 80% recovery level.

Sorption of Perchloroethylene by Surfactant-Modified Zeolite as Controlled by Surfactant Loading

The sorption of nonpolar hydrophobic organic compounds by soil organic matter has long been attributed to a partitioning mechanism, with the sorption coefficient proportional to the fractional organic carbon content of the soil. However, deviations from this linear proportionality have been observed and reported in the literature by many authors. In our study a natural zeolite was modified with a cationic surfactant to achieve different fractional organic carbon contents and different surfactant molecule configurations on the surface. The sorption of perchloroethylene (PCE) by the surfactant-modified zeolite (SMZ) was found to be dependent on the bound surfactant molecule configuration as well as on the fractional organic carbon content. Below monolayer coverage by the surfactant, the PCE sorption coefficient on SMZ was proportional to the fractional organic carbon content. Above monolayer coverage, increasing fractional organic carbon content resulted in minimal further increase in the PCE sorption coefficient. The change in PCE sorption behavior was attributed to the structural differences between sorbed surfactant monolayers and bilayers. The surfactant surface configuration has a significant impact on the effective volume and density of the bound organic phase that is responsible for partitioning nonpolar organic compounds. The ratio of the organic carbon-based distribution coefficient (Koc) for the monolayer versus that for the bilayer systems was 1.7, similar to the estimated bilayer to monolayer hydrocarbon density of 1.3. Our results reinforce the notion that the structure of natural organic matter as well as its quantity controls the sorption of nonpolar organics to soils and sediments.

Organic Compound Sorption Enthalpy and Sorption Mechanisms in Soil Organic Matter

AbstractSmall exothermic or even endothermic heats of sorption for organic compounds in soil organic matter (SOM) have been traditionally considered evidence for a partitioning mechanism into the bulk of SOM. This derives from considerations of solute transfer enthalpy (ΔHtr) from aqueous solution to organic solvent and partial molar enthalpies of solution in organic solvent (ΔHssol) and aqueous (−ΔHwsol) phases, where ΔHtr = ΔHssol − ΔHwsol. The dissolution of many solutes in organic solvents is accompanied by positive solution enthalpies and conforms to the condition ΔHtr > −ΔHwsol. It was suggested by analogy of SOM to organic solvents, that solute sorption enthalpies (ΔHi) in SOM that conform to the analogous condition (i.e., ΔHi > ΔHwsol) are consistent with partitioning into SOM. Systems that do not conform to this condition (i.e., ΔHi < ΔHwsol) were considered to be consistent with adsorption. The purpose of this analysis is to point out the fallacies associated with this reasoning and to demonstrate that sorption enthalpy cannot be used in this way as evidence for a particular sorption mechanism. It is shown that for partitioning of numerous organic solutes into different organic solvents, ΔHssol < 0, such that ΔHtr < −ΔHwsol. If SOM is considered the solvent phase, it is clear that ΔHi < −ΔHwsol cannot be taken to indicate surface adsorption. This is particularly true for systems that provide an opportunity for strong force specific interactions inside of SOM. Similarly, it is shown that systems involving adsorption of nonpolar organic compounds at mineral surfaces often conform to the condition suggested as evidence for partitioning.

Deviations from Sorption Linearity on Soils of Polar and Nonpolar Organic Compounds at Low Relative Concentrations

A series of single-solute and binary-solute sorption data have been obtained on representative samples of polar compounds (substituted ureas and phenolic compounds) and of nonpolar compounds (e.g., EDB and TCE) on a peat soil and a mineral (Woodburn) soil; the data extend to low relative solute concentrations (Ce/Sw). At relatively low Ce/Sw, both the nonpolar and the polar solutes exhibit nonlinear sorption. The sorption nonlinearity approaches apparent saturation at about Ce/Sw = 0.010−0.015 for the nonpolar solutes and at about Ce/Sw = 0.10−0.13 for the polar solutes; above these Ce/Sw regions, the isotherms are practically linear. The nonlinear sorption capacities are greater for polar solutes than for nonpolar solutes and the peat soil shows a greater effect than the Woodburn soil. The small nonlinear sorption capacity for a nonpolar solute is suppressed indiscriminately by either a nonpolar or a polar cosolute at relatively low Ce/Sw of the cosolute. By contrast, the abilities of different cosolutes to suppress the nonlinear capacity of a nominal polar solute differ drastically. For polar solutes, a nonpolar cosolute exhibits a limited suppression even at high cosolute Ce/Sw; effective suppression occurs when the cosolute is relatively polar and at various Ce/Sw. These differences suggest that more than a single mechanism is required to account for the nonlinear sorption of both nonpolar and polar compounds at low Ce/Sw. Mechanistic processes consistent with these observations and with soil surface areas are discussed along with other suggested models. Some important consequences of the nonlinear competitive sorption to the behavior of contaminants in natural systems are discussed.

Sequestration of Hydrophobic Organic Contaminants by Geosorbents

The chemical interactions of hydrophobic organic contaminants (HOCs) with soils and sediments (geosorbents) may result in strong binding and slow subsequent release rates that significantly affect remediation rates and endpoints. The underlying physical and chemical phenomena potentially responsible for this apparent sequestration of HOCs by geosorbents are not well understood. This challenges our concepts for assessing exposure and toxicity and for setting environmental quality criteria. Currently there are no direct observational data revealing the molecular-scale locations in which nonpolar organic compounds accumulate when associated with natural soils or sediments. Hence macroscopic observations are used to make inferences about sorption mechanisms and the chemical factors affecting the sequestration of HOCs by geosorbents. Recent observations suggest that HOC interactions with geosorbents comprise different inorganic and organic surfaces and matrices, and distinctions may be drawn along these lines,...

Paramagnetic Relaxation of Atrazine Solubilized by Humic Micellar Solutions

This study examines a central tenet of the “membrane−micelle” model of humic substancesthat humic molecules form “micelle-like” aggregates with hydrophobic interiors into which nonpolar organic compounds partition. We solubilized atrazine, labeled by a trifluoromethyl group on the ethylamino side chain, in aqueous solutions containing 10% humic acid by weight and observed the F-19 nuclear magnetic resonance (NMR) relaxation of atrazine induced by paramagnetic probes added to the humic solution. One paramagnetic probe, Gd·EDTA anion, remains in aqueous solution while the other, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), is sorbed by humic micelles. The hydrophilic anionic paramagnetic probe induces virtually no paramagnetic relaxation in atrazine solubilized by 10% aqueous humic acid solutions while the hydrophobic neutral paramagnetic probe causes rapid paramagnetic relaxation. These results show that atrazine solubilized by concentrated humic acid solutions occupies a domain accessible only to neutral...

Extraction of polychlorinated biphenyls with water under subcritical conditions

Supercritical fluid extraction is a fast and efficient method to extract all manner of organic compounds from a wide variety of solid sample matrices. Due to the marked change in its polarity with temperature, water is an interesting alternative to carbon dioxide as the extraction fluid. By merely adjusting the temperature, selectivity can be achieved for inorganic or organic compounds and for polar or non-polar organic compounds. Many organic compounds are sufficiently soluble to be extracted under subcritical conditions and, in this way, instrumental and other problems, such as the high corrosiveness of supercritical water, can be avoided. Instrumentation for sub- and supercritical water extraction was developed and modified in several ways with the aim of simplifying the procedure while maintaingng good recoveries. Good recoveries of polychlorinated biphenyls (PCBs) spiked into sea sand and of native PCBs in a real soil sample were achieved with liquid collection. Relative to Soxhlet extraction, recoveries were higher or similar when solid-phase and liquid collection were combined. With a solid-phase trap packed with Tenax, the recovery was usually more than 85% for spiked PCBs.