Chlorinated Hydrocarbon Solvents Research Articles

The impact of additives found in industrial formulations of TCE on the wettability of sandstone

The wettability of aquifer rocks is a key physical parameter which exerts an important control on the transport, residual trapping, distribution and eventual fate of chlorinated hydrocarbon solvents (CHSs) released into the subsurface. Typically chlorinated solvents are assumed to be non-wetting in water saturated rocks and unconsolidated sediments. However industrially formulated solvent products are often combined with basic additives such as alkylamines to improve their performance; and the mineral surfaces of aquifer rocks and sediments usually possess a range of acid and hydrogen-bonding adsorption sites. The presence of these sites provides a mechanism whereby the basic additives in CHSs can be adsorbed at the solvent phase/solid phase interface. Given the amphiphilic molecular structure of these additives, this may result in changes in the wetting conditions of the solid phase. The aim of this study was therefore to test this conjecture for two classes of additives (alkylamines and quaternary ammonium salts) that are often encountered in industrial solvent formulations. Wettability assessments were made on sandstone cores by means of measurements of spontaneous and forced water drainage and spontaneous and forced water imbibition and through contact angle measurements on a smooth quartz surface. No solvent/additive combination produced solvent wetting conditions, though dodecylamine and octadecylamine significantly reduced the water wetting preference of sandstone which frequently resulted in neutral wetting conditions. The large volume of spontaneous water drainage observed in wettability experiments involving cetyltrimethylammonium bromide and octadecyltrimethylammonium bromide, suggested that the sandstone cores in these tests remained strongly water wetting. However equilibrium static contact angles of around 60° were measured on quartz suggesting that the sandstone surfaces should be close to neutral wetting conditions. This paradox was finally resolved by noting that contact between the solvent mixture and water in the sandstone core resulted in a final solvent phase which had an extremely low interfacial tension. It is therefore suspected that the observed spontaneous drainage of solvent from the core was driven by gravitational and buoyancy forces rather than strong water wetting conditions. Finally it was noted that the mobilisation of iron oxide coatings from the sandstone surface had a considerable influence in reducing the interfacial tension and in the formation and stabilisation of TCE/water emulsions.

Recognition and exposition of intermolecular interaction between CH 2Cl 2 and CHCl 3 by conducting polyaniline materials

A detailed study has been performed on the sensing of weakly interacting chlorinated hydrocarbon solvent vapours of CH 2Cl 2 and CHCl 3 separately or combinedly from their solvent mixture (1:1 by volume) by three polyaniline materials, polyaniline sulphate (PANI), PANI doped with naphthalenesulphonic acid (PANI-NSA) and PANI-poly(vinyl alcohol) blend (PANI-PVA) of 2:1 molar ratio. Each sensor material responded through a decrease in conductivity reversibly and their activities were monitored by normalized conductivity change (NCC). The NCC values for the two solvents are in the decreasing order, PANI-NSA > PANI > PANI-PVA which is also the order of conductivity. However, the NCC values of the vapour mixture are abnormally far higher than the sum of NCC values of individual solvent vapours in all the three materials. Originally CH 2Cl 2 has a weaker interaction than CHCl 3 with polyaniline materials. Nevertheless, it gets ‘activated’ in the molecular pair with CHCl 3 through electronic effects and the pair exhibits concerted interaction with polyaniline materials causing abnormal conductivity changes. Conductivity studies performed in different solvent sequence vapour exposures, spectral (IR, UV–vis and EPR) and structural (XRD) studies have not only confirmed this concerted type of interaction but also demonstrated the dominance of CH 2Cl 2 vapour in molecular pair interaction with polyaniline. In the two solvent cases, the vaporized molecules neutralize the polarons by acting as reducers and bring about a decline in conductivity. On the contrary, with mixture, besides this redox activity, the accompanying conformational change in the sensor material also appears to be responsible for the abnormal conductivity change. Polyaniline could, thus, recognize and expose the intermolecular interaction in the molecular pair of CH 2Cl 2 and CHCl 3 like proteins through its chemically flexible unique characteristics of imine-amine groups and protonation-dependent conductivity.

A Strong Acid that Does Not Protonate Water

The nature of solvated acids in benzene and chlorinated hydrocarbon solvents is sensitively revealed by IR spectroscopy. Two similarly strong, structurally related acids, triflic acid (CF3SO3H) and the N−H acid bis(trifluoromethylsulfonyl) imide ((CF3SO2)2NH), behave quite differently toward water in these media. Triflic acid protonates water at the one-equivalent level to give the hydronium ion, H3O+. By contrast, bis(trifluoromethylsulfonyl) imide forms a simple hydrate, (CF3SO2)2NH···OH2, even with water at the two-equivalent level. The difference arises from the differing abilities of the conjugate base anions to engage in H-bonding and ion pairing. It illustrates how acidity in low-dielectric media is critically dependent on the nature of the conjugate base anion. νO−H and νN−H stretching frequencies indicate that the H-bonding acceptor ability for solvents toward acidic protons increases in the order carbon tetrachloride < benzene ∼ 1,2-dichoroethane < water. With benzene, a marked tendency for acidic protons to H-bond to the π-face of the arene ring is noted and an IR signature of this solvation mode is observed.

Chlorinated hydrocarbon solvents.

Chlorinated hydrocarbon solvents, such as trichloroethylene and 1,1,1-trichloroethane, have been used widely in many industries because of their ready ability to dissolve oils, greases, and other materials, their low acute toxicity, and their non-flammability. Although these materials share certain toxicologic, functional, and chemical similarities, important differences exist. These differences largely explain why certain solvents, once common, are no longer in use and why others have become more widely used over time. This article reviews the properties, toxicologic effects of interest, workplace limits, and use history of the most common chlorinated hydrocarbon solvents.

Changes in interfacial tension of chlorinated solvents following flow through U.K. soils and shallow aquifer material.

The interfacial tension (IFT) that arises at the interface between water and an immiscible organic liquid is a key parameter affecting the transport and subsequent fate of the organic liquid in water-saturated porous media. In this paper, data are presented that show how contact between a range of soil types and chlorinated hydrocarbon solvent (CHS) dense nonaqueous phase liquids (DNAPLs) can affect DNAPL/water IFT values. The soils examined are indicative of U.K. soil types and shallow aquifer materials. The solvents investigated were tetrachloroethylene (PCE) and trichloroethylene (TCE). Lab grade, recovered field DNAPL and industrial waste chlorinated solvent mixtures were used. The data from batch and column experiments invariably revealed that water/DNAPL IFT values change following contact with unsaturated soils. In the majority of cases, the IFT values increase following soil exposure. However, after contact with an organic-rich soil, the IFT of the lab grade solvents decreased. The experimental evidence suggests that these reductions are linked to the removal of organic material from the soil and its subsequent incorporation into the solvent IFT increases in the case of lab solvents are shown to be linked to the removal of stabilizers (added by the manufacturers to obviate degradation) that are removed by adsorption to soil mineral surfaces. Similarly, it is conjectured that adsorption of surface-active compounds from the industrial waste samples to soil surfaces is responsible for increases in the IFT in these samples. Finally, it was observed that invading CHSs are capable of dissolving and subsequently mobilizing in-situ soil contaminants. GC/MS analysis revealed these mobilized soil contaminants to be polyaromatic hydrocarbons and phthalate esters.

Scleroderma and solvent exposure among women.

Exposure to solvents has been reported to increase the risk of scleroderma. The authors investigated the relation between exposures to solvents in occupational and hobby settings and the development of scleroderma among women in a case-control study with population-based controls in Michigan (1980-1991) and Ohio (1980-1992). A total of 660 cases and 2,227 frequency-matched controls were interviewed by telephone. Diagnoses of scleroderma were verified by medical records review. Paint thinners and removers were significantly associated with scleroderma both by self-report (odds ratio (OR) = 1.9, 95% confidence interval (CI): 1.4, 2.6) and after expert review (OR = 2.0, 95% CI: 1.5, 2.6). Other petroleum distillates (gasoline and mineral spirits) were not significantly associated with scleroderma after controlling for other correlated exposures in multivariable analyses. Trichloroethylene was associated with scleroderma both by self-report (OR = 2.0, 95% CI: 0.8, 4.8) and after expert review (OR = 1.9, 95% CI: 0.6, 6.6), but not significantly. Analyses by duration of exposure found that risk increased with the duration of use of any of the solvents (OR = 1.01/year of exposure, 95% CI: 1.01, 1.02), but there was no evidence of increasing risk with increasing duration of exposure for any specific solvent studied. In summary, exposures to paint thinners and removers were associated with scleroderma in women but showed no evidence of increasing risk with increasing duration. Exposures to other specific chlorinated and nonchlorinated hydrocarbon solvents were not clearly associated with scleroderma.

Photoionization of β-carotene via electron transfer from excited states to chlorinated hydrocarbon solvents. A picosecond transient absorption study

Time-resolved photoinduced (λexc 266, 355 and 532 nm) formation of the radical cation of β-carotene in the chlorinated solvents n-butylchloride, dichloromethane, 1,2-dichloroethane, chloroform and carbon tetrachloride, was studied with 5–10 ps time resolution. The radical cation is formed via electron transfer from the electronically excited solute to the solvent and is characterized by an absorption band with maximum at 900–950 nm. The process is efficient (ϕ > 0.12) and fast (t < 10 ps), which excludes involvement of the triplet state. It is suggested that the electron transfer proceeds from either the vibrationally excited singlet 2A−g (l 2) or from the “forbidden” 1B−u state. The formation times of the carotene radical cation in the chlorinated hydrocarbon solvents are on the order of their diffusion times.

A Comparison of the Activity of Polymer Immobilised TEMPO (PIPO) with MCM-41 and Silica Supported TEMPO as Heterogeneous Catalysts for the Oxidation of Alcohols

PIPO, a readily prepared polymer immobilised TEMPO, is an efficient recyclable heterogeneous catalyst for the chlorinated hydrocarbon solvent- and bromide-free bleach oxidation of a variety of alcohols. Under these environmentally friendly conditions, PIPO is superior to homogeneous TEMPO and the previously described MCM-41 and silica supported TEMPO catalysts. In addition, in combination with CuCl, PIPO is also able to catalyse the aerobic oxidation of benzyl alcohol.

Clean-chemistry synthesis of 2-tetralones in a single-stage acylation-cycloalkylation process.

The preparation of substituted-2-tetralones by direct reaction of a 1-alkene with a substituted phenylacetic acid in a reaction system of trifluoroacetic anhydride (TFAA) and phosphoric acid is described. This single-stage process involves in situ formation of a mixed anhydride of the phenylacetic acid and acylation of the alkene by this species followed by cycloalkylation of the aromatic ring. This is a cleaner approach to the synthesis of 2-tetralones compared to Friedel-Crafts aliphatic acylation-cycloalkylation in that use of thionyl chloride, aluminum trichloride, and a chlorinated hydrocarbon solvent is eliminated. In addition, the atom efficiency is augmented by recovery of the spent TFAA as trifluoroacetic acid (TFA) and conversion of this back to TFAA by dehydration.

A comparison of prototype compound parabolic collector-reactors (CPC) on the road to SOLARDETOX technology

Solar photocatalytic detoxification of non-biodegradable chlorinated hydrocarbon solvents (NBCS) is carried out in different concentrating and non concentrating devices using TiO2 as a photocatalyst fixed on the inner surface of the reaction tubes or as a slurry catalyst which has to be removed from the treated water. The reaction is most effective using 200 mg/l of TiO2 as a slurry in a non concentrating CPC reactor. The concentrating parabolic trough reactor has a poor activity because of its minor irradiated reactor surface. Catalyst coated glass tubes are less efficient then the used slurry catalyst. Their advantage is that no catalyst has not to be removed from the treated water and there is no loss of activity during treatment. Yet their physical stability is not sufficient to be competitive to the slurry catalyst. Nevertheless the degradation results are very promising and will possibly lead to commercial applications of this technology.

Occupational exposures and cancers of the endometrium and cervix uteri in Finland.

Endometrial cancer incidence rates are low in Asia and Africa and high in North America and Northern Europe. Cervical cancer is often the most common female cancer in developing countries, and infection with human papillomavirus (HPV) is its main risk factor. However, other factors, such as occupational exposures may modify the HPV-related risk. We conducted an exploratory register-linkage study in Finland to assess the role of occupational exposures on incidence rates of cancers of the endometrium and cervix uteri. Occupational risk factors for endometrial and cervical cancers were explored in a 25-year follow-up of female workers born 1906-1945 (N = 413,877) identified through the Population Census of Finland of 1970. Job titles in census records were converted to exposures of 31 occupational agents through a job-exposure matrix. Poisson regression models estimated relative risks (RR) for each agent, standardized for birth cohort, follow-up period, and socio-economic status. For each agent, the product of level and probability of exposure was calculated and subdivided in three categories: zero, low, and medium/high. Adjustment at the job title level was done for the turnover rate (endometrial and cervical cancers), mean parity, and age at first birth (endometrial cancer). Endometrial cancer (2,833 cases) was associated with exposure to animal dust (RR 1.2, low level, 174 cases) and sedentary work (RR 1.3, high level, 145 cases). Cervical cancer (1,101 cases) was associated with exposure to aliphatic and alicyclic (RR 1.3, low level, 91 cases), aromatic (RR 1.2, low level, 318 cases; RR 1.4, high level, 41 cases), and chlorinated hydrocarbon solvents (RR 1.3, low level, 50 cases), silica dust (RR 1.2, low level, 251 cases), and wood dust (RR 1.2, low level, 249 cases). This study suggests that occupational exposures may be associated with increased risk of endometrial and cervical cancers.

Design of multiple flame‐retardant polymers

AbstractTwo polyphosphonates having multiple flame‐retardant actions were synthesized by interfacial polycondensation of a bisphenol and dichlorophenylphosphine oxide using cetyl trimethyl ammonium chloride as a phase transfer catalyst (PTC) at 0°C. The polyphosphanates thus prepared were characterized by viscometry, elemental analysis, IR, 1H‐NMR, 31P‐NMR, and X‐ray diffraction studies. These polymers are highly soluble in polar solvents such as DMF, DMAc, DMSO, etc., as well as in chlorinated hydrocarbon solvents such as CH2Cl2, CHCl3, etc. The thermal study of polymers was carried out by TGA and DTA analyses. The flammability of the polymers was studied by the limiting oxygen index measurements. The polymers are self‐extinguishing, and begin to lose weight at around 252°C. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 81: 785–792, 2001

Risk of pancreatic cancer in workers exposed to chlorinated hydrocarbon solvents and related compounds: a meta-analysis.

This is a meta-analysis of occupational exposures to chlorinated hydrocarbon (CHC) solvents and pancreatic cancer, based primarily on studies that addressed exposure directly (agent studies) and secondarily on studies that reported data without verification of individual CHC exposures (job title studies), all of which were listed in databases for the period January 1969 to May 1998. Standardized extraction of data and double-checking of consistency of data extraction by five extractors were done. Simple random models estimated meta-relative risks. Suggestive weak excesses were found for trichloroethylene (meta-relative risk (MRR) = 1.24, 95% confidence interval (CI): 0.79, 1.97), polychlorinated biphenyls (MRR = 1.37, 95% CI: 0.56, 3.31), methylene chloride (MRR = 1.42, 95% CI: 0.80, 2.53), and vinyl chloride (MRR = 1.17, 95% CI: 0.71, 1.91) but not for carbon tetrachloride. One study addressed tetrachloroethylene (MRR = 3.08, 95% CI: 0.63, 8.99); another investigated chlorohydrin production (MRR = 4.92, 95% CI: 1.58, 11.4). Exposure-response meta-analyses for trichloroethylene and methylene chloride failed to reveal trends. Job title studies on metal degreasing and dry cleaning revealed significant MRRs (2.0 and 1.4, respectively). Publication bias was unlikely. Confounding may have remained insufficiently controlled. Unless the results are seriously biased by exposure or endpoint misclassification or by confounding, strong causal associations between CHC compounds and pancreatic cancer can be judged unlikely. Interactions between environmental and occupational agents, lifestyle factors, and genetic susceptibility remain a possibility, but the data for this meta-analysis did not address interactions.

Synthesis and Properties of NewN-Methylated Aliphatic-Aromatic Polyamides Derived from N,N′-Dimethylalkylenediamines and 4,4′-Biphenyl-dicarboxylic and 4,4″-p-Terphenyldicarboxylic Acids

Two new series of N-methylated aliphatic-aromatic polyamides were prepared by interfacial polycondensation of N,N'-dimethylalkylenediamines having 6-10 methylene units with 4,4'-biohenyldicarbonyl and 4,4-p-terphenyldicarbonyl chlorides. All of the N-methylated polyamides were soluble in chlorinated hydrocarbon solvents, and the solubilities of the biphenyl-based polyamides were higher than those of the terphenyl-containing polymers. The biphenyl-bearing polyamides with an even-number of methylene units were crystalline and their odd-numbered neighbors were amorphous, whereas all of the terphenyl-containing polymers were crystalline. The melting temperatures of the terphenyl-based polyamides (220-307°C) were higher than those of the biphenyl-bearing polymers (180-207°C). Among these N-methylated polyamides, the terphenyl-containing polyamide having 7 methylene units showed enantiotropic liquid crystallinity.

Study on intermediate species of polystyrene by using pulse radiolysis

The solvent effects on the formation and reaction processes of intermediates in irradiated polystyrene (PS) in chlorinated hydrocarbon solutions have been studied by using pulse radiolysis. Both the intramolecular dimer cation radical (Ph 2 +·) and CT complex are confirmed clearly in pulse radiolysis of polystyrene solutions in CH 2Cl 2. The infrared absorption bands are observed in nanosecond pulse radiolysis of polystyrene solutions in three chlorinated hydrocarbons. The peaks, band width, and intensity of infrared absorption depend on kinds of chlorinated hydrocarbon solvents. The absorption intensities of Ph 2 +· were increased with the increase in the polarity of solvents.

Steric Strain and Reactivity: Electrophilic Bromination oftrans-(1-Methyl-2-adamantylidene)-1-methyladamantane

trans-(1-Methyl-2-adamantylidene)-1-methyladamantane (DMAD, 1b) reacts with Br(2) in chlorinated hydrocarbon solvents to give either a bromonium polybromide ion pair or a substitution product, depending on bromine concentration. The first intermediate is a 1:1 pi-complex having K(f) = 1.85(0.19) x 10(3) M(-)(1) at 25 degrees C, which rapidly evolves to the bromonium tribromide ion pair. At high bromine concentration, which shifts all equilibria involving the counteranion of the ion pair intermediate toward the pentabromide species, this bromonium ion is stable and unable to further evolve into products. Temperature-dependent NMR spectra indicate chemical exchange of Br(+) between the sides of the plane containing the two carbons of the bromonium ion. At very low bromine concentration, no ionic intermediate is detected and the reaction rapidly yields a rearranged substitution product, identified as 10. Under these conditions the disappearance of the pi-complex follows a first-order rate law, and the observed rate constant increases with increasing olefin concentration, showing that product formation implies Br(-) as counteranion of the ionic intermediate, whose formation is a reversible process. A comparison of the results reported here for the bromination of 1b with those previously found for the parent olefin, adamantylideneadamantane (1a), shows that steric strain markedly affects the reactivity of the double bond.

EFFICIENT EXTRACTION OF PACLITAXEL AND RELATED TAXOIDS FROM LEAF TISSUE OF TAXUS USING A POTABLE SOLVENT SYSTEM

Leaves of Taxus x media and Taxus brevifolia were examined for their potential use as a source of paclitaxel and related taxoids. Various solvent systems were compared for their efficacy in the extraction of paclitaxel, as well as the extraction of contaminating residue. A method of extraction has been developed that enriches paclitaxel by over 500-fold using only potable solvents in combination with solid phase extraction, thus avoiding the use of chlorinated hydrocarbon solvent systems. This solvent system can be used on fresh leaf material, eliminating the need for drying material before extraction, and preventing degradation of the taxoids during the drying process. Using these methods, paclitaxel constituted 0.01 to 0.02% of the dry weight of the leaf tissue from Taxus x media, and 0.04% from dried leaves of Taxus brevifolia.

Removal of single component chlorinated hydrocarbon vapor by activated carbon of very high surface area

Abstract Experimental results are reported on the application of a new type of activated carbon having very high specific surface area, 3000 m2/g, formed in granular or supported on a honeycomb board, to the recovery of chlorinated hydrocarbon solvent vapors. The activated carbon showed an excellent adsorption capacity and the type of its adsorption was found to be volume-filling. Intraparticle diffusion was found to be the same as that for conventional activated carbons, i.e. the intraparticle diffusion proceeds mostly by surface migration.

Engineering a recombinant Deinococcus radiodurans for organopollutant degradation in radioactive mixed waste environments.

Thousands of waste sites around the world contain mixtures of toxic chlorinated solvents, hydrocarbon solvents, and radionuclides. Because of the inherent danger and expense of cleaning up such wastes by physicochemical methods, other methods are being pursued for cleanup of those sites. One alternative is to engineer radiation-resistant microbes that degrade or transform such wastes to less hazardous mixtures. We describe the construction and characterization of recombinant Deinococcus radiodurans, the most radiation-resistant organism known, expressing toluene dioxygenase (TDO). Cloning of the tod genes (which encode the multicomponent TDO) into the chromosome of this bacterium imparted to the strain the ability to oxidize toluene, chlorobenzene, 3,4-dichloro-1-butene, and indole. The recombinant strain was capable of growth and functional synthesis of TDO in the highly irradiating environment (60 Gy/h) of a 137Cs irradiator, where 5x10(8)cells/ml degraded 125 nmol/ml of chlorobenzene in 150 min. D. radiodurans strains were also tolerant to the solvent effects of toluene and trichloroethylene at levels exceeding those of many radioactive waste sites. These data support the prospective use of engineered D. radiodurans for bioremediation of mixed wastes containing both radionuclides and organic solvents.

Synthesis and properties of new solubleN-phenyl-substituted aromatic-aliphatic and all aromatic polyamides derived from 4,4?-dianilinobiphenyl

New N-phenylated aromatic-aliphatic and all aromatic polyamides were prepared by the high-temperature solution polycondensation of 4,4′-dianilinobiphenyl with both aliphatic (methylene chain lengths of 6–11) and aromatic dicarboxylic acid chlorides. All of the aromatic-aliphatic polyamides and the wholly aromatic polyamides exhibited an amorphous nature and good solubility in amide-type and chlorinated hydrocarbon solvents, except for those aromatic polyamides containing p-oriented phenylene or biphenylylene linkages in the backbone; the latter were crystalline and insoluble in organic solvents except m-cresol. The N-phenylated aromatic-aliphatic polyamides and aromatic polyamides had glass transition temperatures in the range of 79–116°C and 207–255°C, respectively, and all the polymers were thermally stable with decomposition temperatures above 400°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2193–2200, 1998