Abstract  The current study evaluated the Control of Substances Hazardous to Health (COSHH) Essentials model for short-term task-based exposures and full-shift exposures using measured concentrations of three volatile organic chemicals at a small printing plant. A total of 188 exposure measurements of isopropanol and 187 measurements of acetone were collected and each measurement took approximately 60 min. Historically, collected time-weighted average concentrations (seven results) were evaluated for methylene chloride. The COSHH Essentials model recommended general ventilation control for both isopropanol and acetone. There was good agreement between the task-based exposure measurements and the COSHH Essentials predicted exposure range (PER) for cleaning and print preparation with isopropanol and for cleaning with acetone. For the other tasks and for full-shift exposures, agreement between the exposure measurements and the PER was either moderate or poor. However, for both isopropanol and acetone, our findings suggested that the COSHH Essentials model worked reasonably well because the probabilities of short-term exposure measurements exceeding short-term occupational exposure limits (OELs) or full-shift exposures exceeding the corresponding full-shift OELs were <0.05 under the recommended control strategy. For methylene chloride, the COSHH Essentials recommended containment control but a follow-up study was not able to be performed because it had already been replaced with a less hazardous substance (acetone). This was considered a more acceptable alternative to increasing the level of control.

Abstract  Acyclovir, a selective antiherpes virus agent, was loaded in the hollow microspheres to improve bioavailability and patient compliance by prolonging the residence time in the gastrointestinal tract. The hollow microspheres of acyclovir were prepared by solvent evaporation diffusion method using Eudragit S 100 as a controlled polymer. We found that the process conditions that provided the high % yield of the hollow microspheres were the use of 5:8:2 of dichloromethane: ethanol: isopropanol as a solvent system and stirring at 300 rpm for 60 min. The size of the microspheres prepared from different ratios of acyclovir and Eudragit S 100 was 159-218 microm. When the drug-to-polymer ratio was increased, the size and percent drug content increased. The highest percent drug entrapment was obtained at the ratio of 600 mg acyclovir: 1 g Eudragit S 100. The hollow microspheres tended to float over 0.1 M hydrochloric acid containing 0.02% Tween 20 solution for 24 hr. The rate of acyclovir released from the microspheres was generally low in simulated gastric fluid without enzyme due to the low permeability of the polymer. However, in phosphate buffer pH 6.8, the drug release increased as the drug load increased due to the swelling property of the polymer. In simulated intestinal fluids without enzymes, the polymer completely dissolved resulting in instant release of the drug in this medium.

Abstract  Mesoporous titania materials have been synthesized by using urea as a template via sol-gel reactions of titaniumisopropoxide, followed by the removal of urea by extraction with water. The solid was dried, calcined at different temperatures and impregnated with trifluoromethanesulfonic acid. They were extracted by a mixture of dichloromethane and diethyl ether using a Soxhlet apparatus in order to remove the loosely adsorbed acid. The solids were characterized by FT-IR, XRD, DTA-TGA, and BET. The acidic characteristics of the catalysts were determined by potentiometric titration with n-butylamine and the test reaction of isopropanol dehydration. (c) 2006 Elsevier B.V. All rights reserved.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Successful bioremediation often is difficult to achieve because of complex interactions between contaminants, the soil environment, and decomposer organisms. The objective of this work was to study the extent and pattern of contaminant biodegradation during slurry-phase bioremediation of four industrially-contaminated soils (<3% contamination) to obtain further insight into the factors which may control biodegradation. Two soils (sand and silty clay) were contaminated with creosote compounds, and two soils (loam and clay loam) were contaminated with petroleum compounds. Two liter glass jars containing 300g soil and 300 ml nutrient solution (300g soil and 100 ml nutrient for sand), and 5% inoculum of previously bioremediated soil containing an active culture, were rotated at 3 rpm at 22? C in the dark for 10 weeks. Biodegradation was monitored by measuring reductions in total dichloromethane-extractable organics (TEO), selected polycyclic aromatic hydrocarbons (PAHs),

Abstract  An analytical method was developed to determine quantitatively 1-hydroxypyrene (OHP) in bovine urine samples. The procedure includes an enzymatic hydrolysis to cleave the conjugated metabolite, an enrichment step using solid phase extraction with a non-polar rinse step and elution with dichloromethane. A final clean-up on silicagel was performed before high-performance liquid chromatography (HPLC) analysis and fluorescence detection. Alternatively, HPLC and electrospray ionization in the negative ion mode applying selective ion monitoring acquisition revealed to be a highly sensitive detection method allowing the quantitation of low pg of OHP in the urine samples. The method was successfully applied to the determination of OHP in bovine urine samples from animals living in urban and rural areas. Urine concentrations of OHP were significantly higher (median 8.6 mug l(-1)) of bovines living close to a highway. (C) 2002 Published by Elsevier Science Ltd.

Abstract  7H-Benzo[c]fluorene (benzo[c]fluorene) is a major DNA adduct forming component of coal tar in lung of mice. The present study evaluated the types of PAH:DNA adducts formed from different neat coal tar samples and soils contaminated with coal tar. Mice were fed diets containing coal tar either neat or as a contaminant in an environmental soil sample for 14 days, and the types of chemical:DNA adducts formed in lung were evaluated using P-32-postlabeling and HPLC analysis. Three major DNA adducts derived respectively from benzo[b]fluoranthene (B[b]F), benzo[a]pyrene (B[a]P), and benzo[c]fluorene were detected in three of the four neat coal tar samples evaluated. In contrast, only a single major DNA adduct derived from benzo[c]fluorene was observed with the remaining tar sample. Ingestion of coal tar contaminated soil resulted in DNA adducts primarily derived from benzo[c]fluorene and B[b]F; a B[a]P derived DNA adduct was not detected. The DNA adducts derived from benzo[c]fluorene and B[b]F but not B[a]P were also observed with animals fed methylene chloride extracts of three of these soils but not the one designated A1000H soil. However, the extract of A1000H resulted in a B[a]P: DNA adduct being detected along with adducts formed from B[b]F and benzo[c]fluorene. The selective formation of the benzo[c]fluorene:DNA adduct with coal tar contaminated soils indicates that the in vivo systemic bioavailability and/ or metabolism of benzo[c]fluorene is relatively high when compared to other DNA adducting hydrocarbons within coal tar. Benzo[c]fluorene may play a critical role in the potential of contaminated soil to induce a toxicological response in animals.

Abstract  Biotransformation of carbon tetrachloride (CT) was examined with an anaerobic enrichment culture grown on dichloromethane as the sole organic carbon and energy source. The principal products from [C-14]-CT included chloroform (17%), carbon disulfide (21%), and CO2 (21%). When cyanocobalamin was added along with CT, the percentage converted to CO2 increased almost 3-fold (59%), while CS2 decreased somewhat (11%), and virtually none of the CT (<1%) was reduced to chloroform. Carbon monoxide was a major transformation product (12-27%) in autoclaved cultures and in live cultures that received high levels of CT (up to 52 mg/L). Adding cyanocobalamin also increased the rate of CT transformation in live cultures by at least 10-fold, but had a minor effect on the rate of CT use in autoclaved cultures. Accelerated rates of transformation by live cultures were sustained for as long as 200 days, with hydrogen serving as the electron donor. Cyanocobalamin, hydroxocobalamin, and methylcobalamin were equally effective, while a 3-week lag period was required before adenosylcobalamin started to enhance CT transformation. Because of their high cost, the feasibility of using cobalamins will depend on the amount required. We observed significant enhancement in CT transformation at concentrations up to 340 mu M, with cobalamin levels as low as 10 mu M.

Abstract  Preparation, metal ion complexation and coordinative assembly of polyiminocarbazolylenes with terpyridine substituent groups into organized electrochromic films are described. Polymers P-2,7 and P-3,6 were prepared upon Pd-catalyzed coupling of 2,7-dibromo-N-(2-ethylhexyl)carbazole or 3,6-dibromo-N-(2-ethylhexyl)carbazole and 4'-(4-aminophenyl)-2,2':6,2 ''-terpyridine. Molecular weights of about 3 000 Da were obtained indicating the formation of oligomers. The compounds are soluble in common organic solvents. P-3,6 exhibits blue, green or yellow fluorescence in toluene, tetrahydrofuran (THF), or dichloromethane, respectively, whereas P-2,7 exhibits a blue fluorescence independent from the polarity of the solvent. Fluorescence quantum yields up to 68% were found. Upon addition of divalent metal salts such as zinc, nickel or cobalt acetate, colour transitions involving isosbestic points occur. Titration experiments indicate the formation of 2 : 1 and 1 : 1 tpy : metal ion complexes. Organized films of the polymer-metal ion complexes can be prepared, if pretreated negatively charged substrates (quartz, ITO-coated glass) are sequentially dipped into a THF/DMF/n-hexane (1 : 0.1 : 1, v/v) solution of the metal hexafluorophosphates and the THF/n-hexane (1 : 1, v/v) solutions of the polymers. Films of the zinc and nickel ion complexes of P-3,6 and P-2,7 are yellow in the neutral state, whereas films containing the cobalt complex are pink. Upon anodic oxidation, all films exhibit electrochromic properties. Films containing P-3,6 exhibit color changes into green and blue (zinc and nickel) or greenish brown (cobalt). For films containing P-2,7 the oxidation potentials are generally higher. Upon oxidation, color changes into grey (zinc), olive (nickel), or brown (cobalt) are found. All color changes are reversible, even under ambient conditions. Switching times of the films prepared upon twelve dipping cycles are between 300 ms and 1.1 s, the change of transmittance being low (2.8 to 4%) at 800 nm, but rather high at 300 nm (up to 24.6%). The self-assembled films are useful for preparation of electrochromic devices.

Abstract  In this study, films of poly[1-(4-methoxyphenyl)-1H-pyrrole] [poly(MPPy)] were electrochemically grown on carbon fiber microelectrodes (CFMEs) in 0.05 M of tetraethyl ammonium perchlorate-dichloromethane. The effect of different monomer concentrations (range = 1-10 mM) on electrochemical properties of resulting polymers was characterized by cyclic voltammetry, Fourier transform infrared reflectance-attenuated total reflection spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy. All modified CFMEs were found to have capacitance on the basis of Nyquist, Bode-magnitude, Bode-phase, and Admittance plots. An equivalent circuit model of (R(C(R(QR)))(CR)) gave the best fit for all monomer concentrations used. Furthermore, SEM and AFM results showed that poly(MPPy) was formed as a continuous and well-adhered film onto CFME. (C) 2009 Wiley Periodicals, Inc. Adv Polym Techn 28: 120-130, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20152

Abstract  A new polythiophene containing a cholesteryl side chain in the beta-position was chemically polymerised in nitromethane/carbontetrachloride using FeCl3 as the oxidizing agent. Polymerisation was also achieved by constant current electrolysis in dichloromethane. Subsequently, conducting copolymers of thiophene-3-yl acetic acid cholesteryl ester (CM), PCM1 (obtained from chemical polymerisation method) and PCM4 (obtained from constant current electrolysis) with pyrrole were synthesized using p-toluene sulfonic acid and sodium dodecyl sulfate as the supporting electrolytes via constant potential electrolyses. Characterizations of the samples were performed by CV, FTIR, NMR, DSC, TGA and SEM analyses. Electrical conductivities were measured by the four-probe technique. (C) 2002 Kluwer Academic Publishers.

Abstract  Catalytic total oxidation of some selected chlorinated hydrocarbons is studied with several Pt-based catalysts. Chlorinated hydrocarbons used have been ethyl chloride, trichloroethylene and dichloromethane, alone or mixed with some hydrocarbons, such as toluene. Eighteen different catalysts have been tested from eight different manufacturers (Degussa AG, Sud-Chemie AG, Kataleuna GmbH, Chimet, Johnson Matthey, Prototech Co.,...) and from three research institutions (Universities of Leiden (NL) and Wroclaw (PL) and Spanish CSIC-ICP). Catalysts both in the form of spheres (particulates) and of monoliths are used. Selection of the best catalyst(s) is made based on their activity, selectivity and life. Apparent energies of activation for these reactions on these catalysts, using an empirical first-order reaction rate, are given. There are interesting or noticeable differences in activity and selectivity among the tested Pt-based catalysts. In overall they are not so active as the chromia and vanadia-based catalysts but they have an high life, reason why they can be recommended for this application. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract  The interaction between elastomeric container closures and the solutions they confine presents a potential hazard to the consumer due to extraction of closure ingredients into the dosage form. Each of the major Pharmacopeias, the United States, the European, and the Japanese, prescribe testing procedures for elastomeric closures. These consist of a series of non-specific wet chemical analyses performed on samples extracted into water or, in some cases, isopropanol (IPA) or the drug product vehicle. No consideration is given to the extracting potential of the drug product. Results from our testing on ten randomly selected closure samples indicated that these tests are not sensitive or specific enough to accurately measure the levels of extractables. Therefore, an HPLC gradient method was developed which had the required sensitivity and specificity. The prescribed compendial extractions, when performed on the various stopper types, proved inefficient and experiments were conducted in an attempt to improve them. These included increasing the time of the extractions, increasing the closure surface area, and increasing the strength of the extracting solvent (methylene chloride). The HPLC gradient method and the compendial wet chemical tests were then used to evaluate the stopper extractables. Results of the compendial analyses on the prescribed aqueous extractions were inconclusive as the number and relative amount of extractables in the closure could not be measured. The results of the compendial testing were only marginally improved using the stronger extraction conditions. Testing was dramatically improved, however, using the HPLC gradient method. As many as twenty extractables were detected in some of the samples and, unlike the compendial analysis, low level extractables were detected in the water samples. Identification of some of the extractables was accomplished via GC/MS.

Abstract  Biodegradation of chloroform (CF) was examined in a methanogenic enrichment culture grown on dichloromethane (DCM) as the sole organic carbon and energy source, with and without the addition of supplemental cyanocobalamin. In the absence of cyanocobalamin, the principal products of [C-14] CF biodegradation were (CO2)-C-14 and [C-14]DCM. The extent of CF reduction to DCM increased significantly when CF was biodegraded in the presence of a large amount of DCM. The addition of cyanocobalamin enhanced CF biodegradation in two ways. First, the rate of CF biodegradation increased approximately 10-fold. Second, the metallocofactor increased the extent of CF oxidation to CO2 and virtually eliminated the accumulation of DCM. These effects were not observed in autoclaved cultures supplemented with cyanocobalamin. When cyanocobalamin was added to viable cultures, as much as 10% of the [C-14]CF transformed accumulated as C-14-labeled carbon monoxide. This suggested that the oxidation of CF to CO2 proceeds via net hydrolysis to CO. CF levels as high as 2.2 mM were readily transformed, without accumulation of DCM, at cyanocobalamin to CF molar ratios of 3-5%. Although the organism or consortium responsible for CF biodegradation was not identified, prior work with DCM suggests that acetogenic bacteria are involved.

Abstract  The facile phase-transfer of large, water-soluble metal nanoparticles to nonpolar solvent is reported here. Thiol-terminated polystyrene (PS-SH) is ligand-exchanged onto water-soluble metal nanoparticles in single-phase acetone/water mixtures, generating a precipitate. The solvent is then removed and the particles are redissolved in nonpolar solvent. This approach is demonstrated for nanoparticles of different metal (Au and Ag), size (3 to >100 nm), shape (spheres, rods, and wires, etc.), and leaving ligand (citrate, cetyltrimethylammonium bromide, poly(vinylpyrrolidone), and 4-dimethylaminopyridine. The resulting PS-SH-stabilized nanoparticles maintain their initial size and shape, and are highly stable. They are soluble in various organic solvents (toluene, benzene, chloroform, dichloromethane, and tetrahydrofuran), and can be readily dried, purified, and re-dissolved. This method makes possible the utilization of a full range of existing nanoparticle cores in nonpolar solvents with a single ligand. It provides access to numerous nanomaterials that cannot be obtained through direct synthesis in nonpolar solvent, and is expected to be of significant value in a number of applications.

Abstract  Iron-based degradative solidification/stabilization (DS/S-Fe(II)) is a modification of conventional solidification/stabilization (S/S) that incorporates degradative processes for organic contaminant destruction with immobilization. This study investigated the effectiveness of a binder mixture of Portland cement and slag in a DS/S-Fe(II) system to treat trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), trichloromethane (CF), and dichloromethane (MC), which are major chlorinated hydrocarbons contained in waste oils and waste organic solvents. For TCE, 1,1-DCE, and VC, degradation experiments were conducted using three different binder combinations with Fe(II) (cement/Fe(II), slag/Fe(II), and cement/slag/Fe(II)). When cement and slag were mixed at a 1:1 ratio (% wt), the TCE and 1,1-DCE dechlorination rate was enhanced compared to that when cement or slag was used alone with Fe(II). Also, batch experiments were conducted in the solid phase consisting of cement, slag, sand, and Fe(II) to treat liquid wastes that contain chlorinated compounds at high concentrations. TCE was completely removed after 5 days in the cement/slag/sand/Fe(II) system, in which the initial TCE concentration was 11.8mM, with Fe(II) concentration of 565 mM. While the CF concentration was decreased by 95% after 5 days when the initial CF and Fe(II) concentration was 0.25 mM and 200 mM, respectively. However, MC was not degraded with the cement/slag/Fe(II) system.

Abstract  The objective of this study was to predict the inhalation toxicokinetics of chemicals in mixtures using an integrated QSAR-PBPK modelling approach. The approach involved: (1) the determination of partition coefficients as well as V(max) and K(m) based solely on chemical structure for 53 volatile organic compounds, according to the group contribution approach; and (2) using the QSAR-driven coefficients as input in interaction-based PBPK models in the rat to predict the pharmacokinetics of chemicals in mixtures of up to 10 components (benzene, toluene, m-xylene, o-xylene, p-xylene, ethylbenzene, dichloromethane, trichloroethylene, tetrachloroethylene, and styrene). QSAR-estimated values of V(max) varied compared with experimental results by a factor of three for 43 out of 53 studied volatile organic compounds (VOCs). K(m) values were within a factor of three compared with experimental values for 43 out of 53 VOCs. Cross-validation performed as a ratio of predicted residual sum of squares and sum of squares of the response value indicates a value of 0.108 for V(max) and 0.208 for K(m). The integration of QSARs for partition coefficients, V(max) and K(m), as well as setting the K(m) equal to K(i) (metabolic inhibition constant) within the mixture PBPK model allowed to generate simulations of the inhalation pharmacokinetics of benzene, toluene, m-xylene, o-xylene, p-xylene, ethylbenzene, dichloromethane, trichloroethylene, tetrachloroethylene and styrene in various mixtures. Overall, the present study indicates the potential usefulness of the QSAR-PBPK modelling approach to provide first-cut evaluations of the kinetics of chemicals in mixtures of increasing complexity, on the basis of chemical structure.

Abstract  Toxicity and exposure evaluations remain the two of the key components of human health assessment. While improvement in exposure assessment relies on a better understanding of human behavior patterns, toxicity assessment still relies to a great extent on animal toxicity testing and human epidemiological studies. Recent advances in computer modeling of the dose-response relationship and distribution of xenobiotics in humans to important target tissues have advanced our abilities to assess toxicity. In particular, physiologically based pharmacokinetic (PBPK) models are among the tools than can enhance toxicity assessment accuracy. Many PBPK models are available to the health assessor, but most are so difficult to use that health assessors rarely use them. To encourage their use these models need to have transparent and user-friendly formats. To this end the Agency for Toxic Substances and Disease Registry (ATSDR) is using translational research to increase PBPK model accessibility, understandability, and use in the site-specific health assessment arena. The agency has initiated development of a human PBPK tool-kit for certain high priority pollutants. The tool kit comprises a series of suitable models. The models are recoded in a single computer simulation language and evaluated for use by health assessors. While not necessarily being state-of-the-art code for each chemical, the models will be sufficiently accurate to use for screening purposes. This article presents a generic, seven-compartment PBPK model for six priority volatile organic compounds (VOCs): benzene (BEN), carbon tetrachloride (CCl(4)), dichloromethane (DCM), perchloroethylene (PCE), trichloroethylene (TCE), and vinyl chloride (VC). Limited comparisons of the generic and original model predictions to published kinetic data were conducted. A goodness of fit was determined by calculating the means of the sum of the squared differences (MSSDs) for simulation vs. experimental kinetic data using the generic and original models. Using simplified solvent exposure assumptions for oral ingestion and inhalation, steady-state blood concentrations of each solvent were simulated for exposures equivalent to the ATSDR Minimal Risk Levels (MRLs). The predicted blood levels were then compared to those reported in the National Health and Nutrition Examination Survey (NHANES). With the notable exception of BEN, simulations of combined oral and inhalation MRLs using our generic VOC model yielded blood concentrations well above those reported for the 95th percentile blood concentrations for the U.S. populations, suggesting no health concerns. When the PBPK tool kit is fully developed, risk assessors will have a readily accessible tool for evaluating human exposure to a variety of environmental pollutants.

Abstract  Cation exchange capacity (CEC) and exchangeable cation composition are important properties in defining water-sediment interactions in contaminant transport scenarios, such as the seepage of process-affected water from oil sands tailings impoundments. At present, detailed characterization of these properties has been overlooked in the surficial Pleistocene sediments of the Athabasca Oil Sands region in Canada. Although a great variety of methods for determining CEC exist and continue to be developed, there is a deficiency in detailed comparisons amongst these methods in the literature, and consequently uncertainty still remains as to which extractants/methods are most suitable for use with sediments containing partially soluble carbonate salts. The present study (1) conducts an up-to-date evaluation of several distinct methods for their suitability in characterizing cation exchange properties in mildly calcareous sediments; using them to (2) evaluate the sorptive capacity and easily displaceable cations of mildly calcareous, surficial sediments near Fort McMurray, Alberta. Four conceptually different CEC methods were chosen: (a) a summation method (Lithium Chloride extractant); (b) a method that displaces an index cation after intermediary washes (Sodium Acetate-Ammonium Acetate); (c) a method using a high affinity cation complex (Silver Thiourea); and (d) a titration method using an organic cationic dye (Methylene Blue). Exchangeable cations were characterized using the Lithium Chloride and Silver Thiourea methods. Analysis suggests that the Methylene Blue test is least impacted by the presence of carbonate mineral phases. Results from field sediments suggest that the exchangeable cations, in decreasing abundance, consist of Ca > Mg > K > NH4 > Na; while the CEC was found to be 4.7 +/- 2.7 meq 100 g(-1) in the clay-rich glacial till, 0.7 +/- 0.0 meq 100 g(-1) in the underlying sand and 4.1 +/- 2.3 meq 100 g(-1) in the till-sand transition zone. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  The existing rapid method for the determination of anionic surfactants in aqueous solutions relies on the association of the cationic methylene blue dye with the anionic surfactant to form an electroneutral complex that is subsequently extracted into chloroform and determined spectrophotometrically. This methylene blue active substance (MBAS) assay suffers from salt interference in estuarine and marine waters due to the high concentration of chloride (Cl-) ions. The interference was shown to arise from the association of Cl- ions with the cationic methylene blue dye, which, although weak, becomes significant at the elevated concentrations of Cl- in marine water. Analysis of the kinetics of the formation and extraction into chloroform of complexes of methylene blue with a typical anionic surfactant (sodium dodecyl sulfate, SDS) and with Cl- ions revealed that the efficacy of the extraction step was critical in yielding reliable data. Based on these results, a modified, simple one-step MBAS method is described that overcomes interference by salt.

Abstract  Catalytic oxidation of isopropanol and o-xylene alone as well as in mixture was investigated over basic NaX zeolite. Experiments were carried out in wet air (11,000 ppm of water) and at a high gas hourly space velocity (GHSV) of 18,000 h super(-1). Results show an inhibiting effect of the o-xylene on the isopropanol destruction whereas the isopropanol has no effect on the o-xylene destruction. Adsorption experiments as well as molecular modelling seem to demonstrate that this inhibiting effect of o-xylene is due to the adsorption of this aromatic VOCs near the apertures of the NaX supercages limiting the access of isopropanol to the basic active sites of this zeolite. Furthermore, the concentration of o-xylene influences the formation of secondary products (propene, coke) resulting from the isopropanol transformation.

Abstract  Coking over two H-mordenites (framework SiO(2)/Al(2)O(3) ratios of 15 and 75) was studied during o-xylene isomerization at temperatures between 523 and 723 K. Despite its lower acid site density the deeply dealuminated sample was the most active and more stable. This is due to the presence of mesopores created during the dealumination which render the diffusion of organic molecules quasi tridimensional, thus reducing both diffusive constraints and the deactivating effect of coke, with both samples coke aromaticity increased and the yield in coke soluble in methylene chloride decreased as the temperature increased. The composition of this coke fraction was strongly affected by reaction temperature but not by the characteristics of the mordenite samples. Whatever the temperature, coke components remained trapped in the mordenite pores, At low temperature, this trapping was due to their low volatility and/or strong adsorption, at high temperature to their steric blockage. Coke oxidation was practically independent of the coke content and composition but was favoured by the density of the acid sites. (C) 1997 Academic Press.

Abstract  Compound specific isotope analysis (CSIA) has been applied to monitor bioremediation of groundwater contaminants and provide insight into mechanisms of transformation of chlorinated ethanes. To date there is little information on its applicability for chlorinated methanes. Moreover, published enrichment factors (ε) observed during the biotic and abiotic degradation of chlorinated alkanes, such as carbon tetrachloride (CT); 1,1,1-trichloroethane (1,1,1-TCA); and 1,1-dichloroethane (1,1-DCA), range from -26.5‰ to -1.8‰ and illustrate a system where similar C-Cl bonds are cleaved but significantly different isotope enrichment factors are observed. In the current study, biotic degradation of chloroform (CF) to dichloromethane (DCM) was carried out by the Dehalobacter containing culture DHB-CF/MEL also shown to degrade 1,1,1-TCA and 1,1-DCA. The carbon isotope enrichment factor (ε) measured during biodegradation of CF was -27.5‰ ± 0.9‰, consistent with the theoretical maximum kinetic isotope effect for C-Cl bond cleavage. Unlike 1,1,1-TCA and 1,1-DCA, reductive dechlorination of CF by the Dehalobacter-containing culture shows no evidence of suppression of the intrinsic maximum kinetic isotope effect. Such a large fractionation effect, comparable to those published for cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) suggests CSIA has significant potential to identify and monitor biodegradation of CF, as well as important implications for recent efforts to fingerprint natural versus anthropogenic sources of CF in soils and groundwater.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. 1,1,2-Trichloroethylene (TCE), 1,1-dichloroethylene, cis and trans-1,2-dichloroethylene and tetrachloroethylene (PCE), at concentrations of 20 ppm in aqueous solutions were rapidly hydrodechlorinated to ethane (in a few minutes), on the surface of palladized iron in batch experiments that were performed in closed vials. No intermediate reaction products such as 1,1-dichloroethylene, 1,2-dichloroethylenes and vinyl chloride were detected at concentrations 1 ppm either in the headspace or in solution. The chloromethanes, CCl4, CHCl3 and CH2Cl2 were also dechlorinated to methane on palladized iron; the CCl4 was dechlorinated in a few minutes, the CHCl3, in less than an hour and the CH2Cl2, in 4-5 h. These results indicate that an above-ground treatment method can be designed for the treatment of groundwater contaminated with low molecular weight chlorinated hydrocarbons.

Abstract  Cross-linked quaternary chitosan salt (QCS) was used for perchlorate removal from aqueous solution. The effect of pH and co-existing anions on the adsorption process, adsorption isotherms, kinetics and thermodynamics was investigated. The thermo stability and the solubility in water were improved after QCS was cross-linked by glutaraldehyde. The cross-linked QCS showed maximum monolayer adsorption capacity of 119.0 mg/g, which was 2.5 times higher than protonated cross-linked chitosan. The adsorption process was almost independent of pH in a range from 4.0 to 10.3, which was much wider than using protonated cross-linked chitosan with applicable pH range of 4.0-6.0. The effect from co-existing anions on perchlorate adsorption followed the order: Cl- > NO3- > SO42-. The adsorption data fitted Langmuir and Tempkin isotherm models well. Adsorption kinetic analysis showed that chemical adsorption was a rate-limiting stage during the adsorption process. The adsorption reaction was exothermic and spontaneous according to the calculated result of adsorption thermodynamics. The spent adsorbents could be effectively regenerated by NaCl solution with the concentration higher than 0.3%. Fourier transformation infrared spectra and the change of Cl- concentration in solution demonstrated that the ion-exchange interaction might occur between the chloride ions on the quaternary ammonium salt groups of the cross-linked QCS and the perchlorate ions in solution, resulting in the perchlorate adsorption onto the cross-linked QCS. (C) 2012 Elsevier B.V. All rights reserved.