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Chlorinated Solvents (chlorinated + solvent)
Selected AbstractsDicopper(II) Complexes with the Enantiomers of a Bidentate Chiral Reduced Schiff Base: Inclusion of Chlorinated Solvents and Chiral Recognition of1,2-Dichloroethane Rotamers in the Crystal LatticeEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006Vamsee Krishna Muppidi Abstract Bisphenoxo-bridged dicopper(II) complexes [Cu2Ln2Cl2] {1 (n = 1) and 2 (n = 2)} with the N,O-donor reduced Schiff bases N -(2-hydroxybenzyl)-(R)-,-methylbenzylamine (HL1) and N -(2-hydroxybenzyl)-(S)-,-methylbenzylamine (HL2) have been synthesised and characterised. In both 1 and 2, the bidentate chiral ligands coordinate the metal centres through the secondary amine N atom and the bridging phenolate O atom. The chloride ion occupies the fourth coordination site and completes a slightly distorted square-planar NO2Cl environment around each copper(II) centre. Magnetic susceptibility measurements in the solid state suggest a strong antiferromagnetic interaction between the metal centres in both complexes. Both 1 and 2 readily form 1:1 host-guest compounds with chlorinated solvents such as CH2Cl2, CHCl3 and Cl(CH2)2Cl. All the host-guest compounds crystallise in noncentrosymmetric space groups. 1·CH2Cl2 and 2·CH2Cl2 crystallise in the P21 space group while 1·CHCl3, 2·CHCl3, 1·Cl(CH2)2Cl and 2·Cl(CH2)2Cl crystallise in the P212121 space group. In these inclusion crystals, the C,H···Cl interactions between the guest and the host molecules are primarily responsible for enclatheration of the chloroalkane molecules. In the case of CH2Cl2, one of its Cl atoms acts as the acceptor. On the other hand, for CHCl3 and Cl(CH2)2Cl, the metal coordinated Cl atom of the host complex acts as the acceptor. The structures of 1·(P)-Cl(CH2)2Cl and 2·(M)-Cl(CH2)2Cl provide rare examples for chiral recognition of the right handed (P) and the left handed (M) gauche forms of Cl(CH2)2Cl in molecular assemblies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Soil Vapor Extraction and Chemical Oxidation to Remediate Chlorinated Solvents in Fractured Crystalline Bedrock: Pilot Study Results and Lessons LearnedREMEDIATION, Issue 2 2002H. Jean Cho A pilot study was completed at a fractured crystalline bedrock site using a combination of soil vapor extraction (SVE) and in-situ chemical oxidation (ISCO) with Fenton's Reagent. This system was designed to destroy 1,1,1-trichloroethane (TCA) and its daughter products, 1,1-dichloroethene (DCE) and 1,1-dichloroethane (DCA). Approximately 150 pounds of volatile organic compounds (VOCs) were oxidized in-situ or removed from the aquifer as vapor during the pilot study. Largely as a result of chemical oxidation, TCA concentrations in groundwater located within a local groundwater mound decreased by 69 to 95 percent. No significant rebound in VOC concentration was observed in these wells. Wells located outside of the groundwater mound showed less dramatic decreases in VOC concentration, and the data show that vapor stripping and short-term groundwater migration following the oxidant injection were the key processes at these wells. Although the porosity of the aquifer at the site is on the order of 2 percent or less, the pilot study showed that SVE could be an effective remedial process in fractured crystalline rock. © 2002 Wiley Periodicals, Inc. [source] Construction of a permeable reactive barrier in a residential neighborhoodREMEDIATION, Issue 4 2002Peter Richards In June 2001, the Massachusetts Department of Environmental Protection (DEP) installed a permeable reactive barrier (PRB) within a roadway in Needham, Massachusetts, to treat a plume of chlorinated solvents migrating toward two public water-supply wells located in the adjacent town of Wellesley, Massachusetts. The solvents originated from an electronics manufacturer located approximately 2,300 feet upgradient of the roadway and 5,200 feet upgradient of the public supply wells. Chlorinated solvents, primarily trichloroethene (TCE), had migrated past the roadway to within 300 feet of the public supply wells. Two contaminant transport models prepared by the DEP's design contractor and the EPA indicated that the plume would reach the well field if no response actions were taken. To mitigate the future impact to the municipal well field, the DEP decided to install a PRB composed of zero-valent granular iron across the path of the plume along Central Avenue in Needham. Though several dozen PRBs have been installed at sites worldwide and the technology is no longer considered innovative, the application of the technology in a roadway that receives 17,000 vehicles per day within a residential neighborhood is unique and presented difficulties not typically associated with PRB installations. The Needham PRB was also one of the first zero-valent iron PRBs installed using the slurry trench method to treat chlorinated compounds. © 2002 Wiley Periodicals, Inc. [source] Phytotoxicity of chlorinated aliphatics to hybrid poplar (Populus deltoides × nigra DN34)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2001Annette C Dietz Abstract Effects of a series of chlorinated ethenes and ethanes on hybrid poplar (Populus deltoides × nigra DN34) were assessed in laboratory experiments. Poplar cuttings were grown in sealed reactors with hydroponic solutions and were exposed to a chlorinated solvent for a period of two weeks. Exposure concentrations ranged from 0 to 0.4 mM for perchloroethylene to 0 to 8.4 mM for 1,1-dichloroethane. Effects were assessed by gravimetrically monitoring transpiration and measuring change in cutting mass. The zero-growth concentrations of the chemicals tested were 0.3 mM perchloroethylene, 0.9 mM trichloroethylene, 0.9 mM 1,1,2,2-tetrachloroethane, 2.0 mM 1,1,1-trichloroethane, 2.3 mM 1,1,2-trichloroethane, 4.8 mM trans -dichloroethylene, 5.6 mM 1,1-dichlor-oethylene, 6.0 mM cis -dichloroethylene, and 10.7 mM 1,1-dichloroethane. Adverse effects were found to increase with increasing number of chlorine atoms within a homologous series of ethenes or ethanes. Ethenes were more toxic than similarly chlorinated ethanes. [source] Remediation of chlorinated ethenes, ethanes, and methanes in groundwater using carbon- and iron-based electron donorREMEDIATION, Issue 4 2009Nanjun Shetty Field-scale pilot tests were performed to evaluate enhanced reductive dechlorination (ERD) of dissolved chlorinated solvents at a former manufacturing facility located in western North Carolina (the site). Results of the site assessment indicated the presence of two separate chlorinated solvent,contaminated groundwater plumes, located in the northern and southern portions of the site. The key chlorinated solvents found at the site include 1,1,2,2-tetrachloroethane, trichloroethene, and chloroform. A special form of EHC® manufactured by Adventus Americas was used as an electron donor at this site. In this case, EHC is a pH-buffering electron donor containing controlled release carbon and ZV Iron MicroSphere 200, a micronscale zero-valent iron (ZVI) manufactured by BASF. Approximately 3,000 pounds of EHC were injected in two Geoprobe® boreholes in the saprolite zone (southern plume), and 3,500 pounds of EHC were injected at two locations in the partially weathered rock (PWR) zone (northern plume) using hydraulic fracturing techniques. Strong reducing conditions were established immediately after the EHC injection in nearby monitoring wells likely due to the reducing effects of ZV Microsphere 200. After approximately 26 months, the key chlorinated VOCs were reduced over 98 percent in one PWR well. Similarly, the key chlorinated solvent concentrations in the saprolite monitoring wells decreased 86 to 99 percent after initial increases in concentrations of the parent chlorinated solvents. The total organic carbon and metabolic acid concentrations indicated that the electron donor lasted over 26 months after injection in the saprolite aquifer. © 2009 Wiley Periodicals, Inc. [source] Mobility control: How injected surfactants and biostimulants may be forced into low-permeability unitsREMEDIATION, Issue 3 2003Richard E. Jackson Recovering dense nonaqueous-phase liquid (DNAPL) remains one of the most difficult problems facing the remediation industry. Still, the most common method of recovering DNAPL is to physically remove the contaminants using common technologies such as total fluids recovery pumps, vacuum systems, and "pump-and-treat." Increased DNAPL removal can be attained using surfactants to mobilize and/or solubilize the pollutants. However, very little is understood of the methods developed by petroleum engineers beginning in the 1960s to overcome by-passed, low-permeability zones in heterogeneous oil reservoirs. By injecting or causing the formation of viscous fluids in the subsurface, petroleum engineers caused increased in-situ pressures that forced fluid flow into low permeability units as well as the higher permeability thief zones. Polymer flooding involves injecting a viscous aqueous polymer solution into the contaminated aquifer. Foam flooding involves injecting surfactant to decontaminate the high-permeability zones and then periodic pulses of air to cause a temporary viscous foam to form in the high-permeable zones after all DNAPL is removed. Later surfactant pulses are directed by the foam into unswept low-permeable units. These methods have been applied to DNAPL removal using surfactants but they can also be applied to the injection of bio-amendments into low-permeability zones still requiring continued remediation. Here we discuss the principles of mobility control as practiced in an alluvial aquifer contaminated with chlorinated solvent and coal tar DNAPLs as well as some field results. © 2003 Wiley Periodicals, Inc. [source] Dicopper(II) Complexes with the Enantiomers of a Bidentate Chiral Reduced Schiff Base: Inclusion of Chlorinated Solvents and Chiral Recognition of1,2-Dichloroethane Rotamers in the Crystal LatticeEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006Vamsee Krishna Muppidi Abstract Bisphenoxo-bridged dicopper(II) complexes [Cu2Ln2Cl2] {1 (n = 1) and 2 (n = 2)} with the N,O-donor reduced Schiff bases N -(2-hydroxybenzyl)-(R)-,-methylbenzylamine (HL1) and N -(2-hydroxybenzyl)-(S)-,-methylbenzylamine (HL2) have been synthesised and characterised. In both 1 and 2, the bidentate chiral ligands coordinate the metal centres through the secondary amine N atom and the bridging phenolate O atom. The chloride ion occupies the fourth coordination site and completes a slightly distorted square-planar NO2Cl environment around each copper(II) centre. Magnetic susceptibility measurements in the solid state suggest a strong antiferromagnetic interaction between the metal centres in both complexes. Both 1 and 2 readily form 1:1 host-guest compounds with chlorinated solvents such as CH2Cl2, CHCl3 and Cl(CH2)2Cl. All the host-guest compounds crystallise in noncentrosymmetric space groups. 1·CH2Cl2 and 2·CH2Cl2 crystallise in the P21 space group while 1·CHCl3, 2·CHCl3, 1·Cl(CH2)2Cl and 2·Cl(CH2)2Cl crystallise in the P212121 space group. In these inclusion crystals, the C,H···Cl interactions between the guest and the host molecules are primarily responsible for enclatheration of the chloroalkane molecules. In the case of CH2Cl2, one of its Cl atoms acts as the acceptor. On the other hand, for CHCl3 and Cl(CH2)2Cl, the metal coordinated Cl atom of the host complex acts as the acceptor. The structures of 1·(P)-Cl(CH2)2Cl and 2·(M)-Cl(CH2)2Cl provide rare examples for chiral recognition of the right handed (P) and the left handed (M) gauche forms of Cl(CH2)2Cl in molecular assemblies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Monitoring Subsurface Contamination Using Tree BranchesGROUND WATER MONITORING & REMEDIATION, Issue 1 2007Gayathri Gopalakrishnan This paper proposes a method of assessing the distribution of chlorinated solvents in soil and ground water using tree branches. Sampling branches is a potentially more cost-effective and easier method than sampling tree cores, with less risk of damage to the tree. This approach was tested at Argonne National Laboratory, where phytoremediation is being used to remove tetrachloroethene (PCE), trichloroethene (TCE), and carbon tetrachloride (CCl4) from soil and ground water. The phytoremediation system consists of shallow-rooted willows planted in an area with contaminated soil and deep-rooted poplars planted in an area with clean soil and contaminated ground water. Branch samples were collected from 126 willows and 120 poplars. Contaminant concentrations from 31 soil borings and six monitoring wells were compared to those from branches of adjacent trees. Regression equations with correlation coefficients of at least 0.89 were obtained, which were found to be chemical specific. Kriged profiles of TCE concentration based on soil and willow branch data were developed and showed good agreement. Profiles based on ground water data could not be developed due to lack of sufficient monitoring wells for a meaningful statistical analysis. An analytical model was used to simulate TCE concentrations in tree branches from soil concentrations; the diffusion coefficient for TCE in the tree was used as the fitting parameter and the best-fit value was two orders of magnitude greater than literature values. This work indicates that tree branch sampling is a useful approach to assess contaminant distribution and potentially to determine where to locate monitoring wells or perform detailed soil analysis. Further research is necessary prior to using this method as a quantitative monitoring tool for soil and ground water. [source] DNAPL Characterization Methods and Approaches, Part 2: Cost ComparisonsGROUND WATER MONITORING & REMEDIATION, Issue 1 2002Mark L. Kram Contamination from the use of chlorinated solvents, often classified as dense nonaqueous phase liquids (DNAPLs) when in an undissolved state, pose environmental threats to ground water resources worldwide. DNAPL site characterization method performance comparisons are presented in a companion paper (Kram et al. 2001). This study compares the costs for implementing various characterization approaches using synthetic unit model scenarios (UMSs), each with particular physical characteristics. Unit costs and assumptions related to labor, equipment, and consumables are applied to determine costs associated with each approach for various UMSs. In general, the direct-push sensor systems provide cost-effective characterization information in soils that are penetrable with relatively shallow (less than 10 to 15 m) water tables. For sites with impenetrable lithology using direct-push techniques, the Ribbon NAPL Sampler Flexible Liner Underground Technologies Everting (FLUTe) membrane appears to be the most cost-effective approach. For all scenarios studied, partitioning interwell tracer tests (PITTs) are the most expensive approach due to the extensive pre-and post-PITT requirements. However, the PITT is capable of providing useful additional information, such as approximate DNAPL saturation, which is not generally available from any of the other approaches included in this comparison. [source] Solubility and degradation of polyhydroxyalkanoate biopolymers in propylene carbonateAICHE JOURNAL, Issue 6 2010Christopher W. J. McChalicher Abstract New biobased materials and chemicals require different processing strategies than petroleum-derived commodities. The extraction and recovery of polyhydroxyalkanoate (PHA) biopolymers from the residual cellular biomass is particularly difficult because the polymer is accumulated within the cell. PHAs have low solubility in many classical polymer solvents and are most often dissolved using undesirable chlorinated solvents. The solubility kinetics is greatly diminished when these polymers are highly crystalline. Here, 1,2-propylene carbonate is used to dissolve highly crystalline polyhydroxybutyrate at ambient pressures and moderate temperatures. We have used kinetic studies of the dissolution of the crystalline material to determine the energy barrier for dissolution of the system. Further, the degradation of polyhydroxybutyrate and similarly prepared PHA block copolymers were studied during this extraction process using molecular weight characterization by gel permeation chromatography. Finally, we have used these findings to extract PHA block copolymers from dried biomass at the bench scale. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Synthesis of a [60] fullerene,Functionalized isotactic polypropylene derivativeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Gerardo Martínez Abstract The covalent attachment of [60] fullerene (C60) to isotactic polypropylene (i-PP) is achieved by direct reaction in 1,2,4-trichlorobenzene (TCB) solution in the presence of dicumyl peroxide (DCP). The chemically modified pendant C60/i-PP polymers are soluble in chlorinated solvents and have been characterized by ultraviolet,visible and fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, cyclic voltametry, and thermogravimetric analysis. From the results it can be concluded that the modification of i-PP by grafting via a free-radical reaction competes with the possibility of chain scission of i-PP due to the presence of DCP. The functionalized polymers crystallize in the monoclinic crystal modification, and have high crystallinity. The incorporation of C60 significantly enhances the thermal stability of the i-PP. Electrochemical measurements demonstrate good electron acceptor properties of the fullerenated i-PP samples. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6722,6733, 2008 [source] Novel organosoluble and colorless poly(ether imide)s based on 3,3-bis[4-(3,4-dicarboxyphenoxy)phenyl]phthalide dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Chin-Ping Yang Abstract A novel series of colorless and highly organosoluble poly(ether imide)s were prepared from 3,3-bis[4-(3,4-dicarboxyphenoxy)phenyl]phthalide dianhydride with various fluorinated aromatic bis(ether amine)s via a conventional two-stage process that included ring-opening polyaddition to form the poly(amic acid)s followed by cyclodehydration to produce the polymer films. The poly(ether imide)s showed excellent solubility, with most of them dissoluble at a concentration of 10 wt % in amide polar solvents, in ether-type solvents, and even in chlorinated solvents. Their films had a cutoff wavelength between 358 and 373 nm, and the yellowness index ranged from 3.1 to 9.5. The glass-transition temperatures of the poly(ether imide) series were recorded between 237 and 297 °C, the decomposition temperatures at 10% weight loss were all above 494 °C, and the residue was more than 54% at 800 °C in nitrogen. These films showed high tensile strength and also were characterized by higher solubility, lighter color, and lower dielectric constants and moisture absorption than an analogous nonfluorinated polyimide series. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3140,3152, 2006 [source] Synthesis and characterization of phthalazinone containing poly(arylene ether)s via a novel N,C coupling reactionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2003S. J. Wang Abstract High-molecular-weight poly(phthalazinone)s with very high glass-transition temperatures (Tg's) were synthesized via a novel N,C coupling reaction. New bisphthalazinone monomers (7a,e) were synthesized from 2-(4-chlorobenzoyl) phthalic acid in two steps. Poly(phthalazinone)s, having inherent viscosities in the range of 0.34,0.91 dL/g, were prepared by the reaction of the bis(phthalazinone) monomers with an activated aryl halide in a dipolar aprotic solvent in the presence of potassium carbonate. The poly(phthalazinone)s exhibited Tg's greater than 230 °C. polymer 8b synthesized from diphenyl biphenol and bis(4-flurophenyl) sulfone demonstrated the highest Tg of 297 °C. Thermal stabilities of the poly(phthalazinone)s were determined by thermogravimetric analysis. All the poly(phthalazinone)s showed a similar pattern of decomposition with no weight loss below 450 °C in nitrogen. The temperatures of 5% weight loss were observed to be about 500 °C. The poly(phthalazinone)s containing 4,4,-isopropylidenediphenol and 4,4,-(hexafluoroisopropylidene) diphenol and diphenyl ether linkage were soluble in chlorinated solvents such as chloroform. Other poly-(phthalazinone)s were soluble in dipolar aprotic solvents such as N,N,-dimethylacetamide. The soluble poly(phthalazinone)s can be cast as flexible films from solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2481,2490, 2003 [source] An evaluation of permeable reactive barrier projects in CaliforniaREMEDIATION, Issue 1 2009John P. Muegge Permeable reactive barriers made of zero-valent iron (ZVI PRBs) have become a prominent remediation technology in addressing groundwater contamination by chlorinated solvents. Many ZVI PRBs have been installed across the United States, some as research projects, some at the pilot scale, and many at full scale. As a passive and in situ remediation technology, ZVI PRBs have many attractive features and advantages over other approaches to groundwater remediation. Ten ZVI PRBs installed in California were evaluated for their performance. Of those ten, three are discussed in greater detail to illustrate the complexities that arise when quantifying the performance of ZVI PRBs, and to provide comment on the national debate concerning the downgradient effects of source-zone removal or treatment on plumes of contaminated groundwater. © 2009 Wiley Periodicals, Inc. [source] Remediation of chlorinated ethenes, ethanes, and methanes in groundwater using carbon- and iron-based electron donorREMEDIATION, Issue 4 2009Nanjun Shetty Field-scale pilot tests were performed to evaluate enhanced reductive dechlorination (ERD) of dissolved chlorinated solvents at a former manufacturing facility located in western North Carolina (the site). Results of the site assessment indicated the presence of two separate chlorinated solvent,contaminated groundwater plumes, located in the northern and southern portions of the site. The key chlorinated solvents found at the site include 1,1,2,2-tetrachloroethane, trichloroethene, and chloroform. A special form of EHC® manufactured by Adventus Americas was used as an electron donor at this site. In this case, EHC is a pH-buffering electron donor containing controlled release carbon and ZV Iron MicroSphere 200, a micronscale zero-valent iron (ZVI) manufactured by BASF. Approximately 3,000 pounds of EHC were injected in two Geoprobe® boreholes in the saprolite zone (southern plume), and 3,500 pounds of EHC were injected at two locations in the partially weathered rock (PWR) zone (northern plume) using hydraulic fracturing techniques. Strong reducing conditions were established immediately after the EHC injection in nearby monitoring wells likely due to the reducing effects of ZV Microsphere 200. After approximately 26 months, the key chlorinated VOCs were reduced over 98 percent in one PWR well. Similarly, the key chlorinated solvent concentrations in the saprolite monitoring wells decreased 86 to 99 percent after initial increases in concentrations of the parent chlorinated solvents. The total organic carbon and metabolic acid concentrations indicated that the electron donor lasted over 26 months after injection in the saprolite aquifer. © 2009 Wiley Periodicals, Inc. [source] A design tool for planning emulsified oil-injection systemsREMEDIATION, Issue 4 2008Aaron M. Weispfenning Emulsified oils have been used to stimulate anaerobic bioremediation at hundreds of sites contaminated with chlorinated solvents, perchlorate, heavy metals, and nitrate. A simple spreadsheet-based tool has been developed to assist in the design of injection-only systems for distributing emulsified oils in barriers and area treatments. This tool allows users to quickly compare the relative costs and performance of different injection alternatives and identify a design that is best suited to site-specific conditions. Contact efficiency is estimated using results of prior numerical model simulations and dimensionless scaling factors that relate the volume of oil and water injected to treatment-zone dimensions. Sensitivity analysis results indicate that maximum oil retention is one of the most important factors controlling system performance and cost. © 2008 Wiley Periodicals, Inc. [source] Pilot-scale evaluation of in situ cometabolic bioremediation of TCE in groundwater using PHOSter® technologyREMEDIATION, Issue 2 2008Karl W. Eggers A study was conducted to evaluate the efficacy of PHOSter® technology for treating groundwater contaminated with trichloroethene (TCE) at Edwards Air Force Base, California. The technology consists of injecting a gaseous mixture of air, methane, and nutrients into groundwater with the objective of stimulating the growth of methanotrophs, a naturally occurring microbial group that is capable of catalyzing the aerobic degradation of chlorinated solvents into nontoxic products. Injection operations were performed at one well for a period of three months. Six monitoring wells were utilized for groundwater and wellhead vapor monitoring and for groundwater and microbial sampling. In the five monitoring wells located within 44 feet of the injection well, the following results were observed: dissolved oxygen concentrations increased to a range between 6 and 8 milligrams per liter (,g/L); the biomass of target microbial groups increased by one to five orders of magnitude; and TCE concentrations decreased by an average of 92 percent, and to below the California primary maximum contaminant level (MCL; 5 micrograms per liter [µg/L]) in the well closest to the injection well. © 2008 Wiley Periodicals, Inc., [source] Considerations for the design of organic mulch permeable reactive barriersREMEDIATION, Issue 1 2007Farrukh Ahmad Organic mulch consists of insoluble carbon biopolymers that are enzymatically hydrolyzed during decomposition to release aqueous total organic carbon (TOC). The released TOC is utilized by microorganisms as an electron donor to transform electrophilic contaminants via reductive pathways. Over the last decade, organic mulch permeable reactive barriers (PRBs), or biowalls, have received increased interest as a relatively inexpensive slow-release electron donor technology for addressing contaminated groundwater. To date, biowalls have been installed to enhance the passive bioremediation of groundwater contaminated with a variety of electrophilic compounds, including chlorinated solvents, explosives, and perchlorate. In addition, several mulch biowall projects are currently under way at several U.S. Department of Defense facilities. However, at the present time, the guidelines available for the design of mulch PRBs are limited to a few case studies published in the technical literature. A biowall design, construction, and operation protocol document is expected to be issued by the Air Force Center for Environmental Excellence in 2007. In this publication, three technical considerations that can have a significant impact on the design and performance of mulch PRBs are presented and discussed. These technical considerations are: (1) hydraulic characteristics of the mulch bed; (2) biochemical characteristics of different types of organic amendments used as mulch PRB fill materials; and (3) a transport model that can be used to estimate the required PRB thickness to attain cleanup standards. © 2007 Wiley Periodicals, Inc. [source] A deterministic approach to evaluate and implement monitored natural attenuation for chlorinated solventsREMEDIATION, Issue 4 2007Michael J. Truex A US EPA directive and related technical protocol outline the information needed to determine if monitored natural attenuation (MNA) for chlorinated solvents is a suitable remedy for a site. For some sites, conditions such as complex hydrology or perturbation of the contaminant plume caused by an existing remediation technology (e.g., pump-and-treat) make evaluation of MNA using only field data difficult. In these cases, a deterministic approach using reactive transport modeling can provide a technical basis to estimate how the plume will change and whether it can be expected to stabilize in the future and meet remediation goals. This type of approach was applied at the Petro-Processors Inc. Brooklawn site near Baton Rouge, Louisiana, to evaluate and implement MNA. This site consists of a multicomponent nonaqueous-phase source area creating a dissolved groundwater contamination plume in alluvial material near the Mississippi River. The hydraulic gradient of the groundwater varies seasonally with changes in the river stage. Due to the transient nature of the hydraulic gradient and the impact of a hydraulic containment system operated at the site for six years, direct field measurements could not be used to estimate natural attenuation processes. Reactive transport of contaminants were modeled using the RT3D code to estimate whether MNA has the potential to meet the site-specific remediation goals and the requirements of the US EPA Office of Solid Waste and Emergency Response Directive 9200.4-17P. Modeling results were incorporated into the long-term monitoring plan as a basis for evaluating the effectiveness of the MNA remedy. As part of the long-term monitoring plan, monitoring data will be compared to predictive simulation results to evaluate whether the plume is changing over time as predicted and can be expected to stabilize and meet remediation goals. This deterministic approach was used to support acceptance of MNA as a remedy. © 2007 Wiley Periodicals, Inc. [source] Enhanced attenuation: Its place in the remediation of chlorinated solventsREMEDIATION, Issue 2 2007Kimberly Wilson The development and regulatory acceptance of monitored natural attenuation (MNA) as a remedial strategy has forever changed the field of environmental cleanup. MNA is continuing to develop but it is challenged by a lack of a clear definition for the appropriate application of the MNA strategy. This challenge has resulted in the lack of a significant record of restoration and site closure. Environmental professionals face challenges in providing guidance that addresses how to manage these sites when technologies, performance monitoring, and even environmental conditions are subject to further development, refinement, and/or altered perspectives. As our experience and institutional knowledge grows around the implementation of MNA, we have the opportunity to develop "second-generation" management tools and procedures for optimizing sites utilizing MNA as a part of a comprehensive site management plan. This opportunity is the focus of the Enhanced Attenuation: Chlorinated Organics (EACO) Team of the Interstate Technology Regulatory Council (ITRC). The development of the "second-generation" tools/procedures has included defining EA and evaluating, through the use of a national survey of state regulators, the experience with MNA and interest in EA. The results of these two efforts formed the basis for developing a framework that provides a "bridge" from active treatment to MNA. © 2007 Wiley Periodicals, Inc. [source] Construction of a permeable reactive barrier in a residential neighborhoodREMEDIATION, Issue 4 2002Peter Richards In June 2001, the Massachusetts Department of Environmental Protection (DEP) installed a permeable reactive barrier (PRB) within a roadway in Needham, Massachusetts, to treat a plume of chlorinated solvents migrating toward two public water-supply wells located in the adjacent town of Wellesley, Massachusetts. The solvents originated from an electronics manufacturer located approximately 2,300 feet upgradient of the roadway and 5,200 feet upgradient of the public supply wells. Chlorinated solvents, primarily trichloroethene (TCE), had migrated past the roadway to within 300 feet of the public supply wells. Two contaminant transport models prepared by the DEP's design contractor and the EPA indicated that the plume would reach the well field if no response actions were taken. To mitigate the future impact to the municipal well field, the DEP decided to install a PRB composed of zero-valent granular iron across the path of the plume along Central Avenue in Needham. Though several dozen PRBs have been installed at sites worldwide and the technology is no longer considered innovative, the application of the technology in a roadway that receives 17,000 vehicles per day within a residential neighborhood is unique and presented difficulties not typically associated with PRB installations. The Needham PRB was also one of the first zero-valent iron PRBs installed using the slurry trench method to treat chlorinated compounds. © 2002 Wiley Periodicals, Inc. [source] The Use of Natural Systems to Remediate Groundwater: Department of Energy Experience at the Savannah River SiteREMEDIATION, Issue 3 2002Gerald C. Blount Natural remediation is moving toward the forefront as engineers clean groundwater at the Savannah River Site (SRS), a major Department of Energy (DOE) installation near Aiken, South Carolina. This article reviews two successful, innovative remediation methods currently being deployed: biosparging to treat chlorinated solvents and phytoremediation to address tritium in groundwater. The biosparging system reintroduces oxygen into the groundwater and injects nutrient compounds for in-situ remediation. The system has greatly reduced the concentrations of trichloroethylene (TCE) and vinyl chloride in wells downgradient from a sanitary landfill (SLF). Phytoremediation is an emerging technology that promises effective and inexpensive cleanup of certain hazardous wastes. Using natural processes, plants can break down, trap and hold, or transpire contaminants. This article discusses the use of phytoremediation to reduce the discharge of tritium to an on-site stream at SRS. © 2002 Wiley Periodicals Inc.* [source] Aerobic Cometabolism of Halogenated Aliphatic Hydrocarbons: A Technology OverviewREMEDIATION, Issue 1 2000Michael T. Saul Bioremediation of chlorinated solvents has been moving from an innovative to mainstream technology for environmental applications. Cometablism of chlorinated solvents by monooxygenase has been demonstrated for trichloroethylene (TCE). Cl-out microbes combine the dehalogenation of PCE with the monooxygenase destruction of TCE to complete the PCE breakdown pathway. Underthe right conditions, cometabolic bioremediation can be cost effective, fast, and complete. Aerobic bioremediation can augment mass transfer technologies such as pump and treat or sparging/vapor extraction to improve their efficiency. [source] Free radical polymerization of methyl methacrylate initiated by the diphosphine Mo(0) complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2006Ayfer Mente Abstract The polymerization of methyl methacrylate MMA catalyzed by [Mo(CO)4L2] [L2 = diphenylphosphinomethane (dppm), diphenylphosphinoethane (dppe) or diphenylphosphinopropane (dppp)] has been studied. The activity of these single-component catalysts depends on the length of the (CH2)n bridge of diphosphine ligand. Thus, the dppm derivative displays higher activity than dppe or dppp ligands. These complexes, as free radical initiators, afforded the methyl methacrylate polymerization in chlorinated solvents. The mechanism of the polymerization was discussed and a radical mechanism was proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Porphyrin-Functionalized Dendrimers: Synthesis and Application as Recyclable Photocatalysts in a Nanofiltration Membrane ReactorCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2005Suhas A. Chavan Dr. Abstract The convergent synthesis of a series of porphyrin-functionalized pyrimidine dendrimers has been accomplished by a procedure involving the nucleophilic aromatic substitution (NAS) as a key reaction step. The resulting dendritic porphyrin catalysts show high activity in the light-induced generation of singlet oxygen (1O2) from ground-state oxygen. These materials are synthetically useful photosensitizers for the oxidation of various olefinic compounds to the corresponding allylic hydroperoxides. Catalytic activities and regio- and stereoselectivities of the dendritic photosensitizers are comparable to those observed for mononuclear porphyrin catalysts. Recycling of the dendrimer-enlarged homogeneous photocatalysts was possible by solvent-resistant nanofiltration (SRNF) by using an oxidatively stable membrane consisting of a polysiloxane polymer and ultrastable Y zeolite as inorganic filler. Moreover, this membrane technology provides a safe way to isolate the hydroperoxide products under very mild conditions. The membrane showed high retention for the macromolecular catalysts, even in chlorinated solvents, but some oxidative degradation of the porphyrin units of the dendrimer was observed over multiple catalytic runs. [source] Bis (ortho -) chelated Monoanionic Bisphosphinoaryl Ruthenium (II) Complexes: Synthesis, Characterization and Reactivity,CHINESE JOURNAL OF CHEMISTRY, Issue 3 2002Gerard P. M. Klink Abstract Bisphosphinoaryl ruthenium (II) compounds are synthesized using two distinct synthetic routes. One route, direct cycloruthenation, consists of the reaction of the parent arene compound R-PCHP with [RuCl2 (PPh3)3] in chlorinated solvents. However, this route suffers from major drawbacks because HCl is formed as well as free triphenylphoshine. The other route, the transcyclometalation reaction, involves the interconversion of one cyclometalated ligand metal complex, [RuCl (NCN) (PPh3)], into another complex, [RuCl (R-PCP) (PPh3)], with concomitant consumption and formation of the corresponding arenes R-PCHP and NCHN, respectively. [source] | ||||||||||