Trichloroethylene In Air Research Articles

Cesium ion-guided detection of trichloroethylene in air

Whereas the close associations of cesium ion with organochlorine compounds have been previously documented, the present report is the first attempt to exploit these interactions to create a trichloroethylene (TCE)-selective sensor. Gold monolayer-protected clusters peripherally functionalized with Cs+ ions were used to prepare a chemiresistance film on MEMS-fabricated interdigitated electrodes. Vapor sensing properties of the cesium-rich chemiresistor were determined using a panel of chlorinated hydrocarbons including TCE as well as polar and non-polar VOCs for comparison. The sensor was selective and highly sensitive toward VOCs containing a 1,2-dichloro group at concentrations as low as 0.1 ppm. The results suggest the key interaction contributing to sensor response is a bidentate, metallocycle-like coordination of the 1,2-dichloro group to the cesium cations at the sensor surface.

Tuning the band-gap and enhancing the trichloroethylene photocatalytic degradation activities of flower-like Ni-doped SnS2/SnO2 heterostructures by partial oxidation

A hydrothermal procedure was used to synthesis flower-like 0–0.5 wt% Ni-doped SnS2, oxidation extent of which was tuned in air at 350 °C for various times. Photocatalysts were dip-coated on coiled wire-meshes including a light source for oxidation of 500 ppm trichloroethylene in air. FE-SEM revealed that the SnS2 flower-like structure integrity was preserved after partial oxidation, while surface areas were dramatically enhanced. XRD, HR-TEM, Raman, XPS and PL showed formation of fine crystalline nanoparticles and defects by oxidation and resulted in enhanced photocatalytic activity. Band gaps and defects recombination rate of heterostructures were tuned by partial oxidation and Ni doping. 43% oxidation of 0.34 wt% Ni-doped SnS2 results in increased surface area by 7.7 times to 100 m2/g, quenched electrons and holes recombination, increased the band gap, and showed the highest TCE conversion of 88%, while the photocatalyst with no oxidation showed no activity. Further addition of Ni declined the surface area and photocatalytic conversion.

A cataluminescence sensor for the detection of trichloroethylene based on PEG200/ZnO nanocomposite

The content of volatile organic compounds (VOCs) in the atmosphere will endanger the health and safety of human beings which makes it very important to develop a simple and rapid method for the determination of gas pollutants. Based on this, a new type of gas sensor was proposed for the detection of trichloroethylene in air. PEG200/ZnO nanocomposite were prepared by hydrothermal method. The materials were characterized by scanning electron microscope, X-ray energy spectrum and fourier infrared spectrum. The high selectivity of the materials was verified by using the cataluminescence (CTL) intensity of 9 kinds of VOCs on the surface of the materials as a reference. The results show that trichloroethylene can produce CTL response on the surface of PEG200/ZnO nanocomposite. Temperature, air flow rate and detector concentration all have certain effects on the CTL intensity. By comparing the CTL intensity under different reaction conditions, it is found that the suitable temperature and air flow rate are 120 °C, 180 mL/min and there is a good linear relationship between the relative CTL intensity and the concentration of the detected substance (y = 28.588 x - 285.56, R=0.9593). The gas sensor has the advantage of rapid response, and trichloroethylene can produce the maximum CTL on the surface of the material within 3 ~ 5 s.

Gas Sensing Properties and in Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy Study of Trichloroethylene Adsorption and Reactions on SnO2/RGO Films

The detection of trichloroethylene has attracted much attention because trichloroethylene has an important effect on human health. The sensitivity of the SnO2/RGO gas sensor arrays to 200 ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated in 250−350℃ by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2/RGO films. Dichloroacetyl chloride (DCAC), single chloroacetic acid salt(CH2ClCOO-), COCl2, HCl, H2O, CO and CO2 surface species are formed during trichloroethylene adsorption at 250−350°C. A possible mechanism of the reaction process is discussed.

Highly active Fe2O3-doped TiO2 photocatalyst for degradation of trichloroethylene in air under UV and visible light irradiation: Experimental and computational studies

0.0–5.0wt% Fe2O3-doped TiO2 photocatalysts were synthesized by an ultrasonic-assisted co-precipitation method and used for degradation of 500ppm trichloroethylene (TCE) in air. The photocatalysts were treated at 100–400°C and characterized by high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), BET surface area, and Raman, UV–vis, and photoluminescence (PL) spectroscopies. For the samples treated at 100°C, XRD patterns show no significant peaks, while HRTEM micrographs indicate crystalline structures and diffraction patterns and Raman spectra reveal wide and weak peaks of anatase TiO2. As 0.1wt% Fe2O3 is added to TiO2, the surface area increases by a factor of 1.87 and reach to 448m2/g. UV–vis analyses indicate that, as the Fe2O3 content of the samples increases, the band gap energies decrease from 3.22eV for the pure TiO2 to 2.60eV for 5.0wt% Fe2O3-doped TiO2. Density functional theory simulations show that, when Fe3+ is doped into or FeO, Fe2O3 or Fe4O6 is adsorbed on anatase TiO2, the bad gap reduces and the iron oxide–TiO2 show photocatalytic activity in visible light region. The synthesized TiO2 showed about two times higher photocatalytic activity for TCE removal than that of Degussa P25. Moreover, 0.1wt% Fe2O3-doped TiO2 sample dried at 100°C showed a maximum photocatalytic TCE conversion of about 97% with minor amounts of CO as a hazardous byproduct. As the treatment temperature of the samples increase, the photocatalytic activity declines. Significant photocatalytic degradation of TCE was also observed for the Fe2O3-doped TiO2 samples, under visible light irradiation.

Solid-phase microextraction fiber development for sampling and analysis of volatile organohalogen compounds in air.

A green, environmental friendly and sensitive method for determination of volatile organohalogen compounds was described in this paper. The method is based on a homemade sol–gel single-walled carbon nanotube/silica composite coated solid-phase microextraction to develop for sampling and analysis of Carbon tetrachloride, Benzotrichloride, Chloromethyl methyl ether and Trichloroethylene in air. Application of this method was investigated under different laboratory conditions. Predetermined concentrations of each analytes were prepared in a home-made standard chamber and the influences of experimental parameters such as temperature, humidity, extraction time, storage time, desorption temperature, desorption time and the sorbent performance were investigated. Under optimal conditions, the use of single-walled carbon nanotube/silica composite fiber showed good performance, high sensitive and fast sampling of volatile organohalogen compounds from air. For linearity test the regression correlation coefficient was more than 98% for analyte of interest and linear dynamic range for the proposed fiber and the applied Gas Chromatography-Flame Ionization Detector technique was from 1 to 100 ngmL−1. Method detection limits ranged between 0.09 to 0.2 ngmL−1 and method quantification limits were between 0.25 and 0.7 ngmL−1. Single-walled carbon nanotube/silica composite fiber was highly reproducible, relative standard deviations were between 4.3 to 11.7 percent.

Gas sensing properties and in situ diffuse reflectance infrared Fourier transform spectroscopy study of trichloroethylene adsorption and reactions on SnO2 films

The detection of trichloroethylene has attracted much attention because it has an important effect on human health. The sensitivity of the SnO2 flat-type coplanar gas sensor arrays to 100ppm trichloroethylene in air was investigated. The adsorption and surface reactions of trichloroethylene were investigated at 100–200°C by in-situ diffuse reflection Fourier transform infrared spectroscopy (DIRFTS) on SnO2 films. Molecularly adsorbed trichloroethylene, dichloroacetyl chloride (DCAC), phosgene, HCl, CO, H2O, CHCl3, Cl2 and CO2 surface species are formed during trichloroethylene adsorption at 100–200°C. A possible mechanism of the reaction process is discussed.

Deactivation of H-zeolites during catalytic oxidation of trichloroethylene

This paper reports the stability of protonic zeolites (H-ZSM-5, H-MOR and H-BEA) in the catalytic oxidation of trichloroethylene (TCE), focused on determining the causes of the deactivation. The study was conducted by relating the evolution of TCE conversion (with and without water vapor) with the physicochemical properties of the zeolites as a function of time on stream (TOS). The oxidation reactions were carried out in a fixed-bed reactor under 1000ppmv of TCE in air. We found out that both coke formation and chlorine attack were the causes of H-zeolites’ rapid deactivation. Coke was formed from the TCE or the surface intermediates already formed before the TCE oxidation slower step. Chlorine atoms of TCE also caused irreversible deactivation by attacking to Brönsted acid sites, which lead to structural changes. Under wet conditions, H-zeolites were strongly hydrated restoring hydroxyl groups to keep TCE conversion invariably overtime.

SiO2/TiO2 Antireflective Coatings With Photocatalytic Properties Prepared by Sol–Gel for Solar Glass Covers

The glass covers of solar systems are usually coated with antireflective (AR) coatings on both sides that allow to increase the efficiency of the whole system. At the same time, the accumulation of dust and dirt particles on the surface of the AR coated glass decreases the transmittance of the covers, even to values lower than the uncoated glass. This decrease in the cover transmittance reduces the solar radiation that reaches the absorber and, in this way, a decrease in the solar plant efficiency would be obtained. So, the use of films that combine high transmittance and self-cleaning capacity seems to be a promising development. This paper reports the preparation of sol–gel porous TiO2 and SiO2 bilayers on borosilicate glass. The porosity and thickness of both layers have been optimized in order to obtain the optimal photocatalytic and optical properties. Solar transmittance values of 0.964 were obtained for the TiO2/SiO2 coated glass. The highest value of transmittance reached is 0.993 and it is placed at 600 nm. The self-cleaning properties were evaluated using methylene blue and trichloroethylene (TCE) as model organic molecules using UV-A light. The results showed that the SiO2/TiO2 samples degraded the colorant faster than the SiO2 sample. Moreover, the degradation of TCE in air in a continuous fix bed photoreactor for samples with different TiO2 film thicknesses was also performed. The TCE conversion was found dependent on the TiO2 thickness. Nevertheless, the increase in the thickness of this layer reduced transmittance properties. The study demonstrates that it is possible to combine antireflective and self-cleaning properties in the same material.

Photocatalytic degradation of TCE in dry and wet air conditions with TiO2 porous thin films

Porous TiO2-anatase thin films were prepared by the sol–gel route and used for the study of the influence of structural properties in their photocatalytic activity. Sols were prepared by using titanium isopropoxide with two types of modifier ligands, namely acetic acid and acetyl acetone, and pore generating agents such as polyethylene glycol, pluronic F-127 and polyethylene glycol hexadecyl ether (Brij 58). The photocatalytic activity for the degradation of trichloroethylene in air was evaluated under ultraviolet irradiation at different gas flows and water vapour contents. The photocatalytic activity depends on the nature of the pore generating agent which influences the TiO2 crystallite size and the textural properties of the final material. The samples obtained by using acetic acid as the modifier ligand and either Brij 58 or PEG as the pore generating agent exhibited the best photocatalytic behaviour even in the presence of high quantities of water vapour. The direct trichloroethylene oxidation pathway to CO2 is favoured at low water vapour contents, but an important generation of COCl2 is observed even at low water partial pressures.

La-, Mn- and Fe-doped zirconia catalysts by sol–gel synthesis: TEM characterization, mass-transfer evaluation and kinetic determination in the catalytic combustion of trichloroethylene

Catalysts of pure zirconia and novel zirconia materials doped with combinations of La, Mn and Fe at 0.5 wt% of each metal were synthesized by a sol–gel method and characterized by transmission electron microscopy (TEM). The crystallite size was determined by the Scherrer equation from the main peak of the tetragonal phase of ZrO 2 observed in X-ray diffraction (XRD) patterns; the size thus determined coincided with the crystallite size observed in the TEM images. The structures were revealed to be porous and the dopant metals La, Mn and Fe were distributed on the surfaces of the zirconia crystallite with metal particle sizes ranging from a few to 13 nm. Different morphologies were adopted by the metal doping agents and caused different crystal aggregation modes in the doped samples during the xerogel annealing process. Agglomerates of the crystallites provided an average particle diameter of 23.67 μm for the catalyst loaded into the experimental reactor, resulting in low mass-transfer effects during the combustion of trichloroethylene in air. The mass-transfer effect was evaluated using the Yoshida correlation under the catalytic test of trichloroethylene combustion. A Langmuir–Hinshelwood model was proposed to describe the inhibition phenomenon seen in the reaction rate data for trichloroethylene combustion over the catalysts.

Kinetics rate model of the photocatalytic oxidation of trichloroethylene in air over TiO 2 thin films

The photocatalytic oxidation of trichloroethylene (TCE) over a TiO 2 thin film was investigated in a flow-through photocatalytic reactor. The effects of TCE concentration and water vapor concentration on the oxidation rates were investigated. Rate models based on variations of the Langmuir–Hinshelwood kinetic model were found to represent the results unsatisfactorily. Therefore, a general rate equation for the oxidation of TCE was derived from an elementary reaction mechanism of TCE photocatalytic oxidation over TiO 2. The model, based on chlorine atom attack of the TCE molecule, yields a relatively complex equation including the explicit dependence on water vapor concentration, TCE concentration, photon flux and quantum yield. The rate equation yields half-order dependence on the photon flux at high photon fluxes and first-order dependence at low photon fluxes and reduces to first-order dependence on TCE and inverse dependence on water vapor under specific conditions. The kinetic parameters of the photocatalytic oxidation of TCE on TiO 2 thin film were estimated by fitting the model to the experimental results. The approach demonstrated in this paper represents a more rational method of kinetic analysis than the mechanical adoption of a Langmuir–Hinshelwood type rate equation often reported in the literature.

Hybrid photocatalysts for the degradation of trichloroethylene in air

Hybrid photocatalysts based on an adsorbent SiMgOx and a photocatalyst TiO 2 were developed in a plate shape. The ceramic surface was coated with TiO 2 by the slip-casting technique. The effect of the support in the photocatalytic degradation of trichloroethylene (TCE) was analyzed by modifying TiO 2 loading and the layer thickness. Photocatalysts were characterised by N 2 adsorption–desorption, mercury intrusion porosimetry, SEM, UV–vis spectroscopy and XRD. A direct relationship between the TiO 2 content and the photocatalytic activity was observed up to three layers of TiO 2 (0.66 wt.%). Our results indicate that intermediate species generated on the TiO 2 layer can migrate through relatively long distances to react with the OH − surface groups of the support. By increasing the TiO 2 loading of the photocatalyst two effects were observed: trichloroethylene conversion is enhanced, while the efficiency of the oxidation process is decreased at expenses of increasing the selectivity to COCl 2 and dichloroacetylchloride (DCAC). The results are discussed in terms of the layer thickness, TiO 2 amount, TCE conversion and CO 2, and COCl 2 selectivity.

Hybrid Plasma-Catalyst System for the Removal of Trichloroethylene in Air

AbstractNon-thermal plasmas are innovative and promising tools with respect to end-of-pipe treatment of waste gases. Among other features, they allow decomposition of low concentrations of volatile organic compounds in air streams at atmospheric pressure. In this paper, a plasma-catalytic hybrid system for the removal of trichloroethylene (TCE) in dry air is discussed. A pin-to-mesh electrode concept is used to obtain a positive corona discharge. A packed bed of TiO

Reconstructing population exposures from dose biomarkers: inhalation of trichloroethylene (TCE) as a case study.

Physiologically based pharmacokinetic (PBPK) modeling is a well-established toxicological tool designed to relate exposure to a target tissue dose. The emergence of federal and state programs for environmental health tracking and the availability of exposure monitoring through biomarkers creates the opportunity to apply PBPK models to estimate exposures to environmental contaminants from urine, blood, and tissue samples. However, reconstructing exposures for large populations is complicated by often having too few biomarker samples, large uncertainties about exposures, and large interindividual variability. In this paper, we use an illustrative case study to identify some of these difficulties, and for a process for confronting them by reconstructing population-scale exposures using Bayesian inference. The application consists of interpreting biomarker data from eight adult males with controlled exposures to trichloroethylene (TCE) as if the biomarkers were random samples from a large population with unknown exposure conditions. The TCE concentrations in blood from the individuals fell into two distinctly different groups even though the individuals were simultaneously in a single exposure chamber. We successfully reconstructed the exposure scenarios for both subgroups - although the reconstruction of one subgroup is different than what is believed to be the true experimental conditions. We were however unable to predict with high certainty the concentration of TCE in air.

Kinetics of the Catalytic Oxidation of Lean Trichloroethylene in Air over Pd/Alumina

Kinetic modeling of the catalytic oxidation of trichloroethylene (TCE) over a palladium supported on alumina was evaluated. On the basis of previous studies on the effect of temperature, inlet TCE and oxygen concentrations, and the space velocity on the reaction rate, a five-step reaction network scheme, based on an Eley−Rideal-type mechanism, provided an accurate correlation of the experimental data, determined by a nonlinear least-squares regression.

Effect of Water and Oxygen Contents on the Decomposition of Gaseous Trichloroethylene in Air under Electron Beam Irradiation

Abstract An electron beam (EB) treatment of gaseous trichloroethylene (TCE) in air was studied as a purification method of off-gases containing gaseous chloroethylenes. The model air containing TCE at input concentrations of 5–75 ppmv, detected mostly in actual off-gases, was irradiated with 1-MeV EBs in a gas-flow vessel at 10 L/min under the conditions of atmospheric pressure, 298 K, and different H2O contents. The decomposition of 75 ppmv TCE was also examined in humid air under different O2 contents of 1 × 103–2.1 × 105 ppmv. In the existence of H2O and O2 contents with ≥ 3 × 102 ppmv and ≥ 5 × 103 ppmv, respectively, the decomposition ratios of TCE were enhanced and TCE was decomposed into 83.0 ± 1.5% of dichloroacetyl chloride (DCAC) and 17.5 ± 0.6% of carbonyl chloride (COCl2) independently of the input TCE concentrations based on the carbon balance. Trichloroethylene of 5–75 ppmv was effectively decomposed by the OH radical through Cl-radical chain oxidation under the above-mentioned air conditions.

Ru-Promoted CrOx/Al2O3 Catalyst for the Low-Temperature Oxidative Decomposition of Trichloroethylene in Air

A series of Ru-promoted CrOx/Al2O3 as catalysts for the low-temperature oxidative decomposition of trichloroethylene (TCE) were characterized and evaluated in comparison with an unpromoted CrOx/Al2O3 catalyst. Catalyst characterization was conducted by surface area measurement, X-ray diffraction and X-ray photoelectron spectroscopy. Catalyst performance in the TCE decomposition reaction was evaluated with respect to the initial catalytic activity, the rate of catalyst deactivation, and the product concentrations of CO and Cl2 under dry or wet air conditions. The presence of a small amount of Ru, as much as 0.4 wt% in a CrOx/Al2O3 catalyst, brought about several beneficial effects on the catalytic reaction performance. As compared with the unpromoted CrOx/Al2O3, this Ru-promoted CrOx/Al2O3 catalyst showed enhanced catalytic activity (249 versus 264 °C in terms of temperature at which 50% of TCE conversion occurred), a reduced concentration of CO (180 versus 325 ppm) in the product, and a decreased propensity to deactivation. Performance improvements of the Ru-promoted CrOx/Al2O3 catalyst were thought to originate from its enhanced oxidation activity due to the coexisting highly-dispersed Ru oxides rendering less active Cr(III) to more active Cr(VI), and facilitating the process of supplying activated oxygen for the reaction system.

Decomposition of Trichloroethylene by Microwave‐Induced Plasma Generated from SiC Whiskers

Microwave‐induced plasma discharge behavior of β‐SiC whiskers prepared by thermal decomposition of a sulfur containing silicon oil has been investigated in different surrounding gases. The undoped whiskers prepared in this study were white and woolly, and exhibited amazingly high electrical conductivity of 102 to , comparable to that of carbon fibers. The undoped whiskers were brought to a red heat and emitted a strong light upon microwave irradiation in an air environment and even in flowing air at 1.01 × 105 Pa. Spectral analysis of the light has revealed the generation of nitrogen plasma in addition to heat radiation. In contrast, a long and narrow streak of strong bluish white light was generated from the whiskers upon microwave irradiation in flowing argon at 1.01 × 105 Pa, and was confirmed as an Ar plasma based on the 4s‐4p electron transition of Ar atoms. It was found that the plasma streak was stable even in an atmosphere of flowing argon containing a small amount of trichloroethylene, oxygen, and water vapor. Generation of such a microwave‐induced plasma discharge in air and an Ar plasma streak were unique phenomena with β‐SiC whiskers and carbon fibers exhibiting high electrical conductivity. Decomposition of trichloroethylene in air by the plasma discharge was less effective than thermal decomposition from the standpoint of conversion of trichloroethylene and the amounts of partial decomposition products. However, trichloroethylene could be completely decomposed by the Ar plasma streak with low energy consumption, demonstrating the potential advantage of a microwave‐induced Ar plasma streak to decompose toxic halogenated hydrocarbons.

Trichloroethylene Cancer Risk: Simplified Calculation of PBPK-Based MCLs for Cytotoxic End Points

Cancer risk assessments for trichloroethylene (TCE) based on linear extrapolation from bioassay results are questionable in light of new data on TCE's likely mechanism of action involving induced cytotoxicity, for which a threshold-type dose–response model may be more appropriate. Previous studies have shown that if a genotoxic mechanism for TCE is assumed, algebraic methods can considerably simplify the use of physiologically based pharmacokinetic (PBPK) models to estimate virtually safe environmental concentrations for humans based on rodent cancer-bioassay data. We show here how such methods can be extended to the case in which TCE is assumed to induce cancer via cytotoxicity, to estimate environmentally safe concentrations based on rodent toxicity data. These methods can be substituted for the numerical methods typically used to calculate PBPK-effective doses when these are defined as peak concentrations. We selected liver and kidney as plausible target tissues, based on an analysis of rodent TCE-bioassay data and on a review of related data bearing on mechanism. Tumor patterns in rodent bioassays are shown to be consistent with our estimates of PBPK-based, effective cytotoxic doses to mice and rats used in these studies. When used with a margin of exposure of 1000, our method yielded maximum concentration levels for TCE of 16 ppb (87 μg/m3) for TCE in air respired 24 hr/day, 700 ppb (3.8 mg/m3) for TCE in air respired for relatively brief daily periods (e.g., 0.5 hr while showering/bathing), and 210 μg/liter for TCE in drinking water assuming a daily 2-liter ingestion. Cytotoxic effective doses were also estimated for occupational respiratory exposures. These estimates indicate that the current OSHA permissible exposure limit for TCE would produce metabolite concentrations that exceed anacuteno observed adverse effect level for hepatotoxicity in mice. On this basis, the OSHA TCE limit is not expected to be protective.