Sorption Of Trichloroethylene Research Articles

Microplastic inhibits the sorption of trichloroethylene on modified biochar.

Biochar (BC) was used to remove trichloroethylene (TCE) from soil and water phases, and BC modification changed the sorption behavior of pollutants. Microplastics are emerging pollutants in the soil and water phases. Whether microplastics can affect the sorption of TCE by modified BC is not clear. Thus, batch sorption kinetics and isotherm experiments were conducted to elucidate the sorption of TCE on BC, and BC combined with polyethylene (PE) or polystyrene (PS). The results showed that HCl and NaOH modification increased TCE sorption on BC, while HNO3 modification inhibited TCE sorption on BC. When PE/PS and BC coexisted, the TCE sorption capacity decreased significantly on BC-CK + PE, BC-HCl + PE, BC-HNO3 + PE, BC-NaOH + PE, and BC-NaOH + PS, which was likely due to the preferential sorption of PE/PS on BC samples. We concluded that microplastics can change TCE sorption behavior and inhibit TCE sorption on BC samples. Thus, the interaction of BC and microplastics should be considered when BC is used for TCE removal in soil and water remediation.

A novel nZVI–bentonite nanocomposite to remove trichloroethene (TCE) from solution

Nanoscale zero-valent iron (nZVI) based (nano)composites supported by clay mineral substrates are a promising technology for the in-situ remediation of groundwater and (sub)soils contaminated with chlorinated hydrocarbons, such as trichloroethene (TCE). However, the physicochemical processes and interaction mechanisms between nZVI particles, clay minerals and TCE are poorly understood, yet. We immobilized nZVI particles on a commercial bentonite substrate to prepare a novel nZVI-B nanocomposite and tested its performance for TCE removal from solution against pure nZVI in batch reactors. The nZVI-B exhibited a higher reactivity (2.2·10−3 L h−1·m−2) and efficiency (94%) for TCE removal than nZVI (2.2·10−4 L h−1·m−2; 45%). Sorption of TCE onto the clay surfaces and reductive de-chlorination in “micro-reactors” developing within the nZVI-B controlled the kinetics and the magnitude of TCE loss from solution. Contrary to pure nZVI, no signs of nZVI particle agglomeration or inactivation due to oxide shell formation were found in nZVI-B. We attribute this to the uptake of dissolved Fe species that are liberated via progressing nZVI particle corrosion by the bentonite substrate to form Fe-smectite (nontronite domains), which prevented from a deterioration of the properties and reactivity of the nZVI-B. The use of nZVI-B in permeable reactive barriers at contaminated field sites could be feasible, where a system-inherent reduction of the soil-bearing capacity has to be minimized.

Poplar wood and tea biochars for trichloroethylene remediation in pure water and contaminated groundwater

Four biochars from pyrolysis of poplar wood (biochar P) and tea (biochar T) at 450 and 750 °C have been tested in a first time as adsorbents for trichloroethylene (TCE) removal in groundwater. The physico-chemical properties of biochars were systematically investigated with organic elemental analyser, scanning electron microscopy, N2 adsorption measurement, IR spectroscopy and X-ray photoelectron microscopy. Three kinetic models were used to follow the TCE removal by biochars. The best kinetic performances were obtained with biochars P with the smallest particle size diameter (50 – 100 µm) due to their porosity and the mass transfer limitation for the TCE remediation. Remediation of a real sample of groundwater polluted by chlorinated organic compounds showed that biochar P produced at 750 °C is more efficient to remove vinyl chloride (65% adsorbed) than commercial activated carbon powder (40%). The TCE sorption capacity is similar in pure water and in polluted groundwater. The results also highlighted better retention capacity for the most substituted molecules (tri and tetrachloroethylene) for biochar P750.

Biochar catalyzed dechlorination – Which biochar properties matter?

Bone char catalyzed dechlorination of trichloroethylene (TCE) by green rust (iron(II)-iron(III) hydroxide, GR) has introduced a promising new reaction platform for degradation of chlorinated solvents. This study aimed to reveal whether a broader class of biochars are catalytically active for the dechlorination reaction and to identify which biochar properties are the most important for the catalytic activity. Biochars produced by pyrolysis of animal, plant, and sewage waste substrates at 950 °C were prepared for catalytic dechlorination of TCE by GR tested in batch experiments with 0.15 g L−1 biochar, 3.2 g L−1 GR, and ~ 20 µM TCE. The results showed that the biochar substrate significantly affects its catalytic activity, with the highest TCE reduction rate observed for bone and shrimp-based biochars (k ≥ 0.18 h−1), whereas no reactivity was seen for graphite and activated carbon references. Multivariate regression indicated that the biochar catalytic activity is controlled by multiple biochar properties - biochar surface area, TCE sorption, abundance of C–O groups, and pore size are the properties that impact the catalytic activity most. Derivation of biochar reactivity relationship for a broad spectrum of biochars provides a new approach for identifying proper biochar catalysts for pollutant degradation.

The effects of temperature and relative humidity on trichloroethylene sorption capacities of building materials under conditions relevant to vapor intrusion

In this research, the sorption capacities of trichloroethylene (TCE) vapors were investigated at ppbv concentrations on building materials in the temperature range from 283.15 K to 303.15 K and at relative humidity levels of 50% and 85%. These are conditions that are relevant to vapor intrusion investigations. Such interactions of TCE with different materials at different temperatures/ relative humidity have been studied to a very limited extent, and not yet at all at the extremely low concentration ranges in vapor intrusion scenarios. The sorption capacities of the building materials decrease as temperature increases. The isotherms are for the most part linear, indicating that the adsorption process takes place in the Henry’s Law regime, except for cinderblock. The isosteric heats of adsorption have been calculated. The sorption capacities of glass wool and nylon carpet increased slightly when the relative humidity increased from 0% to 85% whereas the sorption capacities of printer paper, drywall, and cinderblock decreased significantly at elevated humidity levels. The influence of humidity is complicated since under certain conditions it may enhance sorption or inhibit sorption. The sorption capacities of the studied materials are in a range indicating the possibility of these processes should not be overlooked during vapor intrusion investigations.

Sorption of trichloroethylene under dynamic conditions

The solution to the problem of obtaining water that is safe against organohalogen pollutants, including trichloroethylene, can be the use of adsorption purification methods. For engineering calculations of the treatment plant, adsorption constants, kinetic parameters and dynamic characteristics of the adsorption process are required. It is advisable, at the stage of technology development, to optimize the parameters and modes of the sorption columns using mathematical modeling based on equations of external diffusion dynamics of adsorption.

Two-Stage Ozonation – Adsorption Purification of Ground Water from Trichloroethylene and Tetrachloroethylene with Application of Commercial Carbon Adsorbents

ABSTRACT The aim of the research is to choose the most efficient adsorbent for two-stage ozone-sorption purification of groundwater containing both trichloroethylene (TCE) and tetrachloroethylene (PCE) between three carbon sorbents produced in Russia (AUT-M, CAUSORB-221, and AG-3). Sorption isotherms of TCE and PCE on AUT-M and CAUSORB-221 at 296 K were fitted by the Freundlich equation. The better TCE and PCE sorption ability of AUT-M in comparison with CAUSORB – 221 and AG-3 was demonstrated. The optimum parameters for ozonation and sorption stages of groundwater purification from TCE and PCE are elucidated using laboratory and pilot-plant scales. Prolonged test of this technology for purification of ground demonstrated that the higher achievable efficiency of destruction with ozone is 94% for TCE and 38% for PCE. Ozonation-sorption treatment of groundwater allows one to achieve TCE and PCE removal efficiency of 96-97% and 92-94% correspondingly. The most efficient carbon sorbent is microporous carbon fiber AUT-M. Using this sorbent, TCE and PCE concentrations in treated water decrease below the MPC level (5 μg/L) adopted in Russia. It is concluded that the combination of ozonation with sorption of residual contaminants by carbon sorbents is a promising way for the purification of waters containing chlorinated contaminants.

Bone Char Mediated Dechlorination of Trichloroethylene by Green Rust.

Biochars function as electron transfer mediators and thus catalyze redox transformations of environmental pollutants. A previous study has shown that bone char (BC) has high catalytic activity for reduction of chlorinated ethylenes using layered Fe(II)-Fe(III) hydroxide (green rust) as reductant. In the present study, we studied the rate of trichloroethylene (TCE) reduction by green rust in the presence of BCs obtained at pyrolysis temperatures (PTs) from 450 to 1050 °C. The reactivity increased with PT, yielding a maximum pseudo-first-order rate constant (k) of 2.0 h-1 in the presence of BC pyrolyzed at 950 °C, while no reaction was seen for BC pyrolyzed at 450 °C. TCE sorption, specific surface area, extent of graphitization, carbon content, and aromaticity of the BCs also increased with PT. The electron-accepting capacity (EAC) of BC peaked at PT of 850 °C, and EAC was linearly correlated with the sum of concentrations of quinoid, quaternary N, and pyridine-N-oxide groups measured by XPS. Moreover, no TCE reduction was seen with graphene nanoparticles and graphitized carbon black, which have high degrees of graphitization but low EAC values. Further analyses showed that TCE reduction rates are well correlated with the EAC and the C/H ratio (proxy of electrical conductivity) of the BCs, strongly indicating that both electron-accepting functional groups and electron-conducting domains are crucial for the BC catalytic reactivity. The present study delineates conditions for designing redox-reactive biochars to be used for remediation of sites contaminated with chlorinated solvents.

Effect of water leaching on biochar properties and its impact on organic contaminant sorption.

When biochar (BC) is applied to soil, one process that can alter its properties and contaminant sorption is the leaching of minerals and dissolved organic carbon (DOC). This study investigated changes in properties of three BCs (cattle manure, grain husk, and wood chips), due to leaching, and the subsequent impact on sorption of trichloroethylene (TCE) and tetrachloroethylene (PCE). The manure-derived BC released 27.4 mg g-1 DOC, which isover ten times more than that measured for the two plant-based BCs (2.5 and 1.5 mg g-1 DOC for grain husk and wood chips, respectively). In all leachates, potassium is the dominant cation, whereas chloride, sulfate, and phosphate are the main anions. In total, the manure-derived biochar released the highest sum of total ions (73.1 mg g-1), followed by BC produced from grain husk (15.5 mg g-1) and wood chips (1.2 mg g-1). Leaching increased external surface area, mesopore volume, and hydrophobicity of the manure-derived BC and decreased its polarity. This enhanced sorption via partitioning. In plant-based BCs, micropore volume and size distribution were altered, most likely through the un-blocking of pores, causing increased sorption via pore-filling for both TCE and PCE. The results indicate that, depending on feedstock material, BC leaching can alter the environmental fate of organic compounds.

Removal of trichloroethylene by biochar supported nanoscale zero-valent iron in aqueous solution

Abstract Nanoscale zero-valent iron (NZVI) has been widely used for the degradation of trichloroethylene (TCE) in contaminated water, however, it is suffering from being easy to aggregate and having low adsorption capacity for TCE. In order to overcome the shortcomings of NZVI, modified NZVI particles with biochar (NZVI/BC) were applied in this study for removal and degradation of TCE, given the high stability and adsorption capacity of BC. The effects of pyrolysis temperature of BC, mass ratio of NZVI/BC and solution pH on the removal and degradation efficiency of TCE were studied. The different pyrolysis temperatures of BC resulted in the differences on the surface areas, aromaticity and noncarbonized fractions, which determined the sorption capacity of TCE. Compared with pure NZVI, the NZVI/BC at different mass ratios could increase the removal efficiency of TCE to 99%, which was attributed to the higher adsorption capacity of BC for TCE. Besides, the yield of final products (ethane, ethylene and acetylene) differed at different mass ratios of NZVI/BC. Generally, the main product was ethylene in all reactions and the yield of acetylene and ethane were relatively low. Solution pH had little effect on the total removal of TCE but significantly influenced the yield of final products. The yield of ethylene decreased with the increasing pH. The results indicate that solution pH could not affect the sorption of TCE but influenced the degradation rate of TCE by NZVI/BC.

Concept model of the formation process of humic acid–kaolin complexes deduced by trichloroethylene sorption experiments and various characterizations

To explore the interactions between soil organic matter and minerals, humic acid (HA, as organic matter), kaolin (as a mineral component) and Ca2+ (as metal ions) were used to prepare HA-kaolin and Ca-HA-kaolin complexes. These complexes were used in trichloroethylene (TCE) sorption experiments and various characterizations. Interactions between HA and kaolin during the formation of their complexes were confirmed by the obvious differences between the Qe (experimental sorbed TCE) and Qe_p (predicted sorbed TCE) values of all detected samples. The partition coefficient kd obtained for the different samples indicated that both the organic content (fom) and Ca2+ could significantly impact the interactions. Based on experimental results and various characterizations, a concept model was developed. In the absence of Ca2+, HA molecules first patched onto charged sites of kaolin surfaces, filling the pores. Subsequently, as the HA content increased and the first HA layer reached saturation, an outer layer of HA began to form, compressing the inner HA layer. As HA loading continued, the second layer reached saturation, such that an outer-third layer began to form, compressing the inner layers. In the presence of Ca2+, which not only can promote kaolin self-aggregation but can also boost HA attachment to kaolin, HA molecules were first surrounded by kaolin. Subsequently, first and second layers formed (with inner layer compression) via the same process as described above in the absence of Ca2+, except that the second layer continued to load rather than reach saturation, within the investigated conditions, because of enhanced HA aggregation caused by Ca2+.

Ozone-adsorption Method of TRIC and PERC Elimination from Underground Water Corresponding to the Russian Maximum Permissible Concentration Standards

ABSTRACTIn this research, the ozonation–sorption technology for water purification to remove trichloroethylene and tetrachloroethylene is presented. Physical and chemical (kinetic) parameters of consecutive ozonation and sorption of trichloroethylene and tetrachloroethylene from water are determined. The optimum technological parameters of this method for the purification of water from trichloroethylene and tetrachloroethylene are developed. R&D were carried out using water from 12 underground wells nearby Podolsk, Moscow region (Russia).

Influence of soil properties on vapor-phase sorption of trichloroethylene

Current practices in health risk assessment from vapor intrusion (VI) using mathematical models are based on assumptions that the subsurface sorption equilibrium is attained. The time required for sorption to reach near-steady-state conditions at sites may take months or years to achieve. This study investigated the vapor phase attenuation of trichloroethylene (TCE) in five soils varying widely in clay and organic matter content using repacked columns. The primary indicators of TCE sorption were vapor retardation rate (Rt), the time required for the TCE vapor to pass through the soil column, and specific volume of retention (VR), and total volume of TCE retained in soil. Results show TCE vapor retardation is mainly due to the rapid partitioning of the compound to SOM. However, the specific volume of retention of clayey soils with secondary mineral particles was higher. Linear regression analyses of the SOM and clay fraction with VR show that a unit increase in clay fraction results in higher sorption of TCE (VR) than the SOM. However, partitioning of TCE vapor was not consistent with the samples' surface areas but was mainly a function of the type of secondary minerals present in soils.

Identification of TCE and PCE sorption and biodegradation parameters in a sandy aquifer for fate and transport modelling: batch and column studies.

The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, K d = 0.0016; PCE, soil 1, K d = 0.0051; PCE, soil 2, K d = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, K f = 0.6493 and S max = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ13C values within the range of −23.6 ÷ −24.3 ‰ and −26.3 ÷−27.7 ‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.

Mechanism insights into enhanced trichloroethylene removal using xanthan gum-modified microscale zero-valent iron particles

This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe2+ concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the in-situ remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity.

Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system

This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc=0.046–0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46–0.58. Kerogen+black carbon was the dominant CM fraction extracted from the sediments and accounted for >60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State.A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that >80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration <1000μgL−1. These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM.

Detection of TCE Using Electrochemical Testing: Analyzing the Purity of Water

Trichloroethylene (TCE) can be considered as one of the most dangerous and toxic organic pollutants. It is present in the groundwater with concentration as high as few ppm, as reported by the Environmental Protection Agency in USA. [1,2] Zero-Valent Iron sorbents are effective at removing TCE from water, but are too expensive to use for large quantity. One promising area of fly ash (FA) is its use as a sorbent, particularly to remove pollutants from water and wastewater in industry. However, raw fly ash has a relatively low surface area and is hydrophilic, hence in its raw form it is not efficient absorbent and easily mixes with water. In this study, we set out to modify the fly ash into a zeolitic fly ash (ZFA) with high surface area (404 m2.g-1) by alkali fusion followed by hydrothermal treatment. The resulting zeolite material is subjected to hydrophobic surface treatments to produce a material that adsorbs organic components like TCE, and repels water. The concentration of TCE was measured by using simple characterization techniques such as UV-Vis spectroscopy and chronoamperometry measurements. TCE exhibits absorption maxima at 260 nm which was used to calibrate the concentration. The chronoamperometry measurements were done using stainless steel as working electrode. The TCE sorption capacity of the zeolitic fly ash is improved by the chemical modification and it was about three times higher than the as-received fly ash as shown in figure 1.

Photocatalytic degradation of trichloroethylene in aqueous phase using nano-ZNO/Laponite composites

The feasibility of nano-ZnO/Laponite composites (NZLc) as a valid alternative to TiO2 to mineralize trichloroethylene (TCE) without difficulties for recovery of photocatalysts was evaluated. Based on the experimental observations, the removal of TCE using NZLc under UV irradiation was multiple reaction processes (i.e., sorption, photolysis, and photocatalysis). Sorption of TCE was thermodynamically favorable due to the hydrophobic partitioning into crosslinked poly vinyl alcohol, and the adsorption onto high-surface-area mineral surfaces of both ZnO and Laponite. The degradation efficiency of TCE can be significantly improved using NZLc under UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. However, the degradation efficiency was found to vary with experimental conditions (e.g., initial concentration of TCE, loading amount of NZLc, the intensity of light and initial solution pH). Although the removal of TCE by NZLc was found to be a complex function of sorption, photolysis, and photocatalysis, the photocatalytic degradation of TCE on the surface of ZnO was critical. Consequently, developed NZLc can be applied as a valid alternative to suspended TiO2 powder, and overcome drawbacks (e.g., filtration and recovery of photocatalysts) in degradation of TCE for various water resources.

Influence of temperature and macromolecular mobility on sorption of TCE on humic acid coated mineral surfaces

This study demonstrates differences in sorptive capacity of volatile organic compound (VOC) trichloroethylene (TCE) onto natural organic matter (NOM) coated and uncoated mineral surfaces above and below the NOM glass transition temperature. TCE sorption isotherms for dry NOM-mineral systems below the NOM glass transition temperature (Tg) demonstrated sorption behavior characteristic of micropore filling, with sorption capacities reduced relative to uncoated mineral matrices. Such differences were not entirely associated with differences in surface areas of the coated and uncoated mineral matrices, but were likely associated with either a blockage of pore space available to the VOC or a kinetic limitation that does not allow the VOC access to the internal porosity of the model soil within the time periods of the experiment. TCE sorption in dry NOM-mineral matrices above the Tg, however, was described in terms of sorption within a more fluid, macromolecular dissolution medium that does not hinder access to mineral surfaces. Such observations have potential important implications for modeling the fate and transport of VOCs in soils and sediment systems.

Mechanistic Investigation of Non-Ideal Sorption Behavior in Natural Organic Matter. 1. Vapor Phase Equilibrium

Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment.