Thermal Desorption Temperature Research Articles

Thermal Desorption Temperature Affects Water Retention and Hydraulic Conductivity of Three Contrasting Soils

ABSTRACT Thermal desorption is an effective approach to removing petroleum hydrocarbons from soil. However, the resultant environmental function and revegetation potential of the soil can be reduced by high temperatures. This study evaluated the effect of nine temperatures of heating (60–800°C) on water retention and hydraulic conductivity in three soils of contrasting mineral and physical properties. Fredlund-Xing water release curves were developed using the HYPROP system. Features of the release curves were compared for differences: the water content (%Vol) at which air first enters the macropore volume (AEV), the slope of the rapid desorption portion of the curve, field capacity, and the residual water content. A Hearne sandy loam showed an increase in the %Vol at saturation (0.354 to 0.557 cm3 H2O cm−3 soil), but a decrease in plant available water with increasing temperature. A Rader sand showed a decrease in field capacity and plant available water. A Weswood clay showed no change in field capacity, but an increase in plant available water 10.87 to 18.39 cm3 H2O cm−3 soil through 700°C. Saturated hydraulic conductivity (Ksat) increased for both the Hearne and the Weswood soils with increasing temperature. However, the Rader soil Ksat saw an increase from 0.002 to 0.007 cm s−1 to 450°C but declined to <0.0005 cm s−1 between 500°C and 800°C. This study shows the release curve comparison approach can be effective to quantify changes or differences in soil water relationships by treatment or soil property. Additional insight is provided by electron microscope imaging.

Influence of surface structure on D retention and erosion behaviours of RAFM steel with D-plasma exposure

As the first wall candidate material in the future fusion device, Reduced Activation Ferritic/Martensitic (RAFM) steel represented by CLF-1 steel was further investigated on the deuterium (D) erosion and retention behaviours. The influences of the surface conditions, including surface morphology, W-enriched structure and the original surface roughness, of the surface conditions including the sample temperature, W-enriched structure and the original surface roughness are mainly discussed. The results showed that with the increase of the sample temperature of CLF-1 steel during D-plasma exposure, the surface morphology changed obviously, and the grooves/pits formed by the erosion on the sample surface are deepened and the boundary becomes obvious. Then, the granular nanostructures appeared at the erosion edges and covered the grooves, eventually forming the nanoclusters structure on the surface. At the same time, TEM results showed that the thickness and content of W atoms on the surface increased. Under the combined action of the above surface conditions, both the sputtering rate and total D retention amount of CLF-1 steel decrease. Under the current experimental parameters, with the increase of the initial surface roughness, the sputtering morphology and the surface roughness of CLF-1 steel changed to different degrees after erosion of D, which eventually led to the slightly increase of the sputtering rate. The effect of incident D-plasma angle on the sputtering and redeposition behaviour of the material may explain this phenomenon. Besides, both the specific surface area of the contact plasma and the erosion behaviour of the material by D-plasma increased with the original surface roughness. The D releasing peak, thermal desorption temperature and total D retention amount of CLF-1 steel samples decrease with the original roughness of CLF-1 steel, which is mainly caused by the increase of D diffusion on the surface. At present, it can be found that the W-enriched surface behaviour induced by D-plasma exposure as well as the change of roughness and morphology lead to the decrease of the sputtering rate of RAFM steel with fluence, energy and sample temperature.

Ammonia snow lines and ammonium salts desorption

Context. The nitrogen reservoir in planetary systems is a long-standing problem. Some of the N-bearing molecules are probably incorporated into the ice bulk during the cold phases of the stellar evolution, and may be gradually released into the gas phase when the ice is heated, for example in active comets. The chemical nature of the N-reservoir should greatly influence how, when, and in what form N returns to the gas phase, or is incorporated into the refractory material forming planetary bodies. Aims. We present the study of the thermal desorption of two ammonium salts, ammonium formate and ammonium acetate, from a gold surface and from a water ice substrate. Methods. Temperature-programmed desorption experiments and Fourier transform infrared reflection spectroscopy were conducted to investigate the desorption behavior of ammonium salts. Results. Ammonium salts are semi-volatile species releasing neutral species as major components upon desorption, namely ammonia and the corresponding organic acid (HCOOH and CH3COOH), at temperatures higher than the temperature of thermal desorption of water ice. Their desorption follows a first-order Wigner-Polanyi law. We find the first-order kinetic parameters A = 7.7 ± 0.6 × 1015 s−1 and Ebind = 68.9 ± 0.1 kJ mol−1 for ammonium formate and A = 3.0 ± 0.4 × 1020 s−1 and Ebind = 83.0 ± 0.2 kJ mol−1 for ammonium acetate. The presence of a water ice substrate does not influence the desorption kinetics. Ammonia molecules locked in salts desorb as neutral molecules at temperatures much higher than previously expected, and that are usually attributed to refractory materials. Conclusions. The ammonia snow line has a smaller radius than the water snow line. As a result, the NH3/H2O ratio content in Solar System bodies can be a hint to where they formed and subsequently migrated.

Application of thermal desorption for measuring PAHs on PM2.5.

PM2.5 and polycyclic aromatic hydrocarbons (PAHs) emitted from various sources may cause respiratory disease and lung cancer. Additionally, PAHs deposited on PM2.5 would aggravate the hazard to human health once inhaled. Therefore, it is essential to investigate the PAHs adsorbed on PM2.5 in ambient air. However, analysis of PAHs on PM2.5 is limited so far due to high detection limit of the analytical method and complex pretreatment procedures of the sample. In this study, thermal desorption (TD) is combined with GC-HRMS for direct analysis of PAHs on PM2.5 collected by the filter without pretreatment. The results indicate that distribution of PAHs on the filter is uniform and each filter section is representative for direct analysis of PAHs on PM2.5. The optimal thermal desorption temperature and purge time of analysis are found at 320°C and 60 s, respectively. Furthermore, the PAHs on PM2.5 of ambient air in Taiwan including traffic area, industrial area, suburban area, and background site are investigated. The results indicate that the concentrations of PAHs on PM2.5 in ambient air of Northern, Central, and Eastern Taiwan are in the range of 0.13-6.63 ng/m3, with an average concentration of 2.23 ng/m3. The PAH concentration measured in winter is significantly higher than that in summer, and the concentration of PAHs on PM2.5 ranges from 0.071 to 0.280 ng/μg while the average concentration is 0.133 ng/μg. The technology optimized in this study can be applied for rapid and accurate measurement of PAHs present on fine particles.

Numerical studies of CO separation and enrichment from blast furnace gas by using a CuCl/Y fixed bed

ABSTRACT Emission amount of blast furnace gas (BFG) is huge per year and it cannot be directly combusted due to its low heat value. Separating and Enriching CO from blast furnace gas provides an effective way for its utilization. This paper proposes an improved adsorption isotherm model of CO on CuCl/Y adsorbent. A CO/CO2/N2 multi-component adsorption equilibrium model and a set of mathematical models for CO separation and enrichment from BFG by using a fixed bed are established. Detailed characteristics of CO/CO2/N2 adsorption/desorption during Vacuum pressure swing adsorption (VPSA) process are revealed. Effects of adsorption/desorption pressure, cycle time, flow rate, purge operation, and thermal desorption temperature on CO separation and enrichment are further investigated. Optimized operation parameters are provided based on energy consumption analysis. For the purpose of purity >55% and lower energy consumption, conditions of <300 kPa adsorption pressure, 5–20 kPa desorption pressure, and 343–363 K desorption temperature are recommended.

Bio-monitoring of non-metabolized BTEX compounds in urine by dynamic headspace-needle trap device packed with 3D Ni/Co-BTC bimetallic metal-organic framework as an efficient absorbent

In this work we try to develop a new analytical procedure for extraction and analysis of the Benzene, Toluene, Ethylbenzene and Xylene isomer compounds in the urine samples. In this way, we employed the 3D Ni/Co-BTC bimetallic metal–organic framework as new and efficient solid absorbent packed inside a Dynamic Headspace Needle Trap Device for extraction of the Benzene, Toluene, Ethylbenzene and Xylene isomer compounds. For more details, full characterization of the synthesized adsorbent performed by X-ray diffraction, Field emission scanning electron microscopes, Fourier-transform infrared spectroscopy and elemental mapping techniques. In the bench scale, the extraction and thermal desorption parameters such as temperature, time, and percentage salt optimized by Response Surface Methodology and Box Behnken Design. The obtained results exhibited that the optimal extraction time, extraction temperature and salt content of the sample were 35 min, 35°C and 7.5%, respectively. Also, the optimal temperature and time of thermal desorption were determined to be 275°C and 3 min, respectively. The method detection limit of mentioned compounds by this method were in the range of 0.2–1.1 ng.mL−1 that proves the high sensitivity of the proposed method. Moreover, the percentage relative recovery of desired analytes was obtained in the range of 95–99%. The repeatability and reproducibility of proposed method were obtained in the range 1.9–5.8% and 5.5–8.2% respectively, which indicates the acceptable precision of the method. Eventually, this method was successfully employed to determination of Benzene, Toluene, Ethylbenzene and Xylene isomer compounds in the real urine samples. Findings indicated that proposed method can be used to fast, simple and sensitive biological monitoring of non-metabolized Benzene, Toluene, Ethylbenzene and Xylene compounds in the urine samples.

Activated carbon adsorbents with micro-mesoporous structure derived from waste biomass by stepwise activation for toluene removal from air

The waste biomass was used as raw materials to prepare activated carbon adsorbents with micro-mesoporous structure. And the prepared activated carbon adsorbents were used to adsorption remove toluene from air, which can achieve the goal of “treat waste with waste”. In this paper, biomass activated carbon adsorbents with micro‒mesoporous structure were prepared by two-stage process of “low temperature carbonization‒high temperature activation” using waste biomass as raw materials and H3PO4 as activator. The obtained results show that the activation temperature can significantly affect the structural characteristics, graphitization degree and surface chemical properties of the prepared adsorbents, and the toluene adsorption and regeneration performances of the adsorbent are significantly affected by its physicochemical properties. High thermal desorption temperature (100 °C) can destroy the strong interaction between the oxygen atoms of the oxygen-containing functional groups on the surface of the adsorbent and the p-electrons of toluene aromatic ring, thus realizing the desorption of corresponding adsorbed toluene molecules. The low heat treatment temperature of 60 °C can destroy the strong adsorption from narrow micropores for toluene and π‒π conjugation effect between the adsorbent and toluene molecules, which can realize the corresponding adsorbed toluene molecules to be desorbed. When the activation temperature is 650 °C, the activated carbon adsorbent with surface area of 1006.2 m2/g, micro-mesoporous structure and mesoporous proportion of 65.5% can be prepared. The adsorption capacity of toluene can reach 417.0 mg/g, and the toluene thermal desorption regeneration can be realized at 60 °C. The results indicate that it is a promising adsorbent material for toluene removal from air

Changes in Soil Health with Remediation of Petroleum Hydrocarbon Contaminated Soils Using Two Different Remediation Technologies

For sustainable soil management, there is an increasing demand for soil quality, resilience, and health assessment. After remediation of petroleum hydrocarbon (PHC)-contaminated soils, changes in the physicochemical and ecological characteristics of the soil were investigated. Two kinds of remediation technologies were applied to contaminated soils: land farming (LF) and high temperature thermal desorption (HTTD). As a result of total petroleum hydrocarbons (TPH), PHC-contaminated soils were efficiently remediated by LF and HTTD. The soil health could not be completely recovered after the removal of pollutants due to adverse changes in the soil properties, especially in soil enzyme activities. Therefore, monitoring is necessary for accurate estimation of soil ecotoxicity and effective remediation, and additional soil management, such as fertilizer application or organic amendments, is needed to restore soil heath. In the case of HTTD, soil ecological properties are severely changed during the remediation process. The decision to reuse or recycle remediated soils should reflect changes in soil quality. HTTD is a harsh remediation method that results in deterioration of soil fertility and ecological functions. Alternatives, such as low-temperature thermal desorption or additional soil management using fertilizer or organic amendments, for example, are needed.

Rapid screening of illegally added poppy husk in hot pot sauce and soup by thermal desorption electrospray ionization-triple quadruple mass spectrometry

A thermal desorption electrospray ionization-triple quadruple mass spectrometry (TD-ESI-MS/MS) method was developed for the rapid screening of poppy husk in hot pot sauce and soup. The solid surface or liquid sample was directly touched by a simple metal probe. The analytes collected on the probe were desorbed and ionized using a TD-ESI source, after which the analyte ions were detected by MS/MS in multiple reaction monitoring (MRM) mode. The results were compared with those of colloidal gold card rapid detection and verified by high performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC-MS/MS). The instrument gave the best response with the highest sensitivity under the following conditions: thermal desorption temperature, 260 ℃; injection solvent, 0.1% formic acid aqueous solution containing 10 mmol/L formic ammonium-acetonitrile (1:1, v/v); flow rate, 200 μL/h. The limits of detection (LODs) for papaverine, noscapine, and thebaine in five alkaloids were 2 μg/kg, while those for codeine and morphine were 10 μg/kg in hot pot sauce and 5 μg/kg in soup. The sensitivity of this method was significantly superior to that of the colloidal gold card rapid detection. The method was applied to 50 batches of hot pot sauce and soup. Noscapine, papaverine, thebaine, and morphine were detected in a positive sample of chicken soup, which was consistent with the result of the HPLC-MS/MS method. This method without sample preparation and chromatographic separation is fast, green, and environmentally benign, thus being suitable for the rapid qualitative analysis of poppy husk in food.

Photoprocessing of formamide ice: route towards prebiotic chemistry in space

Aims. Formamide (HCONH2) is the simplest molecule containing the peptide bond first detected in the gas phase in Orion-KL and SgrB2. In recent years, it has been observed in high temperature regions such as hot corinos, where thermal desorption is responsible for the sublimation of frozen mantles into the gas phase. The interpretation of observations can benefit from information gathered in the laboratory, where it is possible to simulate the thermal desorption process and to study formamide under simulated space conditions such as UV irradiation. Methods. Here, two laboratory analyses are reported: we studied formamide photo-stability under UV irradiation when it is adsorbed by space relevant minerals at 63 K and in the vacuum regime. We also investigated temperature programmed desorption of pure formamide ice in the presence of TiO2 dust before and after UV irradiation. Results. Through these analyses, the effects of UV degradation and the interaction between formamide and different minerals are compared. We find that silicates, both hydrates and anhydrates, offer molecules a higher level of protection from UV degradation than mineral oxides. The desorption temperature found for pure formamide is 220 K. The desorption temperature increases to 250 K when the formamide desorbs from the surface of TiO2 grains. Conclusions. Through the experiments outlined here, it is possible to follow the desorption of formamide and its fragments, simulate the desorption process in star forming regions and hot corinos, and constrain parameters such as the thermal desorption temperature of formamide and its fragments and the binding energies involved. Our results offer support to observational data and improve our understanding of the role of the grain surface in enriching the chemistry in space.

Direct detection of chemical warfare agent simulants in soil by thermal desorption-low temperature plasma-mass spectrometry

For rapid, accurate and real-time detection of trace chemical warfare agents in soil, direct detection of chemical warfare agent simulants in soil by thermal desorption-low temperature plasma ionization-mass spectrometry was developed. Multi-factor analysis of variance was used to quantitatively analyze the factors affecting the ionization efficiency of low temperature plasma based on the emission spectra of the plasma flame. The experimental parameters including the distance between low temperature plasma outlet and thermal desorption device, the flow rate of discharge gas, the temperature of ion source, the thermal desorption temperature and different solvents were optimized. Dimethyl methylphosphonate (DMMP, G-series nerve agent simulant), tributyl phosphate (TBP, V-series nerve agent simulant) and 2-Chloroethyl ethylsulfide (CEES, H-series blister agent simulant) were desorbed and ionized, forming the typical positive ions of [DMMP + H]+, [DMMP-HOCH3+H]+, [TBP + H]+, [TBP-3(C4H8)+H]+ and [CEES-Cl]+, [CEES- C2H4Cl]+. The ions were analyzed using the multiple reaction monitoring (MRM) of triple quadrupole mass spectrometer. Detection limit of the method was 5 pg for DMMP (m/z 125→93, S/N＞3:1), 5 pg for TBP (m/z 267→99, S/N＞3:1) and 5 ng for CEES (m/z 89→61, S/N＞3:1). Trace level of CWA simulants can be directly detected with simple sample pretreatment, suggesting that the thermal desorption-low temperature plasma-mass spectrometry method is useful for quick and direct detection of chemical warfare agents in soil.

Insight into ex-situ thermal desorption of soils contaminated with petroleum via carbon number-based fraction approach

Ex-situ thermal desorption treatment (ESTD) of petroleum contaminated soil (PCS) was developed to investigate the desorption behavior of five carbon number-based fractions of extractable petroleum hydrocarbons (EPHs) and the morphology changes of soils. The experimental kinetics, isotherm models and thermodynamic parameters were analyzed to provide mechanism insight. Results suggest that most of the diesel range organics (DRO, C10-C28) was removed at low temperatures (100–350 °C), while high temperature (350–550 °C) thermal desorption (HTTD) was effective in removing EPHs due to the high removal efficiency of oil range organics (ORO, C28-C40). Under HTTD treatment, the re-adsorption of low molecular weight hydrocarbons was observed. The particle size of sandy soil barely changed during desorption process, while a significant agglomeration was found in red clayey at high temperatures. The desorption kinetics can be well fitted by the exponential decay model, and the desorption equilibrium agrees with the Langmuir isotherm model. The removal process of EPHs was controlled by multiple diffusion mechanisms. ΔH° values of GS and RS were 65.73 kJ/mol and 76.29 kJ/mol, respectively. DRO was mainly controlled by physical adsorption, while to a great extent ORO release was controlled by chemical adsorption. Finally, removal mechanisms and matrix control mechanisms during ESTD treatment were proposed.

Computational study of HCl adsorption on stoichiometric and oxygen vacancy PuO2 {111}, {110} and {100} surfaces

The interactions between HCl and both the pristine and defect {111}, {110} and {100} surfaces of PuO2 are modelled using hybrid density functional theory, within the periodic electrostatic embedded cluster method. In the case of the pristine surfaces, adsorptions onto the {110} surface are the most stable, likely due in part to the presence of surface hydrogen bonds. In addition, results suggest that even when dissociatively adsorbed onto the surface, the proximity of the hydrogen and chlorine atoms has a significant impact on the stability of the system. The electronic structure of both the pristine and reduced surfaces of PuO2 and UO2 is also probed, with unpaired electrons left behind in a neutral oxygen vacancy defect site having a greater tendency to delocalise on the surface of UO2 than PuO2. HCl adsorptions on the reduced surfaces reveal that configurations in which the chlorine atom attempts to “heal” the gap left by the oxygen vacancy in the {111} surface are by far the most stable of all considered. Finally, molecular thermodynamics is employed to translate adsorption energies to HCl thermal desorption temperatures, for each geometry considered. Particularly when a chlorine atom is embedded in the surface of PuO2, the temperatures required for thermal desorption to occur are high, implying that although thermal treatment is likely to remove some chlorine contamination from PuO2 samples, some will likely remain bound to defect sites within the material.

Optimization of the Conditions of Analysis of Exhaled Air by Gas Chromatography–Mass Spectrometry for the Noninvasive Diagnostics of Lung Cancer

We optimized procedures for the collection, preparation, and storage of samples of exhaled air and the conditions for determining volatile organic compounds in exhaled air by gas chromatography–mass spectrometry (GC–MS), the presence or change in the concentration of which can be caused by lung cancer. The analysis circuit includes group adsorption preconcentration followed by the thermal desorption and determination of analytes by GC–MS. Polymer bags of a Tedlar® film were used for sample collection. The conditions and periods of the storage of samples in bags and adsorption tubes are determined. A method for cleaning and conditioning bags is proposed. For preconcentrating exhaled air components, we used hydrophobic adsorbents (Porapak™ P, Porapak™ Q, and Tenax® TA) and three-section tubes containing Tenax® GR, Carbopack™ B, and Carbosieve® S-III. Their relative efficiency was evaluated by assessing the residual background of gas emission from the adsorbent, the magnitude of the analytical signal, the efficiency of adsorption/desorption, and the efficiency of storage. The conditions for the preconcentration of volatile organic compounds (volume and rate of aspiration, time, and temperature of thermal desorption) are optimized. The main volatile organic compounds in the exhaled air of conditionally healthy volunteers were identified, and their concentrations are evaluated.

Insights into the O : C-dependent mechanisms controlling the evaporation of α-pinene secondary organic aerosol particles

Abstract. The volatility of oxidation products of volatile organic compounds (VOCs) in the atmosphere is a key factor to determine if they partition into the particle phase contributing to secondary organic aerosol (SOA) mass. Thus, linking volatility and measured particle composition will provide insights into SOA formation and its fate in the atmosphere. We produced α-pinene SOA with three different oxidation levels (characterized by average oxygen-to-carbon ratio; O:C‾=0.53, 0.69, and 0.96) in an oxidation flow reactor. We investigated the particle volatility by isothermal evaporation in clean air as a function of relative humidity (RH &lt;2 %, 40 %, and 80 %) and used a filter-based thermal desorption method to gain volatility and chemical composition information. We observed reduced particle evaporation for particles with increasing O:C‾ ratio, indicating that particles become more resilient to evaporation with oxidative aging. Particle evaporation was increased in the presence of water vapour and presumably particulate water; at the same time the resistance of the residual particles to thermal desorption was increased as well. For SOA with O:C‾=0.96, the unexpectedly large increase in mean thermal desorption temperature and changes in the thermogram shapes under wet conditions (80 % RH) were an indication of aqueous phase chemistry. For the lower O:C‾ cases, some water-induced composition changes were observed. However, the enhanced evaporation under wet conditions could be explained by the reduction in particle viscosity from the semi-solid to liquid-like range, and the observed higher desorption temperature of the residual particles is a direct consequence of the increased removal of high-volatility and the continued presence of low-volatility compounds.

Temperature-Dependent DART-MS Analysis of Sexual Lubricants to Increase Accurate Associations.

The analysis of lubricant evidence is a recent development in sexual assault investigations and in the absence of any biological evidence may assist in linking an assailant to the victim or crime scene. An ambient ionization technique, high-resolution direct analysis in real-time mass spectrometry (HR-DART-MS), was employed to characterize a sample set of 33 water-based lubricants. As lubricants are complex multicomponent mixtures, this study investigated if different thermal desorption temperatures could elucidate different additives and provide additional information. A low-temperature, high-temperature, and thermal desorption/pyrolysis DART-MS protocol was used to characterize the water-based lubricant sample set. The strength of the methodologies was evaluated using positive and negative likelihood ratios that were calculated from inter- and intra-pairwise comparisons using Pearson correlation coefficients. The low-temperature DART-MS protocol afforded valuable information pertaining to volatile additives (e.g., flavors and fragrances) and provided positive likelihood ratios that would provide strong support for true positive and negatives than the high-temperature protocol when associating between individual samples and samples to their respective sub-groupings. The thermal desorption/pyrolysis DART analytical protocol provided enhanced differentiation between samples due to the precise temperature control using a thermal gradient. Moreover, the total ion spectra obtained from the thermal desorption/pyrolysis protocol, not only had high positive and negative likelihood ratios, this method also provided the most discrimination as determined by empirical cross entropy plots. Graphical Abstract.

Automated thermal extraction-desorption gas chromatography mass spectrometry: A multifunctional tool for comprehensive characterization of polymers and their degradation products

The TED-GC–MS analysis is a two-step method. A sample is first decomposed in a thermogravimetric analyzer (TGA) and the gaseous decomposition products are then trapped on a solid-phase adsorber. Subsequently, the solid-phase adsorber is analyzed with thermal desorption gas chromatography mass spectrometry (TDU-GC–MS). This method is ideally suited for the analysis of polymers and their degradation processes. Here, a new entirely automated system is introduced which enables high sample throughput and reproducible automated fractioned collection of decomposition products.The fractionated collection together with low temperatures reduces the risk of contamination, improves instrumental stability and minimizes maintenance efforts. Through variation of the two main parameters (purge gas flow and heating rate) it is shown how the extraction process can be optimized. By measuring the decomposition products of polyethylene it is demonstrated that compounds with masses of up to 434 Da can be detected. This is achieved despite the low temperature (˜40 °C) of the solid-phase adsorber and the low thermal desorption temperature of 200 °C in the TDU unit.It is now shown that automated TED-GC–MS represents a new flexible multi-functional method for comprehensive polymer analyses. Comparable polymer characterization was previously only achievable through a combination of multiple independent analytical methods. This is demonstrated by three examples focused on practical challenges in materials analysis and identification: The first one is the analysis of wood plastic composites for which the decomposition processes of the polymer and the bio polymer (wood) could be clearly distinguished by fractionated collection using sequential adsorbers. Secondly, a fast quantitative application is shown by determining the weight concentrations of an unknown polyolefin blend through comparison with a reference material. Additionally, the determination of microplastic concentrations in environmental samples is becoming an increasingly important analytical necessity. It is demonstrated that with TED-GC–MS calibration curves showing good linearity for the most important precursors for microplastic, even complex matrix materials (suspended particulate matter) can be successfully analyzed.

Deuterium retention in re-solidified tungsten and beryllium

Leading edges of the ITER tungsten (W) divertor are expected to melt due to transient heat loads from edge localized modes (ELMs), and melting of the entire divertor surface will occur during vertical displacement events (VDEs) and disruptions. In addition, understanding tritium retention in plasma facing materials is critical for the successful operation of ITER due to safety reasons. Thus, the question of how melting affects hydrogenic retention is highly relevant for fusion devices. Here we use an Nd:YAG laser to melt tungsten and beryllium in vacuo, and the samples are subsequently exposed to deuterium plasma with sample temperatures ranging from 370 to 750 K. The deuterium content in re-solidified and reference (no laser) samples is measured using thermal desorption spectroscopy and modeled using TMAP-7. In all cases, the re-solidified samples have lower retention compared to the reference samples. For re-solidified tungsten, the most significant effect is in the 1.8 eV trap with peak thermal desorption temperature of ∼750 K, which had a 77% reduction in the peak release rate compared with the reference sample. SEM imaging indicates that laser melting and re-solidification of tungsten anneals intrinsic defects that act as nucleation sites for larger-scale defects that develop during plasma exposure. However, melting does not significantly affect traps with lower de-trapping energies of 1.0 eV and 1.4 eV. In beryllium, melting and cracking results in lower retention compared to the reference sample by 40%, and thermal desorption profiles indicate that the diffusion depth of deuterium into re-solidified beryllium is lower than that of the reference sample.

Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

Context. Methanol is formed via surface reactions on icy dust grains. Methanol is also detected in the gas-phase at temperatures below its thermal desorption temperature and at levels higher than can be explained by pure gas-phase chemistry. The process that controls the transition from solid state to gas-phase methanol in cold environments is not understood. Aims. The goal of this work is to investigate whether thermal CO desorption provides an indirect pathway for methanol to co-desorb at low temperatures. Methods. Mixed CH3OH:CO/CH4 ices were heated under ultra-high vacuum conditions and ice contents are traced using RAIRS (reflection absorption IR spectroscopy), while desorbing species were detected mass spectrometrically. An updated gas-grain chemical network was used to test the impact of the results of these experiments. The physical model used is applicable for TW Hya, a protoplanetary disk in which cold gas-phase methanol has recently been detected. Results. Methanol release together with thermal CO desorption is found to be an ineffective process in the experiments, resulting in an upper limit of ≤ 7.3 × 10−7 CH3OH molecules per CO molecule over all ice mixtures considered. Chemical modelling based on the upper limits shows that co-desorption rates as low as 10−6 CH3OH molecules per CO molecule are high enough to release substantial amounts of methanol to the gas-phase at and around the location of the CO thermal desorption front in a protoplanetary disk. The impact of thermal co-desorption of CH3OH with CO as a grain-gas bridge mechanism is compared with that of UV induced photodesorption and chemisorption.

Helium retention behavior in simultaneously He+-H2+ irradiated tungsten

The purpose of this study is to elucidate helium (He) retention behavior in tungsten (W) under simultaneous He and hydrogen (H) irradiation. Polycrystalline-W was irradiated by He+ and H2+ simultaneously with the energy of 1.0 keV and 3.0 keV. He+ fluences were (0.5, 1.0, 10) × 1021 He+ m−2 and H2+ fluence was 1.0 × 1022 H+ m−2,respectively. After irradiation, He desorption behavior was investigated by high temperature thermal desorption spectroscopy (HT-TDS) in the temperature range of R.T.-1773 K. Micro-structure changes of W after irradiation were observed by TEM. It was found that simultaneous irradiation with different H2+ energy significantly changed He retention behavior. 1.0 keV H2+ suppressed the He bubble growth and no bubbles can be observed at room temperature. On the other hand, 3.0 keV H2+ facilitated the formation of He bubbles and increased the He retention due to the additional damage introduction by energetic H2+.