Time-dependent categorization of volatile aroma compound formation in stewed Chinese spicy beef using electron nose profile coupled with thermal desorption GC–MS detection

In the present study,flavor profiles of Chinese spiced beef in the cooking process were comparatively analyzed by electronic nose,gas chromatography–mass spectrometry(GC–MS)with a thermal desorption system(TDS),and solid-phase microextraction(SPME).A total of 82 volatile compounds were identified,and 3-methyl-butanal,pentanal,hexanal,-xylene,heptanal,limonene,terpinene,octanal,linalool,4-terpinenol,-terpineol,and(E)-anethole were identified as the characteristic flavor compounds in Chinese spiced beef.Variation in the content of volatile components produced by different cooking processes was observed.In general,a cooking time of 4 h resulted in optimal flavor quality and stability.Results indicated that the electronic nose could profile and rapidly distinguish variation among different cooking time.The volatile profiling by TDS-GC–MS and responses from the electronic nose,in combination with multivariate statistical analysis,are a promising tool for control the cooking process of spiced beef.

Thermal desorption of mercury from lignite in a high-temperature furnace and in power plant mills

In this article,the binding forms of two lignite samples are determined by thermal desorption using a high-temperature furnace.Each mercury compound,such as HgCl2,has a specifc binding strength whose decomposition requires a certain thermal energy.Hence,the release of mercury from pure substances and lignite samples was analyzed in a high-temperature furnace.The released mercury is determined with a Mercury Vapor Monitor.The obtained characteristic temperature range and peak of the mercury release were compared between lignite samples and mercury pure substances.For the lignite samples investigated,the binding form of mercury was then identifed as Humic Acid.These organic compounds vaporize at lower temperatures.About half of the mercury bound in the lignite was already released at 350℃.Furthermore,the question arises whether mercury is already released during the grinding-drying process in the coal mill of a power plant.At two power plants,lignite samples were taken simultaneously at the feeder before entering the coal mill and at the dust line afterwards.The samples were analyzed for mercury concentration.The results show that up to one third of the mercury was already released in the coal mill.The vaporized mercury enters the combustion chamber detached from the lignite.The stated analysis methods and the results presented in this article contribute to the understanding of the mercury binding forms in lignite.It also shows the potential of thermal coal pretreatment as a favorable alternative mercury separation technology to others such as activated carbon dosing.

Epitaxial growth of antimony nanofilms on HOPG and thermal desorption to control the film thickness

Group-V elemental nanofilms were predicted to exhibit interesting physical properties such as nontrivial topological properties due to their strong spin-orbit coupling,the quantum confinement,and surface effect.It was reported that the ultrathin Sb nanofilms can undergo a series of topological transitions as a function of the film thickness h:from a topological semimetal(h>7.8 nm)to a topological insulator(7.8 nm>h>2.7 nm),then a quantum spin Hall(QSH)phase(2.7 nm>h>1.0 nm)and a topological trivial semiconductor(h<1.0 nm).Here,we report a comprehensive investigation on the epitaxial growth of Sb nanofilms on highly oriented pyrolytic graphite(HOPG)substrate and the controllable thermal desorption to achieve their specific thickness.The morphology,thickness,atomic structure,and thermal-strain effect of the Sb nanofilms were characterized by a combination study of scanning electron microscopy(SEM),atomic force microscopy(AFM),and scanning tunneling microscopy(STM).The realization of Sb nanofilms with specific thickness paves the way for the further exploring their thickness-dependent topological phase transitions and exotic physical properties.

The Impact of Thermal Desorption Unit Associated with Remediation of Hydrocarbon Impacted Soils on Air Quality at Beneku, Ndokwa East, Delta State, Nigeria

The study is on the use of thermal desorption unit in the remediation of contaminated soils located at Beneku in Ndokwa East local government area of Delta state. This method uses heat to vaporize the contaminants, and as such only works for volatile contaminants. Air quality samples around the thermal desorption Unit (TDU), used for the treatment of hydrocarbon impacted soils were taken at six (6) different sampling points (Stations). The sampling points were 100 m apart beginning from 0 m which was the closest to the TDU. The results showed that the mean values of SO2 were 0.01 ppm for both the dry and wet seasons and it is within the FMEnv limit of 0.01. The mean concentration of NO2 in the dry season was 0.25 μg/m3 and in the wet season it was 0.18 μg/m3, which were above the FMEnv limit of 0.06 μg/m3. It is a strong oxidizing agent that reacts with air/water to form corrosive nitric acid, as well as toxic organic nitrates. The mean concentration of CO2 recorded in the dry season was 11.52 ppm and that for the wet season was 10.53 ppm, which were slightly above the FMEnv limit of 10.00 ppm. The levels of SPM 2.5 recorded in the study show a concentration of 132.07 μg/m3 in the dry season and 95.93 μg/m3 in the wet season while those for SPM 10 had 102.17 μg/m3 in the dry season and 91.33 μg/m3 in the wet season. The level of the VOC recorded across the study area was significantly low (0.11 μg/m3). The mean H2S concentration recorded across the study area was low (0.01 μg/m3). Several health risks have been associated with SPM. Inhaling SPM affects respiratory and cardiovascular systems in both children and adults. Fine SPM (such as PM 2.5 particulate) can penetrate into the lungs and blood streams when inhaled, resulting to respiratory problems, heart attack, lung cancer and even death, while exposure to low levels of H2S can induce headaches as well as breathing difficulties in some asthmatic patients.

New Activated Carbon with High Thermal Conductivity and Its Microwave Regeneration Performance

Using a walnut shellas a carbon source and ZnCl_2 as an activating agent,we resolved the temperature gradient problems of activated carbon in the microwave desorption process.An appropriate amount of silicon carbide was added to prepare the composite activated carbon with high thermalconductivity while developing VOC adsorption-microwave regeneration technology.The experimentalresults show that the coefficient of thermalconductivity of SiC-AC is three times as much as those of AC and SY-6.When microwave power was 480 W in its microwave desorption,the temperature of the bed thermaldesorption was 10 ℃ to 30 ℃ below that of normalactivated carbon prepared in our laboratory.The toluene desorption activation energy was 16.05 k J·mol^（-1）,which was 15% less than the desorption activation energy of commercialactivated carbon.This study testified that the process could maintain its high adsorption and regeneration desorption performances.

Temperature-free mass tracking of a levitated nanoparticle

Mass measurement is an essential analytical tool in the characterization of materials.Here we present a method for measuring the mass of an individual nanoparticle which has a fg-level mass.This method enables a temperatureindependent mass measurement with the assistance of a sinusoidal electrostatic driving force.With this approach,we successfully track the change in properties of an optically levitated nanoparticle,such as mass,temperature,and electric charge,with air pressure.An abrupt change in the mass of silica nanoparticles is found to violate the Zhuravlev model.This method can be utilized to extend the mass analysis of materials,such as thermogravimetric analysis,to individual microor nano-particles.

Shale oil resource evaluation with an improved understanding of free hydrocarbons:Insights from three-step hydrocarbon thermal desorption

The pyrolysis parameter S1,which indicates the amount of free hydrocarbons present in shale,is often underestimated due to hydrocarbon loss during sample handling and measurement processes.To remedy this issue,we strongly recommend an immediate three-step hydrocarbon thermal desorption(HTD)approach to be conducted on oil shale at the drilling site.This approach measures S_(g),S_(O),and S_(1)^(*),which refer to gaseous,light,and free hydrocarbons,respectively.The new shale oil content value,calculated from the total of these three parameters,is far more precise and reliable than traditional pyrolysis S1.Moreover,we thoroughly investigated the components and microscopic occurrence features of hydrocarbons thermally desorbed at three temperature stages using gas chromatography(GC)and X-ray microcomputed tomography(CT).For example,we selected Chang 7_(3)mud shale.Our experimental results irrefutably indicate that the ultimate shale oil content of poor resource rocks is significantly impacted by evaporative loss,with this effect being greater when the total organic carbon(TOC)is lower.Additionally,C_(1-5)and C_(1-7)hydrocarbons constitute almost all of S_(g)and S_(O),respectively.S_(g)and S_(O)are predominantly composed of C_(1-3)gaseous hydrocarbons,with a maximum proportion of 42.93%.In contrast,S_(1)^(*)contains a substantial amount of C_(16-31)hydrocarbons.A three-dimensional reconstruction model of an X-ray micro-CT scan shows that while the amount of shale organic matter greatly decreases from the frozen state to 300℃,the pore volume significantly increases,particularly between 90 and 300℃.The increased pore volume is mainly due to macropores and fractures.It is imperative to note that the shale oil triple-division boundaries must be adjusted based on more accurate oil content,although this would not affect the resource zones to which the samples already belong(ineffective,low-efficient,and enriched resources).In conclusion,we strongly advise conducting an immediate well-site analysis or utilizing preservation procedures,such as deep freezing or plastic film wrapping followed by core waxing,to minimize volatile loss.

Influence of mineral species on oil-soil interfacial interaction in petroleum-contaminated soils

The mineral species in soils vary in a wide variety of places,thus resulting in the petroleumcontaminated soil(PCS)with complex characters.Thus,the research on the effect of mineral species on oil-soil interactions in PCS takes on a critical significance.In this study,the desorption and adsorption behaviors of aromatic hydrocarbons(Ar)on two minerals surfaces were examined.Meanwhile,the interfacial forces between minerals and Ar were studied and the sources of these forces were analyzed.Moreover,molecular dynamics(MD)simulations were conducted to gain insight into the interfacial interaction mechanisms.As revealed by the results of this study,in comparison with Qs-Ar(quartz sand,Qs),Mnt-Ar(montmorillonite,Mnt)contaminants required higher temperature and activation energies for thermal desorption(201.95 kJ·mol^(-1)vs.127.82 kJ·mol^(-1))The above difference was generated since the adhesive forces between Ar and Mnt surfaces were greater than those between Ar and Qs.As indicated by the analysis of the adhesion force sources,the van der Waals forces were responsible for facilitating oil adhesion to mineral surfaces,even though the electrostatic force prevented oil-mineral adhesion.Furthermore,the hydrophobic forces facilitated adhesion in 3 nm.The MD results demonstrated that compared with the Qs system,there existed larger binding energies between Ar and Mnt,a lower diffusion coefficient for Ar on the Mnt surface,as well as more significant adsorption of Ar on Mnt.In general,the different mineral species affect the strength of the interaction at the oil-soil interface,which is a guideline for proposing targeted oil-soil separation measures.

Effects of Diesel Concentration on the Thermal Conductivity,Specific Heat Capacity and Thermal Diffusivity of Diesel-Contaminated Soil

High energy consumption is a serious issue associated with in situ thermal desorption(TD)remediation of sites contaminated by petroleum hydrocarbons(PHs).The knowledge on the thermophysical properties of contaminated soil can help predict accurately the transient temperature distribution in a remediation site,for the purpose of energy conservation.However,such data are rarely reported for PH-contaminated soil.In this study,by taking diesel as a representative example for PHs,soil samples with constant dry bulk density but different diesel mass concentrations ranging from 0% to 20% were prepared,and the variations of their thermal conductivity,specific heat capacity and thermal diffusivity were measured and analyzed over a wide temperature range between 0℃ and 120℃.It was found that the effect of diesel concentration on the thermal conductivity of soil is negligible when it is below 1%.When diesel concentration is below 10%,the thermal conductivity of soil increases with raising the temperature.However,when diesel concentration becomes above 10%,the change of the thermal conductivity of soil with temperature exhibits the opposite trend.This is mainly due to the competition between soil minerals and diesel,because the thermal conductivity of minerals increases with temperature,whereas the thermal conductivity of diesel decreases with temperature.The analysis results showed that,compared with temperature,the diesel concentration has more significant effects on soil thermal conductivity.Regardless of the diesel concentration,with the increase of temperature,the specific heat capacity of soil increases,while the thermal diffusivity of soil decreases.In addition,the results of a control experiment exhibited that the relative differences of the thermal conductivity of the soil samples containing the same concentration of both diesel and a pure alkane are all below 10%,indicating that the results obtained with diesel in this study can be extended to the family of PHs.A theoretical prediction model was proposed based on cubic fractal and thermal resistance analysis,which confirmed that diesel concentration does have a significant effect on soil thermal conductivity.For the sake of practical applications,a regression model with the diesel concentration as a primary parameter was also proposed.

Determining indoor air quality and identifying the origin of odour episodes in indoor environments

A methodology for identifying volatile organic compounds （VOCs） and determining air quality of indoor air has been developed. The air samples are collected using pump samplers by the inhabitants when they perceive odorous and/or discomfort episodes. Glass multi-sorbent tubes are connected to the pump samplers for the retention of VOC. The analysis is performed by automatic thermal desorption （ATD） coupled with gas chromatography-mass spectrometry （GC/MS）. This methodology can be applied in cases of sick building syndrome （SBS） evaluation, in which building occupants experience a series of varied symptoms that appear to be linked to time spent in the building. Chemical pollutants concentrations （e.g., VOC） have been described to contribute to SBS. To exemplify the methodology, a qualitative determination and an evaluation of existing VOC were performed in a dwelling where the occupants experienced the SBS symptoms. Higher total VOC （TVOC） levels were detected during episodes in indoor air （1.33 ±1.53 mg/m^3） compared to outdoor air （0.71± 0.46 mg/m^3）. The concentrations of individual VOCs, such as ethanol, acetone, isopropanol, 1-butanol, acetic acid, acetonitrile and 1-methoxy-2-propanol, were also higher than the expected for a standard dwelling. The external source of VOC was found to be an undeclared activity of storage and manipulation of solvents located at the bottom of a contiguous building.

Method for rapid on-site identification of VOCs

Rapid on-site identification of volatile organic compounds （VOCs） in ambient air is an important first step in remediation efforts. This study describes modification of a commercially available, portable GC/MS system and development of an analysis protocol for rapid （〈 3 min） sampling and identification of VOCs typically found at contaminated sites at the low ppbv level.

Progress in fundamental research on thermal desorption remediation of organic compound-contaminated soil

Thermal desorption(TD)is a mainstream technology for the remediation of organic compound-contaminated soil.By reviewing the domestic and foreign research on the remediation of organic compound-contaminated soil by TD,this paper systematically introduces the principle,characteristics,and classification of TD.The impact of key operating parameters(such as heating temperature and heating time),certain physical and chemical properties(such as soil texture,moisture content),and external conditions(such as additives and the carrier gas)on the TD process is summarized.Next,pollutants’migration and their transformation processes,as well as the laws governing the TD process,are briefly described.Finally,the prospects of TD,in terms of its future research and development directions,are described,with the aim of providing references for the application and promotion of TD.

Investigation on Retention and Release Behaviors of Hydrogen and Helium in Vanadium Alloy

Vanadium alloy is proposed as an attractive candidate for first wall and blanket structural material of fusion reactors. The retention and release behaviors of hydrogen and helium in vanadium alloy may be an important issue. In the present work, 1.7 keV deuterium and 5 keV helium ions are respectively implanted into V-4Cr-4Ti and V-4Ti at room temperature. The retention and release of deuterium and helium are measured with thermal desorption spectroscopy (TDS). When the helium ion fluence is larger than 3 × 1017 He/cm2, the retained helium saturates with a value of approximately 2.5 ×1017 He/cm2. However, when the ion fluence is 1×1019 D/cm2, the hydrogen saturation in vanadium alloy does not take place. Experimental results indicates that hydrogen and helium retention in vanadium alloy may lead to serious problems and special attention should be paid when it is applied to fusion reactors.

Determination of activation energy of ion-implanted deuterium release from W–Y2O3

The retention and release of deuterium in W–2%Y2O3 composite materials and commercially pure tungsten after they have been implanted by deuterium plasma(flux ~ 3.71 × 1021 D/m2·s, energy ~ 25 eV, and fluence up to 1.3 × 1026D/m2)are studied. The results show that the total amount of deuterium released from W–2%Y2O3 is 5.23 × 1020 D/m2(2.5 K/min),about 2.5 times higher than that from the pure tungsten. Thermal desorption spectra(TDS) at different heating rates(2.5 K/min–20 K/min) reveal that both W and W–2%Y2O3 have two main deuterium trapped sites. For the low temperature trap, the deuterium desorption activation energy is 0.85 eV(grain boundary) in W, while for high temperature trap, the desorption activation energy is 1.57 eV(vacancy) in W and 1.73 eV(vacancy) in W–2%Y2O3.

Adsorption, Diffusion and Thermal Desorption Features of Cyclopentane and Cyclohexane in Silicalite-1

Adsorption, diffusion and thermal desorption features of cyclopentane and cyclohexane in silicalite-1 have been investigated using the intelligent gravimetric technique. Both the saturation adsorption loadings and diffusion coefficient of cyclopentane were greater than those of cyclohexane. The diffusivity of cyclopentane was about one order of magnitude greater than that of cyclohexane at the same temperature and initial loading. For cyclopentane, there was only one kind of desorption process at adsorption loadings lower than 4 muc （molecule per unit cell）, but two desorption processes appeared at the adsorption loadings higher than 4 muc. While for cyclohexane, one desorption process was found in the whole range of loadings. Both thermal desorption peaks of cyclopentane and cyclohexane moved to higher temperature region with increasing loading.

Use of NiO/SiO_2 catalysts for toluene total oxidation:Catalytic reaction at lower temperatures and repeated regeneration

We deposited NiO via atomic layer deposition on mesoporous SiO2 particles with diameters of several hundred micrometers and a mean mesopore size of -14 nm.NiO was deposited within the shell region of mesoporous SiO2 particles with a shell thickness of -11 mm.We annealed the as-prepared NiO/SiO2 at 450 and 600℃,respectively.These two samples were used as catalysts for the uptake of toluene molecules and their oxidative conversion to CO2.The sample annealed at450℃ was generally more reactive in toluene uptake and its subsequent conversion to CO2.When the NiO/SiO2 annealed at 450℃ was exposed to toluene vapor at 160℃ and then heated to 450℃,CO2 was emitted with almost no toluene desorption.We suggest that our catalysts can be used as building blocks for odor removal devices that operate below 200℃.These catalysts can be regularly regenerated at -450℃.

In-situ probing of thermal desorption of vapor molecules on a nanowire via work function variance

Nanowire sensors based on variations of their electrical properties show great potential for real-time, in situ monitoring of molecular adsorption and desorption. Although the molecular adsorption-induced change in the electronic work function is very sensitive, it does not have any specificity. However, the temperature dependency of the adsorption-induced work function variation can provide limited selectivity based on the desorption temperature. In this study, we report the in situ probing of molecular desorption by monitoring the work function variations of a single Pt nanowire as a function of temperature. The work function of a clean Pt nanowire shows a significant variation due to vapor adsorption at room temperature. Increasing the temperature of the nanowire results in a variation of the work function due to molecular desorption. Experimentally measured differential work function as a function of temperature shows desorption peaks at 36 and 44 ℃ for methanol and ethanol molecules respectively. Adsorption-induced variation of the Pt nanowire work function was further confirmed using ultraviolet photoelectron spectroscopy before and after exposure to methanol vapor. These results show that the molecular adsorption/desorption-induced variation of the work function and its temperature dependency can be used for developing nanoscale electro-calorimetric sensors.

Relationship between hydrogen concentration and mechanical properties of 5Ni-16Cr-Mo steel

The qualitative relationship between hydrogen concentration and notch tensile strength has been investigated for 5Ni-16Cr-Mo steel with different strength.The notch tensile strength was determined by means of slow strain rate test(SSRT)on circumferentially notched round bar specimens with the notch root radius of 0.15 mm after hydrogen charging.Meanwhile,the hydrogen diffusion behaviors of various strength steel were studied by thermal desorption spectroscopy(TDS)analysis.The SSRT results show that the T460 steel has higher susceptibility of hydrogen embrittlement in contrast with T520 steel.The activation energies and microstructure indicate that the dislocations and interfaces of martensitic laths are hydrogen traps in 5Ni-16Cr-Mo steel.By SSRT,the elastic limit of charged specimen loaded in air is higher than the flow stress without hydrogen charging before unloading,while the difference is defined as hydrogen-induced stress.The value of hydrogen-induced stress σ*increases linearly with hydrogen concentration:σ*=−0.622+2.015C0.The finite element analysis results of stress distributions near the notch tip have shown that the maximum principal stress increases with the notch root radius decreasing.

Oxygenic iron clusters in ZSM-5 zeolite promote quantum sieving of gaseous hydrogen isotopes

Isotopic separation is of paramount importance for producing high-purity heavy hydrogen,yet the process remains hugely challenging.Here,we report on an Fe/ZSM-5 zeolite that was able to efficiently separate deuterium from protium via chemical quantum sieving.Structural data showed that four types of Fe species were present in Fe/ZSM-5 and oligomeric Fe-O clusters in the zeolite pores were correlated directly with gas selectivity.Gas adsorption revealed that Fe-O species served as the main adsorption sites and interacted with D_(2) more strongly than with H_(2).D_(2)/H_(2)separation was exemplified using thermal desorption spectroscopy.D_(2)/H_(2) selectivity increased with Fe loading in Fe/ZSM-5 and a selectivity of 32.1 was obtained with an optimal loading of 7 wt%.The shift of desorption temperature supports the chemical affinity-based quantum sieving of D_(2)over H_(2).This study demonstrates an effective strategy for enhancing D_(2)/H_(2) separation and the high selectivity means that Fe/ZSM-5 has strong potential in hydrogen isotope separation.

Constructing Ce-Mn/Al_(2)O_(3)with different active components for low temperature catalytic degradation of chlorobenzene in soil

Soil remediation containing numerous organic contaminants is of great significance to ecological environment.Herein,the synergetic effects of Ce-Mn/Al_(2)O_(3)with different active components on catalytic thermal desorption of chlorobenzene in soil were investigated.The optimized Ce-Mn/Al_(2)O_(3)drastically enhance the desorption efficiency of chlorobenzene,and the corresponding conversion reaches 100%within 1 h at a low temperature of 120℃.The superior performance is ascribed to the formation of Ce-Mn solid solution during the calcination process,resulting in a certain lattice change to the generation of abundant oxygen vacancies and acidic sites.Combining with the analysis of in-situ diffuse reflectance infrared spectroscopy and gas chromatography-mass spectrometry,the final products of chlorobenzene are decomposed into CO_(2),H_(2)O,Cl_(2)and HCl.This work sheds light on the rational design of highly-active catalysts for practical applications of sustainable soil remediation.