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.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

The multi-walled carbon nanotubes(MWCNTs) studied in this work were synthesized by the catalytic chemical vapor deposition(CCVD) process, and were thermally annealed by the hot filament plasma enhanced(HF PE) method at 550℃ for two hours.The x-ray absorption near edge structure(XANES) technique was used to investigate the adsorption and desorption phenomena of the MWCNTs at normal and grazing incidence angles.The adsorbates were found to have different sensitivities to the thermal annealing.The geometry of the incident beam consistently gave information about the adsorption and desorption phenomena.In addition, the adsorption of non-intrinsic potassium quantitatively affected the intrinsic adsorbates and contributed to increase the conductivity of the MWCNTs.The desorption of potassium was almost 70% greater after the thermal annealing.The potassium non-intrinsic adsorbates are from a physisorption mechanism whereas the intrinsic adsorbates result from chemisorption.

Thermal desorption characteristic of helium ion irradiated nickel-base alloy

The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose(peak displacement damage 1-10 dpa).Then thermal desorption spectroscopy(TDS)of helium atoms was performed to discuss the helium desorption characteristic and trapping sites.The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation,reflecting the reduced diffusion activation energy and faster diffusion within the alloy.The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence,which is because the irradiation damage of 180 keV,helium formation and entrapment occur deeper.The broadening of the spectra corresponds to different helium trapping sites(He-vacancies,grain boundary)and desorption mechanisms(different Hen Vm size).The helium retention amount of 80 keV is lower than that of 180 keV,and a saturation limit associated with the irradiation of 80 keV has been reached.The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.

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.

Integrated System for the Rapid Polycyclic Aromatic Hydrocarbons Extraction from Aqueous Samples and Their Consecutive Thermal Desorption Prior to Gas Chromatography Analysis

This paper describes for the first time the extraction followed by thermal desorption of polycyclic aromatic hydrocarbons (PAHs) spiked water samples in a microfluidic silicon device. Thanks to the integration into an original system composed of a micropump, microvalves, and an optimized thermal management, the entire protocol is automated and combines the extraction, the drying and the desorption in less than 25 min before sending the sample to a GC-FID system. Repeatable recovery yields have been determined for 1 μg/L spiked water samples and the analysis of PAHs in a natural water spiked sample has been demonstrated without loss of performance compared to purified water samples. Compared to other extraction techniques, this system has the advantage of reduced footprint, reduced energy consumption and no solvent use.

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.

基于全生命周期的污油泥热脱附处理技术评价

基于全生命周期评价(LCA)软件eFootprint和国内典型污油泥热脱附处理实际,从绿色和可持续性两个方面对污油泥热脱附技术进行评价。结果表明:污油泥热脱附处理过程中,主要评价指标按所产生的环境影响由大到小排列依次为可吸入无机物(RI)、富营养化潜值(EP)、竞争-土地使用(CLU)、臭氧层消耗潜值(ODP)和水资源消耗(WU);回收油和天然气是初级能源消耗(PED)、非生物质资源消耗潜值(ADP)、WU、全球增温潜势(GWP)、ODP等11项评价指标的主要贡献因素,蒸汽是影响RI的最主要因素;污油泥热脱附处理产生的回收油能够抵消热脱附处理过程的部分能源和资源消耗,从而减小PED、ADP、GWP等评价指标的数值;为了进一步提升污油泥热脱附处理技术的绿色和可持续性,建议提高能源效率,减少蒸汽消耗,回收蒸汽余热,优化尾气净化系统和器具清洗系统,减少废水排放和水分挥发。

搅拌子吸附-热脱附-气相色谱-质谱法分析北京大气中33种多氯联苯

用包覆聚二甲基硅氧烷(PDMS)吸附层的搅拌子作被动大气采样器,建立了搅拌子吸附-热脱附-气相色谱-质谱法(SBSE-TD-GC-MS)分析大气中多氯联苯(PCBs)的方法。优化后的热脱附温度为280℃,热脱附时间为6 min,聚焦冷阱的温度为-40℃,33种PCB单体的热脱附残留比例低于7%。验证了方法的线性、精密度和重复性。标准曲线5个点线性关系良好,33种PCB单体的相关系数r>0.998。方法精密度验证的相对标准偏差(RSD)为0.79%~20.2%(n=8),日内重复性实验的RSD为0.43%~29.8%(n=10),日间重复性实验的RSD为3.20%~29.6%(n=20),方法检出限(LOD)为0.01~2.51 pg,回收率为98%±18%。将建立的方法用于北京大气中PCBs的分析。检出8种PCB单体,质量为2.94~129 pg。在32 d的采样周期内PCB-52、PCB-123、PCB-155一直处于线性吸附阶段,而PCB-1和PCB-3经过了线性吸附阶段、曲线吸附阶段和平衡阶段。研究结果表明,SBSE-TD-GC-MS可以用于大气中PCBs的样品采集和快速分析。

动态顶空萃取结合气相色谱-嗅觉测量-质谱联用技术解析不同品种烘青绿茶的挥发性成分

通过优化茶叶用量、捕集温度、孵化温度、吹扫总流量、吹扫速率以及干燥速率等动态顶空(dynamic headspace,DHS)提取参数,建立了基于DHS萃取联合热脱附/气相色谱-质谱的烘青绿茶挥发性成分的最优提取及分析方法,并结合气相色谱-嗅觉测量-质谱(gas chromatography-olfactometry-mass spectrometry,GC-O-MS)联用技术系统解析不同品种烘青绿茶的关键嗅感物质。结果表明,当茶叶用量为200 mg、捕集温度为70℃、孵化温度为70℃、吹扫总流量为350 mL、吹扫速率为10 mL/min、干燥速率为10 mL/min时,萃取效果最佳。继而对3个代表性品种制备的烘青绿茶中的挥发性成分进行提取分析,共鉴定出74种挥发性成分;多元统计分析结果表明,不同品种烘青绿茶的香气化学物质基础差别迥异,共18种化合物被鉴定为关键差异性挥发性成分,其中异亚丙基丙酮及芳樟醇在龙井43烘青绿茶中含量最高,6-甲基-5-庚烯-2-酮、辛醛、环己酮、苯乙酮、古巴烯、表荜澄茄油烯醇等在福鼎大白茶中含量最高。进一步的GC-O-MS分析共识别出烘青绿茶中的28种嗅感物质,它们主要呈现青香、清新、花果香、草本香、木香、甜香等气味属性,其中花果香属性的香气强度总和最高,青香、清新属性次之。综合分析结果表明,芳樟醇、菖蒲烯、δ-杜松烯、6-甲基-5-庚烯-2-酮和辛醛是3个不同品种烘青绿茶间的关键差异性嗅感物质,芳樟醇在龙井43烘青绿茶中贡献显著,而后四者对福鼎大白茶烘青绿茶的香气品质形成贡献显著。

热脱附对多环芳烃和重金属复合污染土壤的影响

热脱附技术被广泛用于污染场地修复,但其对多环芳烃(PAHs)与重金属复合污染土壤的综合影响仍不清楚。选用PAHs和重金属复合污染模拟土壤,探究热脱附温度(220~400℃)和停留时间(5~60 min)对土壤中PAHs的影响,分析空气与氮气气氛下热脱附温度(310、340和370℃)对土壤中重金属Cu、Pb、As和Cd形态分布的影响。结果表明:随热脱附温度和停留时间的增加,土壤中PAHs去除率显著增加;低环PAHs占比逐渐减少,而高环PAHs占比逐渐增加。在2种气氛热脱附后,Cu、Pb和As弱酸提取态占比略有增加,而Cd弱酸提取态占比显著降低;可还原态和可氧化态的转化趋势具有差异性。随着热脱附温度的升高,Cu、Pb、As和Cd 4种重金属的残渣态占比均逐渐增加,说明热脱附有利于4种重金属的固定。相较于空气,氮气条件下4种重金属可氧化态和残渣态占比均增加;Cu和Pb可还原态占比显著降低,而As可还原态占比有所降低,Cd可还原态占比变化不大。氮气更有利于Cu、Pb和Cd的稳定;相反,空气更有利于As的稳定。

响应面分析法优化减压热脱附技术处理油基钻屑

采用减压热脱附技术处理油基钻屑,考察了热脱附温度、热脱附时间和系统真空压力对脱油率的影响,在此基础上,采用响应面分析法建立了各因素与脱油率之间关系的数学模型,优化了工艺参数。实验结果表明,在热脱附温度350~450℃、系统真空压力-0.07~-0.09 MPa、热脱附时间60~90 min的条件下,脱油率可达98%以上。各因素对脱油率的影响依次为热脱附温度>系统真空压力>热脱附时间;在热脱附温度420℃、系统真空压力-0.08 MPa、热脱附时间80 min的最佳工艺条件下,平均脱油率为98.67%,与模型计算值(100%)仅相差1.33%,剩余固体的平均含油率为0.37%。回收油的组分与0号柴油基本一致,可用于配制钻井液。剩余固体中未发现重金属元素和放射性元素,能够满足《页岩气勘探开发油基岩屑处理方法及控制指标》(GB/T 41518—2022)中“可用于油气田建设基础材料”的要求。

X60、X70管线钢及其焊接接头氢脆敏感性的对比研究

目的开展电解渗氢管线钢及其焊接接头显微组织和力学性能研究,为掺氢天然气管线服役安全可靠性评估提供支持。方法X60、X70管线钢及其焊接接头试样在100mA/cm^(2)下进行24h电解渗氢后,开展有、无渗氢情况下相关试样的显微组织结构、氢热脱附、拉伸力学性能与断口形貌测试分析,揭示渗氢对X60、X702种管线钢及其焊接接头氢脆敏感性的影响规律。结果X60及X70管线钢以细小多边形铁素体为主,其焊缝和热影响区以粗大的粒状或板条贝氏体为主。相对于X70管线钢,其焊接接头具有更高的氢渗透性和稳定性。渗氢导致X60、X70管线钢及其焊接接头试样的强度与塑性降低,渗氢X70焊接接头力学性能衰减最为明显,拉伸断口呈准解理断裂特征。结论X70管线钢的氢脆敏感性高于X60管线钢,管线钢焊接接头的氢脆敏感性高于母材。

有机污染场地原位修复过程的地球物理动态监测与分析

有机污染场地原位修复过程的动态监测是评估修复进程和效果的重要环节,监测方法的选择直接影响修复效率及费用。本研究利用高密度电阻率法,结合常规监测井数据,全面刻画了原位热强化氧化耦合修复过程。结果显示,场地内电阻率与水化学、地下水位、污染物含量和温度数据相互验证,实现了点面信息结合。研究发现,在原位热修复过程中,场地内地层电阻率会随温度升高而降低。基于温度与电阻率的经验关系,本文提出了污染物含量变化对电阻率的影响系数,得出影响系数随污染物含量的不断减小而增加。本研究还推算出原位热修复过程中温度及污染物含量的分布,即浓度随温度的不断升高而降低。针对原位氧化修复过程,电阻率变化有效刻画了原位氧化修复中过硫酸钠及水的动态注入过程。研究充分体现了地球物理方法在原位修复监测中的优势,可为有机污染场地原位修复过程精准、高效及低成本的动态监测提供重要参考。

MIL-101(Cr)吸附/热脱附-气相色谱-质谱法检测苯系和氯代VOCs

以金属有机骨架材料MIL-101(Cr)为填料构建了一种新型吸附采样管,将其与热脱附-气相色谱-质谱联用实现了15种典型苯系和氯代挥发性有机物(VOCs)的检测。结果显示,15种VOCs在0~100 ng范围内呈良好的线性关系,相关系数(r2)达到0.99以上,检出限为0.7~1.9 ng。在5、30、70 ng添加量下,15种VOCs的平均回收率分别为86.0%~126%、91.7%~133%和77.6%~135%,相对标准偏差(RSD)分别为6.6%~18%、2.9%~20%和1.3%~20%。MIL-101(Cr)填料吸附管测试稳定性和不同批次吸附管重复性的RSD分别为0.50%~14%和0.30%~18%。MIL-101(Cr)填料吸附管基于质量更少的填料实现了对苯系和氯代VOCs更高效的吸附、富集和热脱附,有助于降低吸附采样管的气体穿透风险。该研究拓展了MOFs材料在环境检测领域的实际应用场景。

土壤异位间接热脱附技术应用研究与优化策略分析

针对我国12个省份的16个典型异位间接热脱附工程进行调研,分析异位间接热脱附技术的应用特征。结果表明,异位间接热脱附修复的目标污染物主要包括苯系物、氯代烃、多环芳烃、农药和石油烃等5种类型,污染物的最大超标倍数为7.60~4 409.09,热脱附最高温度范围为350~750℃,热脱附停留时间不超过30 min的工程占比为94%,热脱附修复综合成本为734~1 400元/m^(3),平均值为1 210元/m^(3)。同时,对热脱附设备在工程应用中的运行问题进行识别,发现存在热脱附设备运行稳定性差、制约处理能力,热脱附系统能量利用效率低、影响处理成本等问题。需进一步加强热脱附过程传热传质机理研究,提升设备集成化与标准化水平,提高能量利用效率。

新型碳分子筛在工业源挥发性有机物测定中的应用

制备新型碳分子筛Scalpha 1500,并采用Scalpha 1500代替进口碳分子筛Carboxen 1000组合成新的吸附管(CB1500吸附管)。采用扫描电子显微镜(SEM)、X射线能谱法(EDS)、氮气吸附-脱附等温线法和X射线衍射法(XRD)对两种碳分子筛的表观形貌、元素组成、孔隙结构以及晶相构成进行表征。利用热脱附-气相色谱-质谱法(TD-GC-MS),比较CB1500吸附管与HJ 734-2014推荐组合三吸附管(Carbon 300吸附管)对挥发性有机物(VOCs)的测试性能。吸附管的最优解吸参数为解吸温度300°C、解吸时间6 min、解吸流量50 mL·min^(−1),在该条件下,两种吸附管具有相近的本底值、解吸性能及穿透性能。结果表明,CB1500及Carbon 300吸附管中24种VOCs的质量在5~100 ng内与对应的峰面积呈线性关系,检出限(3S/N)分别为0.4~4.8μg·m^(−3)和0.4~4.6μg·m^(−3)。按照标准加入法进行回收试验,CB1500及Carbon 300吸附管中24种VOCs的回收率分别为93.0%~107%和92.0%~113%,除乳酸乙酯外其他23种VOCs测定值的相对标准偏差(n=7)均小于5.0%。采用两种吸附管对广州某工业园区固定污染源废气进行采样分析,CB1500及Carbon 300吸附管中24种VOCs均有检出,检出量分别为2.3~21.1μg·m^(−3)和2.4~21.3μg·m^(−3)。上述结果说明新型碳分子筛Scalpha 1500可代替进口碳分子筛Carboxen 1000组合成新的吸附管采集VOCs,可极大降低采样成本。

煤制气遗留场地修复后再开发安全利用评估

随着社会经济发展和城镇建设加快,原有土地使用性质发生改变,其中工业遗留场地的污染物可能对土壤和地下水造成污染。但由于修复技术的局限性以及水文地质的复杂性,修复后场地仍然可能存在不利于安全利用的物质残留或异味等风险隐患。为了进一步完善污染地块修复后再利用评价方法,对可能存在的污染风险进行识别,现选取了一块经原位化学氧化和原位热脱附修复后的煤制气遗留场地,从感官可接受度、工程安全性和环境质量3个方面系统全面地评估场地修复后再开发安全利用的适宜性。评估结果表明,在感官可接受度方面,硫化氢的质量浓度是其嗅阈值的1.6~4.8倍,氨、甲苯和三氯甲烷质量浓度均低于其嗅阈值,臭气浓度低于检出限,感官可接受程度高;在工程安全性方面,地块经原位热脱附和原位化学氧化修复后,基本土性参数、压缩系数和渗透系数未发生明显改变,但是原位化学氧化区MH2点位浅层土壤硫酸盐残留浓度达到中腐蚀等级;在环境质量方面,修复后场地土壤中和地下水中污染物的质量浓度均低于相应评价标准限值。在场地后期开发建设中,应进一步对土壤中硫化氢气体和土壤硫酸盐腐蚀性进行监测,确保地块安全开发利用。研究结果可为其他污染地块修复后的再利用提供有效、科学的指导。

低温热解吸和高温热脱附对土壤三氯乙烯修复效果研究

针对上海某TCE污染场地土壤,采用Box-Behnken模型因子优化,获得热处理技术应用于TCE修复工程的技术参数。结果表明,“低温热解吸+生石灰”工艺适用于低浓度TCE污染土,去除率与生石灰的投加量呈正相关,当温度达到45℃时,残留TCE浓度为0.408 mg/kg,达到修复目标;热脱附技术适用于中高浓度TCE污染土,最优拟合模型为二次项模型,R^(2)=0.92;TCE污染浓度对土壤TCE残留浓度呈强正相关,脱附时间呈负相关,含水率呈弱负相关,各因子对热脱附处理后土壤TCE残留浓度的影响顺序为:TCE污染浓度>脱附时间>含水率。

PAHs污染土壤热脱附过程关键影响因素及脱附动力学研究

土壤多环芳烃(PAHs)污染已严重威胁生态环境安全和人类生命健康。通过异位热脱附试验探究了PAHs初始浓度、土壤含水率和土壤粒径对脱附效率的影响,并采用一级、二级动力学和指数衰减模型对PAHs热脱附过程进行拟合,以探究土壤中PAHs热脱附的去除机制。结果表明,在同等条件下,随着PAHs初始浓度的增加,脱附效率随之升高,且在热脱附20~40 min时提高初始浓度可明显提高PAHs的去除率。土壤含水率对于PAHs不同组分的作用具有一定的差异性,当土壤含水率为16%,萘(Nap)、菲(Phe)和蒽(Ant)达到最佳去除率,而荧蒽(Fla)和芘(Pyr)最大去除率对应的土壤含水率为13%。在相同脱附条件下,土壤粒径越小,土壤中PAHs的去除率越高。研究发现指数衰减模型对PAHs各组分的脱附过程具有更好的拟合效果。土壤中PAHs热脱附主要分为两个阶段:(1)PAHs受到土壤中水的蒸发作用从土壤颗粒表面快速蒸发;(2)PAHs的蒸发速率受到土壤孔隙内部扩散的限制,以非常缓慢的速度从土壤中脱除。