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聚苯胺碳化产物表面和体相结构表征 总被引:3,自引:2,他引:1
测试分析了聚苯胺树脂碳化产物表面和体相结构。结果表明聚苯胺树脂碳化产物比表面积随碳化温度升高而下降。在700℃和1000℃还原性气氛中碳化处理的样品与620℃处理的样品相比,比表面积分别下降了约8.3%和33.7% 。在相同温度条件下,惰性气氛中碳化处理的样品比表面积低于还原性气氛中碳化处理的样品。聚苯胺树脂碳化产物表面中的氮主要以两种不同的基团结构形式存在,并且树脂碳化产物表面的氮含量随着碳化处理温度升高逐渐降低。聚苯胺620℃碳化处理时主要是树脂中的含氮基团发生变化,而其他结果基团变化较小。700℃碳化处理后则开始大规模碳化裂解。但1000℃碳化处理后的样品仍含有少量的碳氢键和氮氢键。1000℃碳处理的树脂碳化样品开始形成多碳稠环,并向有序化方向转变。 相似文献
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锂离子电池新型树脂碳电极材料的研究 总被引:1,自引:0,他引:1
测试分析了碳化处理条件对糠醇树脂碳化产物组成,结构和电化学性能的影响,结果表明:620℃碳化处理的样品出现了明显尖锐的(100)晶面特征衍射峰。同时还发现了(110)和(006)晶面特征衍射峰,表现糠醇树脂是一种较易石墨化的树脂材料,碳化样品比表面积均随着处理温度升高而下降。处理气氛对碳化产物比表面积的影响表现得更为强烈。700℃惰性气氛中碳化处理的样品与还原性气氛中处理的样品相比,比表面积降低了约61.5%,实验结果还发现620℃-1300℃范围内处理的糠醇树脂碳化样品组装的锂离电池都表现出了相对较高的充放电容量,其中700℃碳化处理的样品组装的锂离子电池充放电容量最高,实验结果还表明树脂碳化产物的比表面积是影响电池充放电性能的重要因素,碳化产物的比表面积越大,电池的充放电容量就越高。 相似文献
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用X射线衍射法分析了聚苯乙烯阳离子交换树脂碳化产物石墨化度和微观结构参数,结果表明聚苯乙烯阳离子交换树脂在1000℃以下碳化处理的样品,石墨化程度都很低,属于在中低温条件下较难石墨化处理的树脂样品;H型树脂碳化产物的晶面层有着碳化处理温度升高而依次减小,并且(002)晶面层间距减小速度快于(100)晶面;H型树脂在低温碳化处理条件下,主要是在二维平面结构上演变成石墨微晶,只有碳化处理温度较高时,平面结构的石墨微晶才相互调整,形成纵向平行有序的微晶体;树脂掺杂金属离子后,有利于树脂在碳化过程中形成的石墨微晶层片纵向有序排列;掺杂不同金属离子的树脂碳化样品,在结构参数方面都明显不同于未掺杂的H型树脂碳化样品。 相似文献
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采用固相微萃取与气相色谱串联质谱联用,建立了快捷测定大气细颗粒物(PM2.5)中16种优控多环芳烃的方法.目标物先用二氯甲烷富集浓缩,然后用100 μm聚二甲基硅氧烷萃取纤维,通过超声萃取方式,在60℃条件下,萃取30 min.在优化的在多反应监测模式下,方法回收率在56.8% ~ 106.0%之间,检出限为0.022~0.056 ng/m3.应用此方法检测了清华大学采样点采取的2013年1月1到15日北京PM2.5空气样品中的16种PAHs,实验结果表明,PAHs总质量浓度在290~1812 ng/m3之间,其中四环PAHs的总质量浓度最大(145 ~937 ng/m3),其次是五环PAHs(总质量浓度81.1~664.5 ng/m3),分子质量浓度较高的依次是荧蒽、芘、苯并(b)荧蒽、(蕴)、苯并(a)芘、苯并(k)荧蒽、苯并(a)蒽和菲,PAHs的污染主要来源于化石燃料燃烧和机动车排放. 相似文献
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制备了La3 掺杂的聚苯乙烯阳离子交换树脂 ,对其进行碳化处理 ,分析了树脂碳化产物的组成和结构 ,并进一步考察了树脂碳化产物作为二次锂离子电池碳电极材料的电化学行为。La3 掺杂的聚苯乙烯阳离子交换树脂碳化产物与相同处理条件下的未掺杂离子的树脂碳化样品相比 ,3种非C元素H ,O ,S的含量都发生了明显的变化 ,其中H ,O含量有所提高 ,而S含量则有所降低。La3 掺杂的聚苯乙烯阳离子交换树脂在碳化过程中更易形成直径较大的层片石墨微晶结构。电化学实验测试结果进一步证明 :La3 掺杂有效地提高了树脂碳化产物作为锂离子电池碳负极材料的电化学性能。掺杂La3 的树脂碳化样品制备的锂离子电池碳电极材料与未掺杂La3 的树脂碳化样品制备的碳电极材料相比 ,充放电容量平均提高了约 30mAh·g- 1。 相似文献
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A new sampling method of ambient air analysis using carbonized fibrous resin as a sorbent for polycyclic aromatic hydrocarbons(PAHs) was reported.The physical and chemical properties of the carbonized fibrous resins were measured.The sample pretreatment with ultrasonic extraction and subsequent clean-up elution through a silica gel column was optimized.The suitable ultrasonic extraction conditions were selected as follows:resin weight was 1.5g,ultrasonic extraction time 20min,volume of extraction solvent 100 ml and extraction operation times 2-3.The concentrated extractable organic matter was submitted to next step of clean-up procedure of adsorption chromatography on silica gel column/n-hexane and a mixture of dichloromethene:n-hexane solution 2:3(v/v).The PAHs fractions in the real samples from Changzhou,China were particularly analyzed using GC-MS data system and the data of mass spectra,retention times and scan numbers of the real samples were compared with that of the standards of 16 PAHs listed by the US EPA as “priority pollutants” of the environment. The pretreatment of samples of ambient air with carbonized fibrous resin as a sorbent for PAHs is proved to be reliable and might be used for the procedure of the determination of PAHs in atmospheric environment. 相似文献
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Summary A new, molecular diffusion-based, sampling device (Analyst 2) has been used for the determination of semi-volatile PAHs in
air. It has been developed from a previous model (Analyst), which is suitable for volatile hydrocarbons. The new model is
capable of collecting enough gaseous PAHs for GC-MS analysis of enriched samples after 2 months exposure to both urban and
suburban air. The adsorbent material adopted for enriching PAHs from air (Carbopack C) gives good recoveries of analytes from
naphthalene to chrysene when a single solvent extraction is run at ambient temperature.
The results of an experiment for assessing the internal consistency of this device are presented here. Data collected indicate
that the “uptake rate” is constant for a 6-month sampling period. Results are also presented and discussed for indoor and
outdoor determination of volatile PAHs, collected at both urban and suburban sites over a 12-month period in 2-monthly steps. 相似文献
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Nonpolar organic compounds (NPOCs) in ambient particulate matter (PM) commonly include n-alkanes, branched alkanes, hopanes and steranes, and polycyclic aromatic hydrocarbons (PAHs). The recent development of thermal
desorption-gas chromatography/mass spectrometry (TD-GC/MS) has greatly reduced time and labor in their quantification by eliminating
the laborious solvent extraction and sample concentration steps in the traditional approach that relies on solvent extraction.
The simplicity of the TD-GCMS methods has afforded us concentration data of NPOCs in more than 90 aerosol samples in two aerosol
field studies and 20 vehicular emissions-dominated source samples in Hong Kong over the past few years. In this work, we examine
the interspecies relationships between select NPOCs and their concentration ratios to elemental carbon (EC) among the ambient
samples and among the source samples. Our analysis indicates that hopanes were mainly from vehicular emissions and they were
significantly oxidized in ambient PM. The hopane/EC ratio in ambient samples was on average less than half of the ratio in
vehicular emissions-dominated source samples. This highlights the necessity in considering oxidation loss in applying organic
tracer data in source apportionment studies. Select PAH/EC ratio–ratio plots reveal that PAHs had diverse sources and vehicular
emissions were unlikely a dominant source for PAHs in Hong Kong. Biomass burning and other regional sources likely dominated
ambient PAHs in Hong Kong. 相似文献
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Ho SS Yu JZ Chow JC Zielinska B Watson JG Sit EH Schauer JJ 《Journal of chromatography. A》2008,1200(2):217-227
Thermal desorption coupled with gas chromatography/mass spectrometry (TD-GC/MS) is an alternative to solvent extraction (SE)-based GC/MS (SE-GC/MS) for the analysis of non-polar organic compounds in filter or impactor-collected aerosols. TD-GC/MS has no sample pretreatment and requires a small filter aliquot for detecting individual organic compounds. The performance of an in-injection port TD-GC/MS is evaluated for polycyclic aromatic hydrocarbons (PAHs), n-alkanes, iso-/anteiso-alkanes, hopanes, steranes, branched alkanes, cyclohexanes, alkenes, and phthalates in standards and ambient air samples. Replicate analysis for 132 organic compounds showed relative standard deviations <10%, with the majority <5%. Accuracy for 15 PAHs, determined with NIST standard reference material (SRM) 1649a urban dust, was within +/-5% of the certified values. TD-GC/MS and SE-GC/MS method comparisons for 14 Hong Kong ambient samples agreed within 11% for 106 non-polar compounds. For 19 Tong Liang, China samples, agreement was within 13% for 23 PAHs. 相似文献
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A method for measuring polycyclic aromatic hydrocarbons (PAHs) in ambient air is described. The particulate matter is collected on fibre-glass filters. The loaded filters are placed in tetrahydrofuran and the PAHs dissolved with the aid of ultrasonics and analysed by high-performance liquid chromatography on a reversed-phase column with a methanol-water mixture as mobile phase. The PAHs are detected by use of a UV-detector and the 254-nm mercury emission line. The method is rapid and adequate for measuring about 15 PAH-components in ambient air. 相似文献
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Summary Daily samples of airborne particulates (143) were collected along the year in La Spezia (Italy). Seasonal variations of atmospheric PAH concentrations, with highest winter values, have been observed. The concentration of PAHs was found to correlate negatively with the mean ambient temperature during the sampling period. Volatilization, photodegradation and seasonal modifications of emissions from urban traffic were found to be a possible explanation of this phenomenon. 相似文献
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Jane C. Chuang Jeanette M. Van Emon Nadia Junod Nancy K. Wilson 《Analytica chimica acta》2003,486(1):31-39
Polycyclic aromatic hydrocarbons (PAHs) are frequently encountered in the environment and may pose health concerns due to their carcinogenicity. A commercial enzyme-linked immunosorbent assay (ELISA), was evaluated as a screening method for monitoring PAHs at contaminated sites. The ELISA was a carcinogenic PAH (C-PAH) RaPID assay testing kit that cross-reacts with several PAHs and utilizes benzo[a]pyrene (BaP) as a calibrator. Soil samples were extracted with 50% acetone in dichloromethane (DCM) for analysis by ELISA and gas chromatography-mass spectrometry (GC-MS). The overall method precision was within ±30% for ELISA and within ±20% for GC-MS. Recovery data for spiked soils ranged from 46 to 140% for BaP as determined by ELISA. Recoveries data of the GC-MS surrogate standards, 2-fluorobiphenyl and chrysene, were greater than 70%. The GC-MS procedure detected a total of 19 priority PAHs (2-6-ring PAHs) including seven probable human carcinogens (4-6-ring B2-PAHs). The ELISA results were compared to GC-MS summation results for the total 19 target PAHs as well as for the subset of the seven B2-PAH compounds. For all soil samples, the PAH concentrations derived from ELISA were greater than the sum of B2-PAH concentrations obtained by GC-MS. ELISA determinations were also frequently greater than the results obtained by GC-MS for the total 19 PAH compounds. This discrepancy can be expected, since the ELISA is a screening assay for the detection of several related PAHs while the GC-MS procedure detects priority PAH compounds. Thus, only a subset of PAHs (e.g. 19 PAHs) in the soil samples were measured by GC-MS while additional PAHs, including alkylated PAHs, and PAH derivatives have been demonstrated to be cross-reactive in the C-PAH ELISA. Results of paired tests show that the PAH data from ELISA and GC-MS methods are significantly different (P<0.001), but highly correlated. The ELISA data had a strong positive relationship with the GC-MS summation data for the B2-PAHs as well as for the 19 PAHs targeted by the GC-MS method. Results indicate that the ELISA may be useful as a broad screen for monitoring PAHs in environmental samples. 相似文献
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Reddithota J. Krupadam Bhagyashree Bhagat Muntazir S. Khan 《Analytical and bioanalytical chemistry》2010,397(7):3097-3106
A method based on solid--phase extraction with a molecularly imprinted polymer (MIP) has been developed to determine five
probable human carcinogenic polycyclic aromatic hydrocarbons (PAHs) in ambient air dust by gas chromatography-mass spectrometry
(GC-MS). Molecularly imprinted poly(vinylpyridine-co-ethylene glycol dimethacrylate) was chosen as solid-phase extraction
(SPE) material for PAHs. The conditions affecting extraction efficiency, for example surface properties, concentration of
PAHs, and equilibration times were evaluated and optimized. Under optimum conditions, pre-concentration factors for MIP-SPE
ranged between 80 and 93 for 10 mL ambient air dust leachate. PAHs recoveries from MIP-SPE after extraction from air dust
were between 85% and 97% and calibration graphs of the PAHs showed a good linearity between 10 and 1000 ng L−1 (r = 0.99). The extraction efficiency of MIP for PAHs was compared with that of commercially available SPE materials—powdered
activated carbon (PAC) and polystyrene-divinylbenzene resin (XAD)—and it was shown that the extraction capacity of the MIP
was better than that of the other two SPE materials. Organic matter in air dust had no effect on MIP extraction, which produced
a clean extract for GC-MS analysis. The detection limit of the method proposed in this article is 0.15 ng L−1 for benzo[a]pyrene, which is a marker molecule of air pollution. The method has been applied to the determination of probable carcinogenic
PAHs in air dust of industrial zones and satisfactory results were obtained. 相似文献
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Determination of trace PAHs in seawater and sediment pore-water by solid-phase microextraction (SPME) coupled with GC/MS 总被引:2,自引:0,他引:2
Lee Franck Sen-Chun 《中国科学B辑(英文版)》2006,49(6):481-491
A fast and reliable method for the determination of trace PAHs (polynuclear aromatic hydrocarbons) in seawater by solid-phase microextraction (SPME) followed by gas chromatographic (GC) analysis has been developed. The SPME operational parameters have been optimized, and the effects of salinity and dissolved organic matter (DOM) on PAHs recoveries have been investigated. SPME measures only the portion of PAHs which are water soluble, and can be used to quantify PAH partition coefficient between water and DOM phases. The detection limits of the overall method for the measurement of sixteen PAHs range from 0.1 to 3.5 ng/g, and the precisions of individual PAH measurements range from 4% to 23% RSD. The average recovery for PAHs is 88.2±20.4%. The method has been applied to the determination of PAHs in seawater and sediment porewater samples collected in Jiaozhou Bay and Laizhou Bay in Shandong Peninsula, China. The overall levels of PAHs in these samples reflect moderate pollution compared to seawater samples reported elsewhere. The PAH distribution pattern shows that the soluble PAHs in seawater and porewater samples are dominated by naphthalenes and 3 ring PAHs. This is in direct contrast to those of the sediment samples reported earlier, in which both light and heavy PAHs are present at comparable concentrations. The absence of heavy PAHs in soluble forms (<0.1-3.5 ng/L) is indicative of the strong binding of these PAHs to the dissolved or solid matters and their low seawater solubility. 相似文献
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A low-pressure gas chromatography-ion trap mass spectrometry (LPGC-ITMS) method was investigated to shorten the analysis time for 18 US Environmental Protection Agency priority listed polycyclic aromatic hydrocarbons (PAHs). Their elution was optimised with a short, wide-bore column coupled to a deactivated capillary at the inlet end and with a long, conventional column to compare their analytical performance. The analytical figures of merit under optimal LPGC-ITMS conditions were determined with respect to chromatographic separation, S/N ratio, limit of detection and precision. The peak width at half height of 1.5s matched the ITMS duty cycle. Up to 16 PAHs in the molecular weight (MW) range of 128-278 Da could be separated in a very short time, i.e. less than 13 min using LPGC-ITMS, whereas with conventional GC-MS, it took approximately 40 min. However, LPGC-ITMS has a limited loss of separation power compared to that of conventional GC-MS due to the occurrence of three critical pairs for high-MW PAHs. For a practical evaluation, the LPGC-ITMS approach was applied to the determination of PAHs in gas and aerosol phase samples collected in the ambient air of Hasselt, Belgium. 相似文献