Carbon Blacks Produced by Thermal Plasma: the Influence of the Reactor Geometry on the Product Morphology

Carbon black (CB) nanopowders were obtained by plasma decomposition of methane at various flow rates using inductively coupled thermal plasma torch system of 35 kW. Nitrogen was also introduced in some experiments along with the methane. Using a cylindrical shape reactor the obtained powders were composed mainly of spherical particles, non-uniform in terms of particles size with diameters between 30 and 150 nm. The shape and size of this reactor resulted in the presence of recirculation areas enabling the formation of large CB particles and other secondary volatile compounds. Changing the reactor to a conical geometry resulted in the production of CB powders showing a crystalline and flake-like morphology made of sheets having 6–16 graphitic planes. The conical shape avoids the presence of recirculation areas and promotes the formation of a uniform powder morphology throughout the reactor.     

热解吸–气质联用法测定纺织品中有机挥发物的含量

采用热解吸–气质联用法测定纺织品中有机挥发物氯乙烯、1,3-丁二烯、甲苯、4-乙烯基环己烯、苯乙烯、4-苯基环己烯的含量。吹扫载气N2流量为30 m L/min,100℃吹扫顶空腔30 min,然后于290℃解吸吸附管10 min。色谱柱为DB–624柱,初始柱温35℃,保持5 min,以10℃/min升至240℃,保持10 min。检测上述6种有机物的线性范围分别为21.13~426.26,21.12~422.49,4.22~211.00,4.10~204.85,2.10~209.70,4.43~221.30μg/m L,线性相关系数均大于0.99。3个添加水平的平均回收率为88.8%~110.2%,测定结果的相对标准偏差为1.95%~6.59%(n=4)。该方法重现性好,测量结果准确,可作为纺织品质量控制的参考方法。     

高温热脱附技术对柴油机尾气颗粒物中小分子易挥发组分的分析研究

柴油机排放的颗粒物含量很高,约为汽油机的30～80倍[1].颗粒物中吸附的有机化合物可以诱发人类发生癌变和呼吸系统的疾病,因而被认为是对人类健康造成不利影响的最大因素之一.     

热脱附-单体稳定同位素技术测定挥发性有机物

采用热脱附与稳定同位素质谱联用技术分析了城市不同源及大气环境中挥发性有机物排放的单体同位素特征。系统考察了样品进样量、进样方式和样品分离度对同位素分馏影响情况。使用填有Tenax TA的吸附管采集汽油车尾气、汽油挥发、柴油车尾气、柴油挥发、溶剂挥发和餐饮油烟等污染源,以及城市不同功能区的挥发性有机物(VOCs)样品,不同污染源中挥发性有机物的稳定碳同位素δ13C值不同,97#汽油车尾气的δ13 C值偏重,平均值为-25.84‰,富集13 C;餐饮油烟的δ13 C值偏轻,平均值为-30.26‰。油品挥发比燃烧后以尾气的形式排放的苯系物δ13 C值重。厦门市各功能区挥发性有机物的δ13 C平均范围在-27.03‰~-25.40‰,接近于汽油和柴油挥发及尾气中的δ13 C值,表明厦门市空气中挥发性有机物以机动车排放源为主。     

热脱附-气相色谱-质谱法测定空气中挥发性有机物

提出了热脱附-气相色谱-质谱法测定空气中54种挥发性有机物含量的方法。用HP-INNOWAX毛细管色谱柱分离,电子轰击离子源全扫描和选择离子检测模式检测。54种挥发性有机物的方法检出限在0.11～0.28μg.m-3之间。回收率在85%～107%之间,相对标准偏差(n=7)小于15%。     

Carbon Nanoparticle Production by Inductively Coupled Thermal Plasmas: Controlling the Thermal History of Particle Nucleation

The process control for reproducibility, uniformity, and achievement of desired structures for carbon black generated in thermal plasma devices is studied in this paper through modeling, and correlated with experimental results. A numerical simulation of the flow and energy fields, stream function lines and the quench rates of the plasma gas in a conical shape reactor at different pressures was made. An argon plasma is used with highly diluted methane (0.6–7%) as the carbon precursor. The quench rates were studied in order to observe the flow development and hence the thermal history of particle nucleation. Three pressure cases of 20.7, 55.2 and 101.3 kPa and two plasma powers cases of 10 and 20 kW were studied. The modeling results enabled carbon nanoflakes production in the experimental tests performed on an inductively coupled thermal plasma system. Results indicate a robust process control enabling very little particle morphology variation over this wide range of reactor pressure values and varying plasma power, and a very high reproducibility of the particle morphologies obtained.     

热解吸-气相色谱法测定植物源挥发性有机物

以Tenax-TA、Carboxen 1000和Carbosieve SⅢ为采样管填充料,将植物源挥发性有机物吸附于采样管内,样品通过二次热解吸仪解吸后,随载气进入气相色谱仪,采用氢火焰离子化检测器(FID)测定,建立了利用二次热解吸仪与气相色谱联用技术测定植物挥发性有机物的分析方法。载气N2流速为30 mL/min,60℃下吹扫吸附管2 min,然后在250℃下解吸吸附管5 min,冷却1 min后,在275℃下解吸聚焦管3 min,样品经传输线进入气相色谱。气相色谱载气N2压力为190 kPa,FID检测器温度280℃;进样口温度225℃;初始柱温40℃,停留5 min,以2℃/min升温至120℃,保留1 min,然后以20℃/min升温至200℃,保留10 min。方法重现性好,精密度高,线性相关系数大于0.99;检出限均低于9×10-9g/L;解吸效率大于96%,适用于植物源挥发性有机物的测定。     

蓄热式热氧化炉处理农药行业挥发性有机废气

以农药行业挥发性有机废气为研究对象,优化了蓄热陶瓷体、切换阀、燃烧器等选材,以及安全控制和二噁英防治等方面设计参数,分析了特征污染物进出气浓度及去除效率,探讨了蓄热式热氧化(Regenerative Thermal Oxidizer,RTO)技术治理挥发性有机废气实际运行效果。结果表明甲苯和非甲烷总烃排放限值满足《大气污染物综合排放标准》(GB16297-1996)中表2二级标准,二氯乙烷排放限值满足美国EPA工业环境实验室和《制定地方大气污染物排放标准的技术方法》(GB/T3840-1991)计算值,二噁英排放限值满足《生活垃圾焚烧污染控制标准》(GB18485-2014)表4标准。RTO系统总投资150万元,年运行费用49.98万元,对该企业不构成经济负担。RTO适合农药行业挥发性有机废气处理,特别是对含低浓度卤素废气在保证净化效果的同时又可抑制二噁英产生。     

Carbon Nano-Flakes Produced by an Inductively Coupled Thermal Plasma System for Catalyst Applications

Carbon material was produced using an inductively coupled thermal plasma torch system of 35 kW and a conical shape reactor. The carbon nanopowders were obtained by plasma decomposition of methane at various flow rates and show a uniform microstructure throughout the reactor. The product has a crystalline graphitic structure, with a stacking of between 6 and 16 planes and a nano-flake morphology with particles dimensions of approximately 100 nm long, 50 nm wide and 5 nm thick. Nitrogen was also introduced in some synthesis experiments along with the methane precursor using flow rates of 0.1 and 0.2 slpm. The resulting product has the same structural properties and the nitrogen is incorporated into the graphitic structure through pyridinic type bonds.     

Activated Carbon Adsorption of Some Phenolic Compounds Present in Agroindustrial Wastewater

Single solute and simultaneous experimental adsorption isotherms of three phenolic compounds: gallic acid, p-hydroxybenzoic acid and syringic acid, have been investigated at 20, 30 and 40°C, using a bituminous coal based activated carbon. Regardless of temperature, the capacity of the activated carbon used to adsorb these compounds presented the following order: syringic acid > p-hydroxybenzoic acid > gallic acid. The increase of temperature slightly favored the adsorption capacity of the phenolic compounds. In binary and ternary component adsorption, experimental data suggest that interactions between adsorbates improve the adsorption capacity of some of the phenolic acid compounds. On the contrary, at high organic concentrations, adsorbed gallic acid was partially removed from the activated carbon surface because of the presence of the other components.     

Reactivity of Carbon Adsorbents Used to Determine Volatile Organic Compounds in Atmospheric Air

The surface reactivity of carbon adsorbents (carbon molecular sieves and graphitized carbons) used for analysis of volatile organic compounds in atmospheric air was studied using ¹⁸O as a labelling agent. The carbon adsorbent surface activated in a stream of inert gas at 350°C and then exposed to air is very active chemically. Apparently peroxide structures are formed. Owing to this activity the integrity of some analytes, for example dienes and alcohols, among others, is compromised. The active surface can react with the volatile organic compounds analyzed and even initiate free-radical polymerization. The consequences in analytical practice are discussed.     

吸附/一级热解吸/气相色谱联用测定室内空气中的挥发性有机物

本文以高聚物TenaxTA动态吸附,一级热解吸/毛细管气相色谱法联用测定室内空气中的挥发性有机物。优化了热解吸温度和热解吸时间,建立了苯、甲苯、乙酸正丁酯、乙苯、对二甲苯、苯乙烯、邻二甲苯、正十一烷等8种典型有机污染物的外标定量曲线,各化合物线性范围为103,相关系数R为0.9983～0.9999,最低检出浓度可达2×10-4mg/m3;考察了方法的重复性、热解吸率和残留率,并分析了实际空气样品。     

用吹扫捕集-热脱附-气相色谱-质谱法分析生活污水中挥发性有机物

介绍了用于分析生活污水中挥发性有机物的方法,分析物以吹扫捕集法取样,混合吸附剂富集,然后热脱附-气相色谱分析.混合吸附剂是由TenaxGC和活性炭组成,二者体积比为2∶1.对吹扫捕集流速和捕集时间进行了优化,并测定了标准分析物的回收率.利用该法,从生活污水中检出37种挥发性有机物,其中8种列在我国环境优先污染物名单中.     

用吹扫捕集—热脱附—气相色谱—质谱法分析生活污水中挥发性 …

介绍了用于分析考活污水中挥发性有机物的,分析物以吹扫捕集法取样,混合吸附剂富集,然后热脱附－气相色谱分析。混合吵附剂是由ＴｅｎａｘＧＣ和活性炭组成,二者体积比为２：１。对吹扫捕集流速和捕集时间进行了优化,并测定了标准分析物的回收率。利用该法,从生活污水中检出３７种挥发性有机物,其中８种列在我国环境优先污染物名单中。     

新型单壁碳纳米管采样吸附剂性能的评价

研究了单壁碳纳米管(SWCNTs)作为新型采样吸附剂的性能和效果,并应用于空气中挥发性有机化合物的分析测定。结果表明,单壁碳纳米管具有较大的比表面积,与经典Tenax TA吸附剂相比,对低碳数挥发性强的有机化合物回收率高,有更强的吸附能力;空白实验表明,SWCNTs易获得较低本底,具有化学惰性和疏水特性,采样时水的干扰小。当湿度增加时在误差允许的范围内准确度不受影响;实验测定具有较大的穿透容量和安全采样体积。将单壁碳纳米管吸附剂实际应用于大气中挥发性有机化合物的测定,通过与经典吸附剂Tenax TA相比,更适于采集大气中的挥发性有机化合物。     

水体中痕量挥发性有机物单体碳同位素组成分析

将固相微萃取(SPME)技术与冷阱富集系统相结合,对水体中痕量挥发性有机物进行了单体碳同位素分析,方法检测限较常规SPME提高了一个数量级。在优化的条件下,对20 μg/L的三氯乙烯/四氯乙烯和10 μg/L的苯/甲苯水溶液进行了单体碳同位素分析,相比于纯溶剂(液相)碳同位素值,顶空(气相)同位素分析误差不超过0.5‰,而样本标准偏差为0.3‰。对某受四氯乙烯污染的北京地下水进行了同位素测定,近污染源点(B408)与远污染源点(B230)四氯乙烯的碳同位素值(δ13C)分别为 -37.8‰和-34.45‰     

土壤中挥发性有机化合物的GC-MS测定

利用气相色谱－质谱联用技术，对某废弃化工厂原厂区及附近农田的土壤中可能存在的60种挥发性有机化合物进行了定性和定量分析；采用质量保证和质量控制步骤对分析结果进行监测，结果令人满意。     

热脱附-气相色谱质谱分析热环境下汽车沙发释放的挥发性有机物

汽车沙发部件在热环境中,会释放出许多挥发性有机物(VOC),污染环境,危害人体健康.本研究将汽车沙发放置在2 m3特制塑料采样袋中,在热环境下释放挥发性有机物,然后以Tenax管富集有机物,用热脱附-气相色谱质谱进行分析.结果表明:汽车沙发在热环境状态下,挥发出大量有机物,共定性检测出49种挥发性有机物(VOC),包括...     

水性涂料中挥发性有机化合物的气相色谱-质谱法测定

建立了内墙涂料中24种挥发性有机化合物(VOCs)的GC-MS检测方法,重点研究了现有检测方法分离度差和回收率低的问题,采用无水硫酸钠净化、二氯甲烷超声和膜过滤提取体系,改善了各种化合物的回收率,特别是提高了二元醇类化合物的回收率,优化后的实验条件下,样品的加标回收率为70%~94%,相对标准偏差不大于6.8%,检出限为3.1~10.6 mg/L。在30~300 mg/L范围内,方法的线性关系良好,相关系数大于0.99。该方法简便、快速、灵敏、精密度好,完全满足进出口水性涂料中常见的24种挥发性有机化合物的检测要求。     

Determination of Volatile Carbonyl Compounds in Cigarette Smoke by LC-DAD

An effective and rapid method, use of a 2,4-dinitrophenylhydrazine (DNPH)-treated Cambridge filter and high-performance liquid chromatography (HPLC) with diode-array detection (DAD), has been used for determination of low-molecular-mass carbonyl compounds in cigarette smoke. Different chromatographic mobile phases were investigated and the optimized mobile phase was a gradient prepared from water–acetonitrile–tetrahydrofuran (THF)–iso-propanol, 59:30:10:1 (v/v) (mixture A) and acetonitrile–water, 65:35 (v/v) (mixture B). Under the optimized chromatographic conditions, the 2,4-dinitrophenylhydrazones of formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, 2-butanone, and iso-butyraldehyde were separated completely in an 18 min chromatographic run. The concentration of acid, which has large effect on carbonyl-DNPH derivatization, was investigated by adding different volumes of perchloric acid. The DNPH-treated Cambridge filter was convenient and effective compared with conventional methods used to collect and derivatize the carbonyl compounds present in cigarette smoke. Validation of the method showed it to be effective, precise, accurate, and linear over the range of concentrations of analyzed.