Solubilization of selected polycyclic aromatic compounds by nonionic surfactants

Solubilization of selected polycyclic aromatic compounds (PAC) by biodegradable nonionic surfactants, Tergitol 15-S-X (X=7 or 9) and Neodol 25–7, was investigated and correlated with micellar properties of these surfactants. These PAC include dibenzofuran, phenanthrene, acenaphthene, fluoranthene, and 9-chloroanthracene. Tergitol surfactants are mixtures of secondary ethoxylated alcohols, and Neodol 25–7 is a mixture of similar species but has the alcohol group in the primary position. These surfactants have the same chain length of hydrophobic tails and similar numbers of ethylene oxides. The results show that the Neodol surfactant yields micelles having larger hydrophobic core volume and renders a higher solubilization capacity for the PAC solubilizates in comparison with Tergitol surfactants. In general, aggregation numbers and micellar sizes both increase at elevated temperatures still below the cloud point. The micellewater partition coefficients of these PAC by the nonionic surfactants were well correlated to their octanol-water partition coefficients. Moreover, an estimated log K _ow value of 9-chloanthracene is 4.78.     

Characteristics of polycyclic aromatic hydrocarbons emissions of diesel engine fueled with biodiesel and diesel

With mutagenic and carcinogenic potential, polycyclic aromatic hydrocarbons (PAHs) from mobile source exhaust have contributed to a substantial share of air toxics. In order to characterize the PAHs emissions of diesel engine fueled with diesel, biodiesel (B100) and its blend (B20), an experimental study has been carried out on a direct-injection turbocharged diesel engine. The particle-phase and gas-phase PAHs in engine exhaust were collected by fiberglass filters and “PUF/XAD-2/PUF” cartridges, respectively, then the PAHs were determined by a gas chromatograph/mass spectrometer (GC/MS). The experimental results indicated that comparing with diesel, using B100 and B20 can greatly reduce the total PAHs emissions of diesel engine by 19.4% and 13.1%, respectively. The Benzo[a]Pyrene (BaP) equivalent of PAHs emissions were also decreased by 15.0% with the use of B100. For the three fuels, the gas-phase PAHs emissions were higher than particle-phase PAHs emissions and the most abundant PAH compounds from engine exhaust were naphthalene and phenanthrene. The analysis showed that there was a close correlation between total PAHs emissions and particulate matter (PM) emissions for three fuels. Furthermore, the correlation became more significant when using biodiesel.     

Growth characteristics of polycyclic aromatic hydrocarbons in dimethyl ether diffusion flame

The growth characteristics of polycyclic aromatic hydrocarbons (PAHs) in laminar dimethyl ether (DME) diffusion flame were investigated experimentally, and we assumed that the growth of PAHs within the flame was predominantly due to methyl addition/cyclization (MAC) mechanism. Methane and propane laminar diffusion flames were also investigated for comparison, and their PAHs growth characteristics had been explained by reactions concerning acetylene and propargyl radical. Laser-induced fluorescence (LIF) and laser-induced incandescence (LII) techniques were used to measure the relative concentration of soot and PAHs, respectively. Two-dimensional images of the OH-LIF, PAHs-LIF, and LII from soot were measured in the test flames. Furthermore, to investigate the growth characteristics of the PAHs in the flames, the fluorescence spectra of the PAHs were measured at several heights in the flames, using a spectrograph. The molecular size of the PAHs was estimated based on an emission wavelength region of the PAHs-LIF that varied along with the PAH size. The results show that although the PAHs were widely distributed within the unburned region similar to that of the methane and propane flames, the intensity and detection region of LII were much smaller than that of the methane and propane flames. The PAHs-LIF spectra indicated that the growth of the PAHs within the DME flame was much slower than the methane and propane flames, and thus a large number of small PAHs were discharged into the OH region distributed around the outer edge of the flame.     

Photodegradation of polycyclic aromatic hydrocarbons in fossil fuels catalysed by supported TiO2

This paper describes the photodegradation behavior of polycyclic aromatic hydrocarbons present in different types of fossil fuels (commercial diesel, Arabian light crude, heavy fuel oil from the Prestige oil spill and coal from an abandoned coal dump) suspended in artificial seawater or ultrapure water, under irradiation in a stirred photochemical reactor for 14 days. The reactor was continuously fed with air from a compressor at a constant rate of 6 NL h⁻¹, and thin films of TiO₂ (anatase) supported on pyrex glass raschig rings were used as catalyst. Dark control samples were carried out simultaneously for all the experiments, and both phases, aqueous and organic, were analyzed by gas chromatography–mass spectrometry in the experimental and dark control samples, allowing to calculate a photodegradation ratio. The polycyclic aromatic hydrocarbons reached a high degree of photodegradation in the water-soluble fraction of the samples, but the organic fractions remained almost unaffected in most of the experiments. Some photodegradation products have been also identified in the aqueous and organic fractions of the samples.     

炼焦粉尘中多环芳烃的赋存特性

通过对焦化厂不同地点的粉尘采样,并进行粒度分级、超声波预处理及高效液相色谱分析,得到多环芳烃（PAHs）的赋存特性。在采集的样品中,地面除尘站粉尘仓的粉尘中PAHs的含量最高,达到1880．83μg／g。在焦化粉尘中,PAHs明显表现出对小粒径粉尘的富集特性,粉尘中单组分的PAHs含量差别较大,以4～6环的PAHs居多。此外,地面除尘站粉尘仓的粉尘样品中含有大量的苯并[a]芘。     

炼焦过程中多环芳烃产生特性的研究

对炼焦过程中产生排放的多环芳烃特性进行分析研究,利用超声波萃取和高效液相色谱技术,测定了单煤、配煤炼焦各阶段产生的16种PAHs的含量。研究结果表明,升温初期的1~4 h内PAHs的产生量最多,其中具有四环结构的居多,具有"三致"作用的苯并[a]芘超标排放,是PAHs的重要污染源之一。     

Degradation of polycyclic aromatic hydrocarbons by hydrogen peroxide catalyzed by heterogeneous polymeric metal chelates

Chelating sorbents with 8-hydroxyquinoline (IVa), 8-hydroxyquinoline-5-sulfonic acid (IVb), and tris(2-aminoethyl)amine (VI) ligands immobilized on macroporous methacrylate matrix were prepared and saturated with Co(II), Cu(II), and Fe(II). All these chelates catalyze cleavage of H₂O₂ yielding highly reactive hydroxyl radicals. All were able to degrade by this mechanism polycyclic aromatic hydrocarbons (anthracene, benzo[a]pyrene and benzo[k]fluoranthene). The most effective catalysts IVa-Fe, IVb-Fe, and VI-Cu (25 mg with 100 μmol H₂O₂) performed complete decomposition of 33 μg anthracene and benzo[a]pyrene during one 7-day catalytic cycle at 25 °C. The fastest decomposition proceeded during the 1st day of incubation; 75% of anthracene and 74% of benzo[a]pyrene were decomposed by IVb-Co within the first 24 h. More than 25% decomposition within the 1st day was also achieved with IVb-Fe, VI-Cu, IVa-Cu, and VI-Co for anthracene and more than 30% benzo[a]pyrene was decomposed by IVb-Fe, VI-Cu, IVa-Cu, and IVb-Cu during the same period. 1,4-Anthracenedione was the main product of anthracene oxidation by all catalysts. The catalysts were stable at pH 2–11 depending on their structure and able to perform sequential catalytic cycles without regeneration.     

Sorption of polycyclic aromatic hydrocarbons from aqueous solution by hexadecyltrimethylammonium bromide modified fibric peat

BACKGROUND: Fibric peat was modified by hexadecyltrimethylammonium bromide (HTAB) to improve its performance in sorption of polycyclic aromatic hydrocarbons (PAHs). The raw fibric peat (P‐R) and surfactant modified peat (P‐HTAB) were characterized by capillary rise test to determine the effect of HTAB on surface hydrophobicity. Effect of contact time was also investigated. Batch sorption data were fitted to the Freundlich model and pseudo‐second‐order model for isotherm and kinetics study. RESULTS: P‐HTAB had a more hydrophobic surface than P‐R. After modification, the sorption coefficients (K_OC) of naphthalene, phenanthrene and pyrene on fibric peat increased from 1590, 29661 and 204171 mL g^?1 to 2006, 52410 and 358569 mL g^?1, respectively; the sorption rate constants of naphthalene, phenanthrene and pyrene increased from 0.00057, 0.00036 and 0.00051 g µg^?1 min^?1 to 0.00062, 0.00140 and 0.00155 g µg^?1 min^?1, respectively. The sorption coefficients of PAHs were positively correlated with the octane‐water partition coefficients of PAHs. CONCLUSIONS: The hydrophobicity of fibric peat was enhanced through modification by HTAB, which resulted in the improved sorption rate and sorption capacity for PAHs. The sorption performance of P‐HTAB reveals that it is an effective biosorbent for PAHs and has potential for treatment of wastewater containing hydrophobic organic contaminants. Copyright © 2010 Society of Chemical Industry     

Three-membered benzylic thia-rings of polycyclic aromatic hydrocarbons: synthesis,molecular calculations and properties

In cancer research/organic synthesis related studies, several hitherto unknown three-membered benzylic thia-ring-containing polycyclic aromatic hydrocarbons, PAH-episulfides (PeSs) and PAH diol episulfides (DeSs), have been synthesized and their relevant chemistry explored. These compounds represent the sulfur analogs of the corresponding diol epoxide carcinogens. A highly efficient general synthetic methodology has been developed for the conversion of epoxides and, stereoselectively, diol epoxides into their corresponding episulfides using the nucleophilic sulfur transfer agent DMTF. The newly-synthesized DeSs show remarkable stability towards aqueous acid whereas both PeSs and DeSs are thermodynamically unstable (loss of sulfur)—consistent with the predictions of previously performed molecular orbital calculations. This review constitutes an account of what has been achieved in this area, focusing on aspects related to cancer research and the implications for further research.     

焦化废水中的杂环化合物及多环芳烃降解的研究进展

综述了近年来焦化废水中的杂环化合物和多环芳烃降解的研究进展,总结了物理法的降解研究,归纳了生物法的降解机理,概括了化学法的研究进展,最后指出了焦化废水降解的研究方向。     

The effects of oxygen on the yields of polycyclic aromatic hydrocarbons formed during the pyrolysis and fuel-rich oxidation of catechol

To better understand the effects of oxygen on the formation and destruction of polycyclic aromatic hydrocarbons (PAH) during the burning of complex solid fuels, we have performed pyrolysis and fuel-rich oxidation experiments in an isothermal laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in coal, wood, and biomass. The catechol pyrolysis experiments are conducted at a fixed residence time of 0.3 s, at nine temperatures spanning the range of 500-1000 °C, and under varying oxygen ratios ranging from 0 (pure pyrolysis) to 0.92 (near stoichiometric oxidation). The PAH products, ranging in size from two to nine fused aromatic rings, have been analyzed by gas chromatography with flame-ionization and mass spectrometric detection, and by high-pressure liquid chromatography with diode-array ultraviolet-visible absorbance detection. The quantified PAH products fall into six structural classes: benzenoid PAH, indene benzologues, fluoranthene benzologues, cyclopenta-fused PAH, ethynyl-substituted PAH, and methyl-substituted PAH. A comparison of product yields from pyrolysis and fuel-rich oxidation of catechol reveals that at temperatures <800 °C, where only two-ring PAH are produced in significant quantities, increases in oxygen concentration bring about increases in yields of the two-ring aromatics indene and naphthalene. At temperatures >800 °C, increases in oxygen concentration bring about dramatic decreases in the yields of all PAH products, due to oxidative destruction reactions. The smaller-ring-number PAH are produced in higher abundance under all conditions studied, and the oxygen-induced decreases in the yields of PAH are increasingly more pronounced as the PAH ring number is increased. These observations regarding PAH ring number, from the fuel-rich oxidation experiments with catechol, fully support our finding from catechol pyrolysis in the absence of oxygen: that PAH formation and growth occur by successive ring-buildup reactions involving the C₁-C₅ and single-ring aromatic products of catechol’s thermal decomposition. The yield/temperature data reported here represent one of the most extensive quantifications of the effects of oxygen on PAH produced during the pyrolysis of any fuel.     

Development of micellar solid-phase microextraction fiber based on CTAB-templated mesoporous silica electrochemically assisted self-assembled on wire: Application to chromatographic determination of polycyclic aromatic hydrocarbons

This paper describes the development of a new micellar solid-phase microextraction fiber based on cetyltrimethylammonium bromide-templated mesoporous silica electrochemically assisted self-assembled on copper wire for sensitive determination of polycyclic aromatic hydrocarbons by HPLC. After optimization of experimental parameters, non-polar analytes of PAHs were successfully determined in water samples after microextraction by CTAB/MCM-41 copper fiber as micellar organic platform. The proposed method indicated good linearity in the range 0.01–82.5 µg L^?1 and limits of detection in the range 3–46 ng L^?1. Relative standard deviations of the method were obtained in the range 3.1–8.3%.     

Platinum catalysts supported on hydrothermally stable mesoporous aluminosilicate for the catalytic oxidation of polycyclic aromatic hydrocarbons (PAHs)

Catalytic oxidation of polycyclic aromatic hydrocarbons (PAHs) was studied over platinum catalysts supported on the hydrothermally stable mesoporous aluminosilicate (SM-41). Naphthalene was chosen as a model reactant of PAHs, due to the simplest and the least toxic PAHs. Zeolite seeds crystallization method was used for synthesis of SM-41. Pt/SM-41 catalyst showed higher activity than Pt/MCM-41 for catalytic oxidation of naphthalene in the presence of 10 vol.% water vapor. Hydrothermal stability and hydrophobicity of Pt/SM-41 must be beneficial for the catalytic oxidation of naphthalene in the presence of water vapor.     

污泥热解过程中多环芳烃排放规律

研究了不同温度（350~1050℃）下污泥热解过程液、气、固三相产物中16种多环芳烃（PAHs）排放规律。结果表明,PAHs趋向富集于液相产物中,其次为气相产物,在液相产物中检测到所有16种PAHs,650℃液相产物中16种PAHs（∑₁₆PAHs）总质量比最高,为96%;750℃气相产物中∑₁₆PAHs质量比最高,为21.3%以上;固相产物中PAHs含量极少,仅在650℃时达1%。所有温度下液相产物中2、3和4环PAHs均占据主导地位,∑_2,3,4环PAHs质量比达95%以上,850℃时液相产物中∑EPA-PAHs含量最高,达15.25 mg·kg^-1。气相产物主要以萘（NaP）、苊烯（Acp）、芴（Flu）和蒽（Ant）PAHs为主,未检测到高环PAHs。在高温热解阶段,污泥大分子结构裂解到达高峰,伴随产物的二次断裂、合成、环化等反应,气相产物中∑_低PAHs生成含量达到最高7.248 mg·kg^-1。不同温度下污泥热解产物中PAHs的毒性当量（TEQ）变化规律与其生成量变化基本一致,在850℃时液相产物中PAHs的TEQ最高达1.129。     

煤转化过程中多环芳烃排放的研究现状

发展煤洁净转化技术,减少污染物的排放是煤化工发展方向.目前国内外对减少煤加工过程的CO_2、NO_x、SO_x等污染物的排放研究较多,但对煤加工过程有机污染物多环芳烃(PAHs)的研究还相对不足.本文就多环芳烃的理化性质、起源及其取样和分析方法以及煤加工利用过程中多环芳烃生成与释放的影响因素等有关问题进行了综述和分析,并在此基础上提出进行煤转化过程中多环芳烃的生成与控制研究的思路.     

Bioremediation of polycyclic aromatic hydrocarbons: current knowledge and future directions

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decades due to their potentially harmful effects to human health. This concern has prompted researchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available. Copyright © 2005 Society of Chemical Industry     

Photooxidation reactions of polycyclic aromatic hydrocarbons over pure and Ag-loaded BiVO4 photocatalysts

Photooxidative degradations of nine polycyclic aromatic hydrocarbons (PAHs) using pure and Ag-loaded BiVO₄ photocatalysts have been examined in acetonitrile under visible light irradiation. Photoproducts have been identified by means of gas chromatography–mass spectrometry (GC–MS). Silver fine particles loaded on BiVO₄ surface improved the reaction rates of all PAHs degradations. In particular, anthracene and benz[a]anthracene (Bz[a]A) are efficiently oxidized to anthraquinone and benz[a]anthracene-7,12-dione, respectively. Photooxidation mechanism of anthracene and Bz[a]A has been clarified by the GC–MS analyses by the use of H₂¹⁸O as a reactant. It has been proved that OH radicals are generated through the oxidation of water by valence band holes on the Ag-BiVO₄ surface in acetonitrile, and greatly contribute to the degradations of these PAHs. The OH radical attack to PAHs probably determines the overall rates of oxidation of PAHs on Ag-BiVO₄ photocatalyst.     

多环芳烃的加氢裂化

本文综述了近年来多环芳烃加氢裂化反应催化剂、反应网络及反应机理等方面的研究进展。     

劣质催化柴油中多环芳烃选择加氢工艺评价

选取商品柴油加氢精制催化剂和催化柴油选择加氢裂化催化剂,采用N_2吸附-脱附、XRD、TPD、Py-IR等对催化剂进行表征,结果表明,选择加氢裂化催化剂较加氢精制催化剂具有更大的比表面积和孔容,具有更多的中强酸量和较少的弱酸量,并具有更多的B酸中心。以中石化青岛炼化公司生产的高密度、低十六烷值的FCC柴油为原料,对商品加氢精制催化剂和加氢精制/选择加氢裂化组合催化剂进行FCC柴油中多环芳烃选择加氢工艺条件的考察,结果表明,加氢精制催化剂适宜的反应条件为370℃、1.25 h~(-1)、8.0 Mpa,加氢精制/选择加氢裂化催化剂适宜的反应条件为350℃、1.25 h~(-1)、8.0 MPa,组合催化剂的多环芳烃选择加氢效果较好。