Catalytic ammonia decomposition over industrial-waste-supported Ru catalysts

Industrial solid wastes (fly ash and red mud) have been employed as supports for preparation of Ru-based catalysts. Physical and chemical treatments on red mud were conducted and these modified supports were also used for preparation of Ru-based catalysts. Those Ru catalysts were characterized by various techniques such as N2 adsorption, H2 adsorption, XRD, XPS, and temperature-programmed reduction (TPR), and were then tested for catalytic ammonia decomposition to hydrogen. It was found that red-mud-supported Ru catalyst exhibits higher ammonia conversion and hydrogen production than fly-ash-supported catalyst. Heat and chemical treatments of the red mud greatly improve the catalytic activity. Moreover, a combination of acid and heat treatments produces the highest catalytic conversion of ammonia.     

Adsorption of polar and nonpolar organic chemicals to carbon nanotubes

Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical-chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitrofunctional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the pi-pi electron-donor-acceptor (EDA) interaction between nitroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of carbon nanotubes. Additionally, we attribute the stronger adsorption of nonpolar aromatics compared to that of nonpolar aliphatics to the pi-electron coupling between the flat surfaces of both aromatic molecules and carbon nanotubes. For tetrachlorobenzene, the bulkiest adsorbate, adsorption affinity (on a unit surface area basis) to the SWNT was much stronger than to the two MWNTs, indicating a probable molecular sieving effect.     

模拟太阳光下金属酞菁/多壁碳纳米管催化降解染料

为拓宽芬顿体系pH值的使用范围以高效降解水体中的染料,采用回流法制备多壁碳纳米管负载的十六氯铁酞菁 (FePcCl₁₆/MWCNTs)催化剂,以双氧水(H₂O₂)为氧化剂,在模拟太阳光照的作用下催化降解酸性橙7(AO7) 染料。借助扫描电子显微镜、透射电子显微镜、红外光谱仪、热重分析仪和X射线衍射仪等对催化体系的催化性能、影响因素和催化机制进行研究。结果表明:催化体系在酸性、无机盐及尿素环境中,对AO7的降解率均为100%,在中性环境中为97%,在碱性条件下为75%;该催化体系经5次循环使用后,对AO7的降解率仍在95%以上;催化体系中降解AO7的主要活性种为羟基自由基和超氧自由基,光照可促进活性种的产生而提高体系的催化性能。     

天然乳胶产品的鉴定以及风险监控

随着乳胶产品的广泛应用,如何鉴定乳胶中的天然成分以及对毒害化学物质的风险监控成为关注的焦点.采用红外光谱法和水提蛋白质法,利用天然乳胶中所含蛋白质的特征,可准确、快速地鉴定天然乳胶与合成聚异戊二烯乳胶.同时分析了乳胶生产过程中存在的危害化学物质风险及检测限量.     

Peer reviewed: massachusetts tries to cut toxic chemicals use

An evaluation of statewide effort reveals toxic chemical use and waste generation have declined.     

Fate of chemical warfare agents and toxic industrial chemicals in landfills

One component of preparedness for a chemical attack is planning for the disposal of contaminated debris. To assess the feasibility of contaminated debris disposal in municipal solid waste (MSW) landfills, the fate of selected chemical warfare agents (CWAs) and toxic industrial chemicals (TICs) in MSW landfills was predicted with a mathematical model. Five blister agents [sulfur mustard (HD), nitrogen mustard (HN-2), lewisite (L), ethyldichloroarsine (ED), and phosgene oxime (CX)], eight nerve agents [tabun (GA), sarin (GB), soman (GD), GE, GF, VX, VG, and VM], one riot-control agent [CS], and two TICs [furan and carbon disulfide] were studied. The effects of both infiltration (climate) and contaminant biodegradability on fate predictions were assessed. Model results showed that hydrolysis and gas-phase advection were the principal fate pathways for CWAs and TICs, respectively. Apart from CX and the TICs, none of the investigated compounds was predicted to persist in a landfill for more than 5 years. Climate had little impact on CWA/TIC fate, and biodegradability was only important for compounds with long hydrolysis half-lives. Monte Carlo simulations were performed to assess the influence of uncertainty in model input parameters on CWA/TIC fate predictions. Correlation analyses showed that uncertainty in hydrolysis rate constants was the primary contributor to variance of CWA fate predictions, while uncertainty in the Henry's Law constant and landfill gas-production rate accounted for most of the variance of TIC fate predictions. CWA hydrolysates were more persistent than the parent CWAs, but limited information is available on abiotic or biotic transformation rates for these chemicals.     

聚酯功能化碳纳米管的非等温结晶动力学

以己二酸,1,3-丙二醇和羟基碳纳米管为原料,钛酸丁酯为催化剂,采用原位聚合法制备了聚己二酸-1,3-丙二醇酯功能化羟基碳纳米管(PHHCNTs)。经热重分析(TG)结果计算发现,接枝到羟基碳纳米管表面上的聚酯链的链长随催化剂质量分数的增加而减小。利用差热扫描量热仪(DSC)研究了催化剂对PHHCNTs熔融和非等温结晶行为的影响,结晶温度随催化剂质量分数的增加而升高,随降温速率增加而降低;并且催化剂质量分数越高,PHHCNTs的过冷度越低。Jeziorny法可以很准确地描述PHHCNTs的非等温结晶过程。     

Measuring and modeling adsorption of PAHs to carbon nanotubes over a six order of magnitude wide concentration range

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.     

Estimating the impact of high-production-volume chemicals on remote ecosystems by toxic pressure calculation

Although many chemicals are in use, the environmental impacts of only a few have been established, usually on per-chemical basis. Uncertainty remains about the overall impact of chemicals. This paper estimates combined toxic pressure on coastal North Sea ecosystems from 343 high-production-volume chemicals used within the catchment of rivers Rhine, Meuse, and Scheldt. Multimedia fate modeling and species sensitivity distribution-based effects estimation are applied. Calculations start from production volumes and emission rates and use physicochemical substance properties and aquatic ecotoxicity data. Parameter uncertainty is addressed by Monte Carlo simulations. Results suggest that the procedure is technically feasible. Combined toxic pressure of all 343 chemicals in coastal North Seawater is 0.025 (2.5% of the species are exposed to concentration levels above EC50 values), with a wide confidence interval of nearly 0-1. This uncertainty appears to be largely due to uncertainties in interspecies variances of aquatic toxicities and, to a lesser extent, to uncertainties in emissions and degradation rates. Due to these uncertainties, the results support gross ranking of chemicals in categories: negligible and possibly relevant contributions only. With 95% confidence, 283 of the 343 chemicals (83%) contribute negligibly (less than 0.1%) to overall toxic pressure, and only 60 (17%) need further consideration.     

Neurite outgrowths of neurons with neurotrophin-coated carbon nanotubes

Multiwalled carbon nanotubes (CNTs) coated with neurotrophin were used to regulate the differentiation and survival of neurons. Neurotrophin (nerve growth factor [NGF] or brain-derived neurotrophic factor [BDNF]) was covalently bound to CNTs modified by amino groups using a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) reagent. The CNTs coated with NGF or BDNF promoted the neurite outgrowths of neurons in the same manner as soluble NGF and soluble BDNF. By enzyme-linked immunosorbent assay (ELISA), we demonstrated that neurotrophin-coated CNTs carry neurotrophin. These results suggest that neurotrophin-coated CNTs have biological activity and stimulate the neurite outgrowths of neurons.     

Bioaccumulation of radio-labeled carbon nanotubes by Eisenia foetida

Carbon nanotubes comprise a class of nanomaterials having demonstrated promise for broad ranges of potential applications. Because of difficulties associated with quantifying these materials in environmental media, however, their behaviors therein and associated potential risks are yet largely unknown. To address this problem, a modified chemical vapor deposition process employing carbon-14 labeled methane was used to synthesize single- and multi-walled carbon nanotubes. The labeled nanotubes and a representative polynuclear hydrocarbon, pyrene, were then individually spiked to identical soil samples. The uptake and depuration behaviors of the spiked materials by the earthworm Eisenia foetida, a potential entry point to terrestrial food chains, were then assessed. Bioaccumulation factors determined for the nanotubes were almost 2 orders of magnitude smaller than those measured for pyrene, indicating that purified carbon nanotubes, unlike pyrene, are neither readily absorbed into organism tissues nor manifest equilibrium partitioning thereto.     

碳纳米管及其复合材料的制备与性能研究进展

介绍了碳纳米管的制备、纯化和功能化修饰方法,碳纳米管/聚合物复合材料的制备主要有溶液共混法、固相加热共融法和原位聚合法,以及复合材料的力学性能、导电性能和光电性能,指出碳纳米管与聚合物的详细复合机理尚待重点研究.     

碳纳米管对棉织物的表面改性

棉纤维是纺织行业中最重要的原材料之一.与合成纤维相比,棉纤维的主要缺点是力学性能相对较差、易燃、紫外线防护性能较差.研究了碳纳米管(CNT)对普通棉纤维的功能化改性.采用浸轧法在棉纤维表面涂覆致密的碳纳米管涂层,并对织物的机械强度、阻燃性能和防紫外线性能进行了测试.由于碳纳米管的包覆和保护作用,改性棉织物表现出优异的机...     

Plastic resin pellets as a transport medium for toxic chemicals in the marine environment

Plastic resin pellets (small granules 0.1-0.5 centimeters in diameter) are widely distributed in the ocean all over the world. They are an industrial raw material for the plastic industry and are unintentionally released to the environment both during manufacturing and transport. They are sometimes ingested by seabirds and other marine organisms, and their adverse effects on organisms are a concern. In the present study, PCBs, DDE, and nonylphenols (NP) were detected in polypropylene (PP) resin pellets collected from four Japanese coasts. Concentrations of PCBs (4-117 ng/g), DDE (0.16-3.1 ng/g), and NP (0.13-16 microg/g) varied among the sampling sites. These concentrations were comparable to those for suspended particles and bottom sediments collected from the same area as the pellets. Field adsorption experiments using PP virgin pellets demonstrated significant and steady increase in PCBs and DDE concentrations throughout the six-day experiment, indicating that the source of PCBs and DDE is ambient seawater and that adsorption to pellet surfaces is the mechanism of enrichment. The major source of NP in the marine PP resin pellets was thought to be plastic additives and/or their degradation products. Comparison of PCBs and DDE concentrations in mari     

Photocatalytic oxidation of aqueous ammonia over microwave-induced titanate nanotubes

Characterizations of microwave-induced titanate nanotubes (NaxH(2-x)Ti3O7, TNTs) were conducted by the determinations of specific surface area (S(BET)), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), ionic coupled plasma-atomic emission spectrometry(ICP-AES), scanning electron microscopy/ energy dispersive X-ray (SEM/EDX), and high-resolution transmission electron microscopy (HR-TEM). The applied level of microwave irradiation during the fabrication process is responsible for both the intercalation intensity of Na atoms into TNTs and the type of crystallization phase within TNTs, which dominate the efficiency of photocatalytic NH3/NH4+. A pure TNT phase presents no powerful ability toward photocatalytic NH3/ NH4+, while the photocatalytic efficiency can be enhanced with the presence of a rutile phase within TNTs. In addition, the mixture of anatase and rutile phase within P25 TiO2 prefers forming NO3-, whereas TNTs yield higher NO2- amount Regarding the effect of acid-washing treatment on TNTs, the acid-treated TNTs with enhanced ion exchangeability considerably improve the NH3/NH4+ degradation and NO2-/NO3- yields. This result is likely ascribed to the easy intercalation of NH3/ NH4+ into the structure of acid-washing TNTs so that the photocatalytic oxidation of intercalated NH3/NH4+ is not limited to the shielding effect resulting from the overload of TNTs.     

改性蒙脱土催化油酸甲酯化的研究

采用浸渍法制备了改性对甲苯磺酸-蒙脱土固体酸催化剂,并将其应用于油酸与甲醇酯化制备油酸甲酯的反应体系中。通过对改性固体酸催化剂进行粉末衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)等表征技术发现,制备得到的改性固体酸为分散的小块片状结构,比表面积得到增加。此外,考察了催化剂用量、油酸与甲醇物质的量之比、反应温度及时间等因素对油酸转化率的影响。数据显示:在催化剂用量0.25 g、油酸与甲醇物质的量之比1∶10、反应温度70℃、反应时间3 h的条件下,油酸转化率为65.6%,且该催化剂适用于其它一些游离脂肪酸酯化及非粮油料预酯化反应。     

Adsorption of hydroxyl- and amino-substituted aromatics to carbon nanotubes

The combined effects of hydroxyl/amino functional groups of aromatics and surface O-containing groups of carbon nanotubes on adsorption were evaluated. When normalized for hydrophobicity, 2,4-dichlorophenol and 2-naphthol exhibited a greater adsorptive affinity to carbon nanotubes and graphite (a model adsorbent without the surface O functionality) than structurally similar 1,3-dichlorobenzene and naphthalene, respectively, and 1-naphthylamine exhibited a much greater adsorptive affinity than all other compounds. Results of the pH-dependency experiments further indicated that the hydroxy/amino functional groups of the adsorbates and the surface properties of the adsorbents played a combinational role in determining the significance of the nonhydrophobic adsorptive interactions. We propose that the strong adsorptive interaction between hydroxyl-substituted aromatics and carbon nanotubes/graphite was mainly due to the electron-donating effect of the hydroxyl group, which caused a strong electron-donor-acceptor (EDA) interaction between the adsorbates and the pi-electron-depleted regions on the graphene surfaces of carbon nanotubes or graphite. In addition to the EDA interaction, Lewis acid-base interaction was likely an extra important mechanism contributing to the strong adsorption of 1-naphthylamine, especially on the O-functionality-abundant carbon nanotubes. The findings of the present study might have significant implications for selective removal of environmental contaminants with carbon nanotubes.