Designing Pd-on-Au bimetallic nanoparticle catalysts for trichloroethene hydrodechlorination

Alumina-supported palladium (Pd) catalysts have previously been shown to hydrodechlorinate trichloroethene (TCE) and other chlorinated compounds in water, at room temperature, and in the presence of hydrogen. The feasibility of this catalytic technology to remediate groundwater of halogenated compounds can be improved by re-designing the Pd material in order to increase catalytic activity. We synthesized and characterized Pd supported on gold nanoparticles (Au NPs) of different Pd loadings. In all cases, we found that these catalysts were considerably more active than Pd NPs, alumina-supported Pd, ard Pd-black (62.0, 12.2, and 0.42 L x g(Pd)(-1) x min(-1), respectively). There is a synergistic effect of the Pd-on-Au bimetallic structure, with the material with the highest TCE hydrodechlorination activity (943 L x g(Pd)(-1) x min(-1)) comprised of Au NPs partially covered by Pd metal. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. The resulting nanoparticle-based materials should be highly suitable as hydrodehalogenation and reduction catalysts for the remediation of various organic and inorganic groundwater contaminants.     

Pd/C催化剂的制备、表征及活性研究

以活性炭为载体负载贵金属钯制备Pd/C催化剂.先将氯化钯吸附在活性炭上，再通过氢氧化钠溶液使其以氧化钯或氢氧化钯的形式吸附在活性炭上，干燥还原后作为硬脂腈加氢制备长链烷基二甲基叔胺的催化剂，研究炭钯催化剂对长链烷基二甲基叔胺的活性.通过N2-吸附测试了活性炭的比表面、孔径分布和孔型结构以及在负载活性组分钯后的活性炭表面状况，透射电子显微镜表征了钯在载体活性炭上的分散状况，X-射线衍射分析了活性炭上负载新鲜钯的晶体结构，并用气相色谱对产品进行了定性定量分析，最后以电位滴定测定催化反应时二甲基叔胺得率对其进行活性评价.应用研究表明，活性炭作为载体负载贵金属钯，作为硬脂腈催化加氢制备长链烷基二甲基叔胺的催化剂，其结果较好.     

Influences of amphiphiles on dechlorination of a trichlorobenzene by nanoscale Pd/Fe: adsorption, reaction kinetics, and interfacial Interactions

The influences of amphiphiles on the catalytic dechlorination of 1,2,4-trichlorobenzene (124TCB) bythe nanoscale Pd/Fe particles were comprehensively examined. The fresh and reacted Pd/ Fe particles were characterized with XRD, TEM, SEM, FTIR spectrometry, and goniometry. Adsorption of amphiphiles on the Pd/Fe particles, iron dissolution, and H2 evolution in the Pd/Fe-water system were quantified to expound the influences of the various amphiphiles on the dechlorination process. The Langmuir-Hinshelwood model is used to elucidate the dechlorination kinetics, and it provides insight into the influence of amphiphiles on 124TCB partitioning to the interfacial layer and the resulting dechlorination rates. The rate constants increased by a factor of 1.5--2.5 with the presence of cationic cetyltrimethylammonium bromide (CTAB). In the anionic sodium deodecyl sulfate(SDS) or nonionic nonylphenol ethoxylate (NPE) and octylphenolpoly (ethylene glycol ether)x (TX-100) surfactant solutions, the 124TCB dechlorination rates were slightly increased over those observed in ultrapure water. However, when concentrations of the surfactants were above their CMCs, the dechlorination rates decreased. The findings also showed that DPC (dodecylpyridinium chloride) and NOM (natural organic matter) might be the competitive H2 acceptors to 124TCB, and they significantly retarded its catalytic dechlorination by the Pd/Fe particles. CTAB at a concentration below the CMC appeared to be the most benign to the 124TCB dechlorination.     

Mobilization, adsorption, and bioavailability of Pt and Pd in coastal sediments: the role of the polychaete, Arenicola marina

The biogeochemical behavior of Pt and Pd in coastal sediments has been examined in a series of microcosms, both in the presence and absence of the deposit-feeding invertebrate, Arenicola marina. When metals were introduced to the overlying water column as solutes from acidified standards, A. marina dramatically enhanced their sorption to sediment throughout the core depth (14 cm) compared with an unfaunated control by exposing a greater surface area of particles to more rapidly ventilating contaminated water. After a 10 day incubation period, the assimilation efficiency (AE) by A. marina was about 10% for Pt and 1% for Pd. Calculations based on either partition constants or operational measures of metal bioaccessibility in sediment (using the protein, BSA) suggested that both aqueous and dietary sources of metal were important When Pt and Pd were introduced to the sediment-water interface as components of ground catalytic converter particles, significant subduction was effected by A. marina, and metals were solubilized to a greater extent than in an unfaunated control. AE in these experiments was < 0.1% for Pt and about 1% for Pd, and the most important vector for assimilation appeared to be from the aqueous phase via partial solubilization of metal from catalytic material. The findings of this study improve our understanding of the availability, cycling, and fate of Pt and Pd in contaminated estuaries and coastal waters.     

Efficient catalytic decomposition of CO2 to CO and O2 over Pd/ mixed-conducting oxide catalyst in an oxygen-permeable membrane reactor

The thermal decomposition of CO2 to CO and O2 is a potential route for the consumption and utilization of CO2. However, this reaction is limited by both the thermodynamic equilibrium and the kinetic barrier. In this study, we reported an innovative catalytic process to decompose CO2 in an oxygen-permeation membrane reactor packed with a mixed-conducting oxide supported noble metal catalyst, or Pd/SrCo0.4Fe0.5Zr0.1O3-delta (Pd/ SCFZ), which is of high activity in the decomposition of CO2 into CO and O2. Pd/SCFZ catalyst was prepared by incipient wetness impregnation of the SCFZ powders with an aqueous solution of PdCl2, and the CO2 sorption/desorption property was examined by in situ Fourier transform infrared spectroscopy and temperature-programmed desorption-mass spectrometry technologies. It was shown that there appeared a typical of bridged carbonyls (Pd-CO) on the surface of the Pd/SCFZ catalyst formed after CO2 decomposition. Both CO2 and CO could be detected in the species desorbed from Pd/SCFZ catalyst, which implied that the Pd/SCFZ catalyst could effectively activate the CO2 molecule. During the catalytic process, furthermore, the activity of the Pd/SCFZ catalyst can self-regenerate by removing the produced lattice oxygen through the dense oxygen-permeable ceramic membrane. At 900 degrees C, this catalytic process attains 100% of CO formation selectivity at 15.8% of CO2 conversions.     

Potential mobilization of platinum-group elements by siderophores in surface environments

The emission of platinum-group elements (PGEs) from catalytic converters has led to increased environmental abundances of Pt, Pd, and Rh; however, little is known about the environmental effects and fate of these metals. Organic ligands found in soils have the potential to increase the mobility of PGEs and potentially increase the bioavailability of the metals. Here, we assessed the abilities of microbially produced iron-chelating ligands (siderophores) to complex with the PGEs. Batch experiments using the synthetic siderophore desferrioxamine-B (DFO-B) and powdered metal or oxide forms of Pt, Pd, or Rh showed that DFO-B enhances the solubility of Pt and Pd due to the formation of Pt- and Pd-DFO-B aqueous complexes, with estimated minimum stability constants on the order of 10(17-18) and 10(20-24), respectively. Dissolution rates for Pd are comparable to other mineral dissolution rates with DFO-B. DFO-B had little to no effect on the dissolution of Rh metal or Rh2O3. Our results indicate that siderophores have the potential to increase the mobility of Pt and Pd in environments with limited activities of free trivalent cations. These results have implications for the fate of catalytic converter-emitted Pt and Pd, and support the need for further Pt and Pd toxicity and bioaccumulation studies.     

LaFeO_3系钙钛复合氧化物降低卷烟烟气中的NO_x

为降低卷烟烟气中的氮氧化物(NOx),采用TG、XRD、氮吸附和TEM等方法测定了LaFeO3钙钛矿型复合金属氧化物——LaFe0.85Pd0.05Cu0.1O3的热稳定性、比表面积、粒子的形状与大小,以及对NO的分解催化活性,并以添加于造纸法再造烟叶中的形式,考察了该氧化物对卷烟烟气中NOx等有害成分的影响。结果表明:于700℃下焙烧2h,该氧化物的比表面积为17.24m2/g,平均粒径50nm,具有较高的NO分解催化活性;与对照相比,含1.5%该复合金属氧化物的卷烟烟气中NOx含量降低13.0%,比焦油多降低约9百分点。     

Pd修饰TiO2光催化材料在棉织物中的应用

为提高棉织物表面TiO2的光催化效果,以棉针织物为载体,纳米羟基磷灰石（HAP）为保护剂,纳米TiO2为光催化剂,实践Pd对光催化剂的表面改性,制备具有光催化功能的纺织装饰材料。并采用扫描电镜、气相色谱等测试手段,对整理剂在织物表面的沉积状况、织物对甲醛的催化降解效率等进行测试和分析。结果表明：经过Pd表面改性后,织物表面TiO2的光催化效果得到明显的改善,较改性前提高了49%,并具有很好的紫外防护效果;纳米HAP整理对织物表面光催化剂具有一定的吸附效果。     

Highly selective PdCu/amorphous silica-alumina (ASA) catalysts for groundwater denitration

Catalytic nitrate reduction is a promising technology in groundwater purification. In this study, PdCu bimetallic catalysts supported on an industrial amorphous silica-alumina (ASA) were synthesized and used to simulate catalytic removal of nitrate in groundwater. The catalysts exhibited very high activity and the highest catalytic selectivity toward N?O and N? was 90.2%. The optimal Pd/Cu weight ratio was four. Relatively low reduction temperature was found benefit the catalytic stability and 300 °C was the appropriate reduction temperature during catalyst preparation. With an average particle size 5.4 nm, the metal particles were very uniformly distributed on the catalyst surface prepared with the codeposition method. This kept the catalyst more stable than the PdCu/Al?O? catalyst with larger metal particles. According to XRD, TEM, and XPS results, the metals maintained zero-valence but aggregated by about 2 nm during the denitration reaction, which caused gradual deactivation of the catalysts. Little leaching of Cu and Pd from the catalyst might also have a slightly negative impact to the stability of the catalysts. A simple treatment was found to redistribute the particles on the deactivated catalysts, and high catalytic activity was recovered after this process.     

表面增强拉曼光谱法快速测定保健酒中西地那非

目的 建立金核银壳结构纳米颗粒(Au@Ag NPs)的表面增强拉曼光谱法(surface-enhanced Raman scattering, SERS)快速检测保健酒中非法添加物西地那非的分析方法。方法 制备3种纳米粒子Ag、Au、Au@Ag NPs为SERS基底, 比较3种基底的增强效果。样品前处理基于溶剂萃取法, 利用二氯甲烷对保健酒中的西地那非进行简单提取, 通过调节体系pH值, 得到最佳提取率和SERS增强效果。结果 Au@Ag NPs的SERS增强效应优于Au NPs和Ag NPs; 用0.1 mol/L氢氧化钾调节溶液pH值可有效提高二氯甲烷的提取效果, 再用0.1 mol/L稀盐酸溶解挥发后残留物, 使得西地那非在pH调节后更有利于吸附在Au@Ag NPs表面, 获得更强的SERS信号。西地那非的检出限为0.5 mg/L, 在0.5~10 mg/L浓度范围内线性关系较好, 相关系数(r2)为0.9472, 回收率为86.0%~95.8%之间, 相对标准偏差(relative standard deviation, RSD)为3.6%~5.9%。 结论 SERS技术灵敏度高、特异性强, 可用于快速检测保健酒中的西地那非, 为快速筛查大量样品提供新方法。     

Changes in palladium, platinum, and rhodium concentrations, and their spatial distribution in soils along a major highway in Germany from 1994 to 2004

Soil samples were collected along the highway A5 from the major junctions Frankfurter Kreuz to Darmst?der Kreuz from July to September, 2004 and analyzed for palladium (Pd), platinum (Pt), and rhodium (Rh). The results were compared to analyses of platinum group elements (PGE) in soils collected along this same stretch of highway in 1994. The goal of this study is to detect any changes that may have occurred in the concentration and environmental distribution patterns of these metals over this 10 year period. The concentrations of Pd in soils along the highway were found to be about 15 times higher on average than those measured in 1994. Pt and Rh concentrations increased 2 and 1.6 times, respectively, during this time period. The significant rise in Pd concentrations in soils observed for the time period of analysis is likely due to its use in automobile catalytic converters in Germany since 1993. The results also show a strong positive relationship between PGE emissions and traffic density and speed. The results indicate that increases in the concentrations of Pd, Pt, and Rh in soils along the highway are not limited to the soil surface. Pt was measured as deep as 12 cm. Pd was determined at even greater depths of 12-16 cm. The presence of Pd at lower depths compared to Pt suggests that this element has a higher solubility. Pd, Pt, and Rh concentrations display a strong inverse relationship with distance from the road, with decreasing levels with increasing distance from the highway. Nonetheless, Pd and Pt were detected in a meadow as far as 50 m from the highway, a much greater distance compared to that measured for these metals in 1994. Pt concentrations were also found to significantly correlate with levels of Rh and Pd. The ratios between the PGE analyzed (Pt/Rh and Pd/Rh) display a shift toward Pt and Pd. The results clearly show that PGE concentrations have increased over time. Observed increases in Pd concentrations are particularly a cause of concern.     

Enhanced activity and selectivity of carbon nanofiber supported Pd catalysts for nitrite reduction

Pd-based catalyst treatment represents an emerging technology that shows promise to remove nitrate and nitrite from drinking water. In this work we use vapor-grown carbon nanofiber (CNF) supports in order to explore the effects of Pd nanoparticle size and interior versus exterior loading on nitrite reduction activity and selectivity (i.e., dinitrogen over ammonia production). Results show that nitrite reduction activity increases by 3.1-fold and selectivity decreases by 8.0-fold, with decreasing Pd nanoparticle size from 1.4 to 9.6 nm. Both activity and selectivity are not significantly influenced by Pd interior versus exterior CNF loading. Consequently, turnover frequencies (TOFs) among all CNF catalysts are similar, suggesting nitrite reduction is not sensitive to Pd location on CNFs nor Pd structure. CNF-based catalysts compare favorably to conventional Pd catalysts (i.e., Pd on activated carbon or alumina) with respect to nitrite reduction activity and selectivity, and they maintain activity over multiple reduction cycles. Hence, our results suggest new insights that an optimum Pd nanoparticle size on CNFs balances faster kinetics with lower ammonia production, that catalysts can be tailored at the nanoscale to improve catalytic performance for nitrite, and that CNFs hold promise as highly effective catalyst supports in drinking water treatment.     

Biosupported bimetallic Pd-Au nanocatalysts for dechlorination of environmental contaminants

Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichlorethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L(-1) and reduced simultaneously by Shewanella oneidensis in the presence of H(2), the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.     

SERS Detection of Insecticide Amitraz Residue in Milk Based on Au@Ag Core-Shell Nanoparticles

A simple, rapid, and environmentally friendly surface-enhanced Raman scattering (SERS) method was developed for the determination of trace amitraz in milk with the use of silver-coated gold nanoparticles (Au@Ag NPs) as enhancing reagent. The normal Raman and SERS spectra of amitraz were analyzed, and the peaks were assigned by density functional theory. The morphology of Au@Ag NPs was characterized and confirmed by transmission electron microscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The SERS effects of Au@Ag NPs were investigated, including the types of solvents for dissolving amitraz, the volume ratio of the Au@Ag NPs and amitraz, and the concentration of aggregating agent (NaCl) for aggregate Au@Ag NPs. Results show that ethanol exerts the least interference on the SERS spectrum of amitraz and is more environmentally sound than methanol. The strongest SERS signal appeared when the volume ratio of Au@Ag NPs and amitraz was 2:1. Moreover, the strongest SERS signals appeared when the concentration of NaCl was 0.025 mol L^?1 because of appropriate aggregation. Under the optimum conditions, the concentration of amitraz presents a good linear relationship with Raman intensity (723 cm^?1) with a linear range of 9.77 × 10^?4~2.93 × 10^?2 g L^?1. The detected recoveries of amitraz in milk were between 81.7 and 100.5% with a relative standard deviation (RSD) of 2.61~5.51%.     

基于柠檬酸-铕纳米配位聚合物构建荧光探针快速检测汤煲中5’-肌苷酸含量

基于柠檬酸-铕金属有机纳米配体聚合物（citrate/europium lanthanide coordination polymer nanoparticles,Cit/Eu LCP NPs）构建快速检测肉品汤煲中5’-肌苷酸（inosine-5’-monophosphate,5’-IMP）的荧光探针。研究结果表明,5’-IMP对Cit/Eu?LCP?NPs有良好的荧光猝灭作用。在最佳条件下,该荧光探针在5’-IMP?2.5～200?μg/mL的质量浓度范围内呈现出良好的线性关系,检出限为0.17?μg/mL,且具备良好的抗干扰、稳定性和重复性。为了验证方法可行性,将该方法应用于实际鸡汤样品中的5’-IMP检测,测得加标回收率为97.85%～103.95%,可为快速检测肉品汤煲中5’-IMP提供新的思路和方法。     

Attachment efficiency of nanoparticle aggregation in aqueous dispersions: modeling and experimental validation

To describe the aggregation kinetics of nanoparticles (NPs) in aqueous dispersions, a new equation for predicting the attachment efficiency is presented. The rationale is that at nanoscale, random kinetic motion may supersede the role of interaction energy in governing the aggregation kinetics of NPs, and aggregation could occur exclusively among the fraction of NPs with the minimum kinetic energy that exceeds the interaction energy barrier (E(b)). To justify this rationale, we examined the evolution of particle size distribution (PSD) and frequency distribution during aggregation, and further derived the new equation of attachment efficiency on the basis of the Maxwell-Boltzmann distribution and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The new equation was evaluated through aggregation experiments with CeO(2) NPs using time-resolved-dynamic light scattering (TR-DLS). Our results show that the prediction of the attachment efficiencies agreed remarkably well with experimental data and also correctly described the effects of ionic strength, natural organic matter (NOM), and temperature on attachment efficiency. Furthermore, the new equation was used to describe the attachment efficiencies of different types of engineered NPs selected from the literature and most of the fits showed good agreement with the inverse stability ratios (1/W) and experimentally derived results, although some minor discrepancies were present. Overall, the new equation provides an alternative theoretical approach in addition to 1/W for predicting attachment efficiency.     

Impact of whey protein isolates and concentrates on the formation of protein nanoparticles‐stabilised Pickering emulsions

Whey protein nanoparticles (NPs) were prepared by heat‐induced method. The influences of whey protein isolates (WPIs) and concentrates (WPCs) on the formation of NPs were first investigated. Then Pickering emulsions were produced by protein NPs and their properties were evaluated. After heat treatment, WPC NPs showed larger particle size, higher stability against NaCl, lower negative charge and contact angle between air and water. Dispersions of WPC NPs appeared as higher turbidity and viscosity than those of WPI NPs. The interfacial tension of WPC NPs (~7.9 mN/m at 3 wt% NPs) was greatly lower than that of WPI NPs (~12.1 mN/m at 3 wt% NPs). WPC NPs‐stabilised emulsions had smaller particle size and were more homogeneous than WPI NPs‐stabilised emulsions. WPC NPs‐stabilised emulsions had higher stability against NaCl, pH and coalescence during storage.     

Investigation of palladium and platinum levels in food by sector field inductively coupled plasma mass spectrometry.

Over the last two decades, there has been increased concern regarding the impact of some noble metals, such as Pd and Pt, on human health. These elements pollute the environment due to their widespread use as catalytic converters and in medical applications. The risk they pose to human health and the environment is still controversial; however, literature data point to diet as an important source of uptake by the human body. Within this context, the total Pd and Pt content of several Italian food commodities has been investigated. A total of 90 samples, including flour products, vegetables and foodstuffs of animal origin (meat, milk and eggs), were collected and freeze-dried. Samples were analyzed by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) after chopping or crushing followed by freeze-drying and microwave (MW)-assisted acid digestion in a Class-100 clean-room. A mathematical approach was adopted to correct the mass signals for still unresolved interference (mDeltam = 300, 10 000). The lowest and highest concentrations of Pt, i.e. 17 and 93 ng kg(-1) (dry weight, dw), were found in vegetables and flour products, respectively. The lowest Pd level (2830 ng kg(-1) dw) was found in eggs and the highest (47 800 ng kg(-1) dw) in vegetables.     

Characterization and Quantification of Zinc Oxide and Titanium Dioxide Nanoparticles in Foods

There has been growing concern in recent years about contamination of foods by engineered nanoparticles (NPs) due to their increasing applications in food packaging materials, pesticides, and other products. In this study, we report a systematic approach to detect, characterize, and quantify engineered NPs (i.e., zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs) in food products. A series of concentrations of ZnO and TiO₂ NPs from 0.05 to 1 wt% were spiked into corn starch, yam starch, and wheat flour. The presence of engineered NPs in foods was detected and measured by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The average sizes of ZnO and TiO₂ NPs were around 38 and 40 nm in diameter, respectively. Most ZnO NPs were in either spherical or rod-like shape, while most TiO₂ NPs were in a spherical shape. The concentrations of engineered NPs in food samples were measured by inductively coupled plasma optical emission spectrometry. Calibration curves were plotted for quantification of NPs in foods (R ²?=?0.984 and 0.995 for ZnO NPs in corn starch and wheat flour, respectively; R ²?=?0.992 and 0.998 for TiO₂ NPs in yam starch and wheat flour, respectively). The results of this study could help develop systematic methodologies for detection, characterization, and quantification of NPs in food matrices.     

Pt-Pd/UCNTs无酶生物传感器的研制与葡萄糖检测的应用

研究了铂-钯/裂解碳纳米管(Pt-Pd/UCNTs)无酶生物传感器的研制及其对葡萄糖的电催化性能。扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和循环伏安法(CV)分析发现,沉积的Pt-Pd金属纳米粒子颗粒均匀,且很好地分散在UCNTs修饰电极的表面上;与UCNTs、Pd/UCNTs和Pt/UCNTs修饰电极相比,Pt-Pd/UCNTs复合修饰电极对葡萄糖氧化具有更强的催化活性(如催化响应快和催化电流大),对葡萄糖检测有更好的选择性。