On the nature of the silver phases of Ag/Al2O3 catalysts for reactions involving nitric oxide

The nature of the silver phases of Ag/Al₂O₃ catalysts (prepared by silver nitrate impregnation followed by calcination) was investigated by X-ray diffractograms (XRD), transmission electron microscopy (TEM) and UV–VIS analyses and related to the activity of the corresponding materials for the oxidation of NO to NO₂. The UV–VIS spectrum of the 1.2 wt.% Ag/Al₂O₃ exhibited essentially one band associated with Ag⁺ species and the NO₂ yields measured over this material were negligible. A 10 wt.% Ag/Al₂O₃ material showed the presence of oxidic species of silver (as isolated Ag⁺ cations and silver aluminate), but the UV–VIS data also revealed the presence of some metallic silver. The activity for the NO oxidation to NO₂ of this sample was moderate. The same 10% sample either reduced in H₂ or used for the C₃H₆-selective catalytic reduction (SCR) of NO showed a significantly larger proportion of silver metallic phases and these samples displayed a high activity for the formation of NO₂. These data show that the structure and nature of the silver phases of Ag/Al₂O₃ catalysts can markedly change under reaction feed containing only a fraction of reducing agent (i.e. 500 ppm of propene) in net oxidizing conditions (2.5% O₂). The low activity for N₂ formation during the C₃H₆-SCR of NO (reported in an earlier study) over the high loading sample can, therefore, be related to the presence of metallic silver, which is yet a good catalyst for NO oxidation to NO₂. The reverse observations apply for the oxide species observed over the low loading sample, which is a good SCR catalyst but do not oxidize NO to NO₂.     

Novel phthalocyanine polymers with very flexible pentathiatetraethylene units

A series of polymeric metal-free and metallophthalocyanine (M = 2H, Ni, Co, Fe, Pb, Cu and Zn) polymers were prepared by polymeric tetramerization reaction of bisphthalonitrile monomer with proper materials. The Co–phthalocyanine polymer was prepared by two different methods. The metal-free (3) and the Co-containing phthalocyanine polymer (5) were chemically doped with iodine (I₂) and nitrosyl tetrafluoroborate (NOBF₄), respectively. The electrical conductivities of the polymeric phthalocyanines measured as gold sandwiches were found to be 10⁻⁸–10⁻⁴ S cm⁻¹ in vacuum and in argon. The electrical conductivities of I₂-doped metal-free phthalocyanine (3a) and NOBF₄-doped Co–phthalocyanine (5a) polymers were found to be approximately 110 and 89 times higher than those of undoped versions, respectively. The extraction ability of 3 was also evaluated in tetrahydrofuran using several transition metal picrates such as Ag⁺, Hg²⁺, Pb²⁺, Cd²⁺, Cu²⁺ and Zn²⁺. The extraction affinity of 3 for Ag⁺ was found to be highest in the heterogeneous phase extraction experiments. The aggregation and disaggregation properties of 3 were investigated with silver(I), mercury(II) and methanol as solvent. All the novel compounds were characterized by using elemental analysis, UV–vis, FT-IR, NMR and MS spectral data and DTA/TG.     

Electrochemical beaviour of the solid ionic conductor Ag7I4PO4

Electrochemical investigation of the solid superionic conductor Ag₇I₄PO₄ (0.8 AgI + 0.2 Ag₃PO₄) at room temperature and at 40°C were performed by means of cyclic voltammetry, cyclic chronoamperometry and cyclic chronocoulometry, normal pulse polarography and ac polarography. It was shown that the Ag⁺ ↔ Ag redox process on Pt and Ag working electrode occurs with a certain overvoltage, ie that for Ag⁺ → Ag⁺ oxidation and the return of Ag⁺ ions into the electrolyte a certain overvoltage is necessary. From the determined values of the exchange current one estimates the redox process as a rather fast one. The silver working electrode is electrochemically inactive, while only cathodically deposited silver is electrochemically active and can be oxidized to Ag⁺ ions. Chronoamperometry and chronocoulometry show that there is a certain difference in the behaviour of Pt and Ag working electrodes due to uneven passivating anodic processes. On the basis of measurements of faradaic and capacitance currents and their dependence on frequency, diagrams of complex impedance of the Pt/Ag₇I₄PO₄ interface at various anodic and cathodic polarizations of the Pt electrode were plotted. The dependence of the serial capacity of the interface on the dc potential and temperature are discussed.     

Direct evidence for purely silver ion conduction in CuI-doped silver oxysalt superionic systems: Combined electrolysis and EDS studies

Maiden attempt has been made for the direct estimation of the contributions of silver and copper ions to the ionic conductivity in superionic solids obtained in CuI-doped silver oxysalt systems. The application of the combined electrolysis and EDS techniques towards qualitative and quantitative analyses of the mobile ionic species in solid electrolyte systems having more than one possible mobile ion is reported. These studies confirmed that these electrolyte materials are purely Ag⁺ conducting up to 50 mol% CuI in xCuI–(100 − x)[2Ag₂O–0.7V₂O₅–0.3B₂O₃] and xCuI–(100 − x)[Ag₂O–0.7MoO₃–0.3WO₃] systems and small fraction of t_Cu+ exists above 60 mol% CuI. These solid electrolyte materials exhibited a high ionic transport numbers (t_i) of >0.985 and the t_i increases when two glass formers are used.     

Efficient destruction of bacteria with Ti(IV) and antibacterial ions in co-substituted hydroxyapatite films

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag⁺, Cu²⁺ or Zn²⁺) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO₂ film. The studies of ESR revealed that not only O₂⁻ was formed on HAPTiM, HAPTi, HAP and P25-TiO₂ films under weak UVA irradiation, but also at ambient temperature without light O₂⁻ was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu⁰/Cu²⁺ and Ag⁰/Ag⁺ in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O₂⁻ generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O₂⁻ and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K⁺) leakage from the killed bacteria.     

CuO改性商用选择性催化还原催化剂催化氧化单质汞性能

燃煤烟气中单质汞（Hg⁰）的高效氧化是提高燃煤电厂脱汞效率的关键,为提高传统选择性催化还原（SCR）催化剂氧化Hg⁰的性能,本文采用溶液浸渍法制备了CuO-SCR催化剂,在固定床反应装置上考察了其脱硝协同氧化单质汞性能,并借助BET、XRD和XPS等分析技术对催化剂进行表征。结果表明,CuO的掺杂显著提高了商用SCR催化剂的Hg⁰氧化性能和低温脱硝活性;在200~400℃内,随着反应温度升高和NO+NH₃浓度增大,NH₃对CuO-SCR催化剂的Hg⁰氧化性能抑制作用加强;在350℃、模拟燃煤烟气条件下,随着空速比的减小,催化剂的Hg⁰氧化性能显著提高,NH₃对Hg⁰氧化的抑制作用明显减弱。催化剂表征结果表明,CuO-SCR催化剂表面存在氧化还原反应V⁴⁺+Cu²⁺?V⁵⁺+Cu⁺,增强了催化剂的催化活性。Hg⁰在CuO-SCR催化剂表面的氧化过程遵循Mars-Maessen机制,能够有效增强催化剂的Hg⁰氧化性能。     

Ag exchange at Cds electrode surfaces

The inhibition effect of Ag⁺ ions on the photoanodic corrosion of CdS semiconductor electrodes has been studied in 0.5 M NaClO₄ + xM AgClO₄ solutions (0 x 10⁻², pH = 2) by means of potentiostatic current density-potential measurements, ac-impedance and atomic absorption. In the presence of Ag⁺ ions in the solution a thin Ag₂S film of ca. 30–300 nm thickness is formed on the CdS surface due to the heterogeneous cation exchange reaction CdS + 2Ag⁺ = Ag₂S + Cd²⁺. The Ag₂S film formation is a transport controlled process which can be described by a parabolic rate law. From kinetic investigations in the temperature range (298 T 348 K) the activation energy of this process was determined to be about 62 kJ mol⁻¹. Information about the morphology and composition of the surfaces was obtained from optical and scanning electron microscope investigations including EDAX.     

巯基聚苯乙烯树脂对FGD系统中Hg2+的脱除性能

以氯甲基化聚苯乙烯微球为原料,经过两步反应制得巯基聚苯乙烯树脂,用红外光谱测试、比表面分析、元素分析及热重分析表征了该巯基聚苯乙烯树脂,测试了此巯基聚苯乙烯树脂对含Hg²⁺烟气、脱硫废水及脱硫浆液的脱汞性能。分析测试表明:巯基聚苯乙烯树脂热稳定性好,能有效脱除烟气、脱硫废水及脱硫浆液中的Hg²⁺。巯基聚苯乙烯树脂对烟气中Hg²⁺的脱除效率大于90%,对脱硫废水及脱硫浆液的脱汞率接近100%。将此树脂置于脱硫系统内,能捕捉脱硫系统内的Hg²⁺,避免Hg²⁺进入脱硫石膏而造成脱硫石膏中汞的再释放。用6mol·L^-1盐酸洗脱捕捉了Hg²⁺的巯基聚苯乙烯树脂,再生3次后,巯基聚苯乙烯树脂的再生率仍高达90.2%。     

改性ZSM-5分子筛膜脱除苯并噻吩/2,5-二甲基噻吩

采用二次合成法合成ZSM-5分子筛膜,并用XRD和SEM对其表面进行表征,所合成的膜为ZSM-5分子筛膜。对分子筛膜用Ag⁺、Cu²⁺、Fe³⁺金属离子进行改性,改变离子浓度,然后应用于模拟汽油中苯并噻吩和2,5-二甲基噻吩的分离性能研究,同时还考察了不同料液温度、再生次数对膜脱硫的影响。实验结果表明：负载Ag⁺浓度为0.2 mol/L时对苯并噻吩和2,5-二甲基噻吩的分离效果最好,分离因子最高可达到1.65;料液温度在常温（25 ℃）下脱硫效果最好,通过简单方法对膜进行再生,考察再生膜脱硫具有较好的稳定性。     

Crown ether-thiourea conjugates as ion transporters

Na⁺,Cl^?and K⁺are the most abundant electrolytes present in biological fluids that are essential to the regulation of pH homeostasis,membrane potential and cell volume in living organisms.Herein,we report synthetic crown ether-thiourea conjugates as a cation/anion symporter,which can transport both Na+and Cl^–across lipid bilayers with relatively high transport activity.Surprisingly,the ion transport activities were diminished when high concentrations of K+ions were present outside the vesicles.This unusual behavior resulted from the strong affinity of the transporters for K⁺ions,which led to predominant partitioning of the transporters as the K⁺complexes in the aqueous phase preventing the transporter incorporation into the membrane.Synthetic membrane transporters with Na⁺,Cl^?and K⁺transport capabilities may have potential biological and medicinal applications.     

Effect of silver on the photocatalytic degradation of humic acid

In this study, humic acid was mineralized and degraded photocatalytically in presence of bare TiO₂ and silver loaded TiO₂ (0.5–5.0 at.% Ag). X-ray diffraction (XRD) and inductive coupled plasma (ICP) analysis confirm the complete photodeposition of silver over TiO₂ by photodeposition method. X-ray photoemission spectroscopy (XPS) studies confirmed the presence of Ag⁰ in all Ag–TiO₂ samples and the absence of Ag⁺ ions. Silver loading over TiO₂ improved the rate of mineralization and degradation of humic acid with a maximum loading of 1.0 at.% Ag. Ninety percent carbon from humic acid was mineralized to CO₂ only after 60 min by using bare TiO₂ as a photocatalyst. However, this conversion was possible within 40 min by using 1.0 at.% Ag-loaded TiO₂. This observation verifies that coating of metals like silver over TiO₂ acts as an electron sink and can improve the redox reaction by preventing electron–hole recombination reaction. The optimum 1.0 at.% Ag loading in the current work is indicative that the blocking of the TiO₂ surface active sites by silver also plays an important role in the photocatalytic mineralization and degradation of humic acid. As the silver loading is increased, less number of active site are available over the surface of photocatalyst TiO₂ for redox reaction. This finding was supported by the TEM analysis of the photocatalyst samples.     

Effect of Hydrogen Reduction of Silver Ions on the Performance and Structure of New Solid Polymer Electrolyte PEI/Pebax2533/AgBF4 Composite Membranes

In this paper, the effect of hydrogen reduction of silver ions on the performance and structure of new solid polymer electrolyte polyetherimide (PEI)/Pebax2533 (Polynylon12/tetramethylene oxide block copolymer, PA12-PTMO)/AgBF₄ composite membranes is investigated. For PEI/Pebax2533/AgBF₄ composite membranes prepared with different AgBF₄ concentration, the permeances of propylene and ethylene increase with the increase of AgBF₄ concentration due to the carrier-facilitated transport, resulting in a high selectivity. But for propylene/propane mixture, the mixed-gas selectivity is lower than its ideal selectivity. The hydrogen reduction strongly influences the membrane performance, which causes the decrease of propylene permeance and the increase of propane permeance. With the increase of hydrogen reduction time, the membranes show a clearly color change from white to brown, yielding a great selectivity loss. The data of X-ray diffraction and FT-IR prove that silver ions are reduced to Ag⁰ after hydrogen reduction, and aggregated on the surface of PEI/Pebax2533/AgBF₄ composite membranes.     

Co3O4 with ordered pore structure derived from wood vessels for efficient Hg0 oxidation

Catalytic oxidation of Hgo to Hg^O is an efficient way to remove Hg⁰ from coal-fired flue gas.The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg⁰ oxidation efficiency.Therefore,in the present work,wood vessels were used as sacrificial template to obtain Co₃O₄with ordered pore structure.SEM and BET results show that,when the mass concentrations of Co(NO₃)₂·6H₂O wa...     

Highly Efficient Cooperative Membrane Transport of Lead(II) Ions by Aza-18-crown-6 and Palmitic Acid

Abstract

A chloroform membrane system containing a given mixture of aza-18-crown-6 and palmitic acid was applied for the uphill transport of Pb²⁺ ions. In the presence of P₂O₇ ^4? ion as a suitable metal ion acceptor in the receiving phase, the amount of lead ion transported across the liquid membrane after 100 minutes is 89.1 ± 1.3%. The selectivity and efficiency of lead transport from aqueous solutions containing other cations such as Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe²⁺, Pd²⁺, and Ag⁺ ions were investigated. In the presence of S₂O₃ ^2? ion as a proper masking agent in the source phase, the interfering effects of Cu²⁺ ion were diminished drastically.     

苯并噻唑基修饰的开链Cu2+比色探针的合成及性能

以N-苯基二乙醇胺和2-巯基苯并噻唑为原料通过亲核取代反应合成了一种新型的苯并噻唑基修饰的开链冠醚类化合物1,并用核磁共振氢谱, 核磁共振碳谱及元素分析方法对合成产物进行了表征。利用紫外光谱仪考察了化合物1与多种金属离子（Mn²⁺、Co²⁺、Cu²⁺、Zn²⁺、Ni²⁺ 、Fe³⁺、 Hg²⁺、Cr³⁺、Al³⁺）在乙腈溶液中的光谱变化,并探究了化合物1处理过的滤纸条在水溶液中对金属离子的识别效果,通过核磁共振氢谱讨论了化合物1与金属离子形成配合物的作用机理。实验发现,化合物1的乙腈溶液中添加Cu²⁺后溶液颜色变为棕色,明显区别于添加其他离子;在水溶液中,特制的滤纸条遇到Cu²⁺会呈现黄色,而遇其他离子均无颜色变化。结果表明,化合物1仅对Cu²⁺具有选择性,且能通过裸眼进行识别,是一种高效、简便的Cu²⁺探针。     

不同烟气组分对粉状活性焦吸附汞的影响机理

在模拟燃煤热烟气为热源和介质条件下，以准东褐煤为原料，通过一维沉降炉进行炭化活化（一步法）制备粉状活性焦，考察了活性焦对Hg⁰的吸附能力，探索了SO₂、H₂O、O₂、CO₂、H₂O+O₂、SO₂+O₂及H₂O+SO₂+O₂气氛对活性焦吸附Hg⁰的影响机理。结果表明：一步法获得的活性焦对Hg⁰具有较高的吸附性能。N₂气氛作对比，H₂O、H₂O+O₂、CO₂和SO₂气氛下抑制活性焦对Hg⁰的吸附；O₂、SO₂+O₂和H₂O+SO₂+O₂促进活性焦对Hg⁰的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg⁰的抑制和促进机理。H₂O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg⁰的吸附；SO₂与Hg⁰在活性焦上发生竞争吸附而抑制对Hg⁰的吸附；CO₂ 吸附在活性焦微孔上而抑制对Hg⁰的吸附；O₂气氛下主要形成了HgO, SO₂+O₂气氛下Hg⁰被氧化成HgSO₃，进一步氧化成HgSO₄； H₂O+SO₂+O₂气氛下，Hg⁰被氧化成HgO和HgSO₄。     

Ag/BiOI光催化剂湿法脱除烟气中气态单质汞性能及机理

采用沉淀-光还原法制备了不同Ag含量的Ag/BiOI可见光催化剂,利用XRD、N₂吸附-脱附、SEM、TEM、XPS、DRS、光电流和ESR对其物化结构进行表征,在湿法鼓泡反应器脱汞装置上考察了Ag负载量、光照、SO₂和NO对气态单质汞（Hg⁰）脱除性能的影响。结果表明,与BiOI相比,Ag添加后光催化剂的脱汞效率大幅提高。当Ag负载质量分数为2%时,Ag/BiOI催化剂的脱汞效率高达98%。荧光灯辐照对Ag（2%）/BiOI催化剂的高效脱汞至关重要。与NO相比,SO₂对脱汞效率的影响颇为明显。与BiOI相比,Ag（2%）/BiOI中BiOI的边缘出现较多的Ag微颗粒,且Ag颗粒分散度较好;Ag的添加可以提高BiOI表面的化学吸附态氧含量和增强BiOI在可见光波段的吸收能力,有利于其高效脱汞。机理分析表明,超氧阴离子自由基（^•O₂^-）和空穴（h⁺）在光催化脱汞过程中起主要作用。     

温度和氧含量对NH4Br改性稻壳焦汞氧化吸附特性的影响

采用10 g·L^-1 NH₄Br溶液对原始稻壳焦进行浸渍改性制备了脱汞吸附剂。利用比表面积及孔隙度分析仪、扫描电子显微镜/X射线能谱分析仪对改性前后稻壳焦吸附剂物理化学性质进行表征。在固定床汞吸附实验台上对吸附剂床层出口元素汞(Hg⁰)和二价汞(Hg²⁺)进行同步检测,研究了不同温度下N₂气氛和N₂+6.4 %(体积)O₂气氛中改性稻壳焦的汞氧化吸附特性。50℃下N₂气氛、N₂+6.4%(体积)O₂气氛以及150℃下N₂气氛中固定床出口均未明显检测到Hg²⁺,50℃和150℃时脱汞率均可达90%。温度为150℃时,在N₂+6.4%(体积)O₂气氛中吸附剂的总汞(Hg^T)脱除效率为98.2%,其中82.2%的Hg⁰被吸附脱除,其余则被O₂非均相氧化为Hg²⁺而氧化脱除。通过对程序升温管式炉出口Hg^T进行检测研究了吸附剂表面吸附态汞的脱附特性。汞脱附峰值温度300℃表明吸附态汞可能以Hg-Br化合物的形式赋存于改性稻壳焦表面,220~350℃的脱附温度说明吸附态汞有较高的热稳定性。100.14%~118.62%的汞平衡率验证了实验结果的准确性。     

银基活性炭对废轮胎热解油的吸附脱硫机理研究

废轮胎经热解制备得到热解油和热解炭,热解炭活化制得活性炭,并利用Ag⁺对活性炭进行改性制得Ag⁺改性活性炭（Ag/AC）,将Ag/AC用于热解油的吸附脱硫实验,并利用GC/MS对热解油中的含硫化合物进行了分析。研究结果表明：活性炭吸附脱硫的合适温度和时间分别为20℃和12 h,此时未改性活性炭的脱硫率为15.33%;而Ag/AC的脱硫率提高到了38.6%。GC/MS分析发现热解油中有机硫的主要存在形式为噻吩、2-甲基噻吩、苯并噻吩、二苯并噻吩和4,6-二甲基二苯并噻吩,其中二苯并噻吩（DBT）的GC含量最高,为2.57%。利用原位红外、核磁共振氢谱、ICP-OES和元素分析等检测手段,进一步探究了Ag⁺与二苯并噻吩模型化合物在溶液中的反应机理,研究发现：二苯并噻吩分子上存在S原子和苯环2个反应位点,当Ag⁺加入二苯并噻吩溶液后,Ag⁺与二苯并噻吩分子上的S原子或者苯环发生配位数为1的配位反应生成2种配合物,分子式分别为Ag（D_S）NO₃和Ag（D_C6H6）NO₃。     

Peroxo salts as initiators of vinyl polymerization: Polymerization of acrolein initiated by potassium peroxodiphosphate

Kinetic studies were made on the polymerization of acrolein initated by potassium peroxodiphosphate (PP) in aqueous solution, in the presence and absence of Ag⁺ ions. The rate of polymerization was found to depend on [M]^3/2 (M = monomer) and was independent of both [PP] and [Ag⁺]. The overall activation energy was calculated to be 4.8 kcal mol⁻¹. A mechanism involving termination by PO^2-₄ radicals is proposed and discussed.