Synthesis,characterization and self-assembly of amphiphilic block copolymer poly(4-vinyl benzene chloride)-b-poly(N-vinylpyrrolidone) in aqueous solution

The synthesis, characterization and self-assembly of a novel amphiphilic block copolymer containing a poly(N-vinylpyrrolidone) as a segment of hydrophilic and poly(4-vinyl benzene chloride) (PVBC) arms are reported. The copolymer was characterized by FT-IR spectroscopy ¹H NMR. The composition and the molecular weights of the block copolymers were established using gel permeation chromatography and ¹H NMR. The water-soluble fraction of poly(N-vinyl-2-pyrrolidone) (PVP)/PVBC block copolymers formed micelles which were investigated at 25 °C in water at 5 mg/ml concentration using a tensiometer. The morphology of micelles in aqueous solution was determined by the AFM, SANS, and SAXS methods.     

Infrared spectra of gas-phase V(+)-(benzene) and V(+)-(benzene)(2) complexes

The organometallic ions V+-(benzene) and V+-(benzene)2 are produced by laser vaporization in a pulsed nozzle source. They are trapped and mass selected in an ion-trap/time-of-flight mass spectrometer, and their infrared spectra are measured with resonance-enhanced multiphoton photodissociation (IR-REMPD) spectroscopy with a tunable free-electron laser. Vibrational bands in the 600-1800 cm-1 region are characteristic of the benzene molecular moiety perturbed by the metal cation bonding. Experimental data are compared to the IR spectra derived from density functional calculations. Vibrational patterns in V+-(C6H6) indicate that the metal is bound in an eta6 pi-bonding configuration, while V+-(C6H6)2 is a sandwich. Trapped-ion IR-REMPD is a general method to access the vibrational spectroscopy of organometallic ions and their clusters.     

Synthesis and characterization of vanadium(IV) complexes with cis-inositol in aqueous solution and in the solid-state

The complex formation of vanadium(IV) with cis-inositol (ino) and the corresponding trimethyl ether 1,3,5-trideoxy-1,3,5-trimethoxy-cis-inositol (tmci) was studied in aqueous solution and in the solid-state. With increasing pH, the formation of [VO(H-2L)], [(VO)2L2H-5]-, [VO(H-3L)]- (L = ino) or [(VO)2L2H-6]2- (L = tmci), [V(H-3L)2]2-, and [VO(H-3L)(OH)2]3- was observed. For the vanadium(IV)/ino system, [(VO)2L2H-7]3- was observed as an additional dinuclear species. The formation constants of these complexes were determined by potentiometric titrations (25 degrees C, 0.1 M KCl). In addition, the vanadium(IV)/ino system was investigated by means of UV-vis spectrophotometric methods. EPR spectroscopy and cyclic voltammetry confirmed this complexation scheme. EPR measurements indicated the formation of three distinct isomers of the non-oxo complex [V(H-3ino)2]2- in weakly basic solution. This type of isomerism, which is not observed for the vanadium(IV)/tmci system, was assigned to the ability of ino to bind the vanadium(IV) center with three alkoxo groups having either a 1,3,5-triaxial or an 1,2,3-axial-equatorial-axial arrangement. The structures of [V(H-3ino)2][K2(ino)2].4H2O (1) and [Na6V(H-3ino)2](SO4)2.6H2O (2) were determined by single-crystal X-ray analysis. In both compounds, the coordination of each ino molecule to the vanadium(IV) center via three axial deprotonated oxygen donors was confirmed. The centrosymmetric structure of the coordination spheres corresponds to an almost regular octahedral geometry with a twist angle of 60 degrees. The crystal structure of the potassium complex 1 represents an unusual 1:1 packing of [V(H-3ino)2]2- dianions and [K2(ino)2]2+ dications, in which both K+ ions have a coordination number of nine and are bonded simultaneously to a 1,3,5-triaxial and an 1,2,3-axial-equatorial-axial site of ino. In 2, the [V(H-3ino)2]2- complexes are surrounded by six Na+ counterions that are bonded to the axial alkoxo oxygens and to the equatorial hydroxy oxygens of the cis-inositolato moieties. The six Na+ centers are further interlinked by bridging sulfate ions. According to EPR spectroscopy, the D3d symmetric structure of the [V(H-3ino)2]2- anion is retained in H2O, in dimethylformamide, and in a mixture of CHCl3/toluene 60:40 v/v.     

Formation and stability of zinc(II) and cadmium(II) citrate complexes in aqueous solution at various temperatures

The citrate complexes of Zn(2+) and Cd(2+) have been investigated by pH titration at I = 0.1 M (KNO(3)) and 10, 25, 35 and 45 degrees . The species found were [Zn(cit)](-), [Zn(cit)H], [Zn(cit)(2)](4-) and [Zn(2)(cit)(2)H(-)(2)](4-), [Cd(cit)](-), [Cd(cit)H], [Cd(cit)(2)](4-) and [Cd(cit)H(-1)](2-). From the dependence of the formation constants on temperature, DeltaH degrees and DeltaS degrees values were calculated. Speciation in the Zn(2+)]- and Cd(2+)-citrate systems is discussed with particular attention to formation of polynuclear species. Some comparisons with literature data are made.     

Selective extraction of Hg(II) from aqueous mineral acid solution containing iodide ions using 2-benzylpyridine in benzene

A method for the selective extraction of mercury has been developed. The extraction of Hg(II) by 2-benzylpyridine (BPy) in benzene from dilute mineral acid solution containing iodide ions has been investigated, and variables such as concentration of acids, iodide and the extractant have been optimized. The optimum conditions for the extraction of Hg(II) by 0.1M BPy/benzene are: 0.01M (HCl, HNO₃, H₂SO₄)+0.01M KI. The distribution coefficients and separation factors of 19 elements relative to Hg(II), have been reported. Effect of anions such as ascorbate, acetate, citrate, oxalate and thiosulfate has also been studied. The method developed could find useful applications in selective extraction of small amounts of mercury from environmental samples.     

TiOCl2溶液合成异形TiO2纳米粉及形成机理研究

以TiOCl2溶液为前驱物,由室温至180℃直接反应均可获得TiO2纳米晶。当反应温度低于70℃,100℃和160℃时,沉淀粒子形貌分别为针形聚集体、球型和针形单晶。相应反应温度下所得沉淀的晶型分别为金红石型、混晶和金红石型。晶体的形貌和粒子的均一性强烈依赖于反应温度和成核与成长速率。详细讨论了TiOCl2溶液在各个温区的水解及TiO2粒子的形成机理。     

Synthesis and characterization of 1,3-bis(2-hydroxyethoxy) benzene based saturated and unsaturated polyesters

Polyesterification of adipic acid and maleic anhydride with 1,3-bis(2-hydroxyethoxy)benzene (HER) in the presence of toluene-4-sulphonic acid was carried out using melt condensation technique. The structural characterization of the synthesized polyesters had been carried out using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopic methods. The thermal properties of the polyesters were studied using differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The activation energies for the thermal degradation of the polyesters were calculated by the method of Dharwadkar and Kharkhanavala and discussed. The char residue value at 600 °C indicated maleic anhydride based polyester is thermally more stable compared to the adipic acid based polyester. The mechanism of degradation of these polyesters is discussed.     

Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder

Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media.     

Extraction of iron(III) with diphenyl-2-pyridylmethane dissolved in benzene from aqueous chloride solutions

The mechanism of extraction has been investigated by partition, slope analysis and loading-ratio data. The results obtained give a picture of the mechanism of extraction of FeCl ₄ ⁻ ions in relation to the hydration and solvation of the compound extracted. The possible formula of the extracted species is (DPPM)₃H₃O⁺(H₂O)_n−FeCl ₄ ⁻ . In dilute aqueous hydrochloric acid systems the influence of the concentration of a number of salts with cations of different electrical potentials (Ze/r), on iron(III) extraction, has been studied. Splitting of the organic phases occurs at high acid and/or high salt concentrations. The phenomenon is explained on the basis of the variability of the hydration number. Investigations have been made to understand the parameters controlling the extraction of the metal and its is shown that the extraction offers a simple, fast and selective separation method of iron from solutions.     

Distribution of the iron(III)-ethyl acetoacetate complex between aqueous solution and benzene

Summary Studies have been made on the distribution of iron(III)-ethyl acetoacetate complex between aqueous solution and benzene. Effect of pH, concentration of ethyl acetoacetate and shaking conditions were chosen as experimental parameters. Iron(III) can be well extracted from aqueous solution of pH 4.4–9.8 into benzene with constant extractability (97%), if the concentration of ethyl acetoacetate is kept in excess over that of iron(III). The applicability of the complex ( _max: 452 nm) to the spectrophotometric determination of iron is also discussed.

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Verteilung des Eisen(III)-Acetessigester-Komplexes zwischen wä\riger Lösung und Benzol

Zusammenfassung Zur Untersuchung der Verteilung wurden der pH-Wert, die Konzentration an Acetessigester und die Ausschüttelungsbedingungen variiert. Eisen(III) kann bei pH 4.4–9.8 mit Benzol mit einer konstanten Extrahierbarkeit von 97% ausgeschüttelt werden, wenn die Konzentration an Acetessigester größer ist als die an Eisen(III). Die Anwendbarkeit des Komplexes ( _max: 452 nm) zur spektralphotometrischen Eisenbestimmung wird diskutiert.

     

Synthesis of high molecular weight polystyrene and poly(methyl methacrylate) with low polydispersity by [Cp2ZrCl2] catalyzed aqueous polymerization

An early transition metal metallocene compound, Cp₂ZrCl₂, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier has been found to be an effective catalyst for polymerization of monomers like styrene and methylmethacrylate in aqueous medium. The molecular weights of the polymers have been found to be very high with low molecular weight distribution. The added surfactant has been found to play the dual role of stabilizer of the cation as well as an emulsifying agent for the monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3797–3803, 2005     

[Cu2I2(C8H6N2)]∞晶体的水相合成与表征

近年来,d10金属配位聚合物的合成、结构和性质的研究引起了人们广泛的兴趣[1-3],CuXL(X＝Cl、Br和I,L＝含氮配体)配合物由于其结构的多样性和独特的发光性质而成为活跃的研究领域[1-10].     

Removal of low concentration Cr(VI) from aqueous solution by magnetic-fluids fixed bed using the high gradient magnetic separation

The focus of this paper was a novel model of Cr(VI) extraction process. The original so-called "magnetic-fluids fixed bed" (MFFB), which bridged the solvent extraction and the fixed-bed extraction by the theory of the high gradient magnetic separation (HGMS), has been explained. The MFFB integrated the advantages of the two above mentioned classical extraction methods and overcame their drawbacks. The feasibility of this method was studied by extraction experiments of Cr(VI) from aqueous solution. The influences of the design of ferromagnetic steel wires in magnetic separation column, the pH value of feed solution, TBP concentration in magnetic fluids, and flow rate of aqueous solution in column were investigated. Under the optimum conditions, the proposed method obtained high extraction efficiency with continuous process.     

CeO2纳米管负载Pd纳米颗粒催化CO低温氧化

高效负载型Pd催化剂的制备及其在CO低温氧化反应中的机理探究是近年来的研究热点.普遍认为,Pd催化剂上的CO氧化反应遵循Langmuir-Hinshelwood机理:首先,CO吸附于Pd物种表面;然后,CO与催化剂表面的晶格氧发生反应转化为CO2,反应发生在金属-载体界面.另外,高分散的Pd活性物种有利于CO氧化反应.同时载体的形貌、暴露的晶面、氧空位以及孔结构等都是影响催化剂活性的重要因素.CeO2纳米管具有独特的管状特征和较高的比表面积,是一种潜在的CO低温氧化催化剂载体.本文利用乙醇还原法,以CeO2纳米管为载体,制备不同Pd含量的Pd/CeO2-nanotube纳米催化剂,并利用N2吸附脱附、X射线衍射(XRD)、透射电子显微镜(TEM)、CO程序升温脱附(CO-TPD)、X射线光电子能谱(XPS)等表征手段,探索纳米催化剂载体形貌对CO氧化反应活性的影响.氮气吸脱附结果表明,Pd/CeO2-nanotube具有较高的比表面积(58.0 m2/g),且存在介孔结构.XRD表征发现,Pd/CeO2-nanotube的衍射峰对应立方萤石型结构的CeO2的(111),(200),(220),(311)等品面.TEM结果表明,Pd/CeO2-nanotube具有均匀的纳米管形貌,其外径为40-60 nm,Pd纳米颗粒均匀分散在其表面.CO-TPD结果表明,Pd/CeO2-nanotube在1 10℃附近具有很强的脱附峰,在370℃和600℃附近分别具有较宽和较弱的脱附峰,这表明该催化剂具有较多的吸附位,且具有很强的CO吸附能力;CO不可逆吸附量计算结果表明,该催化剂上的Pd具有很高的表面分散度(23.3％),Pd颗粒尺寸为7.3 nm.XPS表征显示,Pd以pd2+的形式分散于CeO2纳米管的表面,且与载体发生相互作用,存在Pd-O-Ce键;同时该催化剂表面存在丰富的Ce3+,为反应提供更多的氧空位.0.9Pd/CeO2-nanotube纳米催化剂在CO氧化反应中表现出优良的活性,能在100℃实现CO的完全转化;通过计算发现,该催化剂具有较高的TOF值(0.63 s-1),由Arrhenius 曲线可得到该催化剂的活化能为26.5 kJ/mol.综上可见:金属活性组分的尺寸和分散度、载体的结构特征、CO吸附能力以及金属-载体间的相互作用决定催化剂的性能.Pd/CeO2-nanotube的高比表面积有利于Pd的分散;其强CO吸附能力有利于CO吸附于Pd物种表面;催化剂表面丰富的Ce3+能为反应提供更多的氧空位,Pd-O-Ce键的形成能增强金属-载体间的相互作用,有利于CO与催化剂表面品格氧发生反应.同时催化剂介孔结构有利于反应气体和产物气体的吸附和扩散,因此,Pd/CeO2-nanotube纳米催化剂在CO氧化反应中表现出优良的活性.     

Preparation and characterization of nanosized TiO2 powder as an inorganic adsorbent for aqueous radionuclide Co(II) ions

In this research TiO₂ sample was synthesized by a simple sol–gel method and was characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques. The XRD result indicated that the obtained product was anatase titanium dioxide with high purity, the TEM image clearly showed that the particle sizes of TiO₂ nanoparticles were in the range of 30–70 nm, and the measured BET surface area of the heated TiO₂ nanoparticles was 147.14 m²/g. In this work, the prepared TiO₂ sample was used as a new adsorbent for the adsorption of radionuclide Co(II) ions from aqueous solutions, and the influence of pH, contact time, ionic strength and temperature in the presence or absence of humic acid/fulvic acid (HA/FA) were also investigated. The experimental results indicated that the adsorption of Co(II) ions onto TiO₂ was strongly pH-dependent. Based on the surface complexation, the presence of HSs enhanced the adsorption of Co(II) ions and the influence of Co(II) adsorption onto FA–TiO₂ hybrids was much stronger than that of HA–TiO₂ at pH values of 2.0–9.0. Adsorption of Co(II) ions onto TiO₂ powder was strongly dependent on ionic strength. The adsorption process mainly occured in the first contact time of 2 h and could be fitted by a pseudo-second-order rate model. The calculated thermodynamic data indicated that the adsorption of Co(II) ions onto TiO₂ was a spontaneous process and favorable at high temperatures.     

Metallacrown ethers with a symmetric bis(phosphite) ligand derived from 1,2-bis-(2-hydroxyethoxy)benzene: Synthesis, characterization and hydroformylation of styrene

To better understand the effects of ligand configuration on hydroformylation reactions carried out in the presence of LiBPh₄·3dme (dme = 1,2-dimethoxyethane), a conformationally restrained bis(phosphite) ligand derived from 1,2-bis-(2-hydroxyethoxy)benzene, {[(2,2′-O₂C₁₂H₈)P(C₂H₄O₂)]₂C₆H₄}, 1, has been prepared and its Rh(I) metallacrown ether complex has been evaluated as a catalyst for the hydroformylation of styrene. Both the activity and regioselectivity of the catalyst are sensitive to the amount of the LiBPh₄·3dme added with the activity decreasing by 16% and the regioselectivity for the iso increasing by 9% at a 8:1 LiBPh₄:Rh ratio.Model complexes for the octahedral, cis-Mo(CO)₄(1), 2, and square planar, cis-PtCl₂(1), 3, and cis-PdCl₂(1), 4, complexes in the catalytic cycle has been have been studied using multinuclear NMR spectroscopy and X-ray crystallography. Although the X-ray crystal structure of 2 suggests that the metallacrown ether ring could adopt a configuration capable of binding alkali metal cations, this does not appear to occur in a dichloromethane-d₂ solution of 2 because no shift in the ³¹P NMR resonance 2 is observed upon the addition of an excess of LiBPh₄·3dme. The ³¹P{¹H} NMR spectra of chloroform-d solutions of 2 (in the presence of a catalytic amount of HgCl₂) and of 4 and the X-ray crystal structures of the complexes indicate that the bis(phosphite) ligands are cis coordinated in these complexes in both the solution and in the solid state. This is particularly surprising for 4 because related PdCl₂{Ph₂P(CH₂CH₂O)_nCH₂CH₂PPh₂} (n = 3-5) complexes exhibit both cis-trans and monomer-oligomer equilibria in solution.     

Synthesis and solution characterization of [Ru(bpy)2]2+ modified polyazines

A series of [Ru(bpy)(2)](2+) complexes linked by a controlled number of azine units (one to seven) were synthesized and studied in the solution phase. Polymers and dimer model compounds were examined by cyclic voltammetry and IR, NMR, and visible-NIR spectroscopies. The NMR spectra and the cyclic voltammograms indicated that the Ru(2+) sites influenced the main chain properties at least 15 A from the metal site. The first oxidation in each material was assigned to a ligand-centered process, but DFT calculations suggested that the Ru(2+) has an important influence. The first oxidized state of the polymers has a spectroscopic band that is consistent with an intervalence transfer (IT) transition, but this absorption is not seen in the dimer model compounds. Thus, the IT feature is assigned to a ligand-ligand transition that spans several repeat units in the polymer.     

Preparation and characterization of magnetic chitosan nanocomposites for removal of Cu2+ from aqueous solution

In this article, highly efficient magnetic chitosan nanoparticles were prepared by the glutaraldehyde cross-linking method and then chemically-modified with amino groups through reaction between triethylenetramine and glycidyl methacrylate. The adsorption kinetics and isotherms of these novel adsorbents fit the pseudo-second-order model and the Langmuir model. The maximum adsorption capacities were 293?mg/g at pH?=?4.3 and t?=?1.4 hours. The rate-limiting step was the chemical adsorption. Further recycling experiments showed that the adsorbent provided the potential regeneration and reuse after adsorbing Cu²⁺. All the experimental results demonstrated that the adsorbent had a potential application in Cu²⁺ removal from wastewater.