Role of Pd(0) particles in oxidation of lower olefins in the catalytic system Fe(III)_Pd/ZrO<Subscript>2</Subscript>

Oxidation of metallic Pd(0) particles applied onto an oxide support with Fe(III) ions in a concentration not exceeding 0.06 M at 70°C was studied. In contrast to palladium black, with the supported catalyst Pd/ZrO₂ Pd(II) is formed in the solution in the concentration corresponding to the thermodynamic equilibrium. With an increase in the initial Fe(III) concentration, the equilibrium yield of Pd(II) increases. The initial reaction rate grows with an increase in the weight of the initial Pd-containing catalyst and in the initial Fe(III) concentration. The revealed kinetic relationships of the dissolution of Pd(0) in the reaction with Fe(III) aqua ions allow a conclusion that, in oxidation of lower olefins C₂-C₄ in the catalytic system Fe(III)_Pd/ZrO₂ in aqueous solution, Pd(II) is regenerated in the catalytic cycle by oxidation of Pd(I) species, rather than of Pd(0), with Fe(III) aqua ions.     

Tuning the selectivity of two chemosensors to Fe(III) and Cr(III)

Two rhodamine-based chemosensors (1 and 2) were designed, and their sensing behavior toward metal ions was investigated by fluorescence spectroscopies. 1 and 2 achieved tuning the selectivity to Fe(III) and Cr(III) in 100% aqueous solution, whereas other ions including Cd(II), Co(II), Cu(II), Ni(II), Zn(II), Mg(II), Ba(II), Pb(II), Na(I), and K(I) induced basically no spectral change, which constituted a Fe(III)-selective and a Cr(III)-selective fluorescent chemosensor, respectively.     

Thermodynamic and Kinetic Studies for the Adsorption of Fe(III) and Ni(II) Ions From Aqueous Solution Using Natural Bentonite

In this study, the adsorption behavior of natural bentonite with respect to Fe(III) and Ni(II) has been studied in order to consider its application to purity metal finishing wastewaters. During the adsorption process, batch technique is used, and the effects of pH, bentoite amount, temperature, heavy metal concentration, bentonite treatment (calcinations of natural bentonite at 700°C, washing by deionized water to remove the excess salt from bentonite surface), and agitation time on adsorption efficiency are studied. The washed and calcined bentonite samples were labeled by WB and CB, respectively. The pH-dependence of Fe(III) and Ni(II) sorption on the bentonite is significantly more noticeable, indicating a major contribution of surface complexation at the edge sites. It was determined that adsorption of Fe(III) and Ni(II) is well fitted by the second order reaction kinetic. Furthermore, the sorption rate of Fe(III) was higher than the sorption rate of Ni(II). Adsorption of Fe(III) and Ni(II) on NB appeared to follow Langmuir isotherm. In addition, calculated and experimental adsorbed amounts of Fe(III) by the unit NB mass are very higher than Ni(II). The paper also discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. Also the adsorption capacity of bentonite for Fe(III) Ni(II) and increases with increased bentonite dose. According to the equilibrium studies, the selectivity sequence can be given as Fe(III) > Ni(II). The adsorbed amount of Fe(III) and Ni(II) on washed bentonite (WB) were very higher compared to NB and CB. Our results show that bentonite could especially WB be considered as a potential adsorbent for Fe(III) and Ni(II) removal from aqueous solutions.     

Triple channel sensing of Pb(II) ions by a simple multiresponsive ferrocene receptor having a 1-deazapurine backbone

A new redox, chromogenic, and fluorescent chemosensor molecule based on a deazapurine ring selectively senses aqueous Pb2+ in acetonitrile over other metal ions examined: redox shift (DeltaE1/2 = 0.15 V of the Fe(II)/Fe(III) redox couple), the colorless to orange color change, and an emission change of 620-fold, with an unprecedented detection limit of 2.7 microg L-1. The signal transduction occurs via a reversible CHEF with this inherent quenching metal ion.     

Selective detection of Fe2+ by combination of CePO4:Tb3+ nanocrystal-H2O2 hybrid system with synchronous fluorescence scan technique

A new method for quenching kinetic discrimination of Fe(2+) and Fe(3+), and sensitive detection of trace amount of Fe(2+) was developed by using synchronous fluorescence scan technique. The principle of this assay is based on the quenching kinetic discrimination of Fe(2+) and Fe(3+) in CePO(4):Tb(3+) nanocrytals-H(2)O(2) hybrid system and the Fenton reaction between Fe(2+) and H(2)O(2). Stable, water-soluble and well-dispersible CePO(4):Tb(3+) nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS). We found that both Fe(2+) and Fe(3+) could quench the synchronous fluorescence of CePO(4):Tb(3+) nanocrytals-H(2)O(2) system, but their quenching kinetics velocities were quite different. In the presence of Fe(3+), the synchronous fluorescent intensity was unchanged after only one minute, but in the presence of Fe(2+), the synchronous fluorescent intensity decreased slowly until 28 min later. The Fenton reaction between Fe(2+) and H(2)O(2) resulted in hydroxyl radicals which effectively quenched the synchronous fluorescence of the CePO(4):Tb(3+) nanocrystals due to the oxidation of Ce(3+) into Ce(4+) by hydroxyl radicals. Under optimum conditions, the linear range for Fe(2+) is 3 nM-2 μM, and the limit of detection is 2.0 nM. The method was used to analyze water samples.     

Insight into the binding evaluation of two antitumor Pd(II) complexes with human serum albumin

The interaction between two novel water-soluble palladium(II) complexes (Pd(bpy)(pyr-dtc)]NO₃, complex I and ([Pd(phen)(pyr-dtc)]NO₃, complex II, where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and pyr-dtc = pyrrolidinedithiocarbame) and human serum albumin (HSA) was investigated by fluorescence quenching spectroscopy, synchronous, fluorescence resonance energy transfer (FRET) and three-dimensional fluorescence combined with UV–Vis absorption spectroscopy and circular dichroism technique under simulative physiological conditions. Fluorescence analysis demonstrated that the quenching mechanism of HSA by Pd(II) complexes was static fluorescence quenching and hydrogen bonds and van der Waals interactions were the main intermolecular force based on thermodynamic data. The HSA–Pd(II) complex interaction had a high affinity of 10⁵ M^?1, and the number of binding sites n is almost 1. The results of synchronous fluorescence, three-dimensional fluorescence spectra, UV–Vis absorption and CD spectroscopy indicated that these two complexes may induce the microenvironment around the tryptophan residues and the conformation of human serum albumin. The binding distance (r) in the interaction between Pd(II) complex and HSA was estimated by the efficiency of fluorescence resonance energy transfer (FRET). Furthermore, results from multiple spectroscopic studies are consistent and indicate that the antitumor Pd(II) complexes can efficiently bind with human serum albumin molecules, providing a reasonable model that can help in understanding the design, transportation and toxic effects of anticancer agents.     

Sorption of As(V) on aluminosilicates treated with Fe(II) nanoparticles

Adsorption of arsenic on clay surfaces is important for the natural and simulated removal of arsenic species from aqueous environments. In this investigation, three samples of clay minerals (natural metakaoline, natural clinoptilolite-rich tuff, and synthetic zeolite) in both untreated and Fe-treated forms were used for the sorption of arsenate from model aqueous solution. The treatment of minerals consisted of exposing them to concentrated solution of Fe(II). Within this process the mineral surface has been laden with Fe(III) oxi(hydroxides) whose high affinity for the As(V) adsorption is well known. In all investigated systems the sorption capacity of Fe(II)-treated sorbents increased significantly in comparison to the untreated material (from about 0.5 to >20.0 mg/g, which represented more than 95% of the total As removal). The changes of Fe-bearing particles in the course of treating process and subsequent As sorption were investigated by the diffuse reflectance spectroscopy and the voltammetry of microparticles. IR spectra of treated and As(V)-saturated solids showed characteristic bands caused by Fe(III)SO(4), Fe(III)O, and AsO vibrations. In untreated As(V)-saturated solids no significant AsO vibrations were observed due to the negligible content of sorbed arsenate.     

Thiocarbamoylation of Chlorosulfonated Polystyrene for Preparing Sorbents for Noble Metal Ions

A new sorbent for noble metal ions, ensuring selective recovery of Au(III) ions from aqueous solutions containing interfering 3d metal ions, was suggested. The new functional derivative, poly(thiocarbamoylsulfostyre ne), was prepared by treatment of poly(chlorosulfostyrene) with thiourea. At the total degree of functionalization with sulfo and thiourea groups of up to 1.0, the degree of thiocarbamoylation can be controlled in the range from 10 to 75%. The composition and structure of the polymer-analogous transformation products were characterized by elemental analysis, Fourier IR spectroscopy, and thermal gravimetric analysis with IR identification of the decomposition products. Evaluation of the sorption activity of poly(thiocarbamoylsulfostyrene) has shown that the sorbent takes up Au(III) ions virtually quantitatively with high selectivity from an aqueous solution containing Co(II), Fe(III), Pd(II), and Ni(II) ions.     

Effect of the pH on the complexation of Cu(II), Ni(II) and Fe(III) Ions by a vine leaf litter extract by fluorescence quenching

An extract of dead vine leaves (vitis viniferal) (VLE) was obtained by the extraction procedure for fulvic acids and its interaction (at a concentration of 25mg/L in 0.1 M KNO₃) with the Cu(II), Ni(II) and Fe(III) ions was studied in the pH range between 3 and 6. This interaction was monitored by synchronous molecular fluorescence, since bands due to the fluorescent ligands undergo quenching upon complex formation. After the chemometric isolation of the quenching profiles from the raw spectra by a self-modeling mixture analysis, SIMPLISMA, they were analyzed by two methods: (i) graphical procedures based on the Stern-Volmer model; and (ii) a non-linear least-squares procedure. For the Cu(II) and Ni(II) ions, the treatment by these two methods provided similar values both for the logarithm of the conditional stability constants (log Kc) and the percentage of fluorescent structures that do not participate in the complexation. The log Kc were (standard deviations in parenthesis): Cu(II) ion, 2.4 (3), 3.37(3), 4.4(1) and 4.92(9), respectively, for pH = 3, 4, 5 and 6; Ni(II)ion, 2.9(1), 3.3(2), and 4.09(3), respectively, for pH = 4, 5 and 6. For Fe(III) an interaction with VLE was observed, but no values for Kc could be obtained.     

Concatenation of two molecular switches via a Fe(II)/Fe(III) couple

[reaction: see text] Modulation of the fluorescein fluorescence in the presence of spiropyran and ferric ion by light was observed. Such fluorescence modulation was due to the low oxidation potential of complex MC.Fe(2+), which made the electron transfer from MC.Fe(2+) to Flu(+)()(*)() thermodynamically favorable. As a result, the communication between two molecular switches based on fluorescein and spiropyan, respectively, was realized via the reversible Fe(III)/Fe(II) redox couple. The communicating behavior corresponds well to the function of an INHIBIT logic gate.     

Synthesis and characterisation of alkaline earth-iron(III) double hydroxides

Double hydroxides containing alkaline earth and iron(III) ions were synthesised by the co-precipitation method. The solid materials obtained were characterised by a range of instrumental methods (powder X-ray diffractometry, thermogravimetry, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, elemental maps, and infrared spectroscopy). It was found that the Ca(II)Fe(III), Mg(II)Fe(III), and Ba(II)Fe(III) double hydroxides had layered structures, while Sr(II)Fe(III) had not. The optimum conditions for synthesis of Ca(II)Fe(III)-layered double hydroxides (materials to be used in further studies) were also elaborated.     

Fluorescence quenching of anthropogenic fulvic acids by Cu(II), Fe(III) and UO(2)(2+)

The quenching of the fluorescence of three anthropogenic fulvic acids (FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO₂²⁺ (pH 3.5), was analyzed by a non-linear method and by Stern-Volmer plots. The FA samples were extracted from composted sewage sludges (csFA), composted municipal wastes (mwFA) and composted livestock wastes (lsFA). Synchronous-scan fluorescence (SyF) spectra were collected as a function of metal ion concentration. Spectral data were treated by a self-modeling mixture analysis method (SIMPLISMA) to detect the SyF spectral band with the strongest quenching and to calculate the corresponding quenching profile. The analysis of these profiles by a non-linear method allowed the estimation of conditional stability constants (K) and of the percentage of non-complexing fluorophores. The same quantitative information was obtained by the modified Stern-Volmer equation taking into account the existence of fluorophores that do not participate in the complexation. Good agreement was found between the results of the two procedures. The log K calculated by the non-linear method were (standard deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1); UO₂²⁺, 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO₂²⁺, 4.7 (3); lsFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO₂²⁺, 3.6 (2).     

Luminol-K2S2O8体系中金属离子化学发光行为的研究

报导了在自行设计的流动注射式化学发光分析仪上,对Luminal-K2S2O8体系中32种金属离子的化学发光行为的系统研究.确定了对金属离子的最优测定条件以及大多数金属离子的检出极限和线性范围.     

Extraction of the Pd(II)-SCN−-But4N+ ion pair by chloroform: Spectrophotometric determination of palladium

The palladium(II)-thiocyanate complex forms with the tetrabutylammonium ion a water-insoluble ion pair. The present work studies the variables affecting the extraction efficiency from aqueous to chloroformic solutions, this efficiency being in the order of 99.5% in the optimal conditions. A procedure for the spectrophotometric determination of Pd after extracting this compound by CHCl₃ is proposed. Gold(III), Pt(IV), Fe(III), Bi(III), Ti(IV), and Co(II) interfere; fluoride is used to mask Fe(III) and Ti(IV).     

2.2 Organic industrial products

Summary Highly sensitive and selective spectrofluoriphotometric determinations of iron(III) with fluorescein(Fl)-hydrogen peroxide-triethylenetetramine (TETA), and manganese(II) with Fl-hydrogen peroxide-TETA-tiron are proposed. The methods are based on the inhibition of the oxidizing decomposition of Fl-hydrogen peroxide solution in the presence of iron(III)-TETA or manganese(II)-TETA-tiron combination. The calibration graphs are linear in the ranges of up to 220 ng iron(III) and up to 270 ng manganese(II) per 25 ml at an emission wavelength of 510 nm with excitation at 490 nm. By measuring the difference of relative fluorescence intensities (F) between Fl-TETA-hydrogen peroxide and its iron(III) solutions or Fl-TETA-tiron-hydrogen peroxide and its manganese(II) solutions, the concentrations of iron(III) or manganese(II) are determined. The application of these methods to the analysis of iron(III) or manganese(II) in waste water was investigated with satisfactory results.

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Hochempfindliche und selektive fluorimetrische Bestimmungsmethoden für Eisen(III) und Mangan(II) mit Fluorescein/H₂O₂/Triethylentetramin bzw. Fluorescein/H₂O₂/Triethylentetramin/Tiron

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Application of xanthene derivatives in analytical chemistry. Part LXXVIII. Part LXXVII see ref. [1]     

Selective sensing of Fe3+ based on fluorescence quenching by 2,6-bis(benzoxazolyl)pyridine with beta-cyclodextrin in neutral aqueous solution

A selective and sensitive fluorescent chemosensor (BBOZP-CD) for Fe(3+) was composed of water-soluble beta-cyclodextrins and 2,6-bis(benzoxazolyl)pyridine which was synthesized through the reaction of 2,6-pyridinedicarboxylic acid and o-aminophenol catalyzed by polyphosphoric acid under microwave irradiation. The chemosensor BBOZP-CD for metal ions were carefully investigated by fluorescent quenching in present of metal ions. The result showed BBOZP-CD chemosensor was remarkable fluorescence quenching and a highly selectivity and sensitivity for Fe(3+) in neutral aqueous solution, and the other common metal ions did not notably disturb the detection of Fe(3+). Additionally, the effect of pH to the chemosensor for Fe(3+) was also studied. The result indicated the respond signals of BBOZP-CD to Fe(3+) was stable and hardly influenced while the pH value was greater than 3.6.     

Polymer-Enhanced Ultrafiltration of Fe(III) and Cu(II) Aqueous Solutions Using Poly(Vinyl Alcohol)-Alginic Acid/Cellulose Membranes

This study deals with the removal of Fe(III) and Cu(II) from dilute aqueous solutions using a polymer-enhanced ultrafiltration process. The ultrafiltration studies were carried out in batch stirred cell and the applied pressure was controlled by nitrogen gas. Properties of the composite membranes and its application in metal removal from aqueous solutions were studied. A composite poly(vinyl alcohol)-alginic acid/cellulose membranes were prepared by coating poly(vinyl alcohol)-alginic acid mixture solutions on the filter paper. Poly(vinyl alcohol) and alginic acid were also used as complexing agents to enhance the retention of metal ions. In the filtration of Fe(III) and Cu(II) solutions, the effects of membrane contents, pressure and pH on the retention and the flux were studied. The maximum retention of metals was found as 99% for Fe(III) solution at pressure of 45 psi, pH of 3 in the presence of poly(vinyl alcohol) as complexing agent by using 0.50 (w/v)% [(75 Poly(vinyl alcohol)/25 Alginic acid) (w/w)]/cellulose composite membranes.     

Synthesis of triazolyl anthracene as a selective fluorescent chemosensor for the Cu(II) ion

The Cu(I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) has been used to synthesize an anthracene-based fluorescent compound that undergoes strong fluorescence quenching in the presence of Cu(II). Fluorescence studies indicate that the compound forms a 1:1 complex and can be used to quantitatively determine micromolar concentrations of Cu(II) in aqueous solution.     

Development of liquid-liquid extraction and separation method for ruthenium(III) with 2-octylaminopyridine from succinate media: Analysis of catalysts

Ruthenium(III) has been efficiently extracted from 0.05 M sodium succinate at pH 9.5 by 2-octylaminopyridine in xylene and stripped with aqueous 10% (w/v) thiourea solution and determined spectrophotometrically. Various parameters viz., pH, weak acid concentration, reagent concentration, stripping agents, contact time, loading capacity, aq.: org. volume ratio, solvent has been thoroughly investigated for quantitative extraction of ruthenium(III). The utility of method was analyzed by separating the ruthenium(III) from binary mixture along with the base metals like Cu(II), Ag(I), Fe(II), Co(II), Bi(III), Zn(II), Ni(II), Se(IV), Te(IV), Al(III) and Hg(II) as well as platinum group metals (PGMs). Ruthenium(III) was also separated from ternary mixtures like Os(VIII), Pd(II); Pd(II), Pt(IV); Pd(II), Au(III); Pd(II), Cu(II); Fe(II), Cu(II); Ni(II), Cu(II); Co(II), Ni(II); Se(IV), Te(IV); Rh(III), Pd(II); Fe(III), Os(VIII). The stoichiometry 1: 2: 1 (metal: succinate: extractant) of the proposed complex was determined by slope analysis method by plotting graph of logD _[Ru(III)] versus logC _[2-OAP] and logD _[Ru(III)] versus logC _[succinate]. The interference of various cations and anions has been studied in detail and the statistical evaluations of the experimental results are reported. The method was successfully applied for the analysis of ruthenium in various catalysts, synthetic mixtures corresponding to the composition of alloys and minerals.     

荧光猝灭法和动态光散射法研究尿素-水混合溶剂中牛血清白蛋白的构象变化

利用荧光猝灭法和动态光散射法测定尿素-水混合溶剂中牛血清白蛋白(BSA)与荧光素的结合距离和BSA的流体动力学半径, 并通过分析BSA和荧光素在BSA-尿素-水和荧光素-尿素-水三元体系以及BSA-荧光素-尿素-水四元体系中荧光光谱的变化, 探讨尿素与蛋白质分子在水溶液中相互作用的机理及其对蛋白质构象的影响. 结果显示, BSA的3个结构域在尿素-水混合溶剂中具有不同的稳定性, 其中结构域III在尿素-水混合溶剂中是不稳定的, 而结构域I和结构域II分别在尿素浓度大于3.0和4.0 mol&#8226;L－1的混合溶剂中发生去折叠. 试验发现, BSA结构域II在低于去折叠浓度的尿素-水混合溶剂中形成更为紧密的构象, 这一现象可以归因于尿素与BSA结合引起的“蛋白质粘稠效应”