Factorial design for optimization of experimental variables in preconcentration of copper by a chromotropic acid loaded Q-Sepharose adsorbent

An agarose-based anion exchanger (Q-Sepharose) was loaded with chromotropic acid (CTA) and used for column preconcentration and determination of copper by flame AAS. Preliminary experiments indicated that a sample pH of 5.7-6.5 is best suited for accumulation of copper and a 2.5 ml portion of a 0.02 mol l⁻¹ HCl solution can efficiently desorb the analyte from the column. An incomplete factorial design was used for optimization of five different variables that affect recovery of copper. The results indicated that ionic strength, pH and sample volume variables are the most important effects, respectively. Hence, these variables and their possible interactions were studied more carefully. In optimized conditions, the column could tolerate up to 0.18 mol l⁻¹ sodium nitrate in the matrix. A 5 ml portion of a 0.02 mol l⁻¹ CTA was sufficient for loading of a 0.5 ml column prior to preconcentration of copper from a 150 ml sample solution. Matrix ions of Ca²⁺, Mg²⁺, Na⁺ and K⁺ and potentially interfering ions of Pb²⁺, Ni²⁺, Cd²⁺, Co²⁺, Zn²⁺ and Mn²⁺ with relatively high concentrations did not have any significant effect on the recovery of the analyte. A preconcentration factor of 60 and a detection limit of 1.0 μg l⁻¹ was obtained for the determination of copper by the flame AAS method. A precision better than 2.5%, expressed as R.S.D., was also achieved. Application of the method to tap water and two different river water samples resulted in values well confirmed by direct determinations with ET-AAS.     

Dissolution kinetics of MgO in aqueous,acidic media

The method of the rotating disc was used to study the kinetics of MgO dissolution. Single crystals of MgO with the orientation {100}, {101}, and {111} were dissolved in N₂-saturated HClO₄-NaClO₄ solutions of constant ionic strength (I=1.0 mol kg^–1). Chemical, mixed and diffusional control of the reaction leading to dissolution has been found between 25 to 90°C and 0.5<pH<3. The dissolution at 90°C andpH3 occurred diffusionally controlled with respect to H⁺ ions. Independent measurements of the limiting current densities for the cathodic reduction of H⁺ ions were carried out in solutions of the same composition and confirmed this kind of control. In the chemical control region the dissolution rates were proportional to the Mg²⁺ ion densities of the single crystal surfaces investigated. The dissolution rates relative to {111}, at 40°C andpH=1, were found to be: 1.0±0.1 (1.0) {111}; 1.3±0.2 (1.2) {101} and 1.7±0.2 (1.7) {100}. Figures in parentheses refer to the relative Mg²⁺ ion densities of the surface. Reproducible results of high quality can only be obtained when fresh dislocations are removed by chemical polishing.In a limitedpH range these results were formally consistent with the complex formation model of metal oxide dissolution. For substances with large surfaces this model applies frequently. However, for single crystals no methods are known which allow the independent determination of the amount of surface OH-groups and the surface complex formation constants. Although the overall dissolution behaviour of MgO, which is relevant for industrial applications, is now rather well known, not enough information for unambiguous mechanistic conclusions is available.Herrn O. Univ.-Prof. Dr.K. Komarek zum 60. Geburtstag gewidmet.     

Evaluation on dispersion behavior of the aqueous copper nano-suspensions

This paper presents a procedure for preparing a nanofluid which is solid-liquid composite material consisting of solid nanoparticles with sizes typically of 1-100 nm suspended in liquid. By means of the procedure, Cu-H(2)O nanofluids with and without dispersant were prepared, whose sediment photographs and particle size distribution were given to illustrate the stability and evenness of suspension with dispersant. Aiming at the dispersion of nano-Cu is regarded as the guide of heat transfer enhancement, the dispersion behavior of Cu nanoparticles in water were studied under different pH values, different dispersant types and concentration by the method of zeta potential, absorbency and sedimentation photographs. The results show that zeta potential has good corresponding relation with absorbency, and the higher absolute value of zeta potential and the absorbency are, the better dispersion and stability in system is. The absolute value of zeta potential and the absorbency are higher at pH 9.5. Hexadecyl trimethyl ammonium bromide (CTAB) [corrected] and sodium dodecylbenzenesulfonate (SDBS) can significantly increase the absolute value of zeta potential of particle surfaces by electrostatic repulsions, and polyoxyethylene (10) nonyl phenyl ether (TX-10) can form a thick hydration layer on the particle surfaces by steric interference, which leads to the enhancement of the stability for Cu suspensions. In the 0.1% copper nano-suspensions, the optimizing concentrations for TX-10, CTAB [corrected] and SDBS are 0.43, 0.05, and 0.07%, respectively, which have the best dispersion results.     

Dissolution of copper oxide by the ethanolamine and ammonium fluoride in aqueous solution

Dissolution properties of copper oxide in aqueous solutions containing ethanolamine and/or ammonium fluoride have been evaluated at various pH ranges. The dissolution rate was strongly affected by the pH of the solution. The solution of ammonium fluoride showed good properties for the dissolution of copper oxide in the range of acidic conditions, whereas the solution containing ethanolamine showed a dissolution property within the basic condition. A mixture solution of ethanolamine and ammonium fluoride displayed enhanced dissolution property of copper oxide at acidic and basic conditions only. An expected synergy effect on the dissolution rate and selectivity could not be produced through a mixture of ethanolamine and ammonium fluoride in an aqueous solution. Copyright © 2011 John Wiley & Sons, Ltd.     

Oxidation of UO2(s) in aqueous solution

In this review the kinetics and mechanism of oxidative dissolution of UO₂(s), mainly under conditions of relevance for the safety assessment of a deep geological repository for spent nuclear fuel, are discussed. Rate constants for the elementary processes involved (oxidation of UO₂ and dissolution of oxidized UO₂) are used to calculate the rates of oxidative UO₂(s) dissolution under various conditions (type of oxidant, oxidant concentration and HCO₃ ⁻/CO₃ ²⁻ concentration) for which experimental data are also available. The calculated rates are compared to the corresponding experimental values under the assumption that the experimental numbers reflect the steady-state conditions of the system. The agreement between the calculated rates and the corresponding experimental ones is very good, in particular for the higher rates. In general, the calculated rates are somewhat higher than the experimental numbers. This can be due partly to the use of initial concentrations rather than steady-state concentrations in the calculations. The kinetic data are also used to quantitatively discuss the dynamics of spent nuclear fuel dissolution under deep geological repository conditions.      

含Pb铝合金表面的电化学溶解趋势

利用一个简单层状模型通过第一性原理的密度泛函理论研究了表面Pb含量变化对Al(100)表面Al原子的化学势和电化学溶解电势的影响规律.计算结果表明,当表面层Pb含量为1/9、1/4、1/2和3/4 ML(monolayer)时,与纯铝相比,表面Al原子的化学势分别升高了0.13、0.17、0.57和0.64 eV,表面Al原子的溶解电极电势分别偏移了-0.04、-0.06、-0.19和-0.21 V.溶解电势向负方向偏移,表明含Pb的Al(100)表面的Al原子在更低的电势条件下就可以溶解了.同时,表面Pb含量不同会引起表面Al原子向内不同程度的弛豫,导致表面Al的化学环境和表面结构发生变化,进一步表明金属表面原子的化学势和溶解电极电势受原子周围的化学环境的影响.表面Mülliken电荷布居分析证实,随着表面Pb含量增加,Pb原子与Al原子之间的电荷交换作用增强,使表面Al原子总的负电荷数增加,导致表面电位下降,表面功函数也减小,也促使Al表面更易于发生电化学腐蚀反应.     

Atomic absorption spectrophotometric determination of trace copper in waters, aluminium foil and tea samples after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

An atomic absorption spectrophotometric method for the determination of trace copper after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been developed. This chelate is adsorbed on the adsorbent in the pH range 1–8. The copper chelate is eluted with 5 ml of 0.1 mol l⁻¹ potassium cyanide and determined by flame atomic absorption spectrometry (FAAS). The selectivity of the proposed procedure was also evaluated. Results show that iron(III), zinc(II), manganese(II) and cobalt(II) at the 50 μg l⁻¹ level and sodium(I), potassium(I), magnesium(II), calcium(II) and aluminium(III) at the 1000 μg l⁻¹ level did not interfere. A high enrichment factor, 200, was obtained. The detection limit (3σ) of copper was 0.34 μg l⁻¹. The precision of the method, evaluated by seven replicate analyses of solutions containing 5 μg of copper was satisfactory and the relative standard deviation was 1.7%. The adsorption of copper onto Ambersorb 572 can formally be described by a Langmuir equation with a maximum adsorption capacity of 14.3 mg g⁻¹ and a binding constant of 0.00444 l mg⁻¹. The accuracy of the method is confirmed by analysing tomatoes leaves (NIST 1573a) and lead base alloy (NBS 53e). The results demonstrated good agreement with the certified values. This procedure was applied to the determination of copper in waters (tap, river and thermal waters), aluminium foil and tea samples.     

Complexation of copper(I) by thiourea in acidic aqueous solution

The interaction of copper(II) and copper(I) with thiourea(Tu) has been investigated by UV and visible spectrophotometry. Over the range of concentrations of copper(I) and Tu(0.1–20)×10^–3 mol-dm^–3 in acid aqueous solutions there are two complexes, CuTu₂ ⁺ (log ₂=11.1) and the other has the ratio Cu/Tu=1/1 with the likely composition Cu₂Tu₂ ²⁺ with log ₂₂=18.5. By the determination of copper(0) solubility in acid thiourea solution and potentiometric measurements it was shown that the potential of the copper electrode is that of a non-equilibrium (corrosive) electrode.     

在铜箔上电辅助制备纳米银及其SERS应用研究

在电化学工作站上以铜箔为工作电极,以硝酸银和PVP混合液作为前驱溶液,利用循环伏安法电辅助制备了纳米银,得到在铜箔上紧密均匀分布的纳米银颗粒聚集体作为SERS基底。通过X射线粉末衍射、X射线光电子能谱、扫描电子显微镜等表征手段,对铜箔上负载的银纳米颗粒进行了形貌和成分的表征,探讨了PVP及电辅助方法对纳米银形貌及基底SERS活性的影响。以4-巯基吡啶和罗丹明6G为探针溶液研究了制备基底的SERS活性,同时还对基底的均匀性进行了研究,结果表明所制备的SERS基底具有良好的性能。     

Potentiometric behaviour of the copper electrode in aqueous copper(II) perchlorate solutions containing sodium chloride

It is demonstrated that the copper metal electrode corrodes in the presence of copper(II) ions in solution. A model based on mass balance can properly describe the experimental results. In the presence of copper(II) ions the copper electrode responds to copper(I), indicating that the electrode potential corresponds to a mixed potential.     

火焰原子吸收法测定粗锡中的铜含量

本文讨论了用火焰原子吸收法测定粗锡中的铜含量的方法。试料用盐酸、硝酸、酒石酸溶解。在5%盐酸介质中,使用空气-乙炔火焰,波长选用324.7 nm,用原子吸收光谱法测量铜的吸光度。以工作曲线法计算铜含量。研究了仪器的最佳测量条件,元素测定的质量数以及酸度的影响等实验。方法测定结果准确、可靠,样品加标回收率在97.20%~102.00%。能满足日常检测应用。     

Fluorescence of lanthanide(III) complexes in aqueous solutions the influence ofpH and solution composition

The fluorescence of lanthanide ions and of their complexes withEDTA,NTA andAA in aqueous solutions was investigated. It has been shown that the fluorescence band intensities of Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III) complexes depend on thepH and the complexing agent concentration. Fluorescence measurements were used to characterise the lanthanide complexes formed and an attempt was made to interpret the results theoretically.

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Untersuchung der Fluoreszenz von Lösungen einiger Lanthaniden(III)-Komplex in Abhängigkeit vonpH und Zusammenhang der Lösung

Zusammenfassung Die Fluoreszenz von wäßrigen Lösungen der Ionen und Komplexe einiger Lanthaniden mit Ethylendiamintetraessigsäure, Nitrilotriessigsäure und Essigsäure wurde untersucht. Der Einfluß vonpH und Konzentration der Komplexbildner auf die Intensität der Fluoreszenzbanden von Sm(III), Eu(III), Gd(III), Tb(III) und Dy(III) wurde bewiesen. Die Fluoreszenzmessungen wurden für die Charakterisierung von Lösungen der Lanthanidenkomplexe genützt und ein Versuch der theoretischen Interpretation der beobachteten Änderungen im Spektrum wurde unternommen.

     

Controlled-potential electrolysis of copper foil and graphite-coated copper foil in a nonaqueous 1 M LiPF6 in a ternary organic carbonate solvent

Controlled-potential electrolysis of battery-grade copper foil and graphite-coated copper foil electrodes in a typical lithium ion battery electrolyte (1 M LiPF₆ in propylene carbonate:ethylene carbonate:dimethyl carbonate [1:1:3 vol.]) was performed in order to construct Tafel plots to obtain values of the exchange current, i₀, and transfer coefficient, α. The transfer coefficients of both electrodes were found to be small (α = 0.25), which was consistent with an assumption of a dominant anodic process in the cell. At room temperature, the graphite-coated copper foil was found to have a higher exchange current than the copper foil. This can be explained by the intercalation of lithium ions into the graphite coating which increases the electron transfer rate. In the range of 0 °C to 50 °C, the exchange currents of both electrodes increased with temperature, but at different rates, while the transfer coefficients were not significantly affected by temperature.     

Corrosion of copper electrode in sodium sulfide solution

The electrochemical reactions of a copper electrode in Na₂S solutions were studied using cyclic voltammetry, potentiostatic and galvanostatic measurements. In addition surface examination and morphological studies were applied using scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX). There are three anodic peaks were found in the anodic branch of the voltammogram’s. These peaks may be corresponding successively to the formation of Cu₂S, CuS and Cu₂O. On the other hand, the cathodic branch contains four peaks. These peaks correspond to the reduction of copper oxide and copper sulfide formed on the anodic branch.     

Inhibitory action of aqueous Ruellia Tuberosa L leaves extract on the corrosion of copper in HCl solution

The inhibitive action of the aqueous extract of Ruellia tuberosa L (ART) on the corrosion of copper in 0.5 ​M HCl was investigated. The inhibition efficiency increased with the extract concentration, acid concentration, as well as increasing the temperature. The Polarization studies revealed that the ART act as a mixed-type inhibitor. Based on the analysis of electrochemical impedance spectroscopy, an equivalent circuit is suggested. The adsorption of the inhibitor ART on the copper surface obeyed the Langmuir adsorption isotherm. From the results of scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy the adsorption of ART on the copper surface is confirmed.     

蒸气发生火焰原子吸收法测定面粉中的铜

用自制的蒸气发生装置,在强还原剂存在下,对铜蒸气的生成进行了详细研究,并通过该装置测定非蒸气发生元素镁和在络合剂掩蔽下测铜两种不同的方法进行了验证。对酸的种类及浓度、NaBH4溶液流速及浓度、反应管道长度的影响等实验参数和干扰情况进行了研究。用该方法测定了面粉中铜的质量分数,检出限为6μg L。     

浊点萃取-火焰原子吸收光谱法测定水样中痕量铜的研究

提出了浊点萃取火焰原子吸收光谱法测定痕量铜的新方法。详细探讨了溶液pH，试剂浓度等实验条件对浊点萃取及测定灵敏度的影响，在最佳下，富集50mL样品溶液，用火焰原子吸收光谱法测定，铜的检测限为0.35μg/L，铜的富集倍率为71倍。方法用于自来水、河水及海水中痕量铜的测定。     

Anodic oxidation of foil copper on fiber-glass plastic in sulfate-chloride electrolyte

The effect of the conditions of galvanostatic anodizing of copper foil at fiber-glass plastic on growth kinetic parameters of Cu₂O films is studied. It is shown that the anodic treatment current density in the sulfate-chloride electrolyte features a logarithmic dependence on the electric field strength in the anodic Cu₂O film, which is probably caused by the presence of either a p-n-transition, or an inversion layer of electronic conductivity at the Cu/Cu₂O interface. It is found that the dependence of the film thickness on the formation time at different current densities is nonlinear.     

Dissolution and regeneration of cellulose in NaOH/thiourea aqueous solution

A novel cellulose solvent, 1.5 M NaOH/0.65 M thiourea aqueous solution, was used to dissolve cotton linters having a molecular weight of 10.1 × 10⁴ to prepare cellulose solution. Regenerated cellulose (RC) films were obtained from the cellulose solution by coagulating with sulfuric acid (H₂SO₄) aqueous solution with a concentration from 2 to 30 wt %. Solubility of cellulose, structure, and mechanical properties of the RC films were examined by infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, ¹³C NMR, and tensile tests. ¹³C NMR analysis indicated that the novel solvent of cellulose is a nonderivative aqueous solution system. The presence of thiourea enhanced significantly the solubility of cellulose in NaOH aqueous solution and reduced the formation of cellulose gel; as a result, thiourea prevented the association between cellulose molecules, leading to the solvation of cellulose. The RC film obtained by coagulating with 5 wt % H₂SO₄ aqueous solution for 5 min exhibited higher mechanical properties than that with other H₂SO₄ concentrations and a homogenous porous structure with a mean pore size of 186 nm for free surface in the wet state. The RC film plasticized with 10% glycerin for 5 min had a tensile strength of 107 MPa and breaking elongation of 10%, and about 1% glycerin in the RC film plays an important role in the enhancement of the mechanical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1521–1529, 2002