Concentration Of Complexing Agent Research Articles

Electro-deposition of Fe–Tb–O films with ac currents for use in high frequency micromagnetic devices

Electro-deposition of Fe–Tb–O films was attempted using ac currents with low frequency. The film composition, especially Tb content of films, was found to be sensitive to the concentration of complex agent, KNaC 4H 4O 6: when KNaC 4H 4O 6=283.47 mM, plated films with very high Tb content reaching 29 at.% were obtained, in spite of the difficulty in electro-deposition of Tb owing to its very low catalytic activity. Coercivity H c and squareness ratio M r/ M S of films varied considerably depending strongly on the intensity of ac current i: when i=0.67 A/dm 2, films with relatively soft magnetic properties of H c=29O e and M r/ M S=0.93 were realized.

Water purification by sulfide-containing activated carbon

We investigated a new kind of activated carbon named gaiasafe-Formstoff as an agent for powerful heavy metal reduction. This activated carbon contains highly dispersed sulfide compounds. Our investigations with lead containing wastewaters showed an outstanding metal sulfide precipitation power of the new agent. The lead reduction rates are independent of wastewater parameters like lead concentration and complexing agent concentration. Contacted as powder or as a fixed bed with wastewater gaiasafe-Formstoff showed the best cleaning capacity in comparison to all other agents tested. Investigations with gaiasafe-Formstoff about its ability to reduce the contents of further heavy metals in wastewater are under way. The gaiasafe-Formstoff reaction products with wastewater represent an energy-rich and raw material-rich resource when fed to metallurgical processes.

Sorption characteristics of radionuclides on synthetic birnessite-type layered manganese oxides

The removal of trace caesium (137Cs), trace strontium (89Sr, 90Sr/90Y) and trace cobalt (57Co) from aqueous solution by synthetic sodium and potassium birnessites has been studied by a batch technique. Distribution coefficients were determined as a function of pH in four solutions: water, 0.005 M sodium tetraborate, 0.005 M sodium citrate and 0.0001 M EDTA. Other effects studied were increasing sodium ion, potassium ion and complexing agent concentration. Key synthesis parameters (ageing time, MnO4−/Mn2+ ratio) were tuned in order to maximise trace cobalt sorption efficiencies. The optimised material was tested for the removal of caesium, strontium and cobalt from a nuclear power plant floor drain simulant. A sodium birnessite sample was also screened for the removal of 63Ni, 54Mn, 59Fe, 65Zn and 236Pu radionuclides.

Soft-solution process of Fe–Tb–O films for use in high frequency micromagnetic devices

An attempt for fabricating Fe–Tb–O films with heterogranular structures was made using a soft-solution process with an alternative current for deposition. The resultant film composition was found to be sensitive to the concentration of complex agent, KNaC4H4O6, the intensity i, and the frequency f of deposition current. These dependencies are well explained from the model for film formation. When KNaC4H4O6=283.47 mM, i=6.7 mA/cm2, and f=6 mHz, the film with very high Tb content exceeding 29 at. % were obtained, which exhibited a relatively soft magnetic magnetization of Hc=29 Oe and Mr/Ms=0.93.

無電解ＮｉＢめっきにおける複合錯化剤の影響

Based on the results of previous single complexing agents, we prepared mixed complexing agents for electroless NiB plating based on sodium citrate, and studied their characteristics. Complexing agents were mixed as follows: sodium citrate-sodium malonate, sodium citrate-glycine, sodium citrate-diethylenetriamine. The deposition rate from the mixed complexing agent bath was influenced by pH and complexing agent concentration, and mainly corresponded to mixed behavior except for sodium citrate-diethylenetriamine. The boron content of deposited films gradually increased with increasing sodium citrate concentration for the mixed complexing agent. The carbon content was highest as 0.72wt% at a ratio of 1:1 for sodium citrate-diethylenetriamine. The microstructure and crystallization by heat-treatment of NiB films mainly depended on boron content for the mixed system. Codeposited carbon in NiB films may also affect the microstructure and crystallization behavior.

Quantitative determination of inorganic minor cations in sodium-, calcium-, magnesium-matrix simulated samples by capillary electrophoresis

The analysis of ammonium, alkali and alkaline-earth trace cations (0.5 ppm) in samples with a calcium, sodium or magnesium matrix (500 ppm) has been achieved using 10 m M imidazole (pH 4.5) electrolyte to which a complexing agent (15-crown-5, oxalic acid or dipicolinic acid) has been specifically added in order to decrease the electrophoretic mobility of the matrix cation and thus to allow the separation of higher mobility cations at sub-ppm concentrations. The influence of several experimental parameters (complexing agent concentration, buffer pH and temperature) have been studied in order to optimize the separation. The complexing agent concentration appears to be the main parameter governing the selectivity of the cations during the analysis of matrix samples. In optimized conditions, we have checked that the separation between minor inorganic cations is not significantly altered by an increase in the matrix cation concentration. As the concentration of the matrix cation increases, the migration times of minor cations remain unchanged even for a 1000 ppm concentration of the matrix cation. Finally, these optimized buffers allow the quantitation of minor cations down to 0.05% (w/w) for calcium- or magnesium- matrix simulated samples and 0.2% (w/w) for sodium-matrix simulated samples.

Application of Maximum Entropy Formalism in the Determination of the Affinity Spectrum in Macromolecular Complexation

Binding of small molecules to heterogeneous ligands and/ or adsorption on heterogeneous surfaces with a multiplicity of specific binding sites is of great importance in many fields, ranging from the analysis of interactions between receptors and ligands in biochemistry to environmental sciences. This paper presents the application of the Maximum Entropy (MaxEnt) formalism to the calculation of the Langmuirian affinity distribution function or affinity spectrum, describing the interactions between small molecules and a surface or a macromolecule. Discrete, continuous, and mixed affinity distribution functions are successfully reproduced using a very reduced number of simulated data of coverage versus free complexing agent concentration and without any a priori assumption on the number of kinds of sites. MaxEnt is also applied to experimental data previously reported in the literature. Finally, the advantages and drawbacks of applying MaxEnt formalism to the spectral analysis of coverage data are discussed.

Effect of Complexing Agents (EDTA and ATMP) on the Remobilization of Heavy Metals from a Polluted River Sediment

EDTA and ATMP are synthetic chelatingagents used in many industrial applications. Becauseof their low biodegradability, they are present inmany aquatic systems where their strong complexingcapacities can modify the transfer of toxic heavymetals between solid and liquid phases. The remobilization of Cu, Pb and Cd from pollutedsuperficial river sediments in the presence of twosynthetic organic ligands (a polycarboxylate, EDTA,and a phosphonate, ATMP) is investigated as a functionof reaction time to determine the time necessary toreach dissolutive equilibrium, and as a fonction ofthe complexing agent concentration. The dissolutive equilibrium times are similar (10 to20 hours) and the solubilizing power of ATMP isslightly lower than that of EDTA. The curves ofsolubilization of metals in the presence of thecomplexing agents present a shape of a “chelateconcentration” desorption edge, for a chelate rangebetween 10-5 to 10-3 mol L-1, thesolubilised metals increasing dramatically. Thisremobilization is the result of a competition betweenassociation with the solid phase and dissolvedcomplexation. With EDTA, the desorption order ofmetals seems to be imposed by association with thesolid. For ATMP is it the chelate complexing strengthwhich determines this order.

Separation of transition metal cations by capillary electrophoresis optimization of complexing agent concentrations (lactic acid and 18-crown-6)

The simultaneous separation of alkali, alkaline earth and transition metal cations by capillary electrophoresis was achieved using an electrolyte containing imidazole as indirect UV co-ion and lactic acid and 18-crown-6 as complexing agents with indirect UV detection. The addition of lactic acid to the imidazole electrolyte allows the separation of transition metal cations, whereas 18-crown-6 allows one to resolve ammonium and potassium and also sodium and lead. An electrolyte containing 10 m M imidazole, 5 m M lactic acid and 0.5 m M 18-crown-6 at pH 4.5 and with the separation temperature fixed at 30°C allow the simultaneous separation of alkali, alkaline earth and transition metal cations by capillary electrophoresis. By increasing the hydrodynamic injection time to 15 s, a linear relationship between corrected peak area and cation concentration in the 0.1–1 ppm range was obtained for transition metal cations. Further, the separation of inorganic cations at a low concentration level (100 ng ml −1) was achieved without any loss of resolution.

Production of rare-earth oxides of high purity

A novel industrial technology for producing rare earth oxides of high purity (>99.99%) by temperature pressurized ion-exchange displacement chromatography is reported. It was concluded from the technological parameters that the concentration of complex agent in the eluent can be several times higher than that used in the classical ion-exchange method if a certain amount of buffer is present; the height equivalent to a theoretical plate (HETP) decreases linearly with increase in the operating temperature, increases slightly with increase in the flow-rate of the eluent and depends on the particle size of the ion exchanger. Rare earth oxides of high purity were manufactured on an industrial scale using a solution of special composition as eluent, and enriched rare earth mixtures or single rare earth oxides with low grade as raw and processed material on a temperature pressurized ion-exchange multi-column operating system containing polytetrafluoroethylene as the inner liner.

An ecoregion approach to mercury bioaccumulation by fish in reservoirs

Three Oregon reservoirs were evaluated for environmental parameters affecting mercury (Hg) dynamics and bioaccumulation in fish using an ecoregion approach. Ecoregions are distinguished by topography, geology, soil type and composition, and land use patterns. We examined: pH, dissolved oxygen, hardness, conductivity and concentration of Hg ([Hg]) in water; and complexing agent concentrations, organic content, inorganic and organic [Hg] in sediments; and [Hg] in three fish species. [Hg] in water was below detection (0.1 μg/L) in most water samples from the three reservoirs; in samples above detection, we reasoned that Hg was predominantly in the particulate fraction. Hg in sediment was only found consistently in the inorganic state; organic mercury was below detection (0.2 ng/g) in 83% of sediment samples. Muscle [Hg] in fish over 4 years old was above the FDA limit of 1.0 μg/g wet weight, and more than 90% of the Hg in all fish was organic mercury. [Hg] in lateral muscle was similar between smallmouth bass (Micropterus dolomieu) in Owyhee Reservoir and largemouth bass (Micropterus salmoides) in Cottage Grove Reservoir; rainbow trout (Salmo gairdneri) from Ochoco Reservoir had significantly lower levels of Hg. It is concluded that, although ecoregion parameters alone do not explain mercury dynamics, they may influence the methylation rate in areas of similar Hg loading rates.

Effect of complexing agent (citric acid) and pH on the cathodic deposition of As-Sb alloys

As-Sb alloys have been cathodically deposited onto nickel electrodes from acidic aqueous solutions containing citric acid. The effect of complexing agent concentration, pH, angular speed of the RDE and temperature on deposition rate and alloy composition have been monitored. Increasing citric acid concentration and pH decrease the deposition current and the antimony content of the alloys (measured by EDX analyses). The opposite effect is observed when rotation speed or temperature are increased. Under most combinations of citric acid concentration and pH, the steady-state i/E curves show the current peak already observed in a previous investigation. The morphology and structure of the alloys have been studied with scanning electron microscopy and X-ray diffraction. Alloys containing ⩾ 74% Sb were found to be crystalline (hexagonal system).

Terpolymerization of maleic anhydride, styrene and electron‐acceptor monomers

AbstractThe free‐radical terpolymerization of maleic anhydride, styrene, and acrylic monomers such as acrylonitrile, methyl acrylate and methyl methacrylate was studied. The alternating copolymerization of maleic anhydride with styrene was found to be favored in those systems. Contrary to theoretical predictions, maleic anhydride is more reactive than styrene in ternary systems. The relative reactivity of the acrylic monomers studied was found to decrease in the order: methyl methacrylate ≥ methyl acrylate > acrylonitrile. In the presence of a Lewis acid, such as ZnCl2 or C2H5AlCl2, the relative reactivity of acrylic monomers increases and at the respective complexing agent concentration the copropagation of the acrylic monomer with styrene can dominate. On the basis of the results obtained, some aspects of the mechanism of alternating propagation in systems comprising an electron‐donor monomer and two electron‐acceptor monomers are discussed.

Continuous free focusing electrophoresis of metal ions in stepwise pH gradient system

Theoretical considerations indicate the possibility of focusing electrophoresis of metal ions in a stepwise pH gradient system with constant complexing agent concentration. An experimentally stepwise pH gradient was established. Several separation examples of transition metals were accomplished on an apparatus for continuous free electrophoresis. The separation and focusing effects predicted by theoretical considerations have been experimentally confirmed.

Continuous free focusing electrophoresis of metal ions in a stepwise gradient system of complexing agent

Theoretical considerations indicated the possibility of the focusing electrophoretic separation of metal ions using a stepwise gradient of complexing agent concentration. Separations of cations in several prepared samples were performed in an apparatus for continuous free electrophoresis. The separation performance and focusing effect of this system predicted theoretically were confirmed. Each component seeks its own concentration step in the completing agent.

Extraction of Copper by Liquid Membranes

Abstract Important variables governing the permeation of copper ion through liquid membranes and their effects on the separation process are described. These variables are membrane viscosity, treatment ratio (volume ratio of emulsion to feed in mixer), complexing agent concentration, internal droplet size, internal phase leakage, and copper concentration in the internal phase. The information is needed for scaling-up of equipment and further process development. The economic evaluation based on bench-scale pilot plant runs shows this process is 40% cheaper than solvent extraction.

Unified treatment of the potentiostatic reduction on an expanding mercury electrode of complexes at any concentration ratio of reacting species

The article describes a general treatment of voltammetry of equilibrium complexation reactions at an electrode expanding in accord with any power law, the stationary electrode and the dropping mercury electrode being special cases. Reversible, irreversible and quasireversible electrode reactions are embraced by the treatment. A general expression for the current—voltage characteristic was derived, which was applied to the case of the polarographic reduction of complex ion, where either the simple or complex ion is electrochemically active. An equation accounting for the surface concentration of all reacting species is derived, the solution of which under appropriate conditions gives the equations of Lingane, Matsuda and Ayabe, etc. Correlations of potential, current and wave shape with complexing agent concentration are presented and discussed. A criterion for the splitting of the polarographic wave in the absence of excess of the complexing agent is proposed. Experimental results of several papers are discussed in the light of these criteria and a satisfactory agreement between the results and the predictions is established.

Unified treatment of the potentiostatic reduction on an expanding mercury electrode of complexes at any concentration ratio of reacting species

The article describes a general treatment of voltammetry of equilibrium complexation reactions at an electrode expanding in accord with any power law, the stationary electrode and the dropping mercury electrode being special cases. Reversible, irreversible and quasireversible electrode reactions are embraced by the treatment. A general expression for the current—voltage characteristic was derived, which was applied to the case of the polarographic reduction of complex ion, where either the simple or complex ion is electrochemically active. An equation accounting for the surface concentration of all reacting species is derived, the solution of which under appropriate conditions gives the equations of Lingane, Matsuda and Ayabe, etc. Correlations of potential, current and wave shape with complexing agent concentration are presented and discussed. A criterion for the splitting of the polarographic wave in the absence of excess of the complexing agent is proposed. Experimental results of several papers are discussed in the light of these criteria and a satisfactory agreement between the results and the predictions is established.

The Influence of the Complexing Agent Concentration on the Etch Rate of Germanium

This paper reports the effect of the concentration of the complexing agent in an etching solution on the etch rate and surface morphology. The {100} surface of germanium was etched in a solution of the basic composition in the volume ratio 1:1:4, where was tartaric, acetic, citric, oxalic, and acids, and mannitol. There was no change in the shape or orientation of the etch figures with variation of the type or orientation of the complexants. It was found that the etch rate was a function of the concentration of the complexant when the concentration of the oxidizing agent was held constant. The variation in etch rates and activation energies with the complexing agent concentration indicated that the reactions are diffusion controlled. A model is proposed for the crystal‐solution interface which is consistent with the interdependence of the etch rates and the complexing ratio of the germanium.

Silver complexes with I −, Br − and SCN − in sulfolane

The solubility product constants of silver bromide(I), iodide(II), and thiocyanate(III) and the over-all formation constants β of Ag nX m (m−n)− (X = Br, I, SCN) complexes in sulfolane at 30°, have been calculated from potentiometric titrations. At ionic strength μ = 0.1 the stoichiometric solubility product constants were: 6.6 × 10 −19 (I), 3.3 × 10 −19 (II), 5.4 × 10 −17 (III). In the range of complexing agent concentrations explored, only one complex has been found for Br − (AgBr 2 −, β = 2.1 × 10 19, only one complex for I − (Ag 3I( 4 −, β = 3.3 × 10 56) and only one complex for SCN − (Ag(SCN) 2 −, β = 1.1 × 10 16). The above formulas of the complex ions have been also confirmed by conductometric titrations.