Solubility of particulate cadmium sulfide at pH=1–14: A radiotracer study

Cadmium sulfide particles were prepared by precipitation from acid solution. A radiotracer technique with¹⁰⁹Cd was applied to measure the solubility of cadmium sulfide at various pH's. Filtration, centrifugation, ultracentrifugation, and dialysis were used to separate the particles from the solution. Only the last two techniques proved to be successful. The solubility of cadmium sulfide in water (pH=7) is found to be: 7.9·10^–5 mol·l^–1 in contrast with the literature value of 9.0·10^–6 mol·l^–1. At low pH (1–4), the solubility agrees fairly well with the solubility calculated on the basis of generally accepted values for the solubility product and for the various complex formation constants, while at high pH (4–14) the solubility is higher than expected.     

The New Fluorescence Enhancement System Eu<Superscript>3+</Superscript>-ARADE-HMTM-Al<Superscript>3+</Superscript> and its Analytical Application

A new bis-Schiff base ligand, N,N-bis-(4-N-aminothiourea-2-amylidene)-4,4-diaminodiphenyl ether (ARADE), was synthesized. Its complex with Eu³⁺ in DMF emits the intrinsic fluorescence of Eu³⁺. The fluorescence intensity of the Eu³⁺-ARADE system was enhanced about 60-fold by the addition of hexamethylene tetramine (HMTM) and potash alum. This is a new fluorescence enhancement phenomenon. The excitation and emission wavelengths are 375nm and 615nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Eu³⁺ in the range of 7.8×10^–9–1.75×10^–5mol·L^–1 with a detection limit of 5.2×10^–9mol·L^–1, or with the concentration of Al³⁺ in the range of 3.1×10^–7–9.7×10^–5mol·L^–1 with a detection limit of 2.7×10^–7mol·L^–1. The interferences of some rare earth metals and other inorganic ions were described. This method was applied to the determination of Eu³⁺ in high purity yttrium oxide and the analysis of Al³⁺ in alloy steel standard samples. The mechanism of fluorescence enhancement was also studied.     

Spectrofluorimetric Assay of Cationic Surfactants by Fluorescence Quenching of 9-Anthracenecarboxylic Acid

A new simple, selective and sensitive fluorescence quenching method was developed to determine cationic surfactants with the 9-anthracenecarboxylic acid (ACA). The fluorescence intensity of ACA was decreased by addition of trace amounts of cationic surfactants. Under optimum conditions, the ratio of fluorescence intensity in the absence and presence of cationic surfactants was proportional to the concentration of cationic surfactants over the range of 0.3–4.5 × 10⁻⁵ mol L⁻¹ for cetylpyridinium chloride (CPC) and 0.4–6.0 × 10⁻⁵ mol L⁻¹ for cetyl trimethyl-ammonium bromide (CTAB). The detection limits are 1.0 × 10⁻⁶ mol L⁻¹ for CPC and 1.2 × 10⁻⁶ mol L⁻¹ for CTAB, respectively. Based on this approach, this paper presents a new quantitative method for cationic surfactants assay.     

Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm^–3 (TOA); HF concentration in the feed solution, 0.01 mol·dm^–3 and concentration of NaOH used as stripping agent 2.5 mol·dm^–3. The maximum flux and permeability determined under optimum conditions are 3.06·10^–5 mol·m^–2·s^–1 and 8.44·10^–11 mol· ·m²·s^–1 at 25±2°C and 4.21·10^–5 mol·m^–2·s^–1 and 11.55·10^–11 mol·m²·s^–1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10^–11 mol·m²·s^–1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.     

Determination of thorium by adsorptive type chemically modified electrode with a polycomplex system

A preconcentration and determination method for thorium in aqueous solution with a tri-n-octylphosphine oxide modified glassy carbon electrode is proposed. In the presence of 2-thenoyltrifluoroacetone, thorium in NaAc-HAc supporting electrolyte is preconcentrated on a modified rotating disk electrode, and a highly sensitive reduction peak is obtained by cathodic stripping voltammetry at –1.10 V versus Ag/AgCl. A linear response of reduction peak height and concentration is observed for 1.15×10^–9–1.44×10^–8 mol·1^–1 of thorium and the detection limit is 1.0×10^–9mol·1^–1. It is very selective and sensitive, with a standard deviation of 3.4% and a recovery of 90–110%.     

Kinetics and kinetic isotope effect in pentavalent plutonium disproportionation activated by power ultrasound

A kinetic isotope effect in Pu(V) disproportionation has been observed in nitric acid solution under the effect of power ultrasound with intensity 0.9W·cm^–2 and frequency 22 kHz. The isotope separation coefficient for²⁴²Pu/²³⁹Pu isotopes was found to be 1.0081 at 20°C. Without sonication the k.i.e. was not observed. The rate constant of Pu(V) disproportionation was found to be accelerated under sonication. The rate constant determined was (5.7±0.6)·10^–3 1²·mol^–2·s^–1 atl=0.9 W·cm^–2,v=22 kHz, [HNO₃]=0.5 mol·l^–1 andT=20°C. It is supposed that the acceleration of Pu(V) disproportionation and the kinetic isotope effect are due to the activation of plutonoyl groups in the interface between the cavitation bubble and the bulk solvent.     

Nitric acid transport across TBP—Kerosene oil supported liquid membranes

HNO₃ transport across tri-n-butyl phosphate kerosene oil supported liquid membrane with or without uranyl ion transport has been studied. Parameters studied are the effect of TBP in the membrane, nitric acid in the feed solution and nitrate ion concentration in the feed solution. The flux of protons for 1 to 10 mol·dm^–3 HNO₃ solution is in the range of (0–25)·10^–4 mol·m^–2·s^–1 and for the TBP concentration range of 0.359 to 3.59 mol·dm^–3, the flux determined is (8.9 to 22)·10^–4 mol·m^–2·s^–1. From the experimental data and using theoretical equations the complex under transport through the membrane appears to be 2TBP·HNO₃ both in the presence and absence of uranyl ions. The diffusion coefficient for H⁺ ions through the membrane as a function of TBP concentration varies from (53 to 6)·10^–12 m²·s^–1, based on experimental flux and permeability data. The values of this coefficient supposing 2TBP·HNO₃ as diffusing species, based on viscosity data and theoretical estimation varies from (82.50 to 3.30)·10^–12 m²·s^–1. The value of distribution coefficient varies in the reverse direction from 0.06 to 1.46 at the same TBP concentration.     

Transport of titanium(IV) ions across di-2-ethylhexylphosphoric acid-CCl4 supported liquid membranes

Transport study for Ti(IV) ions using di-2-ethylhexylphosphoric acid (D2EHPA) (carrier)-CCl₄ (diluent) liquid supported membrane in microporous polypropylene hydrophobic film has been performed. The parameters studied are effects of carrier, H₂SO₄, stripping agent (NH₄F) concentrations and temperature variation on flux and permeability coefficients of the metal ion. The optimum concentrations of transport found are 2.04 mol·dm^–3 D2EHPA, 1.0 mol·dm^–3 H₂SO₄ in the feed and 1 mol·dm^–3 NH₄F as stripping agent. The maximum flux and permeability coefficient determined are 1.32·10^–5 mol·m^–2·s^–1 and 8.02·10^–12 mol·m^–2·s^–1, respectively. The transport of this metal ion is increased with increase in temperature. The mechanism of transport appears to be based on coupled counter ion transport phenomenon.     

Photometry in a continuous flow system

Summary Sulphate in various environmental samples was determined by measuring the optical absorbance upon reaction with the barium(II) dimethylsulphonazo(III) complex. The measurement took place in a flow-through system. Interferences from phosphate, metal ions and others were eliminated. The results of a turbidimetric measurement, a spectrophotometric measurement with thorin, an automatic titration and the proposed method are compared. The latter allows the determination of sulphate in the range of 1.4–60 mol·l^–1. The standard deviation is 0.3–0.6 mol·l^–1, depending on the type of sample (water) analysed. A determination takes 1.5min.

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Photometric in einem DurchflußsystemBestimmung von Sulphat mit Dimethylsulfonazo(III) in Umweltmaterial mit Hilfe eines Durchflußsystems

Zusammenfassung Sulfat wurde in verschiedenen Umweltproben durch Messung der Extinktion nach Reaktion mit dem Barium(II)-dimethylsulfonazo(III)-komplex im Durchflußsystem bestimmt. Störungen von Phosphat, Metallionen, u.a. wurden beseitigt. Die Ergebnisse einer turbidimetrischen, einer photometrischen, einer automatischen Titration und der vorgeschlagenen Methode werden verglichen. Die Methode ermöglicht die Sulfatbestimmung im Bereich von 1,4–60 mol·l^–1. Die Standardabweichung beträgt 0,3–0,6 mol· l^–1 je nach Typ des Probematerials (Wasser). Eine Bestimmung erfordert 1,5min.

     

Kinetik der Entstehung des Zinktartrats

Zusammenfassung Aus potentiometrischen Daten wurde die Konstante der Entstehungsgeschwindigkeit des Zinktartrates bei 18° berechnet. Ihr durchschnittlicher Wert beträgt 1,3·10² mol·min^–1 und der Wert der Zerfallsgeschwindigkeitskonstante beläuft sich im Durchschnitt auf 7,5·10^–2 mol·min^–1.     

Extraction of Pd(II) ions using tri-n-octylamine xylene base supported liquid membranes

Membranes, based on tri-n-octylamine (TOA) xylene liquid, supported in hydrophobic microporous films have been used to study the transport of Pd(II) ions, after extraction into the membrane. Various parameters, such as the effect of hydrochloric acid concentration in the feed solution, TOA concentration in the membrane phase, effect of stripping agent like nitric acid concentration, and temperature on the flux of Pd(II) ions across the liquid membranes have been investigated. The optimum conditions of transport for these metal ions determined are, TOA concentration, 1.25 mol·dm^–3, HCl concentration in the feed solution, 5 mol·dm^–3, and concentration of nitric acid used as a stripping, agent 5 mol·dm^–3. The maximum values of the flux and permeability determined under the optimum condition are 23·10^–6 mol·m^–2·s^–1 and 2.40·10³ m²·s^–1 at 25°C. The results obtained have been used to elucidate the mechanism of palladium transport.     

The aggregation ofn-dodecanephosphonic acid in water

Several techniques were employed to study the aggregation ofn-Dodecanephosphonic Acid (DPA) in water. At 22°C, the solubillity of DPA increases, probably due to the formation of small premicellar aggregates. The CMC is (5.4±2.4) ×10^–4 mol·dm^–3 and the solubility reaches the CMC value at 26°C. At 30°C and at a concentration of about 9×10^–3 mol·dm^–3, a lamellar mesophase appears. Both micelles and liquid crystal lamellae are almost uncharged. Their polar heads have strong hydrogen bonds between them. The ionization of DPA molecules in micelles and mesophase structures is strongly reduced in comparison with monomerically dissolved molecules.     

Adsorptive Voltammetric Study of Thorium–Alizarin Complexon Complex at a Carbon Paste Electrode

A new sensitive adsorptive voltammetric procedure is described for trace measurement of thorium. It is based on the cathodic stripping peak of the thorium–alizarin complexon (ALC) complex at a carbon paste electrode (CPE). The complex of Th(IV) with alizarin is adsorbed at a CPE in a mixed buffer solution (pH 5.0) which consists of 0.1mol·L^–1 sodium acetate and 0.04mol·L^–1 potassium biphthalate, yielding a sensitive cathodic voltammetric peak corresponding to the reduction of alizarin in the complex at –0.57V (vs. SCE). The second-order derivative peak current of the complex is linearly dependent upon the concentration of Th(IV) over the range of 3.0×10^–9 8.0×10^–7mol·L^–1. The detection limit is 1.0×10^–9mol·L^–1 for 180s accumulation. The molar ratio of each component in the complex was estimated as n_Th(IV):n_ALC=1:1 by a continuous variation method. The electrode processes of the Th(IV)–alizarin complex at a CPE were investigated. The procedure was successfully applied to the trace determination of thorium in ore and clay samples.     

Sodium hexadecanoate micellar aggregation number

The diffusion coefficient of sodium hexadecanoate micelles was studied by polarography at 63°C, and the size and aggregation number of the micelles was computed. At concentrations above 0.01 mol·L^–1 rodlike micelles exist, which become flexible at 0.040 mol·L^–1 and entangle at 0.043 mol·L^–1     

Determination of total chlorine in waste oil

Summary A simple method has been developed to determine the concentration of organic chlorine in waste oil. The determination is based on the conversion of organic chlorine to inorganic chloride by reaction with sodium biphenyl followed by extraction with nitric acid and a mixture of nitric acid and water. The concentration of chloride is determined by direct potentiometry with an ion-selective electrode. The limit of determination amounts to 3·10^–5 mol·l^–1 chloride ions with a standard deviation of 3.5%. Different samples of waste oil have been analyzed and the results have been compared to those obtained by combustion in a H₂/O₂ flame followed by potentiometric titration with silver nitrate.     

p-Dimethylaminobenzaldehyde thiosemicarbazone: a simple novel selective and sensitive fluorescent sensor for mercury(II) in aqueous solution

A novel and simple fluorophore, p-dimethylaminobenzaldehyde thiosemicarbazone (DMABTS), was prepared in order to find available fluorescent chemosensor for mercuric ion in aquesous solution. DMABTS emitted fluorescence at 448 nm in aqueous solution and its fluorescence intensity was completely quenched upon interaction with Hg²⁺ ions, which should be attributed to the 1:1 complex formation between DMABTS and Hg²⁺. The binding constant of the complex was determined as 7.48 × 10⁶ mol l⁻¹. The linear range of quantitative detection of 0 to 5.77 × 10⁻⁶ mol l⁻¹ and the detection limit of 7.7 × 10⁻⁷ mol l⁻¹ for Hg²⁺ in the 6.3 × 10⁻⁶ mol l⁻¹ DMABTS aqueous solution were obtained from a calibration curve. The coexistence of several transition metal ions and anions did interfere the fluorometric titration of Hg²⁺ ion by less than 4% in the emission change.     

Atomic absorption spectroscopic determination of molybdenum in aqueous tetrathiomolybdate solutions

The flame atomic absorption spectroscopic determination of molybdenum, in aqueous solutions of tetrathiomolybdate (MoS ₄ ^2– , TTM) and paramolybdate species (Mo₇O ₂₄ ^2– , PM) has been investigated. A serious signal decrease occurred, if molybdenum has been present as tetrathiomolybdate species, and the sensitivity loss has been 85%. To improve the sensitivity, the solutions of TTM have been digested by wet-acid treatment, and made 0.14 mol·l^–1 ammonia. Finally, Mo has been determined by AAS using a nitrous oxide-acetylene flame. The range of the calibration was 0–100 mg·l^–1 and the relative standard deviation of the slope was less than 1%.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Separation of cerium and europium by extraction with tributyl phosphate and di(2-ethylhexyl)phosphoric acid in n-alkane from nitrate solutions

The following extraction systems have been studied: (Ce³⁺+Eu³⁺) (NO₃)-(EDTA, DCTA, DTPA)/TBP in n-alkane and (Ce³⁺+Eu³⁺)(NO₃)/DEHPA in n-alkane at concentration ratios as follows: [Ce³⁺]=trace –1 mol·dm^–3, [Eu³⁺]=trace –0.1 mol·dm^–3. [TBP]=(0.183–1.83) mol·dm^–3, [DEHPA]=(5·10^–3–0.1) mol·dm^–3, [(H, Na)NO₃]=(0.1–6) mol·dm^–3, [Eu³⁺]: [EDTA, DCTA, DTPA]=11–110. The initial concentration of Eu³⁺ in aqueous phase in the extraction system containing a mixture of Ce³⁺ and Eu³⁺ was trace, 1% and 10% compared with the Ce³⁺ concentration. The distribution of the elements between the phases was observed radiometrically using¹⁴¹Ce,¹⁵²Eu and¹⁵⁴Eu. The results are documented by the distribution ratios D_Ce, D_Eu and separation factor =D_Eu/D_Ce as functions of variable parameters of the systems.     

Electron irradiation studies on ammonium molybdophosphate

Ammonium molybdophosphate (AMP) was irradiated with electrons up to a dose of 1 MGy. X-ray diffraction patterns and FT-IR of irradiated and control AMP samples were recorded. Uptake of¹³⁷Cs from nitric acid in the range of 0.2 to 10 mol·dm^–3 was estimated by a batch equilibration technique. AMP undergoes perceptible changes in its physico-chemical characteristics on irradiation with electrons. Uptake of¹³⁷Cs from nitric acid by irradiated AMP was nearly the same as the control AMP in the nitric acid concentration range of 6 to 10 mol·dm^–3 and relatively higher in the range of 0.2 to 6 mol·dm^–3. The results are discussed in terms of available information on the physicochemical properties of 12-heteropoly acids and their salts.     

Analysis of tryptophan at nmoll(-1) level based on the fluorescence enhancement of terbium-gadolinium-tryptophan-sodium dodecyl benzene sulfonate system

It is found that Tb³⁺ can react with tryptophan (Trp) and sodium dodecyl benzene sulfonate (SDBS), and emits the intrinsic fluoresence of Tb³⁺. The fluorescence intensity can be enhanced by La³⁺, Gd³⁺, Lu³⁺, Sc³⁺ and Y³⁺, among which Gd³⁺ has the greatest enhancement. This is a new co-luminescence system. The studies indicate that in the Tb-Gd-Trp-SDBS system, there is both Tb-Trp-SDBS and Gd-Trp-SDBS complexes, and they aggregate together and form a large congeries. The fluorescence enhancement of the Tb-Gd-Trp-SDBS system is considered to originate from intramolecular and intermolecular energy transfers, and the energy-insulating sheath effect of Gd-Trp-SDBS complex.Under the optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of Trp in the range from 4×10⁻⁸ to 4×10⁻⁵ mol l⁻¹. The detection limit is 10⁻⁹ mol l⁻¹. The proposed method is one of the most sensitive fluoremetries of Trp.