Yukio Nagaosa

SOLVENT EXTRACTION OF METAL IONS AND SEPARATION OF NICKEL(II) FROM OTHER METAL IONS BY ORGANOPHOSPHORUS ACIDS

ABSTRACT Such physicochemical properties of bis(2-ethylhexyl)phosphinic acid, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester and bis(2-ethylhexyl)phosphoric acid as the solubilities and the dissociation constants in water, the dimerization constants in organic solvent and distribution constants in organic solvent-water were examined by a potentiometric two-phase titration. The solvent extraction of seven kinds of transition metal ions and magnesium(II) from aqueous sulfate media was studied with the three organophosphorus acids. The pH1/2 values obtained were discussed in terms of the separation efficiency between nickel(II) and the other metal ions. Bis(2-ethylhexyl)phosphinic acid was found to exhibit the best separation efficiency compared with the other two extractants. As a practical application, the purification of unrefined nickel sulfate solution containing the other metal ions as impurities with three extractants was studied by the sequential multistage extraction method with a separatory fu...

Extraction equilibria of some transition metal ions by bis(2-ethylhexyl)phosphinic acid

Measurements of dimerization constants (K(d,HR)) and distribution constants (K(D,HR)) of bis(2-ethylhexyl)phosphinic acid (PIA-8) in three kinds of organic diluents were carried out by a potentiometric two-phase titration technique at 298 +/- 0.1 K. Extraction of iron(III), zinc(II), copper(II), manganese(II), cadmium(II), cobalt(II) and nickel(II) by PIA-8 from 1.0 mol dm(-3) ammonium sulfate solution into heptane was investigated as a function of pH and extractant concentration. The data have been analyzed both graphically and numerically to determine the stoichiometry of extracted species and their extraction constants. The extracted metal species were found to be FeR(3) . 2HR for iron(III), ZnR(2) and ZnR(2) . 3HR for zinc(II), CuR(2) . HR and CuR(2) . 5HR for copper(II), MnR(2) . 2HR and MnR(2) . 3HR for manganese(II), CdR(2) . 3HR for cadmium(II), CoR(2) . HR and CoR(2) . 4HR for cobalt(II) and NiR(2) . 3HR and NiR(2) . 6HR for nickel(II), respectively.

Extraction-polarographic determination of cobalt(II) and nickel(II) as 2,2′-bipyridine complexes in acetonitrile

Abstract The tris(2,2′-bipyridine)cobalt(II) complex gives a reversible d.c. wave with E 1 2 = −1.02 V vs. SCE and a sharp differential pulse peak at Ep = −1.03 V in a salted-out acetonitrile phase. A simple selective method is described for the determination of cobalt(II); down to 0.25 μg of cobalt(II) can be determined in presence of large amounts of Ni, Zn, Cd, Pb, and Cu; iron(III) can be masked with sodium fluoride. The method is applicable to the determination of >0.0l% cobalt in nickel salts and >5 × 10−5% cobalt in iron salts. Nickel(II) can also be extracted from aqueous solution and determined by differential pulse polarography, even in presence of a 20-fold amount of cobalt(II) by masking with EDTA; >0.01% of nickel in cobalt salts can be determined reproducibly.

Solvent extraction of rare-earth metals with bis(2-ethylhexyl)phosphinic acid

Abstract The extraction behavior of tervalent rare-earth metals (Ln) using a heptane solution containing bis(2-ethylhexyl)phosphinic acid (PIA-8, HR) from 0.1 mol/dm3 sodium perchlorate media was studied. The pH0.5 values and separation factors obtained were compared among the metals. The stoichiometry of the extracted species and the extraction constants for the present aqueous/heptane system were determined by slope analysis. It is demonstrated that the rare-earth metals were extracted as monomers LnR3⋅mHR (m=3, 4, 5 or 6), and the extracted species could be stripped into a relatively low concentrated hydrochloric acid. PIA-8 was found to be the most selective extractant for the mutual separation of rare-earth metals among the other phosphinic acids reported.

Determination of trace arsenic(III) by differential-pulse anodic stripping voltammetry with in-situ plated bismuth-film electrode

A sensitive and precise method is presented for the determination of As(III) by differential-pulse anodic stripping voltammery (DPASV). This method is based on the co-deposition of As(III) with Bi(III) onto a basal-plane type of pyrolytic graphite substrate at an accumulation step. DPASV studies indicate that the As was oxidized with anodic scans to give an enhanced anodic peak at about 500 mV vs. Ag/AgCl. Addition of L-cysteine to test solutions was found to be highly effective to obtain reproducible oxidation responses due to As(0) → As(III). A linear relationship between the anodic stripping peak-current ratio (I As/I Bi) and As(III) concentration was observed over the concentration range from 0.0200 µg L−1 to 18.0 µg L−1. The detection limit of As(III) was 0.012 µg L−1 at a deposition time of 180 s. The relative standard deviation was 2.85% (n = 8) at a concentration of 10.0 µg L−1 As(III). Analytical results demonstrate that the determination of As(III) in real water samples is possible by the proposed method.

Recovery and separation of lanthanum(III), aluminum(III), cobalt(II), and nickel(II) from misch metal by solvent extraction using bis(2-ethylhexyl)phosphinic acid

Abstract This paper describes use of bis(2-ethylhexyl) phosphinic acid as a reagent for extraction and mutual separation of lanthanum(III), aluminum(II), cobalt(II), and nickel(II) in 1.0 mol/L sodium nitrate. The extraction and stripping behavior of the four metal ions has been investigated using the extractant in Solvesso #150 as a diluent. The mutual separation and recovery of the metal ions from their mixtures has been tested by multistage extraction with a conventional separator funnel. A set of separation schemes has also been proposed for a continuous countercurrent multistage extraction which is comprised of ten extraction stages, four scrubbing stages, and seven stripping stages. Lanthanum(III) and aluminum(III) are coextracted but separated by selective stripping into different concentrations of hydrochloric acid. Cobalt(II) can be extracted with the nickel(II)-preloaded extractant solution, whereas nickel(II) remains in the aqueous phase. The successful separation of these metal ions from a mis...

Determination of total antimony(III,V) by square-wave anodic stripping voltammetry with in situ plated bismuth-film electrode

A sensitive and reliable method is described for the determination of total Sb(III, V) at traces levels by Osteryoung square-wave anodic stripping voltammery (OSWASV). This method is based on the co-deposition of Sb(III, V) with Bi(III) onto an edge-plane pyrolytic graphite substrate at an accumulation step. OSWASV studies indicated that the co-deposited antimony was oxidised with anodic scans to give an enhanced anodic peak at about 450 mV vs. Ag/AgCl (sat. KCl). The anodic stripping peak current was directly proportional to the total concentration of antimony in the ranges of 0.01–0.10 µg L−1, 0.10–1.0 µg L−1 and 1.0–18.0 µg L−1 with correlation coefficient higher than 0.995 when 2.0 mol L−1 hydrochloric acid was used. The detection limits calculated as S/N = 3 was 5.0 ng L−1 in 2.0 mol L−1 hydrochloric acid at 180 s deposition time. The relative standard deviation was 5% (n = 6) at 0.10 µg L−1 level of antimony. The analytical results demonstrate that the proposed method is applicable to analyses of real water samples.

High-performance liquid chromatography with electrochemical detection for the determination of vanadium(V) in river water and mussel samples

A highly sensitive method has been developed for the determination of vanadium(V) by reversed-phase liquid chromatography with electrochemical detection at −0.60V vs. AgAgCl. The metal complex with N-phenylbenzohydroxamic acid was separated on a C18 (ODS) column; the mobile phase was a 1:1 (vv) mixture of acetonitrile-acetate buffer (0.02 mol l−1, pH 3.5) containing 0.05 mol l−1 potassium nitrate. The elution peak due to the vanadium(V) complex appeared on the chromatogram, and the peak height was proportional to the concentration of the metal ion in the range of 3.0 − 100.0ngml−1. The detection limit for vanadium(V) was 1.0ng ml−1. The method has been applied to the determination of vanadium in two river water samples and one mussel homogenate with precise results.

Cathodic Stripping Voltammetric Determination of Tellurium(IV) with in situ Plated Bismuth-Film Electrode

Abstract A very sensitive and reliable method is proposed for the determination of tellurium(IV) [Te(IV)] by Osteryoung square-wave cathodic stripping voltammetry. This method is based on the reduction of Te(IV) with bismuth(III) onto an edge-plane pyrolytic graphite electrode, followed by a cathodic potential scan. The reduced Te gave a well-defined catalytic hydrogen wave at −1200 mV vs. Ag/AgCl. The peak height of the catalytic wave was directly proportional to the initial Te(IV) concentration in the concentration ranges of 0.01–0.10 and 0.1–1.0 µg L−1 with 30 s deposition time. A 3σ detection limit of 1.0 ng L−1 Te(IV) was obtained with the same deposition time. The relative standard deviation was 3% on replicate runs (n = 5) for the determination of 0.1 µg L−1 Te(IV). Analytical results of natural water samples demonstrate that the proposed method is applicable to the determination of traces of Te(IV).

Dichloromethane as a Solvent for Extraction-Polarographic Determination of Nickel as its Dimethylglyoximate

Abstract Dichloromethane is newly investigated as a solvent for the differential pulse polarographic determination of nickel after solvent extraction with dimethylglyoxime. As little as 20 ng of nickel in sample solution can be selectively determined by the present polarographic method. This method is successfully applied to the determination of nickel in such samples as steel, aluminum and zinc alloy, river sediment with good accuracy and reproducibility.