Masaru Kimura

Trace enrichment with activated carbon and determination of trace metals in high-purity zinc and zinc(II) nitrate.

A method is described for the enrichment and determination of trace metals such as Ag, Bi, Cu, Co, Cd, In, Pb, Ni, Tl, Fe and Hg, present as impurities in high-purity zinc and zinc(II) nitrate. When the sample solution, after addition of potassium ethyl xanthate, is filtered through a small filter paper coated with 50 mg of activated carbon, the trace elements are quantitatively adsorbed on the carbon. The trace elements (with the exception of Hg) are dissolved off with nitric acid and determined by atomic-absorption or emission spectrometry. Mercury is evaporated at 650 degrees and determined by flameless atomic-absorption. In 10 g of Zn oe 50 g of Zn(NO(3))(2).6H(2)O the limit of detection is 0.1-60 ppM and the coefficient of variation was 2.7-20%.

Preconcentration of traces of silver and bismuth from cobalt and nickel and their nitrates, with activated carbon

A method is described for the preconcentration of trace metals Ag and Bi, present as impurities in high-purity cobalt and nickel metals and their nitrates. After the metal samples have been dissolved in nitric acid (or the salts in water) the trace elements are complexed with ammonium pyrrolidinedithiocarbamate (APDC). The sample solution is then filtered through a 2-cm filter paper coated with 50 mg of activated carbon, whereby the complexed trace metals are adsorbed on the activated carbon and separated from the matrix. The trace elements are dissolved off with nitric acid and determined by flame atomic-absorption spectrometry (AAS). The detection limits for the analysis of 10 g of metal samples and 50 g of the nitrate samples were 0.002-0.035 ppm Ag and 0.04 ppm Bi for the metal samples, and 0.0003-0.0004 ppm Ag and 0.004-0.005 ppm Bi for the nitrate samples. The coefficient of variation, in general, is 10-25% for Ag and 33% for Bi.

Separation and Preconcentration of Trace Amounts of Several Metals in Magnesium Metal and Nitrate with Activated Carbon as a Collector

A method is described for the preconcentration and determination of traces of Hg, Ag, Cu, Fe, In, Mn, Pb, and Zn present as impurities in magnesium metal (1 g) and nitrate (100 g). After the metal sample has been dissolved in nitric acid (or the salt in water) and the pH adjusted to 8.1-9 (except for preconcentration of Hg, when pH 3 is used), the solution is filtered through a 2-cm paper coated with 50 mg of activated carbon. The trace metals are quantitatively adsorbed on the activated carbon and separated from the matrix. The rest of the procedure has already been described. The detection limits for the analysis of 1 g of Mg and 100 g of Mg(NO(3))(2).6H(2)O are 0.03-1.3 ppm and 0.00031-0.013 ppm respectively, for all the trace metals except Hg. The limit is 0.00001(4) ppm for Hg in 100 g of Mg(NO(3))(2).6H(2)O. The coefficient of variation is 4-33%, depending on the trace metal.

Kinetics of the oxidation reaction of arsenious acid by peroxodisulfate ion, induced by irradiation with visible light of aqueous solutions containing tris(2,2′-bipyridine)ruthenium(II) ion

Abstract The oxidation reaction of arsenious acid (H 3 AsO 3 ) by the peroxodisulfate ion (S 2 O 8 2− ) is greatly accelerated by irradiation with visible light of aqueous acid solutions containing the tris(2,2′-bipyridine)ruthenium(II) ion (Ru(bpy) 3 ] 2+ ). The [Ru(bpy) 3 ] 2+ ion acts as a photocatalyst during the reaction. The mechanism of the reaction consists of a chain reaction being initiated by the quenching reaction of the photoexcited ruthenium(II) complex ion ([Ru(bpy) 3 ] 2+* ) with S 2 O 8 2− ion, followed by the oxidation reaction of arsenious acid by the SO 4 − radical and Rub(bpy 3 ) 3+ . The rate law is expressed by −d[S 2 O 8 2− ]/d t = k q I a o[S 2 O 8 2− ]/( k o + k q [S 2 O 8 2− ]) and the bimolecular quenching rate constants k q are determined by kinetic experiments under various conditions. The rate constants of the reaction between [Ru(bpy) 3 ] 3+ and arsenious acid are evaluated at 25 °C and ionic strength of 0.05 mol dm −3 with stopped-flow method to be 6.3, 1.2 × 10 3 , 2.2 × 10 3 and 1.1 × 10 4 dm 3 mol −1 s −1 at pH 2.6, 4.0, 6.5 and 8.1, respectively.

Light-induced electron-transfer reactions. Part 4. Kinetics of formation of hydrogen peroxide and acetone by irradiation with visible light of aqueous solutions containing tris(2,2′-bipyridine)ruthenium(II) complex, 2-propanol and oxygen

Abstract Hydrogen peroxide and acetone are formed by the light-catalyzed reaction of tris(2,2′-bipyridine)ruthenium(II) complex ([Ru(bpy) 3 ] 2+ ; bpy=2,2′- bipyridine) in an aqueous diluted sulfuric acid solutions containing 2-propanol and oxygen. The overall reaction is (CH 3 ) 2 CHOH + O 2 → H 2 O 2 + (CH 3 ) 2 CO. The amounts of hydrogen peroxide and acetone formed increase with increasing concentrations of [Ru(bpy) 3 ] 2+ , oxygen, 2-propanol, and hydrogen ion, and with increasing the amount of incident light intensity irradiated. No formation of hydrogen peroxide and acetone is found in the dark or in the absence of either [Ru(bpy) 3 ] 2+ , 2-propanol, or oxygen. The formation of hydrogen peroxide and acetone is greatly retarded by the presence of copper(II) ion. A chain mechanism of reaction is presented to account for these results obtained.

Reaction of ethylenediaminetetraacetate with aquated chromium(III) ions in mixed solvents of water with methanol and with ethanol

Abstract Kinetic studies of the reaction of ethylenediaminetetraacetate (EDTA) with aquachromium(III) ions are made in the mixed solvents of water with methanol and with ethanol at pH range 3.3–4.6. The reactions proceed only through the dissociation of the water molecules out of hexaaquachromium(III) and hydroxopentaaquachromium(III) ions, and the rate of reaction is independent of concentrations of EDTA. The results are accounted for by a mechanism of reaction: Cr(H 2 O) 6 3+ Cr(OH)(H 2 O) 5 2+ + H + Cr(H 2 O) 6 3+ Cr(edta)(H 2 O) − + 5H 2 O Cr(OH)(H 2 O) 5 2+ Cr(edta)(H 2 O) − + 4H 2 O + OH − The values of k1, k2 and Ka are determined in the mixed solvents. k1 and k2 were independent of concentrations of the alcohols. Ka was slightly decreased with increasing concentrations of the alcohols. k2 of (3.1 ± 0.7) × 10−4 s−1 was larger than k1 of (4.4 ± 2.2) × 10−6 s−1 by a factor of 102. Additions of small amounts of hydrogen peroxide and iron(II), or of peroxodisulfate and iron(II) into the reaction solutions accelerated 3–5 times the reaction between EDTA and aquachromium(III) ions in aqueous solution.

Separation and preconcentration of molybdenum (VI) ions in aqueous solution using activated carbon as a collector ; Determination of molybdenum (VI) in tap-water, river-water and seawater.

水中のモリブデン(VI)イオンについて活性炭の粒子表面での吸着特性を調べ,微量モリブデンの分離濃縮及び定量法について報告する.Mo(VI)を含む溶液200 mlに活性炭50 mgを添加して30分間かき混ぜてから濾過する.濾液中のモリブデン濃度をAAS装置を用いて測定した.モリブデン(VI)はpH 3.3～4.0において90%以上の吸着率を示した.この実験条件で吸着等温曲線を描き, Langmuirプロットをした.得られた最大吸着量は59mg g-1であった.最大吸着量は,溶液にEDTAを加えると約8分の1に減じた.そのほか,シュウ酸ナトリウム,硫酸ナトリウム,塩化カリウム,塩化マグネシウム,塩化カルシウム,硝酸亜鉛などの共存する溶液中のMo(VI)イオンの活性炭への吸着率を求めた.これらいずれの塩類も共存量が増すに伴って吸着率は低下した.特に硝酸亜鉛の共存によってMo(VI)の吸着率は著しく低下したが,8-キノリノールの添加によって吸着率は90%以上に回復した.いったんMo(VI)を吸着させてから活性炭を取り出し,0.1 M NaOHを加えるとMoは容易に脱離した.従って,水中のMo(VI)の分離濃縮を簡単に行うことができる.200 mlの試料溶液中のMo(VI)を活性炭50mgに吸着し,分離及び脱離操作を経て最終的に1mlに濃縮した場合における試料中のMoのAASによる検出限界濃度は0.0011ng ml-1の超微量である.本法を用いて,水道水,河川水及び海水中のモリブデンの分離濃縮及び定量を行った.その結果,水道水,河川水及び海水についてそれぞれ20回の操作(n=20)の平均値は,0.37(R.S.D.=14%),0.23(17%)及び7.9(8%)ng ml-1であった.

Light-induced ligand-substitution reactions—II. Reaction between the [CoBr(NH3)5]2+ ion and ethylenediaminetetraacetate by irradiation with visible light of aqueous acid solution containing the tris(2,2′-bipyridine)ruthenium(II) ion

Abstract The ligand-substitution reaction of the bromopentaamminecobalt(III) ion, [CoBr(NH3)5]2+, with ethylenediaminetetraacetate (EDTA) (which denotes all the forms of EDTA, i.e. edta4−, Hedta—, H2edta2− etc.) was induced by irradiation with visible light of aqueous solutions containing the tris(2,2′-bipyridine)ruthenium(II) ion, [Ru(bpy)3]2+. The [Co(edta)]− ion was efficiently produced in acid solutions at pH 2–3, where [Ru(bpy)3]2+ acts as an inductor and a photocatalyst. The ligand-substitution reaction constitutes a chain reaction composed of a [Ru(bpy)3]2+ and [Ru(bpy)3]3+ cycle, where the substitution reaction is initiated by the quenching reaction of the photoexcited complex [Ru(bpy)3]2+* with [CoBr(NH3)5]2+. The formation rate of [Co(edta)]− by the ligand-substitution reaction between EDTA and [CoBr(NH3)5]2+ decreased with increasing pH (pH > 3) as well as with decreasing pH (pH

Kinetics of the reducing reaction of the tris(oxalato)cobaltate)(III) ion induced by the reaction between copper(II) and thiosulfate in aqueous solution

Abstract The kinetic study of the reducing reaction of the tris(oxalato)cobaltate(III) ion ([Co(C2O4)3)3−) induced by the reaction between the copper(II) and thiolsulfate ions has been made in an aqueous solutions. The initial rate of the reducing reaction of the [Co(C2O4)3]3− ion was proportional to the initial concentrations of the [Co(C2O4)3]3− ion as well as the copper(II) ion, and was inversely proportional to those of the thiosulfate ion. The rate of the induced reducing-reaction of the [Co(C2O4)3]3− ion was greatly retarded by the presence of complex-forming substances such as ethylenediaminetetraacetate and oxalate. The mechanism of reaction is presented to account for the results obtained, and the rate constant for the reaction between copper(I) and tris(oxalato)cobaltate(III) is determined and discussed by the term of the Marcus theory.