Selective solid-phase extraction of trace thallium with nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> from environmental samples

A novel sorbent, nano-Al₂O₃ was employed for the separation and preconcentration of thallium from aqueous solution in batch equilibrium experiments. It was found that the adsorption percentage of thallium ions was close to 100% at pH 4.5, and the desorption by 1.0 mL of 0.25 M HCl reached 99%. The adsorption equilibrium was well described by the Langmuir isotherm model with maximum adsorption capacity of 5.78 mg/g (20 ± 0.1°C). The enrichment factor values of Tl(III) was 25 for 25 mL sample. Detection limit of thallium (3σ, n = 11) equal to 0.8 μg/mL and relative standard deviation (2.4%) were obtained. The method has been successfully applied to the determination of trace thallium in some environmental samples and the certified reference material polymetallic nodule (GBW07296) with satisfactory results.     

Determination trace amounts of thallium after separation and preconcentration onto nanoclay loaded with 1-(2-pyridylazo)-2-naphthol as a new sorbent

A procedure has been proposed for the separation and preconcentration of trace amounts of thallium. It is based on the adsorption of thallium ions onto organo nanoclay loaded with 1-(2-pyridylazo)-2-naphthol (PAN). Thallium ions were quantitatively retained on the column in the pH range of 3.5–6.0, whereas quantitative desorption occurs with 5.0?mL of 5% ascorbic acid and thallium was determined by flame atomic absorption spectrometry. Linearity was maintained between 0.66?ng?mL^?1–15.0?µg?mL^?1?in initial solution. Detection limit was 0.2?ng?mL^?1?in initial solution and preconcentration factor was 150. Eight replicate determinations of 2.0?µg?mL^?1 of thallium in final solution gave a relative standard deviation of ±1.48%. Various parameters have been studied, such as the effect of pH, breakthrough volume and interference of a large number of anions and cations and the proposed method was used to determine thallium ions in water and standard samples. Determination of thallium ions in standard sample showed that the proposed method has good accuracy.     

The determination of thallium in sediments and natural waters

Thallium is determined in natural waters (including sea water) by first preconcentrating it by adsorption from oxidizing medium onto a strongly basic anion exchanger as the tetrachlorothallate(III) ion. After elution with sulphur dioxide and evaporation, thallium is estimated either by graphite-furnace atomic absorption spectrometry or by differential-pulse anodic stripping voltammetry. Relative standard deviations of 4% were found for both endpoints at thallium concentrations of 15 ng l^?1. There was good agreement between the results obtained by the two techniques. The technique is also applied to digests from deep-sea sediments.     

Interaction between thallium(III) bromide and dicyclohexano-18-crown-6 immobilized on silica

The adsorption of cis-syn-cis-dicyclohexano-18-crown-6 on silica gel from organic solvents was studied. In the adsorption from chloroform solutions, the immobilization of the reagent molecules at the surface was coplanar. Hydrogen bonds between surface silanol groups and oxygen atoms of the polyether ring of the crown ether play an important role in the immobilization of the reagent. The reaction between thallium(III) bromide and the immobilized reagent was studied. The composition of complex compounds formed at the surface of the modified adsorbent was found. A procedure was proposed for the sorption-spectrophotometric determination of thallium(III) (≥0.05 mg/L) in the presence of heavy metal ions.     

Electrocatalysis by thallium adatoms of the oxidation of formic acid on platinized platinum

With the use of a complex system combining radiotracer (adsorption) and pulsed potentiodynamic measurements, the adsorption and electrooxidation of formic acid on platinum modified by thallium adatoms were investigated. New data on the mechanism of electrocatalysis by thallium adatoms of the electrooxidation process of formic acid were obtained. The inhibiting action of thallium adatoms on the formation and electrooxidation of strongly adsorbed products of formic acid was proved.     

Spectrophotometric determination of thallium as thallium tetriodide

Iodide ions react with thallic ions at pH 2–8 to form a complex iodide, which is suitable for the spectrophotometric determination of thallium. The reaction has a sensitivity of 0.05 μg Tl per cm² for log $\text{I}{}_0\text{I}$ = 0.001 and obeys Beer's law up to 40 p.p.m. Optimum conditions for the reaction have been established. The standard deviation is 0.6%. The effects of temperature and pH, the ratio of thallium to reagent, stability of the complex, its conformity to Beer's law, and the rate of color formation were studied. The effect of many diverse ions was examined.     

铊的分离富集技术

对近二十年来重金属铊的重要的和最新的分离富集技术作了系统总结和评述，并提出了在不同情况下铊分离富集方法的最优化选择，对其未来发展趋势进行了展望。     

Biosorption of toxic,heavy, no-carrier-added radionuclides by calcium alginate beads

Summary Studies on adsorption behavior of heavy radionuclides, present altogether in no-carrier-added state, e.g., ^197-200Pb, ^197-200Tl and ¹⁹⁷Hg, have been carried out with calcium alginate beads. High lead (100%) and moderate thallium removal (~65%) was achieved in pH range 2-7. 100% mercury removal was also achieved at pH 2 and 4. Effort has been made to recover all three radionuclides adsorbed in the calcium alginate beads using various chemicals, such as HCl, thiourea, sodium acetate, sodium oxalate and sodium nitrite. It was found that 0.1M HCl and 0.1M thiourea could remove at pH 1 80-90% of adsorbed Pb. Tl recovery was possible by all chemicals mentioned above. Hg was also recovered by all chemicals except HCl.     

Anion-induced adsorption of thallium complex on silver electrodes

The interfacial behavior of thallium ions on polycrystalline silver electrodes is analyzed using cyclic voltammetric and chronocoulometric and impedance studies. The specificity associated with bromide ions leading to the anion-induced adsorption of the thallium complex is pointed out and the stoichiometry of the thallium complex is deduced.     

Anodic Dissolution of Gold in Alkali–Cyanide Solutions Containing Microquantities of Mercury Ions

An admixture of mercury ions accelerates dissolution of gold at negative (in the hydrogen scale) potentials and hinders it at positive potentials. In contradistinction to a similar effect exerted by admixtures of thallium, bismuth, and lead ions, the influence of mercury ions, all other conditions being equal, manifests itself at much longer times of contact between gold and solution. This difference is due to a low rate of the act of adsorption (discharge) of mercury ions. The rate increases at more negative potentials, and at E –1.2 V (NHE) the act accelerates to such an extent that looses the limiting role, which passes to the stage of supply of mercury ions to the electrode, as with solutions containing thallium, bismuth, and lead. Comparing these results with earlier data on the adsorption of cyanide ions on gold shows that the discharge of the Hg(CN)^2- ₄ anions stops limiting the formation of a layer of mercury atoms when the adsorption of cyanide ions turns insignificant.     

The spectrophotometric determination of thallium(iii)by ternary complex formation

If thallium(III) is added to an aqueous solution of potassium thiocyanate containing a large amount of pyridine in the pH range 5.2–5.5, a yellow solution which is stable in diffuse light is obtained. The yellow colour can be measured at 405 nm for the colorimetric determination of thallium(III) in the range 20–300 μg Tl ml^-1. The complex is a mixed ligand complex with a metal-ligand ratio of 1:2:2. Thallium(I) does not interfere. The interference of various other metal ions and anions is discussed.     

Application of matrix-modification in determination of thallium in waste water by graphite-furnace atomic-absorption spectrometry

A method has been developed for the determination of thallium in waste water at the ng ml level by graphite-furnace atomic-absorption spectrometry. If microgram amounts of palladium or platinum are used as a matrix modifier, the ashing temperature for thallium can be raised to 1000 degrees , and the interference of halides and mineral acids is greatly reduced. The relative standard deviation found was 2% (9 replicate determinations) at the 8-ng ml thallium level, and the detection limit 1 ng ml .     

Speziesanalytik von Cadmium und Thallium in nativen Rapspflanzen (Brassica napus)

Summary The speciation of cadmium and thallium was studied in leaves from unpolluted rape of two different growth stages. In average the cytoplasmic fraction contained 37% of the whole cadmium or 84% of the whole thallium, respectively. Gel filtration of the cytoplasmic samples revealed a high (M>80,000 g/mol) and two low molecular weight cadmium species (M=4400 g/mol), but only one thallium species (M=3800 g/mol). No free ionic species have been detected. The determinations of metals were performed by ET-AAS, with a recovery between 60% and 90%. The low molecular weight species containing most of the cadmium was further purified by means of ion-exchange chromatography and gel filtration. The resulting strong anionic peptide showed a low absorption at 280 nm. The molar cadmium/peptide ratio was about 1/140. An amino acid analysis indicated no cysteine or methionine. Conclusively, the main cytoplasmic cadmium species in native rape neither belongs to the well known classes of sulphureous phytochelatins nor to the metallothioneins.

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Herrn Prof. Dr. Wilhelm Fresenius zum 75. Geburtstag in Verehrung gewidmet     

电感耦合等离子体质谱法快速测定尿、血液和头发中的铊含量

采用电感耦合等离子体质谱法快速测定了尿、血液和头发中的铊含量。以^115In作内标,方法检出限为0．0055ng·mL^-1（3δ）,标准曲线范围为1～1000ng·mL^-1（r=0．9998）,相对标准偏差为2．8％（n=10）,加标回收率在94％～104％之间。     

Selective preconcentration of thallium species as chloro and iodo complexes on Chromosorb 105 resin prior to electrothermal atomic absorption spectrometry

A selective preconcentration method was described for the determination of inorganic thallium species by electrothermal atomic absorption spectrometry (ETAAS). Thallium(III) and thallium(I) as chloro and iodo complexes were selectively retained by a column containing 0.5 g of Chromosorb 105 resin and quantitatively eluted by 10 mL of pure acetone. The calibration graph was linear with a correlation coefficient of 0.997 at levels near the detection limit and up to at least 0.8 μg L⁻¹. The detection limits for the determination of total thallium and thallium(III) employing the proposed method by ETAAS were estimated as three values of the standard deviations, 0.050 μg L⁻¹ and 0.034 μg L⁻¹, respectively. Verification of the accuracy was carried out by the analysis of standard reference materials (GBW 07402 soil, NIST 2710 Montana soil, GBW 07309 and GBW 07310 stream sediments). The relative errors were found to be in the range of −7.7% to +4.8%. The relative standard deviations were generally found to be below 10%. The effect of potential interfering ions on the determination was studied. The proposed method was successfully applied to the determination of total thallium in five different brand cements, soils around two cement plants and metallic zinc samples. The speciation of thallium(I) and thallium(III) was applied to synthetic solutions.     

Kinetic Separation of Oxygen and Argon Using Molecular Sieve Carbon

A pressure-swing adsorption (PSA) simulation study was performed for the separation of a mixture of 95% O₂ and 5% Ar using a molecular sieve carbon (MSC) as the adsorbent. Two PSA cycles have been outlined to maximize the recovery of either argon or oxygen as a high purity product. The effect of cycle parameters such as cocurrent depressurization pressure, purge/feed ratio, pressure ratio and adsorption pressure on the separation of O₂/Ar has been studied. It was found that it is feasible to obtain an argon product of purity in excess of 80% with reasonably high recovery using one of the cycles. The other cycle is capable of producing high purity oxygen (>99%) at high recovery (>50%) with reasonably high product throughputs. The PSA process can be conducted at room temperature and hence has an advantage over conventional processes like cryogenic distillation and cryogenic adsorption.     

Optical and electrochemical studies of the underpotential deposition of metals Part I. Thallium deposition on single crystal silver electrodes

The underpotential deposition of thallium on single crystal silver cathodes, orientations 100, 110 and 111, was investigated optically and voltammetrically. Careful chemical polishing of the silver surfaces was necessary to reveal the fine structure on the voltammograms reproducibly. The deposition process for the first monolayer was shown to be the formation of a layer of adsorbed atoms initially, followed by a phase transformation to form a crystal plane by two-dimensional nucleation and growth. The extent of the initial adsorption was related to the number of favourable sites on each crystal face such that the adsorbed layer formed a superlattice. The influence of the substrate structure was seen on the formation of the second thallium monolayer. The formation of this layer also involved adsorption followed by transformation into a crystal plane.     

Substoichiometric radiochemical determination of thallium with sodium isopropyl xanthate

A rapid radiochemical method for the determination of thallium(III) has been developed based on the substoichiometric extraction of its 13 complex with sodium isopropyl xanthate into chloroform from pH 9 ammonia buffer. The effect of foreign ions on the extraction was also studied. 10 g amounts of thallium were determined with an average error of 1.9%. The method has been successfully applied for the determination of thallium content present in sphalarite ores collected from Jawar Mines, Rajasthan (India).     

泡沫塑料富集–石墨炉原子吸收光谱法测定贝类水产品中痕量铊

采取微波消解的前处理手段消解样品,经泡沫塑料分离富集后,用石墨炉原子吸收光谱法测定贝类水产品中痕量铊。以1.5 mL Fe3+,2 mL H2O2和5%王水介质作为吸附体系将样品中铊分离富集,再以硝酸钯、抗坏血酸作为基体改进剂进行测定。铊的质量浓度在0～50μg/L范围内线性良好,相关系数为0.999 7,方法的检出限可达0.07μg/g。测定结果的相对别准偏差为1.53%～4.01%(n=7),加标回收率为87.1%～98.3%。泡沫塑料富集–石墨炉子吸收光谱法测定贝类水产品中痕量铊是一种准确、安全、便捷的检测方法。     

Extraction-fluorimetric determination of microgram amounts of thallium with 2-phenylbenzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium perchlorate

In 0.5 M hydrochloric acid medium, thallium(III) forms with 2-phenylbenzo [8,9]quinolizino[4,5,6,7-fed]phenanthridinylium perchlorate (PQPP) an ion-association compound which is extractable in isoamyl acetate. The extracted ion-pair has a mole ratio Tl/PQPP in 1:1 and has been used for the spectrofluorimetric determination of thallium in the concentration range 0.06–1.6 μg per 5 ml of organic layer. The interference of a large number of foreign ions has been investigated. The method is sensitive, accurate, precise, and specially useful for the determination of thallium in different materials with low contents of this element.