Sodium Tellurate Research Articles

Synthesis, crystal structure and investigation of ion-exchange possibility for sodium tellurate NaTeO3(OH).

A new sodium tellurate has been hydrothermally synthesized and comprehensively analysed using spectroscopic and thermogravimetric techniques, resulting in the determination of its composition as NaTeO3(OH). The analysis of synchrotron X-ray and neutron diffraction data indicates that NaTeO3(OH) has a crystal structure similar to that of the previously reported tellurate, KTeO3(OH), with the space group P21/a (No. 14). NaTeO3(OH) consists of zigzag one-dimensional chains built by edge-sharing TeO6 octahedra, running parallel to the c-axis and connected to sodium and hydrogen atoms. The hydrogen atoms covalently bond to the terminal oxygen atoms on the one-dimensional chain and also form hydrogen bonds with other terminal oxygen atoms on nearby chains. The structure has been confirmed by optimization using the pseudopotential method and performing Bond Valence Sum (BVS) analysis. Although Li+ ions in LiTeO3(OH) can be exchanged reversibly with H+ ions, no ion exchange behaviour is observed in NaTeO3(OH). The difference is attributed to the size of the alkali ions and their crystal structure.

Formation of biogenic tellurium nanorods in unicellular green alga Chlamydomonas reinhardtii.

Tellurium (Te) is an industrially useful element but causes environmental contamination. The formation of biogenic Te nanorods (Te-BgNRs) in plants is one of the Te detoxification pathways associated with the phytoremediation of Te because Te-BgNRs contain low-toxicity Te at high densities. In this study, we investigated the mechanism of Te-BgNR formation in a common unicellular green alga, Chlamydomonas reinhardtii, on the basis of elemental analysis by inductively coupled plasma mass spectrometry (ICP-MS). After exposure to 1000 μM sodium tellurate (Na2TeO4) for 2 weeks, the alga accumulated 65.2 fg of Te per cell, and 55.8% of which was present in an insoluble form. Electron microscopic observations revealed that the insoluble Te was rod-shaped elemental Te, i.e. Te-BgNRs, and had a highly crystalline nanostructure. We determined the Te contents in Te-BgNRs by single-particle ICP-MS analysis and found that these nanorods were formed at tellurate exposure concentrations of 100 to 1000 μM. In contrast, soluble Te compounds were found in algal cells even at exposure concentrations lower than 100 μM. These findings suggest that the algal cells initially metabolized tellurate to form soluble Te compounds, and excess tellurate that could not be metabolized was then transformed to Te-BgNRs, which are less toxic than tellurate. Our findings provide a novel approach to Te remediation through the formation of BgNRs in C. reinhardtii.

Cellulose derivatives modified by sodium tellurate and a chromium(III) tellurate complex

A novel cellulose (Cell) derivative, sodium-tellurato (Cell-TeO(OH)4(ONa)/Cell-Cl), has been synthesized from the reaction of 6-chloro-6-deoxycellulose (Cell-Cl) with telluric acid in the presence of sodium hydroxide. The subsequent reaction of this polymeric material with chromium(III) in aqueous solution yields the [Cr(Cell-TeO3(OH)3/Cell-Cl)(Cell-TeO2(OH)4/Cell-Cl)(H2O)3] complex. The molecular structures and morphology of the new polymer and the Cr(III) complex have been examined using elemental analysis, solid-state 13C NMR, UV–vis, XRD and FTIR spectroscopy, and SEM-EDX, TGA and magnetic measurements. The results are considered to be consistent with the formulations proposed. The deprotonation constants of the modified cellulose and the stability constant of the Cr(III) complex have been determined by pH-metric measurements.

Speciation and identification of tellurium-containing metabolites in garlic, Allium sativum

Tellurium (Te) is a widely used metalloid in industry because of its unique chemical and physical properties. However, information about the biological and toxicological activities of Te in plants and animals is limited. Although Te is expected to be metabolized in organisms via the same pathway as sulfur and selenium (Se), no precise metabolic pathways are known in organisms, particularly in plants. To reveal the metabolic pathway of Te in plants, garlic, a well-known Se accumulator, was chosen as the model plant. Garlic was hydroponically cultivated and exposed to sodium tellurate, and Te-containing metabolites in the water extract of garlic leaves were identified using HPLC coupled with inductively coupled plasma mass spectrometry (ICP-MS) or electrospray tandem mass spectrometry (ESI-MS-MS). At least three Te-containing metabolites were detected using HPLC-ICP-MS, and two of them were subjected to HPLC-ESI-MS-MS for identification. The MS spectra obtained by ESI-MS-MS indicated that the metabolite was Te-methyltellurocysteine oxide (MeTeCysO). Then, MeTeCysO was chemically synthesized and its chromatographic behavior matched with that of the Te-containing metabolite in garlic. The other was assigned as cysteine S-methyltellurosulfide. These results suggest that garlic can assimilate tellurate, an inorganic Te compound, and tellurate is transformed into a Te-containing amino acid, the so-called telluroamino acid. This is the first report addressing that telluroamino acid is de novo synthesized in a higher plant.

An improved hydrometallurgical route for tellurium production

In recent years, tellurium has been extensively used in the manufacture of semiconductor materials. For this type of application, high-purity tellurium is required. Selenium, lead and silicon are usually the main impurities in tellurium. During the electrolytic refining of copper, tellurium gold and silver are collected in the anode slimes. A pyrometallurgical treatment is used to recover gold and silver from the decopperized anode slimes whereas tellurium is oxidized and skimmed off from the refining furnace as a Na2CO3-based slag. In the slag, tellurium is present as sodium tellurite (Na2TeO3), which is further water-leached from the slag. The first step in the conventional process for tellurium recovery consists of the precipitation of the tellurium contained in the leaching solution as tellurium dioxide (TeO2). The solid TeO2 is then dissolved under acidic conditions for its further reduction with sulfur dioxide gas (SO2). In this paper, an alternative route for tellurium production is presented in which a sodium tellurate [Na2TeO4] intermediate is obtained by oxidation of the sodium tellurite in an alkaline solution following the water leaching step. Sodium tellurate is then dissolved in acid media and high-purity tellurium is obtained by reduction with SO2 gas. Experimental tests under laboratory conditions indicate that the novel process yields higher precipitation selectivity for tellurium than the conventional process. A comparison of its efficiency concerning impurities co-precipitation with respect to the conventional process is discussed.

Preparation by Hydrothermal Techniques in a Tungstosilicate Acid Solution System and Optical Properties of Tellurium Nanotubes

AbstractSingle‐crystalline tellurium nanotubes can be easily synthesised by a simple hydrothermal, economical and green chemical route. The tungstosilicate acid (TSA) serves as not only an effective reducing agent but also a new morphology‐directing agent for tellurium nanotubes from sodium tellurate (Na2TeO3) precursor powders. Scanning electron microscopy images show that most of the tellurium nanotubes have sloping cross‐sections and open ends with outer diameters of 100–500 nm, wall thicknesses of 30–100 nm and lengths of 30–50 μm. A few Te nanotubes have hexagonal cross‐sections. Te nanotubes grow along the [001] direction and have excellent crystallinity. The synthetic conditions also investigated for the tellurium nanotubes were molar ratio of sodium tellurate to TSA, pH of reaction solution and reaction temperature. The optical properties of the t‐Te nanotubes have been investigated. A possible mechanism for the growth of tellurium nanotubes has been discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

DNA-damage induction by eight metal compounds in TK6 human lymphoblastoid cells: Results obtained with the alkaline Comet assay

Metal compounds are long-lived and can react with different macromolecules, producing a wide range of biological effects, including DNA damage. Since their reactivity is associated with their chemical structure, it is important to obtain information on more than one compound from the same metal. In this study, the DNA-damaging potential of two mercury compounds (mercury chloride and methyl mercury chloride), two nickel compounds (nickel chloride and potassium hexafluoronickelate), two palladium compounds (ammonium tetrachloropalladate and ammonium hexachloropalladate), and two tellurium compounds (sodium tellurite and sodium tellurate) was evaluated in human lymphoblastoid TK6 cells by use of the alkaline version of the Comet assay. As the use of computerized image-analysis systems to collect comet data has increased, the metric used for quantifying DNA damage was the Olive tail moment. Treatments lasted for 3 h and the range of concentrations tested was different for each metal compound, depending on its toxicity. Both mercury agents produced DNA damage in TK6 cells, with mercury chloride producing considerably more DNA damage than methyl mercury chloride. Of the two nickel compounds, only nickel chloride (a Ni(II) compound) induced DNA breaks. Similarly, of the two palladium compounds, only the Pd(II) compound (ammonium tetrachloropalladate) was positive in the assay. Sodium tellurite was clearly positive, producing concentration-related increases in DNA damage, while sodium tellurate gave a negative response. In conclusion, the ability of inducing DNA damage by the selected metal compounds in human TK6 cells, when measured with the Comet assay, was dependent on the chemical form and, in general, compounds containing the metal in the lower valence state displayed the greater DNA-damaging ability.

Synthesis, Characterization, and Growth Mechanism of Tellurium Nanotubes

A simple hydrothermal reduction method, employing sodium tellurate (Na2TeO4·2H2O) as tellurium source and formamide (HCONH2) as a reductant, was used to prepare and investigate tellurium nanotubes. The diameters of the nanotubes range from 200 to 600 nm and their lengths from 4 to 15 μm. Unlike studies reported previously,1,2 a series of electron microscopy characterization results suggests that the growth of tellurium nanotubes under the present experimental conditions is governed by a nucleation−dissolution−recrystallization growth mechanism: sphere-like tellurium nanoparticles initially formed in the hydrothermal system; the sphere-like nanoparticles were gradually dissolved to generate free tellurium atoms in the solution; these tellurium atoms were renewedly transferred onto the surfaces of the sphere-like nanoparticles and evolved into groove-like nanorods; the groove-like nanorods could be grown into tellurium nanotubes eventually.

Production of dimethyl telluride and elemental tellurium by bacteria amended with tellurite or tellurate

AbstractThe purpose of this study was to determine whether a facultative anaerobe, Pseudomonas fluorescens K27, would produce dimethyl telluride when anaerobic cultures were amended with differing concentrations of sodium tellurate and/or sodium tellurite and how that volatile organotellurium production varied over time. Batch bacterial bioreactor experiments were undertaken in order to observe the changes in the headspace of a growth medium solution inoculated with P. fluorescens and amended with tellurium salts. Gas samples were taken from the bioreactor every hour and were analyzed by capillary gas chromatography using fluorine‐induced chemiluminescence detection to determine compounds in the headspace. Liquid samples were analyzed by spectrophotometer to determine optical densities, which were used as an indicator of cell growth. Verification of the identity of the dimethyl telluride produced in the bacterial headspace above a tellurate‐amended culture was achieved by comparison with the chromatographic retention time of an authentic (CH3)2Te standard and by gas chromatography/mass spectrometry. The time course production of dimethyl telluride varied with amendment salts' tellurium oxidation states and concentrations. Increasing tellurate concentrations caused slower bacterial growth, but those cultures reached the stationary phase sooner than cultures amended with tellurite concentrations 10 or 100 times less. Black elemental tellurium (Te0) was produced by live cultures amended with tellurium salts but not by sterile controls. The amount of tellurium in the solid phase (as Te0 and in/or on cells) harvested from replicate, anaerobic cultures of P. fluorescens sampled after 92 h of incubation was approximately 34%. Mixed tellurite/tellurate amendment experiments exhibited a synergistic toxic effect and yielded less final biomass and very little dimethyl telluride production compared with cultures amended with either tellurate or tellurite alone. Copyright © 2001 John Wiley & Sons, Ltd.

Mixed former effect in sodium phospho tellurate glasses

Glasses in the binary system xNa 2 P 2 O 6-( l − x) Na 2 Te 2 O 5 have been synthesised for 0≤ x ≤1. For all compositions, the glasses are transparent and appear homogeneous. Nevertheless for compositions near x = 0.4 glasses seem to be heterogeneous on SEM observations. Glass transition temperatures for all the compositions are between 220 and 310 °C. Conductivity data have been obtained using impedance techniques in the 100–250 °C temperature range. The σT product obeys an Arrhenius relationship with a composition-independent pre-exponential term A. The value of log A ≈ 4.8 is in agreement with an indirect interstitial mechanism model for sodium cation migration. Isothermal conductivity curves with x show a maximum in the ionic conductivity. This mixed network former effect may be justified by assuming an endothermic mixture between sodium phosphate and sodium tellurate.

Renal Excretion After Peroral Administration of Tellurium to Humans

Abstract The present study was aimed to investigate the renal excretion of tellurium after oral administration in various forms to male volunteers. In a total of 12 experiments on 5 healthy subjects tellurium was given as sodium tellurate, sodium tellurite, metallic colloid, and intrinsically bound in cress. Tellurium concentrations were measured by means of graphite furnace atomic absorption spectroscopy. From the cumulated tellurium concentrations in the first four days a mean percentage intestinal absorption of 28% ± 11% was calculated. The introduction of tellurium to cress did not alter the intestinal absorption significantly. For metallic tellurium the intestinal uptake was about 15%. The renal excretion is faster after administration of the hexavalent tellurium than after ingestion of tetravalent form.

Sodium Tellurite as a Mild and Selective Oxidizing Agent for Thiols: Its Use in the One-Pot Synthesis of Unsymmetrical Disulfides

Abstract Sodium tellurite acts as a mild and highly selective oxidizing agent for thiols under phase-transfer conditions at room temperature. Aromatic and benzylic thiols are rapidly converted to disulfides. Short-chain primary thiols undergo oxidation in preference to long-chain thiols. Secondary thiols are sluggish in oxidation and tertiary thiols remain intact. No overoxidation of the sulfur atom is observed. Similar results are also obtained with sodium tellurate.

Thermal Annealing of Tellurium resulting from Isomeric Transition in Solid Sodium Tellurate

LITTLE attention has hitherto been directed to the chemical effects of radioactive decay in ionic crystals. Two papers are devoted to β-decay. Baro and Aten1 have examined the distribution of arsenic-77, formed by β-decay of germanium-77 in GeO2, between tri- and pentavalent states, and Andersen and Knutsen2 the distribution of antimony-125, formed by β-decay of tin-125 in K2SnCl6. In both papers a small annealing effect has been reported. The yield of arsenic and antimony in the pentavalent state increased on heating. Campbell3 has found that on heating sodium bromate crystals containing bromine-80m the distribution of bromine-80 resulting from isomeric transition is not changed.

Ion-exchange studies of solutions of tellurates

The sorption of tellurium and of chloride by Amberlite I.R.A. 400-Cl from telluric acid solutions, containing 1·0-0·07 g atoms of tellurium per litre, has been studied at various pH values. The results have been interpreted in terms of the sorption of a tetra- and a tri-tellurate ion, in addition to the non-condensed ions H 5TeO 6 − and H 4TeO 6 =. The actual ions sorbed appear to depend both upon the pH and the tellurium concentration of the solutions. An attempt was made to correlate the data obtained by ion-exchange methods with those supplied by an examination of the ultra-violet absorption spectra of telluric acid and sodium tellurate solutions.