Telluric Acid Research Articles

Can Telluric Acid Replace Chromate as a Homogeneous Catalyst in the Chlorate Process?

AbstractFinding an alternative to Cr(VI) as catalyst for the conversion of hypochlorite/hypochlorous acid to chlorate is of critical importance to render the industrial chlorate process safe and sustainable. Recently, telluric acid was identified as a potential replacement but its performance under industrial conditions and its interactions with other parts of the process are still unknown. These factors are elucidated by a combination of density functional theory (DFT) modeling and pilot plant studies. Our results indicate, that the addition of telluric acid indeed has a beneficial effect on the decomposition of HOCl to chlorate. The increased performance, shown as a decreased oxygen formation and an increase in anodic current efficiency. It is mostly related to a buffering effect and an increased selectivity for chlorate formation. Unfortunately, a low cathodic current efficiency was achieved due to reduction of telluric acid to solid Te/TeO2 particles in the electrolyte and at the cathode. Despite the benefits of buffering effects and increased selectivity for chlorate formation, telluric acid is unsuitable as replacement for Cr(VI) in the chlorate process due to lack of compatibility with all process conditions.

Effect of B2O3 on the Structure, Properties and Antibacterial Abilities of Sol-Gel-Derived TiO2/TeO2/B2O3 Powders.

This paper studies the influence of B2O3 on the structure, properties and antibacterial abilities of sol-gel-derived TiO2/TeO2/B2O3 powders. Titanium(IV) butoxide, telluric(VI) acid and boric acid were used as precursors. Differences were observed in the degree of decomposition of Ti butoxide in the presence of H3BO3 and H6TeO6 acids. The phase transformations of the obtained gels in the temperature range of 200-700 °C were investigated by XRD. Composite materials containing an amorphous phase and different crystalline phases (metallic Te, α-TeO2, anatase, rutile and TiTe3O8) were prepared. Heating at 400 °C indicated a crystalline-to-amorphous-phase ratio of approximately 3:1. The scanning electron microscopy (SEM) analysis showed the preparation of plate-like TiO2 nanoparticles. The IR results showed that the short-range order of the amorphous phases that are part of the composite materials consists of TiO6, BO3, BO4 and TeO4 structural units. Free B2O3 was not detected in the investigated compositions which could be related to the better connectivity between the building units as compared to binary TiO2/B2O3 compositions. The UV-Vis spectra of the investigated gels exhibited a red shift of the cut-off due to the presence of boron and tellurium units. The binary sample achieved the maximum photodegradation efficiency (94%) toward Malachite green dye under UV irradiation, whereas the ternary sample photoactivity was very low. The compositions exhibited promising antibacterial activity against E. coli NBIMCC K12 407.

A method to load tellurium in liquid scintillator for the study of neutrinoless double beta decay

A method has been developed to load tellurium into liquid scintillator so as to permit searches for neutrinoless double beta decay with high sensitivity. The approach involves the synthesis of an oil-soluble tellurium compound from telluric acid and an organic diol. The process utilises distillable chemicals that can be safely handled underground and affords low radioactive backgrounds, low optical absorption and high light yields at loading levels of at least several percent Te by weight.

A novel approach in synthesizing Te-diol compounds for tellurium-loaded liquid scintillator

Tellurium-loaded liquid scintillator provides a competitive way for searching neutrinoless double beta decay due to the huge cost advantages. A reliable technique needs to be developed to load tellurium into liquid scintillator (LS) without severely affecting the optical properties and stability of LS. Soluble and transparent Te-diol compounds would be a good choice. A novel synthesis method based on the characteristics of the reactions between telluric acid and diols is reported in this paper. The products show quite good stability and transparency by removing water from the reaction system continuously during synthesis. A sample prepared using this method with 0.6% Te loaded shows very limited influence on the absorbance of scintillation solvent around 430 nm and remained the same within the equipment sensitivity (10−4) for six months. The method can also be extended to many other diols which will greatly expand the range of candidate Te-diol compounds.

Sol-Gel Obtaining of TiO2/TeO2 Nanopowders with Biocidal and Environmental Applications

TiO2/TeO2 powders were obtained by an aqueous sol-gel method. Telluric acid (H6TeO6) and titanium butoxide were used as precursors. The as-prepared gel was step-wisely heated in the temperature range 200–700 °C and subsequently characterized by XRD, IR, and UV-Vis analysis and SEM. Mixtures containing TiO2 (anatase), α-TeO2 (paratellurite), and TiTe3O8 were established by XRD as final products, depending on heating temperature. The thermal stability of the obtained gels in the temperature range 100–400 °C was investigated. It was found by IR spectroscopy that the samples heated up to 300–400 °C consist mainly of an organic–inorganic amorphous phase which is transformed into an inorganic one above these temperatures. The microstructure of the gels was verified by scanning electron microscopy (SEM). The photocatalytic degradation of the synthesized nanopowders toward Malachite green organic dye (MG) was examined in order to evaluate the potential applications for environmental remediation. The prepared TiO2/TeO2 samples showed up to 60% decoloration efficiency after 120 min exposure to UV-light. The composition exhibited good antimicrobial activity against E. coli K12. The properties of the obtained material were investigated by the reactions of complete catalytic oxidation of different alkanes and toluene, and it could be suggested that TiO2/TeO2 powders are promising material for use as an active phase in environmental catalysts.

AIO3·H6TeO6 (A = NH4+, Rb+): Two telluric acid and iodate Co-crystalline compounds with second harmonic generation response

Two co-crystalline compounds containing telluric acid and iodate, namely AIO3·H6TeO6 (A ​= ​Rb+, NH4+), were investigated as potential nonlinear optical materials. They crystallize into isostructural and consist of isolated [IO3] group and [H6TeO6] molecule linked by hydrogen bonds and charge interactions of Rb+/NH4+. They show phase-matching second harmonic generation responses with moderate intensity of 1.2 ​× ​KDP (Rb+) and 1.1 ​× ​KDP (NH4+). They also possess large optical band gaps over 4.25 ​eV and can be easily grown from aqueous solutions. The local dipole moment calculations based on the structures of AIO3·H6TeO6 (A ​= ​K+, Rb+, NH4+) series of compounds indicate that the change of A+ cation in their structural frame causes a slight change in the arrangement directions of [IO3] and [Te(OH)6] groups, and further induces their SHG responses of different intensities at the macroscopic level.

Characterization and catalytic reactivity of xerogel catalysts based on mesoporous zirconia doped with telluric acid prepared by sol–gel method: mechanistic study of acetic acid esterification with benzyl alcohol

Characterization and catalytic reactivity of xerogel catalysts based on mesoporous zirconia doped with telluric acid prepared by sol–gel method: mechanistic study of acetic acid esterification with benzyl alcohol

Potential catalysts for the production of NaClO3 in the decomposition of HOCl

By pursuing the aim of identifying new types of catalysts in the electrolytic production of NaClO3 from NaCl (chlorate process), we report a detailed study on the decomposition of hypochlorous acid accelerated by yttrium(III) chloride (YCl3), yttrium(III) oxide (Y2O3) and telluric acid (Te(OH)6) at 80°C. The results were compared with those obtained in the uncatalyzed and chromium(VI) catalyzed reactions. In general, the decomposition of HOCl occurs via two competing paths toward the formation of ClO3− or O2. In the case of YCl3, the decomposition proceeds via the oxygen path over the entire studied pH range. Y2O3 slightly catalyzes the chlorate path under acidic conditions, however the noted catalytic effect is probably due to the “self-buffering” of the reaction mixture (Y2O3 suspension). Although, a real catalytic process takes place in the presence of Te(OH)6, a significant pH-effect is also observed which is most likely associated with the acid–base equilibria of telluric acid. pH dependent studies demonstrate that the optimum pH of decomposition is at around 6.7–6.9 in this case. The comparison of the results obtained in the presence of chromium(VI) and Te(OH)6 reveals that the former is a more active catalyst. On the basis of kinetic and stoichiometric results, it is reasonable to assume that Te(OH)6 may be utilized as an alternative catalyst in the chlorate process.

Specific Absorption Coefficient of Cobalt(II) Ions in Molybdenum-Containing Zinc Tellurite Glass

TeO2–ZnO–MoO3 glasses containing cobalt(II) ions in the concentration range from 0.035 to 1.2 wt % have been prepared using orthotelluric acid, ammonium heptamolybdate, zinc nitrate, and cobalt(II) nitrate as starting materials. In the wavelength range from 0.42 to 3.0 μm, the transmission spectra of the glasses contain two strong absorption bands, peaking at ~584 and ~1357 nm. Using a series of glasses doped with 3.5 × 10–2 to 1.2 wt % cobalt, the specific absorption coefficient of Co2+ ions has been determined (3550 ± 210 dB/(km ppm) at 584 nm) and its spectral dependence has been obtained in the wavelength range studied.

Microwave field: Temperature-dependent dielectric properties and heating characteristics during the synthesis of alpha-tellurium dioxide

The temperature-dependent dielectric properties of the precursor can provide theoretical support for microwave synthesis related materials. Herein, temperature-dependent dielectric properties and microwave heating characteristics were researched in detail during the synthesis of alpha-tellurium dioxide (α-TeO2) by a microwave removal of hydrogen from orthotelluric acid (H6TeO6). The results showed that the dielectric constant (εr′) and the dielectric loss (εr″) values of H6TeO6 were divided into six stages due to the evolution of the structure with increasing temperature. And the loss tangent coefficient (tanδ) values had two distinct wave crests: 200–400 °C, and 450–600 °C, which corresponded to maximum tanδ values of 0.044 (F/m) at 350 °C and 0.028 (F/m) at 550 °C, respectively. In addition, TG-DSC, XRD, FT-IR, SEM were employed to track the as-synthesized evolution of structure and morphology during calcination. The results indicated that the fine and uniform α-TeO2 particles could be obtained by the microwave treatment at 600 °C for 10 min. The work not only provides a stable and high-quality precursor for the application of α-TeO2, but also offers theoretical data support for microwave preparation and design of tellurium oxide-based materials.

Optical properties of the zinc-tellurite glasses doped with Cr3+ ions

The zinc-tellurite glasses doped with Cr3+ ion have been synthesized using orthotelluric acid, zinc nitrate, and ammonium dichromate as raw materials. According to the yielded results, Cr3+ ions in the spectral range from 0.3 to 2.8 µm demonstrate two intense broad bands with maxima 454 and 650 nm, corresponding to the transitions 4A2g(F) → 4T1g(F) and 4A2g(F) → 4T2g(F). For the studied wavelength range the spectral dependence of the specific coefficient of Cr3+ allows establishing the minimum chromium content for achieving the determined level of optical losses in glasses. The electron paramagnetic resonance spectra of the doped glasses demonstrate that ions Cr3+ are presented both in the isolated ions and in Cr3+−Cr3+ paired in the distorted octahedral site. The optical band gap, Urbach energies, the crystal field and Racah parameters of the prepared glasses have been evaluated.

Telluric acid ameliorates hepatic ischemia reperfusion-induced injury in rats: Involvement of TLR4, Nrf2, and PI3K/Akt signaling pathways

In past tellurium-based compounds had limited use, however, their therapeutic potential have been target of interest recently due to antioxidant and anti-inflammatory capabilities in experimental endotoxemia. Nevertheless, their potential hepatoprotective effect against ischemia reperfusion (IR) injury is still obscure. This study examined the possible hepatoprotective effect of telluric acid (TELL), one of tellurium-based compound, against the deteriorating effect hepatic IR injury in rats through directing toll like receptor-4 (TLR4) cascade, phosphoinositide 3-kinase(PI3K)/Akt axis, and nuclear erythroid-related factor-2 (Nrf-2) pathway as possible mechanisms contributed to TELL’s effect. Indeed, male Wistar rats were randomized into 3 groups: sham-operated, control IR and TELL (50 µg/kg). TELL was administrated once daily for seven consecutive days prior to the IR induction. Pretreatment with TELL attenuated hepatic IR injury as manifested by hampered plasma aminotransaminases and lactate dehydrogenase activities. Also, TELL opposed IR induced elevation in tissue expression/activity of high-mobility group box protein-1 (HMGB1), TLR4, myeloid differentiation primary-response protein 88 (MyD88), phospho-nuclear factor-kappa B p65 (p-NF-κB p65), phospho-mitogen activated protein kinasep38 (p-MAPKp38) and tumor necrosis factor-alpha (TNF-α). Moreover, TELL reduced the elevated thiobarbituric acid reactive substances along with increased both Nrf-2 and endothelial nitric oxide synthase (eNOS) protein expression, beside replenishment of hepatic reduced glutathione. In addition, TELL induced obvious upregulation of p-PI3K and p-Akt protein expressions together with restoration of histopathological changes in IR injury. In conclusion, TELL purveyed conceivable novel hepatoprotective mechanisms and attenuated events associated with acute hepatic injury via inhibition of TLR4 downstream axis and activation of Nrf-2 and PI3K/Akt signaling cascades. Thus, TELL may provide a novel therapeutic potential for complications of hepatic IR injury.

Removal of toxic tellurium (IV) compounds via bioreduction using flucloxacillin in aqueous acidic medium: A kinetic and mechanistic approach

This paper describes a novel method for the removal of potassium tellurite (TeIV), a toxic tellurium (IV) compound, via its bioreduction using the drug flucloxacillin (Flx) in an aqueous sulfuric acid solution. The kinetics of the bioreduction process were monitored using UV–Vis absorption spectra at an ionic strength of 2.0 mol dm−3 and 298 K. The reaction between TeIV and Flx was set at a 1:1 stoichiometry. The reduction reaction followed first-order kinetics for [Flx] and fractional-first-order kinetics for [TeIV] and [H+]. The effects of ionic strength and relative permittivity of the reaction medium were also explored. Supplementation with divalent transition metal ions enhanced the reduction rate. The reaction products were identified, in order of their stoichiometric results, spot tests and FT-IR spectra as 3-(2-chloro-6-fluorophenyl)-5-methylisoxazol-4-carbocylic acid, 5,5-dimethyl-thiazolidine-2,4-dicarboxlic acid, ammonium ion, carbon dioxide and elemental tellurium (Te0). The reaction rate dependence on temperature was studied, and the activation and thermodynamic parameters were assessed and discussed. The derived rate-law expression was found to be in excellent accordance with the acquired investigational outcomes. A conceivable reaction mechanism has been provided, which includes a reaction between the protonated flucloxacillin (Flx+) and tellurous acid (H2TeO3) as the essential reactive species, resulting in the construction of an intermediate complex. Such complex decays in the rate-determining step to yield the final reaction products.

Specific Absorption Coefficient of Cr3+ Ions in (TeO2)0.70(ZnO)0.30 Glass

(TeO2)0.70(ZnO)0.30 tellurite glasses doped with Cr3+ ions in the concentration range 80 to 2500 ppm have been prepared via melt solidification using orthotelluric acid and zinc nitrate, and their optical transmission has been measured in the wavelength range 0.3 to 2.7 μm. Transmission spectra of the glasses have been shown to contain two strong absorption bands, peaking at 460 and 650 nm. Using a series of glasses differing in chromium content, we have evaluated the spectral dependence of the specific absorption coefficient for the glasses, which has been shown to be 142 ± 2 cm–1/wt % at the maximum of the 650-nm absorption band.

Pyridine-3-carboxamide-telluric acid (1/1).

In the title structure, C6H6N2O·H6O6Te, the pyridine-3-carboxamide and telluric acid mol-ecules are inter-connected by conventional O-H⋯N, N-H⋯O and O-H⋯O hydrogen bonds of moderate strength as well as by π-π inter-actions between the pyridine rings. The strongest hydrogen bond in the structure is formed between a hydroxyl group of the H6TeO6 mol-ecule and the N-pyrimidine N atom. The structure is unusual because of presence of the alternating sheets, which contain H6TeO6 and pyridine-3-carboxamide mol-ecules, respectively. These sheets are aligned parallel to (001).

Optical properties of zinc tellurite glasses doped with Cu2 + ions

Copper-containing ZnO–TeO2 glasses were synthesized using orthotelluric acid, zinc nitrate and the formed batch was doped with copper nitrate. EPR and optical spectra in a wide transparency range from were measured for all glass samples. The values of the spin-Hamiltonian parameters indicate that the Cu2+ ions in the glasses are present in octahedral coordination with some trigonal distortion. The molecular orbital bonding parameters have been calculated and were found to be independent of Cu2+ concentration in glasses. The optical transmittance spectra of doped glasses show a single broad band at 820nm, which was assigned to the overlapping 2B1g→2B2g, 2B1g→2Eg and 2B1g→2A1g electronic transitions. The spectral dependence of the specific absorption coefficient of Cu2+ ions was calculated for glass samples in the range of 310–2800nm and was found that the specific absorption coefficient at 820nm is (103±1) cm−1/(wt%) and the integral absorption coefficient in the range 0.5–2.8μm is (63±2) cm−2/(ppm wt). From the optical data some optical parameters such as the optical energy gap, Urbach energy, metallization criterion and the cut-off wavelength were calculated. It is observed that the optical band gap decreases with an increase in concentration of copper content.

Telluric Acid Ameliorates Endotoxemic Kidney Injury in Mice: Involvement of TLR4, Nrf2, and PI3K/Akt Signaling Pathways.

Being one of the most abundant trace elements in the human body, the therapeutic potential of tellurium-based compounds has been a target of interest. Recent reports denoted their redox-modulating and anti-inflammatory activities in experimental endotoxemia. However, their potential nephroprotective effect against endotoxemic kidney injury is yet to be elucidated. This study investigated the possible renoprotective effect of telluric acid (TEL) against lipopolysaccharide (LPS)-induced acute kidney injury (AKI) in mice, targeting toll-like receptor 4 (TLR4), phosphoinositide 3-kinase (PI3K)/Akt, and nuclear factor-erythroid 2-related factor-2 (Nrf2) pathways as possible mechanistic contributors to TEL's effect. AKI was induced by LPS (2mg/kg). TEL (60μg/kg; i.p.) was administered once daily for seven consecutive days before LPS injection. Pretreatment with TEL alleviated LPS-induced AKI as evidenced by the hampered serum levels of creatinine and cystatin C. TEL also opposed LPS-induced elevation in renal kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, nuclear factor-kappa B p65, interleukin-1β, and thiobarbituric acid-reactive substance contents. This was accompanied by a replenishment of renal glutathione, transcriptional upregulation of Nrf2, enhancement of heme oxygenase-1 activity, and a marked upregulation of phospho-PI3K and phospho-Akt protein expressions. Histopathological findings corroborated with the amendment of biochemical parameters. In view of these findings, we may conclude that TEL pretreatment purveyed novel nephroprotective effects against endotoxemic kidney injury, which might be partly attributed to the modulation of TLR4, PI3K/Akt, and Nrf2 signaling pathways and may hence provide a valuable asset for the management of endotoxemic renal complications.

A Comparative Study of Physical and Chemical Method for Separation of Benzoic Acid from Industrial Waste Stream

Phthalic anhydride is manufactured by the partial oxidation of ortho xylene in the presence of V2O5/TiO2 catalyst. In the residue, maleic acid, benzoic acid (BA), telluric acid and traces of other organic compounds are present in the by-product stream. There is almost 60% of (BA) in the residue sample, which compels to recover the tremendous amount of (BA), as it is of great importance. The waste stream is in the form of slurry at high temperature and is solidified at room temperature. Benzoic acid was selectively removed from the solid waste of Phthalic anhydride production industry by the processes associated with less intensive parameters as compare to the extraction techniques achieved by, pressurized hot water, supercritical CO2 extraction, where the required parameters are highly intensive. The separation has been performed by using physical and chemical techniques. In physical methods recrystallization (RE), liquid-liquid extraction (LLE) as well as recrystallization followed by liquidliquid extraction (RE, LLE) and liquid-liquid extraction followed by recrystallization (LLE, RE) have been studied. In another attempt chemical derivatization (CD) has been performed for the purification purposes. The operation has been performed at the atmospheric pressure with operating temperatures of 100°C and 25°C in physical processes (RE) and (LLE) respectively while in chemical derivatization it ranges from 72°C to 100°C. The characterization of the samples was accomplished by GCMS, FTIR and also its melting point was determined. Almost 99% of the purity was achieved by CD, LLE, RE followed LLE and LLE followed by RE.

Tellurites of Hexavalent Uranium: First Observation of Polymerized (UO4)2– Tetraoxido Cores

Two novel Ca2(UO3)(TeO3)2 (1) and K2(UO2)2O2(TeO3) (2) uranyl tellurites were obtained from telluric acid, used as a starting reagent for both compounds. In 1, the tetraoxido core is coordinated by TeO3 groups and UO4 squares polymerize into [UO3] chains. The tetraoxido core coordination modes in compound 1 are unique. New layered ⋡2[(UO2)2(TeO3)O2]2– topology is observed for 2. Both of the compounds were studied by the means of high‐temperature X‐ray diffraction. The thermal decomposition of 1 and 2 is different and leads to formation of uranate compounds.

Effect of telluric acid addition on thermal behavior of cesium dihydrogen phosphate

xCsH2PO4·(1-x)Te(OH)6 composites have been synthesized for the different compositions, x = 0.02, 0.04, 0.05, 0.06, 0.08 (labeled composites A-E). The composites were characterized by Scanning Electron Microscopy (SEM), XRay Diffraction (XRD), Thermogravimetry (TG) and Differential Thermal Analysis (DTA). Telluric acid, Te(OH)6, added to cesium dihydrogen phosphate (CsH2PO4) significantly effects the structure, particle size and thermal stability of the composite material. Enhanced thermal stability could lead to use of CsH2PO4 as an electrolyte in low temperature fuel cells.