Synthesized of Sporopollenin-Immobilized Schiff Bases and Their Vanadium(IV) Sorption Studies

This study investigated the potential use of a biologic polymer Lycopodium clavatum spores (Sporopollenin) for removal of vanadium ions (V(IV)) from aqueous solution. Three Schiff base derivative compounds immobilized sporopollenin were prepared and characterized. Immobilized sporopollenin was characterized via a scanning electron microscope, elemental analysis, infrared spectroscopy and thermal analysis techniques. The sorption capacities of the immobilized surfaces toward V(IV) ions were investigated by batch sorption experiments. V(IV) concentration, initial pH and the temperature effects were studied. The isotherm data of V(IV) ions were correlated reasonably well both Langmuir, Freundlich sorption isotherm. The thermodynamic studies showed that the V(IV) sorption onto immobilized sporopollenin derivatives is a spontaneous, endothermic and a chemical reaction.     

EPR of Vanadium(IV) in Lead Silicate Glass

EPR spectra of lead silicate glasses doped with small amounts of V₂O₅ were studied at −150°C to room temperature. Only the glasses with the higher SiO₂ contents produced EPR signals. The spin Hamiltonian parameters are characteristic of the V(IV) species in axial symmetry. The values of g, g ⊥, A, and B indicate that V(IV) is present as VO^2plus; in a tetragonally distorted octahedral site. This ion probably does not enter the SiO₂ network but rather behaves as a modifier cation.     

Spectroscopic and Thermal Studies on Pentaerythritol Tetranitrate (PETN)

Kinetics of the thermal decomposition of pentaerythritol tetranitrate (PETN) in condensed state has been investigated by high temperature infrared spectroscopy (IR) and thermogravimetry (TG) in conjunction with pyrolysis gas analysis, differential thermal analysis (DTA) and hot-stage microscopy. Kinetics of thermolysis has been followed by IR after suppressing volatilization by matrixing and by isothermal TG without suppressing volatilization to simulate actual user conditions. The best linearity was obtained for Avrami-Erofe'ev equation, n=1, in IR and isothermal TG. Activation energy was found to be 152 kJ mol⁻¹ and log A (in s⁻¹) 16.96 by IR. The effect of additives on the initial thermolysis of PETN has been studied. Evolved gas analysis by IR shows that NO₂, H₂CO are produced in the initial stage of decomposition followed by NO, N₂O, CO₂, HCN and H₂O. The decomposition in KBr matrix shows relative preferential loss in NO₂ band intensity which indicates that the rupture of O−NO₂ bond is the primary step in the thermolysis of PETN.     

Preparation of SnO2 Nanoparticles from a New Tin(IV) Complex: Spectroscopic and Photoluminescence Studies

A new dimethyltin(IV) complex, {[Me₂Sn(O₂CNC₉H₆)]₂O}₂ (1), was prepared by reaction of dimethyltin(IV) dichloride with the quinoline-2-carboxylic acid and characterized by elemental analysis, IR, ¹H-, ¹³C-, ¹¹⁹Sn-NMR spectroscopes. The structure of 1 was determined by single-crystal X-ray diffraction. The results showed that 1 is a tetranuclear, centrosymmetric dimeric, and contains two endo-cyclic five-coordinated and two exo-cyclic six-coordinated tin atoms and a N-atom of the 2-quinaldic carboxylate ligand coordinated to exo-cyclic tin. Complex 1 was utilized as a precursor for SnO₂ nanoparticles by direct thermal decomposition at 500 °C in air. The nano-structure of SnO₂ was characterized by scanning electron microscopy and X-ray powder diffraction. The SnO₂ core showed a band gap of ~4 eV determined from the UV/visible absorption spectrum. The SnO₂ nanoparticles show stable photoluminescence (PL) with an emission centered at 557 nm.     

Studies on the fungicidal properties of some triphenyltin(IV) compounds

The results are reported for an investigation into the fungicidal properties of six triphenyltin(IV) compounds representing metal coordination numbers of four through six. These experiments were conducted against a number of soil and plant pathogenic fungi and compared with the results obtained from triphenyltin chloride. While all the compounds examined proved to be effective fungicides, differences at the concentration levels tested were not sufficiently pronounced to relate the degree of toxicity to the molecular structure.     

Liquid Emulsion Membrane (LEM) Process for Vanadium (IV) Enrichment: Process Intensification

Abstract

A liquid emulsion membrane (LEM) system for vanadium (IV) transport has been designed using di‐2‐ethylhexyl phosphoric acid (D2EHPA), dissolved in n‐dodecane as carrier. The selection of extractant, D2EHPA, was made on the basis of conventional liquid‐liquid extraction studies. The work has been undertaken by first carrying out liquid‐liquid extraction studies for vanadium (IV) to get stoichiometric constant (n), and equilibrium constant (K_ex), which are important for process design.

Transport experiments were carried out at low vanadium (IV) concentration (ppm level). The studies on liquid emulsion membrane included i) the influence of process parameters i.e. feed phase pH, speed of agitation, treat ratio, residence time and ii) emulsion preparation study i.e., organic solvent, extractant concentration, surfactant concentration, internal strip phase concentration. When the strip phase concentration was 2 mol/dm³ (H₂SO₄) and feed phase pH 3 better extraction of vanadium was obtained. Higher V_m/V₁ gave higher extraction of vanadium (IV). A simplified, design engineer friendly model was developed.     

Localization and Spectroscopic Analysis of the Cu(I) Binding Site in Wheat Metallothionein Ec-1

The early cysteine-labeled metallothionein (MT) from Triticum aestivum (common wheat), denoted E_c-1, features two structurally well-defined domains, γ and β_E, coordinating two and four Zn(II) ions, respectively. While the protein is currently assumed to function mainly in zinc homeostasis, a low amount of copper ions was also recently detected in a native E_c-1 sample. To evaluate the observed copper binding in more detail, the recombinant Zn₆E_c-1 form was exposed to different amounts of Cu(I) ions and the resulting species characterized with spectroscopic methods. Data reveal that the first Cu(I) equivalent coordinates exclusively to the N-terminal γ-domain of the protein and replaces one Zn(II) ion. To analyze the ability of the γ-domain for coordination of monovalent metal ions in more detail, the γ-E_c-1 peptide fragment was incubated with increasing amounts of Cu(I) and the process monitored with UV–VIS, circular dichroism, and luminescence spectroscopy. Closely similar spectra are observed regardless if the apo- or the metal ion-loaded and, hence, pre-folded forms, were used for the titration experiments with Cu(I). The results indicate that low amounts of Cu(I) ions displace the two metal ions subsequently and stoichiometrically, despite the different coordination geometry requirements of Cu(I) and Zn(II).     

X-Ray Diffraction,Thermal and Spectroscopic Studies on 2,4-Dinitrodiphenylamine (DNDPA)

2,4-Dinitrodiphenylamine (DNDPA) has been studied as regards its crystal structure and thermal decomposition characteristics using X-ray diffraction (XRD), simultaneous thermal analysis, ultraviolet and visible spectroscopy, infrared spectroscopy, hot-stage microscopy and high performance liquid chromatography (HPLC). The elementary cell parameters obtained from the XRD pattern are a=17.002 Å, b=17.002 Å, c=20.400 Å. The crystal structure belongs to the hexagonal system with c/a ratio 1.1999. IR spectra of 2,4-DNDPA have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal thermogravimetry (TG) and HPLC. The best linearity with a correlation coefficient of 0.994 was obtained for the two-dimensional diffusion controlled equation in TG. Activation energy was found to be 83.0 kJ/mol and log A (in s⁻¹)=6.0 from isothermal TG. The rupture of the C NH bond followed by the C NO₂ bond constitutes the primary step in the thermolysis and the decomposition is free-radical assisted.     

Studies on chemically precipitated Mn(IV) oxides—I

Divalent manganesse salts are oxidised by alkali metal chlorates under various reactions conditions. The oxides so obtained are characterised by chemical analysis, X-ray and infra-red studies. The structure of the dioxides thus precipitated is found to be greatly influenced by the quantities of the reactants used, mode of precipitation, nature of the manganous salt and the type of chlorate. While the sulphates tend to produce α-MnO₂, the so-called γ-variety is readily obtained when the chloride salt is used. Its formation is apparently facilitated by the presence of Na⁺ ions. It is however, also precipitated in the presence of K⁺ ions under certain specific conditions. The chemical reactivity of the above dioxides is studied in this work and an attempt made to correlate it with the changes in the crystal structure. A comparison of the results obtained from the above studies with the results of I.C. MnO₂ samples reveals that the samples prepared in this laboratory show promise as active cathode materials in dry cells.     

Studies on chemically precipitated Mn(IV) oxides—II

The discharge characteristics of manganese dioxides prepared by chlorate oxidation of Mn(II) salts [Electrochim. Acta28, 309 (1983)] have been evaluated in 9 M KOH solution. The results would seem to indicate that some of the manganese dioxides prepared in this work have a comparatively better discharge performance than the I.C. MnO₂ samples in alkaline electrolyte.     

工艺因素对钒锆蓝颜料呈色的影响

探讨了工艺因素对钒－硅酸锆蓝色颜料合成的影响,用XRD和UV－V光谱对样品进行了表征,得到一些有益的结论。     

pH-Metric Studies on the interaction of oxovanadium (IV) with iminodiacetic (IMDA) and nitrilotriacetic (NTA) acids

Solution equilibrium studies on the interaction of oxovanadium (IV) with iminodiacetic (IMDA) and nitrilotriacetic (NTA) acids have been carried out. pH-Titrations of the reaction mixtures containing vanadyl sulphate and aminopolycarboxylic acid in equimolar ratio have shown the formation of 1:1 chelates. With IMDA, the possibility of 1:2 chelate (metal ion: IMDA) is also indicated. The equilibrium, chelate formation, hydrolysis and polymerization constants have been calculated at 25 and 30°C and also the thermodynamic functions viz. ΔH, ΔF, and ΔS.     

光谱法研究邻菲罗啉锌与DNA的相互作用

在模拟人体生理条件下(pH 7.4),运用荧光光谱和紫外可见吸收光谱研究了邻菲罗啉锌(Zn(phen)2+3)与小牛胸腺DNA(ctDNA)之间的相互作用。研究结果显示,ctDNA对Zn(phen)2+3的荧光猝灭机制属于静态猝灭。根据修正的Stern-Vomer方程计算了不同温度下的结合常数,并结合Van′t Hoff方程计算出相应的热力学参数,焓变值(ΔH=-7.029kJ/mol)和熵变值(ΔS=50.631J/(mol·K)表明静电作用力是维持Zn(phen)2+3-ctDNA复合物稳定的主要作用力。此外离子强度实验和KI荧光猝灭实验也证实了Zn(phen)2+3与ctDNA间通过静电作用的方式结合,而不是沟槽作用和嵌插作用。     

Extraction and Separation Studies of Tin(IV) with Tri-n-octylamine

Abstract

A selective method is developed for the separation of tin(IV) from copper, manganese, zinc, cadmium, mercury, nickel, lead, aluminum, bismuth, and molybdenum with tri-n-octylamine either from hydrochloric or acetic acid media. The metal ion from the organic phase is stripped with nitric acid solution and determined photometrically in the aqueous phase. The method is shown to be applicable to synthetic mixtures.     

Formation of Zircon from Zirconium Dioxide and Silicon Dioxide in the Presence of Vanadium Pentoxide

The high-temperature formation of zircon from zirconium dioxide and silicon dioxide in the presence of vanadium pentoxide was studied. A reaction between zirconium dioxide and vanadium pentoxide appeared to take place at about 730°C. That reaction product then reacted with silicon dioxide to form zircon. The experiments suggest that such zircon contains a few per cent of tetravalent vanadium in solid solution and has a light blue color. It appeared that the end product under equilibrium conditions would be pure zirconium silicate since vanadium pentoxide or tetroxide was liberated under prolonged heating. Zircon also formed from silicon dioxide and zirconium dioxide in the presence of niobium or tantalum pentoxide.     

水热法合成钒钼磷系列多金属氧酸盐

较系统地论述了目前国内外已见报道的采用水热法合成技术制备钒钼磷系列多金属氧酸盐(以下简称VMoPO)的研究现状，归纳了各VMoPO的水热法合成条件，并从反应温度及反应物种等方面初步总结了几点合成规律；概述了VMoPO的组成中抗衡阳离子的种类—4种简单的有机含氮物和两种碱金属阳离子；根据各VMoPO中多阴离子的空间结构特点对其作了分类和较细致的结构描述，并展望了今后水热法合成VMoPO研究工作的主要内容和发展方向。     

Photopyroelectric Spectroscopic Studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) Ceramics

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.     

Studies on a new heteropolyacid-based inorganic ion exchanger; zirconium(IV) selenomolybdate

A new heteropolyacid-based cation exchanger zirconium(IV) selenomolybdate has been synthesized, characterized using I.R., X-ray, TGA, DTA techniques. Its composition was found to be Zr:Se:Mo::2.5:0.7:1.6 and it is quite chemically stable. It exhibits 0.94 meq/g ion-exchange capacity for Na⁺ ions. Its distribution behavior for 16 metal ions has been studied and its utility has been employed by achieving separations Zn²⁺–Cd²⁺, Zn²⁺–Co²⁺, Ni²⁺–Cd²⁺and Ni²⁺–Co²⁺ on its column.