Metal chelates as flame retardants and smoke suppressants for thermoplastic polymers

Metal chelates have been incorporated into polystyrene and polypropylene to study their effects on the combustion of these polymers, in the absence and presence of a chlorinated hydrocarbon. In particular, the effect of ferrocene on the flammability of the polypropylene-Cereclor 70 system has been studied comprehensively by a triangular diagram method. The additives have been shown to interact synergistically to increase char and thus produce a system of low flammability; the Cl/Fe ratio needed for optimum flame retardance is considerably higher than stoichiometric. It has been found that, if the presence of the chlorine compound decreases the amount of smoke produced from a polymer-metal chelate system, this is indicative of some degree of flame-retardant activity of the metal-halogen system.     

LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Kinetics and mechanism of solid-state reaction between bismuth(III) oxide and molybdenum(VI) oxide

The mechanism of the following solid-state reactions between bismuth(III) oxide and molybdenum(VI) oxide was investigated within the temperature range 400–650°C.

$\text{(i)}\text{Bi}{}_2\text{O}{}_3\text{+ MoO}{}_3\text{→ Bi}{}_2\text{MoO}{}_6\text{, (ii)}\text{Bi}{}_2\text{O}{}_3\text{+ 2MoO}{}_3\text{→ Bi}{}_2\text{MO}{}_2\text{O}{}_9\text{, (iii)}\text{Bi}{}_2\text{O}{}_3\text{+ 3MoO}{}_3\text{→ Bi}{}_2\text{(MOO}{}_4\text{)}{}_3\text{, (iv)}\text{Bi}{}_2\text{MoO}{}_6\text{+ MoO}{}_3\text{→ Bi}{}_2\text{MO}{}_2\text{O}{}_9\text{, (v)}\text{Bi}{}_2\text{Mo}{}_2\text{O}{}_9\text{+ MoO}{}_3\text{→ Bi}{}_2\text{(MoO}{}_{\mathrm{2)3}}\text{.}$

Two types of experiments, capillary and particle size, were performed to ascertain whether MoO₃ diffuses into Bi₂O₃ or vice versa. These show that molybdenum trioxide diffuses into bismuth oxide grains. If α is the fraction of molybdenum trioxide reacted, the kinetics in all five cases are found to be governed by the equation αⁿ = kt throughout the temperature range, where n and k are constants at a given temperature and t is the time. Both n and k are temperature dependent. The characteristic feature of these reactions is that they proceed to completion. Results are also fitted by the relation $\text{α = k}{}_2\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? k}{}_3\text{t}$, where k₂ and k₃ are constants, which shows that the reactions occur by bulk diffusion through grain boundary contacts. The number of grain boundary contact points decreases with time in the course of reaction.     

Binary mixtures of metal compounds as flame retardants for organic polymers

Studies have been made of the effect on the flammability of thermoplastic polymers of the partial or total replacement of one metal compound by another in the presence also of a suitable halogen compound; particular attention has been paid to systems where the primary flame retardant is antimony(III) oxide. With each binary metal compound system investigated, ten different compositions have been chosen so as to provide a symmetrical arrangement of points within a triangular design; resulting calculated values of the limiting oxygen index for each polymer-flame retardant system for a given polymer are shown as a graphical contour analysis. Comprehensive studies of several systems show that both iron(III) oxide and aluminium oxide monohydrate can significantly enhance the flame-retardant action of antimony(III) oxide but that several other metal compounds, although not as effective as Sb₂O₃, may nevertheless be used as adequate partial replacements for it. The Fe₂O₃-SnO₂-H₂O system can also act as an effective flame retardant under certain conditions. The SnOZnO system perhaps best illustrates the importance of the polymer substrate and of the total additive loading as factors controlling the flame-retardant effectiveness. For all the systems studied, however, ABS is a much better substrate than HDPE. The results of a reasonably detailed study of the flame retardance conferred by several different compositions of a binary metal compound mixture give a much more reliable indication of the effects on polymer flammability of the constituent metal compounds than are obtained simply by replacement of a given concentration of one compound by another.     

Extraction of molybdenum(VI) from fluoride niobium-tantalum solutions with a high content of titanium(IV)

Distribution of molybdenum(VI) (0.05 M) upon extraction with tributyl phosphate from fl uoride solutions with a content of titanium(IV), niobium(V), and tantalum(V) of up to 3.0, 0.7, and 0.7 M, respectively, was studied.     

Determination of metallic iron, iron(II) oxide, and iron(III) oxide in a mixture

A procedure is described for the estimation of metallic iron, ferrous oxide, and ferric oxide when present together. The sample is treated with bromine dissolved in ethanol, and filtered. Iron in the filtrate is titrated iodometrically, and corresponds to the metallic iron present in the mixture. The oxide residue is dissolved in hydrochloric acid under a carbon dioxide atmosphere. The iron(II) formed, equivalent to FeO present, is titrated with a standard vanadate solution, and the total iron(III) (FeO + Fe₂O₃) in the titrated solution is then estimated iodometrically.     

Simultaneous first-derivative spectrophotometric determination of iron(III) and molybdenum(VI) in cobalt-chromium and nickel-chromium alloys

A method is proposed for the simultaneous determination of iron(III) and molybdenum(VI) by first-derivative spectrophotometry based on the absorption spectra of their complexes with morin in the presence of a cationic surfactant. The zero-crossing measurement technique is found sutiable for the direct measurement of the first-derivative value at the specified wavelengths. Iron(III) (0.9-1.5 mug ml(-1)) and molybdenum(VI) (0.3-4.2 mug ml(-1)) in different ratios have been determined simultaneously. A critical evaluation of the proposed method is performed by statistical analysis of the experimental data. The method was applied to determine iron and molybdenum in different alloys.     

Modeling Speciation and Solubility in Aqueous Systems Containing U(IV,VI), Np(IV,V, VI), Pu(III,IV, V,VI), Am(III), and Cm(III)

A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been applied to calculate phase equilibria and chemical speciation in selected aqueous actinide systems. The solution chemistry of U(IV, VI), Np(IV, V, VI), Pu(III, IV, V, VI), Am(III), and Cm(III) has been analyzed to develop the parameters of the model. These parameters include the standard-state thermochemical properties of aqueous and solid actinide species as well as the ion interaction parameters that reflect the solution’s nonideality. The model reproduces the solubility behavior and accurately predicts the formation of competing solid phases as a function of pH (from 0 to 14 and higher), temperature (up to 573 K), partial pressure of CO₂ (up to \( p_{{{\text{CO}}_{2} }} \)  = 1 bar), and concentrations of acids (to 127 mol·kg^?1), bases (to 18 mol·kg^?1), carbonates (to 6 mol·kg^?1) and other ionic components (i.e., Na⁺, Ca²⁺, Mg²⁺, OH^?, Cl^?, \( {\text{ClO}}_{4}^{ - } \), and \( {\text{NO}}_{3}^{ - } \)). Redox effects on solubility and speciation have been incorporated into the model, as exemplified by the reductive and oxidative dissolution of Np(VI) and Pu(IV) solids, respectively. Thus, the model can be used to elucidate the phase and chemical equilibria for radionuclides in natural aquatic systems or in nuclear waste repository environments as a function of environmental conditions. Additionally, the model has been applied to systems relevant to nuclear fuel processing, in which nitric acid and nitrate salts of plutonium and uranium are present at high concentrations. The model reproduces speciation and solubility in the U(VI) + HNO₃ + H₂O and Pu(IV, VI) + HNO₃ + H₂O systems up to very high nitric acid concentrations (\( x_{{{\text{HNO}}_{3} }} \approx 0.70 \)). Furthermore, the similarities and differences in the solubility behavior of the actinides have been analyzed in terms of aqueous speciation.     

M?ssbauer spectroscopic studies of the interaction between iron(III) and molybdenum(VI) oxides

At 400°C an appreciable interaction between the title oxides is observed, resulting in iron molybdate formation

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400°C .

     

Characterization of iron(III) oxide and oxide-hydroxide as Sr-sorbent

Iron(III) hydroxide and oxide-hydroxide samples prepared by precipitation of 0.2M iron(III) nitrate solution by 5M NaOH and subsequently aged at pH 12 for times of up to 50 h have been characterized. The sorption properties towards Sr²⁺ were characterized by radiotracer method using⁸⁵Sr, morphology of the samples was characterized by Transmission Electron Microscopy and Emanation Thermal Analysis. X-ray diffraction patterns characterized the crystallinity of the samples aged for various times. The maximum (100%) sorption capacity for⁸⁵Sr corresponding to amorphous iron(III) hydroxide decreased to 75% with the time of precipitate ageing (up to 40 h). This finding corresponds to the development in crystallinity and morphology of the sorbent.     

Adsorption kinetics of fluoride on iron(III)-zirconium(IV) hybrid oxide

Fluoride occurs in some drinking water sources at levels that are hazardous to health. Tests were conducted to assess the ability of a mineral-based adsorbent to take-up fluoride ion. Consequently, in search of novel adsorbent media, crystalline and hydrous iron(III)-zirconium(IV) hybrid oxide (IZHO) was synthesized, and tested to determine its capacity and kinetics for fluoride adsorption. The Fourier Transform Infrared (FTIR) spectrum of IZHO indicated the presence of Fe–O–Zr linkage which showed hybrid nature of the synthetic oxide. The optimum pH range for fluoride adsorption was ranged between 4.0 and 7.0. The analyses of the isotherm equilibrium data using the Langmuir and the Redlich–Peterson model equations by linear and non-linear methods showed that the data fitted better with latter model than the former. Thermodynamic analysis showed spontaneous nature of fluoride adsorption, and that took place with the increase of entropy. The kinetic data obtained for fluoride adsorption on IZHO at pH 6.8 (±0.1) and room temperature (303±2 K) described both the pseudo-first order and the reversible first-order equations equally well (r ²= ∼0.98–0.99), and better than pseudo second order equation (r ²= ∼0.96–0.98) for higher concentrations (12.5 and 25.0 mg/dm³) of fluoride. The kinetics of fluoride adsorption on the mixed oxide took place with boundary layer diffusion. External mass transport with intra-particle diffusion phenomena governed the rate limiting process, which has been confirmed from the Boyd poor non-linear kinetic plots.     

Methylbutylmalonamide as an extractant for U(VI), Pu(IV) and Am(III)

We describe the operation of a Local Area Network at Nuclear Chemistry Laboratory involved in surveillance of environmental radioactivity. Detailed consideration is given separately to computer and network hardware, radiation instrument interfacing, software, as well as operations. The application of a Local Area Network offers considerable improvements in the laboratory preformance, quality assurance of radioactivity analyses, and data reporting.     

Photometric titration of titanium(III) with iron(III)

An oxidimetric titration of titanium(III) with iron(III) with a photometric end-point is proposed. Acetylacetone was used to obtain an intensely coloured titanium(III) complex; titanium(III) was formed by prereduction with chromium(II) or vanadium(II). Amounts of titanium down to 35 μg were determined with fairly good accuracy and precision. Few common elements interfere.     

Porosity of some iron(III), chromium(III), and zirconium(IV) hydroxide oxide xerogels

Porosity and density in water are studied for xerogels prepared by drying iron(III), chromium(III), and zirconium(IV) hydroxide oxide (HO) hydrogels. The hydrogels are either freshly precipitated at pH 7–11 or aged in sodium chloride or sodium sulfate solutions. The space distribution in the xerogels between the volume occupied by the constituent ions and the interstitial volume (spaces between metal-oxygen chains, mesopores, micropores, and macropores) is determined. The meso-and micropore volumes of the chromium(III) HO xerogels are two to four times the volumes of iron(III) and zirconium(IV) HO xerogels. We suggest that the microstructure of the chromium(III) HO hydrogels is almost fully inherited by their xerogels.     

Reactions of tungsten(VI) and molybdenum(V) chlorides,and tungsten(VI) and molybdenum(VI) oxychlorides,with azoxybenzene

Reactions of W^VI and Mo^V chlorides with azoxybenzene yield ionic species of W^VI and Mo^VI oxychlorides in which the cation is a protonated azobenzene. The reaction between MoCl₅ or MoOCl₄ and azoxybenzene gives, after extraction with methylene chloride—ethanol mixture, the complex [trans-MoOCl₄(OC₂H₅)]^? [C₁₂H₁₀N₂H]⁺. In contrast, WOCl₄ reacts with azoxybenzene to give a stable non-ionic adduct in which the organic moiety is coordinated through its oxygen atom trans to the WO bond. Several complexes of substituted azoxybenzene having similar structures are described.     

Mononuclear and homobinuclear vanadium(IV), chromium(III), molybdenum(III), and uranium(VI) chelates with ortho-cresolphthalein complexone

Mononuclear and homobinuclear o-cresolphthalein complexone complexes with VO²⁺, Cr³⁺, MoO⁺, and UO₂ ²⁺ have been prepared and their structures investigated. The empirical formulas, the mode of bonding, and the geometry of the complexes were obtained from elemental and thermal analyses, IR, electronic and ESR spectra, magnetic moment determinations, DC and CV polarographic studies.     

Kinetics,isotherm and thermodynamics for Cr(III) and Cr(VI) adsorption from aqueous solutions by crystalline hydrous titanium oxide

The synthetic crystalline hydrous titanium(IV) oxide (CHTO), an anatase variety and thermally stable up to 300 °C, has been used for adsorption of Cr(III) and Cr(VI) from the aqueous solutions, the optimum pH-values of which are 5.0 and 1.5, respectively. The kinetic data correspond very well to the pseudo-second order equation. The rates of adsorption are controlled by the film (boundary layer) diffusion, and increase with increasing temperature. The equilibrium data describe very well the Langmuir, Redlich–Peterson, and Toth isotherms. The monolayer adsorption capacities are high, and increased with increasing temperature. The evaluated ΔG^° (kJ · mol^?1) and ΔH^° (kJ · mol^?1) indicate the spontaneous and endothermic nature of the reactions. The adsorptions occur with increase in entropy (ΔS^° = positive), and the mean free energy (E_DR) values obtained by analysis of equilibrium data with Dubinin–Radushkevick equation indicate the ion-exchange mechanism for Cr(III) and Cr(VI)-adsorptions.