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Abstract  

The adsorption behavior of 47 metal ions on DEAE-cellulose (Cl) has been surveyed in aqueous thiosulfate solution by thin-layer chromatographic technique. The Rf values are measured as a function of thiosulfate concentration (0.010–2.0M) and are compared with those obtained on a microcrystalline cellulose Avicel SF. Generally, the ion-exchange adsorption of metal ions are weak or moderate over the thiosulfate concentration range tested except for a few metal ions like Mo(VI), Sb(III), Bi(III) etc., which have high preference to DEAE-cellulose. A variety of chromatographic distribution exhibited by metal ions allows to develop a number of separations of analytical and radiochemical interest.

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Abstract  

Thermal decomposition of a mixed valence copper salt, Na4[Cu(NH3)4][Cu(S2O3)2]2·0.5NH3 (1) prepared from pentahydrates of sodium thiosulfate and copper sulphate of various molar ratios in 1:1 v/v aqueous ammonia solution, has been studied up to 1,000 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR), in comparison. Compound 1 releases first but very slowly some of the included ammonia till 170 °C, then simultaneously ammonia (NH3) and sulphur dioxide (SO2) from 175 to 225 °C, whilst the evolution of SO2 from thiosulfate ligands continues in several overlapping stages until 410 °C, and is escorted by explicit exothermic heat effects at around 237, 260, 358 and 410 °C. The former two exothermic DTA-peaks correspond to the simultaneous degradation and air oxidation processes of excess thiosulfate anions not reacted by formation of copper sulfides (both digenite, Cu1.8S and covellite, CuS, checked by XRD) and sodium sulfate, while the last two exothermic peaks are accompanied also by considerable mass gains, as the result of two-step oxidation of copper sulfides into various oxosulfates. The mass increase continues further on until 580 °C, when the sample mass begins to decrease slowly, as a continuous decomposition of the intermediate copper oxosulfates, indicated also by re-evolution of SO2. At 1,000 °C, a residual mass value of 64.3% represents a stoichiometric formation of CuIIO and anhydrous Na2SO4.

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Abstract  

Solvent extraction of Cu(II) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiosulfate ions has been studied at room temperature (23±2°C). Mineral acid solutions alone constitute an aqueous phase from which Cu(II) is not extracted. Addition of small amounts of thiosulfate ions augments the extraction to an extent that quantitative recovery is possible. Stoichiometric studies reveal the involvement of ion-pair type complexes (NPy·H)2·Cu(S2O3)2 which are responsible for extraction. Stability constants lg Kex for this complex are 7.2±0.2; 9.1±0.2 and 9.5±0.2 for HCl, HNO3 and H2SO4, respectively. The presence of 0.01 mol/l of some complexing ions like ascorbate, acetate, citrate, oxalate, tartrate or iodide does not affect the extraction, thus allowing the recovery of the metal from diverse matrices. Under optimal conditions (0.1M NPy in benzene-0.1M HNO3 or H2SO4+0.01M S2O 3 −2 or 0.5M HCl+0.05 M S2O 3 −2 ) a clean separation from some elements, e.g. Cs(I). Co(II), Fe(III), Eu(III), Ce(III), Se(IV) and Cr(VI) can be achieved.

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Abstract  

Thermal behaviour of CuS (covellite) obtained from the Cu(CH3COO)2·H2O and Na2S2O3·5H2O system, working at different molar ratio (1:6 and 1:4) in presence/absence of NH4VO3, was studied. It was established that the presence of vanadium in the system induces a densification of CuS nodules, but do not change the hexagonal CuS structure. It has an important influence in thermal behaviour of copper sulfide CuS obtained also. The morphological characteristics of CuS play an important role in the thermal stability and the stoichiometry of the thermal decompositions. Also, the possibility to obtain copper sulfides with greater cooper content was investigated.

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cephalosporin antibiotics, using stress agents such as hydrogen peroxide at different concentrations (0.1 and 0.3%), sodium thiosulfate, potassium permanganate, iodine solution, and ascorbic acid. In previous researches, we elaborated also simple and rapid TLC

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Abstract  

The isotopic exchange of35S between thiosulfate/sulfite and tetrathionate/thiosulfate is examined. The kinetic data are determined. In both cases the reactions are of second order. As the isotopic exchange between tetrathionate/thiosulfate is very fast, these reaction components are used in high dilution. Furthermore, the extent of exchange during the separation is determined.

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Abstract  

Thermal analysis has been performed of xerogels obtained by encapsulation of sodium thiosulfate (systems I and II), glycerol with I2/KI (system III) and urea with I2/KI (system IV) in silica gel. DTA, TG and DTG of the xerogels with thiosulfate differed markedly depending on the thiosulfate content. At the 22% thiosulfate content in the original silicic acid solution used for the preparation of the xerogel, a single exothermic peak appears in the DTA trace assignable to the combustion of elemental sulfur derived either from the reaction between silicic acid and the thiosulfate or from the thermal degradation of the latter. When the thiosulfate content in the original solution is raised up to 60%, the peak is split into two symmetrical components, one (at 553 K) attributable to combustion of the more finely dispersed sulfur and the other (at 703 K) to sulfur particles of coarser morphology. The former is likely to be formed by chemical interaction of the components of original solution and the latter is due to thermal degradation of residual thiosulfate. The main features of a DTA, TG and DTG obtained from xerogel III are exothermic events recorded in the DTA trace suggesting that after the loss of iodine, thermal degradation of glycerol takes place with the onset at 523 K leaving a combustible solid. Under these conditions, glycerol alone distilled out with no evidence for degradation. A derivatogram of xerogel IV is characterized by initial sublimation/evaporation of urea and iodine followed by partial condensation of urea to afford biuret and eventually cyanuric acid.

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Abstract  

The adsorption of mercury on zirconium oxide from aqueous solution has been studied in relation to concentration of adsorbent and adsorbate. The influence of contact time, buffer composition, pH, and foreign ions was also investigated. Thiosulfate, iodide, thiocyanate, EDTA, cyanide and Li(I) drastically reduced adsorption. Adsorption of other metal ions under the same conditions was also investigated. Based on these data, separation of mercury from antimony and neodymium can be achieved.

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