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  • Author or Editor: J. Lehto x
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Abstract  

The ion exchange behaviour of the exchanger Na4Ti9O20.xH2O was studied with particular emphasis on Sr2+ exchange. Titration of H4Ti9O20.xH2O with 0.1M [Sr/OH/2+SrCl2] solution yielded a strontium ion exchange capacity of 5.30 meq g–1 corresponding well with the theoretical value. When strontium was absorbed on Na4Ti9O20.xH2O from neutral solutions, Sr2Ti9O20.xH2O was formed. This compound decomposed to SrTiO3 and TiO2 when heated to 870 °C. From alkaline solutions strontium was absorbed both as Sr/OH/+ and Sr2+ with the proportion of the former species increasing with pH. At pH 12.8 only exchange of Sr/OH/+ was observed and the exchanged form was Na2/SrOH/2Ti9O20.xH2O. This compound decomposed to Na2Ti6O13 and an unidentified strontium titanate when heated to 870 °C. Distribution coefficients were determined for alkali and alkaline earth metal ions as a function of pH. The selectivity sequence for alkaline earth metal ions was Ba>SrCa>Mg, and that for alkali metal ions was Cs>K>Li /pH 2–6/ and Li>Cs>K /pH 7/.

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Abstract  

Potassium cobalt hexacyanoferrate(II) was synthesized with a composition K1.70Co1.12Fe(CN)6 · 1H2O, a mixture of K2[CoFe(CN)6] (85–88%) and K2[CoFe(CN)6] (12–15%). Ion exchange was found to be stoichiometric, the exchangeable ions being potassium and cobalt in the ratios presented for the corresponding phases. The effective capacity for cesium was 0.35 meq/g, which is only 6% of the theoretical capacity. Cesium is probably only absorbed as a monolayer on the surface of the crystallites.

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Abstract  

An on-line method developed for separating plutonium and americium was developed. The method is based on the use of HPLC pump with three analytical chromatographic columns. Plutonium is reduced throughout the procedure to trivalent oxidation state, and is recovered in the various separation steps together with americium. Light lanthanides and trivalent actinides are separated with TEVA resin in thiocyanate/formic acid media. Trivalent plutonium and americium are pre-concentrated in a TCC-II cation-exchange column, after which the separation is performed in CS5A ion chromatography column by using two different eluents. Pu(III) is eluted with a dipicolinic acid eluent, and Am(III) with oxalic acid eluent. Radiochemical and chemical purity of the eluted plutonium and americium fractions were ensured with alpha-spectrometry.

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Abstract  

The distribution coefficients for alkali and alkaline earth metal ions on potassium cobalt hexacyanoferrate (II), K2CoFe(CN)6×1.4H2O, show high selectivity for cesium. The uptake values of the ions vary widely. The uptake is most probably an ion exchange process.

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Abstract  

A well-known photolabile substance, nifedipine, was used as a sample material to test self-constructed irradiation cells and demonstrate their usefulness in photostability studies. The devices were made as accessories for a commercial isothermal microcalorimeter. Several powder samples containing various amounts of moisture were irradiated with monochromatic light as a scan measurement from 700 to 280 nm, and the heat flow evolved in the photodegradation of nifedipine was determined. According to the results, light does not affect the nifedipine molecule directly, but the photodegradation is a result of the combined effects of moisture and light.

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Summary Thermally carbonised mesoporous silicon microparticles were produced and loaded with two active pharmaceutical ingredients, ibuprofen and antipyrine. By combining the results measured with TG and DSC, reliable estimations for the degrees of the drug loads were obtained. To distinguish the drug adsorbed on the surfaces of the microparticles from that absorbed into the pores, the principle of thermoporometry on the DSC measurements was employed. According to the principle, the drug held in the capillaries of porous material has a depressed melting temperature because of the higher pressure of the drug in cavities with a curved interface. On the other hand, the drug located on the external surface of the microparticles exhibits the normal melting of bulk drug. The loading degrees obtained with the thermoanalytical methods (31 and 26 mass& for ibuprofen and antipyrine, respectively) were comparable with the results obtained with helium pycnometry (the corresponding values were 33 and 28 mass&). Nitrogen sorption studies were not reliable for quantitative determinations due to the inability of nitrogen to penetrate in all pores, which might be blocked by the drug on the surface of the microparticles.

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Abstract  

Advanced separation methods of harmful metals from industrial waste effluents, i.e., radionuclides from nuclear waste solutions, transition metals from metallurgical waste effluents, developed at the Laboratory of Radiochemistry, are discussed.

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