Papers by Author: A. Deptuła

Abstract: Nanocomposites (nanocrystals) of KY(WO4)2 and KY(WO4)2+1% mol Yb were synthesized using a Complex Sol-Gel Process (CSGP). A chemical treatment with concentrated nitric acid and hydrogen peroxide was used to reduce the decarbonisation temperature. The expected monoclinic phase C2/c of the KYW of the nanocomposite powder was confirmed using XDR. From the X-ray diffraction measurements, the unit cell parameters and the size of nanoparticles was determined. Electron spin resonance studies in the X band were carried out on KYW and KYW:Yb nanocrystals. The sintered samples were made with using the high pressure technique at temperatures up to 600oC. In addition chemical analysis, X-ray diffraction measurements and ESR investigations were carried out on the sintered samples.

Abstract: Hydroxyapatite (HA) microspheres of diameter <70 μm have been synthesized by solgel processing. The starting sols were prepared by ultrasonic mixing of concentrated solutions of calcium acetate (1.7M) with 85% H3PO4, followed by emulsification in dehydrated 2-ethyl-1- hexanol. Drops of emulsion were solidified by extraction of water with this solvent. The final thermal treatment was a 2 h soaking in air at 900°C. Properties such as hydraulic resistance and sedimentation rate, which are important for application in ion-exchangers, were superior for our prepared microspheres in comparison with irregularly shaped commercial HA. Adsorption of the following metals was investigated: U, Zn, Fe, Cu, Ni, Co, Cd, Pb, Mn, Al, Cr, As, Sb, Bi and Mo. Retention was ≈100% for of all the metals studied when pH > 3–4. On average, ≈1/20 moles of metal reacted with 1 mole of HA. Adsorbed metals could be desorbed with efficiencies of 60–90%. In addition, nuclear-waste-saturated beds of HA could be transformed to insoluble ceramics by thermal treatment. The cost of producing HA microspheres was estimated to be comparable to current prices of irregularly shaped commercial hydroxyapatite powders. For radioactive contaminants such as U, for which resorption need not be considered, porous monoliths were produced by use of industrial reagents. The retention capacity was determined to be 30 mg of U per 1 mg of monolith.