The removal of radioactive strontium ions from aqueous solutions by isotopic exchange using strontium decavanadates and corresponding mixed oxides


Ortaboy S. , Acar E. T. , Atun G.

CHEMICAL ENGINEERING JOURNAL, cilt.344, ss.194-205, 2018 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 344
  • Basım Tarihi: 2018
  • Doi Numarası: 10.1016/j.cej.2018.03.069
  • Dergi Adı: CHEMICAL ENGINEERING JOURNAL
  • Sayfa Sayıları: ss.194-205

Özet

Two types of strontium decavanadate samples (A and B) were synthesized conductometrically in different pH ranges of 6.7-5.6 and 4.2-3.5, respectively. The samples were used as isotope exchangers after heat treatment at 333, 378 and 573 K for the removal of Sr-90 radionuclide from the aqueous solution which is one of the most important fission products of uranium. The content of crystalline water in the exchangers was determined by thermo-gravimetric analysis (TGA). They were characterized using the X-ray diffraction (XRD), diffuse reflectance infrared Fourier-transforms (DRIFT) and the energy dispersive spectral (EDS) analysis. The SEM micrographs showed that sample A dried at 333 K has an urchin-like structure but it decomposes as annealed at 573 K. Sample B dried at 333 K is composed of quadrangular-prism like micro-rods but nano-sized platelets also formed at 573 K. The time-dependent studies conducted at three different molar ratios of strontium ions in the exchanger to the solution showed that Sr2+ ions completely exchanged at the ratio of 3.5 and 2.0 for the samples A and B annealed at 573 K, respectively. The kinetic data were analyzed using McKay, Nernst Planck, and Paterson's models and correlated to structural characteristics of the exchangers. The Sr-removal capacities of the exchangers evaluated by applying the Langmuir isotherm model increased with the annealing temperature. The results revealed that radioactive Sr2+ ions can be selectively removed by the exchangers annealed at 573 K from real wastewater because the exchange fractions are not significantly affected by the pH changes and the common coexisting cations.