Browsing by Subject "ION-EXCHANGE"

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  • Aromaa, H.; Helariutta, K.; Ikonen, J.; Yli-Kaila, M.; Koskinen, L.; Siitari-Kauppi, M. (2018)
    A method for analyzing H-3, Cl-36, Na-22, Ba-133 and Cs-134 from simulated groundwater (SGW) samples was introduced. Gamma emitting radionuclides Na-22, Ba-133 and Cs-134 were measured by using an HPGe-detector. Beta emitting H-3 and Cl-36 were separated from gamma emitting Na-22, Ba-133 and Cs-134. AgCl precipitation was used for the separation of Cl-36 from SGW samples with yields of 98 +/- 2%. H-3 was separated by distillation with recoveries of 97 +/- 3%. This method was used for the determination of activity concentrations of H-3, Cl-36, Na-22, Ba-133 and Cs-134 in SGW samples collected from an in situ through diffusion experiment.
  • Puhakka, Eini; Ritala, Mikko; Lehto, Jukka (2020)
    Potassium cobalt hexacyanoferrate(II) [K2CoFe(CN)(6)] is an extremely selective ion exchanger for cesium ions. To examine the atomic level background for the selectivity a computational structural study using DFT modelling was carried out for K2CoFe(CN)(6) and for products where Cs has replaced K in the elemental cube cages closest to the surface. In the K-form compound the potassium ions are not in the center of the Co-Fe-CN elementary cube cages closest to the surface but locate about 140 pm from the cube center towards the surface. When cesium ions are exchanged to these potassium ions they locate much deeper from the surface, being only about 70 pm upwards from the cube center. 'Ibis apparently leads to much stronger bonding of cesium compared to potassium. Once taken up into the outermost cube cages on the surface of the crystallites cesium ions are not able to penetrate further since they are much larger than the electron window between the cubes. Furthermore, they are not able to return to the solution phase either leading to a practically irreversible sorption.
  • Xu, Junhua; Virolainen, Sami; Zhang, Wenzhong; Kuva, Jukka; Sainio, Tuomo; Koivula, Risto (2018)
    Recycled Nd and Dy from the end-of-life NdFeB permanent magnet is an important supplement for the increasing demand of rare-earth elements. Thus, there is an urgent need to develop an environmentally friendly recycling method. Amorphous zirconium phosphate exhibits selective separation properties towards the ternary Co-Nd-Dy system, however, its powdery form limits development of scaled-up applications. We present an efficient amorphous ZrP/Polyacrylonitrile (am-ZrP/PAN) composite ion exchanger for uptake and separation of Nd, Dy and Co. The am-ZrP/PAN composite was synthesized and its structural, morphologic and acidic properties were investigated by various methods. X-ray tomography revealed rather evenly distributed am-ZrP in the PAN polymer matrix. The selectivity and ion-exchange kinetics of the am-ZrP/PAN composite were determined in relation to the individual elements. Due to dimethylformide (DMF) intercalation into the interlayer of ZrP, the uptake of Co, Nd and Dy increased 50% compared with that of the pristine am-ZrP. Column separation of Co, Nd and Dy from the Co-Nd-Dy ternary system was assessed by varying the feed concentration, loading degree, temperature, running speed and elution agent (HNO3) concentration. Finally, gradient elution was employed for Co, Nd and Dy separation from a simulated ternary leachate. Fractions with 87.9% pure Co, 96.4% pure Nd and 40% pure Dy were collected through a single-column operation.