Browsing by Subject "Ion exchange"

Sort by: Order: Results:

Now showing items 1-4 of 4
  • Wiikinkoski, Elmo W.; Xu, Junhua; Zhang, Wenzhong; Hietala, Sami; Koivula, Risto T. (2018)
    The aim of an ongoing study is to develop ion exchange materials to be used in low pH in mineral acids for the uptake and separation of trivalent lanthanides and actinides. We present material development of alpha-zirconium phosphate (ZrP), namely the effects of its crystallinity and acidity on other material properties and on Eu(III) and Am(III) trace ion exchange. One-pot synthesis for three ZrP products having a time for (re)crystallization of 1 hour, 5 hours and 25 hours, is reported. Characterization techniques include X-ray diffraction, solid-state nuclear magnetic resonance, infrared spectroscopy, thermal analysis, electron microscopy, pK(a1) determination, and Eu-152(III) and Am-241(III) ion exchange studies, i.e. distribution-, selectivity- and metal binding coefficient determinations. As crystallinity and crystallite size increase, so do Eu(III) and Am(III) metal binding coefficients. The acidity and Eu(III) and Am(III) distribution- and selectivity coefficients increase in the reverse order. Findings are discussed with separation in mind. Promising separation factors (Eu:Am) of up to 90 were achieved in pH less than 1 in nitric acid.
  • 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.
  • Xu, Junhua; Koivula, Risto Tapio; Zhang, Wenzhong; Wiikinkoski, Elmo Werneri; Hietala, Sami; Harjula, Risto Olavi (2018)
    The purpose of this study was to investigate the separation of Co, Nd and Dy from a ternary Co-Nd-Dy solution using amorphous zirconium phosphate (am-ZrP). Am-ZrP was synthesized by a precipitation method at room temperature and subsequently characterized by Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, X-ray diffraction, solid-state 31P magic angle spinning nuclear magnetic resonance spectrometry and sodium hydroxide titration (with and without background salt). The ion exchange kinetics of am-ZrP that were determined in ternary 1 mM equimolar solutions at equilibrium pH 2.5. The effect of pH on the adsorption was studied in ternary 1 mM equimolar solutions and the uptakes of the metals increased with increasing pH until approximately pH 3.5. The adsorption isotherms of Co, Nd and Dy were tested in a series of ternary equimolar solution, the total uptake amounted to 4.13 meq/g at pH ~ 3.0. The preference of am-ZrP for these metals occurred in decreasing order Dy > Nd ≫ Co. The separation of Co, Nd and Dy from their 1 mM equimolar ternary mixture was investigated on an am-ZrP column. Effects of loading (7.8%, 62% and 100%) on the separation were compared by measuring the corresponding HNO3 elution fractions. It was found that with a lower metal loading of 7.8%, three clear elution bands were obtained. Am-ZrP exhibited selective separation properties towards the ternary Co-Nd-Dy system, which contribute to the future scale-up studies for the recycling of NdFeB magnets.
  • Dyer, Alan; Hriljac, Joe; Evans, Nick; Stokes, Ian; Rand, Peter; Kellet, Simon; Harjula, Risto; Moller, Teresia; Maher, Zoe; Heatlie-Branson, Ross; Austin, Jonathan; Williamson-Owens, Scott; Higgins-Bos, Manon; Smith, Kurt; O'Brien, Luke; Smith, Nick; Bryan, Nick (2018)
    Mud Hills clinoptilolite has been used in an effluent treatment plant (SIXEP) at the Sellafield nuclear reprocessing site. This material has been used to remove Cs-134/137 and Sr-90 successfully from effluents for 3 decades. Samples of the zeolite have been tested in column experiments to determine their ability to remove radioactive Cs+ and Sr2+ ions under increasing concentrations of competing ions, Ca2+, Mg2+, Na+ and K+. These ions caused increased elution of Cs+ and Sr2+. Ca2+, Mg2+ and K+ were more effective competitors than Na+. For Na+, it was found that if concentration was reduced, then column performance recovered rapidly.