Separation of cobalt, neodymium and dysprosium using amorphous zirconium phosphate

Abstract

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 31 P 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.

Modification of α‐Zirconium Phosphate Synthesis – Effects of Crystallinity and Acidity on Eu(III) and Am(III) Ion Exchange

“…Crystalline and acid character of a product then dictates its ion exchange properties and applicability for separation use. While the time can be increased further or other methods can be used to get more crystalline product, our findings here support our previous studies,, in that a too highly crystalline product will have less favourable ion exchange properties in low pH. This highlights that the most readily available ion exchange sites exist on surfaces, edges and in crystal defect sites.…”

“…This is slightly more than what is reported for crystalline α‐ZRP, 6.6 meq/g,,, a value that can be rationalized theoretically from the chemical formula. We suggest that this slight increase is due to the partly amorphous nature of the products, which can increase the capacity as discussed in earlier study …”

Column Separation of Am(III) and Eu(III) by α-Zirconium Phosphate Ion Exchanger in Nitric Acid

“…Previously we have proven stability of α-zirconium phosphate for both highly crystalline [21] and highly amorphous [22] material for similar metals: no lowering of the K d for Nd(III) nor Dy(III) were shown during the full duration of the kinetics experiment (three days). In those experiments the analyte concentrations were always 1 mmol•L −1 , instead of trace levels used here, and also there was no Na present.…”

“…During the experiment, a total of 0.10 mmol•g −1 of Eu(III) was taken up by the exchanger; or 0.30 meq•g −1 . Theoretical capacity of crystalline α-zirconium phosphate is 6.6 meq•g −1 [23] whereas amorphous zirconium phosphate can exceed this [18,22]. For the semi-crystalline zirconium phosphate batch used throughout the text, the experimental total capacity by titration has been earlier determined to What is left to account for the decrease in Am uptake, is the slow kinetics of the major cation present: Na.…”

Selective ion-exchange separation of scandium(III) over iron(III) by crystalline α-zirconium phosphate platelets under acidic conditions

“…The characterisations of am-ZrP, am-TiP and α-TiP were reported in our previous studies [27,48]. Moreover, the synthesised α-ZrP platelets have been extensively studied and characterised in the literature [49,50].…”