Bauxite residue (BR) is an inevitable industrial waste generated through the classic Bayer extraction of alumina from bauxite minerals. It contains relatively significant amount of valuable rare earth elements, including scandium, and therefore we explored the suitability of trace scandium recovery from BR acid leachate by titanium phosphate (TiP) ion exchangers. Three kinds of TiP materials (amorphous TiP, α-TiP and γ-TiP) were synthesized through fluorine-free precursors and characterized by chemical analysis, XRD, FE-SEM, FTIR, UV/Vis diffuse reflectance spectrometry, 31 P MAS NMR, TGA and potentiometric titration. The Sc 3+ exchange capacities were determined as 1.74, 0.55 and 0.22 meq g -1 for amorphous, α-and γ-TiP, respectively. Competition of major elements (Fe, Al, Ca) in BR leachate with Sc uptake was studied in batch experiments using binary equimolar mixtures, and the separation factors of Sc/Fe 2+ , Sc/Al and Sc/Ca reach the magnitudes of 10 to 1000 on amorphous TiP. 2 The high Sc 3+ selectivity by amorphous TiP was suspected to be the matching of Ti 4+ lattice radius with Sc 3+ ionic radius (both 0.745 Å). Finally, the separation of trace scandium from the simulated BR leachate solution was demonstrated on an amorphous TiP column. The interference of Fe 3+ has been partially resolved by on-column reduction using sodium sulphite. The optimized final eluate contained only Sc, Fe and Al. The concentration ratio of Sc/Fe can be increased by a factor of 8.8 and Sc/Al by 265 through a single cycle of chromatographic separation with a Sc recovery rate of 91.1%. KEY WORDSTitanium phosphate; scandium recovery; ion exchange; bauxite residue.

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.

Three zirconium phosphate products A, B and C, made through different synthesis routes, were investigated for their europium and americium ion exchange properties utilizing radiotracers

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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 α‐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, pKa1 determination, and 152Eu(III) and 241Am(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.