SEPARATION AND RECOVERY OF RARE EARTHs AFTER RED MUD LEACHING BY CATION - EXCHANGE CHROMATOGRAPHY

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2 National Technical University of Athens School of Chemical Engineering Laboratory of Inorganic and Analytical Chemistry SEPARATION AND RECOVERY OF RARE EARTHs AFTER RED MUD LEACHING BY CATION - EXCHANGE CHROMATOGRAPHY Lamprini-Areti TSAKANIKA, Klaus-Michael OCHSENKÜHN, Maria OCHSENKÜHN-PETROPOULOU Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, NTUA Iroon Polytechniou 9, Zografou, 15773, Greece btsakanika@gmail.com, oxenki@central.ntua.gr

3 Aim of the present study The selective separation and recovery of rare earths from the main elements co-existing in the leachate after red mud acidic leaching. Development and optimization of an ion exchange process using a suitable industrial strong cation exchange resin and applying multiple successive elutions using selective eluents firstly in lab scale. Application of the developed ion exchange process on a pilot plant.

4 RARE EARTH ELEMENTS (REEs) Group of 17 chemical elements 15 lanthanides (La-Lu) Yttrium (Y) Scandium (Sc) Scandium and yttrium are considered rare earth elements since they tend to occur in the same ore deposits as the lanthanides and exhibit similar physico-chemical properties LREEs: light rare earths (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd; also known as the cerium group) HREEs: heavy rare earths (Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y; also known as the yttrium group)

5 The REEs with the greater demand- Their uses Lanthanum Cerium Fluid Catalytic Cracking (FCC) - Catalysts Neodymium Dysprosium Permanent Magnets Yttrium Europium Cerium Lanthanum Terbium Scandium Lighting Aerospace and defense technology, athletic equipment, solid oxide fuel cells (SOFCs) Source : Department of Energy, USA

6 CRITICAL ELEMENTS Five of the most critical elements are rare earths (Nd, Dy, Eu, Y, Tb) (new sources, processes, recycling, substitutes) Source : Critical Materials Institute (Ames Lab, USA )

7 MAIN MINERALS OF REEs Thortveitite [Sc 2 Si 2 O 7 ] (main mineral of scandium, very rare) Bastnasite [(REE)(CO 3 )F] (Light REEs,) Monazite [(REE)PO 4 ] Xenotime [YPO 4 ] (Heavy REEs) ALTERNATIVES RESOURCES FOR REEs Apatites (~ 1kgREEs/ton) Exploitation byproducts of uranium (105g Sc/ton in 1000m depth, Ukraine), tungsten, lead, tin, zirconium, titanium and mine tailings Phosphate rocks and phosphogypsum Bauxites (of low concentration in Al) Red mud, bauxite residue after Bayer process (130g Sc/ton, 1kg REEs /ton ) REEs recycling (permanent magnets, batteries, lamps, phosphors)

8 U$/Kg REEs values Rarity of economically exploitable sources (outside China having the 97% of the annual world market of REEs) High demand for modern and high technology applications High commercial values of REEs YEAR 2010 YEAR 2011 YEAR 2012 YEAR La Ce Nd Pr Sm Dy Eu Tb Y Sc REEs OXIDES Change in the price of REEs oxides (2010 to 2013) Source: Lynas Corporation (China Domestic prices), USGS (Sc, Y)

9 US$/kg % 99,99% 99, ,9999% Scoxide purity Source: USGS Prices of scandium oxide (US$/kg) vs % purity

10 US$/g scandium fluoride, 99.9% purity scandium iodide, % purity dendritic, metal ingot, metal scandium chloride, 99.9% purity scandium acetate, 99.99% purity Prices (US$/g) of scandium metal and its compounds ( )

11 RED MUD The residue after bauxites treatment for alumina production using Bayer process (about 50 % Fe 2 O 3 ) Annual production of red mud in Greece tons (AdG) High alkalinity (ph>11), very fine (< 10μ) Rich in main elements ( Fe, Ti, Si, Ca, Na ) It contains also elements of techno-economical interest (V, Zr, Nb, REEs, etc) Greek red mud is enriched in REEs by a factor almost 2 in comparison to the initial bauxite (Source: M. Ochsenkühn-Petropulu, Th. Lymperopulu, G. Parissakis, Anal Chim Acta (1994) 296, ) Problem Its disposal due to its complex character and alkalinity combined with its annually huge production Solutions Safe disposal (dry stacking, dry disposal) Neutralization Reuse of red mud Utilization (Recovery of valuable elements)

12 Mineral found in bauxite Hydroxyl-bastnaesite (Nd,La)CO 3 (OH,F)) M.Ochsenkühn-Petropulu and K.M.Ochsenkühn, Microscopy and Analysis, 37, (1995)

13 Mineralogical analysis of Greek red mud H H D H C H N D H H H C D N

14 FT-IR analysis of a Greek red mud sample G:Gibbsite, K:Kaolinite, Go:Goethite, D:Diaspore, Cn:Cancrinite, So:Sodalite, He:Hematite Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

15 Morphology and Semi Quant composition (surface analysis) of Greek red mud observed by SEM- EDX Element oxides % Wt EDX Semi quant % Wt AAS Full quant Fe 2 O Al 2 O CaO Na SiO TiO V 2 O Cr 2 O Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

16 Average concentration of lanthanides, yttrium and scandium in Greek bauxites and red mud samples from the alumina production and corresponding enrichment factors (all concentrations in μg/g) Element Average concentration Average Enrichment Factor Bauxite R.S.D. % Red mud R.S.D.% Red mud/bauxite La 87.2 ± ± Ce ± ± Pr 13.9 ± ± Nd 62.4± ± Sm 13.2± ± Eu 2.5 ± ± Gd 12.8 ± ± Dy 7.0 ± ± Ho 2.0 ± ± Er 8.1 ± ± Yb 8.0 ± ± Y 55.9 ± ± Lu 1.38 ± ± Sc 59.0 ± ± Mean 1.99 LREE/ HREE ΣREE ± ±12.36 Source: M. Ochsenkühn-Petropulu, Th. Lymperopulu, G. Parissakis, Anal Chim Acta (1994) 296,

17 Concentration [g/ton] of REEs in greek red mud batches ( ) Red mud 1993 Red mud 2001 Red mud 2007 Red mud 2012 Mean Sc ±11.9 Y ±11.0 La ±22.1 Ce ±48.9 Nd ±13.2 Sm ±3.7 Gd ±1.45 Eu ±0.65 Er ±0.96 Yb ±0.63 Total ±75.5 (±7.7%)

18 Value of REEs / ton of Greek red mud REEs oxides Target price of oxides % ($/kg) Average concentration of REEs oxides Βauxite (g/ton) RM (g/ton) Value ($/ ton RM) Sc (95.3%) Y La Ce Pr Nd Eu Gd Dy Er Total Source: Hefa 31 December, and USGS Jan 2014 (Sc)

19 Flow sheet of the innovative multi process method for the recovery of REEs from red mud Purity 99.1%

20 After the selective acidic leaching of red mud under ambient temperature and pressure, the leachate is enriched in Sc and other REEs, but it contains also the main elements of red mud. An ion exchange process is necessary for further separation of Sc and other REEs from the remaining main elements after the leaching process. Their further purification is achieved using suitable extraction /back-stripping processes.

21 [a] Semi-quantitative analysis of red mud samples by EDAX before [a] and after leaching [b] [b] Oxides [%] Before leaching After leaching Na 2 O Al 2 O 3 SiO 2 CaO TiO 2 V 2 O 5 Fe 2 O Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

22 2 nd elution effluent effluent Ion exchange process 2 Ion exchange Multiple successive elutions with mineral acids Sc Filtered leachate 1 Main elements 1 st elution 3 Y, {Lns} 3 rd elution Analysis with ICP-OES Optima 7000 DV Perkin Elmer Analysis with AAS 240FS Varian Analysis with ICP-OES Optima 7000 DV Perkin Elmer

23 Experimental conditions I. Lab scale Resin bed volume: V=25ml packed in glass column Flow rate: Q=1ml min -1 Residence time: τ=25min II. Pilot plant Resin bed volume: V=5L packed in glass column Residence time: τ=25min (same as in lab scale) Flow rate: Q=12L h -1 The flow rate was calculated by the formula: τ=v/q where τ=25min

24 Lab scale Pilot plant (School of Chem. Enginnering, NTUA)

25 The pilot plant unit for the utilization of red mud (Semi-Industrial Lab, School of Chemical Engineering - National Technical University of Athens)

26 Lab scale experiments Absorption of scandium and other REEs Breakthrough curve of Sc and Y (Column vol.25ml, flow rate 1mL min -1, bed volume=25ml) The feed solution arising from the leaching of red mud with dilute HNO 3 Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

27 Absorption of Fe Breakthrough curve of Fe (Column vol.25 ml, flow rate 1mL min -1, bed volume=25ml) The feed solution arising from the leaching of red mud with dilute HNO 3 Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

28 1 st elution: Quantitatively removal of the main elements of the leachate % removal of main elements with 1.75M HNO 3 (V feed solution =50mL) Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013) Almost the same behavior with 1.75M HCl but lower volumes are required for their quantitative removal

29 Eluent to feed solution 2:1 1 st elution: Removal of Fe with 1.75M HNO 3 or 1.75M HCl Eluent to feed solution 3:1 % removal of Fe with 1.75M HNO 3 or 1.75 M HCl (V feed solution =50mL) What about REEs? Sc and Y remain almost completely in the ion exchanger, while Fe was completely removed. The losses of Sc and Y were higher in HNO 3 (15% for Sc and 7% for Y) in comparison with those in HCl (3% for Sc and 5% for Y). Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

30 2 nd elution: Selective recovery of scandium (Lab scale) I. Type of eluent As eluents HNO 3, HCl and H 2 SO 4 were tested for the recovery of Sc 1M H 2 SO 4 was found to be the most suitable eluent, achieving selective recovery of Sc about 80% from the selected strong cation exchanger Only Y was co-eluted at a total percentage of 10% Flow rate: 1ml min -1 Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013) Sc Eluent to feed solution ~1:1 Sc recovery 80% Elution curves (a) and % REEs recovery (b) with H 2 SO 4 V feed solution = 60ml

31 II. Effect of flow rate Increasing the flow rate of the eluent, the recovery of Sc is decreased, while the losses of Y remain almost constant % recovery of Sc and Y vs flow rate of 1M H 2 SO 4 Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

32 3 rd elution: Recovery of Y and Lns with 6M HNO 3 or 5M HCl Y 6M HNO 3 Quantitative recovery with eluent to feed solution >3:1 Y % Y and Lns recovery with HNO 3, V feed solution = 50ml 5M HCl Quantitative recovery with eluent to feed solution 2.5:1 Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013) % Y and Lns recovery with HCl, V feed solution = 50ml

33 1 st elution: Removal of Fe and other main elements Eluent to feed solution 3:1 1.75M HNO 3 % main elements removal in HNO 3, V feed solution = 50L Eluent to feed solution 1:1 1.75M HCl Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013) % main elements removal in HCl, V feed solution = 50L

34 Main Elements Feed solution (mg) % Removal with effluent % Removal with 1.75M ΗCl 1:1 % Total removal Fe Ca Na Al Ti V Si Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

35 2 nd elution: Recovery of Sc (combination of 1 st and 2 nd elution) % REEs recovery in HCl and H 2 SO 4, V feed solution = 50L Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013) % main elements removal in HCl and H 2 SO 4, V feed solution = 50L

36 REEs Feed solution (mg) % Removal in effluent % Recovery in 1.75M ΗCl 1:1 % Recovery in 1M H 2 SO 4 1.2:1 % Total recovery Composition of 1M H 2 SO 4 eluate (mg) Sc Y La Ce Nd Eu Er Yb Main elements 2 nd elution: Recovery of Sc (combination of 1 st and 2 nd elution) Fe Ca Na Al Ti V Si Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

37 REEs Feed solution (mg) % Recovery in 5M ΗCl 2.5:1 Composition of the 5M HCl eluate (mg) Y La Ce Nd Eu Er Yb Ca Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

38 An ion exchange process is developed for the separation and purification of REEs from the main elements co-existing in the leachate after the acidic leaching process. Further purification of the REEs is achieved by appropriate extraction/back-stripping processes. The quantitative removal of the main elements is achieved with 1.75M HCl, which was found to be more suitable than nitric acid, requiring lower volumes of the eluent. The separation and the selective recovery of Sc about 80% is obtained using as eluent 1M H 2 SO 4. Only few amounts of Y are coeluted while the other REEs remain in the column. A third elution using 5M HCl lead to the quantitative recovery of Y and Lns as a group. The developed ion exchange process was successfully applied on a pilot plant and a good agreement with the optimized parameters found in lab experiments, was achieved.

39 Prof.Dr.Maria Ochsenkühn-Petropoulou ( coordinator) Dr. Klaus - Michael Ochsenkühn Dr. Lamprini - Areti Tsakanika Dr. Theopisti Lymperopoulou Dr. Leonidas Mendrinos Dr. Konstantinos Hatzilyberis Dr. Konstantinos Salmas Dr. Rachel Argyropoulou Students Anthi Psalida Panagiotis Pagonas Giannis Gourousis Panagiotis Rebestekos Emmanuel Foundoulakis

40 Thank you for your attention!