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					Recovery of Nd and Dy from
Rare Earth Magnet Scrap


Sakae Shirayama1 and Toru H. Okabe2
1 Department of Materials Engineering, the University of Tokyo, Japan
2 Institute of Industrial Science, the University of Tokyo, Japan
Nd−Fe−B magnet
Nd−Fe−B magnet is a rare earth permanent magnet.
  main phase: Nd2Fe14B intermetallics
  advantage:
    high magnetic intensity
    high coercive force
    abundance of minerals which contains Nd
  applications:                               Fig. Nd-Fe-B magnet
    Hard Disk Drive in personal computer
    motors for air conditioner
    motors for Hybrid Electronic Vehicle (HEV)

   ★ Dy addition improves heat-resistance.
                                                   MIT_Shirayama_slide 2
Resource for Nd and Dy
Rare earth deposits
Bastnaesite                                  Ion adsorption ore (ion clay)
                                                                                   Other
   La             Ce                Nd                  Y          La Nd           heavy
                                                                                    REE

0 10 20   30 40   50 60   70   80 90  100     0 10 20   30 40   50 60 70     80 90          100
                  mass%                 Other                   mass%
                               Pr   Sm heavy                     Ce Pr Sm Dy
                                         REE
U : 8.7×10-4 mass%
                                              U, Th : −
Th : 0.14 mass%
Nd : 1 ~ 2 mass%                              Nd        : 70 ~ 200 ppm
Dy : trace                                    Dy        : 40 ~ 120 ppm
○Rich in light REE                            ○Rich in heavy REE
 (La, Ce, Pr, Nd)                              (Tb, Dy, Ho, Er, Tm, Yb)
○Abundant all over the world                  ×Distributed only in China
×Contain U and Th                             ○No U and Th
                                                                    MIT_Shirayama_slide 3
                                Problems in supply of REE
                                      Worlds’ 97 % supply is dominated by China.
                                      Prices of REE are escalating especially for Dy.
                                                                                            120
                          120       Other                     China                                                        Dy
Amount of production, w / kt




                                     3 kt                                                   100
                          100                                 120 kt
                                    (3%)




                                                                               Price US$ / kg
                                                              (97%)                             80
                               80             Total
                                              123 kt
                                                                                                60
                               60
                                                                                                                                           Sm
                               40                                                               40                            Nd

                               20                                                               20

                               0                                                                 0
                               1950    1960     1970     1980    1990   2000                    2005.1              2006.1                 2006.12
                                                       Year                                                       Year. Month
                               Change in amount of production of REE.                           Change in prices of Nd, Dy, and Sm.
                                World share in supply of REE in 2006.                                    (Industrial rare metals (2007))
                                (USGS Mineral Commodity Summaries (2007))
                                                                                                                           MIT_Shirayama_slide 4
Purpose of this study
 Supply of Dy has limitation.
 Production of REE from ore induces
 environmental pollution.
 Large amount of Dy-containing Nd−Fe−B
 magnet scrap will be produced especially from
 automobiles.


Development of an efficient recovery process
 of Nd and Dy from Nd−Fe−B magnet scrap.


                                        MIT_Shirayama_slide 5
Recovery of Nd and Dy from magnet scrap
        HDD        HEV                REE extractant


                                    have a stronger affinity for
                                          REE than Fe
Dy-containing                                   or
  Nd−Fe−B                             easily react with REE
magnet scrap

                      Recycling process
                   (Extraction of Nd and Dy)




                Pure Nd   Pure Dy     Fe−B alloy

                                                       MIT_Shirayama_slide 6
  Overview of this study
             Dy-containing Nd−Fe−B magnet scrap             MgCl2(l)

                    Nd and Dy extraction by molten MgCl2

This study      NdClx (l) + DyClx (l) + Mg (l) + MgCl2 (l) + Fe−B (s)

                            Solid / liquid separation
                L                                                     S    Fe−B (s)

                    NdClx (l) + DyClx (l) + Mg (l) + MgCl2 (l)

                        Vacuum distillation / separation                           MgCl2 (l, g)

                                   NdClx (s, l)        DyClx (s, l)       Mg (g)

                              Refining / reduction

                                      Nd (s)             Dy (s)
  Fig. Flow chart of the recovery process by using MgCl2 as an extracting agent.
                                                                            MIT_Shirayama_slide 7
    Experimental work
        Extraction of Nd and Dy by molten MgCl2
           Reaction temperature: 1273 K
           Reaction time: 3 h, 6 h, 12 h
Stainless-steel wire                                                             Alumina tube
                                                                                 Stainless-steel
 Stainless-steel foil                                                            chamber
    Dy-containing                                                                Thermocouple
    Nd−Fe−B alloy
                                                                                 Heating element
        Fe crucible                                                              Stainless-steel
                                                                                 basket
     Molten MgCl2
                                                                                 Ti sponge
                        Fig. Schematic illustration of the experimental setup.
 2 Nd (s) + 3 MgCl2 (l) → 2 NdCl3 (l) + 3 Mg (l)             ΔG° = −151.6 kJ at 1300 K
   Dy (s) + MgCl2 (l) → DyCl2 (l) + Mg (l)                   ΔG° = − 57.6 kJ at 1300 K
                                                                            MIT_Shirayama_slide 8
Experimental result (1)-alloy
                        (a) Initial.                         Nd2Fe14B PDF#39-0473
                                                             Fe       PDF#06-0696
 Intensity, I (a. u.)




                        (b) After exp. (1273 K, 6 h)
                                                           Fe obtained


                   10                  30          50            70         90
                                            Angle, 2θ / degree (Cu-Kα)
                             Fig. XRD patterns of Dy-containing Nd−Fe−B alloy.

                            Fe was obtained after experiment.
                                                                            MIT_Shirayama_slide 9
Experimental result (1)-salt
                        (a) Initial.                           MgCl2 PDF#37-0774
                                                               NdCl3 PDF#12-0785
 Intensity, I (a. u.)




                        (b) After exp. (1273 K, 6 h)
                                                               NdCl3 produced


                   10                  30          50            70           90
                                            Angle, 2θ / degree (Cu-Kα)
                                       Fig. XRD patterns the obtained salt.

 Nd was extracted into molten MgCl2 as NdCl3
                                                                              MIT_Shirayama_slide 10
 Experimental result (2)-alloy
Table      Change in mass and composition of Nd-Fe-B alloy.
                                                                Conc. of element i in
    Reaction Reaction Mass of alloy Mass of alloy                 Nd-Fe-B alloy,
Exp. temp.,   time,    before exp.,  after exp.
No.                                                                Ci (mass%)a
      T/K     t’’ / hr  w alloy / g  w’ alloy / g
                                                                  CNd        CDy
initial      −        −             −                −            26.3       4.9
 #1        1273       3           18.97            15.94           9.4       2.3
 #2        1273       6           19.68            16.45           5.9       2.1
 #3        1273      12           14.97            11.51           3.3       0.8
a: Determined by ICP-AES analysis.                                  decreased
                                                        wi, alloy
                                                       wi , alloy×100 (%)
          REE content ratio,          Rialloy/alloy   = 0
              wi0, alloy : initial mass of element i in alloy
              wi, alloy : mass of element i in alloy after exp.
              i       : Nd, Dy
                                                                            MIT_Shirayama_slide 11
REE content ratio, Rialloy/alloy
REE content ratio, Rialloy/alloy (%)
                                 100
                                                                     Nd
                                       80
                                                                     Dy
                                                                           90 % of Nd and
                                       60                                  87 % of Dy were
                                                                           removed
                                       40
                                                                           after reaction
                                       20
                                                                           for 12 h.

                                        0
                                            0    3      6      9      12
                                                Reaction time, t’’ / hr
              Fig. Change of REE content in the magnet alloy.
                                                                                 MIT_Shirayama_slide 12
 Experimental result (2)-salt
Table     Mass and composition of salt obtained after experiment.
                                                               Conc. of element i in
    Reaction Reaction Mass of MgCl2 Mass of salt
Exp. temp.,                                                            salt,
              time,    before exp., after exp.
No.                                                               C’i (mass%)a
      T/K     t’’ / hr  w MgCl2 / g  w’ salt / g
                                                                 C’Nd        C’Dy
initial     −         −             −               −             0l         0lll
 #1       1273       03           26.85           19.79          12.9        2.1
 #2       1273       96           30.07           30.65          14.9        2.0
 #3       1273       12           23.21           15.78          21.9        3.8
a: Determined by ICP-AES analysis.
                                                                     increased
                                                             wi, salt
      REE extraction ratio,             Risalt/alloy =
                                                             wi0, alloy×100 (%)
           wi0, alloy : initial mass of element i in alloy
            wi, salt : mass of element i in alloy after exp.
           i       : Nd, Dy
                                                                           MIT_Shirayama_slide 13
REE extraction ratio, Risalt/alloy
                                  100
 Extraction ratio, Risalt/alloy (%)



                                      80
                                                                          More than 80 %
                                      60                                  of Nd and Dy
                                                                          were extracted
                                      40
                                                                          after reaction
                                                                   Nd     for 12 h.
                                      20
                                                                   Dy
                                      0
                                           0   3       6      9      12
                                               Reaction time, t’’ / hr
Fig. Change of extraction ratio to the molten salt.
                                                                               MIT_Shirayama_slide 14
Conclusions
     Selective extraction of Nd and Dy
         directly from magnet scrap
   was investigated utilizing molten MgCl2.

 It is possible to extract Nd and Dy into molten
 MgCl2 selectively from Nd−Fe−B magnet alloy.
 Effective recovery process of Nd and Dy from
 magnet scrap can be established by utilizing
 molten MgCl2.

                                      MIT_Shirayama_slide 15
Future work


 Investigate a new gas phase treatment for
 direct recovery of Nd and Dy from magnet
 scrap using various extracting agents.

 Development of a new simultaneous
 extraction and separation of rare earth
 elements from magnet scrap.


                                      MIT_Shirayama_slide 16