RARE EARTHS CHEMISTRY: SCIENTIFIC, TECHNOLOGICAL AND

Faculty of Chemistry, Sofia University, Bulgaria

M. Milanova, D. Todorovsky, N. Minkova, A. Terziev, M. Getsova, G. Tzvetkov, N. Petrova, M. Uzunova,

S. Anastasova, J. Zaharieva, R. Kralchevska,R. Todorovska

RARE EARTHS CHEMISTRY: SCIENTIFIC, TECHNOLOGICAL AND PRODUCTION ACTIVITIES

AT THE DEPARTMENT OF INORGANIC CHEMISTRY, SOFIA UNIVERSITY

Group of Rare and Rare Earth Elements, Est. 1984


Chemistry of rare earth elements

SOLID SOLUTIONS

COORDINATION COMPOUNDS

MECHANOCHEMISTRY

Leaching,separation,purification

Materials,based on REE

SilicatesPolymetallic oxidesModified photocatalystsThin films Optical sensors

RE products


Plan

Materials based on REE

RE products


Polymerized complex method, PCM


Polymerized complex method Problems

Reaction CA /EG Factors influencing the complex compositionsNature of the complexes in bimetallic systems Alcoholic group deprotonationThermochemical behaviour of the complexes; nature of the final precursorApplication of the solutions of complexes for thin film deposition


Synthesized and characterisedmaterials

Buffer layers for high temperature superconductors (Y2O3, CeO2, YSZ)

Materials of high magnet restriction (LaMnO3, pure/doped with Ca)

Magnet materials (Fe2O3, Y3Fe5O12,(granite), YFeO3, Y3Fe5O12 doped with Al or Се)

Ferroelectrics ( La2Ti2O7, Nd2Ti2O7)

Ionic conductors (Y2Ti2O7 )

Oxygen sensors based on YSZ, doped with Pt nanoparticles (Assoc. Prof. Dimitrov, Assoc. Prof. Dushkin)

Optical oxygen sensors

Photocatalysts based on TiO2, including modified by doping with Lа or by mechanochemical treatment (Assoc. Prof. Dimitrov)


Deposition of thin films Spray-pyrolysis /PCM (mixed-metal citrates)


SEM images (8 mol% Y) Т substrate 350oC;additionally annealed at 750оС

On fused quarz On glass

Thin films of Y-stabilized ZrO2 Buffer layers for high temperature superconductors (YBCO)

film on quarz

film on fused silica

powder

XRD


AFM (5x5 μm), from Ce(Cl)Cit (fused quarz)

AFM (10x10 μm), from Ce(N)Cit (fused quarz)

Thin films of CeO2Buffer layers for high temperature superconductors

size of the grains (250-400)x(120-240) nm from Ce(N)Cit,

Т substrate 500оСfrom Ce(N)Tar

Т substrate 350оС


Thin films of LaMnO3Materials of high magnet restriction

SEM of manganite films with thickness ~150 nm on SrTiO3, x20 000).

LaMnO3La0,7Ca0,3MnO3

XRD

AFM (6,5x6,5 μm) of LaMnO3 film on SrTiO3


Thin films of YFeO3Ferromagnetic behaviour,potential UV-Vis photocatalyst

AFM (5x5 μm) of

YFeO3 film on SrTiO3


Thin films of La-doped TiO2Photocatalysts

SEM images, post deposition heating at 400ºC (a), 500ºC (b,c).

glass graphite stainless steel

Degradation of methylene blue, TiO2:5 mol% La

Ti-coated steel

silica


Silanes

Tetraethoxy silane(TEOS)

Methyl triethoxysilane(MTEOS)

Octyl-triethoxysilane(OtEOS)

Ru(dpp)32+

Thin films based on SiO2Optical oxygen sensors

[ ]20 1 OКII

SV+=


SiO2-based filmsEffect of sonication

0

200

400

600

800

1000

1200

1400

1600

1800

2000

TEOS TEOS +OtEOS

TEOS +MtEOS

TEOS TEOS +OtEOS

TEOS +MtEOS

Ster

n-V

olm

er c

onst

ants

(n.1

0-3 %

-1)

No sonication Sonication

Gas phase Water


PMMA films Optical oxygen sensors

SEM

MMA polymerized

PMMA solution

PMMA solution

AFM


PMMA filmsOxygen in the gas phase

0 20 40 60 80 1000,0

0,5

1,0

1,5

2,0 Ksv = 0,0105

1

I 0/I

Concentration of O2, %0 20 40 60 80 100

0,0

0,5

1,0

1,5

2,0

Ksv = 0,0017

I 0/IConcentration of O2, %

film preparedvia PMMA solution

film prepared via in situpolymerization of MMA


PMMA filmsDissolved oxygen in water

0 10 20 30 40 50 600,9

1,0

1,1

1,2

1,3I 0/I

Concentration O2, ppm

film preparedvia PMMA solution

KSV=0,0062


Hybrid matrix, SiO2/polyester Optical oxygen sensors

TEOS/CA/EG = 4 : 1 : 1


Hybrid matrix, SiO2/polyester

0 20 40 60 80 1000

1

2

3

4

5

I 0/I

Concentration of O2

Ksv =0,0302

0 5 10 15 20 25 30 350,0

0,2

0,4

0,6

0,8

1,0

Concentration of O2, ppmIn

tens

ity, a

. u.

Ksv 0,0198

Oxygen in the gas phase Oxygen dissolved in water


Ksv, comparison

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

PMMA MMA Hybrid

Ksv

Gas Water

Eu β-diketonates

Immobilization in PMMA matrix

DBM


Eu(DBM)3oxygen sensitive

500 550 600 650 7000

10

20

30

40

50

60

70

80

Inte

nsity

, a. u

.

Wavelenght, nm550 600 650 700 750

0

50

100

150

200

250

300

350

400

450

Inte

nsity

, a. u

.

Wavelength, nm

265 μs 75 μs

Powder Immobilized in matrix

AFM ,Eu(DBM)3 in PMMA

AFM ,Eu(DBM)3 in PMMA


Eu(DBM)3.Phen

500 550 600 650 700 7500

50

100

150

200

Inte

nsity

, a.u

.

W avelength, nm550 600 650 700 750

0

50

100

150

200

250

300

350

400

450

Inte

nsity

, a. u

.

Wavelength, nm

Powder Immobilized in matrix

530 μs363 μs

Phen – 1,10-phenathroline

AFM ,Eu(DBM)3.phen in PMMA


Methods of RE recovery from waste and by-productsProduction routes for some RE compoundsdeveloped and carried out in practice

REE products, Technology and production activities


Phosphogypsum H3PO4

Mechanochemical RE concentratetreatment

Ca separation

RE concentrate, low Ca

non-RE sepn

REO

RE sources


Ce separation

Mechano-chemistry

Selective dissolution

Selective precipitation

Ln2O3CeO2

REO treatment


Solid statecomplexes,

DEHPA

REO/Ln2O3

REO Ln2O3

Extraction

La-Nd Didymium Heavy RE,Eu

LME

La2O3

Nd2O3

Prconcentrate

Concentrate, Eu enriched

Eu2O3


Pilot facilities


Some of the products

Product REE yield, % Purity

REE concentrate of low Са content 99 Са<1,5%

RE oxide mixture 98 95-99%

СеО2 94-98 Ln2O3: < 10-2%, other impurities: < 0.1%

Oxide mixture, Се-free Се < 1,5%

Nd2O3 50 99.5%

20 99.9%

Eu2O3 25 99.8%

70 98.5%

Y2O3 70 99.999%

Y2O3 (from YAG) 85 Impurities of Аl

Polishing material 85 Cerox quality


Thank you!

Dr. Maria Milanova, Assoc. Prof.,

+ 359-2-8161217

[email protected]

Documents

RARE EARTHS CHEMISTRY: SCIENTIFIC, TECHNOLOGICAL AND