European Metallurgical Conference 27.6.2017 Leaching of Eudialyte concentrate and REE-precipitation - Pilot plant Treatment of Eudialyte Concentrate - Yiqian Ma, Srecko Stopic, Bernd Friedrich

Introduction Rare earth resources Rare earth resources Polinares project, Fact sheet: rare earth oxides, released in 2012 Rare earth resources Polinares project, Fact sheet: rare earth oxides, released in 2012

About EURARE project www.eurare.eu

Eudialyte from Norra Kärr and Tanbreez *Both without radioactivity www.eurare.eu Norra Kärr

Eudialyte from Tanbreez and Norra Kärr Metal Norra Kärr Tanbreez Al 3.32% 3.36% Ca 1.44% 4.33% Fe 5.54% 6.08% Hf 0.09% 0.11% Y 0.45% 0.33% Nb 0.12% 0.44% Yb 0.03% 0.04% Zr 2.28% 5.08% Ce 0.30% 0.52% Dy 0.01% 0.06% Gd 0.02% La 0.14% 0.25% Nd 0.15% 0.21% TREE 1.20% 1.60% Eudialyte Na4(Ca, Ce,Fe)2ZrSi6O17(OH, Cl)2 Norra Kärr Tanbreez

Main aims of large-scale test Treatment of Eudialyte concentrates in demonstration scale in order to produce >20 kg rare earth carbonate Removal of iron and aluminium in order to produce fine product with 45-50 % REE-oxide content Improvement of efficiency and automisation degree of the demonstration plant Eudialyte concentrate Residue after REE extraction

Flowsheet and parameters of lab-scale Variable Norra Kärr Tanbreez Con.: HCl/(kg/L) 1:1 1:1.2 Con.: Water/(kg/L) 1: 3 1: 4 Leaching Temperature/℃ Room temperature Reaction time/min 60 *Dry digestion(fuming) with concentrated acid can prevent silica gel formation

Metal balance of lab-scale pH 4.0-4.1 pH ~6.0

General flowsheet of demo plant Eudialyte Norra Kärr Tanbreez Fuming Leaching Neutralization (CaCO3) Filtration Precipitation (Na2CO3) Filtration % TREE Norra Kärr : 1.2 Tanbreez : 1.6 REE-carbonate SX-MEAB

Continuous process for leaching of eudialyte leaching cascade containing four stirred glas reactors (3x10L, 1x8,5L) filter press stirred collecting container (250L) leaching reactor(2x100L) fuming reactor(2x40L)

Parameters for large scale processing of eudialyte Unit Norra Kärr 1 Norra Kärr 2 (optimal) Tanbreez Total quantity each day kg - 36 30 Fuming temperature oC 70-80 Fuming time min 60 Addition of Eudialyte concentrate 7.5 per reactor (overload) 6 per reactor Addition of HCl (31% w/w) L 5 per reactor Leaching temperature 50 Room temperature Leaching time h 1 Addition of water in leaching reactor 30 per reactor 20 per reactor Extraction efficiency % 85.4 84.8 84.2

Dry digestion(fuming) - the heart of this process Characteristics: Average treatment rate (kg/hour): 6 Reactor volume (L): 40 Digestion media HCl, 31% (L): 6-7.2 Fuming time (min): 60 Temperature: RT, due to exothermic effect increase to 60-70 °C Flux- air operated diafragm pump Flow rate (30 L/min) Operated pressure

pH adjustment using CaCO3 At pH 4 (first stage of leach purification), mainly Zr, Al, Fe transferred to the residue, while REEs remain in solution.

Filtration using a semi-continuous chamber filter press pH of solution higher than 4.0 Max pressure: 6 bar Flow rate of suspension: 1-1.2 L/min Maximum Capacity: 6kg wet residue

Material balance diagram

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Leach residue composition after separation in filter press Metal Norra Kärr /% Tanbreez/% Al 4.960 4.360 Ca 1.370 1.330 Fe 0.408 0.810 Hf 0.044 0.103 Y 0.045 0.057 Nb 0.020 0.069 Yb 0.006 0.008 Zr 2.320 5.390 Ce 0.023 0.049 Dy 0.005 0.007 Gd 0.004 La 0.083 0.019 TREE 0.180 0.210 The overall yields reached 85.1% and 84.4% respectively. Washing residue after filtration makes a new concentrate for recovery of Zr, Hf and Nb.

REE precipitation efficiency with Na2CO3 After precipitation with sodium carbonate pH~6.0, more than 95 % of REEs transferred to REE-carbonate

Removal of iron from the produced REE-Carbonate Element Al Ca Fe Hf Zr Na Nb Si TREE REE Carbonate (%) 3.33 6.0 7.86 0.002 0.05 4.73 0.007 0.031 15.1 REE carbonate re-dissolved with HCl Oxidation of Fe(II) to Fe(III) using 4 ml 30 % H2O2 per liter solution pH value adjusted using diluted NaOH to pH 3.5 to 3.8 Need of flocculants, filtration

Separation using flocculant Removal of iron REE precipitation

Produced REE Carbonate La Ce Nd Tb Gd Y Sm Dy Eu % 5.23 10.5 3.90 0.20 0.85 7.15 0.93 1.17 0.08 Er Sc Fe Al Zr Na Ca Mn TREE 0.78 <0.01 3.31 0.05 0.02  4.18 0.23 31.00 

Summary Conclusions Outlook Based on the results obtained from the small scale experiments, the large scale experiments were carried out successfully. The fuming process should start with addition of concentrate first and then the acid in appropriate ratio to avoid silica gel formation. During neutralization with CaCO3 (pH~ 4.0), more than 95% of Zr, Al and Si go into the residue During precipitation with Na2CO3 (pH~ 6.0), more than 95% of REEs are precipitated for both the concentrates, thus increasing the amount of REEs in the REE-carbonate produced. Outlook Reducing loss of REE during precipitation processes The residue can be used as a potential source of Zr, Hf, Nb recovery

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