Removal of Iron from Titanium Ore through Selective ChlorinationUsing Magnesium Chloride

Jungshin Kang1,+ and Toru H. Okabe2

1Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan2Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan

A selective chlorination process using magnesium chloride (MgCl2) as chlorinating agent was investigated with the aim of developing aprocess for removing iron directly from ilmenite, which is a low-grade titanium ore known as FeTiO3. Two crucibles, one consisting of titaniumore and the other consisting of a mixture of titanium ore and MgCl2, were placed in a gas-tight quartz tube, and then both crucibles were heatedto 1000K. In some experiments, H2O vapor was introduced in the quartz tube. HCl gas produced from the MgCl2/titanium ore mixture reactedwith the iron present in the titanium ore placed in the other crucible to produce TiO2. Iron present in the titanium ore of the titanium ore/MgCl2mixture reacted with MgCl2, and MgTiO3 and MgO were obtained. Iron in the titanium ore present in both crucibles was removed as FeCl2 (l,g).In these experiments, the effects of the particle size of the titanium ore and the atmosphere on selective chlorination were investigated. Inaddition, titanium ores produced in Vietnam, Australia and China were used as feedstocks. By the chlorination process, 97% TiO2 was obtaineddirectly in one step from the low-grade titanium ore containing 51% TiO2 under certain conditions, thus demonstrating the feasibility of theselective chlorination process for producing high-purity titanium dioxide from low-grade titanium ore. [doi:10.2320/matertrans.M-M2013810]

(Received March 26, 2013; Accepted May 15, 2013; Published July 25, 2013)

Keywords: ilmenite, titanium ore, selective chlorination, synthetic rutile, iron removal, titanium smelting

1. Introduction

Titanium (Ti) is widely used in various fields because of itsexcellent properties such as high strength to density ratio andhigh corrosion resistance; in addition, titanium is the ninthmost abundant element on the Earth’s crust.1) However,titanium is still used to a much lesser extent than iron (Fe)or aluminum (Al), mainly because of low productivity andhigh production costs involved at all processing stages.1) Forexample, the cost of processing titanium ore is 15 times higherthan that required for processing iron ore.2­5) To reduce theproduction costs, it is imperative to improve the early stagesof titanium production by developing a simple and effectiveprocesses for processing titanium ore to titanium metal.

Ilmenite and rutile are the key minerals used for titaniumproduction. Chemical formula of ilmenite is FeTiO3 with30­65% TiO2, while that of rutile is TiO2 with 95­100%TiO2.1,6,8,9) If we consider only the concentration of TiO2,rutile will be the most appropriate feedstock for themanufacture of titania (TiO2) pigment or titanium metal.However, ilmenite is used much more extensively as afeedstock. For example, the global production of ilmenite waseight times higher than that of rutile in 2011.7) This is becausethe price of ilmenite is much lesser than that of rutile. Further,ilmenite is much more readily available than rutile, with theshare of ilmenite in the world mine reserves being 94%.7)

Therefore, the role of ilmenite as the source for the titaniummineral is expected to become gain more significance.

As shown in Fig. 1, several processing stages are generallyrequired for removing iron from titanium ore for producingTiO2 pigment or titanium metal using ilmenite as thefeedstock.1,6,8,9) In many cases, first, ilmenite is upgraded tohigh purity TiO2 by the Becher process,10,11) the Beniliteprocess,12­14) or the slag production process.15) It is important

to reduce the amount of iron in the TiO2 ore feed for reducingthe amount of chloride wastes and the chlorine loss during thechloride process16) or the Kroll process.17) Many companiesplace a lower limit on the purity of TiO2 feed before placingthe feed into the chlorinator. Usually the feeds containing atleast 90% of TiO2 are used.18,19) Some countries includingJapan have much more strict criteria for a purity of TiO2 feed,and a purity of over 95% TiO2 is required in the Kroll process.However, due to the increase in the price of the TiO2 feed by,for example, the increase in the consumption of TiO2 feed inChina, recently, some companies in Japan have begun to use90% TiO2 feed in order to reduce the cost of the feedstock.20)

In the Becher process, various types of titanium ores areused as feedstocks.21) However, multiple stages are requiredfor treating iron, and a huge amount of iron compounds aredumped as wastes. In the Benilite process, processing of ironis simpler than the other processes. However, this processmakes use of highly concentrated 18­20% HCl and onlylimited types of titanium ore is used as a feedstock.21) In the

Slag process

Ilmenite (rock) : 30 – 50% TiO2

UGS process

Chloride process

95% TiO2

Sulfate process

Ilmenite (sand) : 35 – 65% TiO2

75 – 86% TiO2 (Ti slag)

Becher process Benilite process

90 – 93% TiO2 95% TiO2

Kroll process

Titanium

(Upgraded slag) (Synthetic rutile)

(5.1Mt TiO2 / year world) (0.1Mt Ti / year world)

Rutile : 95% TiO2

Titania pigment

Fig. 1 Currently used process for titania pigment and titanium produc-tion.1,6,8,9)

+Graduate Student, The University of Tokyo. Corresponding author,E-mail: jskang@iis.u-tokyo.ac.jp

Materials Transactions, Vol. 54, No. 8 (2013) pp. 1444 to 1453©2013 The Mining and Materials Processing Institute of Japan

slag process, iron in the titanium ore is reduced to metal bya carbothermic reaction, and TiO2 slag and iron metal areseparated. The scale of the slag process is large, and it is highspeed process. However, TiO2 with a low purity of 75­86% isobtained. For obtaining high purity TiO2 slag, it is essential toemploy additional upgrading process such as the upgradeslag (UGS) process,15) which entails multiple steps for thefurther removal of iron.

Extensive research has been conducted to improve thecurrently used upgrading processes of titanium ore. Amongthe various processes, selective chlorination has gainedsignificant attention. In the selective chlorination process,iron is only removed directly from the titanium ore as ironchlorides and high purity TiO2 is obtained. The selectivechlorination processes investigated so far have entailedthe use of chlorine gas (Cl2) under carbon22­25) or CO/Cl2mixture atmosphere,26­28) or metal chlorides as the chlorinesource.29­32) Among these processes, the first two processesrequire Cl2 gas and installation of the reactor become costlyand it also has environmental issue for operation.

The selective chlorination process that uses metal chlorideswas recently developed by Okabe et al.29,30) In recent studies,the authors investigated further improvement of the selectivechlorination using calcium chloride (CaCl2) as the chlorinat-ing agent, and 97% TiO2 was successfully obtained directlyfrom titanium ore containing 51% TiO2 in a single step.31,32)

However, because CaCl2 was used as chlorinating agent, itwas needed to decrease the activity of CaO by the productionof complex oxides such as CaTiO3 for producing HCl gas.In addition, high purity TiO2 could not be obtained when theexperiment was conducted under Ar gas flow atmosphere.

Recently, on the basis of thermodynamic analysis,33) it wasanticipated that extracting chlorine source such as HCl gasfrom MgCl2 rather than CaCl2 is easier because HCl gas canbe produced even under standard state condition (aMgO = 1),and is possible even at lower temperatures. In this study, inthe viewpoint of improvement of HCl gas production and theverification of feasibility for upgrading titanium ore byutilizing MgCl2 for the selective chlorination, the authorsused MgCl2 as a chlorinating agent to remove iron directlyfrom the titanium ore.

Figure 2 shows the flow diagram of the process used inthis study. As shown in Fig. 2, the process investigated in thisstudy consists of two selective chlorination processes. Oneselective chlorination process uses MgCl2 to chlorinate theiron in the titanium ore of the titanium ore/MgCl2 mixture.The other selective chlorination process uses HCl gasproduced from the titanium ore/MgCl2 mixture to chlorinatethe iron in the titanium ore. The selective chlorinationinvestigated in this study has the following advantages; (1) itdoes not involve handling of highly concentrated HCl or Cl2gas, (2) high purity titanium dioxide is obtained directly fromthe titanium ore in one step by a simple scalable methodunder Ar atmosphere, and (3) various types of titanium orecan be used as a feedstock.

2. Experimental

Figure 3 shows the schematic of the experimentalapparatus used in this study. MgCl2 (anhydrous; purity

²97.0%; granular; Wako Pure Chemical Industries, Ltd.) wasdried in a vacuum dryer (EYELA, VOS-201SD) for morethan 3 days at 473K before use. In addition, natural ilmeniteproduced in Vietnam, Australia and China were used asfeedstocks. The compositions of the titanium ores are shownin Table 1. The particle of titanium ore sample was separatedaccording to particle diameter using sieve before hightemperature experiments. The particle size ranged from 44to 149 µm was prepared by grinding and sieving the particlesize ranged from 149 to 210 µm before the experiments.

Before the experiments were carried out, a mixture ofMgCl2 and titanium ore was placed in the molybdenum-lined

Selective chlorination

Ilmenite (FeTiO3)MgCl2 H2O

MgTiO3 / MgOFeCl2 HCl

Selective chlorination

Ilmenite (FeTiO3) HCl

TiO2 FeCl2H2O

Titanium metal production

Ti metal

Chlorine recovery

TiCl4Fe

*

*

This study

HC

l rec

over

y

Ti scrap

Chlorinating agents

Fig. 2 Flow diagram of the selective chlorination process investigated inthe present study.

Mo-lined quartz crucible

Quartz wool

Quartz

Ti ore[Mo]

Quartz tube

Ti oreMgCl2

Heater

Electric furnace

Pump

Gas outlet

EmptyWaterMFC

Vacuum or Gas inlet

Gas outlet / Not used under vacuum and Ar atmosphere

Ar

Pressure gauge

Silicone rubber plug

Quartz crucible

Water bubbler used

under Ar + H2O gas

atmosphere only

Temp.controller

Thermocouple

Fig. 3 Schematic of the experimental apparatus used in the present study.

Table 1 Chemical compositions of titanium ores used in this study.

Source countryof titanium ore

Concentration of element i, Ci (mass%)*1

Ti Fe Al Si Ca Mn Zr Nb Mg

Vietnam*2 45.0 49.7 0.33 0.57 0.04 3.47 0.07 0.15 N.D.

Australia*3 48.5 46.7 1.02 1.00 0.07 1.69 0.18 0.18 N.D.

China*4 47.2 45.4 1.41 1.65 0.21 2.79 0.24 0.27 N.D.

*1Determined by XRF analysis (excluding oxygen and other gaseouselements), N.D.: Not Detected. Below the detection limit of the XRF(<0.01%), values are determined by average of analytical results of fivesamples.*2Natural ilmenite produced in Vietnam.*3Natural ilmenite produced in Australia.*4Natural ilmenite produced in China.

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride 1445

quartz crucible (quartz crucible: º = 26mm, I.D.; d =24mm, depth). In addition, the titanium ore was placed ina quartz crucible (º = 31mm, I.D.; d = 13mm, depth). Afterplacing the samples in the two crucibles, both crucibles wereplaced into the quartz tube (º = 41.5mm, I.D.; l = 545mm,length), and then an appropriate atmosphere was providedfor the samples in each experiment. The quartz tube wasthen placed in a horizontal furnace that was heated to up to1000K.

Table 2 shows the experimental conditions used in thepresent study. When the experiments were conducted undervacuum, the quartz tube was evacuated twice for 10min eachbefore the experiments. Ar gas (purity >99.9995%) wasfilled into the quartz tube between the evacuations until theinternal pressure was 1 atm.

When the experiments were conducted under Ar gasatmosphere, after evacuation (carried out as mentionedabove), Ar gas was filled until the internal pressure of thequartz tube was 1 atm. After the internal pressure of thequartz tube became 1 atm, the quartz tube was flowed with Argas at the rate of 50 sccm via a mass flow controller (MFC),while maintaining the internal pressure of the quartz tube at1 atm during experiments.

When the experiments were conducted under Ar + H2Ogas atmosphere, water in a bubbler was bubbled with Ar gasfor 30min to remove the dissolved oxygen. After pretreatmentof the water, the quartz tube was filled with Ar gas until theinternal pressure of the tube reached 1 atm after the evacuationprocedure. Subsequently, Ar gas was injected through thewater bubbler and the gas flow rate was maintained at 50 sccmby the MFC, while the internal pressure of the quartz tube wasmaintained at 1 atm. The temperature of the water in the

bubbler was controlled by using a mantle heater (Model No.:HF-200S, As One Co.) and maintained at 303K.

After a preset reaction time, the quartz tube was instantlytaken out of the furnace and cooled down at roomtemperature. The residues in the quartz crucible wereanalyzed without subjecting the samples to any leachingprocess. However, the residues in the molybdenum-linedquartz crucible were dissolved in deionized water for twohours by sonication at room temperature and then leachedin 20% HCl aqueous solution for 30min with stirring at therate of 300 rpm at room temperature.

The compositions of the residues obtained in bothcrucibles were analyzed using X-ray fluorescence spectrosco-py (XRF: JEOL, JSX-3100RII), their microstructures andcompositions were analyzed using scanning electron mi-croscopy/energy dispersive X-ray spectroscopy (SEM/EDS:JEOL, JSM-6510LV), and their crystalline phases wereidentified using X-ray diffraction (XRD: RIGAKU, RINT2500, Cu­K¡ radiation) analysis.

3. Mechanism of Selective Chlorination

To understand the mechanism of the selective chlorinationthermodynamically, FeTiO3 is assumed as a mixture of FeOand TiO2. This assumption is acceptable from a thermody-namic viewpoint and is used in several studies because theGibbs energy of formation of FeTiO3 is a small negativevalue as shown in eq. (1).

FeOðsÞ þ TiO2ðsÞ ¼ FeTiO3ðsÞ;�G�

r ¼ �12 kJ at 1000K34Þ ð1ÞFigures 4 and 5 show the chemical potential diagrams of

the Fe­O­Cl system and the Ti­O­Cl system at 1000K,respectively, and the abscissa, pCl2 , is the chemical potentialof chlorine gas and the ordinate, pO2

, is the chemicalpotential of oxygen gas. In addition, the authors provideFig. 6, which was constructed by overlapping the chemicalpotential diagram of Fe­O­Cl system and that of the Ti­O­Clsystem shown in Figs. 4 and 5, respectively. Any point in thehatched area shown in Fig. 6 belongs to the stability regionof TiO2(s) and FeCl2(l), or TiO2(s) and FeCl3(g). The vaporpressure of FeCl2(l) at 1000K is 0.02 atm, which is highenough to evaporate FeCl2(l).34) As a result, thermodynami-cally, if the chemical potentials of oxygen and chlorine arepositioned in the hatched area shown in the Fig. 6, the ironoxides can be removed as gaseous iron chlorides and solidtitanium dioxide can be obtained as a result of the selectivechlorination process.

In this study, MgCl2 was used as the chlorinating agent.Even though MgCl2 was dried in the vacuum oven prior touse, absorption of H2O from air is expected to occur duringexperimental preparation owing to the hygroscopicity of theMgCl2. Therefore, eq. (2) is to be considered in this reactionsystem.

MgCl2ðlÞ þ H2OðgÞ ¼ MgOðsÞ þ 2 HClðgÞ;�G�

r ¼ �19 kJ at 1000K34Þ ð2ÞAs shown in eq. (2), if H2O exists in the system, HCl gas

can be produced from MgCl2 at 1000K in the molybdenum-lined quartz crucible. In addition, it is easy to obtain HCl gas

Table 2 Experimental conditions used in the present study.

Exp.No.*

Sourcecountryof Ti ore

Reactiontime,trA/h

Atmosphere H2O bubbler Particle sizein the quartzcrucible,dore/µm

GasFlow,f/sccm

UseTemp.,Tbub/K

121017 Vietnam 5 Vacuum ® ® ® 44­74

121030 Vietnam 5 Vacuum ® ® ® 74­149

121031 Vietnam 5 Vacuum ® ® ® 149­210

121101 Vietnam 5 Vacuum ® ® ® 210­297

121020 Australia 5 Vacuum ® ® ® 44­74

121029 China 5 Vacuum ® ® ® 44­74

121119 Vietnam 3 Ar 50 ® ® 44­74

121118 Vietnam 5 Ar 50 ® ® 44­74

121117 Vietnam 7 Ar 50 ® ® 44­74

121114 Vietnam 9 Ar 50 ® ® 44­74

121113 Vietnam 11 Ar 50 ® ® 44­74

121216 Vietnam 1 Ar 50 O 303 44­74

121215 Vietnam 3 Ar 50 O 303 44­74

121212 Vietnam 5 Ar 50 O 303 44­74

121211 Vietnam 7 Ar 50 O 303 44­74

*Experimental conditions;Weight of titanium ore used in the quartz crucible, wore = 0.10 g.Weight of titanium ore used in the Mo-lined quartz crucible,wore = 0.25 g.Weight of MgCl2 used in the Mo-lined quartz crucible, wMgCl2 ¼ 3:00 g.Particle size used in the Mo-lined quartz crucible, dore = 74­149µm.Reaction temperature, T = 1000K.

J. Kang and T. H. Okabe1446

from MgCl2 when H2O is introduced in the reaction system.On the basis of this reason, a water bubbler was used in thisstudy for intentionally introducing H2O vapor into the quartztube to accelerate the production of HCl gas according to theeq. (2). The partial pressure of H2O vapor introduced into thequartz tube could be fixed at 0.04 atm by using the waterbubbler at 303K.

The lines corresponding to the H2O(g)/HCl(g) eq.d andH2O(g)/HCl(g) eq.e in Fig. 6 can be derived from eq. (3) byconsidering the reaction shown in eq. (2). If MgO remains asa solid in MgCl2(l) after the experiments, the activity ofMgO(s) (aMgO) is unity, and then H2O(g)/HCl(g) eq.e underMgO(s)/MgCl2(l) eq.a dominates the reactions in the system.Meanwhile, if the solubility of MgO(s) in the MgCl2(l) at1000K is high enough, or if all of MgO(s) reacts with TiO2(s)in titanium ore, the activity of MgO(s) is decreased byforming MgTiO3(s) as shown in eq. (4), and H2O(g)/HCl(g)eq.d under TiO2(s)/MgTiO3(s)/MgCl2(l) eq. dominates thereactions in the system. If the activity of the reaction productMgO(s) is decreased in the system, MgCl2 becomes astronger chlorinating agent. It is worth noting that both linescorresponding to the H2O(g)/HCl(g) eq.d and H2O(g)/HCl(g)eq.e in Fig. 6 pass through the stability region of FeCl2(l) inthe hatched region. Therefore, iron in the titanium ore can beselectively removed from the ore directly as FeCl2(l,g) in thequartz crucible by the reaction shown in eq. (5). In addition,the reaction shown in eq. (2) proceeds further by the H2Oproduced according to the reaction shown in eq. (5). BothH2O and HCl gas act as reaction mediators of chlorinationwhen MgCl2 (+H2O) is used as the chlorinating agent.

logpO2¼ 2 logpCl2 þ 2 logpH2O � 4 logpHCl

þ 4 logKfðHClÞ � 2 logKfðH2OÞ ð3ÞMgOðsÞ þ TiO2ðs, FeTiO3Þ ¼ MgTiO3ðsÞ ð4Þ

aMgO ¼ 0:054 at 1000K when aTiO2¼ 1 and aMgTiO3

¼ 134Þ

FeOðsÞ þ 2 HClðgÞ ¼ FeCl2ðlÞ þ H2OðgÞ;�G�

r ¼ �3:8 kJ at 1000K34Þ ð5Þ

Ti-O-Cl system, T = 1000 K

-20 -15 -10 -5 0-60

-50

-40

-30

-20

-10

0

Chlorine partial pressure, log pCl

2

(atm)

Oxy

gen

part

ial p

ress

ure,

log

p O2

(atm

)

TiO2(s)

/ M

gTiO 3

(s) /

MgC

l 2(l)

eq.

extr

apola

ted

H 2O(g

) / H

Cl(g) e

q.d ex

trapo

lated

Ti (s)

TiO (s)

Ti2O

3 (s)

Ti3O

5 (s)

Ti4O

7 (s)

TiO2 (s)

TiCl4 (g)

TiCl3 (s)

TiCl2 (s)

H2O(g) / HCl(g) eq.e

MgO(s) / MgCl2(l) eq.a

TiO2(s) / MgTiO

3(s)

/ MgCl2(l) eq.

C (s) / CO (g) eq.cCO (g) / CO

2 (g) eq.c

H2O(g) / HCl(g) eq.a

H2O(g) / HCl(g) eq.d

e : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO under a

MgO = 1

d : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO

under aMgO

= 0.054 (under TiO2(s)/MgTiO

3(s) eq.)

c : pCl

2

= 0.1 atm

a : standrad state b : pH

2O / p

H2

= 1

b

Fig. 5 Chemical potential diagram of the Ti­O­Cl system at 1000K.34)

Fe-O-Cl system, T = 1000 KTi-O-Cl system,

-20 -15 -10 -5 0-60

-50

-40

-30

-20

-10

0

e : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO under a

MgO = 1

Potential region forselective chlorination

Chlorine partial pressure, log pCl

2

(atm)

Oxy

gen

part

ial p

ress

ure,

log

p O2

(atm

)

Fe (s)

FeO (s)

Fe3O

4 (s)

Fe2O

3 (s)

FeCl2 (l)

FeCl3 (g)

H 2O(g

) / H

Cl(g) e

q.d ex

trapo

lated

TiO 2

(s) /

MgT

iO 3(s

) / M

gCl 2(l)

eq.

extr

apola

ted

TiO2 (s)

Ti3O

5 (s)

Ti4O

7 (s)

Ti2O

3 (s)

TiO (s)

Ti (s)

TiCl4 (g)

TiCl3 (s)

TiCl2 (s)

Fe-O-ClTi-O-Cl

d : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO

under aMgO

= 0.054 (under TiO2(s)/MgTiO

3(s) eq.)

c : pCl

2

= 0.1 atm

a : standard state b : pH

2O / p

H2

= 1

H2O(g) / HCl(g) eq.e

MgO(s) / MgCl2(l) eq.a

TiO2(s) / MgTiO

3(s)

/ MgCl2(l) eq.

C (s) / CO (g) eq.cCO (g) / CO

2 (g) eq.c

H2O(g) / HCl(g) eq.a

H2O(g) / HCl(g) eq.d

b

Fig. 6 Combined chemical potential diagram of the Fe­O­Cl system (solidline) and the Ti­O­Cl system (dotted line) at 1000K.34)

Fe-O-Cl system, T = 1000 K

-20 -15 -10 -5 0-60

-50

-40

-30

-20

-10

0

e : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO under a

MgO = 1

H2O(g) / HCl(g) eq.e

MgO(s) / MgCl2(l) eq.a

H 2O(g

) / H

Cl(g) e

q.d ex

trapo

lated

TiO 2

(s) /

MgT

iO 3(s

) / M

gCl 2(l)

eq.

extr

apola

ted

Chlorine partial pressure, log pCl

2

(atm)

Oxy

gen

part

ial p

ress

ure,

log

p O2

(atm

)

Fe (s)

FeO (s)

Fe3O

4 (s)

Fe2O

3 (s)

FeCl2 (l)

FeCl3 (g)

TiO2(s) / MgTiO

3(s)

/ MgCl2(l) eq.

C (s) / CO (g) eq.cCO (g) / CO

2 (g) eq.c

d : pH

2O / p

HCl

2 : Determined by MgCl2 + H

2O = 2 HCl + MgO

under aMgO

= 0.054 (under TiO2(s)/MgTiO

3(s) eq.)

c : pCl

2

= 0.1 atm

a : standrad state b : pH

2O / p

H2

= 1

H2O(g) / HCl(g) eq.a

H2O(g) / HCl(g) eq.d

b

Fig. 4 Chemical potential diagram of the Fe­O­Cl system at 1000K.34)

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride 1447

MgCl2 by itself can act as the chlorinating agent if it isused in reaction with the titanium ore through physicalcontact. Both lines corresponding to the MgO(s)/MgCl2(l)eq.a and TiO2(s)/MgTiO3(s)/MgCl2(l) eq. in Fig. 6 also passthrough the stability region of FeCl2(l) in the hatched region.The line corresponding to the MgO(s)/MgCl2(l) eq.a

considered the standard state, which means that the activityof MgO(s) produced in the molybdenum-lined quartzcrucible is unity. The reaction under MgO(s)/MgCl2(l) eq.a

is shown in eq. (6). The line corresponding to the TiO2(s)/MgTiO3(s)/MgCl2(l) eq. considered MgTiO3(s) productionduring chlorination, and the reaction under TiO2(s)/MgTiO3(s)/MgCl2(l) eq. is shown in eq. (7). In both cases,iron can be selectively removed from titanium ore directly asFeCl2(l,g) in the molybdenum-lined quartz crucible.

FeOðsÞ þMgCl2ðlÞ ¼ FeCl2ðlÞ þMgOðsÞ;�G�

r ¼ �23 kJ at 1000K34Þ ð6ÞFeOðsÞ þ TiO2ðsÞ þMgCl2ðlÞ ¼ FeCl2ðlÞ þMgTiO3ðsÞ;�G�

r ¼ �47 kJ at 1000K34Þ ð7Þ

4. Results and Discussion

4.1 Observations after the experimentsFigure 7 shows the representative photographs of the

experimental apparatus after the experiments. As shown inFig. 7(a), a white deposit was found inside the low temper-ature portion of the quartz tube. In addition, the black color ofthe reactant titanium ore changed to bright grey color in theproduct residues, as shown in Fig. 7(b). The results of theXRD analysis of the white powder shown in Fig. 8 indicatedthat the white deposit was FeCl2 and FeCl2·(H2O)2, asexpected from the thermodynamic calculations mentionedbefore. The vapor pressure of FeCl2(l) produced from thequartz crucible and molybdenum-lined quartz crucible is0.02 atm at 1000K, which was sufficient to induce itsevaporation. Therefore, FeCl2(l) evaporated from the bothcrucibles and solidified in the low temperature regions of thequartz tube. The H2O present in the FeCl2 might haveoriginated from the H2O produced in the quartz crucible orfrom the air when the silicone rubber plug was removed fromthe quartz tube during sample preparation for XRD analysis.

4.2 Influence of atmosphere on the selective chlorinationTable 3 shows the results of XRF analysis of the residues

obtained in the quartz crucible and the molybdenum-linedquartz crucible. Figures 9 and 10 show the XRD patternsof the residues obtained in the quartz crucible and themolybdenum-lined quartz crucible when the experimentswere conducted under Ar gas or Ar + H2O gas atmosphere,respectively.

As shown in Table 3, Fig. 9(a) and Fig. 10(a), a purity ofabout 97% TiO2 was obtained in the quartz crucible when theexperiments were conducted under Ar gas or Ar + H2O gasatmosphere for 11 or 7 h, as expected from the thermody-namic calculation. A purity of TiO2 was calculated byconverting all elements in Table 3 to its nominal simpleoxides. In addition, when the water bubbler was used in theexperiments, the reaction time required for obtaining highpurity TiO2 decreased. As shown in Table 3, the amount of

iron removed from the titanium ore was greater when theexperiments were conducted under Ar + H2O gas atmos-phere than when the experiments were conducted under Aratmosphere for equal reaction time. The reduction in thereaction time can be attributed to the active introduction ofH2O vapor into the reaction system by using water bubbler,which led to the accelerated production of HCl gas from theMgCl2 in the molybdenum-lined quartz crucible.

Among the impurities present in the titanium ore, MnO(s)can be removed by HCl gas by the reaction shown in theeq. (8). Table 3 shows that the concentration of Mn in theresidues obtained in the quartz crucible decreased as thereaction time increased when the experiments were con-ducted under Ar gas or Ar + H2O gas atmosphere. Inaddition, the concentration of Mg in the residues obtainedin the quartz crucible could not be assessed for all cases.Although the vapor pressure of MgCl2 at 1000K is as lowas 0.0003 atm, MgCl2 can evaporate depending on theatmosphere, such as in vacuum. Based on the results of theconcentration of Mg listed in Table 3, the authors inferredthat there was no reaction through gas phase or negligible

(a)

(b) (c)

Fig. 7 Photographs of the experimental apparatus after the experiment:(a) the quartz tube, (b) residue in the quartz crucible, and (c) residue in themolybdenum-lined quartz crucible.

10 20 30 40 50 60 70 80 90

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

FeCl2 (H2O)2 : PDF #01-072-0268

FeCl2 : PDF #01-089-3732

The residues condensed inside the low temperature part of the quartz tube

Background

Fig. 8 Results of the XRD analysis of the white deposit condensed in thelow temperature portion of the quartz tube.

J. Kang and T. H. Okabe1448

Table 3 Analytical results of the residues obtained in the quartz crucible and the molybdenum-lined quartz crucible: Influence of atmosphere on selectivechlorination at 1000K.

Exp. No.*2

H2O bubblerReaction time,

trA/h

Quartz crucible Mo-lined quartz crucible

Concentration of Concentration of

UseTemp.,Tbub/K

element i, Ci (mass%)*1 element i, Ci (mass%)*1

Ti Fe Mn Mg Ti Fe Mn Mg

121119 ® ® 3 73.0 23.4 2.30 N.D. 61.3 18.0 1.25 18.3

121118 ® ® 5 83.2 13.9 1.47 N.D. 58.5 19.3 1.14 19.8

121117 ® ® 7 92.1 5.88 0.70 N.D. 58.4 19.8 0.98 19.3

121114 ® ® 9 94.4 3.67 0.44 N.D. 62.5 19.1 1.96 15.3

121113 ® ® 11 96.7 1.77 0.14 N.D. 63.4 18.1 1.12 15.5

121216 O 303 1 61.0 35.1 2.94 N.D. 57.8 26.6 1.61 12.7

121215 O 303 3 77.7 19.6 1.94 N.D. 55.9 23.4 1.24 18.0

121212 O 303 5 90.9 7.23 0.98 N.D. 56.6 20.7 1.23 19.9

121211 O 303 7 97.2 1.24 0.13 N.D. 57.1 19.4 1.25 20.5

*1Determined by XRF analysis (excluding oxygen and other gaseous elements), N.D.: Not Detected. Below the detection limit of the XRF (<0.01%),values are determined by average of analytical results of five samples.*2Experimental conditions;Weight of titanium ore used in the quartz crucible, wore = 0.10 g.Weight of titanium ore used in the Mo-lined quartz crucible, wore = 0.25 g.Weight of MgCl2 used in the Mo-lined quartz crucible, wMgCl2 ¼ 3:00 g.Particle size used in the quartz crucible, dore = 44­74µm.Particle size used in the Mo-lined quartz crucible, dore = 74­149µm.Reaction temperature, T = 1000K.Source country of titanium ore: Vietnam.Ar gas was flowed through the quartz tube at a rate of 50 sccm via mass flow controller while the internal pressure of the quartz tube was maintained at1 atm during the experiments.

Angle, 2θ (deg.)

Inte

nsity

, I (

a.u.

)

Residue in the Mo-lined crucible(Exp. No. : 121113)

Residue in the Mo-lined crucible(Exp. No. : 121114)

Residue in the Mo-lined crucible(Exp. No. : 121117)

Residue in the Mo-lined crucible(Exp. No. : 121118)

Residue in the Mo-lined crucible(Exp. No. : 121119)

(5)

(4)

(3)

(2)

(1)

MgTiO3 : PDF #00-006-0494

TiO2 : PDF #00-021-1276

FeTiO3 : PDF #01-089-2811

10 20 30 40 50 60 70 80 90

MgO : PDF #01-087-0651(b)

10 20 30 40 50 60 70 80 90

Angle, 2θ (deg.)

Inte

nsity

, I (

a.u.

)

TiO2 : PDF #03-065-0191

FeTiO3 : PDF #01-075-1208

Residue in the quartz crucible(Exp. No. : 121113)

Residue in the quartz crucible(Exp. No. : 121114)

Residue in the quartz crucible(Exp. No. : 121117)

Residue in the quartz crucible(Exp. No. : 121118)

(4)

(3)

(2)

(1)

Residue in the quartz crucible(Exp. No. : 121119)

(5)

(a)

tr' = 3 h

tr' = 5 h

tr' = 7 h

tr' = 9 h

tr' = 11 h

tr' = 11 h

tr' = 9 h

tr' = 7 h

tr' = 5 h

tr' = 3 h

Fig. 9 (a) XRD patterns of the residues obtained in the quartz crucible when the experiments were conducted under Ar gas atmosphere:(1) 11 h, (2) 9 h, (3) 7 h, (4) 5 h and (5) 3 h. (b) XRD patterns of the residues obtained in the molybdenum-lined quartz crucible when theexperiments were conducted under Ar gas atmosphere: (1) 11 h, (2) 9 h, (3) 7 h, (4) 5 h and (5) 3 h.

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride 1449

reaction between MgCl2 in the molybdenum-lined quartzcrucible and the titanium ore in the quartz crucible.

1=2 MnOðsÞ þ HClðgÞ ¼ 1=2 MnCl2ðlÞ þ 1=2 H2OðgÞ;�G�

r ¼ �17 kJ at 1000K34Þ ð8ÞFigure 11 shows the SEM images of the Vietnamese

titanium ore before experiment and the residue obtained inthe quartz crucible when the experiment was conducted underAr gas atmosphere for 11 h. As shown in Fig. 11, pores weregenerated on the surface of the residue after the experiment.These results show that iron was selectively removed fromtitanium ore as FeCl2(l,g) leaving pores on the surface of theresidues in the quartz crucible because of the high vaporpressure of FeCl2 at 1000K. As a result, it can be expectedthat the HCl gas produced from the MgCl2 could react withiron in the central portion of the titanium ore particle throughthe generated pores.

As shown in Figs. 9(b) and 10(b), the crystalline phasesof the residues obtained in the molybdenum-lined quartzcrucible were MgTiO3 and MgO. Despite the presence ofcrystalline phase of MgTiO3 in the residues revealed by theXRD analysis, the crystalline phase of MgO was also foundin the residues present in the molybdenum-lined quartzcrucible after the experiments. The most intense peakcorresponded to MgO in most cases. These results showthat the lines corresponding to the H2O(g)/HCl(g) eq.e andMgO(s)/MgCl2(l) eq.a dominated the reactions that occurredin the quartz crucible and molybdenum-lined quartz crucible,respectively, when the experiments were conducted under Argas or Ar + H2O gas atmosphere.

Even though the iron was sufficiently removed leaving 1.2or 1.8% in the titanium ore in the quartz crucible, about 18 or19% of iron remained in the titanium ore present in the

molybdenum-lined quartz crucible when the experimentswere conducted under Ar gas or Ar + H2O gas atmospherefor 11 or 7 h, respectively. Figure 12 shows the SEM imageand results of the EDS of a cross section of the residueobtained from the molybdenum-lined quartz crucible. As

10 20 30 40 50 60 70 80 90

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

TiO2 : PDF #01-073-1232

FeTiO3 : PDF #01-075-1203

Residue in the quartz crucible(Exp. No. : 121211)

Residue in the quartz crucible(Exp. No. : 121212)

Residue in the quartz crucible(Exp. No. : 121215)

Residue in the quartz crucible(Exp. No. : 121216)

(4)

(3)

(2)

(1)

(a)

Angle, 2θ (deg.)10 20 30 40 50 60 70 80 90

MgTiO3 : PDF #01-079-0831

MgO : PDF #01-075-0447

FeTiO3 : PDF #01-071-1140

TiO2 : PDF #01-076-0649

Inte

nsity

, I (

a.u.

)

Residue in the Mo-lined crucible(Exp. No. : 121211)

(1)

(2) Residue in the Mo-lined crucible(Exp. No. : 121212)

Residue in the Mo-lined crucible(Exp. No. : 121215)

(3)

(4) Residue in the Mo-lined crucible(Exp. No. : 121216)

r

r

(b)

tr' = 7 h

tr' = 5 h

tr' = 3 h

tr' = 1 h

tr' = 7 h

tr' = 5 h

tr' = 3 h

tr' = 1 h

Fig. 10 (a) XRD patterns of the residues obtained in the quartz crucible when the experiments were conducted under Ar + H2O gasatmosphere: (1) 7 h, (2) 5 h, (3) 3 h and (4) 1 h. (b) XRD patterns of the residues obtained in the molybdenum-lined quartz crucible whenthe experiments were conducted under Ar + H2O gas atmosphere: (1) 7 h, (2) 5 h, (3) 3 h and (4) 1 h.

(a)

(b)

5μm

5μm

Fig. 11 SEM images of the microstructure: (a) the Vietnamese titanium orebefore experiment, and (b) the residue in the quartz crucible when theexperiment was conducted under Ar gas atmosphere (Exp No.: 121113).

J. Kang and T. H. Okabe1450

shown in Fig. 12, the reaction between MgCl2 and the centralportion of the titanium ore particle was hindered because ofthe production of MgTiO3 at the outer portion of the titaniumore particle. Therefore, iron was partially removed from thetitanium ore in the molybdenum-lined quartz crucible.

4.3 Influence of the particle size of the titanium ore onselective chlorination

Table 4 shows the results of analyzing the residuesobtained in the quartz crucible and the molybdenum-linedquartz crucible, and Figs. 13(a) and 13(b) show the XRDpatterns of the residues obtained in the quartz crucible andthe molybdenum-lined quartz crucible, respectively, whenvarious sizes of Vietnamese titanium ore were used as afeedstock under vacuum.

As shown in Table 4 and Fig. 13(a), a purity of about 97%TiO2 was obtained in the quartz crucible when the particlesize ranged from 44 to 297 µm. It is certain that the HCl gasproduced from the molybdenum-lined quartz crucible couldreact with the entire volume of the titanium ore particlethrough the pores generated by the reaction between HCl gasand iron. Therefore, according to these results, the selectivechlorination reaction that occurred in the quartz crucible didnot depend on the particle size of the titanium ore.

It was also reconfirmed that the concentration of Mn in theresidues obtained in the quartz crucible decreased because ofthe reaction shown in the eq. (8) for all the particle sizeranges. However, the concentration of 1.1­1.2% Mg in theresidues obtained in the quartz crucible was analyzed whenthe experiments were conducted under vacuum, while the

concentration of Mg in the residues obtained in the quartzcrucible could not be detected when the experiments wereconducted under Ar gas atmosphere. In addition, a weakintensity peak of MgTiO3 was identified, as shown inFig. 13(a). These results show that even though the vaporpressure of the MgCl2 is low as 0.0003 atm at 1000K, aportion of MgCl2 evaporated from the molybdenum-linedquartz crucible reacted with the titanium ore in the quartzcrucible under vacuum.

As shown in Table 4 and Fig. 13(b), about 22­25% of ironremained and MgO and MgTiO3 were produced in themolybdenum-lined quartz crucible. It is expected that iron inthe center of the titanium ore particle does not react with theMgCl2 due to the formation of MgTiO3 at the outer part ofthe titanium ore particle, similar to the case shown in theFig. 12. In addition, MgO(s) found in the molybdenum-linedquartz crucible also shows that the lines corresponding to theH2O(g)/HCl(g) eq.e and MgO(s)/MgCl2(l) eq.a dominatedthe reactions that occurred in the quartz crucible andmolybdenum-lined quartz crucible, respectively.

4.4 Various kinds of the titanium ores produced inseveral countries

Table 5 shows the results of analyzing the residuesobtained in the quartz crucible and the molybdenum-linedquartz crucible, and Figs. 14(a) and 14(b) show the XRDpatterns of the residues obtained in the quartz crucible andthe molybdenum-lined quartz crucible when the Australiantitanium ore and the Chinese titanium ore were used as afeedstock, respectively.

As shown in Table 5 and Fig. 14(a), a purity of about 92%TiO2 was obtained in the quartz crucible. The purity of TiO2

obtained was lower than that obtained when the Vietnamesetitanium ore was used as the feedstock. As shown in eq. (8),Mn in the titanium ore can be removed by HCl gas producedfrom the molybdenum-lined quartz crucible. However, it is

1 3 5 7 9 110

10

20

30

40

50

Mg Ti Fe

Com

posi

tion

i, C

i (m

ass

%)

Position No.

Position No. 1 Position No. 12

50 μm

(a)

(b)

Fig. 12 (a) SEM image of the cross section of the residue obtained fromthe molybdenum-lined quartz crucible (Exp. No.: 121117). (b) Corre-sponding EDS results of the cross section of the residue obtained from themolybdenum-lined quartz crucible (Exp. No.: 121117).

Table 4 Analytical results of residues obtained in the quartz crucible andthe molybdenum-lined quartz crucible: Influence of the particle size of thetitanium ore on selective chlorination at 1000K.

Exp.No.*2

Quartz crucible Mo-lined quartz crucible

Particlesize,

dore/µm

Concentration ofelement i,

Ci (mass%)*1Particlesize,

dore/µm

Concentration ofelement i,

Ci (mass%)*1

Ti Fe Mn Mg Ti Fe Mn Mg

121017 44­74 96.8 0.60 0.06 1.12 74­149 54.1 21.9 1.15 21.0

121030 74­149 96.9 0.53 0.07 1.11 74­149 53.9 24.6 1.56 18.6

121031 149­210 96.9 0.61 0.08 1.16 74­149 50.2 24.2 1.49 22.6

121101 210­297 96.6 0.59 0.06 1.28 74­149 53.2 23.0 1.47 20.7

*1Determined by XRF analysis (excluding oxygen and other gaseouselements), values are determined by average of analytical results of fivesamples.*2Experimental conditions;Weight of titanium ore used in the quartz crucible, wore = 0.10 g.Weight of titanium ore used in the Mo-lined quartz crucible,wore = 0.25 g.Weight of MgCl2 used in the Mo-lined quartz crucible, wMgCl2 ¼ 3:00 g.Reaction time, trA = 5 h.Reaction temperature, T = 1000K.Source country of titanium ore: Vietnam.Experiments were conducted under vacuum.

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride 1451

difficult to remove other impurities such as Al, Si, Zr and Nbin the titanium ore by HCl gas, as shown in eqs. (9) and (10).The amount of these impurities in the Australian titanium oreand the Chinese titanium ore are larger than the amount of theimpurities in the Vietnamese titanium ore as shown inTable 1. When comparing the purity of residues obtained inthe quartz crucible, the purity of the residue obtained fromthe Australian and the Chinese titanium ores (92 and 92%TiO2) was lower than that of the residue obtained from the

Vietnamese titanium ore (97% TiO2). In practice, thisdifference is unimportant because a purity of 92% TiO2 issufficient for application of the Kroll process.

1=6 Al2O3ðsÞ þ HClðgÞ ¼ 1=3 AlCl3ðlÞ þ 1=2 H2OðgÞ;�G�

r ¼ 62 kJ at 1000K34Þ ð9Þ1=4 SiO2ðsÞ þ HClðgÞ ¼ 1=4 SiCl4ðgÞ þ 1=2 H2OðgÞ;�G�

r ¼ 54 kJ at 1000K34Þ ð10Þ

5. Conclusions

The authors have considered the use of MgCl2 as thechlorinating agent to develop a selective chlorination processfor producing high purity titanium dioxide by upgrading low-grade titanium ore containing 51% TiO2. Iron was removedfrom the titanium ore as FeCl2(l,g) by the HCl gas producedfrom the MgCl2/titanium ore mixture at 1000K in the quartzcrucible and TiO2 with purity of 97% was obtained when theexperiments were conducted under Ar gas or Ar + H2O gasatmosphere. The time required for the completion of thereaction was decreased when the experiments were con-ducted under Ar + H2O gas atmosphere because of theaccelerated production of HCl gas.

The authors also demonstrated the direct production of97% TiO2 from the Vietnamese titanium ore that containedparticles of sizes ranging from 44 to 297 µm by using the HClgas produced from MgCl2/titanium ore mixture. In addition,when the Australian or the Chinese titanium ores were usedas the feedstock, 92% TiO2 was obtained. This was attributedto the presence of impurities like Al or Si in the titanium orethat were difficult to remove by HCl gas.

The iron present in the titanium ore was also removed asFeCl2(l,g) by the direct reaction between MgCl2 and the

dore

=

210 - 297 μm

TiO2(rutile)

10 20 30 40 50 60 70 80 90

: PDF #03-065-0191

MgTiO3 : PDF #01-079-0831

Residue in the quartz crucible(Exp. No. : 121017)

Residue in the quartz crucible(Exp. No. : 121030)

Residue in the quartz crucible(Exp. No. : 121031)

(3)

(2)

(1)

Residue in the quartz crucible(Exp. No. : 121101)

(4)

dore

=

149 - 210 μm

dore

=

74 - 149 μm

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

dore

=

44 - 74 μm

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

MgTiO3 : PDF #01-079-0831

MgO : PDF #01-074-1225

FeTiO3 : PDF #01-075-1211

TiO2 : PDF #03-065-1118

Residue in the Mo-lined crucible(Exp. No. : 121017)

Residue in the Mo-lined crucible(Exp. No. : 121030)

Residue in the Mo-lined crucible(Exp. No. : 121031)

Residue in the Mo-lined crucible(Exp. No. : 121101)

dore

=

210 - 297 μm

(3)

(2)

(1)

(4)

dore

=

149 - 210 μm

dore

=

74 - 149 μm

dore

=

44 - 74 μm

(b)

Fig. 13 (a) XRD patterns of the residues obtained in the quartz crucible when the ore particle size was in the range: (1) 44­74µm, (2) 74­149µm, (3) 149­210µm and (4) 210­297µm. (b) XRD patterns of the residues obtained in the molybdenum-lined quartz crucible whenthe ore particle size was in the range: (1) 44­74µm, (2) 74­149µm, (3) 149­210µm and (4) 210­297µm.

Table 5 Analytical results of residues obtained in the quartz crucible andthe molybdenum-lined quartz crucible: Various types of the titanium oresproduced in several countries at 1000K.

Exp.No.*2

Sourcecountryof Ti ore

Quartz crucibleMo-lined quartz

crucible

Concentration ofelement i,

Ci (mass%)*1

Concentration ofelement i,

Ci (mass%)*1

Ti Fe Mn Mg Al Si Ti Fe Mn Mg

121020 Australia 92.2 2.27 0.14 1.80 0.74 1.17 62.8 21.1 0.54 13.2

121029 China 91.7 2.62 0.10 1.47 0.93 1.21 50.9 19.1 0.72 25.5

*1Determined by XRF analysis (excluding oxygen and other gaseouselements), values are determined by average of analytical results of fivesamples.*2Experimental conditions;Weight of titanium ore used in the quartz crucible, wore = 0.10 g.Weight of titanium ore used in the Mo-lined quartz crucible,wore = 0.25 g.Weight of MgCl2 used in the Mo-lined quartz crucible, wMgCl2 ¼ 3:00 g.Particle size used in the quartz crucible, dore = 44­74µm.Particle size used in the Mo-lined quartz crucible, dore = 74­149µm.Reaction temperature, T = 1000K.Reaction time, trA = 5 h.Experiments were conducted under vacuum.

J. Kang and T. H. Okabe1452

titanium ore. However, when the MgCl2 directly reacted withthe titanium ore, 18­25% of iron remained in the titanium orebecause of the formation of MgTiO3 at the outer part of thetitanium ore, which hindered further reaction between MgCl2and iron present at the central portion of the titanium oreparticle, physically.

Acknowledgements

The authors are grateful to Professor Tetsuya Uda, KyotoUniversity; Professors Kazuki Morita and Takeshi Yoshikawa,The University of Tokyo; Professor Ryosuke O. Suzuki,Hokkaido University; and Messrs. Susumu Kosemura,Masanori Yamaguchi and Yuichi Ono, Toho Titanium Co.,Ltd., for their valuable suggestions and for supplying samplesthat were used throughout this research. Furthermore, theauthors thank Dr. Katsuhiro Nose, Dr. Yuki Taninouchi, Dr.Hideaki Sasaki and Mr. Hisao Kimura for their valuablesuggestions and technical assistance. The authors would liketo specially thank Professor Haiyan Zheng of NortheasternUniversity and Mr. Ryosuke Matsuoka of Global AdvancedMetals Pty., Ltd., for providing useful information and results

of their preliminary studies. This research was partly fundedby a Grant-in-Aid for the Next Generation of World-LeadingResearchers (NEXT Program). Jungshin Kang is grateful forthe financial support provided by the MEM (Mechanical,Electrical and Materials Engineering) International GraduateProgram from the Ministry of Education, Culture, Sports,Science and Technology, Japan (MEXT).

REFERENCES

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Sozai 109 (1993) 1157­1163.4) K. Faller and F. H. Froes: JOM 53 (2001) 27­28.5) F. H. Froes, H. Friedrich, J. Kiese and D. Bergoint: JOM 56 (2004)

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7) G. M. Bedinger: Mineral Commodity Summaries: Titanium MineralConcentrates, U.S. Geological Survey, Washington, DC, January,(2013) pp. 174­175, http://minerals.usgs.gov/minerals/pubs/commodity/titanium/mcs-2013-timin.pdf.

8) D. Filippou and G. Hudon: JOM 61 (2009) 36­42.9) T. S. Mackey: JOM 46 (1994) 59­64.10) R. G. Becher, R. G. Canning, B. A. Goodheart and S. Uusna: Proc.

Aust. Inst. Min. Metall. 21 (1965) 21­44.11) W. Hoecker: European Patent EP0612854, (1994).12) J. H. Chen and L. W. Huntoon: United States Patent 4019898, (1977).13) J. H. Chen: United States Patent 3967954, (1976).14) J. H. Chen: United States Patent 3825419, (1974).15) M. Guéguin and F. Cardarelli: Miner. Process. Extr. Metall. Rev. 28

(2007) 1­58.16) M. K. Akhtar, S. Vemury and S. E. Pratsinis: AIChE J. 40 (1994) 1183­

1192.17) W. Kroll: Trans. Electrochem. Soc. 78 (1940) 35­47.18) T. Iida: Kinzoku 82 (2012) 218­221.19) Y. Ito: Titan 60 (2012) 212­218.20) The Japan Titanium Society: Titan 61 (2013) 84.21) W. Zhang, Z. Zhu and C. Y. Cheng: Hydrometallurgy 108 (2011) 177­

188.22) K. I. Rhee and H. Y. Sohn: Metall. Mater. Trans. B 21 (1990) 341­347.23) S. Fukushima and E. Kimura: Titanium · Zirconium 23 (1975) 67­74.24) E. Kimura, A. Fuwa and S. Fukushima: Nippon Kogyo Kaishi 95

(1979) 821­827.25) A. Fuwa, E. Kimura and S. Fukushima: Metall. Mater. Trans. B 9

(1978) 643­652.26) K. I. Rhee and H. Y. Sohn: Metall. Mater. Trans. B 21 (1990) 331­340.27) K. I. Rhee and H. Y. Sohn: Metall. Mater. Trans. B 21 (1990) 321­330.28) L. K. Doraiswamy, H. C. Bijawat and M. V. Kunte: Chem. Eng. Prog.

55 (1959) 80­88.29) H. Zheng and T. H. Okabe: Proc. 16th Iketani Conf., Masuko

Symposium, ed. by S. Yamaguchi, (The 16th Iketani ConferenceOrganizing Committee, 2006, Japan) pp. 1005­1010.

30) R. Matsuoka and T. H. Okabe: Proc. Symp. on MetallurgicalTechnology for Waste Minimization, (134th TMS Annual Meeting,2005, San Francisco, United States) http://www.okabe.iis.u-tokyo.ac.jp/japanese/for_students/parts/pdf/050218_TMS_proceedings_matsuoka.pdf.

31) J. Kang and T. H. Okabe: Proc. 4th Asian Conf. on Molten SaltChemistry and Technology, and 44th Symposium on Molten SaltChemistry, (Molten Salt Committee, the Electrochemical Society ofJapan, Japan, 2012) pp. 176­182.

32) J. Kang and T. H. Okabe: Metall. Mater. Trans. B 44 (2013) 516­527.33) T. H. Okabe and J. Kang: Molten Salts 56 (2013) 15­26.34) I. Barin: Thermochemical Data of Pure Substances, 3rd ed., (VCH

Verlagsgesellschaft mbH, Weinheim, Germany, 1995).

10 20 30 40 50 60 70 80 90

MgTiO3 : PDF #01-079-0831

TiO2 (rutile)

FeTiO3 : PDF #01-071-1140

: PDF #03-065-0190

MgO : PDF #00-045-0946

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

Residue in the Mo-lined crucible(Exp. No. : 121020, Australia)

Residue in the Mo-lined crucible(Exp. No. : 121029, China)

(2)

(1)

(b)

Residue in the quartz crucible(Exp. No. : 121029, China)

Residue in the quartz crucible(Exp. No. : 121020, Australia)

(1)

(2)

Inte

nsity

, I (

a.u.

)

Angle, 2θ (deg.)

TiO2 (rutile)

MgTiO3 : PDF #01-079-0831

FeTiO3 : PDF #01-075-0519

Fe3O4 : PDF #01-089-0951

SiO2 : PDF #01-085-0865

TiO2 (anatase)

10 20 30 40 50 60 70 80 90

: PDF #01-072-1148

: PDF #01-073-1764 (a)

Fig. 14 (a) XRD patterns of the residues obtained in the quartz cruciblewhen various types of titanium ore were used as feedstock: (1) Australianilmenite and (2) Chinese ilmenite. (b) XRD patterns of the residuesobtained in the molybdenum-lined quartz crucible when various typesof titanium ore were used as feedstock: (1) Australian ilmenite and(2) Chinese ilmenite.

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride 1453