Ma e ials Sciences and Applica ions, 2014, 5, 441-458
Published Online May 2014 in SciRes. h p://www.sci p.o g/jou nal/msa
h p://dx.doi.o g/10.4236/msa.2014.57048
How o ci e his pape : Gázquez, M.J., Bolí a , J.P., Ga cia-Teno io, R. and Vaca, F. (2014) A Re iew o he P oduc ion Cycle
o Ti anium Dioxide Pigmen . Ma e ials Sciences and Applica ions, 5, 441-458. h p://dx.doi.o g/10.4236/msa.2014.57048
A Re iew o he P oduc ion Cycle o
Ti anium Dioxide Pigmen
Manuel Jesús Gázquez1,2*, Juan Ped o Bolí a 1, Ra ael Ga cia-Teno io3, Fede ico Vaca1
1Depa amen o de Física Aplicada, Uni e sidad de Huel a, Huel a, España
2Depa amen o de Química, P oyec o P ome eo, Uni e sidad Técnicas Pa icula de Loja (UTPL), Loja, Ecuado
3Depa amen o de Física Aplicada II, Uni e sidad de Se illa, Se illa, España
Email: *manuel.gazque[email p o ec ed], *mjgazquez@u pl.edu.ec
Recei ed 19 Ma ch 2014; e ised 23 Ap il 2014; accep ed 2 May 2014
Copy igh © 2014 by au ho s and Scien i ic Resea ch Publishing Inc.
This wo k is licensed unde he C ea i e Commons A ibu ion In e na ional License (CC BY).
h p://c ea i ecommons.o g/licenses/by/4.0/
Abs ac
Ti anium is a e y impo an elemen o se e al indus ial applica ions, being one o he nin h
mos abundan elemen s in he Ea h’s c us (0.63% w ). In his wo k i will discuss he di e en
mining and indus ial ac i i ies in ol ed in he p oduc ion o i anium dioxide. The i s s ep ana-
lyzed will ea abou he bene icia ion mining p ocess o i anium mine al, and secondly, i will
discuss he wo main p ocesses o he TiO2 manu ac u ing (sulpha e and chlo ide ou es). In addi-
ion, we will show di e en uses o he i anium dioxide pigmen as ille in pape , plas ics and
ubbe indus ies and as lux in glass manu ac u e, e c. Finally, we will show ha he old was es
a e cu en ly called co-p oduc s since hey we e alo ized, being comme cialized by he Spanish
indus y o TiO2 p oduc ion in di e en ields such as ag icul u e, ci il enginee ing, o cemen
manu ac u ing.
Keywo ds
Ti anium Mine als, Ti anium Dioxide Pigmen , P ope ies and Uses o Tio2, Valo iza ion o
Co-P oduc s
1. Ti anium Mine als: O igin, Deposi s and Resou ces
Ti anium was disco e ed in 1791 by he B i ish cle gyman and mine alogis William G ego while analyzing
black magne ic sands om Menachan in Co nwall (England). He p oduced a whi e me allic oxide om he min-
e al menachani e, a a ie y o ilmeni e, and named he new elemen menachi e. A ew yea s a e G ego ’s dis-
co e y, M.H. Klap o h, a Ge man chemis , sepa a ed TiO2 om he mine al u ile. Klap o h named he new
*Co esponding au ho .
M. J. Gázquez e al.
442
elemen i anium a e he gian s o G eek my hology. In 1825, J.J. Be zelius, a Swedish chemis , pe o med a
c ude sepa a ion o i anium me al. Howe e , i was no un il 1910 ha M.A. Hun e , an Ame ican chemis ,
p oduced pu e i anium. Ilmeni e, he p incipal i anium o e mine al, was named a e he Ilmen Moun ains in
he sou h U als.
Ti anium, wi h a omic numbe 22 and symbol Ti, is one o he ansi ion elemen s in G oup IVB o he pe i-
odic able. I s chemis y shows many simila i ies o hose o silicon and zi conium, al hough i s aqueous solu ion
chemis y shows some esemblances o hose o anadium and ch omium. Ti anium is a sil e -whi e me allic
elemen wi h a low densi y, good s eng h, excellen co osion esis ance, e y low elec ical and he mal con-
duc i i y, and is pa amagne ic. Ti anium is as s ong as s eel bu 45% ligh e . I is 60% hea ie han aluminum,
bu wice as s ong. Ti anium has a lowe coe icien o expansion and lowe he mal conduc i i y han ei he
s eel o aluminum alloys. Pu e i anium is malleable and duc ile bu i becomes b i le when con amina ed wi h
o he elemen s such as ca bon and ni ogen. I can be polished o a high lus e . The na u al i anium consis s o
i e s able iso opes, 46Ti (8%), 47Ti (7.3%), 48Ti (73.8%), 49Ti (5.5%) and 50Ti (5.4%), bu se e al uns able iso-
opes ( adioac i e) a e also known, being 51Ti, he adioac i e iso ope wi h highes hal -li e (5.76 min).
Ti anium is no ound as a pu e me al in na u e due o i s s ong a ini y o oxygen, ca bon and ni ogen, ma-
king i di icul o ob ain in he pu e s a e, bu i su e s he phenomenon o “passi a ion”, which is he p ocess
o making a ma e ial “passi e”, usually by he deposi ion o a laye o oxide ha adhe es o he me al su ace [1].
In he con ex o co osion, passi a ion is he spon aneous o ma ion o a ha d non- eac i e su ace ilm ha in-
hibi s u he co osion. This oxide o ni ide ilm usually has a hickness o ew nanome e s.
1.1. Ti anium Resou ces
Ti anium is he nin h mos abundan elemen in he ea h’s c us ep esen ing app oxima ely 0.6 pe cen and he
se en h me al mos abundan in he whole Ea h [2] [3] which is ound in p ac ically all ocks and sedimen s,
and is p esen in plan s, animals and na u al wa e s. I s elemen al abundance is abou i e imes smalle han i on
and 100 imes g ea e han coppe . Ti me al use is abou 200 imes less han coppe and 2000 imes less han
i on. The comme cial p oduc ion o i anium dioxide s a ed on he 1920 decade, and he Ti me al s a ed on he
1950 decade due o he inc ease o demand gene a ed by he ai c a indus y, eaching i s me al p oduc ion
166,000 me ic ons in 2008 [4]. Ti anium o es a e basically ound in na u e as mainly ilmeni e ( he mos im-
po an economic mine al), see Figu e 1, nominally FeTiO3 bu o en al e ed, ei he as a ock o as sand, u ile
(Figu e 2(a)), ana ase (Figu e 2(b)) and b ooki e, (Figu e 2(c)), which al hough hey all ha e he same o mula,
di e in hei c ys alline s uc u e and also as leucoxene (Fe2O3∙nTiO2) [5], an oxida ion p oduc o ilmeni e
which i is composed o inely c ys alline u ile.
The mine alogical p ope ies o he main i anium mine als a e summa ized in Table 1.
In addi ion, i anium is common in magne i e, wi h Ti- ich (2% - 20%) a ie ies e med i ani e ous magne i e
o i anomagne i e. O he less common i anium oxide-bea ing mine als a e pseudob ooki e (Fe2TiO5), pe o s-
ki e (CaTiO3), geikieli e ((Mg, Fe)TiO3), and py ophani e (MnTiO3) [6]. The only silica e mine al wi h i anium
as a majo componen is i ani e, o me ly called sphene.
Figu e 1. Ilmeni e o e. Pic u e ob ained om i ual
museum o he Uni e si y o Huel a.
M. J. Gázquez e al.
443
(a)
(b) (c)
Figu e 2. a) Ru ile o m; b) Ana ase o m; c) B ooki e o m. Pic u es ob ained om i ual mu-
seum o he Uni e si y o Huel a.
Table 1. P ope ies o some mine als o i anium [7].
Name, (Fo mula) %TiO2 Colou Ha dness Densi y C ys al Fo m T anspa ency
Ilmeni e
(FeTiO3) 52.6 black 5 - 6 4.5 - 5.0 hexagonal opaque
Pe o ski e
(CaTiO3) 58
Black, B own,
eddish-b own o yellow 5.5 4.48 - 4.26
Monoclinic
(pseudocubic)
Ru ile, ana ase,
b ooki e
(TiO2)
95 eddish-b own, ed,
yellowish o black
6.0 - 6.5 ( u ile)
5.5 - 6.0
(ana ase and
b ooki e)
4.23 - 5.5 ( u ile)
3.82 - 3.97
(ana ase) and
4.08 - 4.18
(b ooki e)
Te agonal ( u ile,
ana ase)
O ho hombic
(b ooki e)
opaque o
sub anspa en
Ti ani e (sphene)
(CaTiSiO5) 35 - 40 B own, g een, g ey,
yellow o black 5.0 - 5.5 monoclinic anspa en o
opaque
One o he mos impo an sou ces o i anium is he black mine al sands deposi s, which con ain mainly
hea y mine als wi h a speci ic g a i y g ea e han 2.85, and hey gene ally consis o wo o e p oduc s eams;
i s ly, i anium dioxide in he u ile o m, ilmeni e and leucoxene and, secondly, zi con. Ilmeni e is used in i s
na u al o m and also o manu ac u e i anium slag and syn he ic u ile p oduc s as we will see la e , Sec ion 2.2.
1.2. Main Deposi s
The geology o i anium mine al deposi s was e iewed by Fo ce [8], and hei wo ld p oduc ion and ese es
has been summa ized by Gambogui in di e en yea s (2009, 2010, and 2011) [4] [9] [10]. Mo e han hal o he
wo ld’s i anium p oduc ion is om ilmeni e and u ile in sho eline place deposi s in Aus alia, Sou h A ica,
USA, India and S i Lanka. Mos o he emainde is supplied by magma ic ilmeni e deposi s in Canada, No way,
M. J. Gázquez e al.
444
Finland and USA. The magma ic deposi s yield ilmeni e wi h a TiO2 con en o 35% - 40%, whe eas he sho e-
line place deposi s p o ide ilmeni e o highe TiO2 con en , including al e ed ilmeni e (60% - 75% TiO2), leu-
coxene (76% - 90% TiO2) and u ile (95% TiO2) [11].
In his sense, he mos signi ican class o magma ic ilmeni e deposi s is associa ed wi h ano hosi e o ano -
hosi e-gabb o complexes1, mos ly o P ecamb ian age. These o es ypically occu in ilmeni e- ich lenses, dikes
and sills cu ing he ano hosi es, and o lesse impo ance, dissemina ed in he ano hosi es. The ilmeni e p oba-
bly c ys allized om an immiscible i on- i anium- ich hea y liquid phase o a e odio i e magma [8], which
o med syngene ic laye s and seg ega ions, as well as au o-in usions in o pa ly o wholly solidi ied ano ho-
si e-gabb o. Mine als include ilmeni e, i ani e ous magne i e (wi h exsol ed i anhema i e and ul ospinel), pla-
gioclase, py oxene, oli ine, ga ne , bio i e, apa i e, u ile and py ho i e. In a second class o magma ic deposi s,
pe o ski e, u ile, b ooki e and/o ilmeni e occu in alkalic ing complexes p edominan ly composed o nephe-
line syeni es, bu a e pa icula ly associa ed wi h py oxeni e phases.
The i anium mine als mos ly occu in magne i e-pe o ski e dikes in uding py oxeni e (Py oxeni e is a plu-
onic ock ha consis s o da k mine als in he py oxene g oup plus a li le oli ine o amphibole mine als). The
p esence o Nb, REE and Th in he oxide mine als o his class o deposi makes e ining di icul and he e is
cu en ly no comme cially ope a ing p ocess o eco e y o TiO2 om pe o ski e. On he o he hand, some al-
kalic ano hosi ic complexes ha e con ac me asoma ic deposi s o u ile on hei ma gins. Signi ican onnages
o u ile o e may be de eloped whe e swa ms o ano hosi e dikes and sills pe mea e coun y ocks, as in he
Roseland Dis ic , Vi ginia [8].
Mo eo e , we ha e o ake in o accoun he impo ance o he allu ial place deposi s. Ru ile has been mined
om Qua e na y allu ial deposi s in he Gbangbama dis ic o Sie a Leone, whe e he deposi s a e mos ly
abou 10 m and up o 20 m hick, and lie di ec ly on bed ock.
In addi ion, u ile along wi h zi con and ilmeni e is mined om se e al Qua e na y beach and dune hea y-
mine al sand deposi s along he eas coas o Aus alia, om Tomago nea Newcas le in he sou h, o No h S a-
db oke Island, nea B isbane [12]. F om he no h o S adb oke Island o Glads one, he p opo ion o ilmeni e
inc eases a he expense o u ile and zi con. On he wes coas o Aus alia, ilmeni e, leucoxene, u ile, zi con
and monazi e a e eco e ed om Pliocene and Qua e na y sho eline deposi s, mainly nea Bunbu y in he sou h
and a Eneabba 225 km no h o Pe h [13].
In Sou h A ica, hea y-mine al deposi s occu in Holocene high dunes a Richa ds Bay, abou 160 km no h
o Du ban. In he USA, Pleis ocene beach deposi s in Jackson ille Dis ic , Flo ida (T ail Ridge and G een Co e
Sp ings), p oduce ilmeni e, a leucoxene- u ile mix u e, and u ile, wi h zi con, s au oli e and monazi e as co-
p oduc s. Nea by mode n beach deposi s we e mined in he pas . Unde eloped esou ces a e known in Geo gia,
Tennessee and he Ca olinas. India p oduces ilmeni e and u ile om beach deposi s nea Quilon and Mana-
alaku ichi on he sou h-wes e n coas . La ge deposi s ha e also been epo ed in he Cha apu a ea. Malaysia
and Thailand p oduce small quan i ies o i anium mine als as by-p oduc s om sho eline place in mining.
Sand ilmeni e place deposi s ha e been o med in mode n beach en i onmen s o a e olde aised beach de-
posi s o med du ing he Pleis ocene. Economic beach place s a e ypically 10 m hick, 1 km wide and o e 5
km long. A signi ican pa o he i on in sand ilmeni e is oxidized o he i alen s a e in a na u al p ocess a -
o ding wha is known as wea he ed ilmeni e. Ilmeni e sand wi h a 50% - 60% TiO2, 15% - 25% FeO and 15% -
25% Fe2O3 is a ypical eeds ock o he TiO2 indus ies using he sulpha e p ocess, bu he exhaus ion o some
la ge deposi s exploi ed du ing decades ha e led o some new deposi s being explo ed o i s po en ial wo king,
some o hem in a eas o Asia.
2. Ti anium O es P oduc ion, Rese es and Pu i ica ion
The e m “ i anium o e” co e s a wide a ie y o na u al o indus ial i anium esou ces ha can be used as eed
ma e ial by TiO2 pigmen and i anium me al p oduce . As we can see in Table 1, he mo e impo an comme -
cials i anium o es a e basically ound in na u e as mainly ilmeni e (nominally FeO∙TiO2 o TiFeO3) con aining
40% - 65% TiO2, wi h he es being mainly e ous and e ic i on oxides wi h some amoun s o o he oxide
impu i ies o ch omium, manganese, anadium, magnesium, aluminum, calcium, silicon and o he s, depending
on i s geological his o y, ei he as a ock o as sand [14]. The i anium and e ous and e ic i on con en in he
1Ano hosi e and ano hosi ic gabb o a e ock ypes consis ing o 90% - 100% and 75% - 90% plagioclase eldspa c ys als, espec i ely.
M. J. Gázquez e al.
445
ilmeni e may a y signi ican ly as i can be p esen in i s p ima y s oichiome ic o m (FeTiO3) o as wea he ed
ilmeni es and mix u es o bo h ypes. The wea he ed ilmeni e is he esul om he oxida ion and pa ial dissolu-
ion by g ound wa e o he i on, which g adually ans o ms p ima y ilmeni es o o he phases such as pseudo-
u ile (Fe2Ti3O9). The TiO2 con en can e en exceed he 60% when he o e is al e ed o leucoxene, which is a
mix u e o u ile o ana ase amo phous TiO2 and i on oxides.
Ti anium can also be ound in na u e as u ile, which is a iche o m o TiO2 (93% - 96% TiO2) which occu s
na u ally bu is no so o en ound in deposi s alid o comme cial use, and is o en used o eed he TiO2 and
inally can be ound as leucoxene (Fe2O3∙nTiO2), a na u al al e a ion p oduc o ilmeni e, ypically con aining
mo e han 65% TiO2 [6] [14].
2.1. Ti anium Wo ld Mine P oduc ion and Rese es
As we can see in Table 2, in 2009 he majo p oducing egions o ilmeni e we e Sou h A ica (1.05 M ), Aus-
alia (1.02 M ), Canada (0.65 M ), China (0.5 M ) India (0.42 M ), Vie nam (0.412 M ), No way (0.30 M ), and
Uk anie (0.30 M ), while he o al p oduc ion was 5.3 M . On he o he hand, he majo u ile p oduce s we e
Aus alia (0.266 M ), Sou h A ica (0.127 M ) and Sie a Leona (0.06 M ), wi h a o al wo ld p oduc ion o 0.55
M [10].
Nowadays he ese es o ilmeni e and u ile a e es ima ed o be abou 650 and 42 million me ic ons, espec-
i ely. Fo ha eason, he e is no doub ha ilmeni e is he mos impo an i anium esou ce, and i is su e ha
his o e will be he main sou ce o i anium in nea u u e. Ilmeni e supplies abou 91% o he wo ld’s demand
o i anium mine als, being i s wo ld p oduc ion o abou 5.3 million me ic ons in 2009, see Table 2.
In he nex decade, global demand o TiO2 is expec ed o con inue inc easing a an a e age a e o abou 3%
annually [4] [9]. G ow h highe han he a e age is expec ed o occu in he Asia egion. China in pa icula is
expec ed o lead wo ld g ow h in p oduc ion and consump ion. Howe e , he p oli e a ion o small TiO2 pig-
men plan s using he sulpha e- ou e in China has gi en a e y high TiO2 p oduc ion capaci y in China, eaching
1 M /y by he end o he decade [15]. G ow h in ae ospace, de ense, and indus ial uses will s ongly in luence
he demand o i anium me al o he o eseeable u u e. Based on he announced capaci y expansion plans, by
2015, wo ld-wide capaci ies would be expec ed o each 350,000 /y [15].
Table 2. Mine p oduc ion and es ima ed i anium o e p oduc ion in housands o ons [10].
Ilmeni e
Ru ile
Mine p oduc ion Rese es Mine p oduc ion Rese es
2009 2010 (**) 2009 2010(**)
Uni ed S a es 200 200 2000 (*) (*)
Aus alia 1020 1070 100,000 266 280 18,000
B azil 43 43 43,000 3 3 1200
Canada 650 700 31,000 - -
China 500 600 200,000 - -
India 420 420 85,000 20 20 7400
Madagasca 47 150 40,000 2 6 NA
Mozambique 283 350 16,000 2 2 480
No way 302 320 37,000 - -
Sou h A ica 1050 1120 63,000 127 130 8300
S i Lanka 30 40 - 11 12 NA
Uk anie 300 300 5900 57 57 2500
Vie nam 412 410 1600 - -
Sie a Leona - - 61 67 3800
O he coun ies 34 35 26,000 - - 400
Wo ld o al 5300 5800 650,000 550 580 42,000
(*) Uni ed S a e u ile p oduc ion and ese es da a a e included wi h ilmeni e. (**) es ima ed. (-) Ze o. NA No A ailable.

M. J. Gázquez e al.
446
2.2. Ti anium O e Pu i ica ion
Al e na i e i anium eeds ock comme cially a ailable a e ob ained om ilmeni e by i s pu i ica ion, as i is de-
sc ibed below, o ob ain “ i ania slag” and “syn he ic u ile”, p oduced a indus ial scale. The limi ed a ailabil-
i y o high quali y i anium o es, wi h high TiO2 and limi ed i on and hea y me als con en (ch omium, ana-
dium, e c.) is h ea ening he TiO2 business in e ms o gua an eed and quali y supply and p ices, pa icula ly
since 2010.
2.2.1. Upg ade o Ilmeni e o Slag and UGS
To p oduce he wo main i anium p oduc s, i anium dioxide (by sulpha e and chlo ide p ocess) [16] and me al-
lic i anium (K oll p ocess) [17], and aking in o accoun he exhaus ion o some deposi s, ilmeni e o es a e o en
upg aded o comme cial pu poses in o i ania “slag” con aining ypically 70 w % - 90 w % TiO2 by elec o-
smel ing p ocesses conduc ed a e y high empe a u es (mol en s a e) in elec ic a c u naces, whe e o he
“main” p oduc is he high pu i y pig i on (HPPI) o impo an and speci ic indus ial applica ions [18]. This
p ocess is applied o he ock ilmeni e om Eas e n Canada and No way, which is upg aded by a smel ing
p ocess by impo an mine al companies, wi h o wi hou a p elimina y p e- educ ion s age. The slag ob ained
om ock ilmeni e is comme cially supplied o TiO2 manu ac u e s as a eeds ock o he sulpha e p ocess, bu
canno be used o he chlo ide TiO2 manu ac u e due o i s ela i ely high calcium and magnesium con en [19].
A u he pu i ica ion o pa o he slag p oduced om ock ilmeni e is ca ied ou by he mal ea men [20]
[21] and p essu e leaching in HCl a o ding he “upg aded slag” (UGS), wi h 95% o TiO2 and a lowe calcium
and magnesium con en . UGS is a sui able eeds ock o he TiO2 chlo ide p ocess and i anium me al p oduc-
ion.
Al hough he sand ilmeni e is o en sold o he TiO2 indus y as a eeds ock o he sulpha e p ocess ( a ely
used o he chlo ide p ocess which equi es a highe TiO2 eeds ock such as slag o na u al o syn he ic u ile) i
is also smel ed o p oduce slag by using classical elec ic u naces, o a mode n DC plasma a c u nace echnol-
ogy. This is he case o he sand ilmeni e ex ac ed om se e al deposi s in Sou h A ica and p ocessed o a o d
a slag wi h 85% - 87% TiO2 which is sui able and sold o use in he TiO2 chlo ide p ocess, called o ha ea-
son as “chlo ide slag”, [22].
2.2.2. Bene icia ion o Ilmeni e o Syn he ic Ru ile
In he same way, ilmeni e o es a e also upg aded in o “syn he ic u ile” p oduc s con aining 90 w % - 96 w %
TiO2 by p ocesses consis ing in educing he i on oxide and he “leaching” wi h mine al acids. Al hough he e
a e a numbe o comme cialized o p oposed p ocesses o p oduce “syn he ic u ile”, he bes known a e he
Beche and he Benili e p ocess [22].
The Beche p ocess s a s wi h he educ ion o he i on in ilmeni e almos comple ely o i s me allic o m in a
o a y kiln wi h coal a ca. 1200˚C. The educed ilmeni e is p ocessed h ough a sc een and magne ic sepa a ion,
o emo e he cha , which is ecycled o he kiln. I is hen subjec ed o leaching in a NH4Cl solu ion unde ae a-
ion o oxidize and p ecipi a e he i on as oxide/hyd oxide in ine pa icles ha a e sepa a ed om he coa se
syn he ic u ile wi h hyd ociclones o a o d he TiO2 bene icia e.
In he Benili e p ocess, he i on con en o ilmeni e is educed o he e ous s a e wi h hea y oil in a o a y
kiln a 850˚C - 1100˚C. The educed o e is leached in diges e s wi h 18% - 20% HCl a 145˚C. The leached ma-
e ial is hen washed and calcined, a o ding he bene icia e. The leaching acid is egene a ed and he i on oxide
sepa a ed as a by-p oduc .
O he p ocesses ha e ei he been used o a e unde de elopmen , such as he Rupaque p ocess un a Japan
du ing a numbe o yea s, he Aus pac p ocess by oas ing and leaching wi h HCl, and he Al ai p ocess based
on leaching wi h concen a ed chlo ide solu ions. All hose p ocess ha e some simila i ies wi h he p e iously
desc ibed ones.
3. Manu ac u e o Ti anium Dioxide Pigmen s
In opposi ion o he popula belie , he mos widely used i anium p oduc is no he i anium me al and alloys,
bu a he is he i anium dioxide (TiO2) pigmen ha p o ide whi eness and opaci y o a as ange o e e yday
p oduc s om coa ings and plas ics, o inks and e en as lux in glass manu ac u e, ille in pape , ubbe indus-
ies [15], cosme ics and ood. Annually mo e han 4.5 million o TiO2 a e p oduced wo ldwide [23] and only
abou 4% - 5% is used o p oduce me allic i anium [24].
M. J. Gázquez e al.
447
Ti anium dioxide was i s disco e ed in he ea ly 1900s and he manu ac u e o i anium whi e o use as a
pigmen (ana ase o m) was i s epo ed in 1923 in F ance, whe e soon eplaced he li hopone2 and oxic
lead-based pigmen s in he ea ly 1930s.
Ti anium dioxide pigmen s a e p oduced om a a ie y o o es by wo di e en p ocesses: he sul a e p ocess
(abou 40% o o al TiO2 p oduc ion) using concen a e sulphu ic acid and he chlo ide p ocess (abou 60%) us-
ing chlo ine gas. Bo h p ocesses di e in hei chemis y and aw ma e ial equi emen s. Because he chlo ide
p ocess has some ad an ages o e he adi ional sul a e p ocess in cos and was e managemen , i has domina -
ed he pigmen indus y in ecen imes.
3.1. The Chlo ide P ocess
The chlo ide p ocess, comme cialized by Du Pon in he ea ly 1950s, o e s was e disposal, ene gy and quali y
ad an ages o e he sul a e p ocess [25]. This p ocess can use a wide ange o eeds ock, i.e. u ile, syn he ic u-
ile, high-g ade ilmeni e o slag, depending o he indus y bu mainly u ile and syn he ic u ile (90% - 95%
TiO2) a e used, a oiding he i on sul a e was e p oblem.
The chlo ide p ocess begins wi h he mixing o aw ma e ials wi h gaseous chlo ine a a empe a u e o
a ound 900˚C - 1000˚C in a luidized bed eac o in he p esence o coke as a educing agen (1) [23]. The e-
sul ing gas s eam con ains i anium e achlo ide (TiCl4), oxides o ca bon and all he impu i y me als om he
eeds ock in he o m o me al chlo ides, bu impu i ies such as silica and zi conium may no chlo ina ed and
emain accumula ed in he eac o [23] [25]. Signi ican quan i ies o gas chlo ine a e equi ed o low TiO2 con-
en eeds ock.
The main chemical eac ions o his p ocess a e he ollowings:
2TiO2 + 3C + 4Cl2 → 2TiCl4 + 2CO + CO2 (1)
TiCl4 (impu e gas) → TiCl4 (pu e liqui ) (2)
TiCl4 + O2 → TiO2 + 2Cl2 (3)
The gas s eam is con ac ed wi h ecycled liquid TiCl4 which cools i o a le el in a which he o he me al
chlo ides sepa a e ou as solids by condensa ion and chemical ea men . The impu i ies can be educed o ypi-
cally abou 10 - 20 mg∙kg−1. The pu i ied TiCl4 goes o wa d wi h u he cooling o be condensed as a liquid (2)
and hen ed o a high empe a u e oxida ion eac o whe e i is eac ed wi h oxygen, abo e 1500˚C, ei he in a
plasma a c u nace o in a oluene- i ed u nace o o m i anium dioxide and elease he chlo ine which is e-
cycled back o he beginning o he eac ion (3). Residual chlo ine associa ed wi h he solid TiO2 is emo ed by
aqueous hyd olysis. Finally he pu e i anium dioxide is subjec ed o a ange o chemical su ace ea men s,
milling and d ying.
The was es gene a ed by he chlo ide p ocess a e mainly coke and o e solids ha emain un- eac ed du ing he
chlo ina ion p ocess. In addi ion a was e acid solu ion, usually called i on chlo ide was e acid, is also gene a ed
when he combined s eam o un- eac ed coke and o e solids, me al chlo ide solids, is acidi ied using wa e o
was e hyd ochlo ic acid (HCl) om he eac ion sc ubbe . The me al chlo ide impu i ies a e gene ally en i on-
men ally ha m ul, especially he i on chlo ide, which a e emo ed and neu alized wi h lime o limes one, and
inally sen o disposal ia land ill. Cu iously, in one chlo ine plan in he Uni ed S a es, he chlo ine sal s a e
no neu alized, bu hey a e injec ed in o deep exhaus ed oils well [22].
In he desc ibed p ocess he consump ion o chlo ine is he e o e ela ed o he amoun o i on oxide p esen s
in he aw ma e ial. Abou one on o chlo ine is equi ed o p oduce 5 o 6 ons o i anium dioxide pigmen
(depending on he i on con en in he eeds ock used consuming he chlo ine as e ic chlo ide and wi h abou
one- hi d o chlo ine ending up as hyd ogen chlo ide).
Cu en ly, he chlo ide p ocess o e s igh e p oduc con ol, is less labo in ensi e, and is en i onmen ally
sa e . Cu en ly abou 60 pe cen o he 4.5 million ons o pigmen p oduc ion wo ld-wide is gene a ed by he
chlo ine p ocess. Al hough declining in esponse o conce ns abou en i onmen ally unaccep able was e, many
sul a e plan s ha e in oduced inno a i e echniques de e ing hei closu e.
3.2. Sulpha e P ocess
The sulpha e p ocess was he i s comme cialized echnology o ob ain he i anium dioxide pigmen . In his
2Li hopone is a whi e pigmen composed o a mix u e o ba ium sul a e (28% - 30%) and zinc sul ide (68% -
70%) wi h ace amoun s o
zinc oxide.
M. J. Gázquez e al.
448
p ocess, ilmeni e (40% - 60% TiO2) o i anium slag (72% - 85% TiO2) o e en a ca e ully con olled blend, is
diges ed wi h concen a ed sulphu ic acid (98%). A highly-exo he mic eac ion is ini ia ed by he addi ion o
measu ed quan i ies o s eam, wa e and dilu ed sulphu ic acid. The gene al equa ion o he diges ion eac ion
(dissolu ion o he aw ma e ial) is he ollowing:
FeTiO3 + 2H2SO4 → TiOSO4 + FeSO4 + H2O (Dissolu ion o he aw ma e ial) (4)
TiOSO4 + H2O → TiO2n.H2O + H2SO4 (TiO2 p ecipi a ion) (5)
TiO2n∙H2O → TiO
2+ nH2O (TiO2 calcina ion and condi ioning) (6)
The esul ing liquo con ains i anyl sulpha e (TiOSO4) and i on sulpha e (FeSO4) dissol ed in sulphu ic acid.
I he eeds ock used is ilmeni e based, a educ ion s ep is equi ed in which i on is added o con e any e ic
ions (Fe3+) o he e ous (Fe2+) o m o aid sepa a ion la e in he p ocess. The e o e o ensu e ha all he i on
is in dissolu ion, he liquo is passed h ough sc ap me al (i on educ ion s ep). Then, i passes o a cla i ica ion
ank whe e he undissol ed o e and solids a e allowed o se le. The i anium liquo is hen concen a ed and hy-
d olyzed o i anium dioxide hyd a ed (5).
The i anium dioxide hyd a ed p ecipi a es om he e ous sulpha e and sulphu ic acid is sepa a ed by il a-
ion. The i on sulpha e is sepa a ed om he i anium dioxide p oduc ion p ocess liquo s by concen a ion and
cooling, as we will see wi h mo e de ail in Sec ion 5.1. A e il a ion, he hyd a ed i anium dioxide slu y is
sen o a calcine , whe e he i anium dioxide c ys als g ow o hei inal c ys alline size and esidual wa e and
H2SO4 a e emo ed (6). The d ied i anium dioxide is sen o a inishing phase, which in ol es any equi ed mil-
ling and o chemical ea men , such as su ace coa ing wi h silica o alumina. Fu he p ocessing ( inishing), is
hen analogous o he chlo ide p ocess in ol ing chemical su ace ea men s (coa ing), milling and d ying ope -
a ions.
Abou one on o aw ma e ial (ilmeni e o ilmeni e + slag) is equi ed o p oduce 0.5 ons o i anium dioxide
pigmen .
Finally, we can say ha he sulpha e p ocess uses a simple echnology and lowe g ade and cheape aw ma-
e ials o p oduce a o m o pigmen called ana ase ( e agonal, nea oc ahed al), which is p e e ed o e he
pigmen om he chlo ide p ocess o use in pape s, ce amics and inks. Howe e , he adi ional sulpha e
p ocess p oduce lowe quali y p oduc s o mos applica ions and la ge quan i ies o was e i on sulpha e, due o
he high concen a ion o i on p esen s in he ilmeni e used. The exhaus ion o some la ge deposi s exploi ed
du ing decades ha e led o some new deposi s being explo ed o i s po en ial wo king bu he end is o eed
he TiO2 sulpha e si es con aining ilmeni e wi h lowe TiO2 han in he pas .
4. P ope ies and Uses o Ti anium Dioxide Pigmen s
As men ioned abo e, abou 95% o i anium o e is p ocessed in o i anium dioxide which is he mos widely
used i anium p oduc . TiO2 is a polymo phous and simple ino ganic compound, exis ing in h ee undamen al
c ys al o ms. All h ee o ms, ana ase, u ile and b ooki e, occu na u ally bu he la e is a e, and al hough i
has been p epa ed in he labo a o y i is o no comme cial in e es . The e o e, he main c ys al o ms commonly
a ailable a e wo, ana ase and u ile. Ru ile is he mos s able o m and is hus he mos abundan . I has a mo e
compac s uc u e han ana ase and his gi es ise o impo an di e ences in p ope ies be ween bo h modi ica-
ions. Ru ile TiO2 has a highe e ac i e index, highe speci ic g a i y and g ea e chemical s abili y han ana-
ase, smel ing a 1825˚C. Ana ase has no speci ic mel ing poin as i is i e e sibly ans o med o u ile be o e a
mel ing poin is eached.
4.1. P ope ies
TiO2 is a simple ino ganic compound p oduced as a pu e whi e powde (known as i anium whi e). This pigmen
can be used, in mos o i s applica ions, as a pigmen o sca e ligh , because abso bs almos no inciden ligh in
he isible egion o he spec um. This pigmen sca e s ligh by h ee mechanisms: e lec ion om he su ace
o a c ys al, e ac ion wi hin a c ys al, and di ac ion, whe eby ligh is ben as i passes nea a c ys al. Re lec-
ion and e ac ion a e maximized by inc easing he di e ence be ween he e ac i e index o he pigmen and
ha o he polyme ma ix o o he ma e ial in which i is dispe sed. In addi ion, TiO2 is a good pigmen because
i has a e y high e ac i e index o 2.70 in compa ison wi h alues o only 2.02 and 1.57 o zinc oxide and
china clay espec i ely, as we can see in Table 3. This means ha ela i ely low le els o he pigmen a e e-
M. J. Gázquez e al.
449
qui ed o achie e a whi e opaque coa ing.
This high e ac i e index gi es he po en ial o p oducing much g ea e opaci y o hiding powe , making
TiO2 a much be e pigmen han he o he chemicals men ioned. Ligh sca e ing by di ac ion is mos e ec i e
when he pigmen diame e is sligh ly less han hal he wa eleng h o he ligh o be sca e ed. Hence, he
whi eness o i anium dioxide pigmen s is a unc ion o pa icle size. Pigmen s con aining smalle -sized pa icles
lead o inished p oduc s (e.g., pain s, plas ics, e c.) ha end o ha e a bluish in ; pigmen s wi h la ge -sized
pa icles cause inished p oduc s o ha e a mo e yellowish in [26].
On he o he hand, we can see in Table 3 ha mos u ile pigmen s ha e a speci ic g a i y be ween 3.9 and
4.1, while ana ase g ades ha e 3.7 o 3.8. Zinc sulphide and Li hopone 30% ha e sligh ly highe alues o spe-
ci ic g a i y, bu o he whi e pigmen s a e much dense . An impo an measu e o a pigmen ’s po en ial hiding
powe can be de e mined by a simple es whe eby i is in ed wi h a s anda d black pigmen , and assessed using
an a bi a y scale. The in ing s eng h alues o u ile i anium pigmen s ange be ween 1550 and 1850 and o
ana ase be ween 1150 and 1350. The bes o he o he whi e pigmen s lis ed in Table 3, zinc sulphide, is only
hal as powe ul as u ile.
O he impo an ea u es o i anium dioxide pigmen s a e excellen esis ance o chemical a ack, good he -
mal s abili y and esis ance o ul a iole (UV) deg ada ion. Ru ile pigmen is mo e esis an o UV ligh han
ana ase, and is p e e ed o pain s, plas ics, especially hose exposed o ou doo condi ions, and inks. On he
o he hand, ana ase pigmen has a blue one han he u ile ype, is less ab asi e and is used mainly in indoo
pain s and in pape , ce amics, ubbe and ibe s manu ac u e. One possible explana ion o he high ab asion
p ope ies o u ile TiO2 pigmen s is he mul iple ace s o he pigmen pa icles [26]. Also, ana ase e lec s mo e
ul a iole ligh han u ile, making mo e ul a iole ligh a ailable o op ical b igh ene s. Bo h u ile and ana-
ase pigmen s can be made mo e esis an o pho odeg ada ion by coa ing he pigmen pa icles, which also im-
p o es hei dispe sibili y, dispe sion s abili y, opaci y and b igh ness. Ana ase is 10 imes mo e ac i e han u-
ile and esponds o sligh ly di e en wa eleng hs [27]. In pape , he ad an age o u ile o e ana ase is less de-
cisi e because he ligh -sca e ing ad an age is pa ially o -se by a densi y disad an age.
The e o e we can say ha i anium dioxide is he bes whi e pigmen a ailable, bu his does no jus es ic
i s use o any hing ha is whi e; he opaci y is also used in combina ion wi h colo ed pigmen s o gi e hem he
equi ed hiding powe hey need.
Taking in o accoun he p ope ies abo e men ioned, he majo consume indus ies o i anium dioxide pig-
men s a e ma u e sec o s in high- esou ce coun ies whe e hey a e used o su ace coa ings, pape and pape -
boa d and plas ics. In addi ion, consump ion o i anium dioxide ends o be pa allel o he gene al economic
ends. Wo ld consump ion o i anium dioxide by end-use in 2001 was: coa ings, 55%; plas ics and ubbe , 24%;
pape , 12%; p in ing inks, 3%; and o he , 6%; while in 2005 was: coa ings, 58%; plas ics and ubbe , 23%; pa-
pe , 11%; and o he , 8% [23] [28]. Some o he uses o i anium dioxide a e in ca alys s, ce amics, coa ed ab ics
and ex iles, loo co e ings and oo ing g anules [29].
Acco ding o he Ame ican Socie y o Tes ing and Ma e ials (ASTM, 1988 [30]) D476-84 s anda d, ou
ypes o i anium dioxide pigmen exis [31] [32].
Table 3. Re ac i e index, Re ac i e in ing s eng h and speci ic g a i y o some whi e pigmen s.
Pigmen s Re ac i e Index Tin ing S eng h Speci ic G a i y
Whi e lead 2.00 100 6.7
Zinc oxide 2.02 200 5.6
Zinc sul ide 2.37 900 4.0
Ana ase TiO2 2.55 1350 3.7 - 3.85
Ru ile TiO2 2.70 1850 3.7 - 4.2
China Clay 1.57 <100 2.6
Li hopone 30% 1.84 300 4.3
An imony Oxide 2.30 400 5.7
M. J. Gázquez e al.
456
public o Ecuado -(SENESCYT o i s ac onym in Spanish). The au ho s would like o acknowledge he inan-
cial suppo ecei ed om he company Tioxide-Huel a by he esea ch p ojec s “Valo iza ion o ed gypsum
om he indus ial p oduc ion o i anium dioxide” (PROFIT, CIT-310200-2007-47) and “Applica ions o ed
gypsum and Tioni e was e in comme cial applica ions”. The au ho s also hank o he echnical s a o he ad-
iso y p o ided in he explana ion o he esul s.
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