Treatment of raw materials containing titanium

Production of titanium dioxide which is characterized by recovery of reusable H.sub.2 SO.sub.4, highly pure Fe oxide and hydroxide and fractional recovery of Mn, V and Cr, etc., from FeSO.sub.4. nH.sub.2 O and waste acid of 20 - 40% H.sub.2 SO.sub.4 containing abundant heavy metallic ions, which are by-produced in the production of TiO.sub.2 by dissolution of Ti raw materials such as ilmenite, steel production slag, such as electric furnace slag, convertor slag with H.sub.2 SO.sub.4.

BACKGROUND OF THE INVENTION 
This invention is concerned with the production of titanium dioxide which 
is characterized by recovery of reusable H.sub.2 SO.sub.4, high pure Fe 
oxide and hydroxide and fractional recovery of Mn, V and Cr, etc., from 
FeSO.sub.4.nH.sub.2 O and waste acid of 20 - 40% H.sub.2 SO.sub.4 
containing abundant heavy metallic ions, which are by-products of the 
production of TiO.sub.2 by dissolution of Ti raw materials, such as, 
ilmenite, steel production slag, such as, electric furnace slag, convertor 
slag with H.sub.2 SO.sub.4. 
In the conventional production of TiO.sub.2 using H.sub.2 SO.sub.4, the 
required amount of 98% H.sub.2 SO.sub.4 per 1 ton of TiO.sub.2 product is 
3.5 to 4.2 tons. Nevertheless, an economical treatment of 
FeSO.sub.4.nH.sub.2 O and waste acids produced in abundance as by-products 
after the separation of Ti compounds by the hydrolysis process has not 
been found and the practice of retaining or discarding them in the 
untreated form has given rise to serious pollution problems. This 
invention has been developed to overcome the faults of the conventional 
production process described above. 
SUMMARY OF THE INVENTION 
The present invention relates to the production of titanium dioxide which 
is characterized by the recovery of reusable H.sub.2 SO.sub.4, high pure 
Fe oxide and hydroxide and fractional recovery of Mn, V and Cr, etc., from 
FeSO.sub.4.nH.sub.2 O and waste acid of 20 - 40% H.sub.2 SO.sub.4 
containing abundant heavy metallic ions, which are by-products in the 
production of TiO.sub.2 by dissolution of Ti raw materials, such as, 
ilmenite, steel production slag, such as electric furnace slag, convertor 
slag, with H.sub.2 SO.sub.4. 
The summary of this invention is as follows. The present invention is 
firstly characterized by the absence of the production of waste acids and 
FeSO.sub.4.nH.sub.2 O is as follows: The aqueous solution pretreated after 
dissolution of the Ti raw materials with H.sub.2 SO.sub.4 is brought into 
contact and mixed with an organic solvent (A) to extract metallic ions, 
such as, Cr.sup.3+ and Nb.sup.5+ ions in the first stage and the bulk of 
Ti ions in the resulting aqueous solution is separated by well-known 
hydrolysis process in the 2nd stage. The metallic ions, such as, Ti, Mn 
and V ions remaining in the resulting aqueous solution are extracted into 
an organic solvent (B) in the 3rd stage, an organic solvent (C) extracts 
Fe ions in the resulting aqueous solution after the oxidation of Fe.sup.2+ 
ions to Fe.sup.3+ ions in the 4th stage and V.sup.5+ ions in the resulting 
aqueous solution are extracted into an organic solvent (D) in the 5th 
stage. The resulting aqueous solution from the 5th stage is the reusable 
regenerated acid for use in dissolution of raw materials. 
The second characteristic of the present invention is concerned with the 
extraction of Fe ions from the aqueous solution using Cl.sub.2 gas for the 
oxidation as follows: After the conversion of Fe.sup.2+ ions in the 
aqueous solution from the 3rd stage as described hereinafter to Fe.sup.3+ 
ions using Cl.sub.2 gas, the amount of HCl required to extract Fe.sup.3+ 
ions in the aqueous solution as the Fe chloride complex is added to the 
resulting aqueous solution and is contacted with an organic solvent (E) to 
extract Fe-Cl ions into the organic phase. 
The third characteristic of this invention is concerned with the reduction 
of energy in the concentration process of the acid as follows. 
FeSO.sub.4.nH.sub.2 O which is a by-product in the pretreatment process is 
dissolved with water or acids from the fourth stage, the oxidation of 
Fe.sup.2+ ions in the resulting aqueous solution to Fe.sup.3+ ions is 
finished and then Fe.sup.3+ ions in the resulting aqueous solution are 
extracted into the organic phase by contact of the organic solvent (C). 
The resulting increase in the concentration of regenerated acid by several 
repetitions of the above operation as necessary produces reduction in the 
energy required in the following concentration processes of the acid. 
The fourth characteristic of the present invention is concerned with the 
treatment of FeSO.sub.4.nH.sub.2 O with the fractional extraction of Mn 
and Fe ions as follows. After dissolution of the FeSO.sub.4.nH.sub.2 O 
by-product with water, Mn.sup.2+ ions in the resulting aqueous solution 
are extracted with an organic solvent (F) into the organic phase to 
separate them from the Fe.sup.2+ ions in the resulting aqueous solution, 
the Fe.sup.2+ ions are oxidized to Fe.sup.3+ ions and then the Fe.sup.3+ 
ions are extracted into the organic phase by contacting them with the 
organic solvent (C). The concentration of the recovered acid is enhanced 
by several repetitions of the above operation as necessary and by 
recycling for dissolution of the raw materials by way of the concentration 
process. 
The fifth characteristic of this invention is concerned with the reduction 
of the recovery cost by increasing the Fe concentration in the aqueous 
solution which is introduced into the recovery process of HCl and Fe as 
follows. The Fe concentration of the aqueous solution introduced into the 
recovery process of HCl and Fe is increased by extracting Fe.sup.3+ ions 
in the back-extraction solution of the organic solvent (C) with contact of 
the organic solvent (E) and stripping with water. The increased Fe 
concentration produces the reduction of recovery cost. 
The 6th characteristic of this invention is concerned with the reasonable 
recovery of Fe compounds using both solvent extraction and 
diaphragm-electrolysis techniques as follows. The back-extraction solution 
of the organic solvent (C) or of the organic solvent (E) is introduced 
into the cathode compartment of the diaphragm-electrolysis, Fe.sup.3+ ions 
are reduced to Fe.sup.2+ ions there, free acid is transferred to the anode 
compartment and hydrated Fe oxide or hydroxide is recovered by the contact 
of air or oxygen with the aqueous solution in the cathode compartment 
containing a lesser amount of free recovered acid. 
The 7th characteristic of this invention is concerned with the fractional 
recovery of metallic ions coextracted into the organic solvent (B) as 
follows. Mn, V and Fe ions coextracted into the organic solvent (B) are 
scrubbed with HCl or H.sub.2 SO.sub.4, Ti ions in the organic solvent (B) 
is back-extracted into the aqueous solution with contact of 
(NH.sub.4).sub.2 CO.sub.3 + NH.sub.3 solution, and then the organic 
solvent converted from H type to NH.sub.3 type in the above operation is 
again converted to H type with contact of H.sub.2 SO.sub.4. When Cr.sup.3+ 
ions are coextracted, those in the organic phase can be recovered into the 
aqueous solution with contact of HCl + H.sub.2 O.sub.2 or HCl + NaCl 
solution. Thus, the individual metallic ion coextracted into the organic 
solvent (B) are fractionally recovered. When Al.sup.3+ and Mg.sup.2+ ions 
are accumulated in the recovered acid during recycle of the recovered 
acid, the enhancement of their ions concentration is depressed by taking 
one part of out the extraction system and the solution is taken out is 
recovered as (NH.sub.4).sub.2 SO.sub.4 by neutralizing with NH.sub.3. 
Since the desired purpose can be accomplished by installation of the 
process based on this invention along with the conventional production 
process of TiO.sub.2, the control of production line of TiO.sub.2 and its 
quality are unchangeable and consequently the practical application of 
this invention is very easy and the economical recovery of valuable metals 
which could not be economically recovered hitherto becomes possible. 
Therefore, the present invention has a great deal of industrial values for 
the connected industrial fields.

The following explanation is based on the experiments carried out by the 
inventors. The typical chemical analysis of ilmenite used commonly as a 
raw material of TiO.sub.2 is shown as follows. 
______________________________________ 
TiO.sub.2 
FeO Fe.sub.2 O.sub.3 
V.sub.2 O.sub.5 
MnO Cr.sub.2 O.sub.3 
MgO 
______________________________________ 
54.20 26.60 14.20 0.16 0.40 0.07 1.03 
53.13 19.11 22.95 0.19 0.94 0.03 0.92 
Values in wt.% 
______________________________________ 
2 to 2.5 tons of raw material described above per 1 ton of TiO.sub.2 
product is sulfatized with 3.5 to 4 tons of 98% H.sub.2 SO.sub.4. After 
heating to sulfatize, Fe.sup.3+ ions in the resulting aqueous solution is 
completely reduced with Fe scrap. The clarified solution is produced by 
removing undissolved residues. The chemical composition of the aqueous 
solution which is obtained after removing one part of Fe ions as 
FeSO.sub.4.nH.sub.2 O crystal is shown as follows 
______________________________________ 
TiO.sub.2 
Fe.sup.2+ 
T . H.sub.2 SO.sub.4 
Cr.sup.3+ 
Mn.sup.2+ 
V.sup.4+ 
Mg.sup.2+ 
______________________________________ 
200 32 300 0.1 1.8 0.3 1.6 
Values in g/l 
______________________________________ 
The synthesized solution having the above mentioned chemical composition 
and no Fe.sup.3+ ions was as a standard solution in the following 
experiment. 
(1) The First Stage 
The extraction of Cr.sup.3+ and Nb.sup.5+ ions with the organic solvent (A) 
is run before hydrolysis process owing to their superior extractability in 
lower concentrations of free acid and higher temperatures of the aqueous 
solution. Organic solvent (A) is made up of primary, amine secondary, 
tertiary or quaternary amines, for example, "Primene JMT" (tradename, 
primary amine produced by Rohm and Haas), "Amberlite LA-1" (tradename, 
secondary amine produced by Rohm and Haas), "Alamine 336" (tradename, 
tertiary amine produced by General Mills), and "Aliquat 336" (tradename, 
quaternary amine produced by General Mills), 2 - 5% higher alcohols such 
as, octanol, dodecanol or isodecanol as a modifier and aromatic aliphatic 
or paraffin hydrocarbon as a diluent. The organic solvents used in this 
experiment indicate only one example and of course similar organic 
solvents can be utilized. 
- Extraction - 
The extraction test is done with the increased concentration of Cr.sup.3+ 
and Nb.sup.5+ ions by adding and adjusting the Cr.sub.2 (SO.sub.4).sub.3 
and NbCl.sub.5 concentration in the aqueous solution described above. 
Cr.sup.3+ and Nb.sup.5+ ions are extracted according to the following 
formulas. 
__________________________________________________________________________ 
NbO(SO.sub.4).sub.2.sup.- 
+ H.sub.2 RN 
+ H.sup.+ 
.revreaction. 
(H.sub.2 RNH.sup.+) . NbO(SO.sub.4).sub.2.sup.- 
(see FIG. 3) 
(Aq) (Org) (Aq) (Org) 
CrSO.sub.4 
+ H.sub.2 RN 
+ H.sup.+ 
.revreaction. 
(H.sub.2 RNH.sup.+) . CrSO.sub.4.sup.- 
(see FIG. 4) 
(Aq) (Org) (Aq) (Org) 
__________________________________________________________________________ 
The extractability of Cr.sup.3+ ions by amines follows the order: primary 
amine &gt; secondary amine &gt; tertiary amine. However, there is little 
difference in the extractability of Nb.sup.5+ ions with various amines. 
The main factors of the Cr.sup.3+ ions extraction are temperature, contact 
time and concentration of free acid. The high extractability of Cr.sup.3+ 
ions is obtained the 50.degree. to 80.degree. C and the longer contact 
time the higher the concentration of free acid. 
- Stripping - 
Cr.sup.3+ ions extracted into the organic solvent (A) are stripped from the 
organic phase with by contact with HCl or H.sub.2 SO.sub.4 according to 
the under formula. 
__________________________________________________________________________ 
(H.sub.2 RNH.sup.+) . CrSO.sub.4.sup.- 
+ 1/2 H.sub.2 SO.sub.4 
.revreaction. 
H.sub.2 RN 
+ 1/2 Cr.sub.2 (SO.sub.4).sub.3 
+ 2 H.sup.+ 
(Org) (Aq) (Org) (Aq) (Aq) 
Back-extraction test (see FIG. 5) 
Temp. 
Back-extraction % 
Temp. 
Back-extraction % 
__________________________________________________________________________ 
15% HCl 
20.degree. C 
88.9% 20% H.sub.2 SO.sub.4 
20.degree. C 
81.4% 
20% HCL 
20.degree. C 
99.0% 30% H.sub.2 SO.sub.4 
60.degree. C 
98.0% 
__________________________________________________________________________ 
After removing Cr.sup.3+ ions from the organic solvent (A), Nb.sup.5+ ions 
is stripped from the organic phase with contact of NH.sub.4 F + NH.sub.3 
solution according to the following formula. 
__________________________________________________________________________ 
(H.sub.2 RNH.sup.+) 
. 
NbO(SO.sub.4).sub.2.sup.- 
+ NH.sub.4 F 
+ 4NH.sub.4 OH 
.revreaction. 
H.sub.2 RN 
+ Nb(OH).sub.5 
+ 2(NH.sub.4).sub.2 SO.sub.4 
+ NH.sub.4 F 
(Org) (Aq) (Aq) (Org) (ppt) (Aq) (Aq) 
__________________________________________________________________________ 
(2) The Second Stage 
A large amount of Ti ions is removed as Ti hydroxide by hydrolysis process 
of the resulting aqueous solution from which Cr.sup.3+ and Nb.sup.5+ ions 
have been extracted. The approximate chemical composition of the liquor 
after separation of titanium is shown as follows. 
______________________________________ 
TiO.sub.2 
Fe.sup.2+ 
T . H.sub.2 SO.sub.4 
Cr.sup.3+ 
V.sup.4+ 
Mn.sup.2+ 
Mg.sup.2+ 
______________________________________ 
7 32 300 Tr 0.3 2.8 1.6 
Values in g/l 
______________________________________ 
(3) The Third Stage 
Ti ions and one part of the V.sup.4+ ions in the resulting aqueous solution 
are extracted into the organic phase with the organic solvent (B). When 
there are Cr.sup.3+ ions from the omission of the first stage, Cr.sup.3+ 
ions are coextracted with Ti ions into the organic solvent (B) as shown in 
FIG. 6. The organic solvent (B) is composed of alkyl phosphoric acid, for 
example, D2EHPA(Di-2-ethyl hexyl phosphoric acid) and H.sub.2 DDP 
(Mono-dodecyl phosphoric acid), 2 - 5% higher alcohols, such as, octanol, 
decanol or isodecanol as a modifier and aromatic, aliphatic or paraffin 
hydrocarbons as a diluent. 
- Extraction - 
Ti.sup.4+ ions are extracted with the organic solvent (B) according to the 
under formula. 
__________________________________________________________________________ 
Ti.sup.4+ 
+ 4 [(RO).sub.2 POOH] 
.revreaction. 
Ti[(RO).sub.2 POO].sub.4 
+ 4 H.sup.+ 
(see FIG. 7) 
(Aq) (Org) (Org) (Aq) 
__________________________________________________________________________ 
The resulting solution includes a small amount of V.sup.5+ ions and they 
are slightly extracted. While, Fe.sup.3+ ions are not commonly contained 
in the resulting solution, but if Fe.sup.3+ ions exist in it, they are 
completely extracted like Ti.sup.4+ ions. Mn.sup.2+ ions are extracted as 
the concentration of free acid lowers. 
- Continuous extraction test - 
The liquor as shown in the following table was continuously treated with 
the organic solvent (B) at a flow rate of 0.15 l/min. using a 
mixer-settler (100 mm W .times. 500 mm L .times. 180 mm H). The mixer was 
of the pump-suction type and rotated at 120 - 310 r.p.m. depending on the 
interface level in the settler using a non-stepwise speed changer. The 
organic solvent used consists of 20% D2EHPA, 3% octanol and kerosene in 
balance. 
______________________________________ 
The third stage - Extraction 
Flow 
ratio Inlet(Aq) Outlet(Aq) 
Appa- O/A Ti V Fe H.sub.2 SO.sub.4 
Ti V Fe H.sub.2 SO.sub.4 
ratus 
5 Stage 
1.0/ 7.1 0.2 31.8 300 tr 0.18 31.8 300 
mixer- 
settler 
1.0 
______________________________________ 
Outlet (Org) Solvent 
______________________________________ 
Ti V Fe H.sub.2 SO.sub.4 
20%D2EHPA 
7.1 0.02 &lt;0.01 &lt;0.1 3% octanol diluted 
with kerosene 
______________________________________ 
Values in g/l 
- Scrubbing - 
V.sup.4+, Fe.sup.3+ and Mn.sup.2+ ions, which are extracted in the low 
concentration of free acid, coextracted with Ti.sup.4+ ions into the 
organic solvent (B) are scrubbed from the organic solvent (B) by contact 
with of HCl, H.sub.2 SO.sub.4 or HNO.sub.3, but Ti.sup.4+ and Cr.sup.3+ 
ions are not scrubbed. 
______________________________________ 
Scrubbing test with 15% HCl 
Metallic ions 
Flow 
concentration 
ratio shaking 
Back- 
in the org. phase 
O/A Temp. time extraction % 
______________________________________ 
Mn.sup.2+ 
0.2 g/l 1.0 Room temp. 
15 min. 
99.5% 
V.sup.4+ 
0.5 g/l 1.0 " " 99.0% 
Fe.sup.3+ 
1.0 g/l " " " 98.5% 
Cr.sup.3+ 
0.5 g/l " 60.degree. C 
30 min. 
0% 
Ti.sup.4+ 
7.0 g/l " Room temp. 
" 0% 
______________________________________ 
The organic solvent (B) extracted Ti ions are scrubbed by contact of HCl, 
H.sub.2 SO.sub.4 or HNO.sub.3 to remove V.sup.4+ and Mn.sup.2+ ions, etc. 
coextracted with Ti.sup.4+ ions into the organic solvent (B). The 
selection of HCl, H.sub.2 SO.sub.4 or HNO.sub.3 as a scrub solution is 
done after consideration of the finished recovery form of scrubbed V and 
Mn, etc. The organic solvent (B) after the scrubbing process includes only 
Ti.sup.4+ ions, but includes also Cr.sup.3+ ions provided that the first 
stage is omitted. 
- Continuous scrubbing test - 
The apparatus for the test is the same one used for the extraction process 
and the flow rates of organic aqueous phases are 0.5 l/min. and 0.05 
l/min., respectively. 
______________________________________ 
The third stage - Scrubbing 
Flow Outlet Outlet 
Appa- ratio Inlet (Org) 
(Org) (Aq) 
ratus O/A Ti V Ti V Ti V Note 
______________________________________ 
5 Stage Temp.: 35.degree. C 
mixer- 
10/1 7.10 0.02 7.10 0.01 -- 0.2 Scrub sol. 
settler : 15% HCl 
______________________________________ 
Values in g/l 
- Stripping - 
Ti.sup.4+ ions in the organic solvent (B) after the scrubbing process are 
stripped in the following stripping process. 
Back-extraction test of Ti ions with various back-extraction solutions 
Flow ratio : 0/A = 1/1, Shaking time: 15 min. Temp.: Room temp. 
______________________________________ 
Back- Back-ex- 
extraction % traction % 
______________________________________ 
6N H.sub.2 SO.sub.4 
0 0.5 N HF 64.71 
12N H.sub.2 SO.sub.4 
0 0.5N NH.sub.4 F 75.03 
6N HCl 0 6N H.sub.2 SO.sub.4 +1% H.sub.2 O.sub.2 
36.04 
12N HCl 0 (NH.sub.4).sub.2 SO.sub.4 
0 
4N HNO.sub.3 
0 (NH.sub.4).sub.2 SO.sub.4 + NH.sub.3 
98.0 
8N HNO.sub.3 
0.4 Saturated (NH.sub.4).sub.2 CO.sub.3 
99.5 
11N H.sub.3 PO.sub.4 
5.7 1M (NH.sub.4).sub.2 CO.sub.3 + NH.sub.3 
99.5 
______________________________________ 
It is considered from the result of the back-extraction test that 0.5 M - 
saturated (NH.sub.4).sub.2 CO.sub.3 + NH.sub.3 solutions with pH values 
maintained between 7 and 9.5 and over 2 M(NH.sub.4).sub.2 SO.sub.4 + 
NH.sub.3 solutions with pH values maintained over 7.0 are the most 
suitable back-extraction solutions of Ti ions from the standpoint of cost 
and subsequent operations. Therefore, the mechanism of the back-extraction 
of Ti ions is shown as follows. 
__________________________________________________________________________ 
Ti [(RO).sub.2 POO].sub.4 
+ 2 (NH.sub.4).sub.2 CO.sub.3 
+ 4 NH.sub.4 OH 
.revreaction. 
Ti(OH).sub.4 + 
(Org) (Aq) (Aq) (ppt) 
4 [(RO).sub.2 POONH.sub.4 ] 
+ 2 (NH.sub.4).sub.2 CO.sub.3 
(see FIG. 8) 
(Org) (Aq) 
__________________________________________________________________________ 
As shown in the above formula, (NH.sub.4).sub.2 CO.sub.3 used for the 
back-extraction forms HCO.sub.3.sup.- ion in the back-extraction of Ti and 
HCO.sub.3.sup.- ion formed reacts with NH.sub.3 to form (NH.sub.4).sub.2 
CO.sub.3 again. 
______________________________________ 
The third stage - Stripping 
Flow Inlet Outlet 
Outlet 
ratio (Org (Org) (Aq) 
Apparatus 
O/A Ti Ti Ti Note 
______________________________________ 
5 Stage- 1M(NH.sub.4).sub.2 CO.sub.3 
mixer- 1/1 7.10 0.01 7.10* + NH.sub.3 
settler pH: 9.5 
Temp.: 23.degree. C 
______________________________________ 
Remark : The value of Ti* in the back-extraction solution is one obtained 
the remelting the precipitate as Ti(OH).sub.4. 
As the organic solvent (B) becomes the NH.sub.4 type by stripping Ti ions, 
it is converted to the H type by with contact of H.sub.2 SO.sub.4 or HCl 
in the following process. When Cr.sup.3+ ions are coextracted, Cr.sup.3+ 
ions are stripped by contact with of H.sub.2 SO.sub.4 + H.sub.2 O.sub.2, 
HCl + H.sub.2 O.sub.2 or HCl + NaCl solution and then the NH.sub.4 type of 
the organic solvent (B) is converted to the H type. (see FIG. 9). 
(4) The Fourth Stage 
- Extraction - 
Fe.sup.2+ ions in the resulting solution in which Ti ions are separated are 
converted to Fe.sup.3+ ions with H.sub.2 O.sub.2, oxygen, high pressure 
air or electro-oxidation and Fe.sup.3+ ions in the resulting aqueous 
solution are extracted into the organic phase with the organic solvent 
(C). The organic solvent (C) is composed of alkyl phosphoric acid, for 
example, D2EHPA, mixed solvent of alkyl phosphoric acid and LIX-63 
(tradename, chelate reagent produced by General Mills) or .alpha.-bromo 
lauric acid, 2 - 5% higher alcohol as a modifier and aromatic, aliphatic 
or paraffin hydrocarbon as a diluent. 
The extraction mechanism of Fe.sup.3+ ion with alkyl phosphoric acid is 
shown as follows. (See FIG. 10) 
______________________________________ 
Fe.sup.3+ 
+ 3 [(RO).sub.2 POOH] 
= Fe [(RO).sub.2 POO].sub.3 
+ 3 H.sup.+ 
(Aq) (Org) (Org) (Aq) 
______________________________________ 
While, Fe.sup.2+ ions are oxidized to Fe.sup.3+ ions using Cl.sub.2 gas and 
Fe ions are extracted into the organic phase with the organic solvent (E) 
after adding HCl to the resulting aqueous solution in an amount enough to 
extract the Fe.sup.3+ ions as an Fe chloride complex. The organic solvent 
(E) is made up of phosphoric acid ester, for example, TBP (tri-butyl 
phosphoric acid), TOP (tri-octyl phosphoric acid), DBBP (di-butyl butyl 
phosphonate) or TOPO (tri-octyl phosphine oxide) and aromatic, aliphatic 
or paraffin hydrocarbons as a diluent. Moreover, the organic solvent (E) 
may be made up of primary, secondary, tertiary or quaternary amine, higher 
alcohol as a modifier and aromatic, aliphatic, or paraffin hydrocarbons as 
a diluent. The test used Primene-JMT as a primary amine, LA-1 as a 
secondary amine, Alamine 336 as a tertiary amine and Aliquat 336 as a 
quaternary amine. Of course, similar amines can be utilized besides the 
amines described above. Furthermore, mixed solvent of phosphoric acid 
ester, such as, TBP and tertiary amine such as TOA (tri-octyl amine) can 
be used. Fe ions are extracted into the organic phase with phosphoric acid 
ester or amine according to the following formulas. 
__________________________________________________________________________ 
FeCl.sub.3 
+ H.sup.+ 
+ Cl.sup.- 
+ 2TBP 
.revreaction. 
HFeCl.sub.4 . 2TBP 
(Extraction by TBP 
see FIG. 12) 
(Aq) (Aq) 
(Aq) (org) (Org) 
FeCl.sub.4.sup.- 
+ (R.sub.3 NH).sup.+ 
.revreaction. 
(R.sub.3 NH).sup.+ . FeCl.sub.4.sup.- 
(Extraction 
by tertiary 
(Aq) (Org) (Org) amine. see FIG. 12) 
__________________________________________________________________________ 
- Stripping - 
Fe.sup.3+ ions extracted into the organic phase with the organic solvent 
(C) are stripped from the organic phase with HCl and the organic solvent 
(C) is regenerated as shown in the following formula. 
__________________________________________________________________________ 
Fe[(RO).sub.2 POO].sub.3 
+ 3HCl 
.revreaction. 
FeCl.sub.3 
+ 3[(RO).sub.2 POOH] 
(see FIG. 13) 
(Org) (Aq) (Aq) (Org) 
__________________________________________________________________________ 
While, Fe chloride complex extracted into the organic phase with the 
organic solvent (E) is stripped from the organic phase with water and the 
organic solvent (E) is regenerated according to the following formulas 
(see FIG. 14). 
______________________________________ 
HFeCl.sub.4 . 2TBP 
+ H.sub.2 O 
.revreaction. 
FeCl.sub.3 
+ HCl + TBP 
(Org) (Aq) (Aq) (Aq) (Org) 
(R.sub.3 NH.sup.+). FeC1.sub.4.sup.- 
+ H.sub.2 O 
.revreaction. 
FeCl.sub.3 
+ HCl + R.sub.3 N 
(Org) (Aq) (Aq) (Aq) (Org) 
______________________________________ 
- Continuous extraction and stripping test - 
The apparatus used for the test is the same one used in the first stage. 
The flow rate of organic and aqueous phases were 0.1 l/min. 
__________________________________________________________________________ 
Extraction 
Appara- 
Flow ratio 
Inlet(Aq) 
Outlet(Aq) 
Outlet(Org) 
tus O/A Fe H.sub.2 SO.sub.4 
Fe H.sub.2 SO.sub.4 
Fe H.sub.2 SO.sub.4 
Note 
__________________________________________________________________________ 
10 Stage 30% D2EHPA 
mixer- 
3/1 31.8 
300 &lt;0.01 
300 10.6 
&lt;0.01 
3% decanol 
settler kerosene 
15 Stage 
mixer- 
4/1 31.8 
300 &lt;0.01 
300 7.94 
&lt;0.01 
15% TBP 
settler kerosene 
__________________________________________________________________________ 
values in g/l - 
Stripping 
Appara- 
Flow ratio 
Inlet(Org) 
Outlet(Org) 
Outlet(Aq) 
tus O/A Fe HCl Fe HCl Fe HCl Note 
__________________________________________________________________________ 
10 Stage 
mixer 
settler 
1.5/1.0 
10.6 
-- 0.1 -- 15.9 
150 Room temp. 
150 g/l HCl 
" 10/1 7.94 
20.5 
0.6 1.5 73.4 
189 60.degree. C 
H.sub.2 O 
__________________________________________________________________________ 
Values in g/l 
(5) The Fifth Stage 
- Extraction - 
The resulting aqueous solution extracted off Fe.sup.3+ ions contains a 
small amount of Al.sup.3+, Mg.sup.2+, Mn.sup.2+ and V.sup.4+ ions and is 
reused for dissolution of Ti raw materials through the concentration 
process. However, since these metallic ions are gradually accumulated in 
the recycling process, it is necessary to take them out the system and to 
prevent their accumulation. When acid is taken out the system or is 
recycled to reuse, it is connected with the improved economization of the 
apparatus to extract and recover the V.sup.4+ ions which have an 
economical value among them. 
In the case of recycling for reuse, VO(SO.sub.4).sub.2.sup.- ions in the 
resulting aqueous solution which has no Fe ions and 300 - 500 g/l of free 
acid are extracted into the organic phase by contact of the organic 
solvent (D). (see FIG. 15). In the other case of taking acid out the 
system, VO.sub.3.sup.- ions in the aqueous solution, whose pH values are 
maintained between 2 and 4 with NH.sub.3, are extracted into the organic 
phase with contact of the organic solvent (D). FIG. 16 shows the relation 
between the pH and V extraction coefficient. 
The organic solvent (D) is made up of primary, secondary, tertiary or 
quaternary amine, 2 - 5% higher alcohols such as, octanol, decanol or 
isodecanol as a modifier and aromatic, aliphatic or paraffin hydrocarbons 
as a diluent. The amines used for the test are Primene-JMT as a primary 
amine, LA-1 as a secondary amine, Alamine 381 (tri isooctylamine produced 
by Ashland Chemical Co.) as a tertiary amine and Aliquat 336 as a 
quaternary amine. Of course, various similar amines can be commonly 
utilized besides the amines mentioned above. 
- Stripping - 
VO(SO.sub.4).sub.2.sup.- ions extracted into the organic solvent (D) are 
stripped from the organic phase with the contact of (NH.sub.4).sub.2 
SO.sub.4. While, VO.sub.3.sup.- ions extracted into the organic solvent 
(D) can be stripped with NH.sub.4 Cl + NH.sub.3 (see FIG. 17). Both types 
of V ions are recovered as the form of NH.sub.4 VO.sub.3. 
(6) The Treatment of By-product FeSO.sub.4.nH.sub.2 O 
The H.sub.2 SO.sub.4 concentration produced after the extraction of 
Fe.sup.3+ ions and almost all heavy metallic ions in the fourth stage is 
250 - 300 g/l and consequently this low concentration of H.sub.2 SO.sub.4 
enhances the energy cost of the concentration to reuse for the dissolution 
of raw materials, through the concentration process. The H.sub.2 SO.sub.4 
concentration is increased by dissolving FeSO.sub.4.nH.sub.2 O by-produced 
in the pretreatment process into the aqueous solution from which the 
Fe.sup.3+ ions are removed in order to reduce this energy cost. The 
several repetitions of the above operation in accordance with the demand 
can diminish the energy cost of concentration. The relation between the 
H.sub.2 SO.sub.4 concentration and the Fe.sup.3+ ions extraction 
coefficient is shown in FIG. 18. 
FeSO.sub.4.nH.sub.2 O often includes MnSO.sub.4. As shown in the flow-sheet 
of FIG. 2, Mn.sup.2+ ions are separated from Fe.sup.2+ ions by extracting 
Mn.sup.2+ ions by contact of the organic solvent (F) in the lower 
concentration of free acid produced by the dissolution of the 
FeSO.sub.4.nH.sub.2 O crystals with water (see FIG. 19). 
The organic solvent (F) is composed of alkyl phosphoric acid, for example, 
D2EHPA, H.sub.2 DDP, 2 - 5% higher alcohol as a modifier and aromatic, 
aliphatic or paraffin hydrocarbons as a diluent. While, the organic 
solvent (F) may be made up of mixed solvent of D2EHPA and LIX-63 or 
primary, secondary, tertiary or quaternary amine. As described above, the 
mixed solvents consisted of mainly alkyl phosphoric acid and 5 - 20% of 
LIX-63, aliphatic hydroxy oxime or .alpha.-bromo lauric acid are used to 
extract Mn ions. 
A small amount of Fe.sup.2+ ions coextracted with Mn.sup.2+ ions are 
scrubbed from the organic solvent (F) with contact of MnSO.sub.4 solution 
having 2 - 3.5 of pH values, the organic solvent (F) contains only Mn ions 
and consequently Mn.sup.2+ ions are stripped from the organic solvent (F) 
with 300 g of H.sub.2 SO.sub.4 in the following process. 
- Continuous extraction test - 
The continuous extraction test using the under-tabulated 
FeSO.sub.4.nH.sub.2 O by-produced by the H.sub.2 SO.sub.4 process was done 
and MnSO.sub.4 was added to the resulting solution in order to facilitate 
the confirmation of the Mn extraction. 
______________________________________ 
Chemical analysis of FeSO.sub.4 . nH.sub.2 O 
FeO TiO.sub.2 
MnO 
______________________________________ 
24.96% 0.22% 0.06% 
______________________________________ 
The pH value in dissolving 250 g of the above crystal with 1 liter of water 
was 1.8 and the chemical composition of the resulting solution to which Mn 
was added was shown as follows. 
__________________________________________________________________________ 
Total H.sub.2 SO.sub.4 
Fe Mn Ti (Values in g/l) 
90.7 48.8 2.0 0.3 
__________________________________________________________________________ 
Extraction 
Flow ratio Inlet(Aq) Outlet(Aq) Outlet(Org) 
Apparatus 
0/A Fe Mn Ti Fe Mn Ti Fe Mn Ti Note 
10 Stage 
4/1 48.8 
2.0 0.3 48.4 
0.1 Tr 0.1 0.49 
0.1 20% 
mixer- D2EHPA 
settler 
" 2/1 48.8 
2.0 0.3 48.6 
0.1 Tr Tr 1.0 0.15 
10% LIX 
63+10% 
D2EHPA 
__________________________________________________________________________ 
Values in g/l 
Fe.sup.2+ ions are coextracted with Mn.sup.2+ ions from pH values between 
3.5 and 3.8. In this case, Fe.sup.2+ ions extracted into the organic phase 
are scrubbed from the organic solvent (F) with MnSO.sub.4 solution having 
a pH value of 2 - 2.5 and the concentraton of Mn in the MnSO.sub.4 
solution depends on the concentration of the organic solvent (F). (see 
FIG. 20) 
__________________________________________________________________________ 
Stripping 
Flow ratio Inlet(Org) Outlet(Org) (Outlet(Aq) 
Apparatus 
O/A Fe Mn Ti Fe Mn Ti Fe Mn Ti 
__________________________________________________________________________ 
5 Stage 
10/1 0.1 0.49 
0.1 -- 0.06 
0.6 -- 4.8 -- 300g/l 
mixer- H.sub.2 SO.sub.4 
settler 
" 10/1 Tr 1.0 0.15 
-- 0.01 
0.15 
-- 9.9 -- 
__________________________________________________________________________ 
Values in g/l 
Ti ions in the organic solvent (F) are not stripped and the organic solvent 
(F) is recycled. Since the Ti concentration gradually increases, one part 
of the organic solvent (F) is taken out the system and Ti ions in it are 
stripped from the organic phase with contact of the (NH.sub.4).sub.2 
CO.sub.3 + NH.sub.4 OH solution. 
(7) The Recovery of HCl by Diaphragm -- Electrolysis 
As the concentration of Fe.sup.3+ ions in the back-extraction solution of 
the organic solvent (C) including Fe.sup.3+ ions is impossible to be 
increased as shown in FIG. 13, the introduction of the above 
back-extraction solution into the apparatus of the recovery by the 
thermal-decomposition process enhances the energy cost of the recovery and 
consequently the back-extraction solution is introduced into the cathode 
compartment of diaphragm-electrolysis, and free HCl produced there by the 
reduction of FeCl.sub.3 to FeCl.sub.2 is transferred to the anode 
compartment and recovered. 
- Continuous electrolysis test - 
The back-extraction solution of the organic solvent (C) is fed into the 
cathode compartment by a quantitative pump and the aqueous solution of low 
HCl concentration, which is the back-extraction solution of the organic 
solvent (C) and contains no Fe ions, is fed into the anode compartment. 
______________________________________ 
Electrolysis condition 
Material of diaphragm : 
Film of Tetra-fluo ethylene 
Thickness of diaphragm : 
0.103 mm 
Void percent diaphragm : 
55 % 
Hole diameter diaphragm : 
0.3.mu. 
Water permeability : 
0.48 ml/cm.sup.2 H 
diaphragm 
Electric resistance : 
0.1 .OMEGA.-cm.sup.2 
Anode : carbon Cathode : 
Ti (Pt plating) 
Volume of anode or cathode room : 
5l 
Temperature : 24 - 55.degree. C 
Current density : 2 A/dm.sup.2 
______________________________________ 
- Continuous test at steady state - 
Cathode room 
Anode room 
Inlet Outlet Inlet Outlet 
______________________________________ 
Fe.sup.3+ 
(g/l) 18.0 0.4 0 -- 
Fe.sup.2+ 
(g/l) -- 21.0 0 -- 
HCl (g/l) 176 27.4 50 178.0 
Liquor 
volume (1/H) 5.0 4.3 5.0 5.7 
______________________________________ 
The following diaphragms besides the one described above were used. 
__________________________________________________________________________ 
Material Electric resistance 
Hole dia. 
Void % 
Water permeab. 
__________________________________________________________________________ 
Acetic cellose 
0.05 - 0.19.OMEGA.-cm.sup.2 
0.1 - 0.4.mu. 
58 - 62% 
0.11-0.3 ml/cm.sup.2 
Polypropylene 
0.12 - 0.27.OMEGA.-cm.sup.2 
0.2 - 0.4" 
38 - 45% 
0.02-0.2 ml/cm.sup.2 
Ion exchange 
cm.sup.2 1.7 - 3.2 .PSI. 
Water content : 38% 
membrane 
__________________________________________________________________________ 
The back-extraction solution of the organic solvent (E) is the concentrated 
solution containing 75 - 85 g/l of Fe and 200 - 240 g/l of HCl as 
described above. However, it is considered that the energy cost of free 
HCl recovery by reduction of Fe.sup.2+ ions in the electrolysis process 
becomes lower than that by thermal-decomposition process because free HCl 
exists in the back-extraction solution of the organic solvent (E). As for 
the ion exchange membrane, any ion exchange membrane may be used. 
The solution containing Fe.sup.2+ ions, which consists of the solution of 
Fe.sup.2+ ions produced by electro-reduction of Fe.sup.3+ ions (FeCl.sub.3 
.fwdarw. FeCl.sub.2 + Cl) and the solution which is recovered by 
transferring the solution, containing abundant HCl unused in the 
back-extraction, into the anode compartment are converted to FeCl.sub.3 by 
the oxidation with air or oxygen and one part of the Fe ions is 
precipitated and separated as hydrated Fe oxide or hydroxide according to 
the following formula. 
EQU 2 FeCl.sub.2 + O + H.sub.2 O = FeCl.sub.3 + HCl + FeO(OH) 
Both HCl and FeCl.sub.3 produced in the above formula are introduced again 
into the cathode compartment of the electrolysis process and HCl and 
Cl.sup.- which are transferred to the anode compartment are recovered by 
reduction of Fe.sup.3+ ions to Fe.sup.2+ ions. When there is the 
apparatus of thermal-decomposition, Fe.sub.2 O.sub.3 and HCl can be 
obtained by thermal-decomposition of the concentrated solution produced 
through several electrolysis processes from the viewpoint of 
water-balance. 
Both Fe.sub.2 O.sub.3 and FeO(OH) obtained as mentioned above are high 
purity and can be utilized for ferrite and pigment without further 
purification. 
The production of TiO.sub.2 based on this invention has the following 
advantages. 
(1) The adoption of this production method has the extreme advantages in 
the anti-pollution and economical cost by working out the problem of 
FeSO.sub.4.nH.sub.2 O -- treatment which has been the most troublesome 
process. 
(2) The recovery of valuable metals, such, as V, Nb and Mn, etc., contained 
in a small amount is possible by regenerating and reusing the waste acid 
economically, including a large amount of heavy metal ions in 20 - 40% 
H.sub.2 SO.sub.4 after the hydrolysis process. The product of the 
individual valuable metal is recovered in high purity. 
(3) The metals such as, Cr whose existence in the raw materials is 
undesirable can be fractionally recovered with solvent extraction 
techniques from the aqueous solution before the hydrolysis process and 
consequently the selection of the raw materials is very easy. 
(4) The product-purity of the hydrated Fe oxide and hydroxide by-produced 
in the acid recovery process is very high as used not only pig iron -- raw 
materials, but also for valuable ferrite or pigment and consequently the 
economical value is enhanced. 
(5) The whole system is built up as a closed-circuit and the protection of 
the environment is possible because the great part of the used reagent is 
recovered or used as a product.