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Extraction of lithium from the dead sea
Hydrometallurgy, 6 (1981) 269--275
269
Elsevier Scientific Publishing Company, Amsterdam - - P r i n t e d in The Netherlands
EXTRACTION OF LITHIUM FROM THE D E A D SEA
J.A. EPSTEIN, E.M. FEIST and J. ZMORA
Dead Sea Works, Beer-Sheba (Israel) and Y. MARCUS
Department of Inorganic and A naly tical Chemistry, The He brew University of Jerusalem, Jerusalem (Israel) (Received February 6th, 1979; accepted in revised form September 25th, 1980)
ABSTRACT Epstein, J.A., Feist, E.M., Zmora, J. and Marcus, Y., 1981. Extraction of lithium from the Dead Sea. HydrometaUurgy, 6: 269--275. Present and future uses of lithium and its compounds are briefly reviewed. A method for the extraction of lithium from the Dead Sea involving its precipitation as lithium altiminate followed by solvent extraction to separate the lithium from aluminium is described. An economic evaluation of the m e t h o d is given.
INTRODUCTION
General interest in the diversification of commercial lithium sources has been increasing in recent years owing to the versatility of the present uses of the metal and its c o m p o u n d s and the prospects of expanding future uses [ 1 ] . The Dead Sea may become a source of lithium, provided an economically viable process can be developed. The present paper describes a possible method for extracting the element from the Dead Sea. A general background on the present and future uses of lithium and its c o m p o u n d s is also given. USES OF LITHIUM AND LITHIUM COMPOUNDS [ 2 ]
The most w i d d y used lithium salt is the carbonate (Li2COa). Its applications include addition as a flux to vitreous enamelling of steel for use mainly in household applications and to the glass lining of water heaters and various other grades of glass. It is also used in medicine for the treatment of certain mental diseases, and in metallurgy as an additive to fused salt baths in the production of aluminium and magnesium. Lithium hydroxide (Li OH) is used in the manufacture of lithium soaps. These c o m p o u n d s are able to withstand extreme environmental conditions such as heat, cold, water and high pressures, and are therefore usefully em-
0304-386X/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
270
ployed as greases for systems where such conditions are met. The anhydrous hydroxide is used as an absorbent for carbon dioxide in space-craft and submarines. Lithium bromide (LiBr) has a high water solubility. The concentrated solutions have very low vapour pressures and are used in absorption type refrigeration systems. They are specially suitable for operating absorption units in conjunction with solar energy collectors. Lithium chloride (LiC1) solutions are used in commercial dehumidifying equipment. Lithium hypochlorite (LiOC1) is used in a spray
Lithium appears in several minerals and lake brines. The main minerals are: Spodumene -- lithiumssodium-aluminium silicate (Li,Na)AI(SiO3)2 Petalite -- also a silicate of sodium, lithium and aluminium Lepidolite -- "lithium mica" -- a mineral of variable composition, usually K4Li4(A1,Fe)3-A14(Si3Os) (SIO4)3 Amblygonite - - a lithium-aluminium fluoride and phosphate Li,AI(F,OH)PO4. According to Vine [1] the U.S. resources may be divided into three categories: (1) Proven reserves, extraction economical at current prices (up to 50% recovery) 230,000 tons (2) Poor reserves, extraction may become economical in the future (up to 30% recovery) 300,000 tons (3) Hypothetical resources, require development, (up to 50% recovery) 470,000 tons Main reserves in other countries are: Canada 153,000 tons Zimbabwe/Rhodesia 81,000 tons Chile 1,200,000 tons Zaire 1,000,000 tons at 15% estimated recovery 617,000 tons Total recoverable lithium
1,617,000 tons
271 Present annual demand is 4000 tons of lithium (as metal). Therefore these reserves are ample to cover world demand for all the conventional uses mentioned above. But if lithium based fuel cells come into widespread use and fusion processes are to become the ultimate source of energy to replace fossil fuels and fission reactors based on uranium, these quantities will n o t be sufficient. In such cases secondary, poorer sources of lithium minerals such as clays, will become of industrial importance and the extraction of the metal from t h e m will be realized. THE DEAD SEA AS A SOURCE OF LITHIUM
The Dead Sea is a saturated solution of sodium chloride containing also the chlorides and bromides of magnesium, calcium and potassium, and to a lesser extent a series of other elements including lithium [3] whose concentration in the sea water is 18 ppm. Dead Sea Works applies a process of solar evaporation to separate from the sea water sodium, potassium and magnesium chlorides. During evaporation and crystallizationof salts,the lithium remains in solution and its concentration in the "end brines" rises to 40 ppm. The total amount of the element in the Dead Sea is 2.7 × 106 tons, and the annual quantity carried through the evaporation-pan system of the Dead Sea Works is 4000 tons. Earlier work in the research laboratories of Dead Sea Works [4] forms the basis for a process to extract lithium from the Dead Sea. A n aluminium salt, preferably the chloride, is dissolved in the sea brine and an alkaline reagent is added to raise the p H up to the point of precipitation of aluminium hydroxide. The precipitate contains a considerable proportion of the lithium content of the original brine, and most of it remains strongly held on the solid alumina phase even after repeated washings. Recent work by Frenkel, Glasner and Sarig [5] at the Casali Institute of Applied Chemistry indicates that a definite crystalline structure involving both lithium and aluminium oxides is formed. Attempts to increase the amount of lithium absorbed on the precipitate by repeated contact of the solid phase with fresh portions of Dead Sea brines at controlled p H values [6] have shown that the m a x i m u m molar ratio of Li20 :A1203 attainable is 1:5. These results seem to indicate that the solid phase formed m a y be a low temperature variety of the well known zetaalumina structure, LiAlsOs, described by Datta and Roy [7]. The solids, after separation by conventional means, are dissolved in aqueous hydrochloric acid. Lithium chloride can be extracted from aqueous brines containing chlorides by means of water-immiscible alcohols or similar solvents, provided the chloride ion concentration.is sufficiently high, and the water activity is sufficiently low. The selectivity of the extraction depends on the cations presents: potassium, calcium and aluminium salt the lithium chloride out, while sodium and magnesium salt it in. Being themselves extracted, they provide the necessary counter-ions and reduce the lithium extraction by the c o m m o n (chloride) ion
272
effect. An excess of hydrogen ions must also, of course, be avoided. It is therefore necessary to dissolve the lithium aluminate concentrate in the minimal a m o u n t of hydrochloric acid and to concentrate the brine to the maximum extent possible. The composition of the brine then corresponds to a solution 2.96 molal in AIC13, 0.25 molal in MgC12 and 0.47 molal in LiC1 (the other components being of no consequence), of total chloride molality of 9.9 and molal ionic strength of I = 19.0. This would constitute the feed solution to the solvent extraction unit. Information on such an extraction system involving isoamyl alcohol (3methylbutanol) is partly available in the study of Kuznetsova and Panchenkov [ 8 ] , who found a distribution coefficient for LiC1 of DLicl = 0.016 from 2--5 M A1C13. Marcus et al. [9] found DLiCl = 0.66 and an enrichment factor relative to MgC12 of 18.5 for extracting with isoamyl alcohol from Dead Sea end-brines, containing mainly 4 M MgC12 and 1 M CaC12. They tested also 4-hexanol, 2-ethylhexanol and methyl isobutyl ketone, among m a n y other solvents, and showed t h a t these perform similarly to isoamyl alcohol. From other relevant studies [10--14] it is concluded that magnesium chloride will coextract with lithium chloride, but that aluminum chloride will hardly do so at all. A simultaneous solution of the following two equations will give the necessary information on the extraction: m L i m c l ~ L i C l = K L i c l m L i m C l ~ + LiCl MgHtCl / ±MgCI 2 =
Kmgc12mmgm~l~'3_+MgCl~
(1)
(2)
with rncl = rnLi + 2~7~Mg and mcl = 3mAl + 2mMg + mLi. The activity coefficients in the aqueous solutions refer to the mixed solution, but can be obtained from those in binary solution "/±°LiCb7°±MgCI~ and 7°±AlCh at the ionic strength I of the mixture, by the method of Lietzke and Stoughton [15] o o lnT±i = lnT~ + 0. 5 ~ iyi(zizi -IlnT±i -- lnT_+i )
(3)
where z is the charge and y the ionic strength fraction of the designated electrolyte. The extraction constants have been given as [15] KLtc~ = 4.9 × 10 -s and as [16] KMgch = 2 × 10 -s. The activity coefficients of the salts in the organic phase can be expressed in power series of inn from extraction data for binary solutions [16], assumed to apply also for mixtures. Organic solutions in equilibrium with the aqueous feed described above will have mLi = 0.35 and mMg = 0.07, i.e. a distribution ratio DLi = 0.74 and an enrichment factor relative to magnesium of ca. 2.7. Contact of this organic solution with an equal volume of water will strip both salts practically completely.
273 DETAILED DESCRIPTION OF PROCESS (see the flow sheet in Fig. 1)
Precipitation Aqueous aluminium chloride recycled from a later stage, plus some makeup to cover losses is mixed with Dead Sea brine and calcium hydroxide slurry keeping the pH constant between 6.8--7.0. The solid phase is separated by thickening and filtration giving a lithium concentrate containing 0.064% Li on a dry basis.
Washing The concentrate is washed with water in a three~tage countercurrent washing system to remove soluble salts, mainly magnesium and calcium chlorides. The residual wash water containing 27 p p m lithium may be concentrated by solar evaporation and returned to the precipitation stage. The final concentrate from the washing has the following composition: Al:O3 Li20 MgC12 CaC12 (K+Na)C1 H20
3.68% 0.18% 0.6% 0.1% 0.05% balance
1
(Molar ratio A1203:Li20
Ca(OH)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SOLAR
6:1)
=
LREJECTWASH ._WATER
EVAPORATION| . . . . . . . • . . . . . . WASTE TIDEPLETED BRINE 1 DEAD SEAl , I I , l - - ----~PRECIPITATION~--~ITHICKENING I---------~IFILTRATION ~ BRINE
I
I
I
I
l
I
•
I
3-STAGE
L ..........
[WASHIN . . .G. . . . . . . ANDI
AICI3 / MAKE Up = e
AICI 3 RECYCLE '
WATER
LI
/
:i FILTRATION /
F LTRAT ON H
.
I /
1
I T
LITHIUMI IELECTROLYS~S ~ METAL ' I
',[__1
"°' °'DISSOLUTIONi
Cl
[
EVAPORATIONL - - - ~ L - LIQUID- LIQUID'~I CONCENTRATIONI J . I SOLUTION E X T R A C T I O N J I
Fig. 1. F l o w sheet of lithium production.
' '
274
Dissolution and concentration The concentrate is dissolved in hydrochloric acid giving a brine with the following composition: Salt:
AIC13 M g C 1 2
C a C 1 2 (K+Na)C1
LiCI
g/kg
79
0.8
4.1
4.9
0.4
The brine is further concentrated up to the point of saturation. Solvent extraction The lithium and aluminium chlorides are separated from the concentrated brine by solvent extraction using one of the suitable solvents available such as n-hexanol, 2~ethylhexanol or methyl isobutyl ketone. The lithium-depleted aluminium chloride brine is recycled to the precipitation stage. Production o f lithium metal The aqueous solution of lithium chloride obtained in the solvent extraction stage may be used to make other commercially required lithium salts or dehydrated and electrolysed in a fused-salt bath to produce lithium metal. The production of lithium metal by electrolysis of the chloride in a bath of fused salts is a known process. ECONOMIC E V A L U A T I O N
The data available at this stage of development are not sufficient for a detailed economical evaluation. However, an approximate indication of cost should be available in order to form a basis for estimating the desirability of continuing to develop the process. The following evaluation is based on two hour~ residence time in the initial precipitation stage. Data are n o t available for a detailed cost estimate of the investment required in the solvent extraction and electrolysis stages, b u t it is quite obvious that owing to the much larger volumes involved in the precipitation and washing stages, the size of the equipment, and therefore the cost of it, for the latter stages would be relatively "very small. Therefore, only variable costs are considered for these parts. The production cost of $30/kg of lithium metal may be compared with the current selling price, which is also $30/kg. For a project at such an early stage of development, one would wish to arrive at a much lower figure in order to justify further development. On the other hand, the expectations of further depletion of lithium resources may, as indicated earlier, enhance the attractiveness of the process described above.
275
Lithium production - 50 tons/year of Li metal Investments 1. Precipitation stage 2. Washing, thickening and filtration + Running-in costs and interest during construction Variable and fixed costs Lime, 460 kg at $35 Hydrochloric acid, 576 kg at $30 Al chloride, 5% makeup at $200 Process water, 120 m3 h-’ at $0.1 1 m-’ Electricity for electrolysis of LiCl 18 kWh kg-’ Li at $0.04 kWh_’ Electricity for pumps and agitators Capital costs (23-25s) Operation and management Solvent extraction, $0.5 me3of aq. stream [17] Other expenses
$1,125,000 1,398,OOO Total 2,685,OOO $3,340,000 Annual costs $130,000 138,000 6,000 96,000 36,000 102,000 778,000 150,000 30,000 50,000 Total 1,516,OOO
Zest per kg of Li $30.00
iEFERENCES
1 Lithium Resources and Requirements in the Year 2000, Geological Survey Profession-
10 11 12 13 14 15 16 17
al Paper No. 1005, U.S. Govt. Printing Office, Washington, 1976. Smith, E.W., 2nd Industrial Minerals International Congress, Munich, 1976. Epstein, J.A., Hydrometahurgy, 2 (1976) l-10. Kaplan, D., Israel J. Chem., 1(1963) 115. Frenkel, M., Glasner, A. and Sarig, S., J. Phys. Chem., 84 (1980) 507-510. Forgacs, C. and Eiger, H., unpublished results. Datta, R.K. and Roy, R., J. Am. Ceram. Sot., 46(8) (1963) 388. Kuznetsova, E.M. and Panchenkov, G.M., Zh. Fiz. Khim., 40 (1966) 481. Marcus, Y., Ben-Zwi, N. and Blinderman, J.M., Israel J. Chem., 10 (proc.) (1972) 161; J.M. Blinderman, M.Sc. thesis, Hebrew Univ., Jerusalem, 1972. Rozen, A.M. and Mikhalichenko, A.I., Russ. J. Inorg. Chem., 12 (1967) 380. Azarova, L.A. and Vinogradov, E.E., Zh. Neorg. Khim., 21 (1976) 2484. Vinogradov, E.E., Zh. Neorg. Khim., 12 (1967) 1930. Krasnov, K.S. and Kazas, T.S., Radiokhimiya, 14 (1972) 246. Kazas, T.S. and Krasnov, K.S., Izv. Vyssh. Ucheb. Zav. Khim. i Khim. Teknol., 17 (1974) 209. Lietzke, M.H. and Stoughton, R.W., J. Soln. Chem., 1 (1972) 299. Marcus, Y., unpublished results, 1977. Barnea, E., private communication.
269
Elsevier Scientific Publishing Company, Amsterdam - - P r i n t e d in The Netherlands
EXTRACTION OF LITHIUM FROM THE D E A D SEA
J.A. EPSTEIN, E.M. FEIST and J. ZMORA
Dead Sea Works, Beer-Sheba (Israel) and Y. MARCUS
Department of Inorganic and A naly tical Chemistry, The He brew University of Jerusalem, Jerusalem (Israel) (Received February 6th, 1979; accepted in revised form September 25th, 1980)
ABSTRACT Epstein, J.A., Feist, E.M., Zmora, J. and Marcus, Y., 1981. Extraction of lithium from the Dead Sea. HydrometaUurgy, 6: 269--275. Present and future uses of lithium and its compounds are briefly reviewed. A method for the extraction of lithium from the Dead Sea involving its precipitation as lithium altiminate followed by solvent extraction to separate the lithium from aluminium is described. An economic evaluation of the m e t h o d is given.
INTRODUCTION
General interest in the diversification of commercial lithium sources has been increasing in recent years owing to the versatility of the present uses of the metal and its c o m p o u n d s and the prospects of expanding future uses [ 1 ] . The Dead Sea may become a source of lithium, provided an economically viable process can be developed. The present paper describes a possible method for extracting the element from the Dead Sea. A general background on the present and future uses of lithium and its c o m p o u n d s is also given. USES OF LITHIUM AND LITHIUM COMPOUNDS [ 2 ]
The most w i d d y used lithium salt is the carbonate (Li2COa). Its applications include addition as a flux to vitreous enamelling of steel for use mainly in household applications and to the glass lining of water heaters and various other grades of glass. It is also used in medicine for the treatment of certain mental diseases, and in metallurgy as an additive to fused salt baths in the production of aluminium and magnesium. Lithium hydroxide (Li OH) is used in the manufacture of lithium soaps. These c o m p o u n d s are able to withstand extreme environmental conditions such as heat, cold, water and high pressures, and are therefore usefully em-
0304-386X/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
270
ployed as greases for systems where such conditions are met. The anhydrous hydroxide is used as an absorbent for carbon dioxide in space-craft and submarines. Lithium bromide (LiBr) has a high water solubility. The concentrated solutions have very low vapour pressures and are used in absorption type refrigeration systems. They are specially suitable for operating absorption units in conjunction with solar energy collectors. Lithium chloride (LiC1) solutions are used in commercial dehumidifying equipment. Lithium hypochlorite (LiOC1) is used in a spray
Lithium appears in several minerals and lake brines. The main minerals are: Spodumene -- lithiumssodium-aluminium silicate (Li,Na)AI(SiO3)2 Petalite -- also a silicate of sodium, lithium and aluminium Lepidolite -- "lithium mica" -- a mineral of variable composition, usually K4Li4(A1,Fe)3-A14(Si3Os) (SIO4)3 Amblygonite - - a lithium-aluminium fluoride and phosphate Li,AI(F,OH)PO4. According to Vine [1] the U.S. resources may be divided into three categories: (1) Proven reserves, extraction economical at current prices (up to 50% recovery) 230,000 tons (2) Poor reserves, extraction may become economical in the future (up to 30% recovery) 300,000 tons (3) Hypothetical resources, require development, (up to 50% recovery) 470,000 tons Main reserves in other countries are: Canada 153,000 tons Zimbabwe/Rhodesia 81,000 tons Chile 1,200,000 tons Zaire 1,000,000 tons at 15% estimated recovery 617,000 tons Total recoverable lithium
1,617,000 tons
271 Present annual demand is 4000 tons of lithium (as metal). Therefore these reserves are ample to cover world demand for all the conventional uses mentioned above. But if lithium based fuel cells come into widespread use and fusion processes are to become the ultimate source of energy to replace fossil fuels and fission reactors based on uranium, these quantities will n o t be sufficient. In such cases secondary, poorer sources of lithium minerals such as clays, will become of industrial importance and the extraction of the metal from t h e m will be realized. THE DEAD SEA AS A SOURCE OF LITHIUM
The Dead Sea is a saturated solution of sodium chloride containing also the chlorides and bromides of magnesium, calcium and potassium, and to a lesser extent a series of other elements including lithium [3] whose concentration in the sea water is 18 ppm. Dead Sea Works applies a process of solar evaporation to separate from the sea water sodium, potassium and magnesium chlorides. During evaporation and crystallizationof salts,the lithium remains in solution and its concentration in the "end brines" rises to 40 ppm. The total amount of the element in the Dead Sea is 2.7 × 106 tons, and the annual quantity carried through the evaporation-pan system of the Dead Sea Works is 4000 tons. Earlier work in the research laboratories of Dead Sea Works [4] forms the basis for a process to extract lithium from the Dead Sea. A n aluminium salt, preferably the chloride, is dissolved in the sea brine and an alkaline reagent is added to raise the p H up to the point of precipitation of aluminium hydroxide. The precipitate contains a considerable proportion of the lithium content of the original brine, and most of it remains strongly held on the solid alumina phase even after repeated washings. Recent work by Frenkel, Glasner and Sarig [5] at the Casali Institute of Applied Chemistry indicates that a definite crystalline structure involving both lithium and aluminium oxides is formed. Attempts to increase the amount of lithium absorbed on the precipitate by repeated contact of the solid phase with fresh portions of Dead Sea brines at controlled p H values [6] have shown that the m a x i m u m molar ratio of Li20 :A1203 attainable is 1:5. These results seem to indicate that the solid phase formed m a y be a low temperature variety of the well known zetaalumina structure, LiAlsOs, described by Datta and Roy [7]. The solids, after separation by conventional means, are dissolved in aqueous hydrochloric acid. Lithium chloride can be extracted from aqueous brines containing chlorides by means of water-immiscible alcohols or similar solvents, provided the chloride ion concentration.is sufficiently high, and the water activity is sufficiently low. The selectivity of the extraction depends on the cations presents: potassium, calcium and aluminium salt the lithium chloride out, while sodium and magnesium salt it in. Being themselves extracted, they provide the necessary counter-ions and reduce the lithium extraction by the c o m m o n (chloride) ion
272
effect. An excess of hydrogen ions must also, of course, be avoided. It is therefore necessary to dissolve the lithium aluminate concentrate in the minimal a m o u n t of hydrochloric acid and to concentrate the brine to the maximum extent possible. The composition of the brine then corresponds to a solution 2.96 molal in AIC13, 0.25 molal in MgC12 and 0.47 molal in LiC1 (the other components being of no consequence), of total chloride molality of 9.9 and molal ionic strength of I = 19.0. This would constitute the feed solution to the solvent extraction unit. Information on such an extraction system involving isoamyl alcohol (3methylbutanol) is partly available in the study of Kuznetsova and Panchenkov [ 8 ] , who found a distribution coefficient for LiC1 of DLicl = 0.016 from 2--5 M A1C13. Marcus et al. [9] found DLiCl = 0.66 and an enrichment factor relative to MgC12 of 18.5 for extracting with isoamyl alcohol from Dead Sea end-brines, containing mainly 4 M MgC12 and 1 M CaC12. They tested also 4-hexanol, 2-ethylhexanol and methyl isobutyl ketone, among m a n y other solvents, and showed t h a t these perform similarly to isoamyl alcohol. From other relevant studies [10--14] it is concluded that magnesium chloride will coextract with lithium chloride, but that aluminum chloride will hardly do so at all. A simultaneous solution of the following two equations will give the necessary information on the extraction: m L i m c l ~ L i C l = K L i c l m L i m C l ~ + LiCl MgHtCl / ±MgCI 2 =
Kmgc12mmgm~l~'3_+MgCl~
(1)
(2)
with rncl = rnLi + 2~7~Mg and mcl = 3mAl + 2mMg + mLi. The activity coefficients in the aqueous solutions refer to the mixed solution, but can be obtained from those in binary solution "/±°LiCb7°±MgCI~ and 7°±AlCh at the ionic strength I of the mixture, by the method of Lietzke and Stoughton [15] o o lnT±i = lnT~ + 0. 5 ~ iyi(zizi -IlnT±i -- lnT_+i )
(3)
where z is the charge and y the ionic strength fraction of the designated electrolyte. The extraction constants have been given as [15] KLtc~ = 4.9 × 10 -s and as [16] KMgch = 2 × 10 -s. The activity coefficients of the salts in the organic phase can be expressed in power series of inn from extraction data for binary solutions [16], assumed to apply also for mixtures. Organic solutions in equilibrium with the aqueous feed described above will have mLi = 0.35 and mMg = 0.07, i.e. a distribution ratio DLi = 0.74 and an enrichment factor relative to magnesium of ca. 2.7. Contact of this organic solution with an equal volume of water will strip both salts practically completely.
273 DETAILED DESCRIPTION OF PROCESS (see the flow sheet in Fig. 1)
Precipitation Aqueous aluminium chloride recycled from a later stage, plus some makeup to cover losses is mixed with Dead Sea brine and calcium hydroxide slurry keeping the pH constant between 6.8--7.0. The solid phase is separated by thickening and filtration giving a lithium concentrate containing 0.064% Li on a dry basis.
Washing The concentrate is washed with water in a three~tage countercurrent washing system to remove soluble salts, mainly magnesium and calcium chlorides. The residual wash water containing 27 p p m lithium may be concentrated by solar evaporation and returned to the precipitation stage. The final concentrate from the washing has the following composition: Al:O3 Li20 MgC12 CaC12 (K+Na)C1 H20
3.68% 0.18% 0.6% 0.1% 0.05% balance
1
(Molar ratio A1203:Li20
Ca(OH)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SOLAR
6:1)
=
LREJECTWASH ._WATER
EVAPORATION| . . . . . . . • . . . . . . WASTE TIDEPLETED BRINE 1 DEAD SEAl , I I , l - - ----~PRECIPITATION~--~ITHICKENING I---------~IFILTRATION ~ BRINE
I
I
I
I
l
I
•
I
3-STAGE
L ..........
[WASHIN . . .G. . . . . . . ANDI
AICI3 / MAKE Up = e
AICI 3 RECYCLE '
WATER
LI
/
:i FILTRATION /
F LTRAT ON H
.
I /
1
I T
LITHIUMI IELECTROLYS~S ~ METAL ' I
',[__1
"°' °'DISSOLUTIONi
Cl
[
EVAPORATIONL - - - ~ L - LIQUID- LIQUID'~I CONCENTRATIONI J . I SOLUTION E X T R A C T I O N J I
Fig. 1. F l o w sheet of lithium production.
' '
274
Dissolution and concentration The concentrate is dissolved in hydrochloric acid giving a brine with the following composition: Salt:
AIC13 M g C 1 2
C a C 1 2 (K+Na)C1
LiCI
g/kg
79
0.8
4.1
4.9
0.4
The brine is further concentrated up to the point of saturation. Solvent extraction The lithium and aluminium chlorides are separated from the concentrated brine by solvent extraction using one of the suitable solvents available such as n-hexanol, 2~ethylhexanol or methyl isobutyl ketone. The lithium-depleted aluminium chloride brine is recycled to the precipitation stage. Production o f lithium metal The aqueous solution of lithium chloride obtained in the solvent extraction stage may be used to make other commercially required lithium salts or dehydrated and electrolysed in a fused-salt bath to produce lithium metal. The production of lithium metal by electrolysis of the chloride in a bath of fused salts is a known process. ECONOMIC E V A L U A T I O N
The data available at this stage of development are not sufficient for a detailed economical evaluation. However, an approximate indication of cost should be available in order to form a basis for estimating the desirability of continuing to develop the process. The following evaluation is based on two hour~ residence time in the initial precipitation stage. Data are n o t available for a detailed cost estimate of the investment required in the solvent extraction and electrolysis stages, b u t it is quite obvious that owing to the much larger volumes involved in the precipitation and washing stages, the size of the equipment, and therefore the cost of it, for the latter stages would be relatively "very small. Therefore, only variable costs are considered for these parts. The production cost of $30/kg of lithium metal may be compared with the current selling price, which is also $30/kg. For a project at such an early stage of development, one would wish to arrive at a much lower figure in order to justify further development. On the other hand, the expectations of further depletion of lithium resources may, as indicated earlier, enhance the attractiveness of the process described above.
275
Lithium production - 50 tons/year of Li metal Investments 1. Precipitation stage 2. Washing, thickening and filtration + Running-in costs and interest during construction Variable and fixed costs Lime, 460 kg at $35 Hydrochloric acid, 576 kg at $30 Al chloride, 5% makeup at $200 Process water, 120 m3 h-’ at $0.1 1 m-’ Electricity for electrolysis of LiCl 18 kWh kg-’ Li at $0.04 kWh_’ Electricity for pumps and agitators Capital costs (23-25s) Operation and management Solvent extraction, $0.5 me3of aq. stream [17] Other expenses
$1,125,000 1,398,OOO Total 2,685,OOO $3,340,000 Annual costs $130,000 138,000 6,000 96,000 36,000 102,000 778,000 150,000 30,000 50,000 Total 1,516,OOO
Zest per kg of Li $30.00
iEFERENCES
1 Lithium Resources and Requirements in the Year 2000, Geological Survey Profession-
10 11 12 13 14 15 16 17
al Paper No. 1005, U.S. Govt. Printing Office, Washington, 1976. Smith, E.W., 2nd Industrial Minerals International Congress, Munich, 1976. Epstein, J.A., Hydrometahurgy, 2 (1976) l-10. Kaplan, D., Israel J. Chem., 1(1963) 115. Frenkel, M., Glasner, A. and Sarig, S., J. Phys. Chem., 84 (1980) 507-510. Forgacs, C. and Eiger, H., unpublished results. Datta, R.K. and Roy, R., J. Am. Ceram. Sot., 46(8) (1963) 388. Kuznetsova, E.M. and Panchenkov, G.M., Zh. Fiz. Khim., 40 (1966) 481. Marcus, Y., Ben-Zwi, N. and Blinderman, J.M., Israel J. Chem., 10 (proc.) (1972) 161; J.M. Blinderman, M.Sc. thesis, Hebrew Univ., Jerusalem, 1972. Rozen, A.M. and Mikhalichenko, A.I., Russ. J. Inorg. Chem., 12 (1967) 380. Azarova, L.A. and Vinogradov, E.E., Zh. Neorg. Khim., 21 (1976) 2484. Vinogradov, E.E., Zh. Neorg. Khim., 12 (1967) 1930. Krasnov, K.S. and Kazas, T.S., Radiokhimiya, 14 (1972) 246. Kazas, T.S. and Krasnov, K.S., Izv. Vyssh. Ucheb. Zav. Khim. i Khim. Teknol., 17 (1974) 209. Lietzke, M.H. and Stoughton, R.W., J. Soln. Chem., 1 (1972) 299. Marcus, Y., unpublished results, 1977. Barnea, E., private communication.