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Separation of lithium from dead sea brines by gel permeation chromatography
SHORT
SEPARATION BY GEL
OF LITHIUM PERMEATION
(Received
‘37
COMMUNICATIONS
FROM DEAD SEA BRINES CHROMATOGRAPHY
19 June 1972 Accepted
3 August
1972)
Dead Sea brutes are concentrated soluttons of a mtxture of salts (3040% salts, specific gravtty ca 1.3). mamly hahdes of the alkahne and alkalme earth metals To date. their prmcrpal value ts as a source of potash and bromine, but there IS also constderable interest m the extractton of the rarer elements dtssolved m them. such as caesmm. rubidium, and hthmm Of these three elements hthtum IS present m relattvely high concentratrons-20 ppm m the water of the Sea and about 40 ppm m the so-called “end brine”, which IS a concentrated salt solutton obtamed after evaporation of the water m solar ponds and the subsequent crystalhzation of the potash. Of all separatron techniques available for such a concentrated salt solution, gel permeation chromatography seemed to the authors the most promrsmg In that method use 1s made of the differential mrgration of cations, the difference bemg most pronounced between the mtgrations of univalent and brvalent metal ions, especially on polyacrylamide gels. Studtes of the gel permeation chromatography of simple cations and anions were first camed out by Egan,’ who used polydextran and polyacrylamtde gels Ohasht 2-4 has mvestigated solute-gel utteractions and the Influence of elutmg agents on the chromatograms obtamed. In these works a certam degree of selectrvity was achieved This study examines the possrbihty of utihwng such separations to obtain hthuim-ennched fractions. The mam problems to which an answer was sought by the authors were (1) whether it is possible to separate hthmm chlonde from the other chlorides m the very concentrated soluttons available; (2) the determutation of the purity of the hthmm so obtained m the concentrated fractions, (3) whether some degree of preconcentratron can be achieved m addrtron to the separation. EXPERIMENTAL
Matertals gel, Blo-Gel P-2, molecular wetght exclusion hmrt about 2600. Bio-Rad Laboratories,
Polyacrylamlde
Richmond,
California. Blue Dextran Separation
2000, average molecular
weight 2 x lo6 Pharmacta
Fme Chemicals, Sweden
procedure
Dry Bra-Gel P-2 was immersed m distilled water and allowed to swell for 24 hr. The gel thus wetted was introduced mto a 2OO-cm long column of 3.5 cm mternal diameter. The bed length was 147 cm. Before use the column was rinsed for several hours with distrlled water The void volume, Fe, determined by measunng the elution volume of Blue Dextran 2000, was found to be 400 ml The total volume V, was 1385 ml After mtroductton mto the column, at a flay-rate of 1 ml/min, the sample of Dead Sea water was allowed to soak completely mto the gel phase. For elutron, drstilled water was used. Ten-ml fractions were collected from the column, and each fraction was analysed for hthmm, sodium, potassium, calcium, and magnesium. Analytical
methods
Since the hthmm content of Dead Sea brines IS very low compared with that of the other salts, Its atomic-absorptron signal is ordmarily suppressed, but with the method of standard additions quantttatrve results can be achieved The measurements were made on a Perkm-Elmer Model 403 Atomic Absorptron Spectrophotometer wrth a hthtum hollow-cathode lamp at wavelength 335 nm. Potassium and sodrum These were measured by flame photometry, using the same instrument as for hthmm but at wavelength 589 nm for sodmm and 766 5 nm for potassium. Calcrunt and magneszum These were titrated m an ammonia buffer with a standard solutton of EDTA, wtth Ertochrome Black T as rndrcator Qualltatrce tests In order to follow the elution process, quahtatrve tests for chlonde were made throughout Thus the fraction m which the brme begins to emerge and the pomt at which rt IS completely eluted from the column can be estabhshed Ltthrum
238
SHORT CDMMUNICATlONS
Further quahtatlve tests, for magnesmm and calcmm, were carried out with carbonate m order to determme the fraction m which these elements first emerge from the column Fortunately. they do so after the IIthtum RESULTS
AND
DlSCUSSlON
The great dtfficulty encountered m this separatton stems from the very high overall salt concentration and from the high vtscosity and den&y of both Dead Sea Water and the end brme Table 1 lists the average salt composltlons of these solutions
Table 1. Salt composmon of Dead Sea water (D S W) and end brine (E.B)
LI+ cone. PPm
Salt concentration, g/l .-_I_____ CaCIz NaCf M&l,
Br- cone SiI
Sample
SP. gr at 17°C
D SW.
1.22
18
48
155
E.B.
1.337
36
Il.2
348
463 108
.- . KCI
1003
136
69
38
Both Dead Sea water and end brme were chromatographed on a column of Blo-Gel P-2, and the catmns were eluted with water. The chromatograms are shown m Ftgs. 1 and 2. In both cases the order of appearance m the effluent fractions was K”, Na+, LI+, Mg’*, &a”, thus confirmmg the iindmgs of Egan i The chromatograms &early mdicate that separation 1s feastble and that there are a number of fracttons which contam hzgh conce~~t~ons of hthtum chiortde. These fracttons also contam small amounts of NaCf and KCI, but no salts of either calcmm or magnesium. This IS slgmficant, as these latter two Ions are the ones that are present m the highest concentrations The fact that these two blvalent catIons emerge last from the column can be explamed by their stronger mteractlon with the negattveiy charged oxygen atom of the resonance form of the polyacryiarn~de gel
CH,-C
P\N/
H
A+ Indeed, the dlstnbutlon coefficrents-as shown m Table 2-are all smaller than umty, mdrcatmg that this mteractlon, though relatively weak, 1s yet stronger than with the umvalent cations. Table 2. Dzstnbutzon coefkents of Dead Sea brrnes on Bro-Gel P-2 Sample K’ Na’ LI’ ~I____..~-__-~ _--_-.DS.W 046 0 53 0 59 ___________-...-._ __ ---.__IIE.B. 0.37 046 0.49
Mg”+ 071 060
Ca’ + ------
087 075
Drstnbutton coefficxents (Kdvo,lJ& were calculated from the chromatogram Laurent and Klltander *
by the formula developed by
where Y, IS the eluted volume of the solute, V, the votd volume. and V, the total hqutd volume
SHORT
239
COMMUNICATlONS
L 04
07
06
05
VJVt
Vt*l385,
08
09
10
ml
Ftg 1 Fra~t~onatlon of Dead Sea water on Bra-Gel P-2 Magnesium and c&mm peaks have not been drawn m because of then great height, but then locations have been mdtcated
From a practical point of view It seems better to separate hthmm from the end brine, because there the concentmtlon of hthmm IS hrgher, and that of potassmm and sodmm lower, than m the natural L3ead Sea water Table 3 presents a comparatrve study of both solutrons as regards the degree of separatron and preconcentratton achreved wrth them The results shown m Table 3 mdtcate that the arms set m the mtroductron were achreved to a certain extent Of the 130 lo-ml fractrons collected there are four or five that are rich m hthmm and contam only small quantmes of potassmm and sodrum but no magnesmm or calcmm. A degree of preconcentratron was also achieved It seems preferable, as was stated before, to separate hthmm from the end brme, because of tts hrgher mrttal concentratron and the presence of lower quarttrues of sodtum potassium. On the other hand the vrscosity of the end brme IS higher than that of natural Dead Sea water and Its mrgratron through the column consequently slower
V,/Vt
Vtz1395,
ml
Fig 2 Fracttonatton of end brine on Bto-Gel P-2 Magnesmm and calcmm peaks have not been drawn m because of then great hetght. but then locatrons have been mdtcated
240
SHORT COMMUNICATIONS
Table 3 Composttton
Imtlal LI+ cont. Lt+ cont. m enrlched
of the hthmm-enrtched and end brme
fractions
Lt+/Na’ Lt+/Na’
m orlgmal solution m concentrated fractton
Lt+/K+ Ll+/K+
m ortgmal solution m concentrated fractions
Lt+/Mg’+ Lt+/Mg’+
m orlgmal solution m concentrated fractions
m ongmal solutton Li+/Ca’+ Llf/Ca2 + m concentrated fractions
Acknowledgement-This No 1214
project
was supported
fracttons
of Dead
Sea water
D.S W
EB
18 ppm 49 ppm
38 ppm 62 ppm
1 5550 1 11
1 181 1 8
1 756 1 10
1 loo 1 3
1.8611 1 1
1 9150 no magnesmm present
I 2572 1:l
m part by the Israel
Department of Chemutry Techmon-lsrael Institute of Technology Halfa, Israel
1 2840 no calcmm present
Mmlstry
of Development
under
Contract
M RONA G SCHMUCKLER
REFERENCES 1. 2. 3. 4 5
B. Y N. T T
Z. Egan. J Chromatog, 1968, 34, 382. Ueno, N. Yoza and S Ohasht, ibrd.. 1970, 52, 321 Yoza, T. Ogato and S. Ohashl, IbId, 1970, 52, 329. Ogato, N Yoza and S. Ohashi, rbld., 1971, 58, 267. C. Laurent and J Kdlander, Ibtd.. 1964.34, 317
Summary-Fracttonatton of Dead Sea brmes by dlfferentlal rmgratlon through a polyacrylamlde gel IS shown to be feasible. Ltthtum-enrIched fractions obtamed m the process contam no calcmm or magnesmm and only small quantltles of sodtum and potassmm Zusammenfassung-Es wlrd gezelgt, daD Solen aus dem Toten Meer durch dtfferentlelle Wanderung durch em Polyacrylamldgel frakttomert werden konnen Durch dleses berfahren erhaltene, an Llthmm angereicherte Fraktlonen enthalten kem Calcmm oder Magnesmm und nur wemg Natrmm und Kahum R&me-II a ete montrk que le fractlonnement de saumures de la Mer Morte par mlgrauon dlff&enttelle d travers un gel de polyacrylamtde est possible Les fractions enrtchles en hthmm obtenues dans le processus ne contlennent pas de calcium ou de magntslum et seulement de petnes quantltis de sodium et potassmm.
SEPARATION BY GEL
OF LITHIUM PERMEATION
(Received
‘37
COMMUNICATIONS
FROM DEAD SEA BRINES CHROMATOGRAPHY
19 June 1972 Accepted
3 August
1972)
Dead Sea brutes are concentrated soluttons of a mtxture of salts (3040% salts, specific gravtty ca 1.3). mamly hahdes of the alkahne and alkalme earth metals To date. their prmcrpal value ts as a source of potash and bromine, but there IS also constderable interest m the extractton of the rarer elements dtssolved m them. such as caesmm. rubidium, and hthmm Of these three elements hthtum IS present m relattvely high concentratrons-20 ppm m the water of the Sea and about 40 ppm m the so-called “end brine”, which IS a concentrated salt solutton obtamed after evaporation of the water m solar ponds and the subsequent crystalhzation of the potash. Of all separatron techniques available for such a concentrated salt solution, gel permeation chromatography seemed to the authors the most promrsmg In that method use 1s made of the differential mrgration of cations, the difference bemg most pronounced between the mtgrations of univalent and brvalent metal ions, especially on polyacrylamide gels. Studtes of the gel permeation chromatography of simple cations and anions were first camed out by Egan,’ who used polydextran and polyacrylamtde gels Ohasht 2-4 has mvestigated solute-gel utteractions and the Influence of elutmg agents on the chromatograms obtamed. In these works a certam degree of selectrvity was achieved This study examines the possrbihty of utihwng such separations to obtain hthuim-ennched fractions. The mam problems to which an answer was sought by the authors were (1) whether it is possible to separate hthmm chlonde from the other chlorides m the very concentrated soluttons available; (2) the determutation of the purity of the hthmm so obtained m the concentrated fractions, (3) whether some degree of preconcentratron can be achieved m addrtron to the separation. EXPERIMENTAL
Matertals gel, Blo-Gel P-2, molecular wetght exclusion hmrt about 2600. Bio-Rad Laboratories,
Polyacrylamlde
Richmond,
California. Blue Dextran Separation
2000, average molecular
weight 2 x lo6 Pharmacta
Fme Chemicals, Sweden
procedure
Dry Bra-Gel P-2 was immersed m distilled water and allowed to swell for 24 hr. The gel thus wetted was introduced mto a 2OO-cm long column of 3.5 cm mternal diameter. The bed length was 147 cm. Before use the column was rinsed for several hours with distrlled water The void volume, Fe, determined by measunng the elution volume of Blue Dextran 2000, was found to be 400 ml The total volume V, was 1385 ml After mtroductton mto the column, at a flay-rate of 1 ml/min, the sample of Dead Sea water was allowed to soak completely mto the gel phase. For elutron, drstilled water was used. Ten-ml fractions were collected from the column, and each fraction was analysed for hthmm, sodium, potassium, calcium, and magnesium. Analytical
methods
Since the hthmm content of Dead Sea brines IS very low compared with that of the other salts, Its atomic-absorptron signal is ordmarily suppressed, but with the method of standard additions quantttatrve results can be achieved The measurements were made on a Perkm-Elmer Model 403 Atomic Absorptron Spectrophotometer wrth a hthtum hollow-cathode lamp at wavelength 335 nm. Potassium and sodrum These were measured by flame photometry, using the same instrument as for hthmm but at wavelength 589 nm for sodmm and 766 5 nm for potassium. Calcrunt and magneszum These were titrated m an ammonia buffer with a standard solutton of EDTA, wtth Ertochrome Black T as rndrcator Qualltatrce tests In order to follow the elution process, quahtatrve tests for chlonde were made throughout Thus the fraction m which the brme begins to emerge and the pomt at which rt IS completely eluted from the column can be estabhshed Ltthrum
238
SHORT CDMMUNICATlONS
Further quahtatlve tests, for magnesmm and calcmm, were carried out with carbonate m order to determme the fraction m which these elements first emerge from the column Fortunately. they do so after the IIthtum RESULTS
AND
DlSCUSSlON
The great dtfficulty encountered m this separatton stems from the very high overall salt concentration and from the high vtscosity and den&y of both Dead Sea Water and the end brme Table 1 lists the average salt composltlons of these solutions
Table 1. Salt composmon of Dead Sea water (D S W) and end brine (E.B)
LI+ cone. PPm
Salt concentration, g/l .-_I_____ CaCIz NaCf M&l,
Br- cone SiI
Sample
SP. gr at 17°C
D SW.
1.22
18
48
155
E.B.
1.337
36
Il.2
348
463 108
.- . KCI
1003
136
69
38
Both Dead Sea water and end brme were chromatographed on a column of Blo-Gel P-2, and the catmns were eluted with water. The chromatograms are shown m Ftgs. 1 and 2. In both cases the order of appearance m the effluent fractions was K”, Na+, LI+, Mg’*, &a”, thus confirmmg the iindmgs of Egan i The chromatograms &early mdicate that separation 1s feastble and that there are a number of fracttons which contam hzgh conce~~t~ons of hthtum chiortde. These fracttons also contam small amounts of NaCf and KCI, but no salts of either calcmm or magnesium. This IS slgmficant, as these latter two Ions are the ones that are present m the highest concentrations The fact that these two blvalent catIons emerge last from the column can be explamed by their stronger mteractlon with the negattveiy charged oxygen atom of the resonance form of the polyacryiarn~de gel
CH,-C
P\N/
H
A+ Indeed, the dlstnbutlon coefficrents-as shown m Table 2-are all smaller than umty, mdrcatmg that this mteractlon, though relatively weak, 1s yet stronger than with the umvalent cations. Table 2. Dzstnbutzon coefkents of Dead Sea brrnes on Bro-Gel P-2 Sample K’ Na’ LI’ ~I____..~-__-~ _--_-.DS.W 046 0 53 0 59 ___________-...-._ __ ---.__IIE.B. 0.37 046 0.49
Mg”+ 071 060
Ca’ + ------
087 075
Drstnbutton coefficxents (Kdvo,lJ& were calculated from the chromatogram Laurent and Klltander *
by the formula developed by
where Y, IS the eluted volume of the solute, V, the votd volume. and V, the total hqutd volume
SHORT
239
COMMUNICATlONS
L 04
07
06
05
VJVt
Vt*l385,
08
09
10
ml
Ftg 1 Fra~t~onatlon of Dead Sea water on Bra-Gel P-2 Magnesium and c&mm peaks have not been drawn m because of then great height, but then locations have been mdtcated
From a practical point of view It seems better to separate hthmm from the end brine, because there the concentmtlon of hthmm IS hrgher, and that of potassmm and sodmm lower, than m the natural L3ead Sea water Table 3 presents a comparatrve study of both solutrons as regards the degree of separatron and preconcentratton achreved wrth them The results shown m Table 3 mdtcate that the arms set m the mtroductron were achreved to a certain extent Of the 130 lo-ml fractrons collected there are four or five that are rich m hthmm and contam only small quantmes of potassmm and sodrum but no magnesmm or calcmm. A degree of preconcentratron was also achieved It seems preferable, as was stated before, to separate hthmm from the end brme, because of tts hrgher mrttal concentratron and the presence of lower quarttrues of sodtum potassium. On the other hand the vrscosity of the end brme IS higher than that of natural Dead Sea water and Its mrgratron through the column consequently slower
V,/Vt
Vtz1395,
ml
Fig 2 Fracttonatton of end brine on Bto-Gel P-2 Magnesmm and calcmm peaks have not been drawn m because of then great hetght. but then locatrons have been mdtcated
240
SHORT COMMUNICATIONS
Table 3 Composttton
Imtlal LI+ cont. Lt+ cont. m enrlched
of the hthmm-enrtched and end brme
fractions
Lt+/Na’ Lt+/Na’
m orlgmal solution m concentrated fractton
Lt+/K+ Ll+/K+
m ortgmal solution m concentrated fractions
Lt+/Mg’+ Lt+/Mg’+
m orlgmal solution m concentrated fractions
m ongmal solutton Li+/Ca’+ Llf/Ca2 + m concentrated fractions
Acknowledgement-This No 1214
project
was supported
fracttons
of Dead
Sea water
D.S W
EB
18 ppm 49 ppm
38 ppm 62 ppm
1 5550 1 11
1 181 1 8
1 756 1 10
1 loo 1 3
1.8611 1 1
1 9150 no magnesmm present
I 2572 1:l
m part by the Israel
Department of Chemutry Techmon-lsrael Institute of Technology Halfa, Israel
1 2840 no calcmm present
Mmlstry
of Development
under
Contract
M RONA G SCHMUCKLER
REFERENCES 1. 2. 3. 4 5
B. Y N. T T
Z. Egan. J Chromatog, 1968, 34, 382. Ueno, N. Yoza and S Ohasht, ibrd.. 1970, 52, 321 Yoza, T. Ogato and S. Ohashl, IbId, 1970, 52, 329. Ogato, N Yoza and S. Ohashi, rbld., 1971, 58, 267. C. Laurent and J Kdlander, Ibtd.. 1964.34, 317
Summary-Fracttonatton of Dead Sea brmes by dlfferentlal rmgratlon through a polyacrylamlde gel IS shown to be feasible. Ltthtum-enrIched fractions obtamed m the process contam no calcmm or magnesmm and only small quantltles of sodtum and potassmm Zusammenfassung-Es wlrd gezelgt, daD Solen aus dem Toten Meer durch dtfferentlelle Wanderung durch em Polyacrylamldgel frakttomert werden konnen Durch dleses berfahren erhaltene, an Llthmm angereicherte Fraktlonen enthalten kem Calcmm oder Magnesmm und nur wemg Natrmm und Kahum R&me-II a ete montrk que le fractlonnement de saumures de la Mer Morte par mlgrauon dlff&enttelle d travers un gel de polyacrylamtde est possible Les fractions enrtchles en hthmm obtenues dans le processus ne contlennent pas de calcium ou de magntslum et seulement de petnes quantltis de sodium et potassmm.