CA1272982A - Method for the recovery of lithium from solutions by electrodialysis - Google Patents
Method for the recovery of lithium from solutions by electrodialysisInfo
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- CA1272982A CA1272982A CA000495301A CA495301A CA1272982A CA 1272982 A CA1272982 A CA 1272982A CA 000495301 A CA000495301 A CA 000495301A CA 495301 A CA495301 A CA 495301A CA 1272982 A CA1272982 A CA 1272982A
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- concentrate
- lithium
- electrodialysis
- cells
- diluate
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Separation Using Semi-Permeable Membranes (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
ABSTRACT
Lithium-containing brines containing mono and multivalent cations, especially magnesium, and anions are treated by electrodialysis to effect separation of a lithium concentrate low in multivalent cations from which lithium can be recovered as chloride, sulfate, or carbonate. Brine containing 0.03 to 15 g/L Li and a ratio of Mg:Li as high as 60:1 is subjected to one or more electrodialysis steps. The preferred cationic and anionic membranes are those that are strongly acidic and have sulphonic acid radical and trimethylamine derivatives, respectively, as active groups at 3 to 4 milligram equivalent per gram of dry resin and have a matrix of styrene divinyl benzene copolymer on a pvc base. Electrodialysis is carried out at a pH below 7 under turbulent conditions. The number of electrodialysis steps depends on the permselectivity of the membrances, the Mg:Li ratio in the feed and that in the concentrate, the latter being maintained at 5:1 or less. The chloride concentration in the electrode compoartments is maintained at less that 3 g/L. In multi-step electrodialysis, a portion of the magnesium may be removed in an intermediate stage by the addition of lime, the lithium in the resulting solution being further concentrated by electrodialysis.
Electrodialysis is carried out in at least one unit comprising a multiplicity of alternating anion permselective membranes and univalent cation permselective membranes defining alternating diluate and concentrate cells between an anode and a cathode compartment. Lithium is recovered from withdrawn concentrate.
Lithium-containing brines containing mono and multivalent cations, especially magnesium, and anions are treated by electrodialysis to effect separation of a lithium concentrate low in multivalent cations from which lithium can be recovered as chloride, sulfate, or carbonate. Brine containing 0.03 to 15 g/L Li and a ratio of Mg:Li as high as 60:1 is subjected to one or more electrodialysis steps. The preferred cationic and anionic membranes are those that are strongly acidic and have sulphonic acid radical and trimethylamine derivatives, respectively, as active groups at 3 to 4 milligram equivalent per gram of dry resin and have a matrix of styrene divinyl benzene copolymer on a pvc base. Electrodialysis is carried out at a pH below 7 under turbulent conditions. The number of electrodialysis steps depends on the permselectivity of the membrances, the Mg:Li ratio in the feed and that in the concentrate, the latter being maintained at 5:1 or less. The chloride concentration in the electrode compoartments is maintained at less that 3 g/L. In multi-step electrodialysis, a portion of the magnesium may be removed in an intermediate stage by the addition of lime, the lithium in the resulting solution being further concentrated by electrodialysis.
Electrodialysis is carried out in at least one unit comprising a multiplicity of alternating anion permselective membranes and univalent cation permselective membranes defining alternating diluate and concentrate cells between an anode and a cathode compartment. Lithium is recovered from withdrawn concentrate.
Description
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Q~ INV~NTI~
This invention relates to a method for the recovery of lithium from so1utions and, more particularly, to a method for the recovery of lithium from lithium containing brines and solutions 5 using electrodialysis.
In the recovery of lithium from ores, ore may be baked with sulfuric acid, the product leached with water, resulting lithium sulfate solution treated with lime and soda ash to remove calcium and magnesium, and lithium precipitated as carbonate. Other ore-treating methods include the o-called alkaline methods and ion-exchange methods which yield solutions of lithium as hydroxide, chloride or sulfate. These methods also include the removal of ; calcium and magnesium by treatment with lime and soda ash.
In the recovery of lithium from natural, predominantly chloride, 15 brines, which vary widely in composition, an economical recovery ; depends not only on the lithium content but also on the concentrations of in~erfering ions, especially calcium and magnesium. Magnesium is particularly troublesome because its chemical behaviour in solution is very similar to that of ~; 20 lithium. If the magnesium content is low, removal by precipitation with lime is feasible. Evaporation and treatment with lime and oda ash, is followed by precipitation of lithium carbonate. In the case of a high magnesium content, removal with lime is not feasible and various ion exchange and liquid-liquid ex~raction methods have been proposed. Thus, it i~ obvious that, although conventional processing of ores and brines makes it ., '" ~
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~%~2g~2 possible to eliminate major portions of interfering ions, the separation of lithium from magnesium remain5 a serious problem.
Lithium brines have also been subjected to electrolysis or to membrane electrolysis, but usually only after the calcium and S magnesium contents have been reduced to relatively low values.
Therefore, el~ctrolysis and membrane eleetrolysis of lithium salt solutions, usually with the object of producing a lithium compound, not only require the additional step of removing calcium and magnesium, but have the additional disadvantage of the evolution of copious amounts of gases such as hydrogen and chlorine.
It is suggested that the use of electrodialysis alone or in combination with cation exchange may overcome these difficulties to some extent and can accomplish a separation of lithium from 15 multivalent cations such as iron, aluminum, calcium and magnesium. More specifically, in ~.S. Patent 3063924, it is stated that the removal of univalent ions and multivalent anions from aqueous solutions is easily accomplished, but the presence of multivalent cation~ such as calcium and magnesium causes di~ficulties due to the formation of deposits on membranes.
Hence, multivalent cations are first removed by means of a cation exchanger whereupon calcium and magnesium deposit after which the : liquid is passed throu~h an electrodialyzing apparatus to remove ~a portion of at least one monovalent ion and to form a 25 concentrated salt solution. This method still requires the prior ,' " .
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removal of calcium and magne6ium in a separate operation.
G.E. Raplan et al have reported (Chemical Abstracts, volume 60, 6507a) that good separation~ of lithium ions from multivalent ions, such as ferric, aluminum, magnesium and calcium ions, can be obtained at ~igh pH in a three-compartment electrodialysis cell using unipolar and bipolar ion-exchange membranes, a nickel anode and a lead-antimony alloy cathode. The presented data show that only relatively dilute solutions have been u edl It is stated that at hi~h pH hydroxides of the multivalent cation~
lo precipitate, and that at low pH the selectivity toward these cations is considerably lowered.
~UMMARY QE ~E~ INvENTIoN
We have now found that lithium in solutions can be concentrated to a high concentration and that a very effective separation of lithium from brines comprising lithium and high concentrations of multivalent ions, especially magnesium, can be obtained with high selectivity by subjecting such solutions and brines to electrodialy is at low or neutral p~ using monopolar cationic and anionic permselective membranes.
The cationic membranes that are useful are those that are permselective for monovalent cations, and the anionic membranes ~: are chosen dependent on the form in which lithium is to be ; recovered from the concentrate and can be permselective for ~-. monovalent or mono and multivalent anions. By carefully - 25 controlling the operating conditions, such as current densities, ac1d~ties and flow rate~ a concentrated ~olution of lithium with , .. . . .
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a low magne~ium to lithium weight ratio can be recovered. Feed ~olution~ containing as little a~ 30 mg lithium per litre of brine or solution and a magnesium to lithium weight ratio as high as ~ixty to one can be processed.
When treating chloride-containin~ lithium brine~, the evolution of chlorine can be ~uppressed by the choice of an appropriate rinse ~olution.
A hiyh recovery of lithium and a satisfactory rejection of multivalent cations~ especially magnesium, can be achieved by carrying out ~he method in a single stage. With feed brines with high ratios of magnesium to lithium, it ~ay be necessary to carry out the method in more than one stage. In one embodiment, the lithium content in the concentrate is raised partially in a first stage while lowering the magnesium content. Subsequently, a major portion of the magnesium in the concentrate is removed with lime. The remaining solution is 5ubjected to a second stage electrodialysis to concentrate the lithium content further.
Accordingly, there is provided a method for the recovery of : litbium from brines containing monovalent cations including ; 20 lithium, multivalent cations including magnesium and monovalen~
and multivalent anions which method comprises the steps of subjecting brine to electrodialysis; feeding brine to diluate cells of an electrodialysis unit comprising a multiplicity of :
alternating monopolar cationic permselective membranes and monopolar anionic permselectiYe membranes, said membranes - ,.
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Q~ INV~NTI~
This invention relates to a method for the recovery of lithium from so1utions and, more particularly, to a method for the recovery of lithium from lithium containing brines and solutions 5 using electrodialysis.
In the recovery of lithium from ores, ore may be baked with sulfuric acid, the product leached with water, resulting lithium sulfate solution treated with lime and soda ash to remove calcium and magnesium, and lithium precipitated as carbonate. Other ore-treating methods include the o-called alkaline methods and ion-exchange methods which yield solutions of lithium as hydroxide, chloride or sulfate. These methods also include the removal of ; calcium and magnesium by treatment with lime and soda ash.
In the recovery of lithium from natural, predominantly chloride, 15 brines, which vary widely in composition, an economical recovery ; depends not only on the lithium content but also on the concentrations of in~erfering ions, especially calcium and magnesium. Magnesium is particularly troublesome because its chemical behaviour in solution is very similar to that of ~; 20 lithium. If the magnesium content is low, removal by precipitation with lime is feasible. Evaporation and treatment with lime and oda ash, is followed by precipitation of lithium carbonate. In the case of a high magnesium content, removal with lime is not feasible and various ion exchange and liquid-liquid ex~raction methods have been proposed. Thus, it i~ obvious that, although conventional processing of ores and brines makes it ., '" ~
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~%~2g~2 possible to eliminate major portions of interfering ions, the separation of lithium from magnesium remain5 a serious problem.
Lithium brines have also been subjected to electrolysis or to membrane electrolysis, but usually only after the calcium and S magnesium contents have been reduced to relatively low values.
Therefore, el~ctrolysis and membrane eleetrolysis of lithium salt solutions, usually with the object of producing a lithium compound, not only require the additional step of removing calcium and magnesium, but have the additional disadvantage of the evolution of copious amounts of gases such as hydrogen and chlorine.
It is suggested that the use of electrodialysis alone or in combination with cation exchange may overcome these difficulties to some extent and can accomplish a separation of lithium from 15 multivalent cations such as iron, aluminum, calcium and magnesium. More specifically, in ~.S. Patent 3063924, it is stated that the removal of univalent ions and multivalent anions from aqueous solutions is easily accomplished, but the presence of multivalent cation~ such as calcium and magnesium causes di~ficulties due to the formation of deposits on membranes.
Hence, multivalent cations are first removed by means of a cation exchanger whereupon calcium and magnesium deposit after which the : liquid is passed throu~h an electrodialyzing apparatus to remove ~a portion of at least one monovalent ion and to form a 25 concentrated salt solution. This method still requires the prior ,' " .
~729~3~
removal of calcium and magne6ium in a separate operation.
G.E. Raplan et al have reported (Chemical Abstracts, volume 60, 6507a) that good separation~ of lithium ions from multivalent ions, such as ferric, aluminum, magnesium and calcium ions, can be obtained at ~igh pH in a three-compartment electrodialysis cell using unipolar and bipolar ion-exchange membranes, a nickel anode and a lead-antimony alloy cathode. The presented data show that only relatively dilute solutions have been u edl It is stated that at hi~h pH hydroxides of the multivalent cation~
lo precipitate, and that at low pH the selectivity toward these cations is considerably lowered.
~UMMARY QE ~E~ INvENTIoN
We have now found that lithium in solutions can be concentrated to a high concentration and that a very effective separation of lithium from brines comprising lithium and high concentrations of multivalent ions, especially magnesium, can be obtained with high selectivity by subjecting such solutions and brines to electrodialy is at low or neutral p~ using monopolar cationic and anionic permselective membranes.
The cationic membranes that are useful are those that are permselective for monovalent cations, and the anionic membranes ~: are chosen dependent on the form in which lithium is to be ; recovered from the concentrate and can be permselective for ~-. monovalent or mono and multivalent anions. By carefully - 25 controlling the operating conditions, such as current densities, ac1d~ties and flow rate~ a concentrated ~olution of lithium with , .. . . .
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a low magne~ium to lithium weight ratio can be recovered. Feed ~olution~ containing as little a~ 30 mg lithium per litre of brine or solution and a magnesium to lithium weight ratio as high as ~ixty to one can be processed.
When treating chloride-containin~ lithium brine~, the evolution of chlorine can be ~uppressed by the choice of an appropriate rinse ~olution.
A hiyh recovery of lithium and a satisfactory rejection of multivalent cations~ especially magnesium, can be achieved by carrying out ~he method in a single stage. With feed brines with high ratios of magnesium to lithium, it ~ay be necessary to carry out the method in more than one stage. In one embodiment, the lithium content in the concentrate is raised partially in a first stage while lowering the magnesium content. Subsequently, a major portion of the magnesium in the concentrate is removed with lime. The remaining solution is 5ubjected to a second stage electrodialysis to concentrate the lithium content further.
Accordingly, there is provided a method for the recovery of : litbium from brines containing monovalent cations including ; 20 lithium, multivalent cations including magnesium and monovalen~
and multivalent anions which method comprises the steps of subjecting brine to electrodialysis; feeding brine to diluate cells of an electrodialysis unit comprising a multiplicity of :
alternating monopolar cationic permselective membranes and monopolar anionic permselectiYe membranes, said membranes - ,.
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2~32 defining alternating diluate and concentrate cells, an anode compartment and a cathode compartment, an anode positioned in the anode compartment and a cathode positioned in the cathode compartment; applying an electrical cur-ent between the anode and the cathode at a value such that the value or the corresponding current density is in the range of about 10 to 500 A/m2;
maintaining the temperature in the electrodialysis in the range of about 0 to 60C; maintaining the pH of the brine fed to the unit at a value of less than about 7; passirlg flows of solutions through the diluate and concentrate cells at a linear velocity sufficient to maintain turbulent flow in said cells; removing a lithium-depleted diluate from the diluate cells; withdrawing a lithium-enriched concentrate from the concentrate cells, said concentrate containing magnesium and lithium in a weight ratio of about 5:1 or less; and recovering lithium from withdrawn concentrate.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Brines that can be treated according to the method of the .
invention are natural brines such as occurring at Searle's Lake, :; the Great Salt Lake and Clayton'Valley in the United States and : 20 at various locations in Argentina, Bolivia and Chile. Other ~ brines that can be treated are oilfield brines, geothermal brines :' ~
; ~and intermediate solutions and brines obtained in the processing o~ ores and natural brines. Such brines contain varying amounts ~: : of monovalent cations includlng lithium, multivalent cations ~ ~25 including calcium, magnesium, iron, copper and zinc and anions including sulfate, borate and chloride.
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Although the method of the invention i8 ~uitable ~or the recovery of lithium from above-mentioned solution~ and brines1 the me~hod is e~pecially u~eful in the treatment of brines which contain high ratios of m~gnesium to lithium as well a~ r tho~e that S eon~ain very low concentrations of lithium. Su~h lithium-high magnesium ~rine~ are usually first treated by evaporation in conventional evaporator~ or in solar ponds, whereby sub~tantial amounts of ~alt~ other th~n the lithium and magnesium ~alts have :
:~ been precipi ated and re~oved from the brine. Low-llthium 10~ bcines, such aB oilfield or geothermal brines, can also be :
~: : treated advantageously by the method of the present invention.
:Thus, the lithi~um brines ~uitable a~ feed for the treatment by the method:of the present invention are brines containing lithium in a concentration as low as 30 mg/L. A practical upper limit 15~ for the ~lithium concentration in a feed brine i~ about 15 g/L, :: which is~ he practically attainable concentration for most brines n so:lar evaporation. Typicall~, feed brines contain about û.5 to;7 g/L lithium. Brines containing high concentrations of mono:valent cations other than llthium may be first. at ~east ~:;20 pa~tially, evaporated to reduoe the concentrations of the : monovalent cation~ other than lithium. During such partial evaporation, major portions of sodium and po~assium salts precipitate and can be removed.
: The lithium br~ne, whether or nct partially evaporated, is fed to an electrodialysi~ unit. The electrodialysis unit or ~ ~, .. ..
~;272~382 electrodialyzer comprise~ a multiplicity of vertically arranged, alternating anion permselective exchange membrane~ and univalent cation permÆelective 2xchanse membranes, a ca~hode compartment and an anode compartment. The choice of membranes i5 very 5 important. Suitable cationic membranes must have a high permselectivity (to be defined) for lithium, a low permselectivity for multivalent cations, especially magnesium, a high resi~tance against chemical deterioration, biological fouling and thermal degradation, a low electrical resistance and lO a high mechanical strength. We have found that ~uitable ca~ionic permselective membranes are, for example, strongly acidic membranes which have a membrane matrix of a styrene di-vinyl benzene co-polymer on a polyvinyl chloride base and possess sulphonic acid radicals ~R-SO3~) as active groups~ The active 15 groups comprise 3-4 milli-equivalents per gram of dry resin which is satisfactory to provide the desired selectivity for univalent ions. In particular, we have found that suitable cationic permselective membraneæ are treated Selemion ~M CMR, Selemion TM
Experimental A (specially treated on one face) and Selemion TM
20 Experimental B (both surfaces specially treated). Suitable anionic permselective membranes must have properties similar to those for the cati~nic membranes. Suitable anionic permselective membranes are, for example, strongly basic membranes with active ~roups derived from trimethylamine (for example, R-N(cH~)3.Cl) 2s at 3-4 milli-equivalents per gram of dry resin, and having a matrix of a styrene di-vinyl benzene co-polymer on a polyvinyl ~. ~
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chloride base. In particular, Selemion TM ASV, which is permselective for univalen-t anions, or Selemion TM AMV which is non-selective for univalent anions (i.e. permeable to mono and multivalent anions) are suitable, the choice being dependent on 5 the particular embodment of the method (to be described). A
combination of the preferred membranes will, therefore, make it possible to concentrate the monovalent cations, such as Li, Na and K, and monovalent anions such ~s Cl or mono and multivalent anions such as Cl, S04, and borates. The Selemion TM membranes, lO which are manufactured by the Asahi Glass Company of Tokyo, Japan, have the desired properties. It is understood that membranes with similar properties produced by other manufactures such as Neosepta TM CM-l and Neosepta TM CMS membranes that have sulphonic acid active groups and are produced by the Tokuyama Soda Co. Ltd.
15 of Japan, are similarly suitable and that the use of combinations of other membranes may yield the desired results.
The alternating cationic and anionic membranes form alternating diluate cells and concentrate cells situated between the anode compartment and the cathode compartment. The anode and cathode 20 are made of suitable materials. For example, the anode can be made of platinum coated titanium and the cathode of stainless steel. A source of direct current is connected to the electrodes.
The lithium brine is fed to the diluate cells, preferably after removal of suspended solids. A lithium-depleted diluate is 2S withdrawn from the diluate cells. It is important to maintain turbulent conditions in the concentrate and diluate cells. This .
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can be achieved by passing solution through the cells at a sufficient rate. At least a portion of the diluate may be recycled and fed into the diluate cells mainly to en~ure turbulent conditions. A lithium-enriched concentrate i~ withdrawn 5 from the concentrate cells as product~ If desired, at leas~ a portion of the withdrawn concentrate may be circulated as feed to ~he concentrate cells to ensure turbulent conditions. Instead of concentrate, a quantity of a dilute receiving solution of an acidic substance may be fed to the concentrate cells, mainly for reason of pH controln If desired, a quantity of acidic substance solution may be fed to the concentrate cells alone or together with and in addition to a circulated portion of the lithium concentrate. Whether the feeding of a solution of an acidic substance is necessary depends on the net water transfer in the electrodialyzer.
During electrodialysls, water i~ transferred by osmosis from the diluate to the concentrâte ~ides of the membranes and by electro osmosis, which takes place in the direction of the transferring ions. Feed brines with a high salt concentration (e~g. molar concentration of about 20) have a high osmotic pressure and thus a high rate of osmotic transfer can be expected. For such feeds, the water transfer caused by osmosis is in the opposite direction to that caused by electro-osmosis and, thus, tends to reduce the net ; water transfer. For dilute feed brines, both osmosis and electro-osmosis are in the same direction to augment the net water transfer which can be as high as 20 g mol/h or higher.
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With relatively concentrated feed brines it may be necessary to feed a make-up solution of an acidic substance or sodium sulfate to the concentrate cells, while for relatively dilute brinss the feeding of an acidic make-up solution to the concentrate cells may be unnecessary. Generally, the feeding of an acidic make-up solution is necessary when the net-water transfer rate to ~he conc~ntrate cells is less than the withdrawal rate of concentrate from the concentrate cells.
The nature of the acidic substance in the make-up solution depends on the form in which the lithium is to be recovered from the concentrate. If recovery as lithium chloride is desired, the acidic substance is a hydrochloric acid. If recovery as lithium carbonate is desired, the solution may contain sodium sulfate, sodium bisulfate or sulfuric acid, the use of sulfuric acid being preferred.
The cathode and anode compartments are rinsed with a circulating rinse solution. It was discovered that the anodic reaction yields mostly oxygen when the chloride ion concentration in the circulating anode rinse solution is kept at less than about 3 g/L. The rinse solution is preferably acidified to increase the electrical conductivity. The rinse solution can be water or a salt solution acidified to a pH of about 2. A pH of about 2 also prevents the formation of basic precipitates. The use of sodium sulfate solution with a concentration in the range of 0.1 to 1.0 molar, preferably 0.2 to 0.5 molar sodium sulfate, acidified with , ~7~
sulfuric acid to a pH of about 2, is preferred. Thi~ rin~e solution also cau~es evolution of oxygen~ thereby minimizing the evolution of chlorine~ which, unle~s recovered, con~titutes an undesirable byproduct. The same rin~e solution is circulated to 5 both the anode compartment and the cathode compartment.
When using monovalent cation permselective and anion permselective membranes, the monovalent cations and anions in the feed solution pass from the diluate cells to the concentrate cells through the cationic and anionic membranes respectively, 10 leaving multivalent cations and anions in the diluate cells. The use of monovalent permselective cationic and anionic membranes is : desired when lithium is to be recovered from concentrate as lithium chloride. When llthium is to be recovered as lithium sulfate, the use of monovalent cation permselective membranes and 15 multiYalent anion permselective membranes is preferred~ The gases evolved at the electrodes are carried from the cathode and anode compartments in the rinse solution. Unlike membrane electrolysis, the volume of ga~es evolved in electrodialysis is small, especially also in relation to the volume of brine . 20 treated.
:~ The permselectivity PMl/M2 of a membrane is defined as the ratio between the specific transport rate of a first element Ml and that of a ~econd element M~ through the membrane; the specific transport rate being the quotient of the transfer rate of the 25 element over the concentration of that element. In the present method, to effect separation of lithium from magnesium into a ., ~ ..
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-. ., -. , lithium-enriched concentrate, PLi/Mg should be greater than one, and preferably much greater than one. Desirable values of PLi/Mg are related to the weight ratio of Mg:Li and the number of electro dialysis steps.
For brines containing both lithium and multivalent cations, especially magnesium, the conventional processing of such brines by lime addition to precipitate magnesium limits the Mg:Li weight ratio from about 0.5:1 to as high as about 7:1. The ratio is preferably limited to 5:1. Ratios of higher than about 7:1 can cause formation of unmanageable precipitates. The Mg:Li weight ratio in concentrates obtained as final product by electrodialysis and to be subjected to further treatment should, therefore, also be restricted to an upper value of about 5:1 or less to avoid difficulties in subsequent processing. However, by establishing the number of electrodialysis steps in relation to the PLi/Mg value, feed brines with much higher Mg:Li ratios can be processed. For example, a brine containing magnesium and lithium in a weight ratio of 20:1 can be treated by electrodialysis using membranes having values for PLi/Mg of > 4, 1.5, or 1.1 in 1, 4 and 15 steps of electrodialysis preferably arranged in series, respectively, to give a final concentrate product with a maximum Mg:Li weight ratio of about 5:1 or less. In multi-stsp electrodialysis to improve the Mg:Li ratio, the concentrate ~rom one step i5 used as feed in a subsequent step, the last electrodialysis giving a final concentrate having the preferred Mg:Li ratio of not ~reater than about 5:1.
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A~ stated above, the lithlum feed brine may contain a~ little as 30 mg/L l~thium and as much as 15 g/L lithium, typically 0.5 to 7 g/L. With lithium-high magnesium feed brines, the magnesium to lithium weight ratio in the feed is in the range of about 1:1 to 60~ he ratio i~ usually higher than about lsl but should preerably not exceed a~out 60:1, to give the preferred ratio in the final concentrate of about 5:1 or le6s. ~he lithium in ~he concentrate can be concentrated up to a value just below its solubility, but the precipitation of lithium or any other salt should, of course, be avoided. The recovery of lithium can be increased by subjecting the diluate from the electrodialysis to one or more additional electrodialysis steps~ Thus, lithium recovery can be maximized by ~ubjecting brine to multiple-step electrodialysis, feeding diluate from one step as feed to the next electrodialysis step. If desired, an amount of magnesium : can be removed in an intermediate precipitation, wherein solution is treated with lime. Suitable concentrations of lithium in the ; f inal concentrate can be as high as about 40 ~/L, at, as stated, a magnesium to 1ithium weight ratio of about S:l or less.
20 Lithium is recovered from the concentrate as its chloride, carbonate or sulfate according to known methods.
The electr~dialyzer may be operated with brine temperatures in the range of from just above the f reezing temperature to as high as 60C. At the higher temperatures, the process is more 25 efficient but the life of the membranes is reduced. The process ; , .
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is preferably operated with brine temperatures in the range of about 5 to 50C, the optimum temperature with optimum membrane . life being about 30C.
The method is conducted at low or neutral apparen$ pH. We have 5 found that a pH above about 7 results in the undesirable precipitation of magnesium when relatively high magnesium concentrations are presentO The pH of the feed brine is, therefore, maintained at a value of less than about 7 and preferably in the range of about 2 to 6, a value of about 4 being 10 most preferred. Within the preferred range of about 2 to 6I the method proceeds without any precipitation and feed solutions with a Xg con~ent as high as 145 g/L can be processed.
The flow rate of ~olutions through the concentrate and diluate cells should be such that the linear velocity is sufficient to 15 obtain turbulent flow. The value of the linear velocity is dependent on equipment used. The flows of solutions through the concentrate and diluate cells and the anode and cathode ; compartments should be substantially balanced in order to - maintain a differential pressure across the membranes which is as 20 low s possible to maintain membrane integrity. The differential pressure should not exceed about 100 kPa and is preferably in the : range of from 0 to about 100 kPa.
The current applie~ to the electrodes i5 controlled such that the membrane current density (applied current per membrane surface 25 area) is such that water splitting is minimized. The current is ~ : :
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preferably equivalent to a current dens~ty ln the range of about 10 to SQ0 A/m2. Below about 1 A/m2, ~he ionic transfer rat~ ls too low (the rates approach those o difusive transport). Above about ~00 A/m2 there are not enough lithium ions to replenish the 5 lithium transferred from the diffusion layer at the membrane and, as a result, water splittin~ oecurs to an undesirable extent under severe concentration polarization conditions. The hi~her values of current density are required for efficient use of the equipment. Water splitting can be substantially obviated when lo operating with current densities in the range of about 100 to 450 A/m2 under conditions of turbulence in the concentrate and diluate cells. Current densitie~ in this range also provide optimum efficiency and equipment size for the most economical operation.
15 In one embodiment of the method of the invention, the lithium content in the concentrate is raised only partially in a first electrodialysis stepl while simultaneously lowering the magnesium and other multivalent cations content to a relatively low val~e.
The concentrate f rom the f irst electrodialysis step is subjected 20 to a treatment with lime in an amount sufficient to precipitate at least a major portion of the magnesium in the concentrate.
The excess calcium in the lime reacts with sulfate already present an~ is r~moved a~ gypsum. The so-treated concentrate, ater removal of precipitate, is subjected to one or more further 25 electrodialysis steps to raise the concentration of the lithium in the concentrate, while simultaneously removing substantially ". ~ . .
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all ~emaining magnesium and oth*r r~ultivalent cation~3 with he diluate. ~hls embGdiment can be carried out batch-wise, in which case one electrodialy~s unit can be used, or eontinuou~ly using two or more electrodialy~i~ uni~sO
S ~he permselective membrane~ used i n this embodiment are pref erably univalent cationic permselective ~nembranes and multi~lent anionlc perm . elective membrane~, the use of multivalent anionic perm~elective membranes being advantageou~ in ~che removal of any exces5 calcium that may be present as a result 10 of the lime treatment. In continuous operationD the type s)f membrane~ used is~ th~ second electrodialysis step can be the ~ame ~: ;as in batch operati9n when it is desired to recover lithium as lts sul~ote. In case of the recovery of lithium as chloride the ~: membranes ~re monovalent permselective.
15 l'he: in~ention will now be illu~trated by means of the :Eollowing ,~ ~
~: non-limitative examples, All tests were carried out at ambien~
, ~
'emper atur es .
, ~
A number of tests was eonducted to determine the permselectivity 20 of cationic membranes. The electrodialy~is unit corlsisted o~ a :
rectangular I,ucite TM cell partitioned into two compartment~ by : he cationic ~embrane to be tested. The effective membrane area !
wa~ 80cm~. The two compartments were filled with the brine feed and water respectively~ and the two liquid~ were slowly agitated ; ~ 2s ino turbulence) to promote d~ffu~ive tran~fer (no current wa~
, ,, ~2~72~3~32 applied). The brine eed to the cell in te ts l, 2 and 3 assayed 7.S g/L Ll, 120 g/L Mg, 1~0 g/L Na and 1.3 g~L ~, the feed in test 4 assayed 7,3 g/L Li and 104 g/L Mg and that in test 5 assayed 6.2 g/L Li and 33 g/L Mg. The trarlsfer of Li and Mg to the water side was monitored by as~aying samples of the water-containing compartment. The results are tabulated in Table Ir Apparent Test Time mg/~ mg/l Permselectivity Mem~rane h~ur~ _Li_ _~9_ Pl~ gL
lSelemion TM CMR 5 66 73 1307 24 360 460 12.9 28 410 60~ lO.g 2 Selemion TM Exp'tal A 6 84 72 1707 2~ 340 270 lg.8
maintaining the temperature in the electrodialysis in the range of about 0 to 60C; maintaining the pH of the brine fed to the unit at a value of less than about 7; passirlg flows of solutions through the diluate and concentrate cells at a linear velocity sufficient to maintain turbulent flow in said cells; removing a lithium-depleted diluate from the diluate cells; withdrawing a lithium-enriched concentrate from the concentrate cells, said concentrate containing magnesium and lithium in a weight ratio of about 5:1 or less; and recovering lithium from withdrawn concentrate.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Brines that can be treated according to the method of the .
invention are natural brines such as occurring at Searle's Lake, :; the Great Salt Lake and Clayton'Valley in the United States and : 20 at various locations in Argentina, Bolivia and Chile. Other ~ brines that can be treated are oilfield brines, geothermal brines :' ~
; ~and intermediate solutions and brines obtained in the processing o~ ores and natural brines. Such brines contain varying amounts ~: : of monovalent cations includlng lithium, multivalent cations ~ ~25 including calcium, magnesium, iron, copper and zinc and anions including sulfate, borate and chloride.
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Although the method of the invention i8 ~uitable ~or the recovery of lithium from above-mentioned solution~ and brines1 the me~hod is e~pecially u~eful in the treatment of brines which contain high ratios of m~gnesium to lithium as well a~ r tho~e that S eon~ain very low concentrations of lithium. Su~h lithium-high magnesium ~rine~ are usually first treated by evaporation in conventional evaporator~ or in solar ponds, whereby sub~tantial amounts of ~alt~ other th~n the lithium and magnesium ~alts have :
:~ been precipi ated and re~oved from the brine. Low-llthium 10~ bcines, such aB oilfield or geothermal brines, can also be :
~: : treated advantageously by the method of the present invention.
:Thus, the lithi~um brines ~uitable a~ feed for the treatment by the method:of the present invention are brines containing lithium in a concentration as low as 30 mg/L. A practical upper limit 15~ for the ~lithium concentration in a feed brine i~ about 15 g/L, :: which is~ he practically attainable concentration for most brines n so:lar evaporation. Typicall~, feed brines contain about û.5 to;7 g/L lithium. Brines containing high concentrations of mono:valent cations other than llthium may be first. at ~east ~:;20 pa~tially, evaporated to reduoe the concentrations of the : monovalent cation~ other than lithium. During such partial evaporation, major portions of sodium and po~assium salts precipitate and can be removed.
: The lithium br~ne, whether or nct partially evaporated, is fed to an electrodialysi~ unit. The electrodialysis unit or ~ ~, .. ..
~;272~382 electrodialyzer comprise~ a multiplicity of vertically arranged, alternating anion permselective exchange membrane~ and univalent cation permÆelective 2xchanse membranes, a ca~hode compartment and an anode compartment. The choice of membranes i5 very 5 important. Suitable cationic membranes must have a high permselectivity (to be defined) for lithium, a low permselectivity for multivalent cations, especially magnesium, a high resi~tance against chemical deterioration, biological fouling and thermal degradation, a low electrical resistance and lO a high mechanical strength. We have found that ~uitable ca~ionic permselective membranes are, for example, strongly acidic membranes which have a membrane matrix of a styrene di-vinyl benzene co-polymer on a polyvinyl chloride base and possess sulphonic acid radicals ~R-SO3~) as active groups~ The active 15 groups comprise 3-4 milli-equivalents per gram of dry resin which is satisfactory to provide the desired selectivity for univalent ions. In particular, we have found that suitable cationic permselective membraneæ are treated Selemion ~M CMR, Selemion TM
Experimental A (specially treated on one face) and Selemion TM
20 Experimental B (both surfaces specially treated). Suitable anionic permselective membranes must have properties similar to those for the cati~nic membranes. Suitable anionic permselective membranes are, for example, strongly basic membranes with active ~roups derived from trimethylamine (for example, R-N(cH~)3.Cl) 2s at 3-4 milli-equivalents per gram of dry resin, and having a matrix of a styrene di-vinyl benzene co-polymer on a polyvinyl ~. ~
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chloride base. In particular, Selemion TM ASV, which is permselective for univalen-t anions, or Selemion TM AMV which is non-selective for univalent anions (i.e. permeable to mono and multivalent anions) are suitable, the choice being dependent on 5 the particular embodment of the method (to be described). A
combination of the preferred membranes will, therefore, make it possible to concentrate the monovalent cations, such as Li, Na and K, and monovalent anions such ~s Cl or mono and multivalent anions such as Cl, S04, and borates. The Selemion TM membranes, lO which are manufactured by the Asahi Glass Company of Tokyo, Japan, have the desired properties. It is understood that membranes with similar properties produced by other manufactures such as Neosepta TM CM-l and Neosepta TM CMS membranes that have sulphonic acid active groups and are produced by the Tokuyama Soda Co. Ltd.
15 of Japan, are similarly suitable and that the use of combinations of other membranes may yield the desired results.
The alternating cationic and anionic membranes form alternating diluate cells and concentrate cells situated between the anode compartment and the cathode compartment. The anode and cathode 20 are made of suitable materials. For example, the anode can be made of platinum coated titanium and the cathode of stainless steel. A source of direct current is connected to the electrodes.
The lithium brine is fed to the diluate cells, preferably after removal of suspended solids. A lithium-depleted diluate is 2S withdrawn from the diluate cells. It is important to maintain turbulent conditions in the concentrate and diluate cells. This .
.
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.
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can be achieved by passing solution through the cells at a sufficient rate. At least a portion of the diluate may be recycled and fed into the diluate cells mainly to en~ure turbulent conditions. A lithium-enriched concentrate i~ withdrawn 5 from the concentrate cells as product~ If desired, at leas~ a portion of the withdrawn concentrate may be circulated as feed to ~he concentrate cells to ensure turbulent conditions. Instead of concentrate, a quantity of a dilute receiving solution of an acidic substance may be fed to the concentrate cells, mainly for reason of pH controln If desired, a quantity of acidic substance solution may be fed to the concentrate cells alone or together with and in addition to a circulated portion of the lithium concentrate. Whether the feeding of a solution of an acidic substance is necessary depends on the net water transfer in the electrodialyzer.
During electrodialysls, water i~ transferred by osmosis from the diluate to the concentrâte ~ides of the membranes and by electro osmosis, which takes place in the direction of the transferring ions. Feed brines with a high salt concentration (e~g. molar concentration of about 20) have a high osmotic pressure and thus a high rate of osmotic transfer can be expected. For such feeds, the water transfer caused by osmosis is in the opposite direction to that caused by electro-osmosis and, thus, tends to reduce the net ; water transfer. For dilute feed brines, both osmosis and electro-osmosis are in the same direction to augment the net water transfer which can be as high as 20 g mol/h or higher.
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With relatively concentrated feed brines it may be necessary to feed a make-up solution of an acidic substance or sodium sulfate to the concentrate cells, while for relatively dilute brinss the feeding of an acidic make-up solution to the concentrate cells may be unnecessary. Generally, the feeding of an acidic make-up solution is necessary when the net-water transfer rate to ~he conc~ntrate cells is less than the withdrawal rate of concentrate from the concentrate cells.
The nature of the acidic substance in the make-up solution depends on the form in which the lithium is to be recovered from the concentrate. If recovery as lithium chloride is desired, the acidic substance is a hydrochloric acid. If recovery as lithium carbonate is desired, the solution may contain sodium sulfate, sodium bisulfate or sulfuric acid, the use of sulfuric acid being preferred.
The cathode and anode compartments are rinsed with a circulating rinse solution. It was discovered that the anodic reaction yields mostly oxygen when the chloride ion concentration in the circulating anode rinse solution is kept at less than about 3 g/L. The rinse solution is preferably acidified to increase the electrical conductivity. The rinse solution can be water or a salt solution acidified to a pH of about 2. A pH of about 2 also prevents the formation of basic precipitates. The use of sodium sulfate solution with a concentration in the range of 0.1 to 1.0 molar, preferably 0.2 to 0.5 molar sodium sulfate, acidified with , ~7~
sulfuric acid to a pH of about 2, is preferred. Thi~ rin~e solution also cau~es evolution of oxygen~ thereby minimizing the evolution of chlorine~ which, unle~s recovered, con~titutes an undesirable byproduct. The same rin~e solution is circulated to 5 both the anode compartment and the cathode compartment.
When using monovalent cation permselective and anion permselective membranes, the monovalent cations and anions in the feed solution pass from the diluate cells to the concentrate cells through the cationic and anionic membranes respectively, 10 leaving multivalent cations and anions in the diluate cells. The use of monovalent permselective cationic and anionic membranes is : desired when lithium is to be recovered from concentrate as lithium chloride. When llthium is to be recovered as lithium sulfate, the use of monovalent cation permselective membranes and 15 multiYalent anion permselective membranes is preferred~ The gases evolved at the electrodes are carried from the cathode and anode compartments in the rinse solution. Unlike membrane electrolysis, the volume of ga~es evolved in electrodialysis is small, especially also in relation to the volume of brine . 20 treated.
:~ The permselectivity PMl/M2 of a membrane is defined as the ratio between the specific transport rate of a first element Ml and that of a ~econd element M~ through the membrane; the specific transport rate being the quotient of the transfer rate of the 25 element over the concentration of that element. In the present method, to effect separation of lithium from magnesium into a ., ~ ..
. ". : .
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I
, ..
-. ., -. , lithium-enriched concentrate, PLi/Mg should be greater than one, and preferably much greater than one. Desirable values of PLi/Mg are related to the weight ratio of Mg:Li and the number of electro dialysis steps.
For brines containing both lithium and multivalent cations, especially magnesium, the conventional processing of such brines by lime addition to precipitate magnesium limits the Mg:Li weight ratio from about 0.5:1 to as high as about 7:1. The ratio is preferably limited to 5:1. Ratios of higher than about 7:1 can cause formation of unmanageable precipitates. The Mg:Li weight ratio in concentrates obtained as final product by electrodialysis and to be subjected to further treatment should, therefore, also be restricted to an upper value of about 5:1 or less to avoid difficulties in subsequent processing. However, by establishing the number of electrodialysis steps in relation to the PLi/Mg value, feed brines with much higher Mg:Li ratios can be processed. For example, a brine containing magnesium and lithium in a weight ratio of 20:1 can be treated by electrodialysis using membranes having values for PLi/Mg of > 4, 1.5, or 1.1 in 1, 4 and 15 steps of electrodialysis preferably arranged in series, respectively, to give a final concentrate product with a maximum Mg:Li weight ratio of about 5:1 or less. In multi-stsp electrodialysis to improve the Mg:Li ratio, the concentrate ~rom one step i5 used as feed in a subsequent step, the last electrodialysis giving a final concentrate having the preferred Mg:Li ratio of not ~reater than about 5:1.
.~
~2~%~
A~ stated above, the lithlum feed brine may contain a~ little as 30 mg/L l~thium and as much as 15 g/L lithium, typically 0.5 to 7 g/L. With lithium-high magnesium feed brines, the magnesium to lithium weight ratio in the feed is in the range of about 1:1 to 60~ he ratio i~ usually higher than about lsl but should preerably not exceed a~out 60:1, to give the preferred ratio in the final concentrate of about 5:1 or le6s. ~he lithium in ~he concentrate can be concentrated up to a value just below its solubility, but the precipitation of lithium or any other salt should, of course, be avoided. The recovery of lithium can be increased by subjecting the diluate from the electrodialysis to one or more additional electrodialysis steps~ Thus, lithium recovery can be maximized by ~ubjecting brine to multiple-step electrodialysis, feeding diluate from one step as feed to the next electrodialysis step. If desired, an amount of magnesium : can be removed in an intermediate precipitation, wherein solution is treated with lime. Suitable concentrations of lithium in the ; f inal concentrate can be as high as about 40 ~/L, at, as stated, a magnesium to 1ithium weight ratio of about S:l or less.
20 Lithium is recovered from the concentrate as its chloride, carbonate or sulfate according to known methods.
The electr~dialyzer may be operated with brine temperatures in the range of from just above the f reezing temperature to as high as 60C. At the higher temperatures, the process is more 25 efficient but the life of the membranes is reduced. The process ; , .
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is preferably operated with brine temperatures in the range of about 5 to 50C, the optimum temperature with optimum membrane . life being about 30C.
The method is conducted at low or neutral apparen$ pH. We have 5 found that a pH above about 7 results in the undesirable precipitation of magnesium when relatively high magnesium concentrations are presentO The pH of the feed brine is, therefore, maintained at a value of less than about 7 and preferably in the range of about 2 to 6, a value of about 4 being 10 most preferred. Within the preferred range of about 2 to 6I the method proceeds without any precipitation and feed solutions with a Xg con~ent as high as 145 g/L can be processed.
The flow rate of ~olutions through the concentrate and diluate cells should be such that the linear velocity is sufficient to 15 obtain turbulent flow. The value of the linear velocity is dependent on equipment used. The flows of solutions through the concentrate and diluate cells and the anode and cathode ; compartments should be substantially balanced in order to - maintain a differential pressure across the membranes which is as 20 low s possible to maintain membrane integrity. The differential pressure should not exceed about 100 kPa and is preferably in the : range of from 0 to about 100 kPa.
The current applie~ to the electrodes i5 controlled such that the membrane current density (applied current per membrane surface 25 area) is such that water splitting is minimized. The current is ~ : :
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preferably equivalent to a current dens~ty ln the range of about 10 to SQ0 A/m2. Below about 1 A/m2, ~he ionic transfer rat~ ls too low (the rates approach those o difusive transport). Above about ~00 A/m2 there are not enough lithium ions to replenish the 5 lithium transferred from the diffusion layer at the membrane and, as a result, water splittin~ oecurs to an undesirable extent under severe concentration polarization conditions. The hi~her values of current density are required for efficient use of the equipment. Water splitting can be substantially obviated when lo operating with current densities in the range of about 100 to 450 A/m2 under conditions of turbulence in the concentrate and diluate cells. Current densitie~ in this range also provide optimum efficiency and equipment size for the most economical operation.
15 In one embodiment of the method of the invention, the lithium content in the concentrate is raised only partially in a first electrodialysis stepl while simultaneously lowering the magnesium and other multivalent cations content to a relatively low val~e.
The concentrate f rom the f irst electrodialysis step is subjected 20 to a treatment with lime in an amount sufficient to precipitate at least a major portion of the magnesium in the concentrate.
The excess calcium in the lime reacts with sulfate already present an~ is r~moved a~ gypsum. The so-treated concentrate, ater removal of precipitate, is subjected to one or more further 25 electrodialysis steps to raise the concentration of the lithium in the concentrate, while simultaneously removing substantially ". ~ . .
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all ~emaining magnesium and oth*r r~ultivalent cation~3 with he diluate. ~hls embGdiment can be carried out batch-wise, in which case one electrodialy~s unit can be used, or eontinuou~ly using two or more electrodialy~i~ uni~sO
S ~he permselective membrane~ used i n this embodiment are pref erably univalent cationic permselective ~nembranes and multi~lent anionlc perm . elective membrane~, the use of multivalent anionic perm~elective membranes being advantageou~ in ~che removal of any exces5 calcium that may be present as a result 10 of the lime treatment. In continuous operationD the type s)f membrane~ used is~ th~ second electrodialysis step can be the ~ame ~: ;as in batch operati9n when it is desired to recover lithium as lts sul~ote. In case of the recovery of lithium as chloride the ~: membranes ~re monovalent permselective.
15 l'he: in~ention will now be illu~trated by means of the :Eollowing ,~ ~
~: non-limitative examples, All tests were carried out at ambien~
, ~
'emper atur es .
, ~
A number of tests was eonducted to determine the permselectivity 20 of cationic membranes. The electrodialy~is unit corlsisted o~ a :
rectangular I,ucite TM cell partitioned into two compartment~ by : he cationic ~embrane to be tested. The effective membrane area !
wa~ 80cm~. The two compartments were filled with the brine feed and water respectively~ and the two liquid~ were slowly agitated ; ~ 2s ino turbulence) to promote d~ffu~ive tran~fer (no current wa~
, ,, ~2~72~3~32 applied). The brine eed to the cell in te ts l, 2 and 3 assayed 7.S g/L Ll, 120 g/L Mg, 1~0 g/L Na and 1.3 g~L ~, the feed in test 4 assayed 7,3 g/L Li and 104 g/L Mg and that in test 5 assayed 6.2 g/L Li and 33 g/L Mg. The trarlsfer of Li and Mg to the water side was monitored by as~aying samples of the water-containing compartment. The results are tabulated in Table Ir Apparent Test Time mg/~ mg/l Permselectivity Mem~rane h~ur~ _Li_ _~9_ Pl~ gL
lSelemion TM CMR 5 66 73 1307 24 360 460 12.9 28 410 60~ lO.g 2 Selemion TM Exp'tal A 6 84 72 1707 2~ 340 270 lg.8
3 Selemion TM Exp'tal B 6 76 65 17.8 24 330 255 20~4
4 Selemion ~ CMv 5 86 300 4.0 24 430 ll~ 5.6 Ionac TM MC3470 5 lO 23 2.3 2~ 34 6~ 2.9 ~ Supplied by Sybron Chemieal Division It can be seen that the three membranes tested ~n tests l, 2 and 3 displayed an apparent perm electivity (PLi/Mg~ in the range of ll to 20, while those tested in tests 4 and 5 had a PLiJM9 which b' ~
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, were in6uffisient to expect ef$icient Li-Mg separation by electrodialy~is. The diffusion transfer rate without the application o~ current was very low and resulted in inefficient use of equipment.
~ample 2 This test was carried out in order to increase the difusion transfer rate with the same feed as in Test No. 1 of Example 1.
An electrodlalyzer with an effective membrane area of 1548 cm2 was used, with turbulent flow conditions in the cells. No : 10 current was applied. The membranes were Selemion TM Experimental A and Selemion TM ASV as the cation and anion permselective membranes, respectively. The dil~ate and concentrate circulating streams af~er 7 hours assayed as shown in Table II.
Table II
,' ~ ~ .
Diluate 3.1 72 Concentrate 2.8 16 As can be seen from the results, the Li ionic flux ~transfer rate 15 per area o~ membrane) was doubled compared to results obtained in Example 1 with the improved cell hydrodynamics. However, the '. increase in;the flux of the more concentrated Mg in the feed was approximately tenfold. The P~i/M9of 4.1 obtained was satisfactory to achieve a desirable Li-Mg separation in one stage 20 with a Mg.Li weight ratio of 16 in the feed brine.
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. , `, , 3L%~;29l32 .E.xample 3 This te~t ~hows the effect of applied dc potential. An electrodialy~is unit with two diluate and one concentrate compar'cments, equipped with Selemion Tl!q CMR ~cationic) and
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.
, were in6uffisient to expect ef$icient Li-Mg separation by electrodialy~is. The diffusion transfer rate without the application o~ current was very low and resulted in inefficient use of equipment.
~ample 2 This test was carried out in order to increase the difusion transfer rate with the same feed as in Test No. 1 of Example 1.
An electrodlalyzer with an effective membrane area of 1548 cm2 was used, with turbulent flow conditions in the cells. No : 10 current was applied. The membranes were Selemion TM Experimental A and Selemion TM ASV as the cation and anion permselective membranes, respectively. The dil~ate and concentrate circulating streams af~er 7 hours assayed as shown in Table II.
Table II
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Diluate 3.1 72 Concentrate 2.8 16 As can be seen from the results, the Li ionic flux ~transfer rate 15 per area o~ membrane) was doubled compared to results obtained in Example 1 with the improved cell hydrodynamics. However, the '. increase in;the flux of the more concentrated Mg in the feed was approximately tenfold. The P~i/M9of 4.1 obtained was satisfactory to achieve a desirable Li-Mg separation in one stage 20 with a Mg.Li weight ratio of 16 in the feed brine.
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. , `, , 3L%~;29l32 .E.xample 3 This te~t ~hows the effect of applied dc potential. An electrodialy~is unit with two diluate and one concentrate compar'cments, equipped with Selemion Tl!q CMR ~cationic) and
5 Selemior~ TM ASV (anionic) membrane8 having an effective membrane atea of 80cm~, was used. Electrode~ were placed in separate compartment~. The cathode was made of stainless steel and the anode of platlnum. With the exception of the electrode compartments the cell was static (i.e. no through-flow3, bu~ the 10 compartments were agitated. A circulating electrode rinse solution was used and controlled at pH 2 by the addition of ~Cl~
A current of 0.5 A was passed for 120 minutes and the ionic flux was monitored by sampling the content of the concentrate cell for Li and Mg assay. Resul s are shown in Table III.
~', Tal21 e I Il Time oncentr ate min . msl~ mg/L Mg ~ ~i/~SI
. 30 46 83 7.6 :~, `~ : 120 250 350 10.1 ,.
15 It can be seen that the application of the relatively small : current of 62.5 A/m2 resulted in an approximately tenfold increase i~ the ionic 1ux, compared to results in Example 1.
~`~ The application of current and the reQulting increased ionic flux due to :electro transport enabled efficlent use of equipmentO
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~7%~82 A multi-cell electrodialyzer containing 11 pairs of 5elemion T~
CMR cationic and Selemion TM ASV anionic membrane~ was used. The unit had intermembrane distances of 0.7~ mm and contained 10 diluate and 9 concentrate cells. The electrodes were positioned in separate electrode compartments. The anode was made of platinum-plated titanium and the cathode of stainless steel.
The initial feed to the diluate cells consisted o~ lOL brine containing 7 g/L Li and 135 g/L M9O The diluate was recirculated to the diluate cells. The concentrate stream was circulated to the concentrate cells and consisted initially of 0.8L 0.05 M HCl~
The electrode rinse solution was circulated to the electrode compartments and consisted initially of watPr adjusted with HCl to p~ 2.
The circulation flow rates of the concentrate and diluate streams were adjusted to give a linear velocity of S cmJsec which was sufficient to ensure turbulent c~nditions in the cells. The electrode rinse streams were adjusted ~o that the differential pressure between the concentrate and the rinse streams was 3 kPaq ; 2a The electrodialyzer was operated at a curr nt density of 100 A/m2 for S hoursr .~he resulting concentrate and diluate streams were analyzed for Li and ~9 and the Mg to Li weight ratios were calculated. The results are given in Table IVq ' L.
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Diluate 5.6 132 23.6 Concentrate 16 40 2.5 PLi/~g was calculated to be 9.4. The re~ults show that a Mg:Li ra~io in ~he concentrate product ~tream as low as 2.5 can be : obtained.
.~
5 This example illustrates that dilute iEeed solutions can be successfully treated. The equipment was the same as for Example 4. A feed brine ~olution containing 0.07 g/l Li and 1.35 9/1 Mg ; was fed at 18 L/hr, and the diluate stream was recycled at a rate sufficient to maintain a linear velocity of ~ cm/sec in the 10 dilua~e cells. The concentrate stream was recirculated through ~: ~he concentrate cells at 5 cm~sec and drawn off at 260 mL/hr.
There was no need for fresh input because of water tran~fer from 'che diluate stream. The electrodialyzer was operated at a current density of 205 A/m~. The pH in the electrode rinse 15 solution was controlled at a value of 2. The Li and ~9 content .
of the var~ous streams were analyzed and the Mg to Li weight : : ratio0 were calculated. The results are shown in Table v as follows:
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_ St~e~n ~a~i gL~
Peed 0.07 1.35 19.3 Diluate 0.029 0.87 30 Concentrate 2.8 33 11.8 It can be seen that the electrodialysis was effectiYe in concentratin~ lithium from a dilute feed brine.
Example ~:
This example illustrates Li recovery versu~ Li-Mg separation.
5 The equipment employed was as described for example 4. The initial feed brine contained 6.8 g/L Li and 122 g/L Mg. 1500 mL
feed brine was circulated through the diluate cells at a linear velocity of 5 cm/sec. The concentrate solution, initially ~00 ml of 0.05 M HCl,was also circulated at the same linear velocity.
10 The electrodialyzer was operated at 200 A/m2 and at 300 A/m2.
Sample6 of the concentrate and diluate recirculating streams were taken for ~i and Mg analyses at certain time intervals. The pH
of these two streams was not controlled, but the electrode rinse stream was maintained at pH 2.
15 The results obtained at 200 A/m2 are shown in Table VI~
:
.
. . .:
~L~d72~9~32 ~1* Vl Li Time Recovery* ~ LLD ~_5L~ n~n~e S~ mL
~miBL ~g~L.h~ Q/h-Mq n~ Li a/L hi ~ M~oLi 0 0 6.8 122 17.9 0 0 32 4.3 90 20~9 2.7 10.0 3.7 120 53 3.3 7~ 21.2 5.0 16.~ 3.2 180 64 2.5 6~ 24. 7.0 30.0 4.3 300 74 1.8 ~ 33.3 8.5 38.0 4.
360 79 1.5 5~ 37.3 8.7 40.~ 4.6 * Calculated on the feed solution The results obtained at 300 A/m2 are shown in Table VII.
T~
LiDuluate Stream Concentrate Stream Rec~veryMg.Li Mg:Li ~ %weight ratio wei~h~_ra~io : 25 24 3 ~: 80 ~4 12 It can be seen from the results tabulated in Tables VI and YII
that the Mg:Li weight ratio in the concentrate stream increased ~;~with the extent of Li removal from the original brine feed. The ~:S results in ~able VI show a satisfactorily low ratio of less than 5 coul~ be obtained at a current density of 200 AJm2 in a single stage with a 79~ recovery of lithium. The results in Table VII, however, show that at the higher current density of 300 A/m2, the .
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Li recovery must be restricted to less than 50~ in order to obtain the desired low Mg:Li weight ratlo in the concentrate. It follows that, in order to obtain the desired low ratio as well as a high recovery, the el ctrodialysis must be carried out in more 5 than one step.
Example 7 This example illustrates that diluate from a f irst stage electrodialysis can be subjected to further electrodialysis to give increased Li recovery with substantial separation f rom Mg.
lo The equipment employed was as described for Example 4. A first ; stage electrodialysis with a feed brine containing 7 g/L Li and 135 g/L Mg wa~ carried out at 290 A/m2. 45% of the lithium was recovered in a concentrate with a Mg:Li weight ratio of 3.3:1 g/L
Li and 105 g~L Mg, circulating diluate stream of a second stage 15 electrodialysis carried ou~ at 290 A/m2~ The circulating concentrate ~ream in this second s~age was initially 700 mL of 0.05 M HCl, but slowly gained volume as a result of the net water transfer from the diluate, reaching a total volume of 950 mL
: after 5 hours. The Li and Mg contents of the diluate and 20 concentrate from the second stage electrodialysis were determined : `
after 2.5 and 5 hours and analyses and calculated ~g:Li weight ratios are bho~n in Table VIII.
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~able VIII
Time Stream Feed: 2.5 4.0 105 26.3 Diluate: 2c5 3.0 96 32 Concentrateo 2.5 7.0 40 5,7 Feed: 5.0 4.0 105 26.3 Diluate: 5.0 3.0 100 33.3 Concentrate: 5.0 9.5 54 5.7 In the second electrodialysis stage, 28% of the input Li was recovered giving a concentrate with a Mg:Li weight ratio of 5.7.
Thus, by employing two electrodialysi~ stages a concentrate stream with the desired Mg:Li weight ratio was produced in the 5 first stage and the lithium recovery was improved in the second stage.
~amRle ~
This example ill~stra~es that by u~ing a non-chloride solution for the anode rinse solution, chlorine evolution can be 10 minimized~ A 0.25 Molar Na2so~ solution, adjusted to p~ 2 by the addition of ~ulphuric acid, was used as electrode rinse solution.
In the electrodialy~er operated at 6 A (345 A/m2), 2L of the rinse solution was circulated through both the anode and cathode compartments. The p~ wa~ maintained at 2 by sulphuric acid 15 addition. Chlorine evolution from the electrodialysis was monitored by measuring chlorine levels in the air in the '';
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immediate vicinity of the unit. The result0 obta~ned are compared to the case of u in~ dilute hydrochloric acid having a p~ of 2 for electrode rinse ~olution. The re~ult~ are given in Table IX.
Table IX
~hlorine l~vels in_th~iai~
TLmet min ~ s_~L~ ~Y~L Q.2~ Q~_ 0.5 ppm no~ detectable 1.0 ppm not detectable 1.5 ppm trace 2 ppm 0.5 ppm 12~ ~ ppm 1 ppm 5 A~ can be seen from the result~ for an operation at 6 A, the 0.25 M Na2so4 electrode rinse solution gave much lower chlorine levels in the air than a hydrochloric acid rinse solution. It was further determined that replacement of 20 ml/min of the sulfate solution with fresh solution allowed the chloride concentration ~; 10 in the rinse solution to be maintained at 3 g/L or less ~- throughout the operation.
Example g:
This example illustrates ~he deportment of other brine constituents. The electrodialyzer and membranes employed were as 15 described in Example 4. The brine feed contained 7 g/L Li, 130 :~ : g/L ~g, 3 g~L Na, 2.6 g/L R, 6.3 g/L B and 42 g/L SO4 with ~ chloride as the predominant anion. 3 L of the brine feed was ,: circulated through the electrodialyzer at a linear velocity of 5 ., ''.; ' ._ ~
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~27%~82 cm/sec. The concentrate stream (0.9 Ll initially 0.05 M HCl) was also circulated a~ the same rate. Electrode rinse solution, initially containing 0.25 M Na2so~, was fed at 20 mL/min and circulated at a sufficient rate to obtain approximately zero 5 differential pressure between the rinse and the other streams.
The electrodialyzer was operated at a c~rrent density of 260 A/m2. After 5 hours the various streams were analysed and the results are given in Table X.
Table X
Diluate S~am Conçentra~ Stream E~emen~Con~entFa~iQn in_~L~Qncentration in g/~
Li 203 15.0 Mg 93. 50.0 Na 0.39 6.5 K 0.2 4.0 5.8 1.9 ~ S04 41.6 0.45 ; It can be seen from the results that Na and R reported 10 substantially with Li in the concentrate stream. The value of PLi/Mg was 12.1 compared with a value for PLi/Na f 0.4 and a value of P Li/~ of 0.3. It follows that the apparent ease of : tra~sport (i.e. to the concentrate stream) was in the order R >
Na > Li Mg. Only 0.3% of the S04 and less than 10% of the 15 boron in the feed brine r~ported to the concentrate stream.
Ex~mpl~ 10 This example illustrates that Li can be recovered in a highly concentrated solution, substantially free of multivalent cations, ~'.
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particularly Mg and Ca, by multi-step electrodialy~is and removal of Mg by treatment with lime. A brine containing 7 g/L Li and 135 g/L Mg was fed to a first electrodialysi~, using the unit as used in Example 4, carried out at 200 A/m2. The concentrate, 5 which contained 9 g/L Li and 42 g/L Mg (Mq:Li weight ratio 4~67~y was treated with a ~0~ calcium hydroxide ~olution until the plE3 reached a value of 11. Calcium remaining in solution was precipitated ~y adding sulfuric acid. The precipi~ate of magnesium hydro~ide and gypsum wa~ removed by filtration.
10 Calcium remaining in solution was precipitated with sulfuric acid and precipitate removed. The filtrate, which contained 6.5 g/L
Li, 0.0009 g/L Mg and 0.04 g/L Ca,was adjusted with hydrochloric acid to a p~ of 4. The adjusted iltrate was fed to the diluate cells for a second electrodialysis~ The second electrodialysis 15 was carried out for 2 hours at 405 A/m2 and yielded a diluate containing 0.05 g/L Li, 0.0007 g/L Mg and 0.03 g/L Ca, and a concentrate containing 15.5 g/L Li, 0.0014 g/L Mg and 0.008 g/L
Ca. The Li recovery in the concentrate of the first electrodialysis was 83% and oE the second 95% for an overall 20 recovery of 78.9% of the Li from the original brine. During each electrodialysis step~ diluate and concentrate solutions were circulated to the diluate and concentrate cells, respectively.
~ The electrode compartments were rinsed with a 0.25 M Na2so~
:~solution ~djusted to pH2. Flow rates were such that turbulent 25 conditions were maintained.
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A current of 0.5 A was passed for 120 minutes and the ionic flux was monitored by sampling the content of the concentrate cell for Li and Mg assay. Resul s are shown in Table III.
~', Tal21 e I Il Time oncentr ate min . msl~ mg/L Mg ~ ~i/~SI
. 30 46 83 7.6 :~, `~ : 120 250 350 10.1 ,.
15 It can be seen that the application of the relatively small : current of 62.5 A/m2 resulted in an approximately tenfold increase i~ the ionic 1ux, compared to results in Example 1.
~`~ The application of current and the reQulting increased ionic flux due to :electro transport enabled efficlent use of equipmentO
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~7%~82 A multi-cell electrodialyzer containing 11 pairs of 5elemion T~
CMR cationic and Selemion TM ASV anionic membrane~ was used. The unit had intermembrane distances of 0.7~ mm and contained 10 diluate and 9 concentrate cells. The electrodes were positioned in separate electrode compartments. The anode was made of platinum-plated titanium and the cathode of stainless steel.
The initial feed to the diluate cells consisted o~ lOL brine containing 7 g/L Li and 135 g/L M9O The diluate was recirculated to the diluate cells. The concentrate stream was circulated to the concentrate cells and consisted initially of 0.8L 0.05 M HCl~
The electrode rinse solution was circulated to the electrode compartments and consisted initially of watPr adjusted with HCl to p~ 2.
The circulation flow rates of the concentrate and diluate streams were adjusted to give a linear velocity of S cmJsec which was sufficient to ensure turbulent c~nditions in the cells. The electrode rinse streams were adjusted ~o that the differential pressure between the concentrate and the rinse streams was 3 kPaq ; 2a The electrodialyzer was operated at a curr nt density of 100 A/m2 for S hoursr .~he resulting concentrate and diluate streams were analyzed for Li and ~9 and the Mg to Li weight ratios were calculated. The results are given in Table IVq ' L.
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Diluate 5.6 132 23.6 Concentrate 16 40 2.5 PLi/~g was calculated to be 9.4. The re~ults show that a Mg:Li ra~io in ~he concentrate product ~tream as low as 2.5 can be : obtained.
.~
5 This example illustrates that dilute iEeed solutions can be successfully treated. The equipment was the same as for Example 4. A feed brine ~olution containing 0.07 g/l Li and 1.35 9/1 Mg ; was fed at 18 L/hr, and the diluate stream was recycled at a rate sufficient to maintain a linear velocity of ~ cm/sec in the 10 dilua~e cells. The concentrate stream was recirculated through ~: ~he concentrate cells at 5 cm~sec and drawn off at 260 mL/hr.
There was no need for fresh input because of water tran~fer from 'che diluate stream. The electrodialyzer was operated at a current density of 205 A/m~. The pH in the electrode rinse 15 solution was controlled at a value of 2. The Li and ~9 content .
of the var~ous streams were analyzed and the Mg to Li weight : : ratio0 were calculated. The results are shown in Table v as follows:
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Peed 0.07 1.35 19.3 Diluate 0.029 0.87 30 Concentrate 2.8 33 11.8 It can be seen that the electrodialysis was effectiYe in concentratin~ lithium from a dilute feed brine.
Example ~:
This example illustrates Li recovery versu~ Li-Mg separation.
5 The equipment employed was as described for example 4. The initial feed brine contained 6.8 g/L Li and 122 g/L Mg. 1500 mL
feed brine was circulated through the diluate cells at a linear velocity of 5 cm/sec. The concentrate solution, initially ~00 ml of 0.05 M HCl,was also circulated at the same linear velocity.
10 The electrodialyzer was operated at 200 A/m2 and at 300 A/m2.
Sample6 of the concentrate and diluate recirculating streams were taken for ~i and Mg analyses at certain time intervals. The pH
of these two streams was not controlled, but the electrode rinse stream was maintained at pH 2.
15 The results obtained at 200 A/m2 are shown in Table VI~
:
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~L~d72~9~32 ~1* Vl Li Time Recovery* ~ LLD ~_5L~ n~n~e S~ mL
~miBL ~g~L.h~ Q/h-Mq n~ Li a/L hi ~ M~oLi 0 0 6.8 122 17.9 0 0 32 4.3 90 20~9 2.7 10.0 3.7 120 53 3.3 7~ 21.2 5.0 16.~ 3.2 180 64 2.5 6~ 24. 7.0 30.0 4.3 300 74 1.8 ~ 33.3 8.5 38.0 4.
360 79 1.5 5~ 37.3 8.7 40.~ 4.6 * Calculated on the feed solution The results obtained at 300 A/m2 are shown in Table VII.
T~
LiDuluate Stream Concentrate Stream Rec~veryMg.Li Mg:Li ~ %weight ratio wei~h~_ra~io : 25 24 3 ~: 80 ~4 12 It can be seen from the results tabulated in Tables VI and YII
that the Mg:Li weight ratio in the concentrate stream increased ~;~with the extent of Li removal from the original brine feed. The ~:S results in ~able VI show a satisfactorily low ratio of less than 5 coul~ be obtained at a current density of 200 AJm2 in a single stage with a 79~ recovery of lithium. The results in Table VII, however, show that at the higher current density of 300 A/m2, the .
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Li recovery must be restricted to less than 50~ in order to obtain the desired low Mg:Li weight ratlo in the concentrate. It follows that, in order to obtain the desired low ratio as well as a high recovery, the el ctrodialysis must be carried out in more 5 than one step.
Example 7 This example illustrates that diluate from a f irst stage electrodialysis can be subjected to further electrodialysis to give increased Li recovery with substantial separation f rom Mg.
lo The equipment employed was as described for Example 4. A first ; stage electrodialysis with a feed brine containing 7 g/L Li and 135 g/L Mg wa~ carried out at 290 A/m2. 45% of the lithium was recovered in a concentrate with a Mg:Li weight ratio of 3.3:1 g/L
Li and 105 g~L Mg, circulating diluate stream of a second stage 15 electrodialysis carried ou~ at 290 A/m2~ The circulating concentrate ~ream in this second s~age was initially 700 mL of 0.05 M HCl, but slowly gained volume as a result of the net water transfer from the diluate, reaching a total volume of 950 mL
: after 5 hours. The Li and Mg contents of the diluate and 20 concentrate from the second stage electrodialysis were determined : `
after 2.5 and 5 hours and analyses and calculated ~g:Li weight ratios are bho~n in Table VIII.
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~able VIII
Time Stream Feed: 2.5 4.0 105 26.3 Diluate: 2c5 3.0 96 32 Concentrateo 2.5 7.0 40 5,7 Feed: 5.0 4.0 105 26.3 Diluate: 5.0 3.0 100 33.3 Concentrate: 5.0 9.5 54 5.7 In the second electrodialysis stage, 28% of the input Li was recovered giving a concentrate with a Mg:Li weight ratio of 5.7.
Thus, by employing two electrodialysi~ stages a concentrate stream with the desired Mg:Li weight ratio was produced in the 5 first stage and the lithium recovery was improved in the second stage.
~amRle ~
This example ill~stra~es that by u~ing a non-chloride solution for the anode rinse solution, chlorine evolution can be 10 minimized~ A 0.25 Molar Na2so~ solution, adjusted to p~ 2 by the addition of ~ulphuric acid, was used as electrode rinse solution.
In the electrodialy~er operated at 6 A (345 A/m2), 2L of the rinse solution was circulated through both the anode and cathode compartments. The p~ wa~ maintained at 2 by sulphuric acid 15 addition. Chlorine evolution from the electrodialysis was monitored by measuring chlorine levels in the air in the '';
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immediate vicinity of the unit. The result0 obta~ned are compared to the case of u in~ dilute hydrochloric acid having a p~ of 2 for electrode rinse ~olution. The re~ult~ are given in Table IX.
Table IX
~hlorine l~vels in_th~iai~
TLmet min ~ s_~L~ ~Y~L Q.2~ Q~_ 0.5 ppm no~ detectable 1.0 ppm not detectable 1.5 ppm trace 2 ppm 0.5 ppm 12~ ~ ppm 1 ppm 5 A~ can be seen from the result~ for an operation at 6 A, the 0.25 M Na2so4 electrode rinse solution gave much lower chlorine levels in the air than a hydrochloric acid rinse solution. It was further determined that replacement of 20 ml/min of the sulfate solution with fresh solution allowed the chloride concentration ~; 10 in the rinse solution to be maintained at 3 g/L or less ~- throughout the operation.
Example g:
This example illustrates ~he deportment of other brine constituents. The electrodialyzer and membranes employed were as 15 described in Example 4. The brine feed contained 7 g/L Li, 130 :~ : g/L ~g, 3 g~L Na, 2.6 g/L R, 6.3 g/L B and 42 g/L SO4 with ~ chloride as the predominant anion. 3 L of the brine feed was ,: circulated through the electrodialyzer at a linear velocity of 5 ., ''.; ' ._ ~
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~27%~82 cm/sec. The concentrate stream (0.9 Ll initially 0.05 M HCl) was also circulated a~ the same rate. Electrode rinse solution, initially containing 0.25 M Na2so~, was fed at 20 mL/min and circulated at a sufficient rate to obtain approximately zero 5 differential pressure between the rinse and the other streams.
The electrodialyzer was operated at a c~rrent density of 260 A/m2. After 5 hours the various streams were analysed and the results are given in Table X.
Table X
Diluate S~am Conçentra~ Stream E~emen~Con~entFa~iQn in_~L~Qncentration in g/~
Li 203 15.0 Mg 93. 50.0 Na 0.39 6.5 K 0.2 4.0 5.8 1.9 ~ S04 41.6 0.45 ; It can be seen from the results that Na and R reported 10 substantially with Li in the concentrate stream. The value of PLi/Mg was 12.1 compared with a value for PLi/Na f 0.4 and a value of P Li/~ of 0.3. It follows that the apparent ease of : tra~sport (i.e. to the concentrate stream) was in the order R >
Na > Li Mg. Only 0.3% of the S04 and less than 10% of the 15 boron in the feed brine r~ported to the concentrate stream.
Ex~mpl~ 10 This example illustrates that Li can be recovered in a highly concentrated solution, substantially free of multivalent cations, ~'.
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particularly Mg and Ca, by multi-step electrodialy~is and removal of Mg by treatment with lime. A brine containing 7 g/L Li and 135 g/L Mg was fed to a first electrodialysi~, using the unit as used in Example 4, carried out at 200 A/m2. The concentrate, 5 which contained 9 g/L Li and 42 g/L Mg (Mq:Li weight ratio 4~67~y was treated with a ~0~ calcium hydroxide ~olution until the plE3 reached a value of 11. Calcium remaining in solution was precipitated ~y adding sulfuric acid. The precipi~ate of magnesium hydro~ide and gypsum wa~ removed by filtration.
10 Calcium remaining in solution was precipitated with sulfuric acid and precipitate removed. The filtrate, which contained 6.5 g/L
Li, 0.0009 g/L Mg and 0.04 g/L Ca,was adjusted with hydrochloric acid to a p~ of 4. The adjusted iltrate was fed to the diluate cells for a second electrodialysis~ The second electrodialysis 15 was carried out for 2 hours at 405 A/m2 and yielded a diluate containing 0.05 g/L Li, 0.0007 g/L Mg and 0.03 g/L Ca, and a concentrate containing 15.5 g/L Li, 0.0014 g/L Mg and 0.008 g/L
Ca. The Li recovery in the concentrate of the first electrodialysis was 83% and oE the second 95% for an overall 20 recovery of 78.9% of the Li from the original brine. During each electrodialysis step~ diluate and concentrate solutions were circulated to the diluate and concentrate cells, respectively.
~ The electrode compartments were rinsed with a 0.25 M Na2so~
:~solution ~djusted to pH2. Flow rates were such that turbulent 25 conditions were maintained.
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Claims (26)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for the recovery of lithium from brines containing monovalent cations including lithium, multivalent cations including magnesium and monovalent and multivalent anions which method comprises the steps of subjecting brine to electrodialysis; feeding brine to diluate cells of an electrodialysis unit comprising a multiplicity of alternating monopolar cationic permselective membranes and monopolar anionic permselective membranes, said membranes defining alternating diluate and concentrate cells, an anode compartment and a cathode compartment, an anode positioned in the anode compartment and a cathode positioned in the cathode compartment; applying an electrical current between the anode and the cathode at a value such that the value of the corresponding current density is in the range of about 10 to 500 A/m2; maintaining the temperature in the unit in the range of about 0 to 60°C; maintaining the pH of the brine fed to the electrodialysis at a value of less than about 7;
passing flows of solutions through the diluate and concentrate cells at a linear velocity sufficient to maintain turbulent flow in said cells; removing a lithium-depleted diluate from the diluate cells; withdrawing a lithium-enriched concentrate from the concentrate cells, said concentrate containing magnesium and lithium in a weight ratio of about 5:1 or less;
and recovering lithium from withdrawn concentrate.
passing flows of solutions through the diluate and concentrate cells at a linear velocity sufficient to maintain turbulent flow in said cells; removing a lithium-depleted diluate from the diluate cells; withdrawing a lithium-enriched concentrate from the concentrate cells, said concentrate containing magnesium and lithium in a weight ratio of about 5:1 or less;
and recovering lithium from withdrawn concentrate.
2. A method as claimed in claim 1, wherein said membranes have a membrane matrix of a styrene di-vinyl benzene copolymer and have active groups in an amount in the range of about 3 to 4 milli-equivalents per gram of dry resin, the active groups of the cationic membranes being sulphonic acid radicals and the active groups of the anionic membranes being a derivative of trimethylamine.
3. A method as claimed in claim 1, wherein the current density is in the range of about 100 to 450 A/m2.
4. A method as claimed in claim 1, wherein the pH of solutions passing through the diluate and concentrate cells is in the range of about 2 to 6.
5. A method as claimed in claim 1, wherein the temperature in the electrodialysis is maintained in the range of about 5 to 50°C.
6. A method as claimed in claim 1, wherein the flows of solutions passing through the diluate and concentrate cells are substantially balanced and the differential pressure across the membranes does not exceed about 100 kPa.
7. A method as claimed in claim 1, wherein brine fed to diluate cells contains magnesium and lithium in a weight ratio in the range of about 1:1 to 60:10
8. A method 93 claimed in claim 1 or 2, wherein brine fed to diluate cells contains lithium in the range of about 0.03 to 15 g/L.
9. A method as claimed in claim 1, wherein at least a portion of the diluate removed from the diluate cells is recycled to the diluate cells.
10. A method as claimed in claim 1, wherein at least a portion of the concentrate withdrawn from concentrate cells is recycled to the concentrate cells.
11. A method as claimed in claim 1, wherein a quantity of a make-up solution of an acidic substance or sodium sulfate is fed to the concentrate cells when the net water transfer rate to the concentrate cell in the electrodialysis is less than the withdrawal rate of concentrate from the concentrate cells, aid acidic substance being chosen from hydrochloric acid, sulfuric acid and sodium bisulfate.
12. A method as claimed in claim 1, wherein the anode compartment and the cathode compartment are rinsed with a circulating rinse solution having a pH of about 2.
13. A method as claimed in claim 1, wherein the anode compartment and the cathode compartment are rinsed with a rinse solution containing chloride ions in a concentration of less than about 3 g/L and having a pH maintained at a value of about 2.
14. A method as claimed in claim 1, wherein the anode compartment and the cathode compartment are rinsed which a rinse solution containing sodium sulfate in a concentration in the range of 0.1 to 1,0 molar and the pH of the rinse solution is maintained at a value of about 2 with sulfuric acid.
15. A method as claimed in claim 1, wherein brine is at least partially evaporated prior to feeding to the electrodialysis unit to reduce the concentration of monovalent cations other than lithium.
16. A method as claimed in claim 1, wherein concentrate withdrawn from said concentrate cells and prior to said recovering of lithium therefrom is subjected to at least one more electrodialysis, whereby the separation of lithium from multivalent cations is improved.
17. A method as claimed in claim 1, wherein diluate withdrawn from said diluate cells is subjected to at least one more electrodialysis, whereby the recovery of lithium is improved.
18. A method as claimed in claim 1, wherein brine is subjected to a first electrodialysis whereby the brine is partially concentrated to raise the concentration of lithium and to simultaneously lower the concentration of magnesium in a concentrate, withdrawing said concentrate, subjecting withdrawn concentrate to a treatment with lime in an amount sufficient to precipitate at least a major portion of the magnesium, removing precipitated magnesium to give a treated concentrate and subjecting treated concentrate to at least one more electrodialysis to further raise the concentration of lithium and to remove substantially all remaining magnesium; and recovering a concentrate substantially free of multivalent cations.
19. A method for the recovery of lithium from brines containing monvalent cations including lithium in an amount in the range of about 0003 to 15 g/L lithium, multivalent cations including magnesium and anions which method comprises the steps of subjecting brine containing magnesium and lithium in a weight ratio in the range of 1:1 to 60:1 to at least one step of electrodialysis; feeding brine to diluate cells of an electrodialysis unit, said unit comprising a multiplicity of alternating cationic permselective membranes and anionic permselective membranes, wherein said membranes have a membrane matrix of a styrene di-vinyl benzene copolymer and have active groups in an amount in the range of about 3 to 4 milli-equivalents per gram of dry resin, the active groups of the cationic membranes being sulphonic acid radicals and the active groups of the anionic membranes being a derivative of trimethylamine, said membranes defining alternating diluate and concentrate cells, an anode compartment containing a anode and a cathode compartment containing a cathode; applying an electrical current between the anode and the cathode at a value such that the value of the corresponding current density is in the range of about 100 to 450 A/m2; removing a diluate from the diluate cells;
withdrawing lithium-enriched concentrate from the concentrate cells; maintaining the temperature in the electrodialysis in the range of about 5 to 50°C; maintaining the pH of the brine fed to the electrodialysis at a value in the range of about 2 to 6; passing flows of solutions through the diluate and concentrate cell. at a linear velocity sufficient for maintaining turbulent flow in said cells, and flows being substantially balanced and the differential pressure across the membranes being less than about 100 kPa; recycling at least a portion of the diluate removed from the diluate cells to the diluate cells;
recycling at least a portion of the concentrate withdrawn from concentrate cells to the concentrate cells; rinsing the anode compartment and the cathode compartment with a rinse solution containing chloride ions in a concentration of less than about 3 g/L; maintaining the pH of the rinse solution at a value of about 2; withdrawing a final concentrate from the electrodialysis which contains magnesium and lithium in a weight ratio not higher than about 5:1; and recovering lithium from said final concentrate.
withdrawing lithium-enriched concentrate from the concentrate cells; maintaining the temperature in the electrodialysis in the range of about 5 to 50°C; maintaining the pH of the brine fed to the electrodialysis at a value in the range of about 2 to 6; passing flows of solutions through the diluate and concentrate cell. at a linear velocity sufficient for maintaining turbulent flow in said cells, and flows being substantially balanced and the differential pressure across the membranes being less than about 100 kPa; recycling at least a portion of the diluate removed from the diluate cells to the diluate cells;
recycling at least a portion of the concentrate withdrawn from concentrate cells to the concentrate cells; rinsing the anode compartment and the cathode compartment with a rinse solution containing chloride ions in a concentration of less than about 3 g/L; maintaining the pH of the rinse solution at a value of about 2; withdrawing a final concentrate from the electrodialysis which contains magnesium and lithium in a weight ratio not higher than about 5:1; and recovering lithium from said final concentrate.
20. A method as claimed in claim 19, wherein the electrodialysis is carried out in more than one step and concentrate is subjected to at least one more electrodialysis, whereby the separation of lithium from multivalent cations is improved.
21. A method as claimed in claim 19, wherein the electrodialysis is carried out in more than one step and diluate is subjected to at least one more electrodialysis, whereby the recovery of lithium is improved.
22. A method as claimed in claim 19, wherein concentrate from a first electrodialysis is subjected to a treatment with lime in an amount sufficient to precipitate a least a portion of the magnesium prior to subjecting concentrate to any further electrodialysis.
23. A method a claimed in claim 20, wherein concentrate from a first electrodialysis is subjected to a treatment with lime in an amount sufficient to precipitate at least a portion of the magnesium prior to subjecting concentrate to any further electrodialysis.
24. A method as claimed in claim 19, wherein a quality of a make-up solution of an acidic substance or sodium sulfate is fed to the concentrate cells when the net water transfer rate to the concentrate cell in the electrodialysis is less than the withdrawal rate of concentrate from the concentrate cells, said acidic substance being chosen from hydrochloric acid, sulfuric acid and sodium bisulfate.
25. A method as claimed in claim 19, wherein the anode compartment and the cathode compartment are rinsed with a rinse solution containing sodium sulfate in a concentration in the range of 0.1 to 1.0 molar and the pH of the rinse solution is maintained at a value of about 2 with sulfuric acid,
26. A method as claimed in claim 19, wherein brine is at least partially evaporated prior to feeding to the electrodialysis unit to reduce the concentration of monovalent cations other than lithium.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000495301A CA1272982A (en) | 1985-11-14 | 1985-11-14 | Method for the recovery of lithium from solutions by electrodialysis |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000495301A CA1272982A (en) | 1985-11-14 | 1985-11-14 | Method for the recovery of lithium from solutions by electrodialysis |
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| CA1272982A true CA1272982A (en) | 1990-08-21 |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015058287A1 (en) * | 2013-10-23 | 2015-04-30 | Nemaska Lithium Inc. | Processes for preparing lithium carbonate |
| US9382126B2 (en) | 2012-05-30 | 2016-07-05 | Nemaska Lithium Inc. | Processes for preparing lithium carbonate |
| US9677181B2 (en) | 2012-04-23 | 2017-06-13 | Nemaska Lithium Inc. | Processes for preparing lithium hydroxide |
| US10036094B2 (en) | 2013-10-23 | 2018-07-31 | Nemaska Lithium Inc. | Processes and systems for preparing lithium hydroxide |
| US10544512B2 (en) | 2014-02-24 | 2020-01-28 | Nemaska Lithium Inc. | Methods for treating lithium-containing materials |
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| CN112973453A (en) * | 2021-03-19 | 2021-06-18 | 青海东台吉乃尔锂资源股份有限公司 | Method for supplementing water and diluting concentrated solution of salt lake brine |
| US11078583B2 (en) | 2013-03-15 | 2021-08-03 | Nemaska Lithium Inc. | Processes for preparing lithium hydroxide |
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-
1985
- 1985-11-14 CA CA000495301A patent/CA1272982A/en not_active Expired - Fee Related
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| US10633748B2 (en) | 2012-04-23 | 2020-04-28 | Nemaska Lithium Inc. | Processes for preparing lithium hydroxide |
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