CN102382984A - Method and device for separating magnesium and lithium and enriching lithium from salt lake brine - Google Patents

Abstract

The invention relates to a method and a device for separating magnesium and lithium from salt lake brine and enriching lithium. Anion-exchange membranes are used to separate the electrodialysis device into two areas: a lithium salt chamber and a brine chamber. The brine chamber is filled with salt lake brine, and the lithium salt chamber is filled with a supporting electrolyte solution that does not contain Mg ²⁺ ; The substrate is placed in the brine chamber as the cathode; the conductive substrate coated with the lithium-intercalated ion sieve is placed in the lithium salt chamber as the anode; driven by the external potential, Li ⁺ in the brine of the brine chamber is inserted into the ion sieve The lithium-intercalated ion sieve is formed in the lithium-salt chamber, and the lithium-intercalated ion sieve in the lithium-salt chamber releases Li ⁺ into the conductive solution, and then recovers as an ion sieve; the lithium-intercalated liquid in the brine chamber is discharged, and the salt lake brine is added again, and the electrodes in the two chambers Replace and repeat the cycle. Efficiently realize the separation of lithium and other ions, and at the same time obtain a lithium-rich solution. The method has the advantages of short flow, simple operation, low production cost, continuous operation and easy industrial application.

Description

A method and device for separating magnesium and lithium from salt lake brine and enriching lithium

technical field

The invention belongs to the field of extraction metallurgy, and specifically relates to a method and a device for directly treating salt lake brine to separate magnesium and lithium, and then enrich lithium.

Background technique

Since lithium-ion batteries were commercialized by Sony in 1990, lithium has become more and more important in modern industry, and is known as "the new energy metal in the 21st century". Due to its high energy density and long cycle life, lithium-ion Batteries are widely used in electronic equipment, and the market demand for lithium is expanding rapidly, so the mining of lithium resources becomes more important.

In nature, lithium mainly exists in two forms of ore and brine. Most lithium resources exist in brine, especially salt lake brine, and its reserves account for more than 80% of the total lithium resource reserves. With the growth of market demand, mineral lithium resources are in short supply and the mining cost is high. People begin to develop lithium resources in salt lake brine. Brine usually contains sodium, potassium, magnesium, calcium, boron, and lithium chlorides, sulfates, and carbonates, except for a few salt lakes such as Chile's Atacama Salt Lake, where the ratio of magnesium to lithium is relatively low (about 6:1) , the ratio of magnesium to lithium in most other salt lake brines is above 40, the highest reaching 1837, and lithium coexists with a large number of alkaline earth metal ions. Due to the diagonal rule, the chemical properties of Mg ²⁺ and Li ⁺ are very similar, and the separation of magnesium and lithium is very difficult, which seriously restricts the extraction and application of lithium. For a long time, extracting lithium from salt lake brine with high magnesium-lithium ratio has become a worldwide problem. Researchers use precipitation method, carbonization method, ion exchange method, solvent extraction method and other technologies to develop lithium resources in brine, but most of these methods are complicated in process, high in cost, severely corroded to equipment, and the product purity is not high, which is not conducive to Mass production.

Contents of the invention

The purpose of the present invention is to propose a method for directly separating magnesium and lithium from salt lake brine and enriching lithium and its supporting device. Efficiently realize the separation of lithium and other ions, and at the same time obtain a lithium-rich solution. The method has the advantages of short flow, simple operation, low production cost, continuous operation and easy industrial application.

A method for separating magnesium and lithium from salt lake brine and enriching lithium comprises the following steps in sequence:

(1) The electrodialysis cell of the electrodialysis device is vertically separated into two regions, a lithium salt chamber and a brine chamber, with an anion exchange membrane, the brine chamber is filled with salt lake brine, and the lithium salt chamber is filled with a Mg ^-free supporting electrolyte solution, Such as NaCl, KCl, NH ₄ Cl, Na ₂ SO ₄ , K ₂ SO ₄ , NaNO ₃ , KNO ₃ solution.

(2) Place the conductive substrate coated with the ion sieve in the brine chamber as the cathode; place the conductive substrate coated with the lithium-intercalated ion sieve in the lithium salt chamber as the anode, and under the drive of the external potential, the brine chamber Li ⁺ in the brine is embedded in the ion sieve to form a lithium-intercalated ion sieve, and at the same time, the lithium-intercalated ion sieve in the lithium salt chamber releases Li ⁺ into the conductive solution and recovers as an ion sieve; the realization of Li ⁺ in the brine chamber and Separation of Mg ²⁺ and other cations, while lithium is enriched in the lithium salt chamber to obtain a lithium-rich solution.

After the operation of the above step (2), the Li ⁺ in the brine chamber brine is embedded in the ion sieve to form a lithium-intercalated ion sieve, and the lithium-intercalated ion sieve in the lithium-salt chamber releases Li ⁺ into the conductive solution and recovers to Ion sieve; so the two electrodes can be exchanged for reuse.

Therefore, after step (2) is completed, the following operations can be performed at least once:

Drain the lithium-intercalated solution in the brine chamber, add salt lake brine again, and then replace the cathode and anode to continue electrodialysis.

Or after step (2) is completed, in order to avoid exchanging the cathode and anode each time, the following operations can be performed at least once to further separate Li ⁺ from Mg ²⁺ and other cations, and enrich lithium at the same time:

Keep the position of the anode and the cathode fixed, discharge the lithium-intercalated liquid in the brine chamber, transfer the lithium-containing solution in the lithium salt chamber to the brine chamber, and add new salt lake brine to the lithium salt chamber; that is, the brine chamber and lithium The salt chamber conversion function is used, and the electrodialysis is continued. (That is, every time the above operation is repeated, the brine chamber and the lithium salt chamber are used once for switching function)

The lithium-intercalated ion sieve directly adopts one of lithium iron phosphate or LiMn ₂ O ₄ ; the lithium iron phosphate is LiFePO ₄ , Li _x Me _y FePO ₄ , LiF _x Me _y PO ₄ , LiFePO ₄ / C, a mixture of one or more of Li _x Me _y FePO ₄ /C, LiF _x Me _y PO ₄ /C, where Me is one of Mn, Co, Mo, Ti, Al, Ni, Nb or A mixture of several types, 0<x<1, 0<y<1;

Or obtain through the following process: the electrodialysis device is separated into lithium salt chamber and brine chamber by anion exchange membrane, the brine chamber is filled with salt lake brine, and the lithium salt chamber is filled with Mg ^-free supporting electrolyte solution; The ion sieve with selective adsorption of Li ⁺ is coated on the conductive substrate, placed in the brine chamber of the electrodialysis device, the ion sieve is used as the cathode, and the inert electrode is used as the counter electrode for cathodic polarization to make the Li ⁺ in the brine Embedded in ion sieves to obtain lithium-intercalated ion sieves.

The salt lake brine includes one or more of any Li ⁺ -containing solution, the original brine in any salt lake and the brine after evaporation and concentration, and the evaporated old brine after potassium extraction.

The conductive substrate is one of ruthenium-coated titanium mesh, graphite plate, Pt group metal and its alloy foil, carbon fiber cloth, and graphite paper.

The temperature of the solution in the electrodialysis device is 0-80°C, and the pH value is 2-12; the voltage range between the two electrodes in the electrodialysis device is 0.5-2.0V.

The ion sieve is one or a mixture of iron phosphate, lithium titanate and MnO ₂ .

The iron phosphate is Fe _1-x Me _x PO ₄ , where Me is a mixture of one or more of Mn, Co, Mo, Ti, Al, Ni, Nb, and the range of x is: 0≤x≤ 0.1; lithium titanate is one or a mixture of Li ₄ Ti ₅ O ₁₂ , Li _x Me _y Ti ₅ O ₁₂ , Li ₄ Me _m Ti _n O ₁₂ ; Me is V, Fe, Co, Mn, A mixture of one or more of Al, Ba, Ag, Zr, Sr, Nb, F; 0<x<4, 0<y<4, 0<m<5, 0<n<5.

The supporting device for the above-mentioned method for separating magnesium and lithium from salt lake brine and enriching lithium includes an electrodialysis device having an electrodialysis cell separated into two spaces by an anion exchange membrane, and a cathode and an anode, and the cathode and the anode are respectively set In the two spaces separated; the cathode is a conductive substrate coated with an ion sieve, and the anode is a conductive substrate coated with a lithium-intercalated ion sieve.

The technical measures of the present invention are: independently design an electrodialysis device, adopt an ion sieve material that works stably in an aqueous solution and has a memory effect on Li ⁺ , and adjusts the potential of the system so that Li ⁺ in the solution is embedded in the crystal of the ion sieve. In the lattice, other ions remain in the solution, through which the effective separation of lithium and other ions is achieved; then the lithium-intercalated ion sieve is placed in a supporting electrolyte solution without Mg ²⁺ such as NaCl solution to adjust the system’s Potential, so that the Li ⁺ in the lithium-intercalated ion sieve is released into the solution to obtain a lithium-rich solution, which realizes the efficient separation of magnesium and lithium and the enrichment of lithium; its advantage is that during the operation of the electrodialysis device, the lithium in the brine While being embedded in the ion sieve, the lithium-intercalated ion sieve delithiates to the lithium salt chamber. This process effectively reduces energy consumption and improves the extraction efficiency of lithium.

The specific steps are:

(1). Initial lithium intercalation of ion sieve: use anion exchange membrane to separate the electrodialysis device into lithium salt room and brine room. The brine room is filled with salt lake brine, and the lithium salt room is filled with support without Mg ²⁺ Electrolyte solution: Coat the ion sieve with selective adsorption on Li ⁺ on the conductive substrate, place it in the brine chamber of the electrodialysis device, make it fully contact with the brine of the salt lake, use the ion sieve material as the cathode, and use the inert anode To polarize the electrode cathodically, the Li ⁺ in the brine is intercalated into the ion sieve to obtain the lithium-intercalated ion sieve;

(2). Separation of magnesium and lithium: Coat the ion sieve on the conductive substrate and place it in a brine chamber filled with brine as the cathode; coat the lithium-intercalated ion sieve on the conductive substrate and place it in a place that does not contain Mg ^{2 +} In the lithium salt chamber of the supporting electrolyte solution, as the anode, under the drive of the external potential, Li ⁺ in the brine in the brine chamber is intercalated into the ion sieve to form a lithium-intercalated ion sieve, while the lithium-intercalated ion in the lithium salt chamber The sieve releases Li ⁺ into the conductive solution. Since the anion exchange membrane prevents the mutual migration of cations between the two regions of the brine chamber and the lithium salt chamber, the anions pass through the exchange membrane from the brine chamber into the lithium salt chamber to maintain charge balance, while the brine chamber Li ⁺ in the solid-phase transfer to the lithium salt chamber;

(3). After step (2) is completed, in order to further separate Li ⁺ from Mg ^{2 +} and other cations, and simultaneously enrich lithium, the following operations can also be performed:

Discharge the lithium-intercalated liquid in the brine chamber, add salt lake brine again, place the ion sieve conductive substrate obtained in the lithium salt chamber in step (2) as a cathode in the brine chamber, and place the lithium-intercalated ion sieve obtained in the brine chamber The conductive matrix is placed in the lithium salt chamber as an anode, and electrodialysis is carried out to make Li ⁺ in the brine intercalate into the ion sieve, and the Li ⁺ in the lithium-intercalated ion sieve is released into the solution in the lithium salt chamber, so that the brine chamber The Li ⁺ in the brine chamber is transferred to the solution in the lithium salt chamber through solid phase, further realizing the separation of Li ⁺ in the brine chamber from Mg ²⁺ and other cations, and at the same time, lithium is enriched in the lithium salt chamber to obtain a lithium-rich solution; Lithium enrichment can be realized by repeated cycle operation according to the above electrodialysis process, and when the Li ⁺ in the lithium-rich solution reaches a certain concentration, it can be used to directly extract lithium.

In order to simplify the above operation and avoid the constant exchange of electrodes between the brine chamber and the lithium salt chamber, the above step (3) can also be operated in the following manner: after step (2) is completed, the positions of the cathode and the anode are fixed, and the brine The lithium-intercalated liquid in the chamber is discharged separately, the lithium-containing solution in the lithium salt chamber is transferred to the semi-dialysis tank (that is, the brine chamber) where the lithium-intercalated ion sieve is located, and the salt lake brine is added to the semi-dialysis tank where the ion sieve is located. (i.e. lithium-salt chamber); the original brine chamber is converted into a new lithium-salt chamber, and the former lithium-salt chamber is converted into a new brine chamber (that is, the conversion function of the brine chamber and the lithium-salt chamber is used), continue electrodialysis, and repeat the above The operation of this new step (3) realizes the separation of Li ⁺ and Mg ²⁺ and other cations in the brine, and simultaneously obtains a lithium-rich solution; repeating the above-mentioned electrodialysis process can realize the enrichment of lithium, when When the Li ⁺ in the lithium-rich solution reaches a certain concentration, it can be used to directly extract lithium.

When using the inventive method and adopting ferric phosphate as an ion sieve to separate magnesium and lithium and enrich lithium, it can be carried out as follows:

(1). Coat lithium iron phosphate on a conductive substrate, place it in a conductive solution as an anode, and use an inert electrode as a cathode; apply an external potential between the two electrodes to deintercalate Li ⁺ in lithium iron phosphate into the solution , lithium iron phosphate is converted into iron phosphate ion sieve;

(2). Separation of magnesium and lithium: the ferric phosphate ion sieve obtained in step (1) is coated on the conductive substrate, placed in a brine chamber equipped with brine, as the cathode; the lithium iron phosphate is coated on the conductive substrate, Placed in a lithium salt chamber containing a supporting electrolyte solution that does not contain Mg2 ⁺ , as an anode, driven by an external potential, the Li ⁺ in the brine of the brine chamber is inserted into the iron phosphate ion sieve to form a lithium-intercalated ion sieve. At the same time, the lithium iron phosphate in the lithium salt chamber releases Li ⁺ into the conductive solution; since the anion exchange membrane prevents the mutual migration of cations between the two regions of the brine chamber and the lithium salt chamber, the anions enter the lithium from the brine chamber through the exchange membrane. The salt chamber maintains charge balance; the overall effect of steps (1) and (2) is equivalent to the Li ⁺ in the brine chamber being transferred to the solid-phase ion sieve first, and then transferred to the lithium salt chamber, thereby separating lithium from magnesium;

Lithium iron phosphate is one or more of LiFePO ₄ , Li _x Me _y FePO ₄ , LiF _x Me _y PO ₄ , LiFePO ₄ /C, Li _x Me _y FePO ₄ /C, LiF _x Me _y PO ₄ /C Me is a mixture of one or more of the mixtures; Me is a mixture of one or more of Mg, Al, Ti, Ni, Co, Mn, Mo, Nb; 0<x<1, 0<y<1 .

The present invention has the following advantages:

The ion sieve of the present invention has good selectivity to Li ⁺ , and has large adsorption capacity and good stability, and can cyclically enrich lithium in brine;

1. This method can handle brines with different ratios of magnesium to lithium, especially the technical problem of separating magnesium and lithium from brines with high ratios of magnesium to lithium;

2. The electrodialysis device designed by this method can simultaneously complete the insertion and extraction of lithium on the two working electrodes, realize efficient and selective extraction of lithium, and have low cell voltage and low energy consumption; after completing a cycle of operation, through Replace electrodes or electrolyte solutions to achieve continuous cycle work;

3. The electrodialysis device designed by this method can simultaneously complete the enrichment of lithium while separating magnesium and lithium; and the electrodialysis device is simple in structure, easy to operate, and can recycle salt lake brine;

4. The method has low cost and is easy to produce on a large scale.

Description of drawings

Fig. 1 is the schematic diagram of top view of electrodialysis cell of the present invention;

In the figure, 1 is the anion exchange membrane, 2 is the cathode, 3 is the anode, 4 is the brine chamber, and 5 is the lithium salt chamber

Fig. 2 is the change figure of ^Li concentration of the present invention with electrodialysis time;

Fig. 3 is a graph showing the variation of Li ⁺ concentration with cycle coefficient in the present invention.

Detailed ways

In order to explain the present invention in more detail, the following examples are given for illustration, but the present invention is not limited to these examples.

Referring to Fig. 1 for the device of the present invention, the electrodialysis cell of the electrodialysis device is vertically separated into two spaces by an anion exchange membrane 1, i.e. a brine chamber 4 and a lithium salt chamber 5, and the cathode 2 and the anode 3 are respectively arranged in the two spaces separated into Inside; the cathode 2 is a conductive substrate coated with an ion sieve, and the anode 3 is a conductive substrate coated with a lithium-intercalated ion sieve.

Example 1

Mix 10g _FePO ion sieve, 0.5g high-purity graphite and 0.5g PVDF in a weight ratio of 20:1:1, and add N-methylpyrrolidone (NMP) organic solvent to the mixed powder to grind and adjust the slurry. Coated on the graphite plate, heat-preserved and dried in a vacuum box at 110°C for 12 hours, and obtained the iron phosphate ion sieve composite membrane after cooling; the iron phosphate composite membrane was placed in the brine chamber of the electrodialysis device, and the electrodialysis device The schematic diagram of the top view is shown in Figure 1; 2L of a certain salt lake brine is added to the brine chamber, and the main components and contents of the salt lake brine are shown in the following table:

Add 500mL of NaCl solution with a concentration of 20g/L into the lithium salt chamber of the electrodialysis device; use the iron phosphate ion sieve membrane as the cathode, and use the inert graphite in the lithium salt chamber as the anode, and apply a voltage of 0.5V across the electrodes , after maintaining at 25°C for 15 hours, the concentration of Li ⁺ in the brine chamber decreased to 358 mg/L, the concentration of Mg ²⁺ was about 17994 mg/L, and the adsorption capacity of Li ⁺ on iron phosphate ion sieve was about 28.4 mg/g, The adsorption capacity of Mg ²⁺ is about 1.2mg/g;

After the initial lithium intercalation is completed, the solutions in the brine chamber and the lithium salt chamber are discharged separately, the lithium intercalated ferric phosphate ion sieve membrane is placed in the lithium salt chamber, and 500 mL of NaCl solution with a concentration of 20 g/L is added; according to this example In the same method as above, 10g FePO ₄ ion sieve was made into iron phosphate composite film without lithium intercalation, this composite film was placed in the brine chamber, and 2L salt lake brine was added, the main components and contents were still shown in the above table; The ferric phosphate ion sieve membrane is used as the cathode, and the lithium-intercalated iron phosphate ion sieve membrane is used as the anode. A voltage of 0.8V is applied between the two electrodes. After the pH is 2 and maintained at 25°C for 12 hours, the Li ⁺ concentration in the brine chamber decreases. to 345mg/L, the concentration of Mg ²⁺ is about 17995mg/L, the adsorption capacity of Li ⁺ on iron phosphate ion sieve is 31mg/g, and the adsorption capacity of Mg ²⁺ is about 1mg/g; A lithium-rich solution with a Li ⁺ concentration of 561mg/L.

Example 2

Mix 9gFe _0.99 Mn _0.01 PO ₄ , 0.5g high-purity graphite and 0.5g PVDF uniformly according to the weight ratio of 90:5:5, add the mixed powder into N-methylpyrrolidone (NMP) organic solvent for grinding and slurrying, Spray or brush the slurry on the ruthenium-titanium mesh, heat and dry it at 110°C for 10 hours under vacuum conditions, and obtain the iron phosphate ion sieve composite membrane after cooling.

Put the iron phosphate composite film in the brine chamber, add 2L salt lake brine, the composition and content of the brine are shown in the following table:

Add 200mL of NaCl solution with a concentration of 50g/L into the lithium salt chamber of the electrodialysis device; use the iron phosphate ion sieve membrane as the cathode, and use the Pt electrode in the lithium salt chamber as the anode, and apply a voltage of 1.0V across the electrodes , after maintaining at 50°C for 10 hours, the concentration of Li ⁺ in the brine chamber decreased to 55.1 mg/L, the concentration of Mg ²⁺ was 1254 mg/L, and the adsorption capacity of Li ⁺ on the ferric phosphate ion sieve was 32.2 mg/g. The adsorption amount of Mg ²⁺ was 1.33 mg/g.

After the initial lithium intercalation is completed, the solutions in the brine chamber and the lithium salt chamber are discharged respectively, the lithium intercalated iron phosphate ion sieve membrane is placed in the lithium salt chamber, and 500 mL of NaCl solution with a concentration of 50 g/L is added; according to this example In the same method as above, 9g FePO ₄ ion sieve was made into iron phosphate composite membrane without intercalation of lithium, the composite membrane was placed in the brine chamber, and 2L salt lake brine was added, the main components and contents of which were shown in the table above; phosphoric acid without intercalation of lithium The iron ion sieve membrane is used as the cathode, and the lithium-intercalated iron phosphate ion sieve membrane is used as the anode. A voltage of 1.5V is applied between the two electrodes, and electrodialysis is carried out at a pH of 7 and 50°C. The concentration of Li ⁺ in the solution was analyzed, and the specific results are shown in Figure 2; after maintaining for 10 hours, the concentration of Li ⁺ in the brine chamber was reduced to 55mg/L, and the concentration of Mg2 ⁺ was about 1254mg/L. The adsorption capacity of ⁺ is about 32.2 mg/g, and the adsorption capacity of Mg ²⁺ is about 1.33 mg/g; at the same time, a lithium-rich solution with a Li ⁺ concentration of 576 mg/L is obtained in the lithium salt chamber.

Example 3

According to the method of Example 2, 3gFe _0.98 Co _0.02 PO ₄ was made into an iron phosphate composite membrane, the iron phosphate composite membrane was placed in the brine chamber, and 500mL of salt lake brine was added. The composition and content of the salt lake brine are shown in the following table:

Add 500mL of NaCl solution with a concentration of 50g/L into the lithium salt chamber, use the iron phosphate composite film as the cathode, and inert graphite as the anode, apply a voltage of 2.0V, and maintain it at 80°C for 10h. The concentration of Li ⁺ in the brine chamber Reduced to 268.4mg/L, the concentration of Mg ²⁺ is 17991mg/L, the adsorption capacity of Fe _0.98 Co _0.02 PO ₄ ion sieve to Li ⁺ is 38.6mg/g, and the adsorption capacity of Mg ²⁺ is 1.5mg/g.

According to the same method in this example, 3g of Fe _0.98 Co _0.02 PO ₄ ion sieves were fabricated into iron phosphate composite membranes without intercalation of lithium. After the initial lithium intercalation is completed, place the non-intercalated iron phosphate composite membrane in the brine chamber, add 500mL of salt lake brine, place the lithium-intercalated ion sieve in the lithium salt chamber, add 500mL of NaCl solution with a concentration of 50g/L, The lithium-intercalated ion sieve was used as the anode, and the lithium-intercalated ion sieve was used as the cathode. A voltage of 2.0V was applied between the electrodes, and the pH was maintained at 12 and 80°C for 10h. After the electrodialysis, the concentration of Li ⁺ in the brine chamber was reduced to 269.1mg/L, and the concentration of Li ⁺ in the lithium-rich solution obtained in the lithium salt chamber was 115mg/L. After the electrodialysis process is over, the morphology of the lithium-intercalated ion sieve and the non-intercalated ion sieve are transformed into each other; keeping the positions of the two electrodes unchanged, the lithium-intercalated liquid in the electrodialysis device is discharged, and the lithium-rich solution is transferred to the storage After the tank, it was added to the original brine chamber again, and 500mL of salt lake brine was added to the new brine chamber (original lithium salt chamber), and the second electrodialysis was performed under the same conditions. After the second electrodialysis, the Li ⁺ concentration in the lithium-rich solution in the lithium salt chamber reached 229mg/L.

In this way, several cycles of lithium intercalation/deintercalation electrodialysis process are carried out. After the third electrodialysis, the Li ⁺ concentration of the lithium-rich solution in the lithium salt chamber is 351 mg/L, and after the fourth electrodialysis, the lithium-rich The concentration of Li ⁺ in the solution increased to 465 mg/L; 10 consecutive electrodialysis were performed under the same conditions. After the 10th electrodialysis, the Li ⁺ concentration in the lithium-rich solution reached 1162 mg/L. The specific changes are shown in the figure 3 shown;

Example 4

10g _MnO2 is made into ion sieve composite membrane by the method of embodiment 2, _MnO2 Composite membrane is placed in brine chamber, adds 1L salt lake brine, the composition and content of salt lake brine are consistent with embodiment 3; Graphite electrode is placed in In the lithium salt chamber, add 500 mL of NaCl solution with a concentration of 20 g/L. With the _MnO2 composite film as the cathode and the graphite electrode as the anode, a voltage of 1.2V was applied and maintained at 5°C for 12h, the concentration of Li ⁺ in the brine chamber decreased to 286mg/L, and the concentration of Mg2 ⁺ was 17982mg/L, The adsorption capacity of MnO ₂ ion sieve to Li ⁺ is 21.4 mg/g, and the adsorption capacity to Mg ²⁺ is 1.8 mg/g.

According to the same method in this embodiment, 10g MnO ₂ ion sieves are made into non-lithium-intercalated MnO ₂ composite membranes. After the initial lithium intercalation is completed, place the non-intercalated iron phosphate composite membrane in the brine chamber, add 1L of salt lake brine, place the lithium-intercalated _MnO2 ion sieve in the lithium salt chamber, and add 500mL of NaCl with a concentration of 20g/L For the solution, the lithium-intercalated MnO ₂ ion sieve was used as the anode, and the non-lithiated MnO ₂ ion sieve was used as the cathode. A voltage of 1.2V was applied between the electrodes and maintained at 5°C for 12h. After the electrodialysis, the concentration of Li ⁺ in the brine chamber was reduced to 284.2 mg/L, and the concentration of Li ⁺ in the lithium-rich solution obtained in the lithium salt chamber was 428.3 mg/L.

After the end of electrodialysis, the morphology of the lithium-intercalated ion sieve and the non-intercalated lithium-ion sieve are mutually transformed; keep the positions of the two electrodes unchanged, discharge the lithium-intercalated liquid in the electrodialysis device, and transfer 500mL of lithium-rich solution to the storage tank Add it back into the original brine chamber, add 1L salt lake brine into the new brine chamber (original lithium salt chamber), and perform the second electrodialysis under the same conditions. After the second electrodialysis, the concentration of Li ⁺ in the brine chamber was reduced to 286.3 mg/L, and the concentration of Li ⁺ in the secondary lithium-rich solution obtained in the lithium salt chamber was 855.1 mg/L.

Example 5

Mix 2gLi ₄ Ti ₅ O ₁₂ , 0.25g acetylene black and 0.25g PVDF uniformly in a weight ratio of 8:1:1, add the mixed powder to N-methylpyrrolidone (NMP) organic solvent for grinding and slurrying, and The slurry was coated on graphite paper, and dried under vacuum at 120°C for 12 hours, and after cooling, a Li ₄ Ti ₅ O ₁₂ ion sieve composite membrane was obtained; the Li ₄ Ti ₅ O ₁₂ ion sieve membrane was placed in an electrodialysis device Add 1L of salt lake brine to the brine chamber in the middle of the tank. The composition and content of the brine are shown in the table below:

Place the graphite electrode in the lithium salt chamber of the electrodialysis device, add 500ml of 20g/L NaCl solution; use the graphite electrode as the anode, and the Li ₄ Ti ₅ O ₁₂ ion sieve as the cathode, apply a voltage of 0.8V between the two electrodes, After maintaining at 25°C for 10 hours, the concentration of Li ⁺ in the brine chamber decreased to 157.6 mg/L, the concentration of Mg ²⁺ basically remained unchanged, and the adsorption capacity of Li ⁺ on Li ₄ Ti ₅ O ₁₂ ion sieve was 21.2 mg/L g.

According to the same method in this example, 2 g of Li ₄ Ti ₅ O ₁₂ ion sieves were fabricated into ion sieve composite membranes without intercalation of lithium. After the initial lithium intercalation, place the non-intercalated Li ₄ Ti ₅ O ₁₂ composite membrane in the brine chamber, add 1L of salt lake brine, place the lithium intercalated ion sieve membrane in the lithium salt chamber, add 500mL of 20g/ L of NaCl solution, Li ₄ Ti ₅ O ₁₂ ion sieve in lithium-intercalated state is used as anode, Li ₄ Ti ₅ O ₁₂ ion sieve without lithium intercalation is used as cathode, and a voltage of 0.8V is applied between the electrodes. Maintain at ℃ for 10h. After the electrodialysis, the concentration of Li ⁺ in the brine chamber was reduced to 155.4mg/L, and the concentration of Li ⁺ in the lithium-rich solution obtained in the lithium salt chamber was 88.7mg/L.

Example 6

According to the weight ratio of 8:1:1, mix 4gLiFe _0.99 Mn _0.01 PO ₄ /C, 0.5g high-purity graphite and 0.5g PVDF evenly, add N-methylpyrrolidone (NMP) organic solvent and grind to make a slurry fluid. coated on graphite paper, heated to 110°C for 12 hours under vacuum conditions, and obtained a lithium iron phosphate composite film after cooling; the lithium iron phosphate composite film was used as the anode and the nickel foam was used as the cathode, and placed in a concentration of 1L In the NaCl solution of 30g/L, a voltage of 1.1V is applied across the electrodes for 10h, and the lithium iron phosphate composite membrane is transformed into an iron phosphate ion sieve;

According to the same method in this example, 4gLiFe _0.99 Mn _0.01 PO ₄ /C is made into a lithium iron phosphate composite membrane, and the lithium iron phosphate composite membrane is placed in the lithium salt chamber of the electrodialysis device, and 500ml of 30g/L NaCl solution is added The ferric phosphate ion sieve of gained is placed in the bittern chamber, adds 1L salt lake bittern, and the composition and content of bittern are shown in the following table:

With the lithium iron phosphate composite membrane as the anode and the iron phosphate ion sieve as the cathode, a voltage of 1.0V was applied at a pH of 8 and 25°C. After maintaining for 15 hours, the concentration of Li ⁺ in the brine chamber decreased to 66.5mg/L, Mg ² The concentration of ⁺ is 1257mg/L, and the concentration of Li ⁺ in the lithium salt chamber is 267.4mg/L.

Example 7

According to the weight ratio of 8:1:1, mix 2gLiFePO ₄ /C, 0.25g high-purity graphite and 0.25g PVDF evenly, add N-methylpyrrolidone (NMP) organic solvent to grind into a slurry fluid, and coat the slurry Place the carbon fiber cloth on the carbon fiber cloth, put it in a vacuum drying oven, heat it up to 110°C for 12 hours, and obtain a lithium iron phosphate composite film after cooling; use the lithium iron phosphate composite film as the anode and nickel foam as the cathode, and place it in 1L In a NaCl solution with a concentration of 20g/L, a voltage of 1.0V is applied across the electrodes for 12h, and the lithium iron phosphate composite membrane is transformed into an iron phosphate ion sieve;

According to the same method in this embodiment, 2gLiFePO ₄ /C is made into a lithium iron phosphate composite membrane, and the lithium iron phosphate composite membrane is placed in the lithium salt chamber of the electrodialysis device, and 1L of NaCl solution of 50g/L is added; The iron phosphate ion sieve is placed in the brine chamber, and 1L of salt lake brine is added. The composition and content of the brine are shown in the following table:

With the lithium iron phosphate composite membrane as the anode and the iron phosphate ion sieve as the cathode, a voltage of 1.0V was applied at a pH of 10 and 30°C. After maintaining for 12 hours, the concentration of Li ⁺ in the brine chamber decreased to 442.3mg/L, and the lithium salt The concentration of Li ⁺ in the chamber was 57.8 mg/L. After the end of the electrodialysis, the morphology of the lithium-intercalated ion sieve and the non-intercalated lithium-ion sieve are transformed into each other; the positions of the above two electrodes are exchanged, that is, the phosphoric acid obtained by converting the lithium iron phosphate composite membrane in the lithium salt chamber The iron ion sieve is placed in the brine chamber as the cathode, and the lithium-intercalated ion sieve obtained by converting the ferric phosphate ion sieve in the brine chamber is placed in the lithium salt chamber as the anode, and electrodialysis is carried out under the same conditions; after the electrodialysis is completed, The concentration of Li ⁺ in the brine compartment became 384.6 mg/L, and the concentration of Li ⁺ in the lithium salt compartment increased to 115.7 mg/L.

Several cycles were carried out in this way. After the sixth electrodialysis, the concentration of Li ⁺ in the brine chamber became 153.5 mg/L, and the concentration of Li ⁺ in the lithium salt chamber increased to 346.8 mg/L.

Claims (10)

1. a salt lake brine magnesium lithium separates and the method for enriching lithium, it is characterized in that, in turn includes the following steps:

(1) with anion-exchange membrane the electrodialysis cell of electrodialysis unit vertically is separated into two zones in lithium salts chamber and bittern chamber, the indoor salt lake brine that charges into of bittern, indoor the charging into of lithium salts do not contain Mg ²⁺Supporting electrolyte solution;

The conducting base that (2) will be coated with ion(ic)sieve places the bittern chamber as negative electrode; Place the lithium salts chamber as anode the conducting base that is coated with embedding lithium attitude ion(ic)sieve, under the driving of electromotive force, make the Li in the bittern of bittern chamber outside ⁺Be embedded into formation embedding lithium attitude ion(ic)sieve in the ion(ic)sieve, the embedding lithium attitude ion(ic)sieve in the lithium salts chamber is with Li simultaneously ⁺After being discharged into conductive soln, revert to ion(ic)sieve; Realize the Li in the bittern chamber ⁺With Mg ²⁺And other cationic separation, lithium enrichment in the lithium salts chamber obtains rich lithium solution simultaneously.

2. the method for claim 1 is characterized in that,

After step (2) is accomplished, carry out once following operation at least:

Liquid behind the embedding lithium in the bittern chamber is discharged, add salt lake brine again, then negative electrode and anode exchange are placed, proceed electrodialysis.

3. the method for claim 1 is characterized in that,

After step (2) is accomplished, carry out once following operation at least:

Holding anode and negative electrode stationkeeping are discharged liquid behind the embedding lithium in the bittern chamber, and the lithium-containing solution in the lithium salts chamber is transferred in the bittern chamber, and new salt lake brine is joined in the lithium salts chamber; Be about to bittern chamber and lithium salts chamber transition function and use, proceed electrodialysis.

4. like claim 1 or 2 or 3 described methods, it is characterized in that described salt lake brine comprises and contains Li arbitrarily ⁺Solution, arbitrarily original bittern and the bittern after the evaporation concentration thereof in the salt lake and carry potassium after the old halogen of evaporation in one or more.

5. the method for claim 1 is characterized in that, the described conducting base of step (2) is to be coated with a kind of in ruthenium titanium net, graphite cake, Pt family metal and Alloy Foil thereof, carbon cloth, the graphite paper.

6. like claim 1 or 2 or 3 described methods, it is characterized in that the temperature of solution is 0～80 ℃ in the electrodialysis unit, the pH value is 2～12; Two interelectrode voltage ranges are 0.5～2.0V in the electrodialysis unit.

7. like claim 1 or 2 or 3 described methods, it is characterized in that described ion(ic)sieve is tertiary iron phosphate, lithium titanate, MnO ₂In one or more mixture.

8. method as claimed in claim 7 is characterized in that, described tertiary iron phosphate is Fe _1-xMe _xPO ₄, wherein Me is one or more the mixing among Mn, Co, Mo, Ti, Al, Ni, the Nb, the scope of x is: 0≤x≤0.1; Lithium titanate is Li ₄Ti ₅O ₁₂, Li _xMe _yTi ₅O ₁₂, Li ₄Me _mTi _nO ₁₂In one or more mixture; Me is one or more the mixing among V, Fe, Co, Mn, Al, Ba, Ag, Zr, Sr, Nb, the F; 0＜x＜4,0＜y＜4,0＜m＜5,0＜n＜5.

9. the method for claim 1 is characterized in that, described embedding lithium attitude ion(ic)sieve directly adopts iron lithium phosphate or LiMn ₂O ₄In a kind of; Described iron lithium phosphate is LiFePO ₄, Li _xMe _yFePO ₄, LiFe _xMe _yPO ₄, LiFePO ₄/ C, Li _xMe _yFePO ₄/ C, LiFe _xMe _yPO ₄The mixture of one or more the among/C, wherein Me is one or more the mixing among Mn, Co, Mo, Ti, Al, Ni, the Nb, 0＜x＜1,0＜y＜1;

Perhaps obtain through following process: with anion-exchange membrane electrodialysis unit is divided into two zones in lithium salts chamber and bittern chamber, the indoor salt lake brine that charges into of bittern, indoor the charging into of lithium salts do not contain Mg ²⁺Supporting electrolyte solution; Will be to Li ⁺Selective adsorbing ion(ic)sieve is coated on the conducting base, places the bittern chamber of electrodialysis unit, is negative electrode with the ion(ic)sieve, is that counter electrode carries out cathodic polarization with the noble electrode, makes the Li in the bittern ⁺Be embedded into and obtain embedding lithium attitude ion(ic)sieve in the ion(ic)sieve.

10. the described salt lake brine magnesium of claim 1 lithium separates and the corollary apparatus of the method for enriching lithium; It is characterized in that; Comprise and have the electrodialysis unit that is separated into two spatial electrodialysis cells by anion-exchange membrane; And negative electrode and anode, described negative electrode and anode are arranged at respectively in two spaces that are divided into; Described negative electrode is the conducting base that is coated with ion(ic)sieve, and anode is the conducting base that is coated with embedding lithium attitude ion(ic)sieve.

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