Two-dimensional montmorillonite modified film for extracting lithium from salt lake original brine as well as preparation method and application of two-dimensional montmorillonite modified film

Abstract

The invention belongs to the technical field of membrane separation and also belongs to the field of lithium extraction, and particularly relates to a two-dimensional montmorillonite modified thin film for extracting lithium from salt lake original brine as well as a preparation method and application of the two-dimensional montmorillonite modified thin film. The two-dimensional montmorillonite modified film for extracting the lithium from the salt lake original halide is obtained by sequentially modifying a two-dimensional montmorillonite functional film with metal ions and crosslinking and modifying an organic matter containing polyphenol hydroxyl groups, the two-dimensional montmorillonite functional film is obtained by self-assembling a two-dimensional montmorillonite nanosheet functional suspension liquid modified by a short-chain organic cross-linking agent containing an amino group into a film. The separation performance of the film under the salt lake raw brine condition can be enhanced, the lithium extraction period is shortened, and the application advantage is remarkable.

Description

Technical Field

[0001] The present invention belongs to the field of membrane separation technology and also to the field of lithium extraction, and specifically relates to a two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, a preparation method and an application thereof. Background Art

[0002] Lithium is an important strategic mineral resource and a key resource for the new energy revolution. 80% of my country's lithium resources are stored in salt lake brine, and lithium extraction from salt lakes is an important way to supply lithium resources. Membrane separation is the mainstream process for extracting lithium from salt lake brine. Among them, two-dimensional channel membranes are widely used in the efficient separation of lithium resources in salt lake brine due to their high sub-nanometer precision control characteristics of the channel.

[0003] However, existing thin films focus on extracting lithium from old brine in salt lakes (i.e., first forming old brine by drying brine, extracting potassium, etc., and then extracting lithium after lithium is enriched). The old brine in salt lakes needs to be obtained by drying and evaporating in salt pans, which leads to a long lithium extraction cycle and a high lithium loss rate. By eliminating the process of evaporating the original brine in salt lakes and directly extracting lithium from the original brine before extracting lithium from the old brine, not only can the lithium extraction cycle be greatly shortened, but also the lithium recovery rate can be doubled. However, existing lithium extraction thin films are difficult to adapt to the brine characteristics of low lithium ion concentration of original brine in salt lakes. On the one hand, the low lithium ion concentration leads to insufficient power for lithium ion transmission and low lithium ion transmission rate; on the other hand, under low lithium ion concentration conditions, it is difficult to highly selectively transmit and separate lithium ions. Summary of the invention

[0004] The purpose of the present invention is to provide a two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes and its application. The two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes provided by the present invention stabilizes the channel height of the film by metal ions with strong electrostatic binding, thereby ensuring that lithium ions have a highly selective transmission ability. At the same time, the hydrophilicity of polyphenol hydroxyl groups and the function of specific lithium ion recognition are utilized to enhance the lithium ion transmission power, thereby realizing efficient lithium extraction from raw brine in salt lakes with low lithium ion concentration.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention provides a two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, which is obtained by sequentially modifying a two-dimensional montmorillonite functional film with metal ions and cross-linking with an organic compound containing polyphenol hydroxyl groups. The two-dimensional montmorillonite functional film is obtained by self-assembly of a two-dimensional montmorillonite nanosheet functional suspension modified with a short-chain organic cross-linking agent containing an amino group.

[0007] According to the above scheme, the short-chain organic crosslinking agent containing an amino group is any one of ethyl carbamate, aminoacetic acid, tetraethylenepentamine, triethylenediamine, and aminosulfonic acid, or a combination of at least two thereof.

[0008] According to the above scheme, the thickness of the two-dimensional montmorillonite functional film is 50-2000 μm.

[0009] According to the above scheme, the metal ion is Al 3+ , Fe 3+ , Ca 2+ , Cu 2+ 、Zn 2+ , Mn 2+ Any of;

[0010] According to the above scheme, the polyphenolic hydroxy organic matter is any one of tannic acid, hydroxytyrosol, 3,4,5-trihydroxybenzoic acid, catechin, and lignan, or a combination of at least two of them.

[0011] According to the above scheme, the metal ion modification is as follows: immersing the two-dimensional montmorillonite functional film obtained by self-assembly into an aqueous solution containing metal ions for modification, and washing with water to obtain the metal ion-modified two-dimensional montmorillonite functional film;

[0012] The cross-linking modification of the polyphenolic hydroxyl organic matter comprises: immersing the metal ion-modified two-dimensional montmorillonite functional film in a solution containing polyphenolic hydroxyl organic matter for immersion cross-linking, washing and drying to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0013] According to the above scheme, in the metal ion modification: the concentration of the metal ion aqueous solution is 1-200 g / L, and the modification treatment time is 1-60 min.

[0014] The concentration of the polyphenol hydroxy organic matter in the cross-linking modification of the polyphenol hydroxy organic matter is 0.1-20wt%, and the cross-linking time is 1-80min.

[0015] The second aspect of the present invention provides a method for preparing the above-mentioned two-dimensional montmorillonite modified film for extracting lithium from raw halogen in salt lakes, and the specific steps are as follows:

[0016] (1) adding two-dimensional montmorillonite nanosheets and a short-chain organic crosslinking agent containing an amino group into water for stirring and reacting to obtain a two-dimensional montmorillonite nanosheet functional suspension;

[0017] (2) self-assembling a two-dimensional montmorillonite nanosheet functional suspension on a base film to form a film, and the film naturally falls off from the base film after drying, thereby obtaining a two-dimensional montmorillonite functional film;

[0018] (3) immersing the two-dimensional montmorillonite functional film in an aqueous solution containing metal ions for modification, and washing with water to obtain a two-dimensional montmorillonite functional film modified with metal ions;

[0019] (4) Immersing the metal ion-modified two-dimensional montmorillonite functional film in a solution containing polyphenolic hydroxyl organic matter for immersion crosslinking, washing with water and drying to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0020] Preferably, in step (1), the average sheet diameter of the two-dimensional montmorillonite nanosheets is 100-1000 nm, the average sheet thickness is 1-10 nm, and the concentration of the two-dimensional montmorillonite nanosheets in the two-dimensional montmorillonite nanosheet functional suspension is 0.5-3.5 wt %.

[0021] Preferably, in step (1), the short-chain organic crosslinking agent containing an amino group is any one of ethyl carbamate, aminoacetic acid, tetraethylenepentamine, triethylenediamine, and aminosulfonic acid, or a combination of at least two thereof; and the amount used is 0.5%-30% of the two-dimensional montmorillonite nanosheets.

[0022] Preferably, in step (1), the stirring reaction time is 0.1-3h.

[0023] Preferably, in step (2), the material of the base film is one of polyvinylidene fluoride, polypropylene, polytetrafluoroethylene, and polyethylene terephthalate.

[0024] Preferably, in step (2), the self-assembly film forming method is one of blade coating, spin coating and spray coating.

[0025] Preferably, in step (2), the drying temperature is 15-100° C. and the drying time is 0.1-12 h.

[0026] Preferably, in step (2), the thickness of the two-dimensional montmorillonite functional film is 50-2000 μm.

[0027] Preferably, in step (3), the metal ion is Al 3+ , Fe 3+ , Ca 2+ , Cu 2+ 、Zn 2+ , Mn 2+ Any one of the above, the concentration of the metal ion aqueous solution is 1-200g / L, and the modification treatment time is 1-60min.

[0028] Preferably, in step (4), the polyphenolic hydroxy organic matter is any one of tannic acid, hydroxytyrosol, 3,4,5-trihydroxybenzoic acid, catechin, lignan or a combination of at least two thereof, with a concentration of 0.1-20 wt % and a cross-linking time of 1-80 min.

[0029] A third aspect of the present invention provides the use of a two-dimensional montmorillonite modified film for extracting lithium from raw brine from salt lakes as a functional membrane for extracting lithium from raw brine from salt lakes.

[0030] According to the above scheme, the application is: using the two-dimensional montmorillonite modified film for extracting lithium from salt lake halogen as a nanofiltration membrane for a pressure-driven nanofiltration membrane system or as an electrodialysis membrane for an electric-driven electrodialysis membrane system to extract lithium from salt lake halogen.

[0031] The present invention solves the problem of lithium extraction under the condition of low lithium ion concentration of raw halogen in salt lake by strengthening the lithium ion transmission ability and channel height stability of the film to reduce the influence of impurity ion competition transmission, and realizes lithium extraction from raw halogen. The working principle of the present invention is: the end face of the two-dimensional montmorillonite nanosheet used in the present invention has rich aluminum hydroxyl groups. First, short-chain organic matter with amine groups is used to perform functional self-assembly with montmorillonite nanosheets. The hydrogen bonding between the amine groups of the short-chain organic matter and the aluminum hydroxyl groups of the end faces of the nanosheets induces the end faces of the nanosheets to cross-link with the end faces. The montmorillonite nanosheets after the end faces are connected into large pieces are easier to assemble into films in an orderly manner. At the same time, the short-chain organic matter can avoid the interlayer channel sites of the film from being occupied. Further, by utilizing the interlayer cation exchange characteristics unique to montmorillonite, metal cations with strong electrostatic binding force and strong electrostatic interaction with montmorillonite can be exchanged between the two-dimensional montmorillonite film layers to stabilize the film channel height. At the same time, the introduction of metal cations can provide cross-linking sites for further introducing functional organic matter into the film. On this basis, organic matter containing polyphenolic hydroxyl groups is used to cross-link the two-dimensional montmorillonite film modified with metal cations. On the one hand, the chelation of polyphenolic hydroxyl groups with metal cations can form a functional layer with polyphenolic hydroxyl groups on the surface of the two-dimensional montmorillonite film. The polyphenolic hydroxyl groups are highly hydrophilic, and the polyphenolic hydroxyl groups have a relatively strong affinity for lithium ions. They have a specific recognition effect on lithium ions, which can effectively improve the transmission power of lithium ions under low lithium ion concentration conditions and increase the lithium ion transmission rate. On the other hand, the chelation functional layer of polyphenolic hydroxyl groups with metal cations can avoid the loss of metal cations used to stabilize the height of the film channel during the lithium ion separation process, further strengthen the stability of the film channel height, and achieve highly selective transmission of lithium ions, thereby ultimately achieving efficient lithium extraction from raw halogen under low lithium ion concentration conditions.

[0032] Compared with the prior art, the beneficial effects of the present invention include:

[0033] 1. The present invention can enhance the lithium ion transmission rate and separation selectivity of low lithium ion concentration raw brine, realize direct lithium extraction from salt lake raw brine, and can shorten the lithium extraction cycle and improve the lithium ion recovery rate compared with lithium extraction from salt lake old brine;

[0034] 2. By utilizing the unique cation exchange properties of montmorillonite and introducing metal cations with strong binding force between the film layers, the binding force between the nanosheets can be strengthened and the channel height of the film can be stabilized, so that the film can exhibit highly selective separation performance in the original halogen system;

[0035] 3. The polyphenolic hydroxyl and metal cation chelating functional layer constructed by the film system can further fix the metal cations between the layers, ensuring that the strong binding force cations introduced between the film layers operate stably and do not leak out of the layer during the separation process in the original halogen environment, thereby enhancing the stability of the film operation;

[0036] 4. The polyphenolic hydroxyl groups introduced into the film system are highly hydrophilic and have a recognition effect on lithium ions. Under the original halide conditions with low lithium ion concentration, they can enhance the lithium ion transmission rate and enhance the lithium-magnesium separation selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the SEM image of the film obtained in Example 1.

[0038] Figure 2 These are the test results of the lithium-magnesium transmission rate and separation selectivity of the film obtained in Example 1.

[0039] Figure 3 The test results of separation selectivity of the membrane obtained in Example 1 after 50 hours of cycle operation are shown in FIG. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Example 1

[0042] A two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, the preparation method of which comprises the following steps:

[0043] (1) stirring two-dimensional montmorillonite nanosheets having an average sheet size of 100 nm and an average sheet thickness of 1 nm and 0.5 wt % of ethyl carbamate in water for 0.1 h to react to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 0.5 wt %;

[0044] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polyvinylidene fluoride base film by spraying, and the film was naturally detached from the base film after being dried at 15° C. for 12 h, thereby obtaining a two-dimensional montmorillonite functional film with a thickness of 50 μm;

[0045] (3) The two-dimensional montmorillonite functional film is placed in a Fe 3+ Modified in aqueous solution for 60 min, and washed with water to obtain Fe 3+ Modified two-dimensional montmorillonite functional film;

[0046] (4) the Fe3+ The modified two-dimensional montmorillonite functional film is immersed in a tannic acid aqueous solution with a concentration of 0.1 wt% for cross-linking for 80 minutes, and then washed and dried to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0047] Figure 1 The two-dimensional montmorillonite modified film prepared in this embodiment shows that the nanosheets in the cross section of the film are in an orderly stacked state, which lays a foundation for the separation and extraction of lithium ions in the raw brine of the salt lake.

[0048] Figure 2 and Figure 3 A control experiment was set up to prove that the method of the present invention can effectively improve the separation performance of the membrane in the raw brine environment of the salt lake, wherein: Figure 2 The prepared two-dimensional montmorillonite modified film is placed in an ion separation device, the content of each ion after the salt lake brine passes through the film is detected, and the ion transmission rate and separation selectivity are calculated. Figure 3 The experiment was Figure 2 The cyclic stability of membrane separation performance was tested by repeatedly replacing the raw brine of the salt lake based on the operation. The results showed that the lithium ion transfer rate of the control membrane (MMTM) in the raw brine environment of the salt lake was 0.06 mol·m -2 h -1 , the lithium-magnesium separation selectivity is 4, and for the film obtained in this example (TA / Fe-MMTM), the lithium ion transmission rate can be increased to 0.12 mol·m -2 h -1 , the lithium-magnesium separation selectivity can be increased to 12. At the same time, the separation selectivity of the film obtained in this embodiment is always maintained at about 12 in the long-term cycle, which has good stability and is conducive to practical application. In addition, the film prepared in this embodiment has strong flexibility and does not break when bent 180°.

[0049] The preparation method of the control group film (MMTM) includes the following steps:

[0050] (1) stirring two-dimensional montmorillonite nanosheets having an average sheet size of 100 nm and an average sheet thickness of 1 nm and 0.5 wt % of ethyl carbamate in water for 0.1 h to react to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 0.5 wt %;

[0051] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polyvinylidene fluoride base film by spraying. The film was dried at 15°C for 12 hours and then naturally fell off the base film to obtain a two-dimensional montmorillonite functional film with a thickness of 50 μm (control group film).

[0052] The Fe-MMTM preparation method comprises the following steps:

[0053] (1) stirring two-dimensional montmorillonite nanosheets having an average sheet size of 100 nm and an average sheet thickness of 1 nm and 0.5 wt % of ethyl carbamate in water for 0.1 h to react to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 0.5 wt %;

[0054] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polyvinylidene fluoride base film by spraying, and the film was naturally detached from the base film after being dried at 15° C. for 12 h, thereby obtaining a two-dimensional montmorillonite functional film with a thickness of 50 μm;

[0055] (3) The two-dimensional montmorillonite functional film is placed in a Fe 3+ Modified in aqueous solution for 60 min, and washed with water to obtain Fe 3+ Modified two-dimensional montmorillonite functional film (Fe-MMTM).

[0056] Example 2

[0057] A two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, the preparation method of which comprises the following steps:

[0058] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet diameter of 1000 nm and an average sheet thickness of 10 nm with aminoacetic acid accounting for 30 wt % of the amount of the nanosheets in water under stirring for 3 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 3.5 wt %;

[0059] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polyethylene terephthalate substrate by a doctor blade coating method. The film was dried at 100° C. for 0.1 h and then naturally fell off the substrate to obtain a two-dimensional montmorillonite functional film with a thickness of 2000 μm.

[0060] (3) The two-dimensional montmorillonite functional film is placed in an Al2O3 solution with a concentration of 200 g / L. 3+ Modified in aqueous solution for 1 min, washed with water to obtain Al 3+ Modified two-dimensional montmorillonite functional film;

[0061] (4) The Al 3+ The modified two-dimensional montmorillonite functional film is immersed in a 20wt% lignan aqueous solution for cross-linking for 1 minute, and then washed and dried to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0062] Compared with the control group film, the lithium ion transfer rate of the film prepared in this example in the original brine environment of the salt lake is increased from 0.05 mol·m -2 h -1 Increased to 0.10 mol·m -2 h -1 The lithium-magnesium separation selectivity was improved from 3.2 to 9.8, and the long-term cycle stability of the film was always maintained above 9.5.

[0063] The preparation method of the control group film (MMTM) includes the following steps:

[0064] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet diameter of 1000 nm and an average sheet thickness of 10 nm with aminoacetic acid accounting for 30 wt % of the amount of the nanosheets in water under stirring for 3 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 3.5 wt %;

[0065] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polyethylene terephthalate base film by a scraping method. The film was dried at 100°C for 0.1 h and then naturally fell off the base film to obtain a two-dimensional montmorillonite functional film with a thickness of 2000 μm (control group film).

[0066] Example 3

[0067] A two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, the preparation method of which comprises the following steps:

[0068] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet size of 500 nm and an average sheet thickness of 5 nm with tetraethylenepentamine accounting for 15 wt % of the amount of the nanosheets in water under stirring for 1.5 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 2 wt %;

[0069] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polypropylene base film by spin coating. The film was dried at 55°C for 2 hours and then naturally fell off the base film to obtain a two-dimensional montmorillonite functional film with a thickness of 1000 μm.

[0070] (3) The two-dimensional montmorillonite functional film is placed in a Cu solution with a concentration of 100 g / L. 2+ Modified in aqueous solution for 30 min, washed with water to obtain Cu 2+ Modified two-dimensional montmorillonite functional film;

[0071] (4) The Cu 2+The modified two-dimensional montmorillonite functional film is immersed in a 10 wt % hydroxytyrosol aqueous solution for cross-linking for 40 minutes, and then washed and dried to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0072] Compared with the control group film, the lithium ion transfer rate of the film prepared in this example in the original brine environment of the salt lake is increased from 0.065 mol·m -2 h -1 Increased to 0.11 mol·m -2 h -1 The lithium-magnesium separation selectivity was increased from 5.3 to 10.5, and the long-term cycle stability of the film was always maintained above 10.

[0073] The preparation method of the control group film (MMTM) includes the following steps:

[0074] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet size of 500 nm and an average sheet thickness of 5 nm with tetraethylenepentamine accounting for 15 wt % of the amount of the nanosheets in water under stirring for 1.5 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 2 wt %;

[0075] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polypropylene base film by spin coating. The film was dried at 55°C for 2 hours and then naturally fell off the base film to obtain a two-dimensional montmorillonite functional film with a thickness of 1000 μm (control group film).

[0076] Example 4

[0077] A two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, the preparation method of which comprises the following steps:

[0078] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet diameter of 200 nm and an average sheet thickness of 3 nm with triethylenediamine accounting for 5 wt % of the amount of the nanosheets in water under stirring for 2 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 1 wt %;

[0079] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled on a polytetrafluoroethylene substrate by spraying, and the film was naturally detached from the substrate after being dried at 30° C. for 6 h, thereby obtaining a two-dimensional montmorillonite functional film with a thickness of 500 μm;

[0080] (3) The two-dimensional montmorillonite functional film is placed in a Zn solution with a concentration of 50 g / L 2+ Modified in aqueous solution for 40 min, washed with water to obtain Zn 2+ Modified two-dimensional montmorillonite functional film;

[0081] (4) The Zn 2+ The modified two-dimensional montmorillonite functional film is immersed in a catechin aqueous solution with a concentration of 15 wt% for cross-linking for 30 minutes, and then washed and dried to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

[0082] Compared with the control group film, the lithium ion transfer rate of the film prepared in this example in the original brine environment of the salt lake is increased from 0.03 mol·m -2 h -1 Increased to 0.14 mol·m -2 h -1 The lithium-magnesium separation selectivity was improved from 4.7 to 13.2, and the long-term cycle stability of the film always remained above 13.

[0083] The preparation method of the control group film (MMTM) includes the following steps:

[0084] (1) reacting two-dimensional montmorillonite nanosheets having an average sheet diameter of 200 nm and an average sheet thickness of 3 nm with triethylenediamine accounting for 5 wt % of the amount of the nanosheets in water under stirring for 2 h to obtain a two-dimensional montmorillonite nanosheet functional suspension, wherein the concentration of the two-dimensional montmorillonite nanosheets is 1 wt %;

[0085] (2) The two-dimensional montmorillonite nanosheet functional suspension was self-assembled into a film on a polytetrafluoroethylene base film by spraying. The film was dried at 30°C for 6 hours and then naturally fell off from the base film to obtain a two-dimensional montmorillonite functional film with a thickness of 500 μm (control group film).

[0086] The present invention is not limited to the above-mentioned embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A two-dimensional montmorillonite modified film for extracting lithium from raw brine in salt lakes, characterized in that: The two-dimensional montmorillonite functional film is obtained by sequentially modifying with metal ions and cross-linking with polyphenolic hydroxyl organic matter. The two-dimensional montmorillonite functional film is obtained by self-assembly of a two-dimensional montmorillonite nanosheet functional suspension modified with a short-chain organic cross-linking agent containing amino groups.

2. The two-dimensional montmorillonite modified film according to claim 1, characterized in that: The short-chain organic crosslinking agent containing an amino group is any one of ethyl carbamate, aminoacetic acid, tetraethylenepentamine, triethylenediamine, and aminosulfonic acid, or a combination of at least two of them.

3. The two-dimensional montmorillonite modified film according to claim 1, characterized in that: The thickness of the two-dimensional montmorillonite functional film is 50-2000 μm.

4. The two-dimensional montmorillonite modified film according to claim 1, characterized in that: The metal ion is Al 3+ , Fe 3+ , Ca 2 + , Cu 2+ 、Zn 2+ , Mn 2+ Any of; The polyphenolic hydroxy organic matter is any one of tannic acid, hydroxytyrosol, 3,4,5-trihydroxybenzoic acid, catechin, and lignan, or a combination of at least two of them.

5. The two-dimensional montmorillonite modified film according to claim 1, characterized in that: The metal ion modification is as follows: immersing the two-dimensional montmorillonite functional film obtained by self-assembly into an aqueous solution containing metal ions for modification, and washing with water to obtain the metal ion-modified two-dimensional montmorillonite functional film; The cross-linking modification of the polyphenolic hydroxyl organic matter comprises: immersing the metal ion-modified two-dimensional montmorillonite functional film in a solution containing polyphenolic hydroxyl organic matter for immersion cross-linking, washing and drying to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

6. The two-dimensional montmorillonite modified film according to claim 5, characterized in that: In metal ion modification: the concentration of the metal ion aqueous solution is 1-200 g / L, and the modification treatment time is 1-60 min; The concentration of the polyphenol hydroxy organic matter in the cross-linking modification of the polyphenol hydroxy organic matter is 0.1-20wt%, and the cross-linking time is 1-80min.

7. A method for preparing a two-dimensional montmorillonite modified film for extracting lithium from raw halogen in salt lakes according to claim 1, characterized in that: The specific steps are as follows: (1) adding two-dimensional montmorillonite nanosheets and a short-chain organic crosslinking agent containing an amino group into water for stirring and reacting to obtain a two-dimensional montmorillonite nanosheet functional suspension; (2) self-assembling a two-dimensional montmorillonite nanosheet functional suspension on a base film to form a film, and the film naturally falls off from the base film after drying, thereby obtaining a two-dimensional montmorillonite functional film; (3) immersing the two-dimensional montmorillonite functional film in an aqueous solution containing metal ions for modification, and washing with water to obtain a two-dimensional montmorillonite functional film modified with metal ions; (4) Immersing the metal ion-modified two-dimensional montmorillonite functional film in a solution containing polyphenolic hydroxyl organic matter for immersion crosslinking, washing with water and drying to obtain a two-dimensional montmorillonite modified film for raw halogen lithium extraction.

8. The preparation method according to claim 7, characterized in that: In the step (1), the average sheet diameter of the two-dimensional montmorillonite nanosheets is 100-1000 nm, the average sheet thickness is 1-10 nm, and the concentration of the two-dimensional montmorillonite nanosheets in the two-dimensional montmorillonite nanosheet functional suspension is 0.5-3.5 wt %; In the step (1), the amount of the short-chain organic crosslinking agent containing an amino group is 0.5% to 30% of the two-dimensional montmorillonite nanosheets; In the step (1), the stirring reaction time is 0.1-3h; In the step (2), the self-assembly film forming method is one of blade coating, spin coating and spray coating; the drying temperature is 15-100° C., and the drying time is 0.1-12 h; In the step (2), the material of the base film is one of polyvinylidene fluoride, polypropylene, polytetrafluoroethylene, and polyethylene terephthalate.

9. Application of the two-dimensional montmorillonite modified film for extracting lithium from raw halogen in salt lakes as claimed in any one of claims 1 to 6 as a functional membrane for extracting lithium from raw halogen in salt lakes.

10. The use according to claim 9, characterized in that: The two-dimensional montmorillonite modified film for extracting lithium from salt lake brine is used as a nanofiltration membrane for a pressure-driven nanofiltration membrane system or as an electrodialysis membrane for an electric-driven electrodialysis membrane system to extract lithium from salt lake brine.

Images