Preparation method and application of graphene oxide permeable membrane suitable for concentrated salt brine system

Abstract

The invention discloses a preparation method and application of a graphene oxide permeable membrane suitable for a concentrated salt brine system, and relates to the technical field of organic matter removal and desalinization. According to the method, polyether sulfone serves as a basement membrane, carboxylated graphene oxide and sodium alginate are subjected to cross-linking construction, and a graphene oxide / sodium alginate composite membrane is prepared; and then the graphene oxide permeable membrane is immersed in an alkali metal Sr < 2 + > solution and transition metal Fe < 2 + > and Fe < 3 + > solutions in sequence, and the graphene oxide permeable membrane is prepared. The prepared permeable membrane material can realize efficient interception of various soluble organic matters in a salt lake brine system, shows excellent desalting performance, and has a good application prospect in the field of salt lake brine treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic matter removal and desalination, and particularly relates to a preparation method and application of a graphene oxide permeation membrane suitable for a concentrated salt brine system. BACKGROUND

[0002] The solvent extraction method is a high-efficiency lithium extraction method for salt lakes, and has the advantages of simple operation, low cost, high efficiency and the like, and has been implemented in industrial application in Dachaidan and Xitaijinal salt lakes. However, in the lithium extraction process of the salt lake, there are often problems such as loss of the extractant, incomplete recovery and decomposition of organic by-products, which result in the residual of various dissolved organic matters in the concentrated salt brine. If not properly treated, the residual organic matters not only reduce the production efficiency of lithium products and affect the quality of lithium products, but also threaten the ecological environment of the salt lake, so that the wide popularization of the extraction technology in the salt lake area is greatly limited. The traditional industrial methods for treating the dissolved organic matters in the concentrated salt system mainly include gravity separation, advanced oxidation, solvent extraction and micro-electrolysis, however, the complex operation process, residual organic matters, high cost and low efficiency greatly limit the practical application. As a two-dimensional nanomaterial, graphene oxide has a large specific surface area, rich chemical functional groups, strong processability, high efficiency and energy saving, and has a good application prospect in the fields of wastewater treatment and seawater desalination, and is expected to realize efficient interception of residual organic matters and salt ions in the salt lake brine. However, the permeation flux of a single graphene oxide-based membrane is only 1.721 L·m -2 ·h -1 , and the swelling effect of the graphene oxide surface results in poor stability of the membrane structure and greatly reduced organic matter separation performance.

[0003] At present, various efficient modified graphene oxide (GO) membrane methods have been developed and reported, but still have certain limitations. The physical constraint method can effectively delay the swelling of the GO interlayer structure to improve the stability of the membrane, but the complex preparation process limits its large-scale production; the chemical reduction method can inhibit the swelling effect of the GO in water by reducing the surface oxygen-containing groups, but the hydrophilicity of the membrane is greatly reduced; the organic polymer or molecule as a crosslinking agent can react / interact with adjacent GO nanosheets to form stable covalent bonds to improve the stability of the GO membrane, but the crosslinking agent with large steric hindrance may occupy the inherent free volume between the GO membrane layers, resulting in a decrease in the permeation flux, and the introduction of hydrophobic alkyl chains or aromatic groups and the large consumption of oxygen-containing groups will also reduce the hydrophilicity of the membrane surface; the metal ion intercalation method can inhibit the swelling effect of the GO membrane through the electrostatic attraction and cation-π interaction with the oxygen-containing functional groups on the GO surface, however, the inherent hydration characteristics of the metal ions will inevitably weaken the interaction with the GO, thereby destroying the membrane structure and reducing the interception performance of the membrane.

[0004] Although various modified GO composite membranes have significantly improved stability and surface hydrophilicity, they are still limited to salt lake brine systems. The main reasons are as follows: first, the swelling effect leads to weakened stability and reduced separation performance of the membrane; second, the complex ion and molecular environment seriously deforms the GO nanochannel induced by anisotropy, resulting in insufficient long-term operation stability and reduced separation performance; third, the deposition of organic matter and inorganic salt on the membrane surface and inside the membrane causes serious membrane pollution and low permeation flux. Therefore, it is necessary to design a graphene oxide permeation membrane suitable for concentrated salt brine system to solve the problem that the GO membrane is limited to the salt lake brine system and improve the organic matter removal and salt ion rejection efficiency. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a graphene oxide permeation membrane suitable for a concentrated salt brine system to solve the problem of low organic matter removal and salt ion rejection efficiency in the prior art applied to the salt lake brine system.

[0006] The present application first provides a preparation method of a graphene oxide permeation membrane suitable for a concentrated salt brine system, which comprises the following steps:

[0007] S1, preparing a carboxylated graphene oxide and sodium alginate (SA) mixed solution;

[0008] S2, pumping the carboxylated graphene oxide and sodium alginate mixed solution to a polyether sulfone (PES) base membrane for filtration and drying, so that the carboxylated graphene oxide and sodium alginate are loaded on the surface of the polyether sulfone base membrane to prepare a graphene oxide / sodium alginate composite membrane;

[0009] S3, immersing the graphene oxide / sodium alginate composite membrane in a strontium ion (Sr 2+ ) solution to prepare a graphene oxide / sodium alginate-strontium composite membrane;

[0010] S4, immersing the graphene oxide / sodium alginate-strontium composite membrane in an iron ion solution to prepare the graphene oxide permeation membrane suitable for the concentrated salt brine system.

[0011] Preferably, in the step S1, the mass ratio of carboxylated graphene oxide to sodium alginate is 0.4-1.6.

[0012] Preferably, in the step S1, the carboxylated graphene oxide and sodium alginate mixed solution is uniformly mixed at a heating temperature of 25-80 DEG C and a stirring time of 2-16 h.

[0013] Preferably, in the step S2, the drying temperature is 25-60 DEG C.

[0014] Preferably, in the step S3, the concentration of strontium ions is 0.01-0.1 mol / L.-1 ~ 2.0 mol·L -1 .

[0015] Preferably, in the step S3, the time of immersing in the strontium ion solution is 2h-16h.

[0016] Preferably, in the step S4, the iron ion solution includes Fe 3+ , Fe 2+ , Fe 3+ content is 0-1 mol·L -1 , Fe 3+ , Fe 2+ content ratio is 10-100:1.

[0017] Preferably, in the step S4, the time of immersing in the iron ion mixed solution is 2h-16h.

[0018] The application further provides an oxidized graphene permeable membrane suitable for a concentrated salt brine system, which is prepared by the preparation method.

[0019] The application further provides an application of the oxidized graphene permeable membrane suitable for a concentrated salt brine system, which is used for efficient interception of organic matters and desalination in a salt lake brine.

[0020] The application discloses an oxidized graphene permeable membrane suitable for a concentrated salt brine system, which is prepared by cross-linking construction of a GO / SA composite membrane through high-hydrophilic natural hydrogel sodium alginate (SA) and carboxylated GO nanosheets with polyether sulfone as a base film. The introduction of the sodium alginate not only effectively regulates the surface performance of the membrane, endows the membrane with super-hydrophilicity and anti-pollution, but also provides more binding sites for subsequent metal ion intercalation. By utilizing the different coordination abilities of alkali metal Sr 2+ and transition metal Fe 2+ , Fe 3+ , Sr 2+ is preferentially intercalated and introduced, a GO / SA-Sr composite membrane is constructed, and then Fe 2+ , Fe 3+ are introduced. By virtue of the different coordination sites and ligand structures of active groups on the GO and SA, the microstructure of the membrane is optimized, a complete and stable GO nanochannel without defects is constructed, the permeation flux of the membrane is greatly improved while the separation performance of the membrane is ensured, and the problem that the traditional membrane material is difficult to balance between the permeation flux and the separation efficiency is solved. In addition, the permeable membrane material has good resistance to the salt lake brine system, super-hydrophilicity, strong acid and alkali resistance and excellent long-term running stability, can realize efficient interception of various salt ions and soluble organic matters, exhibits excellent desalination performance and organic matter interception performance, and has a good application prospect in the salt lake brine system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The flow chart of the preparation method of the graphene oxide permeation membrane suitable for the concentrated salt brine system provided by the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0023] In the description of the present application, the meaning of one or more is one or more, the meaning of multiple is two or more, greater than, less than, more than and the like are understood as not including the number, above, below, within and the like are understood as including the number. If the terms "first", "second", "third" are described, they are only for the purpose of description and distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0024] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "setting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The embodiments will be described below according to the overall structure of the present application.

[0025] Figure 1 The flow chart of the preparation method of the graphene oxide permeation membrane suitable for the concentrated salt brine system provided by the present application, refer to Figure 1 , the method comprises:

[0026] S1, preparing a mixed solution of carboxylated graphene oxide (GO) and sodium alginate (SA).

[0027] In the preparation method of the graphene oxide permeation membrane suitable for the concentrated salt brine system provided by the present application, the mass ratio of the carboxylated graphene oxide to the sodium alginate is 0.4-1.6.

[0028] In the preferred embodiment, the carboxylated graphene oxide and sodium alginate mixed solution is uniformly mixed at a heating temperature of 25-80℃ and a stirring time of 2-16h.

[0029] In a more specific embodiment, the carboxylated graphene oxide and sodium alginate mixed solution is uniformly mixed at a heating temperature of 25-80℃ and a stirring time of 2-16h.-1 ~1.5mg·mL -1 The carboxylated graphene oxide dispersion solution is mixed with a sodium alginate solution at a heating temperature of 25-80°C and a stirring time of 2-16h to obtain a carboxylated graphene oxide and sodium alginate mixture solution.

[0030] S2, the carboxylated graphene oxide and sodium alginate mixture solution is pumped to a polyether sulfone (PES) base film for filtration and drying, so that the carboxylated graphene oxide and sodium alginate are loaded on the surface of the polyether sulfone base film to obtain a graphene oxide / sodium alginate composite film;

[0031] In a preferred embodiment, the drying temperature is 25-60°C.

[0032] In a more specific embodiment, the polyether sulfone base film is cleaned with deionized water, and then the mixed solution is pumped to the surface of the PES base film for filtration and drying by vacuum assisted self-assembly technology.

[0033] S3, the graphene oxide / sodium alginate composite film is immersed in a strontium ion (Sr 2+ ) solution to obtain a graphene oxide / sodium alginate-strontium composite film.

[0034] In a preferred embodiment, the concentration of strontium ions is 0.01-2.0 mol·L -1 . -1 .

[0035] In a preferred embodiment, the time for immersing in the strontium ion solution in step S3 is 2-16h.

[0036] S4, the graphene oxide / sodium alginate-strontium composite film is immersed in an iron ion solution to obtain the graphene oxide permeation membrane suitable for concentrated salt brine system.

[0037] In a preferred embodiment, the iron ion solution includes Fe 3+ and Fe 2+ , and the content of Fe 3+ is 0-1 mol·L -1 , and the content ratio of Fe 3+ to Fe 2+ is 10-100:1.

[0038] In a preferred embodiment, the time for immersing in the iron ion mixed solution is 2-16h.

[0039] The application also provides a graphene oxide permeation membrane suitable for concentrated salt brine system, which is prepared by the preparation method described above.

[0040] The preparation method of this invention uses polyethersulfone as the substrate membrane and constructs a GO / SA composite membrane by crosslinking highly hydrophilic natural hydrogel sodium alginate (SA) with carboxylated GO nanosheets. The introduction of sodium alginate not only effectively regulates the surface properties of the membrane, endowing it with superhydrophilicity and antifouling properties, but also provides more binding sites for subsequent metal ion intercalation, utilizing the alkali metal Sr 2+ and transition metal Fe 2+ Fe 3+ Different coordination capabilities lead to preferential intercalation of Sr 2+ A GO / SA-Sr composite membrane was constructed, and then Fe was introduced. 2+ Fe 3+ By using different coordination sites and ligand structures from the active groups on GO and SA, the microstructure of the membrane is optimized, thus constructing a complete, stable, and defect-free GO nanochannel.

[0041] Example 1

[0042] This embodiment 1 provides a graphene oxide permeation membrane suitable for concentrated brine systems. The preparation method of the graphene oxide permeation membrane is as follows:

[0043] (1) Preparation of GO and SA mixture

[0044] The concentration was prepared at 1.2 mg / mL. -1 A carboxylated GO dispersion was prepared, and sodium alginate solution was added to the dispersion. The mass ratio of GO to SA was 1.2. The mixture was stirred at room temperature for 12 hours to obtain a homogeneous mixture of carboxylated GO and SA.

[0045] (2) Preparation of GO / SA composite membrane

[0046] The 0.22 μm PES base membrane was cleaned with deionized water, and then the GO and SA mixture was pumped onto the surface of the PES base membrane for filtration using vacuum-assisted self-assembly technology. The membrane was then dried overnight at room temperature to obtain the GO / SA composite membrane.

[0047] (3) Preparation of GO / SA-Sr composite membrane

[0048] Immerse the GO / SA composite membrane in Sr 2+ The concentration is 0.1 mol L. -1 The membrane was immersed in a strontium chloride solution for 4 hours, then removed, washed, and dried to obtain a GO / SA-Sr composite membrane.

[0049] (4) Preparation of GO / SA-Sr-Fe composite membrane

[0050] The GO / SA-Sr composite membrane was immersed in Fe 3+ The content is 0.05 mol L.-1 Fe 3+ Fe 2+ The GO / SA-Sr-Fe composite film was obtained by immersing the GO / SA-Sr composite film in the iron ion solution with a content ratio of 50:1 for 4 hours, and then cleaning and drying.

[0051] Example 2

[0052] Compared with Example 1, the GO / SA-Sr composite film in Example 2 was immersed in the iron ion solution with a content ratio of 50:1 for 4 hours, and then cleaned and dried to obtain the GO / SA-Sr-Fe composite film. 3+ The content of the iron ion solution was 0.1 mol / L. -1 Fe 3+ Fe 2+ The GO / SA-Sr-Fe composite film was obtained by immersing the composite film in the iron ion solution with a content ratio of 50:1 for 4 hours, and then cleaning and drying. The other conditions were unchanged.

[0053] Experiment 1: Verification of organic matter interception

[0054] The GO / SA-Sr-Fe composite films prepared by Example 1 and Example 2 were used to separate organic matter in simulated salt lake brine. The membrane separation experiment adopted by the application included preparing simulated salt lake brine containing tributyl phosphate (TBP) as the membrane separation object, placing the GO / SA-Sr-Fe composite films prepared by Example 1 and Example 2 at the flange of the separation device, and fixing and clamping them with a clamp. The pressure remained unchanged at 0.1 bar during the separation process. During the separation process, the effective separation area of the membrane was kept at 1.5 cm 2 .

[0055] The ion composition of the simulated salt lake brine is shown in Table 1.

[0056] Table 1 Ion composition of simulated salt lake brine

[0057]

[0058] The simulated salt lake brine with a salt concentration of 127.18 g·L -1 was subjected to a separation experiment, and the results showed that the organic matter interception rate of the composite film prepared by Example 1 was 94.2%, and the permeation flux was 16690 L·m -2 ·h -1 ·bar -1 ; the organic matter interception rate of the composite film prepared by Example 2 was 96.69%, and the permeation flux was 22130 L·m -2 ·h -1 ·bar -1 .

[0059] The simulated salt lake brine with a salinity of 150.19 g·L -1, the organic matter rejection rate of the composite membrane prepared by the method of Example 1 is 95.1%, and the permeation flux is 12430 L·m -2 ·h -1 ·bar -1 ; the organic matter rejection rate of the composite membrane prepared by the method of Example 2 is 97.9%, and the permeation flux is 19700 L·m -2 ·h -1 ·bar -1 .

[0060] The simulated salt lake brine with a salinity of 95.33 g·L -1 was subjected to separation experiment, and the experimental results showed that the organic matter rejection rate of the composite membrane prepared by the method of Example 1 was 89.4%, and the permeation flux was 17205 L·m -2 ·h -1 ·bar -1 ; the organic matter rejection rate of the composite membrane prepared by the method of Example 2 was 93.3%, and the permeation flux was 24230 L·m -2 ·h -1 ·bar -1 .

[0061] The simulated salt lake brine with a salinity of 206.22 g·L -1 was subjected to separation experiment, and the experimental results showed that the organic matter rejection rate of the composite membrane prepared by the method of Example 1 was 96.7%, and the permeation flux was 9020 L·m -2 ·h -1 ·bar -1 ; the organic matter rejection rate of the composite membrane prepared by the method of Example 2 was 98.8%, and the permeation flux was 16078 L·m -2 ·h -1 ·bar -1 .

[0062] Experiment 2: Ion rejection verification

[0063] The GO / SA-Sr-Fe composite membranes prepared by the methods of Example 1 and Example 2 and the self-made H-type permeation device were used for ion separation experiment of simulated salt lake brine. First, the composite membrane was fixed on the H-type device by using iron clips to separate the feed liquid and the driving liquid. The feed liquid was 40 mL of simulated brine, and the driving liquid was 40 mL of deionized water. A magnetic sub was added on each side of the feed liquid and the driving liquid, and magnetic stirring was carried out at room temperature to prevent the occurrence of concentration polarization. During the separation process, the effective separation area of the membrane was kept at 0.785 cm 2 , and the membrane separation layer was oriented towards the feed liquid side to ensure the stability of the experiment and the maximum separation efficiency of the membrane.

[0064] The ion composition of the simulated salt lake brine used in the above separation process is shown in Table 2.

[0065] Table 2 Ion composition of simulated salt lake brine

[0066]

[0067] The simulated salt lake brine used in the experiment had a salinity of 130.5 g·L -1 -1, and the experimental results showed that the GO / SA-Sr-Fe composite membrane prepared in Example 1 had a rejection rate for different ions of Ca 2+ (99.3%), K + (98.6%), Li + (98.6%), Mg 2+ (99.4%), Na + (98.9%), Cl - (98.8%), and a total ion rejection rate of 98.8%; the GO / SA-Sr-Fe composite membrane prepared in Example 2 had a rejection rate for different ions of Ca 2+ (99.8%), K + (99.0%), Li + (99.6%), Mg 2+ (99.9%), Na + (99.3%), Cl - (99.5%), and a total ion rejection rate of 99.4%.

[0068] The simulated salt lake brine used in the experiment had a salinity of 130.5 g·L -1 -1, and the experimental results showed that the GO / SA-Sr-Fe composite membrane prepared in Example 1 had a rejection rate for different ions of Ca 2+ (99.1%), K + (98.4%), Li + (98.6%), Mg 2+ (99.6%), Na + (98.2%), Cl - (98.7%), and a total ion rejection rate of 98.6%; the GO / SA-Sr-Fe composite membrane prepared in Example 2 had a rejection rate for different ions of Ca 2+ (99.6%), K + (98.7%), Li + (99.4%), Mg 2+ (99.8%), Na + (99.1%), Cl - (99.3%), and a total ion rejection rate of 99.2%.

[0069] In summary, the application provides a preparation method of graphene oxide permeable membrane suitable for concentrated salt brine system, and the prepared permeable membrane material can achieve efficient interception of various dissolved organic matters in the salt lake brine system, and also has excellent desalination performance, and has good application prospect in the field of salt lake brine treatment.

[0070] The above description is merely a specific implementation of the present application, and it should be pointed out that, for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems, characterized in that, The method includes: S1. Preparation of a mixture of carboxylated graphene oxide and sodium alginate; S2. The mixture of carboxylated graphene oxide and sodium alginate is pumped to a polyethersulfone membrane for filtration and drying, so that the carboxylated graphene oxide and sodium alginate are loaded on the surface of the polyethersulfone membrane to obtain a graphene oxide / sodium alginate composite membrane. S3. The graphene oxide / sodium alginate composite membrane is immersed in a strontium ion solution to obtain a graphene oxide / sodium alginate-strontium composite membrane. S4. The graphene oxide / sodium alginate-strontium composite membrane is immersed in an iron ion solution to obtain the graphene oxide permeable membrane.

2. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S1, the mass ratio of carboxylated graphene oxide to sodium alginate is 0.4 to 1.

6.

3. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S1, the carboxylated graphene oxide and sodium alginate mixture are mixed evenly at a heating temperature of 25°C to 80°C and a stirring time of 2h to 16h.

4. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S2, the drying temperature is 25℃~60℃.

5. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S3, the strontium ion concentration is 0.01 mol·L⁻¹. -1 ~2.0 mol·L -1 .

6. The method for preparing a graphene oxide permeation membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S3, the immersion time in the strontium ion solution is 2h to 16h.

7. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S4, the iron ion solution includes Fe 3+ with Fe 2+ Fe 3+ The content is 0-1 mol·L -1 Fe 3+ with Fe 2+ The content ratio is 10 to 100:

1.

8. The method for preparing a graphene oxide permeable membrane suitable for concentrated brine systems according to claim 1, characterized in that, In step S4, the immersion time in the iron ion mixed solution is 2h to 16h.

9. A graphene oxide permeation membrane suitable for concentrated brine systems, characterized in that, The graphene oxide permeation membrane is prepared using the preparation method described in any one of claims 1 to 8.

10. An application of the graphene oxide permeation membrane as described in claim 9 for use in concentrated brine systems, characterized in that, The graphene oxide permeation membrane is used for the removal of organic matter and desalination in salt lake brine.

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