Preparation method of nanofiltration membrane with high magnesium-lithium selectivity

Abstract

The invention discloses a preparation method of a nanofiltration membrane with high magnesium and lithium selectivity. The method mainly comprises the following steps: (1) preparing an aqueous phase solution containing macrocyclic amine; (2) soaking a polyether sulfone base membrane into the water-phase solution in the step (1) for a certain time, taking out the base membrane, and removing redundant water drops; (3) preparing a normal hexane solution containing acyl chloride; (4) soaking the base membrane in the step (2) into the n-hexane solution in the step (3), and reacting for a certain time; (5) soaking the membrane in the step (4) into a secondary reaction aqueous solution containing an amine monomer, and reacting for a certain time; and (6) putting the obtained composite membrane into a drying oven, and heating for a period of time to obtain the high-magnesium-lithium selective nanofiltration membrane. The nanofiltration membrane prepared by the method has relatively high magnesium-lithium selectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment membranes, and particularly relates to a preparation method of a high magnesium-lithium selectivity nanofiltration membrane. Background Art

[0002] With the rapid development of electronic devices and new energy vehicles, the demand for lithium batteries has been increasing year by year. As an important material component of lithium batteries, lithium has limited reserves and has become an important strategic resource. More than 80% of China's lithium resources come from salt lakes, and lithium extraction from salt lakes has broad development prospects. However, salt lakes also contain a large amount of magnesium, whose properties are similar to those of lithium, making it difficult to achieve effective separation.

[0003] Nanofiltration technology has the advantage of selective separation, which can effectively intercept magnesium ions while allowing lithium ions to pass through, thereby achieving lithium enrichment. At the same time, the nanofiltration membrane separation technology has the advantages of low energy consumption, small investment, and easy scale-up, and has great application potential in the field of lithium extraction from salt lakes. However, the magnesium-lithium selectivity of traditional nanofiltration membranes is relatively low, which limits their separation efficiency. Yang et al. (Journal of Membrane Science, 2021, 620: 118862) prepared a nanofiltration membrane with high magnesium-lithium selectivity by reacting piperazine with trimesoyl chloride and then grafting polyethyleneimine. The rejection rate of magnesium chloride was 98.5%, the rejection rate of lithium chloride was 46.2%, and the separation factor was 33.4. Zhao et al. (Separation and Purification Technology, 2022, 286: 120419) used cyclodextrin and polyethyleneimine as aqueous phase monomers and trimesoyl chloride as the organic phase monomer to prepare a nanofiltration membrane with high magnesium-lithium selectivity through an interfacial polymerization reaction, and the separation factor was 10.8.

[0004] However, the separation factors of the above-mentioned nanofiltration membranes still cannot meet the requirements of lithium extraction from salt lakes. Therefore, the demand for nanofiltration membranes with high magnesium-lithium separation performance is extremely urgent. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a preparation method of a high magnesium-lithium selectivity nanofiltration membrane.

[0006] The technical solution of the present invention is outlined as follows:

[0007] A preparation method of a high magnesium-lithium selectivity nanofiltration membrane includes the following steps:

[0008] (1) Prepare an aqueous solution of macrocyclic amine with a concentration of 0.02 - 5 wt%;

[0009] (2) Immerse the polyethersulfone substrate membrane in the aqueous solution of (1) for 5 - 10 minutes, take out the substrate membrane, and remove the excess water droplets;

[0010] (3) Prepare a solution of acyl chloride in n-hexane with a concentration of 0.01 - 0.8 wt%.

[0011] (4) Immerse the base film in (3) the n-hexane solution and react for 1 - 30 min.

[0012] (5) Immerse the film in (4) a secondary reaction aqueous solution with an amine monomer concentration of 1 - 12 wt% and react for 5 - 60 min.

[0013] (6) Place the obtained composite film in an oven and heat it at 50 - 80 °C for 5 - 20 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0014] The macrocyclic amine described in step (1) is one or a mixture of several of triethylenetetramine, 1,4,7,10-tetraazacyclododecane, 1,4,7-triazacyclononane, 1,5,9-triazacyclododecane:

[0015]

[0016] The acyl chloride described in step (3) is one or a mixture of several of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride.

[0017] The amine monomer described in step (5) is one or a mixture of several of diethylenetriamine, 1,2-propanediamine, p-phenylenediamine, acridine-3,6-diamine.

[0018] The present invention has the following beneficial effects:

[0019] The method for preparing the nanofiltration membrane in the present invention is simple, the conditions are mild, and it has a high magnesium-lithium selectivity. The separation factor is above 50, and can even reach 90, which can meet the requirements of lithium extraction from salt lakes. Specific Embodiments

[0020] The technical solution of the present invention will be further limited below in combination with specific embodiments, but the scope of protection is not limited to the description made.

[0021] In the following examples, first, the rejection rate of the nanofiltration membrane for a 2 g / L magnesium chloride solution was tested under the conditions of 1.0 MPa and 25 °C; under the same conditions, the rejection rate of the nanofiltration membrane for a 2 g / L lithium chloride solution was tested; the separation factor was calculated, and the separation factor = (1 - lithium chloride rejection rate) / (1 - magnesium chloride rejection rate).

[0022] Trianglamine: Chaix, A. et al. Trianglamine-based supramolecular organic framework with permanent intrinsic porosity and tunable selectivity. J. Am. Chem. Soc. 140, 14571–14575 (2018).

[0023] Comparative example:

[0024] A method for preparing a selective nanofiltration membrane of the comparative example includes the following steps:

[0025] (1) Prepare an aqueous piperazine solution with a concentration of 2 wt%;

[0026] (2) Immerse the polyethersulfone substrate membrane in the aqueous solution of (1) for 10 min, take out the substrate membrane, and remove the excess water droplets;

[0027] (3) Prepare a 1,3,5-benzenetricarbonyl chloride n-hexane solution with a concentration of 0.8 wt%;

[0028] (4) Immerse the substrate membrane of (2) in the n-hexane solution of (3) and react for 1 min;

[0029] (5) Immerse the membrane in (4) in an aqueous solution of polyethyleneimine with a concentration of 2 wt% and react for 60 min;

[0030] (6) Put the obtained composite membrane into an oven and heat it at 80 °C for 10 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0031] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 97.3%, the rejection rate of lithium chloride was 10.3%, and the separation factor was 33.2.

[0032] Example 1

[0033] A method for preparing a high magnesium-lithium selectivity nanofiltration membrane includes the following steps:

[0034] (1) Prepare an aqueous trianglamine solution with a concentration of 0.02 wt%;

[0035] (2) Immerse the polyethersulfone substrate membrane in the aqueous solution of (1) for 10 min, take out the substrate membrane, and remove the excess water droplets;

[0036] (3) Prepare a 1,3,5-benzenetricarbonyl chloride n-hexane solution with a concentration of 0.8 wt%;

[0037] (4) Immerse the substrate membrane of (2) in the n-hexane solution of (3) and react for 1 min;

[0038] (5) Immerse the membrane in (4) into an aqueous solution of 1,2-propanediamine with a concentration of 12 wt% and react for 60 min;

[0039] (6) Put the obtained composite membrane into an oven and heat it at 80 °C for 10 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0040] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 99.1%, the rejection rate of lithium chloride was 18.6%, and the separation factor was 90.4.

[0041] Example 2

[0042] A preparation method of a high magnesium-lithium selectivity nanofiltration membrane, comprising the following steps:

[0043] (1) Prepare an aqueous solution of 1,5,9-triazacyclododecane with a concentration of 5 wt%;

[0044] (2) Immerse the polyethersulfone substrate membrane in the aqueous solution of (1) for 5 min, take out the substrate membrane, and remove the excess water droplets;

[0045] (3) Prepare a n-hexane solution of terephthaloyl chloride with a concentration of 0.05 wt%;

[0046] (4) Immerse the substrate membrane of (2) in the n-hexane solution of (3) and react for 30 min;

[0047] (5) Immerse the membrane in (4) into an aqueous solution of acridine-3,6-diamine with a concentration of 5 wt% and react for 5 min;

[0048] (6) Put the obtained composite membrane into an oven and heat it at 50 °C for 5 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0049] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 98.5%, the rejection rate of lithium chloride was 22.4%, and the separation factor was 51.7.

[0050] Example 3

[0051] A preparation method of a high magnesium-lithium selectivity nanofiltration membrane, comprising the following steps:

[0052] (1) Prepare an aqueous solution of 1,4,7,10-tetraazacyclododecane with a concentration of 1 wt%;

[0053] (2) Immerse the polyethersulfone substrate membrane in the aqueous solution of (1) for 10 min, take out the substrate membrane, and remove the excess water droplets;

[0054] (3) Prepare a 0.01 wt% solution of isophthaloyl chloride in n-hexane;

[0055] (4) Immerse the base film in step (2) into the n-hexane solution in step (3) and react for 20 min;

[0056] (5) Immerse the film in step (4) into an aqueous solution of p-phenylenediamine with a concentration of 1 wt% and react for 20 min;

[0057] (6) Put the obtained composite film into an oven and heat it at 60 °C for 20 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0058] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 98.6%, the rejection rate of lithium chloride was 28.6%, and the separation factor was 51.0.

[0059] Example 4

[0060] A preparation method of a high magnesium-lithium selectivity nanofiltration membrane, comprising the following steps:

[0061] (1) Prepare an aqueous solution with a concentration of 2 wt% of triethylenetetramine and 0.5 wt% of 1,4,7-triazacyclononane;

[0062] (2) Immerse the polyethersulfone base film into the aqueous solution in step (1) for 7 min, take out the base film, and remove the excess water droplets;

[0063] (3) Prepare a n-hexane solution with a concentration of 0.02 wt% of terephthaloyl chloride and 0.08 wt% of phthaloyl chloride;

[0064] (4) Immerse the base film in step (2) into the n-hexane solution in step (3) and react for 15 min;

[0065] (5) Immerse the film in step (4) into an aqueous solution of diethylenetriamine with a concentration of 5 wt% and react for 15 min;

[0066] (6) Put the obtained composite film into an oven and heat it at 70 °C for 20 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0067] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 98.9%, the rejection rate of lithium chloride was 26.1%, and the separation factor was 67.2.

[0068] Example 5

[0069] A preparation method of a high magnesium-lithium selectivity nanofiltration membrane, comprising the following steps:

[0070] (1) Prepare an aqueous solution with a 1wt% concentration of 1,4,7-triazacyclononane;

[0071] (2) Immerse the polyethersulfone-based membrane in the aqueous solution of (1) for 10 min, take out the base membrane, and remove the excess water droplets;

[0072] (3) Prepare a n-hexane solution with a 0.5wt% concentration of trimesoyl chloride;

[0073] (4) Immerse the base membrane of (2) in the n-hexane solution of (3) and react for 20 min;

[0074] (5) Immerse the membrane in (4) in a secondary reaction aqueous solution with a 1wt% concentration of diethylenetriamine and a 5wt% concentration of 1,2-propanediamine, and react for 30 min;

[0075] (6) Place the obtained composite membrane in an oven and heat it at 60 °C for 15 min to obtain a high magnesium-lithium selectivity nanofiltration membrane.

[0076] The separation performance of the prepared high magnesium-lithium selectivity nanofiltration membrane was tested: the rejection rate of magnesium chloride was 98.5%, the rejection rate of lithium chloride was 28.0%, and the separation factor was 48.0.

Claims

1. A preparation method of a high magnesium-lithium selectivity nanofiltration membrane, characterized in that the specific steps are as follows: (1) Prepare an aqueous solution of macrocyclic amine; (2) Immerse the polyethersulfone substrate membrane into the aqueous solution of (1), take out the substrate membrane, and remove the excess water droplets; (3) Prepare an acyl chloride solution; (4) Immerse the substrate membrane of (2) into the solution of (3) and react; (5) Immerse the membrane in (4) into the secondary reaction aqueous solution of amine monomer and react; (6) Put the obtained composite membrane into an oven for drying to obtain a high magnesium-lithium selectivity nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that the macrocyclic amine described in step (1) is one or a mixture of several of triethylenetetramine, 1,4,7,10-tetraazacyclododecane, 1,4,7-triazacyclononane, 1,5,9-triazacyclododecane.

3. The preparation method according to claim 1 or 2, characterized in that the concentration of the macrocyclic amine aqueous solution in step (1) is 0.02-5 wt%.

4. The preparation method according to claim 1, characterized in that the immersion time in step (2) is 5-10 min.

5. The preparation method according to claim 1, characterized in that the acyl chloride described in step (3) is one or a mixture of several of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride.

6. The preparation method according to claim 1 or 5, characterized in that the concentration of the acyl chloride solution in step (3) is 0.01-0.8 wt%.

7. The preparation method according to claim 1, characterized in that the reaction time in step (4) is 1-30 min.

8. The preparation method according to claim 1, characterized in that the amine monomer described in step (5) is one or a mixture of several of diethylenetriamine, 1,2-propanediamine, p-phenylenediamine, acridine-3,6-diamine.

9. The preparation method according to claim 1 or 8, characterized in that the concentration of the amine monomer in step (5) is 1-12 wt%; preferably, the reaction time is 5-60 min.

10. The preparation method according to claim 1, characterized in that in step (6), it is dried at 50-80 °C for 5-20 min.

Images