阅读说明：本技术 一种纳滤复合膜、制备方法及应用 (Nanofiltration composite membrane, preparation method and application ) 是由 张炜铭 张文彬 施梦琦 潘丙才 吕路 于 2019-10-29 设计创作，主要内容包括：本发明公开了一种纳滤复合膜、制备方法及应用,属于废水处理领域。所述制备方法包括以下步骤：A)制备2D纳米材料分散液；B)首先制备一定浓度的高分子材料的溶液,在搅拌条件下不断加入不良溶剂,使高分子材料进行化学反应得到带负电的高分子凝胶粒子的分散液；C)步骤A)中的纳米材料分散液与步骤B)中制备的分散液进行共混、制膜、干燥,然后放入一定浓度的碱性溶液和纯水中进行浸泡,得到纳滤复合膜。本发明的纳滤复合膜能够通过孔径筛分和电荷排斥的协同作用,实现对重金属络合离子的高效去除。而且长时间使用其截留率及通量未发生明显变化,利于推广。(The invention discloses a nanofiltration composite membrane, a preparation method and application thereof, belonging to the field of wastewater treatment. The preparation method comprises the following steps: A) preparing a 2D nano material dispersion liquid; B) firstly, preparing a solution of a high polymer material with a certain concentration, and continuously adding a poor solvent under the stirring condition to ensure that the high polymer material undergoes a chemical reaction to obtain a dispersion liquid of negatively charged high polymer gel particles; C) blending, film making and drying the nano material dispersion liquid in the step A) and the dispersion liquid prepared in the step B), and then soaking the nano material dispersion liquid and the dispersion liquid in an alkaline solution and pure water with certain concentration to obtain the nanofiltration composite film. The nanofiltration composite membrane can realize the high-efficiency removal of heavy metal complex ions through the synergistic effect of pore size screening and charge repulsion. And the interception rate and the flux of the material do not change obviously after long-time use, thereby being beneficial to popularization.)

1. A nanofiltration composite membrane is characterized in that: the preparation method comprises the following steps:

A) preparing a 2D nano material dispersion liquid;

B) firstly, preparing a solution of a high polymer material with a certain concentration, and continuously adding a poor solvent under the stirring condition to ensure that the high polymer material undergoes a chemical reaction to obtain a dispersion liquid of negatively charged high polymer gel particles;

C) blending, film making and drying the nano material dispersion liquid in the step A) and the dispersion liquid prepared in the step B), and then soaking the nano material dispersion liquid and the dispersion liquid in an alkaline solution and pure water with certain concentration to obtain the nanofiltration composite film.

2. Nanofiltration composite membrane according to claim 1, wherein: the polymer material comprises any one of polymethacrylic acid, sodium polyethylene sulfonate, polyacrylonitrile or polymethyl acrylate.

3. Nanofiltration composite membrane according to claim 1 or 2, wherein: the 2D nano material comprises graphene oxide and MoS ₂Any one of LDH or Mxene.

4. Nanofiltration composite membrane according to claim 3, wherein: the particle size of the polymer gel particles in the step B) is 0.5-10 nm.

5. Nanofiltration composite membrane according to claim 1, wherein: the concentration of the 2D nano-material dispersion liquid prepared in the step A) is 0.001-10 mg/mL.

6. Nanofiltration composite membrane according to claim 1 or 2, wherein: the poor solvent in the step B) comprises any one of ethanol, water, hexane, acetonitrile or petroleum ether, and the adding volume of the poor solvent accounts for 5-85% of the total volume of the solution.

7. Nanofiltration composite membrane according to claim 1 or 2, wherein: the film thickness is controlled to be 5 nm-50 μm during film forming in the step C).

8. Nanofiltration composite membrane according to claim 7, wherein: the method for preparing the film in the step C) comprises but is not limited to any one of vacuum filtration, a hot-table casting method or a spin coater film preparation method.

9. Nanofiltration composite membrane according to claim 1 or 2, wherein: when the nano material dispersion liquid in the step A) is blended with the solution prepared in the step B), the mass ratio of the 2D nano material to the high polymer material is 1: (0.001-10).

10. Use of a nanofiltration composite membrane according to claim 1, characterized in that: the nanofiltration composite membrane is used for removing heavy metal complex ions in a water body.

Technical Field

The invention belongs to the field of wastewater treatment, and particularly relates to a nanofiltration composite membrane for removing heavy metal complex ions, a preparation method and application.

Background

In the production process of the industries such as electroplating, tanning, mining and the like, a large amount of wastewater containing heavy metals is discharged, and the heavy metals are combined with a complexing agent to form heavy metal complex ions. The heavy metal complex ions have large migration range and high stability, and cause great harm to the environment and the healthy life of people. Theoretically, the purpose of adsorbing and removing heavy metal complex ions can be achieved by using a high-molecular nanofiltration membrane. However, the heavy metal complex ions are generally organic complexing agents, and when used, the heavy metal complex ions usually cause swelling of a polymer membrane, and further cause serious membrane pollution, and finally cause significant reduction in separation efficiency, so that the heavy metal complex ions are not suitable for use in the actual use process, and the current common mode is as follows: firstly, heavy metal complex ions are subjected to complex breaking to separate heavy metals from complexes, and then the traditional method for treating the heavy metals is used as a current universal treatment way. At present, the method for treating heavy metal complex ions mainly comprises the steps of breaking the complex by an advanced oxidation method (fenton reaction, photocatalysis, electrooxidation and the like), and then removing the dissociated heavy metals by utilizing a chemical adsorption method or a precipitation method.

Through retrieval, related applications have been disclosed in the prior art, such as chinese patent No. 201611032142.1, application publication No. 2017.03.22, which discloses a method for treating heavy metal wastewater by complex breaking of granular sludge and ceramic membrane, a system and a method for treating heavy metal wastewater by complex breaking, the system comprising: the stirring reactor is used for mixing and reacting the sludge wastewater containing the complexing heavy metal, the pH adjusting liquid medicine and the decomplexing agent under stirring to convert at least part of the complexing heavy metal ions into a granular state; the membrane separation tank is connected with the stirring reactor, a interception membrane is arranged in the membrane separation tank and used for intercepting particulate matters in the mixed liquid after the mixed reaction, a sludge particle layer formed by interception and the interception membrane cooperate to further capture heavy metal particles converted into a particle state and complex heavy metal ions which are not fully reacted, and a captured substance becomes a part of the sludge particle layer and participates in interception; the clean water passes through the membrane hole of the interception membrane and is pumped to the clean water tank by the membrane suction pump.

As another example, Chinese patent No. 201310160786.9, granted publication No. 2016.01.20, discloses a photoelectrocatalytic process for treating heavy metal complex wastewater and recovering heavy metal ions therefrom, and more particularly, a process for irradiating TiO at the anode with ultraviolet light having a wavelength of less than 387nm in a photoelectric reactor containing the wastewater ₂A thin film surface generating photo-generated holes and hydroxyl radicals as strong oxidants that degrade heavy metal complexes while recovering liberated heavy metal ions at the cathode by electrodeposition reduction, the photo-electric reactor comprising: an ultraviolet lamp that emits the ultraviolet light; anode of titanium-based TiO ₂A thin film electrode and a cathode; wherein the anode and the cathode are respectively connected to the positive pole and the negative pole of a direct current power supply.

The method of the above application has high requirements on the pH of water and may cause secondary pollution. Therefore, based on the defects of the prior art, a method which can effectively remove heavy metal complex ions and avoid the defects of high requirement on water pH and possible secondary pollution is needed to be provided.

Disclosure of Invention

1. Problems to be solved

Aiming at the problems of high requirement on the pH value of water quality and possibility of secondary pollution in the prior art for removing heavy metal complex ions, the invention provides the composite membrane capable of efficiently removing the heavy metal complex ions through the synergistic effect of pore size screening and charge repulsion.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the invention provides a nanofiltration composite membrane for removing heavy metal complex ions, which comprises the following steps:

A) preparing 2D nano material dispersion liquid by taking water as a solvent,

B) firstly, preparing a solution of a high polymer material with a certain concentration, continuously adding a poor solvent under the stirring condition, inducing to generate high polymer gel particles, and further performing nucleophilic reaction on the high polymer material to obtain a dispersion liquid containing the high polymer gel particles with negative electricity;

C) blending, film making and drying the nano material dispersion liquid in the step A) and the solution prepared in the step B), and then soaking the nano material dispersion liquid and the solution in pure water to obtain the nanofiltration composite film.

As a further improvement of the present invention, the poor solvent includes, but is not limited to, ethanol, water, hexane, acetonitrile and petroleum ether.

As a further improvement of the present invention, the polymer material includes any one of polyacrylonitrile, sodium polyvinylsulfonate, polymethacrylic acid or polymethylmethacrylate, but is not limited to the above materials.

As a further improvement of the invention, the 2D nano material comprises graphene oxide and MoS ₂Any one of, LDH or Mxene, but not limited to the above materials.

As a further improvement of the invention, the particle size of the polymer gel particles is 0.5-10 nm.

As a further improvement of the invention, the concentration of the 2D nano-material dispersion liquid prepared in the step A) is 0.001-10 mg/mL.

As a further improvement of the invention, the adding volume of the poor solvent in the step B) accounts for 5-85% of the total volume of the solution, and the total volume of the solution is the total volume after the poor solvent is added.

As a further improvement of the present invention, the film thickness is controlled to be 5nm to 50 μm during the film formation in the step C).

As a further improvement of the present invention, the method for preparing the film in the step C) includes any one of vacuum filtration, a hot-stage casting method or a spin coater film preparation method.

As a further improvement of the present invention, when the nanomaterial dispersion liquid in step a) is blended with the solution prepared in step B), the mass ratio of the 2D nanomaterial to the polymer material is 1: (0.001-10).

As a further improvement of the invention, the nanofiltration composite membrane is used for removing the heavy metal complex ions in the water body.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the nanofiltration composite membrane, the dispersion liquid of the polymer gel particles with negative electricity and the 2D nano material dispersion liquid are subjected to blending reaction to prepare the membrane, so that the nanofiltration composite membrane with excellent size sieving performance and electrostatic repulsion performance is obtained, and the nanofiltration composite membrane has high removal rate aiming at substances such as heavy metal complex ions which are difficult to remove independently, and the method for removing the heavy metal complex ions in the prior art is generally as follows: firstly, a high-grade oxidation/decomplexing agent is utilized to break the decomplexing, and then a chemical adsorption or precipitation method is utilized to remove the dissociated heavy metal, so that the defects of high requirement on the pH value of water quality and possibility of secondary pollution are generally existed; the nanofiltration composite membrane can be directly used for adsorbing and removing heavy metal complex ions, breaks through the technical difficulty, has low requirements on water quality, does not produce secondary pollution, and is convenient to use.

(2) The nanofiltration composite membrane is used for removing heavy metal complex ions, has higher negative electrical property compared with a membrane (graphene oxide membrane) prepared from a pure 2D nano material, and can effectively improve the removal performance of the heavy metal complex ions with negative charges through electrostatic repulsion performance; simultaneous high moleculeThe incorporation of particles can in turn significantly improve the size sieving properties of the membrane. The composite membrane prepared by the method has excellent removal performance on different heavy metal complex ions and complex ions of different coordination heavy metals, the retention rates of the composite membrane on Cu-NTA, Cu-CA and Cu-EDTA are respectively greater than 96%, and the flux is greater than 12L/m ²h, the retention rates of the metal ion exchange membrane to Cu-EDTA, Ni-EDTA and Cr-EDTA are all more than 97%, and the flux is more than 12L/m ²h.。

(3) The nanofiltration composite membrane is a novel nanofiltration membrane compounded with a 2D nano material and macromolecular gel particles, is used as an inorganic membrane, and cannot swell due to contact of heavy metal complex ions after long-term use, and experiments show that the nanofiltration composite membrane disclosed by the invention has no obvious change in flux and retention rate after continuous 120-hour test on long-time Cu-EDTA removal, so that the nanofiltration membrane still keeps good removal performance after running for 120 hours. Therefore, the problems of polymer membrane swelling and membrane pollution caused by the adsorption and removal of heavy metal complex ions by using a polymer nanofiltration membrane and the final obvious reduction of separation efficiency are solved.

Drawings

FIG. 1 is a schematic view of a nanofiltration composite membrane;

FIG. 2 is a flow chart of the preparation of a nanofiltration composite membrane;

fig. 3 is an optical photograph of the nanofiltration composite membrane prepared in example 1;

fig. 4 is a Transmission Electron Microscope (TEM) view of the nanofiltration composite membrane prepared in example 1;

fig. 5 is a diagram of the nanofiltration composite membrane prepared in example 1 for removing different heavy metal complex ions;

fig. 6 is a diagram for removing complex ions of different coordinated heavy metals from the nanofiltration composite membrane prepared in example 1;

FIG. 7 is a graph showing a long-term Cu-EDTA removal test of the nanofiltration composite membrane prepared in example 1;

fig. 8 is a comparison of Cu-EDTA rejection for pure GO membrane in comparative example 1 and nanofiltration composite membrane of the present invention (GO/PMAA).

Detailed Description

The invention is further described with reference to specific examples.