阅读说明：本技术 一种用于染料去除的陶瓷复合纳滤膜及其制备方法 (Ceramic composite nanofiltration membrane for dye removal and preparation method thereof ) 是由 高能文 张燕 梁富杰 王洪 毕亚非 于 2020-04-30 设计创作，主要内容包括：本发明涉及一种用于染料去除的陶瓷复合纳滤膜的制备方法,属于膜分离领域。本发明采用管状或片状陶瓷基底作为载体,首先使多巴胺类化合物和聚乙烯亚胺在载体表面形成共沉积层,再在共沉积层上负载TiO<Sub>2</Sub>,最后用没食子酸交联,得到复合纳滤膜。本发明制备过程简单、反应条件温和,制得的陶瓷复合纳滤膜机械强度高、稳定性好、渗透通量大且截留率高。适用于废水中染料的去除,也适用于有机溶剂中染料的去除。(The invention relates to a preparation method of a ceramic composite nanofiltration membrane for dye removal, belonging to the field of membrane separation. The invention adopts a tubular or sheet ceramic substrate as a carrier, firstly, dopamine compound and polyethyleneimine form a codeposition layer on the surface of the carrier, and then TiO is loaded on the codeposition layer 2 And finally, crosslinking with gallic acid to obtain the composite nanofiltration membrane. The preparation process is simple, the reaction conditions are mild, and the prepared ceramic composite nanofiltration membrane is high in mechanical strength, good in stability, large in permeation flux and high in rejection rate. Is suitable for removing the dye in the wastewater and is also suitable for removing the dye in the organic solvent.)

1. A preparation method of a ceramic composite nanofiltration membrane for dye removal is characterized by comprising the following steps:

step 1, soaking a ceramic membrane in deionized water for prewetting;

step 2, preparing 40-60mM aqueous solution of trihydroxymethane, and adjusting the pH value to 7.5-9.0; adding dopamine compound and polyethyleneimine, and uniformly mixing;

step 3, placing the ceramic membrane obtained in the step 1 in the first mixed solution obtained in the step 2, reacting, and taking out after the reaction is finished;

step 4, adding dilute hydrochloric acid and ammonia water into deionized water, adjusting the pH value to 2-4, adding titanium tetrafluoride to enable the concentration of the titanium tetrafluoride to be 0.01-0.07M to obtain a second mixed solution, placing the ceramic membrane obtained in the step 3 into the second mixed solution, reacting, and taking out after the reaction is finished;

and 5, placing the ceramic membrane obtained in the step 4 in 1-3mg/mL of trihydroxymethane water solution of gallic acid for reaction, and taking out after the reaction is finished to obtain the composite nanofiltration membrane.

2. The method for preparing a ceramic composite nanofiltration membrane for dye removal according to claim 1, wherein in one embodiment, in the step 1, the prewetting time is 1 hour or more; the ceramic membrane is a porous ceramic membrane prepared from an oxide at least containing one element of Al, Zr, Ti and Si, the average pore diameter of the ceramic membrane is 0.5-200 nm, and the ceramic membrane is a tubular membrane or a flat membrane;

in one embodiment, in the step 2, the mass concentration of the dopamine compound is 1-5mg/mL, the mass ratio of the polyethyleneimine to the dopamine compound is 1:0.5-1.5, and the molecular weight of the polyethyleneimine is 400-800 Da; the dopamine compound is dopamine, catechol, tannic acid or derivatives.

3. The method for preparing a ceramic composite nanofiltration membrane for dye removal according to claim 1, wherein in one embodiment, in the step 3, the reaction time is 4-8h, and the reaction conditions are room temperature;

in one embodiment, in the step 4, the reaction temperature is 20 to 100 ℃ and the reaction time is 0.5 to 6 hours.

4. The method of claim 1, wherein in the step 5, the concentration of the aqueous trihydroxymethane solution is 40-60mM, and the pH range is 8.0-9.0; the reaction time is 5-120min, and the reaction temperature is room temperature;

in one embodiment, said steps 1 to 5 are repeated from 1 to 20 times.

5. The composite nanofiltration membrane obtained by the preparation method of claim 1.

6. Use of the composite nanofiltration membrane according to claim 5 in dye desalination treatment in aqueous solution and dye removal in organic solvents.

7. Use according to claim 6, wherein in one embodiment, the dye desalting in the aqueous solution is separation of the dye from an inorganic salt;

in one embodiment, the dye is selected from Congo Red, methyl blue, reactive Brilliant Red, methyl orange, or methylene blue;

in one embodiment, the inorganic salt is selected from NaCl or Na₂SO₄。

8. Use according to claim 6, characterized in that the removal of the dye in an organic solvent, in one embodiment selected from ethanol, isopropanol, n-hexane, is carried out, said dye being selected from methyl orange, congo red, methyl blue.

9. Application of dopamine compound in preparing nanofiltration membrane modifier.

10. Use according to claim 9, wherein in one embodiment the modifier is for reducing the surface roughness of the separation layer of the nanofiltration membrane, reducing the molecular weight cut-off, increasing the separation factor of the nanofiltration membrane from dyes and inorganic salts or increasing the fouling resistance of the nanofiltration membrane.

Technical Field

The invention relates to a preparation method of a ceramic composite nanofiltration membrane, in particular to a method for constructing a composite nanofiltration membrane by using a dopamine compound and polyethyleneimineThe co-deposited layer chelating TiO produced by hydrolysis of titanium tetrafluoride₂And then cross-linked with gallic acid to obtain the ceramic composite nanofiltration membrane for dye removal, belonging to the field of membrane separation.

Background

The textile industry generates a great deal of dye wastewater with high salinity every year, and has the characteristics of high toxicity, complex components, great treatment difficulty and the like. The conventional dye wastewater treatment methods comprise flocculation precipitation, adsorption, biodegradation, advanced oxidation and the like, and have certain limitations. The flocculation precipitation method can play a certain role in decoloring, but can only play a role in part of dyes. The adsorbent is also selective to dye molecules, and the adsorbent is difficult to regenerate. Biodegradation methods, although less difficult to operate, tend to run for long periods. The advanced oxidation process is easy to cause secondary pollution, and the oxidant is expensive; moreover, the purpose of oxidation and degradation is to dispose of the pollutants, and the recovery of resources cannot be realized.

A large amount of organic solvents are used in the production of petrochemical products. If the organic solvents can be recycled, the harm to the environment and human beings can be reduced, and the production cost can be reduced, so that the method is a very favorable project. Conventional organic solvent recovery is usually achieved by extractive distillation, which is energy-intensive, solvent-consuming and environmentally friendly. With the rapid development of membrane separation technology, considering factors such as energy consumption and environmental protection, membrane separation technology gradually becomes an effective way for solvent recovery and separation.

The nanofiltration membrane technology is used as a pressure-driven membrane separation process, has the advantages of high efficiency, energy conservation, mild working conditions and the like, the operating pressure is generally between 0.5MPa and 1.5 MPa, and small molecules with the molecular weight of 200-1000 Da can be effectively intercepted. Nanofiltration membranes are widely used in dye separation. Lin et al (J. Membr. Sci., 477 (2015)) used commercial membranes Sepro NF 6 and Sepro NF 2A to separate different dyes and salt mixed solutions, and found that the commercial membranes have good retention (99.9%) for dyes and certain permeability for salt. Zhang et al (ACS appl.Interfaces, 2017, 9(12): 11082) are subjected to interfacial polymerization by isophorone diisocyanate (IPDI) and Tannic Acid (TA), and Graphene Oxide Quantum Dots (GOQDs) are used as water phase additives to prepare the composite nanofiltration membrane, wherein the rejection rate of the composite nanofiltration membrane to methylene blue in an aqueous solution is 97.6%, and the rejection rate of the composite nanofiltration membrane to NaCl is 17.2%. Liu et al (chem. Eng. Res. Des., 153(2020) 572-581) deposit hydroxyethylcellulose on a polypropylene membrane with a pore size of 90 nm, and cross-link with glutaraldehyde to obtain a nanofiltration membrane with retention rates of 95.4% and 84.2% for methyl blue and Congo red in ethanol, respectively, and a permeation flux of 4.6L/(m.m.²H.bar). Li et al (J. Membr. Sci., 601 (2020) 117951) coated a self-microporous polymer on the surface of a polyacrylonitrile carrier membrane with a molecular weight cut-off of 5 ten thousand, and the obtained nanofiltration membrane has a cut-off rate of 93.7% for methyl orange in ethanol and a permeation flux of 4.3L/(m m.m.²H.bar). At present, the nanofiltration membrane material mainly takes an organic nanofiltration membrane as a main material. However, organic nanofiltration membranes generally have the characteristics of poor mechanical strength, poor chemical stability and short service life. Therefore, the preparation of the nanofiltration membrane with good stability and excellent separation performance has important significance.

Researches find that amino groups, catechol groups and catechol groups in Dopamine (DA) molecules enable the dopamine to have the universality of deposition substrates and rich post-functionalization capability, so that a new way is opened for the preparation of composite membranes, and the dopamine can be used for preparing organic-inorganic composite membranes. In the existing report, chinese patent CN102614789A discloses a method for preparing a nanofiltration separation layer by depositing polydopamine on an organic or inorganic base membrane and then subsequently grafting and crosslinking; however, the method has long time for constructing the membrane layer and low water flux. Chinese patent CN105289336A discloses a method for preparing a nanofiltration separation layer on the surface of an organic membrane by co-deposition of catechol and polyethyleneimine; however, the composite nanofiltration membrane prepared by the method cannot realize the efficient separation of the dye and the inorganic salt in the dye wastewater.

Disclosure of Invention

In order to obtain a nanofiltration membrane with better performance, the invention provides a method for chelating titanium tetrafluoride hydrolysis by using a codeposition layer constructed by dopamine compound and Polyethyleneimine (PEI)Produced TiO₂And then cross-linking with gallic acid (PG) to prepare the ceramic composite nanofiltration membrane. Wherein, in the PDA/PEI codeposition layer, the PDA is used for tightly connecting the codeposition layer with the base film by utilizing the characteristic that molecules are easy to adhere to the codeposition layer, so that the codeposition layer is more tight, and then the PDA is connected with TiO₂After the chelating and the cross-linking with gallic acid (PG) are carried out, the roughness of a separation layer on the surface can be obviously reduced, so that the nanofiltration membrane has better pollution resistance in the separation process of organic matters; in addition, the catechol group in the PDA molecule can chelate metal oxide for further modification. PEI was added because low molecular weight PEI contained a large number of amino groups that could react with DA, accelerating the deposition process and resulting in a more dense interlayer. TiO 2₂The low price, the prepared separation layer has good compactness and strong hydrophilicity, and has a self-cleaning function and is introduced. Meanwhile, PG can form a host-guest inclusion compound with PEI, and PG is utilized to crosslink the deposition skin layer, so that the stability and compactness of the membrane layer can be further improved, and the ceramic composite nanofiltration membrane with good stability and excellent separation performance is obtained.

And (2) placing the ceramic membrane in a dopamine compound/polyethyleneimine buffer solution, carrying out oscillation reaction for a certain time, taking out, soaking in a mixed solution of dilute hydrochloric acid, ammonia water and titanium tetrafluoride for a certain time, taking out, continuously soaking in a gallic acid solution for a certain time, airing and cleaning to obtain the dye desalination ceramic composite nanofiltration membrane.

In a first aspect of the present invention, there is provided:

a preparation method of a dye desalination ceramic composite nanofiltration membrane comprises the following steps:

step 1, soaking a ceramic membrane in deionized water for prewetting;

step 2, preparing 40-60mM aqueous solution of trihydroxymethane, and adjusting the pH value to 7.5-9.0; adding dopamine compound and polyethyleneimine, and uniformly mixing;

step 3, placing the ceramic membrane obtained in the step 1 in the first mixed solution obtained in the step 2, reacting, and taking out after the reaction is finished;

step 4, adding dilute hydrochloric acid and ammonia water into deionized water, adjusting the pH value to 2-4, adding titanium tetrafluoride to enable the concentration of the titanium tetrafluoride to be 0.01-0.07M to obtain a second mixed solution, placing the ceramic membrane obtained in the step 3 into the second mixed solution, reacting, and taking out after the reaction is finished;

and 5, placing the ceramic membrane obtained in the step 4 in 1-3mg/mL of trihydroxymethane water solution of gallic acid for reaction, and taking out after the reaction is finished to obtain the composite nanofiltration membrane.

In one embodiment, in the step 1, the pre-wetting time is more than 1 h; the ceramic membrane is a porous ceramic membrane prepared from an oxide at least containing one element of Al, Zr, Ti and Si, the average pore diameter of the ceramic membrane is 0.5-200 nm, and the ceramic membrane is a tubular membrane or a flat membrane.

In one embodiment, in the step 2, the mass concentration of the dopamine compound is 1-5mg/mL, the mass ratio of the polyethyleneimine to the dopamine compound is 1:0.5-1.5, and the molecular weight of the polyethyleneimine is 400-800 Da; the dopamine compound is dopamine, catechol, tannic acid or derivatives.

In one embodiment, in step 3, the reaction time is 4 to 8 hours and the reaction conditions are room temperature.

In one embodiment, in the step 4, the reaction temperature is 20-100 ℃ and the reaction time is 0.5-6 h.

In one embodiment, in step 5, the concentration of the aqueous trihydroxymethane solution is 40-60mM, and the pH range is 8.0-9.0; the reaction time is 5-120min, and the reaction temperature is room temperature.

In one embodiment, said steps 1 to 5 are repeated from 1 to 20 times.

In a second aspect of the present invention, there is provided:

the composite nanofiltration membrane obtained by the method is used for the dye desalination treatment.

In one embodiment, the dye desalting refers to separation of the dye from the inorganic salt.

In one embodiment, the dye is selected from Congo Red, methyl blue, reactive Brilliant Red, methyl orange, or methylene blue.

In one embodiment, the inorganic salt is selected from NaCl or Na₂SO₄。

In a third aspect of the present invention, there is provided:

application of dopamine compound in preparing nanofiltration membrane modifier.

In one embodiment, the modifier is used to reduce the surface roughness of the separation layer of the nanofiltration membrane, reduce the molecular weight cut-off, increase the separation factor of the nanofiltration membrane from dyes and inorganic salts, or increase the fouling resistance of the nanofiltration membrane.

Advantageous effects

1. The invention utilizes a codeposition method to construct a polydopamine/polyethyleneimine codeposition layer, and prepares metal oxide particles required by deposition through hydrolysis reaction. The catechol group in the polydopamine can form a coordination bond with metal ions in metal oxide, so that metal oxide particles are induced to deposit and mineralize on the surface of the basement membrane to form a compact metal oxide mineral layer, and then cross-linking is carried out, so that the high-performance ceramic composite nanofiltration membrane is constructed.

2. The ceramic composite nanofiltration membrane obtained by the method has a good dye interception effect and good stability. Can be used for concentrating and desalting the aqueous dye and can also be used for removing the dye in the organic solvent.

3. According to the method, titanium tetrafluoride is hydrolyzed to generate titanium oxide nanoparticles in situ, on one hand, the titanium oxide nanoparticles can show high organic solvent resistance, on the other hand, the titanium oxide nanoparticles can be crosslinked with monomers such as dopamine and the like, the stability of a composite selective separation layer of the nanofiltration membrane is improved, particularly, the titanium oxide nanoparticles can show good solvent resistance in a filtering process under the condition of an organic solvent, and the effect of removing the dye can still be maintained after long-time filtering.

4. The method has simple and controllable preparation process and mild reaction condition.

Drawings

Fig. 1 is a scanning electron microscope characterization of the surface (a) of the ceramic carrier membrane and the surface (b) of the composite nanofiltration membrane according to example 1 of the present invention.

FIG. 2 is an FTIR spectrum of the surface of the ceramic carrier membrane prepared in example 1 of the present invention.

FIG. 3 is an atomic force microscope photomicrograph of the ceramic films obtained in inventive example 1 and comparative example 1.

FIG. 4 is a gel chromatography molecular weight cut-off characterization pattern of the ceramic membranes prepared in example 1 and comparative example 1 of the present invention.

Fig. 5 is a graph showing the flux recovery rate of the ceramic membranes prepared in example 1 and comparative example 1 according to the present invention during the filtration of BSA solution.

Fig. 6 shows the effect of the ceramic membrane composite nanofiltration membrane prepared in example 1 of the present invention on the rejection of congo red.

FIG. 7 is a cross-linking reaction formula in the process of preparing the nanofiltration membrane.

Detailed Description

The cross-linking reaction in the nanofiltration membrane preparation process of the invention is shown in fig. 7:

the characterization methods in the following examples are as follows:

testing the membrane separation performance:

the determination method of the permeation flux comprises the following steps: fixing a nanofiltration membrane sample with a certain area in a membrane component, performing a filtration experiment at room temperature and 0.6 MPa, and measuring the permeation flux of the nanofiltration membrane after 30 min, wherein the calculation formula is as follows:

wherein J is permeation flux, Q is volume of permeate, A is effective membrane area, and t is filtration time.

The rejection of the membrane is calculated according to the formula:

in the formula C_pAnd C_fRespectively representing the dye or salt concentration in the permeate and the stock solution.