CN114699930B - A kind of polyaza-heterocyclic amide membrane for dye wastewater treatment and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of membrane separation and treatment of dye wastewater, in particular to a polynitrogen heterocyclic amide membrane used for dye wastewater treatment and a preparation method thereof. The method uses cyclic monomer azacycloalkane as a water phase monomer, and adopts interfacial polymerization to prepare the polyazacycloamide film. The present invention adopts a new type of cyclic molecular azacycloalkane as a water-phase monomer, loads it on the surface of the base film, and then reacts with trimesoyl chloride to carry out interfacial polymerization to construct polyaza with stable structure and high selectivity. Cyclic amide membrane. The polynitrogen heterocyclic amide membrane prepared by the present invention realizes the effective separation of dyes/salts due to the enlarged inner pores of the nitrogen heterocyclic rings and retains the characteristic of intercepting macromolecular dyes.

Description

A kind of polyaza-heterocyclic amide membrane for dye wastewater treatment and preparation method thereof

technical field

The invention belongs to the field of membrane separation and treatment of dye wastewater, in particular to a polynitrogen heterocyclic amide membrane used for dye wastewater treatment and a preparation method thereof.

Background technique

Due to the rapid growth of population, urbanization and industrialization, the discharge of textile dye wastewater is increasing rapidly. Dye pollutants can not only endanger human health by polluting freshwater resources, but also have harmful effects on aquatic organisms. Therefore, how to efficiently remove dye pollutants is imminent. So far, traditional techniques, such as adsorption, distillation, flocculation, biodegradation, advanced oxidation, etc., have been widely used in the treatment of dye wastewater. Although these methods are effective in dye removal, a major challenge is the low selectivity to dye/salt mixtures, which affects dye purification and recovery as well as inorganic salt recycling. Compared with the above technologies, loose nanofiltration membranes are widely used in the dye wastewater treatment separation system due to their molecular size similar to that of most dyes, showing high separation coefficient, high flux and environmental friendliness. More importantly, unlike conventional dense NF membranes, a major feature of loose NF membranes is high divalent salt (such as Na ₂ SO ₄ ) permeability, which makes it possible to separate dye/salt mixtures.

At present, the construction methods of loose nanofiltration membranes mainly include blending-phase inversion, surface chemical modification, biomimetic material deposition, and interfacial polymerization. Interfacial polymerization is a method for industrially synthesizing large-area films. It mainly uses piperazine as the monomer in the water phase and trimesoyl chloride as the monomer in the oil phase to prepare polypiperazineamide nanofiltration membranes. However, this type of polyamide membrane has a high rejection rate for both dyes and polyvalent inorganic salts, and it is difficult to effectively separate the dye/salt mixture. In view of this, by using or introducing long-chain branched monomers, polyamine monomers, and hydroxyl ring monomers to fine-tune the cross-linking degree of the film and increase the pore size and porosity, the separation selectivity of dyes/salts is improved. However, the high reactivity of amine monomers makes it easy to form dense polyamides and it is difficult to obtain through pores, so the increase in membrane flux is not obvious. In comparison, the advantages of hydroxyl cyclic monomers are significant: a polyester film with a lower degree of crosslinking is formed, and the pores in the self-ring can increase the free volume and pore connectivity of the film, which is helpful for the dye/salt Improved separation selectivity. However, the weak acid and alkali resistance of this type of membrane limits its application in dye wastewater treatment.

Contents of the invention

The purpose of the present invention is to provide a polyazine heterocyclic amide membrane for dye wastewater treatment and its preparation method, which can better solve the acid and alkali resistance of the membrane and effectively separate the dye/salt mixture.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A polyazine heterocyclic amide membrane used for dye wastewater treatment is obtained through the following preparation method: using cyclic monomer azacycloalkane as a water phase monomer, and preparing the polynitrogen heterocyclic amide membrane by interfacial polymerization.

The solvent of the azacycloalkane is an aqueous solution, and the mass concentration of the aqueous solution is 0.05-0.2wt%.

The pH of the aqueous solution of azacycloalkane is preferably 7-14, more preferably controlled at 12-14.

The n-hexane solvent of trimesoyl chloride is used as the oil phase monomer, and the mass concentration is 0.05-0.2 wt %; the mass ratio of the aqueous solution of azacycloalkane to the n-hexane solution of trimesoyl chloride is 1:1-3.

Preferably, the azacycloalkane is 1,4,7-triazacyclononane, 1,4,8,11-tetraazacyclotetradecane or 1,4,7,10,13- Pentaazacyclopentadecane.

The molecular formula of described azacycloalkane is as follows:

First immerse the aqueous solution of azacycloalkane on the surface of the base film for 3-10 minutes; then add the oil phase monomer solution to react for 0.5-2 minutes, more preferably 0.5-1 minutes, and then heat-treat at 50-80° C. for 1-5 minutes.

The base membrane can be one of polysulfone, polyethersulfone, polyacrylonitrile or Kevlar base membrane.

Specifically, the preparation method of the polyazine heterocyclic amide membrane for the treatment of dye wastewater comprises the following steps:

(1) The base film is fixed in the membrane module, and the aqueous solution of azacycloalkane with a mass fraction of 0.05-0.2wt% is immersed on the surface of the base film. After immersion for 3-10 minutes, the excess aqueous solution of azacycloalkane is removed until There is no obvious water stain on the membrane;

(2) Pour the trimesoyl chloride-n-hexane solution with a mass fraction of 0.05-0.2wt% onto the surface of the above-mentioned membrane, and the reaction time is 0.5-2min;

(3) After the reaction is finished, the surface of the membrane is washed with n-hexane solvent for 10-30 seconds, and then heat-treated at 50-80° C. for 1-5 minutes to obtain a polyazine heterocyclic amide membrane.

In the invention, the novel cyclic monomer azacycloalkane is used as a water phase monomer to construct a polyazine heterocyclic amide membrane with stable structure and high selectivity. Azacycloalkanes are a class of piperazine-like cyclic compounds with secondary amine groups. The presence of multiple secondary amine groups allows this type of compound to undergo interfacial polymerization with trimesoyl chloride to form a structurally stable polyamide film, and The amide bond formed is more stable than the ester bond. In addition, compared with piperazine, azacycloalkane has its unique advantages in the design and development of high dye/salt selectivity films: as the number of carbon or nitrogen atoms on the azacycloalkane ring increases, the azacycloalkane itself The increase of pores in the annulus can increase the free volume in the film and the connectivity in the pores in principle, and improve the permeability of the composite membrane. At the same time, its increased steric hindrance and reduced solubility will weaken the azacycloalkane Reactivity, to a certain extent, reduces the crosslinking degree of the film to obtain more and larger through-hole nanopores, forming microchannels that facilitate the penetration of hydrated ions. In addition, it retains the characteristics of retaining macromolecular dyes, and then Achieve efficient dye/salt separation. In addition, by changing the interfacial polymerization conditions, for example, as the pH of the nitrogen heterocycle-water phase monomer increases, the crosslinking degree of the polynitrogen heterocycle amide membrane decreases, thereby improving the flux of the composite membrane. In addition, the present invention controls the monomer concentration and the interfacial polymerization reaction time to optimize the interfacial reaction conditions so as to increase the porosity of the membrane, thereby optimizing the separation performance of the composite membrane.

In the method for preparing the polynitrocyclic amide membrane of the present invention, the azacycloalkane does not need to be pretreated, and the aqueous solution of different types of polynitrocyclic rings is directly loaded on the surface of the base membrane such as a polysulfone membrane, and then the oil phase solution is added to carry out interfacial polymerization reaction , the polyazine heterocyclic amide membrane for dye wastewater treatment can be prepared.

Compared with the prior art, the present invention has the following advantages:

The present invention adopts a new type of cyclic molecular azacycloalkane as a water-phase monomer, loads it on the surface of the base film, and then reacts with trimesoyl chloride to carry out interfacial polymerization to construct polyaza with stable structure and high selectivity. Cyclic amide membrane. The polynitrogen heterocyclic amide membrane prepared by the present invention realizes the effective separation of dyes/salts due to the enlarged inner pores of the nitrogen heterocyclic rings and retains the characteristic of intercepting macromolecular dyes.

Description of drawings

Fig. 1 is the physical picture of the polyazine heterocyclic amide film prepared respectively in embodiment 3, embodiment 4 and embodiment 7.

Detailed ways

The technical scheme of the present invention is described below with specific examples, but protection scope of the present invention is not limited to this: Embodiment 1

A preparation method for a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7-triazacyclononane with a mass fraction of 0.18 wt%, adjust the pH to 12, and soak the above aqueous solution on the surface of the polysulfone membrane for 5 Minutes later, the excess 1,4,7-triazacyclononane aqueous solution was removed until there were no obvious water spots on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above film, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polyazine heterocyclic amide membrane, labeled as TFC-1 membrane.

Example 2

A preparation method for a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7-triazacyclononane with a mass fraction of 0.18 wt%, adjust the pH to 13, and soak the above aqueous solution on the surface of the polysulfone membrane for 5 Minutes later, the excess 1,4,7-triazacyclononane aqueous solution was removed until there were no obvious water spots on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above film, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrocyclic amide membrane, labeled as TFC-2 membrane.

Example 3

A preparation method for a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7-triazacyclononane with a mass fraction of 0.18 wt%, adjust the pH to 14, and soak the above aqueous solution on the surface of the polysulfone membrane for 5 Minutes later, the excess 1,4,7-triazacyclononane aqueous solution was removed until there were no obvious water spots on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above film, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrocyclic amide membrane, labeled as TFC-3 membrane.

Example 4

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,8,11-tetraazacyclotetradecane with a mass fraction of 0.12 wt%, adjust the pH to 12, and immerse the above aqueous solution in the polysulfone After 5 minutes on the membrane surface, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above-mentioned membrane, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrogen heterocyclic amide membrane, labeled as TFC-4 membrane.

Example 5

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,8,11-tetraazacyclotetradecane with a mass fraction of 0.12 wt%, adjust the pH to 13, and immerse the above aqueous solution in the polysulfone After 5 minutes on the membrane surface, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above-mentioned membrane, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrogen heterocyclic amide membrane, labeled as TFC-5 membrane.

Example 6

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,8,11-tetraazacyclotetradecane with a mass fraction of 0.12 wt%, adjust the pH to 14, and immerse the above aqueous solution in the polysulfone After 5 minutes on the membrane surface, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above-mentioned membrane, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polyazine heterocyclic amide membrane, labeled as TFC-6 membrane.

Example 7

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7,10,13-pentaazacyclopentadecane with a mass fraction of 0.10 wt%, adjust the pH to 13, and immerse the above aqueous solution in After 5 minutes on the surface of the polysulfone membrane, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the film, and the reaction time is 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polyazine heterocyclic amide membrane, labeled as TFC-7 membrane.

Example 8

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7,10,13-pentaazacyclopentadecane with a mass fraction of 0.10 wt%, adjust the pH to 14, and immerse the above aqueous solution in After 5 minutes on the surface of the polysulfone membrane, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the film, and the reaction time is 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrocyclic amide membrane, labeled as TFC-8 membrane.

Comparative example 1

Preparation of PIP-TMC polyamide nanofiltration membrane:

1) The polysulfone membrane is fixed in the membrane module, and the piperazine aqueous solution with a mass fraction of 0.10 wt% is impregnated on the surface of the polysulfone membrane. At this time, the pH of the aqueous phase monomer solution is 11. After immersion for 5 minutes, the excess piperazine The aqueous solution of oxazine was removed until there was no obvious water spot on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above film, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polypiperazine amide membrane, marked as a PIP/TMC-TFC membrane.

Comparative example 2

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take an aqueous solution of 1,4,7-triazacyclononane with a mass fraction of 0.18wt%, at this time, the pH of the aqueous phase monomer solution is 9, and soak the above aqueous solution After 5 minutes on the surface of the polysulfone membrane, remove the excess 1,4,7-triazacyclononane aqueous solution until there is no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above film, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrogen heterocyclic amide membrane, marked as comparative example 2 TFC membrane;

Comparative example 3

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take a 1,4,8,11-tetraazacyclotetradecane aqueous solution with a mass fraction of 0.12 wt%, and the pH of the aqueous phase monomer solution is 10 at this time, and the After the above aqueous solution is immersed on the surface of the polysulfone membrane for 5 minutes, the excess aqueous phase solution is removed until there is no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the above-mentioned membrane, and react for 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polynitrogen heterocyclic amide membrane, which is marked as Comparative Example 3 TFC membrane.

Comparative example 4

A method for preparing a polyazine heterocyclic amide membrane for dye wastewater treatment, comprising the following specific steps:

1) Fix the polysulfone membrane in the membrane module, take a 1,4,7,10,13-pentaazacyclopentadecane aqueous solution with a mass fraction of 0.10 wt%, and the pH of the aqueous phase monomer solution is 12 at this time, After immersing the above aqueous solution on the surface of the polysulfone membrane for 5 minutes, the excess aqueous phase solution was removed until there was no obvious water stain on the membrane;

2) Pour a trimesoyl chloride-n-hexane solution with a mass fraction of 0.1 wt% onto the surface of the film, and the reaction time is 1 min;

3) After the reaction, the surface of the membrane was washed with n-hexane solvent for 30 seconds, and then heat-treated at 80° C. for 3 minutes to obtain a polyazine heterocyclic amide membrane, which is marked as comparative example 4TFC membrane.

Under room temperature conditions, test the water flux of the polyazine heterocyclic amide membrane prepared in Examples 1-8 and the amide membrane prepared in Comparative Examples 1-4 and the removal rate of dyes and inorganic salts in dye wastewater, the results are shown in Table 1 and 2. The test is carried out at room temperature in a cross-flow device with a pressure of 0.4MPa.

Table 1 is the water flux of the polyazine heterocyclic amide membrane prepared by Examples 1-8 and the polypiperazine amide membrane prepared by Comparative Example 1-4 and the retention rate of the dye in the dye wastewater by the nanofiltration membrane reported in the literature, data The errors are all within the reasonable error range.

Table 1

It can be seen from the table that, compared with the traditional polypiperazine polyamide membrane and the nanofiltration membrane reported in the literature, the polyazine heterocyclic amide membrane maintains a high retention rate of the dye, and the water flux is the traditional one. Polypiperazine polyamide membrane 5-10 times, showing excellent dye removal ability.

Table 2 shows the water flux of the polyazine heterocyclic amide membranes prepared in Examples 1-8 and the amide membranes prepared in Comparative Examples 1-4 and the retention rate of the nanofiltration membranes reported in the literature to inorganic salts in dye wastewater, and the data error average within a reasonable margin of error.

Table 2

As can be seen from the table, compared with the traditional polypiperazine amide membrane and the nanofiltration membrane reported in the literature, under the condition of not adjusting the pH of the aqueous phase monomer, the rejection rate of the polyazine heterocyclic amide membrane to the divalent salt is higher High, so the separation of divalent salts and dye molecules cannot be achieved. After adjusting the pH of the monomer solution in the aqueous phase, the rejection rate of the polyazine heterocyclic amide membrane to the inorganic salt was greatly reduced, showing excellent dye/salt separation ability.

Claims (6)

1. a kind of preparation method of the polynitrocyclic amide film that is used for dye wastewater treatment, it is characterized in that, take cyclic monomer azacycloalkane as aqueous phase monomer, adopt interfacial polymerization to prepare described polynitrocyclic amide film; the azacycloalkane is 1,4,7-triazacyclononane, 1,4,8,11-tetraazacyclotetradecane or 1,4,7,10,13-penta Azacyclopentadecane; the pH of the aqueous solution of azacycloalkane is 12-14. 2. the preparation method of the polynitrocyclic amide membrane that is used for dye wastewater treatment as claimed in claim 1, is characterized in that, the solvent of described azacycloalkane is an aqueous solution, and the mass concentration of its aqueous solution is 0.05-0.2 wt%. 3. the preparation method of the polyazine heterocyclic amide film that is used for dye wastewater treatment as claimed in claim 2, is characterized in that, is the oil phase monomer with the n-hexane solvent of trimesoyl chloride, and mass concentration is 0.05-0.2 wt%; the mass ratio of the aqueous solution of azacycloalkane to the n-hexane solution of trimesoyl chloride is: 1:1-3. 4. the preparation method of the polyazaheterocyclic amide film that is used for dye wastewater treatment as claimed in claim 1 is characterized in that, the aqueous solution of azacycloalkane is soaked 3-10min on base film surface earlier; Then add oily phase The monomer solution was reacted for 0.5-2min, followed by heat treatment at 50-80°C for 1-5min. 5. The polynitrocyclic amide film obtained by any one of the preparation methods of claims 1-4. 6. the application of the polyazine heterocyclic amide film obtained by the preparation method according to claim 5 in the treatment of dye wastewater.

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