Method for removing mixed dyes from wastewater

Abstract

The application provides a method for removing mixed dyes in wastewater, and relates to the technical field of water treatment. The method for removing mixed dyes in wastewater provided by the application uses hexadecyl trimethyl ammonium bromide modified iron-based MOF material as a floating agent, and adopts a froth flotation method to remove rhodamine B and crystal violet in wastewater; a bubbling device is used to generate a large number of bubbles on the liquid surface, so that the floating agent attached to the target dyes floats with the bubbles, and finally, the surface foam is removed through froth flotation, so as to reduce the concentrations of crystal violet and rhodamine B dyes in the wastewater. The method has the advantages of simple equipment, simple operation, good treatment effect, low operation cost, and lays a good foundation for the removal and recovery of dyes in wastewater, and is conducive to large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a method for removing mixed dyes from wastewater. Background Technology

[0002] With urbanization and industrialization, large amounts of wastewater are discharged into the aquatic environment, including organic and inorganic pollutants, pesticides, heavy metals, and dyes. Wastewater from the dyeing and printing industry accounts for a significant proportion of total industrial wastewater discharge, with synthetic dyes being the main pollutant. Azo dyes, such as methylene blue (MB), Congo red (CR), methyl orange (MO), and crystal violet (CV), are numerous and have become the most widely used synthetic dyes. Due to their unique chemical properties, wastewater containing these dyes typically exhibits high levels of organic toxins, strong resistance to biodegradation, photodegradation, and oxidation, and possesses potential carcinogenicity.

[0003] Currently, many technologies are applied to the treatment of organic dye wastewater, such as adsorption using composite nanofiber materials, photocatalysis, membrane adsorption, electrocoagulation adsorption, and supramolecular inclusion technology. However, these technologies all have drawbacks to varying degrees, including long treatment times, high operating costs, and secondary pollution. Therefore, developing efficient, convenient, environmentally friendly, and inexpensive dye wastewater treatment technologies is crucial. Foam separation technology, based on the principle of surface adsorption, achieves the recovery and enrichment of solutes or particles in the solution. It has advantages such as mild conditions, low energy consumption, easy scale-up, and good separation effect, making it one of the effective methods for removing dye wastewater.

[0004] Since dyes lack surface activity, flotation agents need to be added to dye wastewater for foam separation. However, existing flotation agents are not ideal for dye flotation and need improvement.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for removing mixed dyes from wastewater, so as to solve the above-mentioned technical problems.

[0007] In a first aspect, the present invention provides a method for removing mixed dyes from wastewater, which employs foam flotation to remove mixed dyes from wastewater;

[0008] The flotation agent for the foam flotation is a hexadecyltrimethylammonium bromide modified iron-based MOF material;

[0009] The mixed dyes include Rhodamine B and crystal violet.

[0010] As a further technical solution, the preparation method of the hexadecyltrimethylammonium bromide modified iron-based MOF material includes: mixing hexadecyltrimethylammonium bromide and iron-based MOF material in an aqueous solution, and preparing the hexadecyltrimethylammonium bromide modified iron-based MOF material after reaction.

[0011] As a further technical solution, the reaction temperature is 45-55℃.

[0012] As a further technical solution, the concentration of hexadecyltrimethylammonium bromide in the mixed aqueous solution is 2-10 mmol / L;

[0013] The concentration of the iron-based MOF material is 3-8 mg / mL.

[0014] As a further technical solution, the preparation method of the iron-based MOF material includes: mixing FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide, and preparing the iron-based MOF material after reaction.

[0015] As a further technical solution, the reaction temperature is 100-130℃.

[0016] As a further technical solution, the conditions for the foam flotation include: pH 3-12, working concentration of flotation agent 25-200 mg / L, and gas velocity 100-500 mL / min.

[0017] As a further technical solution, the foam flotation includes the following steps:

[0018] a. The wastewater was mixed with hexadecyltrimethylammonium bromide-modified iron-based MOF material, and then subjected to the first froth flotation to remove Rhodamine B;

[0019] b. Mix the remaining liquid after the first foam flotation with hexadecyltrimethylammonium bromide modified iron-based MOF material, and then perform a second foam flotation to remove crystal violet.

[0020] As a further technical solution, the conditions for the first froth flotation include: pH 4, working concentration of flotation agent of 50 mg / L, and gas velocity of 100-500 mL / min.

[0021] As a further technical solution, the conditions for the second foam flotation include: pH 12, working concentration of flotation agent 50 mg / L, and gas velocity 100-500 mL / min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a method for removing mixed dyes from wastewater. Using hexadecyltrimethylammonium bromide-modified iron-based MOF material as a flotation agent, the method employs foam flotation to remove Rhodamine B and crystal violet from the wastewater. A bubbling device generates a large number of bubbles on the liquid surface, allowing the flotation agent with attached target dyes to rise with the bubbles. Finally, surface foam is removed by foam flotation, thereby reducing the concentration of crystal violet and Rhodamine B dyes in the wastewater. This method features simple equipment, easy operation, good treatment effect, and low operating cost. It also lays a good foundation for the removal and recovery of dyes from wastewater, facilitating large-scale application. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a flowchart of the process for removing mixed dyes using foam flotation.

[0026] Figure 2 The effects of different pH conditions on the removal rate (a) and enrichment ratio (b) of mixed dyes in wastewater by MOF flotation agent;

[0027] Figure 3 The effect of different MOF flotation agent concentrations on the removal rate (a) and enrichment ratio (b) of rhodamine B in mixed dyes at pH=4;

[0028] Figure 4 The effect of different flotation gas velocities on the removal rate (a) and enrichment ratio (b) of Rhodamine B in mixed dyes at pH=4 is shown.

[0029] Figure 5 The effect of different MOF flotation agent concentrations on the removal rate (a) and enrichment ratio (b) of crystal violet from mixed dyes at pH=12 is shown.

[0030] Figure 6 The effect of different flotation gas velocities on the removal rate (a) and enrichment ratio (b) of crystal violet from mixed dyes at pH=12 is shown. Detailed Implementation

[0031] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] In a first aspect, the present invention provides a method for removing mixed dyes from wastewater, which employs foam flotation to remove mixed dyes from wastewater;

[0033] The flotation agent for the foam flotation is a hexadecyltrimethylammonium bromide modified iron-based MOF material;

[0034] The mixed dyes include Rhodamine B and crystal violet.

[0035] The present invention provides a method for removing mixed dyes from wastewater. Using hexadecyltrimethylammonium bromide-modified iron-based MOF material as a flotation agent, the method employs foam flotation to remove Rhodamine B and crystal violet from the wastewater. A bubbling device generates a large number of bubbles on the liquid surface, allowing the flotation agent with attached target dyes to rise with the bubbles. Finally, surface foam is removed by foam flotation, thereby reducing the concentration of crystal violet and Rhodamine B dyes in the wastewater. This method features simple equipment, easy operation, good treatment effect, and low operating cost. It also lays a good foundation for the removal and recovery of dyes from wastewater, facilitating large-scale application.

[0036] In some optional embodiments, the preparation method of the hexadecyltrimethylammonium bromide modified iron-based MOF material includes: mixing hexadecyltrimethylammonium bromide and iron-based MOF material in an aqueous solution, and preparing the hexadecyltrimethylammonium bromide modified iron-based MOF material after reaction.

[0037] In some alternative implementations, the reaction temperature may be, for example, but not limited to, 45°C, 50°C, or 55°C.

[0038] In some alternative embodiments, the concentration of hexadecyltrimethylammonium bromide in the mixed aqueous solution may be, for example, but not limited to, 2 mmol / L, 4 mmol / L, 6 mmol / L, 8 mmol / L or 10 mmol / L;

[0039] The concentration of the iron-based MOF material can be, for example, but not limited to, 3 mg / mL, 5 mg / mL, 7 mg / mL or 8 mg / mL.

[0040] In some optional embodiments, the preparation method of the iron-based MOF material includes: mixing FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide, and reacting to obtain the iron-based MOF material.

[0041] In some alternative embodiments, the reaction temperature may be, for example, but not limited to, 100°C, 110°C, 120°C, or 130°C.

[0042] In an optional embodiment, the preparation method of the iron-based MOF material includes: weighing 900.0 mg of FeCl3·6H2O and 274.7 mg of terephthalic acid, dissolving them in 60 mL of N,N-dimethylformamide, and shaking in an ultrasonic bath for 10 min. The mixture is then transferred to a reaction vessel and heated at 110 °C for 20 h. After centrifugation, the resulting solid is dispersed in ethanol at 60 °C for 3 h. Finally, the Fe-MOF is purified with ethanol and then dried in a vacuum drying oven at 110 °C for 12 h to obtain Fe-MOF (iron-based MOF).

[0043] In some optional embodiments, the conditions for the foam flotation include: pH 3-12, working concentration of flotation agent 25-200 mg / L, and gas velocity 100-500 mL / min.

[0044] In some alternative implementations, the foam flotation includes the following steps:

[0045] a. The wastewater was mixed with hexadecyltrimethylammonium bromide-modified iron-based MOF material, and then subjected to the first froth flotation to remove Rhodamine B;

[0046] b. Mix the remaining liquid after the first foam flotation with hexadecyltrimethylammonium bromide modified iron-based MOF material, and then perform a second foam flotation to remove crystal violet.

[0047] In some optional embodiments, the conditions for the first froth flotation include: pH 4, working concentration of flotation agent of 50 mg / L, and gas velocity of 100-500 mL / min.

[0048] In some optional embodiments, the conditions for the second foam flotation include: pH 12, working concentration of flotation agent of 50 mg / L, and gas velocity of 100-500 mL / min.

[0049] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0050] Example 1

[0051] Preparation method of hexadecyltrimethylammonium bromide modified iron-based MOF materials:

[0052] ①Fe-MOF nanoflotation agent: 900.0 mg of FeCl3·6H2O and 274.7 mg of terephthalic acid were weighed and dissolved in 60 mL of N,N-dimethylformamide, and the mixture was agitated in an ultrasonic bath for 10 min. The mixture was then transferred to a reaction vessel and heated at 110 °C for 20 h. After centrifugation, the resulting solid was dispersed in ethanol at 60 °C for 3 h. Finally, Fe-MOF was purified with ethanol and then dried in a vacuum drying oven at 110 °C for 12 h. Fe-MOF particles were obtained for later use.

[0053] ②Modification of Fe-MOF to obtain MOF nanoflotation agent: 0.1 g Fe-MOF was reacted vigorously at 50 °C for 4 hours with 20 mL of 5 mmol / L hexadecyltrimethylammonium bromide (CTAB) solution. After cooling to room temperature, the mixture was centrifuged and washed with double-distilled water. Finally, it was dried in a 60 °C oven for later use.

[0054] Example 2

[0055] Preparation method of hexadecyltrimethylammonium bromide modified iron-based MOF materials:

[0056] ①Fe-MOF nanoflotation agent: 900.0 mg of FeCl3·6H2O and 274.7 mg of terephthalic acid were dissolved in 60 mL of N,N-dimethylformamide and agitated in an ultrasonic bath for 10 min. The mixture was then transferred to a reaction vessel and heated at 100 °C for 20 h. After centrifugation, the resulting solid was dispersed in ethanol at 60 °C for 3 h. Finally, Fe-MOF was purified with ethanol and then dried in a vacuum drying oven at 110 °C for 12 h. Fe-MOF particles were obtained for later use.

[0057] ②Modification of Fe-MOF to obtain MOF nanoflotation agent: 0.06 g of Fe-MOF was reacted vigorously at 45 °C for 4 hours with 20 mL of 2 mmol / L hexadecyltrimethylammonium bromide (CTAB) solution. After cooling to room temperature, the mixture was centrifuged and washed with double-distilled water. Finally, it was dried in a 60 °C oven for later use.

[0058] Example 3

[0059] Preparation method of hexadecyltrimethylammonium bromide modified iron-based MOF materials:

[0060] ①Fe-MOF nanoflotation agent: 900.0 mg of FeCl3·6H2O and 274.7 mg of terephthalic acid were dissolved in 60 mL of N,N-dimethylformamide and agitated in an ultrasonic bath for 10 min. The mixture was then transferred to a reaction vessel and heated at 130 °C for 20 h. After centrifugation, the resulting solid was dispersed in ethanol at 60 °C for 3 h. Finally, Fe-MOF was purified with ethanol and then dried in a vacuum drying oven at 110 °C for 12 h. Fe-MOF particles were obtained for later use.

[0061] ②Modification of Fe-MOF to obtain MOF nanoflotation agent: 0.16 g of Fe-MOF was reacted vigorously at 55 °C for 4 hours with 20 mL of 10 mmol / L hexadecyltrimethylammonium bromide (CTAB) solution. After cooling to room temperature, the mixture was centrifuged and washed with double-distilled water. Finally, it was dried in a 60 °C oven for later use.

[0062] Using the hexadecyltrimethylammonium bromide modified iron-based MOF materials provided in Examples 1-3 as flotation agents, flotation was performed on mixed solutions containing rhodamine B and crystal violet. The results showed that the flotation agents provided in Examples 1-3 could all remove rhodamine B and crystal violet from the mixed solutions. The materials provided in Example 1 were used as flotation agents in the subsequent examples.

[0063] It should be noted that in the following embodiments or comparative examples, the specifications of the froth flotation tower are: flotation tower diameter 40-60cm and height 80-150cm.

[0064] Example 4

[0065] 150 mg / L MOF-based flotation agent was added to mixed dye wastewater (with Rhodamine B and crystal violet concentrations both set at 10 mg / L). The solution pH was adjusted to 3-12, and the gas velocity was 300 mL / min. The effect of MOF flotation agent on the removal rate of crystal violet and Rhodamine B mixed dyes by foam flotation under different pH conditions was studied. The removal rate R and enrichment ratio E were calculated. The results are as follows: Figure 2 As shown.

[0066]

[0067]

[0068] In equations (1, 2), C0, C f C r (mg / L) represent the concentrations of Rhodamine B in the injection solution, foam solution, and residual solution, respectively; Q0, Q f Q r (mL / min) represents the volume of feed solution, foam solution, and residual solution, respectively. The removal rate and enrichment ratio of crystal violet are calculated similarly.

[0069] Example 5

[0070] The pH of the mixed dye wastewater (with Rhodamine B and crystal violet concentrations both set at 10 mg / L) was adjusted to 4, and MOF-based flotation agents of 25, 50, 100, 150, and 200 mg / L were added. The solution was transferred to a flotation column, and air bubbles were introduced into the column through a distributor using an electromagnetic air pump at a velocity of 300 mL / min. The bubbles were collected from the top of the flotation column, and a residual liquid sample was taken 3 minutes after bubbling. The removal rates R of Rhodamine B and crystal violet were calculated. RB , enrichment ratio E RB The result is as follows Figure 3 As shown.

[0071] Example 6

[0072] The pH of the mixed dye wastewater (with Rhodamine B and crystal violet concentrations both set at 10 mg / L) was adjusted to 4, and 50 mg / L MOF-based flotation agent was added. The solution was transferred to a flotation tower, and air bubbles were introduced into the tower through a distributor using an electromagnetic air pump. The air velocity was adjusted to 100, 200, 300, 400, and 500 mL / min. The bubbles were collected from the top of the flotation tower, and a residual liquid sample was taken 3 minutes after bubbling. The removal rates R of Rhodamine B and crystal violet were calculated. RB , enrichment ratio E RB The result is as follows Figure 4 As shown.

[0073] Example 7

[0074] Process flow as follows Figure 1 As shown, the mixed dye wastewater is mixed with the MOF flotation agent of the present invention in an equalization tank, and then subjected to the first stage of foam flotation. After the flotation is completed, the remaining liquid is discharged to the discharge liquid storage tank, and then mixed with the MOF flotation agent of the present invention, followed by the second stage of foam flotation. After the flotation is completed, the remaining liquid is subjected to subsequent treatment (e.g., filtration, reverse osmosis, etc. to obtain pure water).

[0075] The pH of the mixed dye wastewater (with Rhodamine B and crystal violet concentrations both set at 10 mg / L) was adjusted to 4, and 50 mg / L MOF-based flotation agent was added. The solution was transferred to a flotation tower, and air bubbles were blown into the tower through a distributor using an electromagnetic air pump. The air velocity was adjusted to 200 mL / min. The blown air bubbles were collected from the top of the flotation tower. Rhodamine B in the mixed dye was removed in the first step.

[0076] The remaining liquid from the first step was collected, and MOF flotation agent was added again to adjust the pH to 12. The solution was transferred to a flotation column at flotation agent concentrations of 25, 50, 100, 150, and 200 mg / L. Bubbles were introduced into the column using an electromagnetic air pump through a distributor at a gas velocity of 300 mL / min. The bubbles were collected from the top of the flotation column, and a residual liquid sample was taken 3 minutes after bubbling. The removal rate (Rcv) and enrichment ratio (Ecv) of crystal violet were calculated. The results are as follows: Figure 5 As shown.

[0077] Example 8

[0078] Process flow as follows Figure 1 As shown, the pH of the mixed dye wastewater (with Rhodamine B and crystal violet concentrations both set at 10 mg / L) was adjusted to 4, and 50 mg / L MOF-based flotation agent was added. The solution was transferred to a flotation tower, and air bubbles were blown into the tower through a distributor using an electromagnetic air pump. The air velocity was adjusted to 200 mL / min, and the blown air bubbles were collected from the top of the flotation tower. Rhodamine B in the mixed dye was removed in the first step.

[0079] The remaining liquid from the first step was collected, and MOF flotation agent was added again to adjust the pH to 12. The solution was transferred to a flotation column at a flotation agent concentration of 50 mg / L. Bubbles were introduced into the column using an electromagnetic air pump through a distributor, with the air velocity adjusted to 100, 200, 300, 400, and 500 mL / min. The bubbles were collected from the top of the flotation column, and a residual liquid sample was taken 3 minutes after bubbling. The removal rate (Rcv) and enrichment ratio (Ecv) of crystal violet were calculated. The results are as follows: Figure 6 As shown.

[0080] Comparative Example 1

[0081] The unmodified iron-based MOF from Example 1 was used as a flotation agent for foam flotation of the mixed dyes. The unmodified MOF could adsorb the dyes, but no foam was generated during flotation, making flotation impossible.

[0082] Comparative Example 2

[0083] Hexadecyltrimethylammonium bromide was used as a flotation agent for foam flotation of mixed dyes. However, hexadecyltrimethylammonium bromide could not adsorb the dyes and therefore could not remove them.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing mixed dyes from wastewater, characterized in that, Foam flotation is used to remove mixed dyes from wastewater; The flotation agent for the foam flotation is a hexadecyltrimethylammonium bromide modified iron-based MOF material; The mixed dyes include Rhodamine B and crystal violet; The preparation method of the hexadecyltrimethylammonium bromide modified iron-based MOF material includes: mixing hexadecyltrimethylammonium bromide and iron-based MOF material in an aqueous solution, and reacting at 45-55℃ to prepare the hexadecyltrimethylammonium bromide modified iron-based MOF material; the preparation method of the iron-based MOF material includes: mixing FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide, and reacting at 100-130℃ to prepare the iron-based MOF material; The foam flotation includes the following steps: a. The wastewater was mixed with hexadecyltrimethylammonium bromide modified iron-based MOF material, and then subjected to the first froth flotation to remove Rhodamine B; b. Mix the remaining liquid after the first foam flotation with hexadecyltrimethylammonium bromide modified iron-based MOF material, and then perform a second foam flotation to remove crystal violet; The conditions for the first froth flotation include: pH 4, working concentration of flotation agent of 50 mg / L, and gas velocity of 100-500 mL / min; The conditions for the second froth flotation include: pH 12, working concentration of flotation agent 50 mg / L, and gas velocity 100-500 mL / min.

2. The method according to claim 1, characterized in that, Hexadecyltrimethylammonium bromide and iron-based MOF materials were mixed in an aqueous solution, and the concentration of hexadecyltrimethylammonium bromide in the mixed aqueous solution was 2-10 mmol / L. The concentration of the iron-based MOF material is 3-8 mg / mL.

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