Method for removing toluene by electrocatalytic coupling bipolar membrane

Abstract

The application discloses a method for removing toluene by electro-catalysis coupling bipolar membrane, which comprises the following steps: 1) adding toluene solution into an anode chamber and / or a cathode chamber of an electro-catalysis coupling bipolar membrane system, and adding electrolyte into the anode chamber and the cathode chamber; 2) connecting a cathode of the electro-catalysis coupling bipolar membrane system in step 1) with a negative electrode of a direct current power supply and placing the cathode in the cathode chamber, connecting an anode of the electro-catalysis coupling bipolar membrane system with a positive electrode of the direct current power supply and placing the anode in the anode chamber, and placing a bipolar membrane between the cathode chamber and the anode chamber as a diaphragm; and 3) starting the direct current power supply to perform electro-catalysis reaction, and then stopping the power supply after the reaction is completed, testing toluene content in the toluene solution after the reaction, and calculating a removal rate of toluene, so that on one hand, the method can save reagents for adjusting pH, and on the other hand, the method can improve current efficiency, accelerate a reaction rate, improve the removal rate of toluene and reduce the cost of the whole reaction system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry and industrial wastewater treatment, in particular to a method for removing toluene by electro-catalysis coupled with bipolar membrane. BACKGROUND

[0002] Steel enterprises often contain coking (including chemical production), sintering, pelletizing, ironmaking, steelmaking to rolling (hot rolling, cold rolling) and other production processes, the production process is long and complex, the types and components of raw and auxiliary materials are various, and there are many pollution links in the production process, thereby causing the characteristics of large toxicity, large quantity and complex types of pollutants of steel enterprises, and the main pollutants of steel enterprises are polycyclic aromatic hydrocarbons and heavy metals. The organic pollutants containing polycyclic aromatic hydrocarbons have poor water solubility and are difficult to be removed by means of plant or microbial degradation, and the pollution caused by the polycyclic aromatic hydrocarbons to the soil and groundwater has many characteristics such as large pollution area, large repair volume and complex repair environment. After the polycyclic aromatic hydrocarbons enter the surface water and groundwater from the soil, they seriously affect the local environmental quality and the sustainable development of economy, and even endanger human health and safety.

[0003] The bipolar membrane is a new type of ion exchange composite membrane, which is usually composed of a cation exchange layer (N type membrane) and an ion exchange layer (P type membrane). The junction of the cation exchange layer and the anion exchange layer is a water layer. Under the action of an applied direct current electric field, water in the water layer is split into H + and OH - , and passes through the cation exchange layer and the anion exchange layer respectively. Due to the combination of the anion and cation membranes, the mass transfer performance of the membrane has many new characteristics. For example, due to the discovery of the P-N junction, many new semiconductor devices have been invented. Different performance and purpose bipolar membranes can be prepared by using membrane materials with different charge densities, thicknesses and properties under different composite conditions, and it has become a relatively active research field separated from ion membranes in recent years.

[0004] Bipolar membrane electrodialysis (BPED) is an electrodialysis device for converting salt into acid and base by using the water splitting of bipolar membrane and the selective permeability of anion and cation exchange membranes. Under the action of a direct current electric field, the ions in the solution migrate directionally, the cations in the salt chamber pass through the cation membrane and are blocked by the negative layer of the bipolar membrane to remain in the base chamber, and the OH - generated by the water splitting of the bipolar membrane passes through the negative layer of the bipolar membrane and is blocked by the cation membrane to remain in the base chamber, so that the base is generated. The anions in the salt chamber pass through the anion membrane and are blocked by the positive layer of the bipolar membrane to remain in the acid chamber, and the H + generated by the water splitting of the bipolar membrane passes through the positive layer of the bipolar membrane and is blocked by the anion membrane to remain in the acid chamber, so that the acid is generated. Since the ions in the salt chamber solution all migrate outward, the desalination effect is achieved over time.

[0005] The research reports on bipolar membrane appeared since the middle of 1950s, and its development process can be divided into three stages: the first stage is from the middle of 1950s to the beginning of 1980s, which is a very slow development period of bipolar membrane, and the bipolar membrane is only directly pressed by two pieces of anion and cation exchange membranes, and has very poor performance, and the water decomposition voltage is several tens of times higher than the theoretical pressure drop, and the application research is still in the laboratory stage based on water dissociation; the second stage is from the beginning of 1980s to the beginning of 1990s, due to the improvement of the preparation technology of bipolar membrane, the single-piece bipolar membrane is successfully developed, and its performance is greatly improved, and has been successfully applied in acid and alkali preparation and desulfurization technology, and the commercial bipolar membrane appears in this stage. From the beginning of 1990s to now, it is a rapid development period of bipolar membrane, and with the in-depth study on the working process mechanism of bipolar membrane, great improvements are made from the membrane structure, membrane material and preparation process, so that the performance of the bipolar membrane is greatly improved, and the main improvement is the improvement of the contact interface of the negative membrane and the positive membrane, from the initial simple “pressing layer type” or “coating type” structure to the “single-piece type” structure which appears in the beginning of 1980s, and then the complex structure with an intermediate “catalytic layer” appears, which greatly reduces the membrane voltage. The bipolar membrane electrodialysis technology plays a unique role in optimizing the traditional industrial process and the new industrial process.

[0006] Therefore, there is an urgent need to develop new technologies or combine existing technologies with more environmentally friendly technologies to achieve efficient and green removal of pollutants from steel plants. SUMMARY

[0007] The purpose of the present application is to solve the problem that the traditional electro-catalytic oxidation technology can cause H + and OH - ions to continuously accumulate at the anode and cathode of the electrolytic cell, resulting in a decrease in the degradation efficiency of toluene, thereby providing a method for removing toluene by electro-catalytic coupling bipolar membrane, which introduces a bipolar membrane into the electro-catalytic system, thereby saving the addition of reagents for adjusting pH, improving current efficiency, accelerating the reaction rate, improving the removal rate of toluene, and reducing the cost of the entire reaction system.

[0008] In order to achieve the above-mentioned purpose, the present application provides a method for electro-catalytically oxidizing toluene, which comprises:

[0009] 1) adding a toluene solution into the anode chamber and / or the cathode chamber of the bipolar membrane electro-catalytic system, and adding an electrolyte into the anode chamber and the cathode chamber;

[0010] 2) connecting the cathode of the bipolar membrane electrocatalysis system in step 1) with the negative pole of the direct current power supply and placing it in the cathode chamber, connecting the anode of the bipolar membrane electrocatalysis system with the positive pole of the direct current power supply and placing it in the anode chamber, and placing the bipolar membrane between the cathode chamber and the anode chamber as a diaphragm;

[0011] 3) starting the direct current power supply to carry out the electrocatalysis reaction, turning off the power supply after the reaction is completed, testing the content of toluene in the toluene solution after the reaction, and calculating the removal rate of toluene.

[0012] In the above technical solution, the method for removing toluene by electrocatalysis coupled with a bipolar membrane according to the application first constructs a bipolar membrane electrocatalysis system composed of an anode chamber, a cathode chamber and a bipolar membrane in the middle, combines the electrocatalysis technology with the bipolar membrane technology, uses the bipolar membrane as the diaphragm of the electrolytic cell, and processes the toluene wastewater. Under the action of the direct current electric field, OH - ions generated by the hydrolysis of the bipolar membrane in the middle layer penetrate the negative membrane layer into the anode chamber, at the same time, H + ions generated by the hydrolysis penetrate the positive membrane layer into the cathode chamber to provide the required pH for the chain reaction of the free radical groups. The introduction of the bipolar membrane can keep the pH of the chamber where the reaction occurs unchanged, which can save the dosage of the reagent for adjusting the pH on the one hand, and improve the current efficiency, speed up the reaction rate and improve the removal rate of toluene on the other hand, so that the cost of the reaction system is reduced.

[0013] Other features and advantages of the application will be described in detail in the following specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and are used together with the following specific embodiments to explain the application, but do not constitute a limitation on the application. In the drawings:

[0015] Figure 1 is the standard curve of the toluene solution of the application;

[0016] Figure 2 a is a top view of the electrocatalysis device of the application, b is a side view of the electrocatalysis device of the application, and c is the connection between the two chambers of the electrocatalysis device of the application;

[0017] Figure 3 is a diagram of the experimental device of the application;

[0018] Figure 4 is a schematic diagram of the experimental device of the application;

[0019] Figure 5 is the ion exchange membrane used in the application, a is a cation exchange membrane, b is an anion exchange membrane, and c is a bipolar membrane;

[0020] Figure 6 a is a front view of the foam nickel electrode used in the present application, and b is a left view of the foam nickel electrode used in the present application. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory in nature and are not intended to limit the present application.

[0022] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and are understood to be encompassed by the range or value they approximate. For ranges, the endpoints are included within the range unless specifically stated otherwise. For numerical values, the endpoints are included within the range unless specifically stated otherwise. The range or value includes the endpoints.

[0023] The present application provides a method for removing toluene by electrocatalysis coupled with bipolar membrane, which comprises:

[0024] 1) adding toluene solution into the anode chamber and / or the cathode chamber of the bipolar membrane electrocatalysis system, and adding electrolyte into the anode chamber and the cathode chamber;

[0025] 2) connecting the cathode of the bipolar membrane electrocatalysis system in step 1) with the negative pole of a direct current power supply and placing it in the cathode chamber, connecting the anode of the bipolar membrane electrocatalysis system with the positive pole of the direct current power supply and placing it in the anode chamber, and placing the bipolar membrane between the cathode chamber and the anode chamber as a diaphragm;

[0026] 3) turning on the direct current power supply to carry out electrocatalysis reaction, turning off the power supply after the reaction is completed, testing the toluene content in the toluene solution after the reaction, and calculating the removal rate of toluene.

[0027] The method for removing toluene by electrocatalysis coupled with bipolar membrane in the present application introduces bipolar membrane into the traditional electrocatalysis system, which can save the addition of reagents for adjusting pH, improve the current efficiency, accelerate the reaction rate, improve the removal rate of toluene, and reduce the cost of the reaction system.

[0028] In the preferred embodiment of the present application, in order to improve the removal rate of toluene, the concentration of the toluene solution in step 1) is 150-250 mg / L.

[0029] In the preferred embodiment of the present application, in step 1), the electrolyte can be an electrolyte commonly used in the art, for example, one or two or more of sodium chloride, potassium chloride and silver chloride.

[0030] In the preferred embodiment of the present application, in order to ensure the electron transmission efficiency in the electro-catalytic system, the concentration of the electrolyte in step 1) is 5-15 g / L.

[0031] In the preferred embodiment of the present application, in order to ensure the electron transmission efficiency in the electro-catalytic system, the cathode and the anode in step 2) are one or more than two of the following: nickel foam, nickel mesh and aluminum foam.

[0032] In the preferred embodiment of the present application, in order to improve the removal rate of toluene, the thickness of the bipolar membrane in step 2) is 200-350 μm, the current efficiency is >98%, and the transport amount is >98%.

[0033] In the preferred embodiment of the present application, the effective area of the bipolar membrane in the bipolar membrane electro-catalytic system is 5.3 cm 2 .

[0034] In the preferred embodiment of the present application, in order to improve the removal rate of toluene, the conditions of the electro-catalytic reaction in step 3) include: the voltage is 11-17 V, the pH is 4-10, the temperature is 25-30°C, and the time is 40-80 min.

[0035] In the preferred embodiment of the present application, in step 3), the toluene content in the reacted toluene solution can be detected by using the conventional method in the art, for example, by spectrophotometry.

[0036] In the preferred embodiment of the present application, if the reacted toluene solution is turbid, it is filtered by using a Buchner funnel filtration device.

[0037] In the preferred embodiment of the present application, the spectrophotometry includes: 1) drawing of a toluene standard curve; and 2) obtaining the toluene content in the reacted toluene solution according to the standard curve.

[0038] In the preferred embodiment of the present application, in step 1) of the spectrophotometry, the drawing of the toluene standard curve includes: taking 8 colorimetric tubes of 50 mL, preparing toluene standard solutions with different concentration gradients, adding pure water to the mark, then sequentially adding 2.0 mL of a buffer solution, 1.0 mL of a 4-aminoantipyrine solution and 1.0 mL of a potassium ferricyanide solution, shaking, sealing and standing for color development, measuring the absorbance values of the toluene standard solutions in the 8 colorimetric tubes, drawing a curve of the absorbance values versus the toluene content, and obtaining a calibration curve regression equation and a correlation coefficient.

[0039] In the preferred embodiment of the present application, in the drawing of the toluene standard curve, the buffer solution is an ammonia chloride buffer solution with a pH of 10.7.

[0040] In a preferred embodiment of the present application, in the drawing of the toluene standard curve, the concentration of the 4-aminoantipyrine solution is 20 g / L.

[0041] In a preferred embodiment of the present application, in the drawing of the toluene standard curve, the concentration of the potassium ferricyanide solution is 80 g / L.

[0042] In a preferred embodiment of the present application, in the drawing of the toluene standard curve, the color development time is 15 min.

[0043] In a preferred embodiment of the present application, the absorbance value is the absorbance value at 510 nm wavelength.

[0044] The present application will be described in detail below through examples, but the scope of protection of the present application is not limited thereto. In the following examples, the drugs and reagents are all conventional commercially available products.

[0045] Table 1 Properties of the membranes used in the experiment

[0046] Membrane properties Anion exchange membrane Cation exchange membrane Bipolar membrane IEC (meq / g) 1.4-1.7 1.5-1.8 - Thickness (pm) 120-180 220-260 200-350 Area resistance (Ω·cm 2 )]]> 2.0-3.5 2.0-3.5 - Voltage (V) - - 1.2-202 Current efficiency (%) - - >98 Transport amount (%) 91 98 >98

[0047] Preparation of toluene solution standard curve:

[0048] 1) Prepare the buffer solution, 4-aminoantipyrine and potassium ferricyanide solution according to the requirements in the environmental standard "HJ 503-2009 Water Quality Determination of Volatile Phenol Aminoantipyrine Spectrophotometric Method";

[0049] 2) Take toluene to prepare toluene standard solution, the concentration is 10 mg / L, take 8 colorimetric tubes of 50 mL, prepare toluene standard solution with different concentration gradients, and add pure water to the mark line;

[0050] 3) Add 2.0 mL of buffer solution, 1.0 mL of 4-aminoantipyrine solution and 1.0 mL of potassium ferricyanide solution in turn, and shake well during the process of dropping, and finally seal and stand for 15 min for color development;

[0051] 4) Measure the absorbance values of the 8 colorimetric tubes at 510 nm wavelength.

[0052] 5) Draw the curve of absorbance value vs. toluene content (mg / L), i.e. toluene solution standard curve, as shown in Figure 1 .

[0053] The regression equation of the calibration curve is y = 0.1368x + 0.003, R2= 0.9987.

[0054] Example 1

[0055] (1) Accurately weigh 200 mg of toluene (analytical pure) into a 1 L volumetric flask, and dilute to the mark with pure water to obtain a 200 mg / L toluene solution;

[0056] (2) Add 100 mL of the toluene solution prepared in step (1) to each of the two electrode chambers of the electrocatalytic experimental device, and add 1 g of NaCl as an electrolyte to each of the two electrode chambers;

[0057] (3) Connect the cathode (foamed nickel electrode) of the electrocatalytic experimental device to the negative pole of a direct current power supply and place it in the cathode chamber, and connect the anode (foamed nickel electrode) to the positive pole of the direct current power supply and place it in the anode chamber. Use a bipolar membrane as the diaphragm between the two electrode chambers, and stir the liquid in the two electrode chambers with a magnetic stirrer;

[0058] (4) Turn on the power supply of the electrocatalytic experimental device, and perform electrocatalytic oxidation under the conditions of a voltage of 15 V, an initial pH of 6, and a temperature of 25°C. The reaction time is 60 min, and the power is turned off after the reaction is completed;

[0059] (5) Take out the reacted toluene solution into a beaker, and if it is turbid, filter it with a Buchner funnel filtration device. Prepare four 50 mL cuvettes, and add 1.00 mL of the reacted toluene solution to each of them. Test them by spectrophotometry in the same way as in the preparation of the calibration curve for the toluene solution. Measure the absorbance of the reacted toluene solution, and obtain the toluene content from the standard curve. Then calculate the toluene removal rate, which is denoted as B1.

[0060] Example 2

[0061] According to the method described in Example 1, the difference is that only toluene solution is added to the anode chamber in step (2). Calculate the toluene removal rate, which is denoted as B2.

[0062] Example 3

[0063] According to the method described in Example 1, the difference is that only toluene solution is added to the cathode chamber in step (2). Calculate the toluene removal rate, which is denoted as B3.

[0064] Example 4

[0065] According to the method described in Example 2, the difference is that the reaction voltage in step (4) is 11 V. Calculate the toluene removal rate, which is denoted as B4.

[0066] Example 5

[0067] According to the method described in Example 2, the difference is that the reaction voltage in step (4) is 13 V. Calculate the toluene removal rate, which is denoted as B5.

[0068] Example 6

[0069] The method described in Example 2 was implemented, except that the reaction voltage in step (4) was 17 V, and the removal rate of toluene was calculated and recorded as B6.

[0070] Example 7

[0071] The method described in Example 1 was implemented, except that the initial pH in step (4) was 4, and the removal rate of toluene was calculated and recorded as B7.

[0072] Example 8

[0073] The method described in Example 1 was implemented, except that the initial pH in step (4) was 8, and the removal rate of toluene was calculated and recorded as B8.

[0074] Example 9

[0075] The method described in Example 1 was implemented, except that the initial pH in step (4) was 10, and the removal rate of toluene was calculated and recorded as B9.

[0076] Comparative Example 1

[0077] The method described in Example 1 was implemented, except that an anion exchange membrane was used as the diaphragm of the two-pole chamber in step (3), and the removal rate of toluene was calculated and recorded as D1.

[0078] Comparative Example 2

[0079] The method described in Example 1 was implemented, except that a cation exchange membrane was used as the diaphragm of the two-pole chamber in step (3), and the removal rate of toluene was calculated and recorded as D2.

[0080] Table 2

[0081]

[0082] From Table 2, the removal rates of toluene in Examples 1-9 and Comparative Examples 1-2 can be known. By comparing the removal rates of toluene under different conditions, it can be concluded that the degradation effect of toluene solution is best when the reaction voltage is 15 V, the initial pH is 6, a bipolar membrane is used as the diaphragm, and toluene solution is added to both the two-pole chambers of the electro-catalytic device, that is, the method of the present application does not need to add a pH adjusting agent during the reaction process, and can improve the removal efficiency of toluene, is green and environmentally friendly, and saves costs.

[0083] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above-described embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

[0084] It should be further noted that any technically feasible combination of the various technical features described in the above embodiments is possible, provided that there is no contradiction, and the disclosure of the present application should be deemed to include all such technically feasible combinations.

[0085] Furthermore, any combination of the various embodiments of the present application is possible, provided that there is no contradiction, and the disclosure of the present application should be deemed to include all such technically feasible combinations.

Claims

1. A method for removing toluene using an electrocatalytically coupled bipolar membrane, characterized in that, The method includes: 1) Add toluene solution to the anode and / or cathode chambers of the bipolar membrane electrocatalytic system, and add electrolyte to both the anode and cathode chambers; 2) Connect the cathode of the bipolar membrane electrocatalytic system described in step 1) to the negative terminal of the DC power supply and place it in the cathode chamber. Connect the anode of the bipolar membrane electrocatalytic system to the positive terminal of the DC power supply and place it in the anode chamber. Place the bipolar membrane between the cathode chamber and the anode chamber as a diaphragm. 3) Turn on the DC power supply to carry out the electrocatalytic reaction. After the reaction is completed, turn off the power supply, test the toluene content in the toluene solution after the reaction, and calculate the toluene removal rate. In step 1), the concentration of the toluene solution is 150-250 mg / L; The electrolyte is sodium chloride and / or potassium chloride; The concentration of the electrolyte is 5-15 g / L; In step 2), the cathode and anode are one or more of nickel foam, nickel mesh, and aluminum foam; The bipolar film has a thickness of 200-350 μm, a current efficiency >98%, and a transport quantity >98%. In step 3), the conditions for the electrocatalytic reaction include: voltage of 11-17V, pH of 4-10, temperature of 25-30℃, and time of 40-80min.

2. The method according to claim 1, characterized in that, In step 3), the toluene content in the toluene solution after the reaction is detected by spectrophotometry.

3. The method according to claim 2, characterized in that, The spectrophotometric method includes: 1) plotting a toluene standard curve; 2) obtaining the toluene content in the toluene solution after the reaction based on the standard curve.

4. The method according to claim 3, characterized in that, In step 1), the plotting of the toluene standard curve includes: taking 8 colorimetric tubes of 50 mL each, preparing toluene standard solutions of different concentration gradients, adding pure water to the mark, then adding 2.0 mL of buffer solution, 1.0 mL of 4-aminoantipyrrolidone solution and 1.0 mL of potassium ferricyanide solution in sequence, shaking well, sealing and allowing to stand for color development, measuring the absorbance values ​​of the toluene standard solutions in the 8 colorimetric tubes, plotting the absorbance value versus toluene content curve, and obtaining the calibration curve regression equation and correlation coefficient.

5. The method according to claim 4, characterized in that, The buffer solution is an ammonia-ammonium chloride buffer solution with a pH of 10.7; The concentration of the 4-aminoantipyrrolidone solution is 20 g / L; The concentration of the potassium ferricyanide solution is 80 g / L; The color development time is 15 minutes; The absorbance value is the absorbance value at a wavelength of 510 nm.

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