Electrochemical-ferric iron activated sodium hydrogen sulfite system and application thereof

Abstract

The invention belongs to the field of antibiotic pollution treatment, and particularly relates to an electrochemistry-ferric iron activated sodium hydrogen sulfite system and application thereof. An electrochemistry-ferric iron activated sodium hydrogen sulfite system comprises an anode, a cathode, an electrolyte solution and an external circuit, and the electrolyte solution is sodium sulfate, sodium hydrogen sulfate and ferric sulfate. According to the method, four active substances including. OH, SO4.-, 1O2 and O2.-contained in an Electro activation S (IV) system are adopted, continuous generation of strong oxidation active substances is promoted by adjusting electrolyte components, the pH value and the like, the degradation effect on antibiotics in an existing method is improved, and the method has good application potential on actual wastewater.

Description

Technical Field

[0001] The present invention belongs to the field of antibiotic pollution control, and particularly relates to an electrochemical-ferric ion activated sodium bisulfite system and its application. Background Art

[0002] Antibiotics are hydrophilic, have a relatively long half-life and antibacterial properties, and exist in the water environment for a long time, resulting in the production of antibacterial genes by pathogenic microorganisms, which can cause potential significant harm to animals, plants, humans and even the entire ecosystem. On the one hand, the Electro system can degrade organic pollutants through direct oxidation, and on the other hand, it can also generate a large number of active substances through indirect oxidation to attack antibiotic molecules, achieving the purpose of effectively oxidizing and decomposing organic matter. However, the single Electro system has some drawbacks, such as low stability and excessive power consumption.

[0003] Sulfite (S(Ⅳ)) is a typical reducing agent and oxygen-containing salt. S(Ⅳ) in the Fe / O 2 / S(Ⅳ) system for air treatment can generate sulfite radicals (SO 3 ·- ), and under sufficient oxygen conditions, it can be further converted into sulfate radicals (SO 4 ·- ) and hydroxyl radicals (·OH) and other active substances. Most advanced oxidation technologies have high economic costs and environmental risks. Chinese Patent CN112811676A discloses a method for degrading antibiotic wastewater using a three-dimensional electrode of geopolymer particles, and its electrolyte uses sulfate and persulfate (Na 2 S 2 O 8 ), but Na 2 S 2 O 8 not only has a high price, but also has a great impact on the environment. Moreover, during the degradation process, excessive particle electrodes will deposit at the bottom of the electrolytic cell, resulting in an increase in short-circuit current.

[0004] In the existing methods for degrading antibiotics using advanced oxidation technologies, they all have good degradation effects in antibiotic solutions, but when applied to natural waters, due to the complex composition of impurities in natural waters, the degradation effect will drop sharply.

[0005] In summary, there is an urgent need for a method for degrading antibiotics that is applicable to natural waters, has low economic costs, is safe and pollution-free. Summary of the Invention

[0006] Purpose of the invention: The present invention proposes an electrochemical-ferric iron activated sodium bisulfite system and its application, the purpose of which is to solve the problems of high economic cost, environmental pollution of degradation products and unsuitability for natural water bodies in existing methods of degrading antibiotics.

[0007] Technical solution:

[0008] The invention provides an electrochemical-ferric iron activated sodium bisulfite system, which comprises an anode, a cathode, an electrolyte solution and an external circuit, wherein the electrolyte solution is sodium sulfate, sodium bisulfate and ferric sulfate.

[0009] Furthermore, the molar ratio of the sodium sulfate, sodium bisulfate and ferric sulfate is 3.5-4.5:1.8-2.2:0.2-0.3.

[0010] Furthermore, the pH of the electrolyte solution is 3-4.

[0011] Furthermore, the current of the external circuit is 10-20 mA.

[0012] The present invention also proposes that the electrochemical-ferric iron activated sodium bisulfite system is further applied in the degradation of antibiotics in wastewater, and the application steps are:

[0013] 1) adding sodium sulfate, sodium bisulfate and ferric sulfate into the antibiotic wastewater in a molar ratio, mixing them evenly, and adjusting the pH of the mixed solution to 4-4.5 to obtain a mixed solution;

[0014] 2) Under the condition of continuous mixing, the anode and cathode are inserted into the mixed solution, the current of the external circuit is adjusted to 10-15 mA, and the power-on time is 20-70 minutes to degrade the antibiotics.

[0015] Furthermore, the antibiotic wastewater contains antibiotics and natural water impurities, wherein the antibiotic is one of sulfamethoxazole, metronidazole or tetracycline, and the natural water impurities are Cl - , HCO 3 - 、SO 4 2- 、NO 3 - , one or more of HA.

[0016] Beneficial effects:

[0017] The present invention adopts the electro-activated S(Ⅳ) system containing OH, SO 4 ·- , 1 O 2 and O 2 ·-Four active substances, among which ·OH plays a major role, and S(Ⅳ) is non-toxic, easily available and inexpensive. At the same time, Electro is green and environmentally friendly, easy to operate, can realize the recycling of S(Ⅳ), and can also realize the effective recycling of Fe 3+ / Fe 2+ , improving the utilization rate of S(Ⅳ). The degradation method of the present invention promotes the continuous generation of strong oxidizing active substances by adjusting the electrolyte components, pH value, etc. Compared with low-dose Fe 2 (SO 4 ) 3 , the removal rate of SMX degradation is increased by 22.01%. Compared with high-dose Na 2 SO 4 , the removal rate of SMX degradation is increased by 24.57%. Compared with a relatively high pH value, the removal rate of SMX degradation is increased by 26.83%. And the COD removal rate of the system of the present invention applied to actual wastewater can reach 80.25%. The system and degradation method of the present invention improve the degradation effect of antibiotics in the existing methods and have good application potential for actual wastewater. Description of the Drawings

[0018] Figure 1 COD values in domestic sewage were measured at different times. Detailed Embodiments

[0019] To further illustrate the technical means adopted by the present invention and its effects, the present invention will be further described below in conjunction with examples and drawings. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0020] S(Ⅳ) is a common reducing agent. Existing technologies show that S(Ⅳ) generally generates SO 3 ·- through UV, transition metal ions and their oxides, and electrochemical (Electro) activation. Under the condition of sufficient oxygen, SO 3 ·- further undergoes a chain reaction to generate SO 4 ·- , ·OH, superoxide anion (O 2 ·- ) and singlet oxygen ( 1 O 2 ). Under the condition of sufficient oxygen, some transition metal ions (such as Fe 0 , Co(Ⅱ), Ni(Ⅱ), Fe(Ⅱ), Cr(Ⅵ) and Ce(Ⅳ), etc.) can effectively activate S(Ⅳ) to generate SO 4 ·-. However, the utilization efficiency is not high. The present invention proposes a ternary system (Electro / Fe(III) / S(IV) system) that synergistically activates sodium bisulfite by electro-oxidation and ferric ions. The Electro-activated S(IV) system contains ·OH, SO 4 ·- , 1 O 2 and O 2 ·- four active substances. Among them, ·OH plays a major role. Moreover, S(IV) is non-toxic, easily available, and inexpensive. At the same time, Electro is green and environmentally friendly, and easy to operate. The entire process can not only solve the disadvantages of the narrow pH application range of the traditional electro-Fenton system and the difficulty in recycling iron ions, but also realize the recycling of S(IV), and can also achieve the effective recycling of Fe 3+ / Fe 2+ , improving the utilization rate of S(IV). The degradation method of the present invention promotes the continuous generation of strong oxidizing active substances by adjusting the electrolyte components, pH value, etc., realizes the purpose of efficiently degrading antibiotics in natural water bodies, and improves the treatment efficiency of antibiotic wastewater.

[0021] Example 1

[0022] Add 20 40 mL, 100 mg L -1 sulfamethoxazole (SMX) into a beaker, and add 0 mM, 5 mM, 10 mM, 20 mM of Cl - , NO 3 - , SO 4 2- , HCO 3 - , and 0 mM, 10 mM, 20 mM, 40 mM of humic acid (HA), and then add 4.5 mM of Na 2 SO 4 , 2.2 mM of NaHSO 3 and 0.3 mM of Fe 2 (SO 4 ) 3 . Turn on the magnetic stirrer to mix the solution evenly. Quickly add H 2 SO 4(0.1M) and / or NaOH (0.1M) was used to adjust the initial pH value of the solution to a constant of 4. A platinum anode and a graphite cathode were placed in a beaker, and the current was adjusted to the required 10 mA. The power supply device of the external circuit was started, and timing was immediately started. The power-on time was 60 min. Samples of 2 mL were taken at certain time intervals and filtered through a 0.45 μm microporous filter membrane. 2 mL of methanol (MeOH) was added to quench the reaction, the absorbance was measured, and its concentration and removal rate were calculated. All experiments were repeated at least 2 times, and the relative error was calculated.

[0023] Sulfamethoxazole (SMX) was determined by high performance liquid chromatography (HPLC). The mobile phase of SMX was 0.1% methanol aqueous solution: methanol = 80:20 (V:V), and the flow rate was 1.0 mL min -1 , and the detection wavelength was 275 nm. The corresponding concentration was calculated according to the standard curve drawn based on the relationship between the peak area and the concentration. The calculation results are shown in Table 1 and Table 2.

[0024] The degradation rate of the organic pollutant was calculated by the following formula.

[0025]

[0026] In the formula: R is the pollutant removal rate (removal efficiency, %); C0 is the concentration of the organic pollutant at the initial moment (mg L-1); C is the concentration of the organic pollutant at a certain sampling moment (mg L-1).

[0027] Table 1 Removal rate of sulfamethoxazole degradation (%)

[0028]

[0029]

[0030] Table 2 Removal rate of sulfamethoxazole degradation with HA added in the system (%)

[0031] 0 mg / L 10 mg / L 20 mg / L 40 mg / L HA 90.52 88.25 86.56 85.65

[0032] It can be seen from Table 1 and Table 2 that when Cl - , NO 3 - , SO 4 2- , HA were added to the system, the removal rate of SMX degradation could reach over 82%. When HCO 3 - was added to the system, the removal rate of SMX degradation was slightly lower, but still higher than 76%.

[0033] Example 2

[0034] In 16 40 mL, 100 mg L-1 Metronidazole (MTZ) was added to a beaker, and 0 mM, 5 mM, 10 mM, and 20 mM of Cl - , NO 3 - and HCO 3 - were added respectively, as well as 0 mM, 1 mg / L, 3 mg / L, and 5 mg / L of HA. Then, 4.0 mM of Na 2 SO 4 , 2.0 mM of NaHSO 3 and 0.25 mM of Fe 2 (SO 4 ) 3 were added. The magnetic stirrer was turned on to mix the solution evenly. H 2 SO 4 (0.1 M) and / or NaOH (0.1 M) were quickly added to the solution to adjust the initial pH value of the solution to be constantly 4. The platinum anode and graphite cathode were placed in the beaker, and the required current was adjusted to 10 mA. The power supply device of the external circuit was started, and timing was immediately started. The power-on time was 20 min. Samples of 2 mL were taken at certain time intervals and filtered through a 0.45 μm microporous filter membrane. 2 mL of MeOH was added to quench the reaction, the absorbance was measured, and its concentration and removal rate were calculated. All experiments were repeated at least 2 times, and their relative errors were calculated.

[0035] The absorbance of metronidazole was measured with a UV-visible spectrophotometer at a detection wavelength of 318 nm. Its corresponding concentration was calculated according to the standard curve drawn based on the relationship between absorbance and concentration, and the degradation rate of organic pollutants was calculated. The calculation results are shown in Tables 3 and 4.

[0036] Table 3 Removal rate of MTZ degradation (%)

[0037] <![CDATA[Cl - > <![CDATA[NO 3 - > <![CDATA[HCO 3 - > 0 mM 86.74 89.95 91.05 5 mM 99.66 91.75 76.52 10 mM 98.35 92.05 72.42 20 mM 99.22 90.63 70.85

[0038] Table 4 Removal rate of MTZ degradation with HA added to the system (%)

[0039] 0 mg / L 2.5 mg / L 5 mg / L 10 mg / L HA 90.66 78.52 76.44 73.85

[0040] It can be seen from Tables 3 and 4 that when Cl - , NO 3 - were added to the system, it slightly promoted the degradation of MTZ, and the removal rate reached more than 86%. When 20 mM of Cl - was added to the system, the removal rate of MTZ degradation was as high as 99.22%. When HCO 3 - , HA were added to the system, the removal rate of SMX degradation was slightly lower, but still higher than 70%.

[0041] Example 3

[0042] Twenty 40 mL portions of 100 mg / L -1 tetracycline (TC) were placed in a beaker, and 0 mM, 2.5 mM, 5 mM, and 10 mM of Cl - , NO 3 - , SO 4 2- , and HCO 3 - were added respectively. In addition, 0 mM, 2.5 mg / L, 5 mg / L, and 10 mg / L of HA were added, and then 4.5 mM of Na 2 SO 4 , 1.8 mM of NaHSO 3 , and 0.2 mM of Fe 2 (SO 4 ) 3 were added. The magnetic stirrer was turned on to mix the solution evenly. H 2 SO 4 (0.1 M) and / or NaOH (0.1 M) were quickly added to the solution to adjust the initial pH value of the solution to be constantly 3.5. A platinum anode and a graphite cathode were placed in the beaker, the required current was adjusted to 10 mA, the power supply device of the external circuit was started, and timing was immediately started. The power-on time was 50 min. Samples of 2 mL were taken at certain time intervals and filtered through a 0.45 μm microporous membrane, 2 mL of MeOH was added to quench the reaction, the absorbance was measured, and its concentration and removal rate were calculated. All experiments were repeated at least 2 times, and their relative errors were calculated.

[0043] The absorbance of TC was measured with a UV-visible spectrophotometer at a detection wavelength of 356 nm, and its corresponding concentration was calculated according to the standard curve plotted based on the relationship between absorbance and concentration. The degradation rate of the organic pollutant was calculated, and the calculation results are shown in Tables 5 and 6.

[0044] Table 5 Removal rate of TC degradation (%)

[0045] <![CDATA[Cl - > <![CDATA[NO 3 - > <![CDATA[SO 4 2- > <![CDATA[HCO 3 - > 0 mM 89.55 85.84 85.86 89.05 2.5 mM 85.32 85.02 83.47 85.36 5 mM 82.66 84.33 82.24 74.42 10 mM 80.54 83.99 75.55 76.88

[0046] Table 6 Removal rate of TC degradation with HA added to the system (%)

[0047] 0 mg / L 2.5 mg / L 5 mg / L 10 mg / L HA 89.69 76.24 75.72 70.06

[0048] It can be seen from Tables 5 and 6 that when Cl - , NO 3 - were added to the system, the removal rate of TC degradation reached over 80%. When HCO 3 - , SO4 2- The removal rate of HA-degraded TC is slightly lower, but still higher than 70%.

[0049] From the data in Tables 1 to 6, it can be seen that the Electro / Fe(III) / S(IV) system and degradation method proposed in the present invention can adapt to different natural water body components and have a certain buffering capacity.

[0050] Comparative Example 1

[0051] Add 40 mL of 100 mg / L SMX to a beaker, add 10 mM of Cl -1 respectively, and then uniformly add 4.0 mM of Na - SO 2 SO 4 、2.0 mM of NaHSO 3 and 0.1 mM of Fe 2 (SO 4 ) 3 . Turn on the magnetic stirrer to mix the solution evenly. Quickly add H 2 SO 4 (0.1 M) and / or NaOH (0.1 M) to adjust the initial pH value of the solution to be constantly 4.0. Place the platinum anode and graphite cathode in the beaker, adjust the required current to 10 mA, start the power supply device of the external circuit, start timing immediately, and the power-on time is 60 min. Take 2 mL of samples at certain time intervals, filter them with a 0.45 μm microporous filter membrane, add 2 mL of MeOH to quench the reaction, measure the absorbance, and calculate its concentration and removal rate. All experiments are repeated at least 2 times, and the relative error is calculated.

[0052] The calculated removal rate of degraded SMX is 64.55%, which is much lower than the removal rate of 86.56% in Example 1 with the addition of 10 mM Cl - (see Table 1). The removal rate of Example 1 is increased by 22.01% compared with Comparative Example 1, indicating that the addition amount of Fe 2 (SO 4 ) 3 affects the final removal rate, that is, Fe(III) can participate in the activation of S(IV). When the content is low, the active substances such as ·OH generated are not enough to degrade SMX in the system.

[0053] Comparative Example 2

[0054] Add 40 mL of 100 mg / L SMX to a beaker, add 10 mM of SO -1 respectively, and then uniformly add 5.0 mM of Na 4 2- SO 2 SO 4, 2.0 mM of NaHSO 3 and 0.2 mM of Fe 2 (SO 4 ) 3 , turn on the magnetic stirrer to mix the solution evenly. Quickly add H 2 SO 4 (0.1 M) and / or NaOH (0.1 M) to adjust the initial pH value of the solution to be constantly 4.0. Put the platinum anode and graphite cathode into the beaker, adjust the required current to 10 mA, start the power supply device of the external circuit, start timing immediately, and the power-on time is 60 min. Take 2 mL of samples at certain time intervals and filter them with a 0.45 μm microporous filter membrane, add 2 mL of MeOH to quench the reaction, measure the absorbance, and calculate its concentration and removal rate. All experiments are repeated at least 2 times, and the relative error is calculated.

[0055] After calculation, the removal rate of degraded SMX is 60.85%, which is much lower than the removal rate of 85.42% when adding 10 mM SO 4 2- in Example 1 (see Table 1). The removal rate of Example 1 is increased by 24.57% compared with that of Comparative Example 2. It shows that too high addition ratio (too high concentration) of Na 2 SO 4 in the electrolyte of the system affects the final removal rate of degraded SMX. Maybe because SO 4 2- as the electrolyte, too high concentration will cause the interaction between sulfate and sodium ions to increase, resulting in the decrease of conductivity in the solution and the reduction of the removal rate of SMX.

[0056] Comparative Example 3

[0057] Add 100 mg L -1 of SMX in 40 mL into the beaker, add 10 mM of HCO 3 - respectively, and then add 4.5 mM of Na 2 SO 4 , 2.2 mM of NaHSO 3 and 0.3 mM of Fe 2 (SO 4 ) 3 , turn on the magnetic stirrer to mix the solution evenly. Quickly add H 2 SO 4Adjust the initial pH value of the solution to 5.0 with HCl (0.1M) and / or NaOH (0.1M). Place the platinum anode and graphite cathode in a beaker, adjust the required current to 10 mA, start the power supply device of the external circuit, immediately start timing, and the power-on time is 60 min. Take 2 mL of samples at certain time intervals, filter them with a 0.45 μm microporous filter membrane, add 2 mL of MeOH to quench the reaction, measure the absorbance, and calculate its concentration and removal rate. All experiments are repeated at least 2 times, and the relative error is calculated.

[0058] The calculated removal rate of SMX degradation is 50.05%, which is much lower than the removal rate of 76.88% in Example 1 with the addition of 10 mM HCO 3 - (see Table 1). The removal rate of Example 1 is increased by 26.83% compared with that of Comparative Example 3. It shows that the pH value of the system affects the final removal rate of SMX degradation. HCO 3 - will provide a weak alkaline environment, which will inhibit the degradation of SMX in the system. If the pH value in the system is relatively high, it will cause iron ions to precipitate more easily, which is not conducive to the activation of S(IV) and the generation of active substances.

[0059] Example 4

[0060] To study the effect of the Electro / Fe(III) / S(IV) system on the organic matter content in actual wastewater, domestic sewage from a certain university is selected as the research object. Measure the COD in the domestic sewage. Take 1 mL of the test solution at 0, 2, and 6 h respectively, filter it with a 0.45 μm filter membrane, dilute it 20 times, and then add it to the Hach COD reagent. After mixing evenly, when the temperature of the Hach digestion furnace rises to 165 °C, digest the Hach COD reagent tube with the test sample added for 15 min. After the digestion is completed, wait for the digestion tube to cool to room temperature, and then use the Hach COD analyzer to measure its COD value. The results are shown in Figure 1 as follows.

[0061] From Figure 1 it can be seen that when the reaction proceeds to 2 h, the removal rate of COD is 54%, and when it reaches 6 h, the removal rate of COD is 80.25%. It shows that the system and degradation method of the present invention have good application potential for actual wastewater.

[0062] In summary, the components of natural water usually affect the degradation of pollutants by the Electro / Fe(III) / S(IV) system. The present invention adds Cl - 、HCO 3 - 、SO 4 2- 、NO 3 -HA was used to simulate natural water bodies. By adjusting the electrolyte components, pH value, etc., the continuous generation of strongly oxidizing active substances was promoted, the degradation effect of antibiotics in the existing methods was improved, and it had good application potential for actual wastewater.

[0063] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An electrochemical-ferric iron activated sodium bisulfite system, comprising an anode, a cathode, an electrolyte solution and an external circuit, characterized in that: The electrolyte solution is sodium sulfate, sodium bisulfate and ferric sulfate.

2. The electrochemical-ferric iron activated sodium bisulfite system according to claim 1, characterized in that: The molar ratio of the sodium sulfate, sodium bisulfate and ferric sulfate is 3.5-4.5:1.8-2.2:0.2-0.

3.

3. The electrochemical-ferric iron activated sodium bisulfite system according to claim 1, characterized in that: The pH value of the electrolyte solution is 3-4.

4. The electrochemical-ferric iron activated sodium bisulfite system according to claim 1, characterized in that: The current of the external circuit is 10-20 mA.

5. Application of the electrochemical-ferric iron activated sodium bisulfite system in degradation of antibiotics in wastewater as claimed in any one of claims 1 to 4.

6. The use according to claim 5, characterized in that: The application steps are: 1) adding sodium sulfate, sodium bisulfate and ferric sulfate into antibiotic wastewater in a molar ratio, mixing them evenly, and adjusting the pH of the mixed solution to 4-4.5 to obtain a mixed solution; 2) Under the condition of continuous mixing, the anode and cathode are inserted into the mixed solution, the current of the external circuit is adjusted to 10-15 mA, and the power-on time is 20-70 minutes to degrade the antibiotics.

7. The use according to claim 6, characterized in that: Antibiotic wastewater contains antibiotics and natural water impurities, wherein the antibiotic is one of sulfamethoxazole, metronidazole or tetracycline, and the natural water impurities are Cl - 、HCO3 - 、SO4 2- 、NO3 - , one or more of HA.

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