Sewage treatment method based on iron-carbon filler and dithionite

Abstract

The invention discloses a sewage treatment method based on iron-carbon filler and dithionite, and belongs to the technical field of sewage treatment. The sewage treatment method based on the iron-carbon filler and the dithionite, provided by the invention, comprises the following steps: mixing the iron-carbon filler, the dithionite and wastewater, carrying out an oxidation-reduction reaction, and degrading organic pollutants in the wastewater to obtain a treated water body. According to the preparation method disclosed by the invention, the dithionite is activated through the oxidation-reduction effect of the iron-carbon filler and Fe < 2 + > / Fe < 3 + > released by the iron-carbon filler, so that strong active groups such as hydroxyl free radicals and sulfate free radicals are generated in the reaction process, and the strong active groups show strong oxidizing property due to relatively high oxidation-reduction potential; and the organic pollutants can be degraded by means of electrophilic addition, dehydrogenation, electron transfer and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a sewage treatment method based on iron-carbon filler and dithionite. Background Art

[0002] Offshore aquaculture tailwater has the characteristics of high salinity and large water volume. With the development of aquaculture, the abuse of antibiotics has become more and more serious, and they are released into the marine environment through residual feed, farmed fish excrement and human pollution. The concentration of residual antibiotics in offshore aquaculture tailwater continues to increase, seriously threatening the marine ecological environment and the sustainable development of marine aquaculture.

[0003] The pore size of ultrafiltration membranes ranges from a few nanometers to tens of nanometers, and they have excellent interception effects on particulate matter, colloids, and microorganisms in water. Currently, the ultrafiltration membranes used in water treatment are mainly made of organic polymers. Ceramic membranes have better thermal, chemical, and mechanical stability than organic membranes, and can adapt to the characteristics of low nutrition, high salinity, and large water volume in offshore aquaculture tailwater treatment. However, membrane technology has problems of severe membrane pollution and poor removal of soluble organic matter and trace pollutants during long-term treatment. Pre-membrane pretreatment is an important measure to control membrane pollution and improve water purification efficiency.

[0004] Sulfonamide antibiotics are one of the most detected antibiotics in the marine environment, and the level of sulfonamide antibiotic resistance genes is higher than that of other antibiotics. Traditional biochemical treatment technology is difficult to effectively degrade antibiotics with antibacterial properties, while advanced oxidation technology based on strong active groups can oxidize various difficult-to-degrade pollutants (mineralized into CO2, H2O and inorganic ions) and has been widely used.

[0005] In the research of advanced oxidation technology, sulfate radical system has a broad application prospect due to its high redox potential (2.8V), long half-life, and applicable pH range. At present, the most widely studied sulfate radical oxidant is persulfate, including peroxymonosulfate (PMS) and peroxydisulfate (PDS). However, persulfate is difficult to self-decompose to produce active oxygen, and usually needs to be activated to break its OO bond to produce SO4 ·- Persulfate has been shown to generate a variety of reactive oxygen species (·OH, 1 O2、SO4 ·- 、SO5 ·- In addition to persulfate, sulfite can also generate a series of active oxygen through activation. Currently, the sulfite oxidation technology mainly uses transition metal activation. Sulfite can react with transition metal ions to directly transform the valence state of sulfur element from +4 to sulfur-containing active groups in a higher valence state, accompanied by the transition metal valence state cycle process.

[0006] Zero-valent iron (ZVI) is an iron-based material that is cheap, non-toxic, and readily available. However, it will generate a passivation layer during a long reaction, which reduces the reaction activity and limits the pollutant treatment effect. For this reason, nano zero-valent iron (nZVI), acid pretreatment, weak magnetic field and other technologies have been proposed to improve the performance of ZVI. Among them, the micro-electrolysis technology formed by the composite of carbon and ZVI can improve the erosion of ZVI and overcome some of the shortcomings of both, and has received widespread attention.

[0007] The prior art discloses the preparation and application of a catalyst for the efficient mineralization of sulfonamide antibiotics based on non-free radicals. In an aqueous solution, an active composite material is used to catalyze sodium persulfate to form non-free radical active substances to participate in the efficient mineralization of sulfonamide antibiotics. Carbon nanotubes are used in the preparation of the composite material. The obtained catalyst has strong anti-interference ability and can effectively catalyze the activation of PDS and degrade sulfonamide antibiotics. However, the catalyst is very expensive and difficult to promote and use on a large scale.

[0008] For example, the prior art discloses a method for degrading sulfonamide antibiotics in wastewater using goethite composite Fe salts, which discloses a method for treating sulfonamide antibiotics using goethite and divalent iron. This method has a slow reaction speed and many subsequent processing steps, making it difficult to industrialize.

[0009] Therefore, although the prior art has studied sulfonamide wastewater, these methods all have many deficiencies in industrial application. Summary of the invention

[0010] In order to overcome at least one problem existing in the above-mentioned prior art, the object of the present invention is to provide a sewage treatment method based on iron-carbon filler and dithionite, which can remove organic pollutants in water and improve water quality.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] The invention provides a sewage treatment method based on iron-carbon filler and dithionite, comprising the following steps: mixing the iron-carbon filler, dithionite and wastewater, performing oxidation-reduction reaction, degrading organic pollutants in the wastewater, and obtaining treated water.

[0013] Preferably, the iron-carbon ratio of the iron-carbon filler is (0.7-0.9):1 by mass; more preferably (0.75-0.85):1.

[0014] Preferably, the porosity of the iron-carbon filler is ≥60%; more preferably ≥65%; for example, it may be 65%, 70%, 80% or 90%.

[0015] Preferably, the average particle size of the iron-carbon filler is 1 to 50 mm; more preferably, it is 3 to 20 mm.

[0016] Preferably, the iron-carbon filler comprises iron powder; the average particle size of the iron powder is 1 to 50 mm; more preferably 3 to 20 mm.

[0017] Preferably, the mass ratio of the iron-carbon filler to the organic pollutant is (500-100000):1; further preferably (2500-10000):1; for example, it can be 3000:1, 4000:1, 6000:1 or 8000:1.

[0018] Preferably, the molar ratio of the dithionite to the organic pollutant is (0.001-1):1; more preferably (0.0025-0.8):1; for example, it can be 0.05:1, 0.1:1, 0.3:1, 0.5:1 or 0.7:1.

[0019] Preferably, the dithionite comprises at least one of sodium dithionite, potassium dithionite or ammonium dithionite; further preferably, the dithionite is selected from sodium dithionite (Na2S2O4, DTN).

[0020] Preferably, the temperature of the redox reaction is 10-50°C; more preferably 25-40°C.

[0021] Preferably, the oxidation-reduction reaction time is ≥30 min; more preferably, it is 30 to 60 min.

[0022] Preferably, the redox reaction is carried out under stirring conditions; the stirring speed is 100 to 500 r / min; more preferably 200 to 300 r / min.

[0023] Preferably, when the redox reaction is carried out, the dissolved oxygen concentration in the wastewater is 3 to 20 mg / L; more preferably, 5 to 12 mg / L; and even more preferably, 6 to 10 mg / L.

[0024] In some embodiments of the present invention, the dissolved oxygen concentration in the wastewater is adjusted by introducing an oxygen-containing gas; the oxygen-containing gas may be oxygen-enriched air or oxygen, and the introduction of the oxygen-containing gas may increase the dissolved oxygen concentration in the wastewater.

[0025] Preferably, when the oxidation-reduction reaction is carried out, the pH value of the wastewater is 2 to 11. In some embodiments of the present invention, when the oxidation-reduction reaction is carried out, the pH value of the wastewater is 5 to 10; in some further embodiments of the present invention, when the oxidation-reduction reaction is carried out, the pH value of the wastewater is 7 to 8.

[0026] Preferably, the organic pollutants in the wastewater include sulfonamide antibiotics.

[0027] The sulfonamide antibiotics described in the present invention refer to antibiotics with para-aminobenzenesulfonamide as the basic structure.

[0028] Preferably, the sulfonamide antibiotics include sulfonamide antibiotics containing a pyrimidine ring, sulfonamide antibiotics containing an isoxazole ring, or a combination thereof; further preferably, the sulfonamide antibiotics include at least one of sulfamethoxazole, sulfamethoxazole, or sulfadiazine; further preferably, the sulfonamide antibiotics are selected from sulfamethoxazole (SMZ).

[0029] Preferably, the concentration of sulfonamide antibiotics in the wastewater is 1 to 20 μmol / L; more preferably, it is 2 to 10 μmol / L.

[0030] Preferably, the organic pollutants in the wastewater also include natural organic pollutants.

[0031] In some embodiments of the present invention, the natural organic pollutant comprises at least one of humic acid (HA), bovine serum albumin (BSA) or sodium alginate (SA).

[0032] Preferably, the concentration of natural organic pollutants in the wastewater is 5 to 40 mg / L; more preferably, it is 10 to 30 mg / L.

[0033] Preferably, the redox reaction further includes ultrafiltration treatment; the ultrafiltration treatment is to use a ceramic membrane to treat the water after the redox reaction.

[0034] Preferably, the molecular weight cutoff of the ceramic membrane is 15 to 300 kDa; more preferably, it is 30 to 100 kDa.

[0035] The beneficial effects of the present invention are as follows: the present invention uses the redox reaction of the iron-carbon filler itself and the released Fe 2+ / Fe 3+ Activate dithionite to generate hydroxyl radicals (·OH) and sulfate radicals (SO4 ·- ) and other strong active groups, which have high redox potentials and are highly oxidizing, and can degrade organic pollutants through electrophilic addition, dehydrogenation, electron transfer and other methods.

[0036] Specifically, compared with the prior art, the advantages of the present invention are as follows:

[0037] 1. The present invention uses dithionite as a source of sulfate radicals, which can react with Fe 2+ / Fe3+ Reaction to produce FeHSO3 + 、FeSO3 + Then the intermediates react with dissolved oxygen to generate a series of active oxygen (SO3 ·- 、SO5 ·- 、SO4 ·- , ·OH, etc.), thereby degrading a variety of new organic pollutants.

[0038] 2. The present invention proposes to use iron-carbon filler to activate dithionite, and further couple the system of ceramic membrane process in sewage treatment. Since it has a good purification effect in the treatment of offshore aquaculture tail water, specifically, the iron-carbon filler, as a solid catalyst, can slowly release ferrous ions during the reaction process, which are used to activate dithionite to produce a variety of strong active groups, thereby achieving efficient degradation of micropollutants. At the same time, it can remove soluble organic matter in water through electrochemical enrichment and flocculation precipitation, reduce membrane pollution load and extend membrane service life. The ceramic membrane process can remove soluble organic matter in water and flocs generated by pretreatment, thereby achieving efficient and stable water purification.

[0039] 3. The method of the present invention is carried out at room temperature and pressure and a pH value of 2 to 11. The reaction is mild, no external energy is required, it is environmentally friendly, there is no risk of secondary pollution to the environment, it is easy to operate, low cost, easy to industrialize, and has a good effect on the degradation of sulfonamide antibiotics in the environment. It has a good application prospect in the field of environmental pollution control. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The degradation rate-reaction time curve under different iron-carbon filler dosage conditions in Example 1 of the present invention.

[0041] Figure 2 Specific flux-filtration volume curve under different iron-carbon filler dosage conditions in Example 1 of the present invention.

[0042] Figure 3 The degradation rate-reaction time curve under different dithionite dosage conditions in Example 2 of the present invention.

[0043] Figure 4 The degradation rate-reaction time curve under different sulfonamide antibiotic conditions in Example 3 of the present invention.

[0044] Figure 5 This is the degradation rate-reaction time curve under different organic pollutant conditions in Example 4 of the present invention.

[0045] Figure 6 Specific flux-filtration volume curve under different organic pollutant conditions in Example 4 of the present invention.

[0046] Figure 7 This is a statistical diagram of total organic carbon under different organic pollutant conditions in Example 4 of the present invention.

[0047] Figure 8 The degradation rate-reaction time curve under different reaction atmosphere conditions in Example 5 of the present invention.

[0048] Fig. 9 The degradation rate-reaction time curves under different treatment agent system conditions in Comparative Example 1 of the present invention are shown.

[0049] Fig.10 It is the specific flux-filtration volume curve under different treatment agent system conditions in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0051] In the following examples and comparative examples, the iron-carbon ratio of the iron-carbon filler is (0.75-0.85) by mass: 1; the porosity of the iron-carbon filler is ≥65%.

[0052] It should be noted that in the following examples, in order to avoid too many factors affecting the research and analysis, the reactions were all carried out in opaque containers, but in fact, light does not affect the treatment effect.

[0053] Example 1

[0054] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0055] Take six opaque reaction containers, respectively marked as reactors 1 to 6, and add 1L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing 3.6μmol / L sulfamethazine, 30g / L NaCl, 277.5mg / L CaCl2, 20mg / L HA, 10mg / L kaolin, pH=7.5) to each reactor, then add 5-80g iron-carbon filler (average particle size of 3mm) to make its concentration 5-80g / L, and add 0.1mmol / L sodium dithionite (Na2S2O4, DTN), and carry out redox reaction at 30℃ and 300r / min mechanical stirring conditions for 30min to obtain purified water.

[0056] Specifically, 5g of iron-carbon filler (3mm) was added to reactor 1 to make its concentration 5g / L; 10g of iron-carbon filler (3mm) was added to reactor 2 to make its concentration 10g / L; 20g of iron-carbon filler (3mm) was added to reactor 3 to make its concentration 20g / L; 40g of iron-carbon filler (3mm) was added to reactor 4 to make its concentration 40g / L; 60g of iron-carbon filler (3mm) was added to reactor 5 to make its concentration 60g / L; 80g of iron-carbon filler (3mm) was added to reactor 6 to make its concentration 80g / L.

[0057] The residual concentration C1 of sulfadimethoxine in the purified water in each reactor was detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 was calculated based on the residual concentration and the initial sulfadimethoxine concentration C0. Then 150 mL of purified water in each reactor was taken, the transmembrane pressure difference was controlled at 0.06 MPa using a nitrogen bottle, and a 50 kDa ceramic membrane was used for filtration. The effluent mass m was recorded using an electronic balance and converted into a filtration volume V. The membrane flux J=V / At was calculated based on the filtration area A and the time t, and the membrane specific flux J'=J / J0 was calculated in combination with the initial flux J0.

[0058] The results are shown in Table 1. Figure 1 and Figure 2 shown. Figure 1 The degradation rate-reaction time curve under different iron-carbon filler dosage conditions in Example 1 of the present invention; Figure 2 Specific flux-filtration volume curve under different iron-carbon filler dosage conditions in Example 1 of the present invention.

[0059] Table 1 Effect of iron-carbon filler dosage on water treatment effect

[0060] Iron-carbon filler dosage (g / L) 5 10 20 40 60 80 Sulfadimethoxine degradation rate (%) 84 86 89 94 95 99 End point membrane flux 0.87 0.92 0.88 0.85 0.95 0.96

[0061] From Table 1, Figure 1 and Figure 2It can be seen that when the dosage of iron-carbon filler increases from 5g / L to 80g / L, the degradation rate of sulfamethazine increases from 84% to 99% within 30min. This indicates that the increase in the dosage of iron-carbon filler significantly promotes the degradation of sulfonamide antibiotics in this system, and can activate sodium dithionite to produce active groups through spontaneous redox reaction of iron-carbon and dissolution of iron ions, thereby effectively degrading sulfamethazine. When the dosage of iron-carbon filler increases from 5g / L to 80g / L, after filtering 150mL of treated water sample, the endpoint membrane flux increases from 0.87 to 0.96, indicating that the increase in the dosage of iron-carbon filler can dissolve more iron ions, remove macromolecular organic matter through flocculation, and alleviate membrane pollution.

[0062] Example 2

[0063] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0064] Five opaque reaction containers were taken, respectively marked as reactors 1 to 5, and 1 L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing 3.6 μmol / L sulfamethazine, 30 g / L NaCl, 277.5 mg / L CaCl2, 20 mg / L HA, 10 mg / L kaolin, pH = 7.5) was added to each reactor, followed by adding 20 g of iron-carbon filler (average particle size of 3 mm) to make its concentration 20 g / L, and adding 0.05 to 0.8 mmol / L sodium dithionite (Na2S2O4, DTN), and carrying out redox reaction at 30°C and 300 r / min mechanical stirring conditions for 30 min to obtain purified water.

[0065] Specifically, sodium dithionite was added to reactor 1 to make its concentration 0.05 mmol / L; sodium dithionite was added to reactor 2 to make its concentration 0.1 mmol / L; sodium dithionite was added to reactor 3 to make its concentration 0.2 mmol / L; sodium dithionite was added to reactor 4 to make its concentration 0.4 mmol / L; sodium dithionite was added to reactor 5 to make its concentration 0.8 mmol / L.

[0066] The residual concentration C1 of sulfadimethoxine in the water body after purification in each reactor is detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 is calculated according to the residual concentration and the initial sulfadimethoxine concentration C0.

[0067] The results are shown in Table 2 and Figure 3 shown. Figure 3 The degradation rate-reaction time curve under different sodium dithionite dosage conditions in Example 2 of the present invention.

[0068] Table 2 Effect of sodium dithionite dosage on water treatment effect

[0069] Sodium dithionite dosage (mmol / L) 0.05 0.1 0.2 0.4 0.8 Sulfadimethoxine degradation rate (%) 69 89 88 86 84

[0070] From Table 2 and Figure 3 It can be seen that when the sodium dithionite is 0.05mmol / L, fewer active groups are generated in the system and the degradation rate of sulfonamide antibiotics is low. When the dosage of sodium dithionite increases to 0.1mmol / L and above, the sulfonamide antibiotics reach more than 84%, indicating that the addition of sodium dithionite helps to enhance the oxidation effect of the system and thus efficiently degrade sulfonamide antibiotics.

[0071] Example 3

[0072] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0073] Take three opaque reaction containers, respectively marked as reactors 1 to 3, and add 1L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing 3.6μmol / L of different types of sulfonamide antibiotics, 30g / L NaCl, 277.5mg / L CaCl2, 20mg / L HA, 10mg / L kaolin, pH=7.5) to each reactor, then add 20g of iron-carbon filler (average particle size of 3mm) to make its concentration 20g / L, and add 0.1mmol / L sodium dithionite, and carry out redox reaction at 30℃ and 300r / min mechanical stirring conditions for 30min to obtain purified water.

[0074] Specifically, reactor 1 contained 3.6 μmol / L sulfamethoxazole; reactor 2 contained 3.6 μmol / L sulfamethoxazole; and reactor 3 contained 3.6 μmol / L sulfadiazine.

[0075] The residual concentration C1 of sulfadimethoxine in the water body after purification in each reactor is detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 is calculated according to the residual concentration and the initial sulfadimethoxine concentration C0.

[0076] The results are shown in Table 3 and Figure 4 shown. Figure 4 The degradation rate-reaction time curve under different sulfonamide antibiotic conditions in Example 3 of the present invention.

[0077] Table 3 Effect of sulfonamide antibiotics on water treatment effect

[0078] Types of sulfonamide antibiotics Sulfadimethoxine Sulfamethoxazole Sulfadiazine Sulfadimethoxine degradation rate (%) 87 84 75

[0079] From Table 3 and Figure 4It can be seen that the iron-carbon micro-electrolysis activated sodium dithionite system has a good degradation effect on different types of sulfonamide antibiotics, and the degradation rate can be maintained above 75%.

[0080] Example 4

[0081] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0082] Take three opaque reaction containers, respectively marked as reactors 1 to 3, and add 1L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing 3.6μmol / L sulfamethazine, 30g / L NaCl, 277.5mg / L CaCl2, 10mg / L kaolin, pH=7.5) to each reactor, then add 20g iron-carbon filler (average particle size of 3mm) to make its concentration 20g / L, add 0.1mmol / L sodium dithionite, and add different types of organic pollutants, and carry out redox reaction at 30℃ and 300r / min mechanical stirring conditions for 30min to obtain purified water.

[0083] Specifically, 20 mg / L humic acid (HA) was added to reactor 1, 20 mg / L bovine serum albumin (BSA) was added to reactor 2, and 20 mg / L sodium alginate (SA) was added to reactor 3.

[0084] The residual concentration C1 of sulfadimethoxine in the purified water in each reactor was detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 was calculated based on the residual concentration and the initial sulfadimethoxine concentration C0. Then 150 mL of purified water in each reactor was taken, and the transmembrane pressure difference was controlled at 0.06 MPa using a nitrogen bottle, and filtered using a 50 kDa ceramic membrane. The effluent mass m was recorded using an electronic balance and converted into a filtration volume V. The membrane flux J=V / At was calculated based on the filtration area A and time t, and the membrane specific flux J'=J / J0 was calculated in combination with the initial flux J0. And the total organic carbon analyzer was used to detect the total organic carbon of the water sample before treatment (raw water), the water sample after pretreatment, and the ultrafiltration effluent.

[0085] The results are shown in Table 4 and Figures 5 to 7 shown. Figure 5 The degradation rate-reaction time curve under different organic pollutant conditions in Example 4 of the present invention; Figure 6 Specific flux-filtration volume curve under different organic pollutant conditions in Example 4 of the present invention; Figure 7It is a statistical graph of total organic carbon under different organic pollutant conditions in Example 4 of the present invention, wherein "Feed" represents raw water, i.e. simulated offshore aquaculture tail water, "Fe-C@DTN" represents water sample treated with iron-carbon micro-electrolysis activated sodium dithionite, and "Membrane" represents ultrafiltration effluent.

[0086] Table 4 Effect of types of organic pollutants on water treatment effects

[0087]

[0088] From Table 4 and Figures 5 to 7 It can be seen that the iron-carbon micro-electrolysis activated sodium dithionite system can still maintain a degradation rate of more than 78% for sulfonamide antibiotics under the interference of different types of natural organic pollutants. The total organic carbon degradation rates of the three tail waters added with humic acid, bovine serum albumin and sodium alginate are 81.4%, 82.7% and 75%, respectively. It can be seen that the iron-carbon micro-electrolysis activated sodium dithionite coupled with the ceramic membrane process can effectively remove macromolecular organic matter in the water body. Comparing the total organic carbon of the raw water and the pretreated water samples, the total organic carbon removal rates of the three water samples by pretreatment were 71.4%, 51.0% and 30.8%, respectively. It can be seen that the pretreatment can effectively remove humic organic pollutants and protein organic matter. Comparing the total organic carbon of the pretreated water samples and the ultrafiltration effluent, the total organic carbon removal rates of the three water samples in the ultrafiltration process were 10%, 31.7% and 44.2%, respectively. It can be seen that the ultrafiltration process can effectively intercept protein organic matter and polysaccharide organic matter, and keep the total organic carbon of the effluent below 2 mg / L. After pretreatment of the three tail waters, the endpoint membrane specific fluxes were 0.92, 0.46, and 0.32, respectively. This shows that the iron-carbon micro-electrolysis activated sodium dithionite system can effectively treat humic organic matter, improve water quality, and alleviate membrane pollution.

[0089] Example 5

[0090] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0091] Take three opaque reaction containers, respectively marked as reactors 1 to 3, and add 1L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing 3.6μmol / L sulfamethazine, 30g / L NaCl, 277.5mg / L CaCl2, 20mg / L HA, 10mg / L kaolin, pH=7.5) to each reactor, then add 20g iron-carbon filler (average particle size of 3mm) to make its concentration 20g / L, and add 0.1mmol / L sodium dithionite, and carry out redox reaction at 30℃, 300r / min mechanical stirring and different gas purging conditions (air, oxygen, nitrogen) for 30min to obtain purified water.

[0092] Specifically, reactor 1 was unchanged as a blank control and reacted in an air atmosphere (Oxygen-free, dissolved oxygen = 6.8 mg / L), oxygen (O2, dissolved oxygen = 16.7 mg / L) was introduced into reactor 2, and nitrogen (N2, dissolved oxygen = 0.3 mg / L) was introduced into reactor 3.

[0093] The residual concentration C1 of sulfadimethoxine in the water body after purification in each reactor is detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 is calculated according to the residual concentration and the initial sulfadimethoxine concentration C0.

[0094] The results are shown in Table 5 and Figure 8 shown. Figure 8 The degradation rate-reaction time curve under different reaction atmosphere conditions in Example 5 of the present invention.

[0095] Table 5 Effect of reaction atmosphere on water treatment effect

[0096] Reaction atmosphere Air oxygen Nitrogen Dissolved oxygen concentration (mg / L) 6.8 16.7 0.3 Sulfadimethoxine degradation rate (%) 87 70 31

[0097] From Table 5 and Figure 8 It can be seen that the effect of controlling dissolved oxygen in water can be achieved by purging with oxygen and nitrogen. When oxygen purging is used to create oxygen-rich conditions, the surface of the iron-carbon filler is easily passivated, making it difficult to effectively activate sodium dithionite, reducing the degradation rate of sulfadimethoxine to 70%. When nitrogen purging is used to create anoxic conditions, the degradation rate of sulfadimethoxine is 31%, while the degradation rate of the blank control is more than 87%, indicating that dissolved oxygen has a significant effect on the degradation of antibiotics by iron-carbon micro-electrolysis activation of sodium dithionite.

[0098] Comparative Example 1

[0099] A method for treating offshore aquaculture tail water, the specific steps are as follows:

[0100] Take three opaque reaction containers, marked as reactors 1 to 3, and add 1L of simulated offshore aquaculture tail water containing sulfonamide antibiotics (containing sulfamethazine 3.6 μmol / L, NaCl 30 g / L, CaCl2 277.5 mg / L, HA 20 mg / L, kaolin 10 mg / L, pH = 7.5) to each reactor, then add different treatment agent systems, and carry out redox reaction at 30°C and 300 r / min mechanical stirring conditions for 30 minutes to obtain purified water.

[0101] Specifically, 20 g of iron-carbon filler (average particle size of 3 mm) was added to reactor 1, recorded as Fe-C; 20 g of iron-carbon filler (average particle size of 3 mm) and 0.1 mmol / L sodium dithionite were added to reactor 2, recorded as Fe-C / DTN; 20 g of iron-carbon filler (average particle size of 3 mm) and 0.1 mmol / L persulfate were added to reactor 3, recorded as Fe-C / PS.

[0102] The residual concentration C1 of sulfadimethoxine in the purified water in each reactor was detected, and the degradation rate of sulfadimethoxine C'=(C0-C1) / C0 was calculated based on the residual concentration and the initial sulfadimethoxine concentration C0. Then 150 mL of purified water in each reactor was taken, the transmembrane pressure difference was controlled at 0.06 MPa using a nitrogen bottle, and a 50 kDa ceramic membrane was used for filtration. The effluent mass m was recorded using an electronic balance and converted into a filtration volume V. The membrane flux J=V / At was calculated based on the filtration area A and the time t, and the membrane specific flux J'=J / J0 was calculated in combination with the initial flux J0.

[0103] The results are shown in Table 6 and Figures 9-10 shown. Fig. 9 The degradation rate-reaction time curves under different treatment agent system conditions in Comparative Example 1 of the present invention; Fig.10 It is the specific flux-filtration volume curve under different treatment agent system conditions in Comparative Example 1 of the present invention.

[0104] Table 6 Effect of treatment agent system on water treatment effect

[0105] Treatment agent system Iron Carbon Filler Iron-carbon filler + sodium dithionite Iron-carbon filler + persulfate Sulfadimethoxine degradation rate (%) 61 89 85 End point membrane flux 0.83 0.92 0.89

[0106] From Table 6 and Figures 9-10 Compared with the single iron-carbon filler system and the iron-carbon filler activated persulfate system, the iron-carbon filler activated sodium dithionite system has a higher sulfamethoxazole degradation rate and endpoint membrane specific flux. It can be seen that the iron-carbon micro-electrolysis activated sodium dithionite system can effectively treat humic organic matter, improve water quality conditions, and alleviate membrane pollution.

[0107] In the embodiment of the present invention, sodium dithionite (Na2S2O4, DTN) is used as a source of sulfate radicals, which can react with Fe 2+ / Fe 3+ Reaction to produce FeHSO3 + 、FeSO3 + Then the intermediates react with dissolved oxygen to generate a series of active oxygen (SO3 ·- 、SO5 ·- 、SO4 ·- , ·OH, etc.), thereby degrading a variety of new organic pollutants.

[0108] Specifically, in the embodiment of the present invention, sodium dithionite is activated by iron-carbon filler, and the system further coupled with ceramic membrane process has a good purification effect in sewage treatment, especially in the treatment of offshore aquaculture tail water. The iron-carbon filler acts as a solid catalyst and can slowly release ferrous ions during the reaction to activate sodium dithionite to produce a variety of strong active groups, thereby achieving efficient degradation of micropollutants. At the same time, it can remove soluble organic matter in water through electrochemical enrichment and flocculation precipitation, reduce membrane pollution load and extend membrane service life. The ceramic membrane process can remove soluble organic matter in water and flocs generated by pretreatment, thereby achieving efficient and stable water purification.

[0109] The method of the embodiment of the present invention is carried out under normal temperature and pressure and a pH value of 2 to 11. The reaction is mild, no external energy is required, it is environmentally friendly, there is no risk of secondary pollution to the environment, it is easy to operate, low cost, easy to industrialize, and has a good effect on the degradation of sulfonamide antibiotics in the environment. It has a good application prospect in the field of environmental pollution control.

[0110] In summary, the present invention uses the redox reaction of the iron-carbon filler itself and the released Fe 2+ / Fe 3+ Activate dithionite to generate hydroxyl radicals (·OH) and sulfate radicals (SO4 ·- ) and other strong active groups, which have high redox potentials and are highly oxidizing, and can degrade organic pollutants through electrophilic addition, dehydrogenation, electron transfer and other methods.

Claims

1. A sewage treatment method based on iron-carbon filler and dithionite, characterized in that: The method comprises the following steps: mixing iron-carbon filler, dithionite and waste water, carrying out oxidation-reduction reaction, degrading organic pollutants in the waste water, and obtaining treated water.

2. The sewage treatment method according to claim 1, characterized in that: The iron-carbon ratio of the iron-carbon filler is (0.7-0.9):1 by mass; and / or, the porosity of the iron-carbon filler is ≥ 60%; And / or, the average particle size of the iron-carbon filler is 1 to 50 mm.

3. The sewage treatment method according to claim 1, characterized in that: The mass ratio of the iron-carbon filler to the organic pollutant is (500-100000):1; And / or, the molar ratio of the dithionite to the organic pollutant is (0.001-1):

1.

4. The sewage treatment method according to claim 1, characterized in that: The temperature of the redox reaction is 10 to 50°C; And / or, the redox reaction time is ≥30 min; And / or, the redox reaction is carried out under stirring; the stirring speed is 100-500 r / min.

5. The sewage treatment method according to claim 1, characterized in that: When the oxidation-reduction reaction is carried out, the dissolved oxygen concentration in the wastewater is 3 to 20 mg / L; And / or, when the oxidation-reduction reaction is carried out, the pH value of the wastewater is 2-11.

6. The sewage treatment method according to claim 1, characterized in that: The organic pollutants in the wastewater include sulfonamide antibiotics.

7. The sewage treatment method according to claim 6, characterized in that: The sulfonamide antibiotics include sulfonamide antibiotics containing a pyrimidine ring, sulfonamide antibiotics containing an isoxazole ring, or a combination thereof; And / or, the concentration of sulfonamide antibiotics in the wastewater is 1-20 μmol / L.

8. The sewage treatment method according to claim 6, characterized in that: The organic pollutants in the wastewater also include natural organic pollutants; the natural organic pollutants include at least one of humic acid, bovine serum albumin or sodium alginate.

9. The sewage treatment method according to claim 1, characterized in that: The redox reaction is followed by ultrafiltration treatment; the ultrafiltration treatment is to use a ceramic membrane to treat the water body after the redox reaction.

10. The sewage treatment method according to claim 9, characterized in that: The molecular weight cut-off of the ceramic membrane is 15 to 300 kDa.

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