Method for treating triazinone wastewater through electrocatalytic oxidation

Abstract

The invention belongs to the technical field of pesticide industry production wastewater treatment, and particularly relates to a method for treating triazinone wastewater through electrocatalytic oxidation. The treatment process comprises the following steps: (1) adding a complex microbial inoculant into the triazinone production wastewater, and carrying out anaerobic culture to obtain degraded triazinone production wastewater; (2) heating the degraded triazinone production wastewater, and distilling out fractions under a stirring condition to obtain distilled wastewater; (3) carrying out electrocatalytic oxidation on the distilled wastewater by using ultraviolet light in combination with electrocatalysis to obtain wastewater containing pivalic acid; (4) under the condition of 25-30 DEG C, adding an extracting solution into the wastewater containing the pivalic acid to obtain an extracting solution layer and a water layer; (5) adjusting the pH of the water layer to be neutral with liquid caustic soda, and performing reduced pressure distillation to obtain recycled water; and carrying out reduced pressure distillation on the extract layer, condensing and recovering the extract, and simultaneously obtaining kettle residues containing pivalic acid. The treatment method provided by the invention can reduce the amount of COD and ammonia nitrogen, and improve the recovery rate of pivalic acid at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of pesticide industrial wastewater treatment, and particularly relates to a method for electrocatalytic oxidation treatment of triazinone wastewater. Background Art

[0002] Triazinone is an organic compound and an important intermediate for synthesizing the herbicide metribuzin. The wastewater generated during the production of triazinone has several special characteristics, which make its treatment difficult. If directly discharged without proper treatment, it will have a significant negative impact on the environment: (1) Large discharge volume: Triazinone is a widely used chemical intermediate, and its production scale is usually large, so the amount of wastewater generated is also relatively large. The discharge of a large amount of wastewater will increase the load on sewage treatment facilities, possibly exceeding the treatment capacity of local sewage treatment plants, resulting in some untreated or incompletely treated wastewater entering natural water bodies. (2) High chemical oxygen demand (COD) concentration: A high COD value indicates that the wastewater contains a large amount of organic matter, which requires more oxygen to decompose, increasing the difficulty and cost of biological treatment. When this high-COD wastewater is discharged into water bodies such as rivers and lakes, it will consume the dissolved oxygen in the water, possibly causing aquatic organisms to die of hypoxia and disrupting the ecological balance. (3) High salt content: The reaction and separation steps in the production process of triazinone may introduce a certain amount of inorganic salts, such as sodium chloride and sodium sulfate. Wastewater with a high salt content will affect the activity of microorganisms, reduce the efficiency of biological treatment, and even inhibit the growth of some microorganisms, making biological treatment methods infeasible. The salt may also affect the soil structure, leading to soil salinization and affecting the growth of crops. (3) High content of compounds that are difficult to biodegrade: Triazinone and its derivatives may be organic compounds with complex and stable structures, which are not easily decomposed by conventional microbial communities. The accumulation of these difficult-to-degrade substances in the environment may be transmitted through the food chain and ultimately pose a threat to human health. (4) Strong odor: The wastewater may contain volatile organic compounds (VOCs), which not only have a strong odor but may also be harmful to human health.

[0003] During the industrial production process of triazinone, wastewater containing various organic substances is generated, including pivalic acid. As a valuable chemical substance, pivalic acid plays an important role in some industrial applications, such as being used as a raw material for solvents, coatings, plastics, and pharmaceuticals. Therefore, from the perspectives of environmental protection and economy, it is very meaningful to separately separate and recover pivalic acid. In the prior art, organic solvents are usually added for extraction to remove all the organic substances in the triazinone industrial production wastewater. However, this method will remove pivalic acid and other organic pollutants together and cannot recover pivalic acid, without paying attention to the problem of separately separating, recovering, and reusing pivalic acid in triazinone production wastewater. Summary of the Invention

[0004] The object of the present invention is to provide a method for electrocatalytic oxidation treatment of triazinone wastewater, by which the COD in the triazinone production wastewater can be treated and the total organic matter concentration in the triazinone production wastewater can be effectively reduced.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for electrocatalytic oxidation treatment of triazinone wastewater, comprising the following steps:

[0007] (1) Adding a composite bacterial agent to the triazinone production wastewater and anaerobically culturing to obtain the degraded triazinone production wastewater;

[0008] (2) Heating the degraded triazinone production wastewater and distilling off the distillate under stirring conditions to obtain the distilled wastewater;

[0009] (3) Using ultraviolet light combined with electrocatalysis to electrocatalytically oxidize the distilled wastewater to obtain the wastewater containing pivalic acid;

[0010] (4) At 25 - 30 °C, adding an extraction liquid to the wastewater containing pivalic acid, stirring for 20 - 40 min, standing for 30 - 40 min, separating the liquid, and separating out the extraction liquid layer; then repeating the extraction of the water layer once in the same way; combining the extraction liquid layers obtained from the two extractions;

[0011] (5) Adjusting the pH of the water layer to neutral with liquid caustic soda and performing vacuum distillation to obtain recycled water; performing vacuum distillation on the extraction liquid layer, condensing and recovering the extraction liquid, and simultaneously obtaining the residue containing pivalic acid.

[0012] Furthermore, the conditions for electrocatalytic oxidation in step (3) are: constant current: 6 A, anode: ruthenium-iridium electrode, cathode: titanium electrode, electrolysis time: 1 - 3 h.

[0013] Furthermore, in step (3), a xenon lamp with a power of 300 - 350 W is used to provide ultraviolet light source irradiation.

[0014] The present invention first heats up the wastewater by heating and evaporates about 20% of the low-boiling organic matters and water under stirring conditions. This process can remove a part of the volatile organic compounds, such as solvents or other low-molecular-weight organic matters, thereby initially reducing the COD in the wastewater. The strong oxidizing free radicals generated by the electrochemical reaction are used to decompose the organic pollutants in the wastewater. In this process, a ruthenium-iridium electrode is selected as the anode and a titanium electrode is selected as the cathode, which can produce efficient oxidation at a lower voltage.

[0015] Furthermore, the conditions for anaerobic culture in step (1) are: anaerobic culture at 30 - 35 °C for 6 - 8 days.

[0016] Further, the composite bacterium agent in the step (1) includes Bacillus subtilis, Bacillus cereus, and Bacillus amyloliquefaciens.

[0017] Further, the dosage of Bacillus subtilis in the step (1) is 10 6 ~10 7 CFU / mL; the dosage of Bacillus cereus is 10 7 ~10 8 CFU / mL; the dosage of Bacillus amyloliquefaciens is 10 8 ~10 9 CFU / mL.

[0018] During the experiment, it was found that although the combination of ultraviolet light and electrocatalysis can reduce the amount of COD, the recovery rate of pivalic acid is not ideal. In the present invention, the triazinone production wastewater is first pretreated with a composite bacterium, which can improve the recovery rate of pivalic acid. The analysis is that the composite bacterium removes or transforms complex organic matters and other interfering substances in the wastewater through biodegradation and metabolic activities during the pretreatment stage, thereby creating more favorable conditions for the subsequent treatment of ultraviolet light combined with electrocatalysis. The wastewater may also contain unreacted raw materials, by-products, solvents and other organic matters, which may compete with pivalic acid for adsorption sites, form coprecipitation or cocrystallization, affecting the separation and recovery of pivalic acid. The composite bacterium can biodegrade these organic pollutants and reduce their interference with pivalic acid.

[0019] Further, 18 - 22 (v / v)% of the distillate is distilled out under stirring conditions in the step (2).

[0020] Further, 50 g of the extractant is added to 1000 g of the wastewater containing pivalic acid in the step (4).

[0021] Further, the extractant layer is distilled under reduced pressure at 55 - 57 °C in the step (5).

[0022] Further, the extractant is toluene and cyclohexane with a volume ratio of (1.3 - 1.5):1.

[0023] After sequential fermentation treatment and ultraviolet light combined with electrocatalysis treatment, the present invention selects toluene and cyclohexane as the extractant for liquid - liquid extraction, which can further improve the recovery rate of pivalic acid. The ratio of toluene and cyclohexane will affect the selectivity for other impurities in the system. By optimizing the ratio, pivalic acid can be selectively extracted, reducing the interference of other impurities and improving the purity and recovery rate of pivalic acid.

[0024] Bacillus subtilis was purchased from Shanghai Microbial Preservation Center, product number: SHMCC D10486.

[0025] Bacillus cereus, purchased from Beijing Zhongke Quality Inspection Biotechnology Co., Ltd., product number: ZKCC25597.

[0026] Bacillus amyloliquefaciens, purchased from Shanghai Center for Preservation of Microorganisms, product number: SHMCC D10875.

[0027] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0028] (1) The combination of electrocatalytic oxidation and ultraviolet light irradiation in the present invention can reduce the generation of toxicity and organochlorine. In addition, reactive chlorine can be photolyzed under the mediation of ultraviolet radiation and generate highly reactive reactive oxygen species such as ·HO and ·Cl. Therefore, introducing ultraviolet light irradiation into the electrocatalytic oxidation process of high-sodium chloride-concentration wastewater is a way to solve the problem that it is difficult to completely mineralize pollutants in high-sodium chloride-concentration wastewater through the electrocatalytic oxidation process.

[0029] (2) Pretreating the triazinone production wastewater with a composite bacterium in the present invention can improve the recovery rate of pivalic acid.

[0030] (3) After successive fermentation treatment and ultraviolet light combined with electrocatalytic treatment, using toluene and cyclohexane as extraction liquids for fractional extraction in the present invention can further improve the recovery rate of pivalic acid. Detailed implementation mode

[0031] The bacteria used in the present invention are commercially available products:

[0032] Bacillus subtilis, purchased from Shanghai Center for Preservation of Microorganisms, product number: SHMCC D10486.

[0033] Bacillus cereus, purchased from Beijing Zhongke Quality Inspection Biotechnology Co., Ltd., product number: ZKCC25597.

[0034] Bacillus amyloliquefaciens, purchased from Shanghai Center for Preservation of Microorganisms, product number: SHMCC D10875.

[0035] Sulfate-reducing bacteria, purchased from Shanghai Center for Preservation of Microorganisms, product number: SHBCC D24615.

[0036] Example 1

[0037] This example provides a method for electrocatalytic oxidation treatment of triazinone wastewater, including the following steps:

[0038] (1) Adding a composite bacterium agent to the triazinone production wastewater, and the composite bacterium agent includes Bacillus subtilis, Bacillus cereus and Bacillus amyloliquefaciens. The dosage of Bacillus subtilis is 10 6 CFU / mL; the dosage of Bacillus cereus is 108 CFU / mL; The dosage of Bacillus amyloliquefaciens is 10 9 CFU / mL. Anaerobic culture is carried out at 32 °C for 8 days to obtain the degraded triazine ketone production wastewater;

[0039] (2) When the temperature of the degraded triazine ketone production wastewater is heated to 106 °C, 20 (v / v)% of the distillate is distilled out under stirring conditions; the distilled wastewater is obtained;

[0040] (3) The distilled wastewater is subjected to electrocatalytic oxidation using ultraviolet light combined with electrocatalysis; a 320 W xenon lamp is used to provide ultraviolet light source irradiation; the conditions for electrocatalytic oxidation are: constant current: 6 A, anode: ruthenium-iridium electrode, cathode: titanium electrode, electrolysis time: 2 h. The wastewater containing pivalic acid is obtained;

[0041] (4) To 1000 g of the wastewater containing pivalic acid, 50 g of the extraction liquid is added at 25 °C. The extraction liquid is toluene and cyclohexane with a volume ratio of 1.4:1. Stir for half an hour, let stand for half an hour, separate the liquid, and separate out the extraction liquid layer; then the water layer is extracted again in the same way once; the extraction liquid layers obtained from the two extractions are combined;

[0042] (5) The pH of the water layer is adjusted to neutral with liquid alkali, and vacuum distillation is carried out to obtain recycled water; the extraction liquid layer is subjected to vacuum distillation at 55 °C, the extraction liquid is condensed and recovered, and at the same time, the residue containing pivalic acid is obtained.

[0043] Example 2

[0044] This example provides a method for electrocatalytic oxidation treatment of triazine ketone wastewater, including the following steps:

[0045] (1) A composite bacterial agent is added to the triazine ketone production wastewater. The composite bacterial agent includes Bacillus subtilis, Bacillus cereus and Bacillus amyloliquefaciens. The dosage of Bacillus subtilis is 10 6 CFU / mL; the dosage of Bacillus cereus is 10 7 CFU / mL; the dosage of Bacillus amyloliquefaciens is 10 8 CFU / mL. Anaerobic culture is carried out at 35 °C for 8 days to obtain the degraded triazine ketone production wastewater;

[0046] (2) When the temperature of the degraded triazine ketone production wastewater is heated to 105 °C, 22 (v / v)% of the distillate is distilled out under stirring conditions; the distilled wastewater is obtained;

[0047] (3) The distilled wastewater is subjected to electrocatalytic oxidation using ultraviolet light combined with electrocatalysis; a 300 W xenon lamp is used to provide ultraviolet light source irradiation; the conditions for electrocatalytic oxidation are: constant current: 6 A, anode: ruthenium-iridium electrode, cathode: titanium electrode, electrolysis time: 1 h. The wastewater containing pivalic acid is obtained;

[0048] (4) Add 50 g of the extraction solution to 1000 g of the wastewater containing pivalic acid at 25°C. The extraction solution is toluene and cyclohexane with a volume ratio of 1.3:1. Stir for half an hour, let stand for half an hour, separate the liquid, and separate the extraction solution layer; then repeat the extraction of the water layer once in the same manner; combine the extraction solution layers from the two extractions;

[0049] (5) Adjust the pH of the water layer to neutral with liquid alkali, and perform vacuum distillation to obtain recycled water; perform vacuum distillation on the extraction solution layer at 55°C, condense and recover the extraction solution, and at the same time obtain the residue containing pivalic acid.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is: no degradation is carried out.

[0052] A method for electrocatalytic oxidation treatment of triazine ketone wastewater, comprising the following steps:

[0053] (1) When heating and raising the temperature of the triazine ketone production wastewater to 106°C, distill out 20 (v / v)% of the distillate under stirring conditions; obtain the wastewater after distillation;

[0054] (2) Use ultraviolet light combined with electrocatalysis to perform electrocatalytic oxidation on the wastewater after distillation; use a 320 W xenon lamp to provide an ultraviolet light source for irradiation; the conditions for electrocatalytic oxidation are: constant current: 6 A, anode: ruthenium-iridium electrode, cathode: titanium electrode, electrolysis time: 2 h. Obtain the wastewater containing pivalic acid;

[0055] (3) Add 50 g of the extraction solution to 1000 g of the wastewater containing pivalic acid at 25°C. The extraction solution is toluene and cyclohexane with a volume ratio of 1.4:1. Stir for half an hour, let stand for half an hour, separate the liquid, and separate the extraction solution layer; then repeat the extraction of the water layer once in the same manner; combine the extraction solution layers from the two extractions;

[0056] (4) Adjust the pH of the water layer to neutral with liquid alkali, and perform vacuum distillation to obtain recycled water; perform vacuum distillation on the extraction solution layer at 55°C, condense and recover the extraction solution, and at the same time obtain the residue containing pivalic acid.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is: the dosage of Bacillus subtilis is 10 8 CFU / mL; the dosage of Bacillus cereus is 10 6 CFU / mL; the dosage of Bacillus amyloliquefaciens is 10 7 CFU / mL.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 1 is that the composite bacterial agent includes Bacillus subtilis, sulfate-reducing bacteria, and Bacillus amyloliquefaciens. The dosage of Bacillus subtilis is 10 6 CFU / mL; the dosage of sulfate-reducing bacteria is 10 8 CFU / mL; the dosage of Bacillus amyloliquefaciens is 10 9 CFU / mL.

[0061] Comparative Example 4

[0062] The difference between this comparative example and Example 1 is that the extraction liquid is toluene and cyclohexane with a volume ratio of 1:1.

[0063] Comparative Example 5

[0064] The difference between this comparative example and Example 1 is that the extraction liquid is toluene.

[0065] Performance test

[0066] The specific situation of triazinone production wastewater is as follows: COD is 15280 mg / L, ammonia nitrogen is 820 mg / L, and the content of pivalic acid is 1 wt%.

[0067] The above triazinone production wastewater was treated using the processes of Examples 1 to 2 and Comparative Examples 1 to 5.

[0068] Measure the COD, ammonia nitrogen, and TOC in the recycled water. The COD detection method is carried out in accordance with HG 828-2017; the ammonia nitrogen detection method is carried out in accordance with HG 535-2009;

[0069] Measure the recovery rate of pivalic acid in the kettle: Pivalic acid is measured by the external standard method of HPLC under the following conditions: Mobile phase: acetonitrile: water = 8:2 (pH 4.0 adjusted with formic acid) Chromatographic column: C18 silica gel column; Wavelength: 214 nm; Flow rate 1 ml / min; Column temperature: 30 °C.

[0070] The recovery rate of pivalic acid = the mass of pivalic acid remaining in the kettle residue / the mass of pivalic acid in the wastewater before treatment * 100%.

[0071] The situation after treatment is shown in Table 1.

[0072] Table 1 Wastewater indexes after treatment

[0073]

[0074] From the results, it can be seen that the amounts of COD, ammonia nitrogen, and TOC in the recycled water of the treatment processes of Examples 1-2 are low, and at the same time, the recovery rate of pivalic acid is higher than 95%.

[0075] In Comparative Example 1, no pre-degradation treatment was carried out, and the amounts of COD, ammonia nitrogen, and TOC in the recycled water increased, while the recovery rate of pivalic acid decreased.

[0076] The types and dosages of the bacteria used in Comparative Examples 2 and 3 are different, which will reduce the recovery rate of pivalic acid to varying degrees.

[0077] The compositions of the extraction liquids in Comparative Example 4 and Comparative Example 5 are different, resulting in a decrease in the recovery rate of pivalic acid.

[0078] The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0079] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for electrocatalytic oxidation treatment of triazinone wastewater, characterized in that, It includes the following steps: (1) Add a composite bacterium agent to the triazine production wastewater and perform anaerobic cultivation to obtain the degraded triazine production wastewater; (2) Heat the degraded triazine production wastewater and distill out the fraction under stirring conditions to obtain the distilled wastewater; (3) Perform electrocatalytic oxidation on the distilled wastewater using ultraviolet light combined with electrocatalysis to obtain the wastewater containing pivalic acid; (4) Under the condition of 25 - 30 °C, add an extraction solution to the wastewater containing pivalic acid, stir for 20 - 40 min, stand for 30 - 40 min, separate the liquid, and separate out the extraction solution layer; repeat the extraction of the water layer once in the same way; combine the extraction solution layers of the two extractions; (5) Adjust the pH of the water layer to neutral with liquid caustic soda and perform vacuum distillation to obtain recycled water; perform vacuum distillation on the extraction solution layer, condense and recover the extraction solution, and at the same time obtain the residue containing pivalic acid.

2. The method according to claim 1, wherein The conditions for electrocatalytic oxidation in step (3) are: constant current: 6 A, anode: ruthenium-iridium electrode, cathode: titanium electrode, electrolysis time: 1 - 3 h.

3. The method according to claim 1, characterized in that, In step (3), a 300 - 350 W xenon lamp is used to provide ultraviolet light source irradiation.

4. The method according to claim 1, characterized in that The conditions for anaerobic cultivation in step (1) are: anaerobic cultivation at 30 - 35 °C for 6 - 8 days.

5. The method according to claim 1, wherein The composite bacterium agent in step (1) includes Bacillus subtilis, Bacillus cereus, and Bacillus amyloliquefaciens.

6. The method according to claim 5, wherein The dosage of the Bacillus subtilis in the step (1) is 10 6 ~10 7 CFU / mL; the dosage of the Bacillus cereus is 10 7 ~10 8 CFU / mL; the dosage of the Bacillus amyloliquefaciens is 10 8 ~10 9 CFU / mL.

7. The method according to claim 1, characterized in that, In step (2), 18 - 22 (v / v)% of the fraction is distilled out under stirring conditions.

8. The method according to claim 1, wherein In step (4), 50 g of the extraction solution is added to 1000 g of the wastewater containing pivalic acid.

9. The method according to claim 1, wherein In step (5), the extraction solution layer is subjected to vacuum distillation at 55 - 57 °C.

10. The method according to claim 1, characterized in that, The extraction solution in step (4) is toluene and cyclohexane with a volume ratio of (1.3 - 1.5):1.

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