Method for recovering hexazinone production wastewater

Abstract

The invention relates to a recovery method of hexazinone production wastewater, and belongs to the technical field of waste liquid recovery. According to the recovery method, high-efficiency separation of methanol and high-boiling-point impurities is realized through pressurized rectification and precise temperature control of tower top and tower kettle temperatures in cooperation with high-efficiency stainless steel wire mesh filler; by constructing a ferric oxide-activated carbon catalyst, sodium sulfite and circulating amine salt solution ternary synergistic toxicity breaking system, the efficiency bottleneck of a traditional single reducing agent is broken through, and synergistic interaction is achieved; efficient capture and high-value conversion of ammonia nitrogen are realized through precise stoichiometric control and an electrochemical innovation scheme; and a carbon dioxide saturated aqueous solution with the pH value of 5.3-5.7 is innovatively adopted to replace an organic solvent for adsorption column desorption, so that the desorption efficiency is greatly improved, and the VOCs emission and hazardous waste disposal risks caused by the use of methanol are effectively eliminated. According to the recycling method, the recycling rate and the purity are guaranteed, and meanwhile the recycling rate of substances such as organic amines is increased.

Description

Technical Field

[0001] This invention belongs to the technical field of waste liquid recycling, and more specifically, relates to a method for recycling wastewater from the production of cycloazinone. Background Technology

[0002] Cycloazolinone is a triazine herbicide developed by DuPont in 1974. It is characterized by systemic selectivity, post-emergence contact action, high efficiency, and low toxicity, making it the preferred agent for controlling bamboo, shrubs, and trees. However, the production process of cycloazolinone generates wastewater, which, if not thoroughly recovered, can cause environmental pollution and even threaten human health.

[0003] Currently, several publicly available technologies have been studied for the treatment and recycling of wastewater from the preparation of cycloazinone. Although existing technologies have achieved certain results in the treatment and recycling of cycloazinone wastewater, they still have some shortcomings.

[0004] (1) Resource recovery efficiency needs improvement: For example, for methanol solvent in wastewater, existing technologies mostly use distillation for recovery. Although high purity can be achieved, the purity improvement is limited by azeotropes, and the recovery cost for low-concentration methanol wastewater (concentration <5%) is high, making it uneconomical. Organic sulfur compounds in wastewater are mostly degraded by oxidation, failing to realize the recovery and utilization of sulfur resources. Methanethiol, as a byproduct, needs to be treated by alkaline absorption, which not only increases the amount of sulfur-containing wastewater generated but also brings environmental risks. Nitrogen resources in amine-containing wastewater are usually recovered in the form of low-value ammonium sulfate, failing to fully utilize their potential value.

[0005] (2) Insufficient process integration: Most of the disclosed technologies adopt a segmented processing flow, with poor connection between the units, resulting in problems such as high energy consumption and large footprint. For example, pretreatment, solvent recovery, and biological treatment units operate independently without forming a synergistic and optimized system, which limits the overall processing efficiency.

[0006] (3) High-salt wastewater is difficult to treat: The salinity of cycloazinone wastewater is high, and the existing biological treatment process can only tolerate a limited amount of salinity. Microbial activity is inhibited in a high-salt environment, and the treatment effect is unstable. The process of evaporation and crystallization to recover salt has high energy consumption and the purity of the recovered salt is low, making it difficult to achieve high-value utilization. Summary of the Invention

[0007] In view of at least one of the shortcomings mentioned in the background art, the present invention provides a method for recycling wastewater from the production of cycloazinone, which has the characteristics of high resource recovery rate.

[0008] The objective of this invention can be achieved through the following technical solutions: A method for recovering wastewater from the production of cycloazinone includes the following steps: S1. The mother liquor of the cycloazinone reaction is fed into a pressurized distillation column, using high-efficiency stainless steel wire mesh as the packing material. The operating pressure is controlled at 0.3~0.5MPa, the top temperature is 78~82℃, the bottom temperature is 85~90℃, the reflux ratio is 1.2~1.8, and the residence time is 25~35min. Methanol is collected at the top of the column, and the bottom is the residue after distillation. S2. The residual liquid after distillation is introduced into a selective catalytic reduction reactor, the pH is adjusted to 6.5-7.5, the temperature is raised to 35-45℃, and ferric oxide-activated carbon composite catalyst and 25-35 wt% sodium sulfite solution are added. The amount of ferric oxide-activated carbon composite catalyst added is 1.5-2.0% of the residual liquid mass, and the amount of sodium sulfite solution added is 3-5 kg / m³. 3 Residual liquid; stir and react for 40-60 minutes to obtain detoxified wastewater; S3. Introduce the detoxified wastewater into the struvite crystallization reactor. First, measure the concentration and volume of ammonia nitrogen in the wastewater, then proceed according to (NH4) + ):(Mg 2+ ):(PO4 3- Magnesium chloride and potassium dihydrogen phosphate were added in a ratio of 1:(1.15~1.25):(1.05~1.15), the pH was adjusted to 8.0~8.5, and the mixture was stirred at 25~35℃ for 20~40 min. The mixture was then filtered to obtain struvite crystals and high-nitrogen wastewater. S4. High-nitrogen wastewater is passed through a mesoporous silica adsorption column modified with amino functionalization to adsorb organic amines. After the adsorption column is saturated, it is desorbed with a carbon dioxide saturated aqueous solution with a pH of 5.3-5.7 to obtain an amine-containing eluent. The amine-containing eluent is introduced into the stripping-absorption unit. After air stripping, the stripping gas flow is introduced into a 5-8 wt% dilute sulfuric acid absorption tower to generate an ammonium salt solution with dimethylamine sulfate and / or methylamine sulfate as the main components.

[0009] Further, in step S4, the amine salt solution is delivered to the selective catalytic reduction reactor of step S2 via a metering pump, where it synergistically promotes the reaction with sodium sulfite; the CO2-poor solution after stripping is adjusted to pH 5.3-5.7 and recycled for the preparation of new desorption agent.

[0010] In step S4, the modified mesoporous silica adsorption column after amino functionalization exhibits an adsorption capacity ≥80 mg / g for organic amines (dimethylamine / methylamine). During adsorption, an online monitoring device can be installed at the outlet of the adsorption column. When a significant increase in the concentration of organic amines in the effluent is detected, approaching or reaching the concentration in the influent, it indicates that the adsorbent is nearing saturation.

[0011] Furthermore, the carbon dioxide saturated aqueous solution is dynamically prepared by passing industrial-grade CO2 gas through deionized water, with the pH precisely controlled at 5.3–5.7, the desorption temperature at 25–35°C, and the flow rate at 1.8–2.2 BV / h. The desorption process utilizes the weakly acidic environment provided by the CO2 / H2CO3 buffer system to selectively desorb organic amines by protonation, achieving efficient desorption while avoiding damage to the mesoporous structure.

[0012] Furthermore, in step S4, the gas-liquid ratio of the air stripping is 600-750:1, and the temperature is 25-30°C.

[0013] The amine-containing eluent is introduced into the stripping-absorption unit, where it is first stripped in an air stripping tower at a gas-liquid ratio of 600–750:1 and a temperature of 25–30°C, converting the dissolved organic amine into a gaseous state. The stripping gas stream is then introduced into a 5–8 wt% dilute sulfuric acid absorption tower, where a neutralization reaction occurs to generate an ammonium salt solution primarily composed of dimethylamine sulfate and / or methylamine sulfate. This amine salt solution is then metered and pumped to the selective catalytic reduction reactor in step S2, where it synergistically promotes the reaction with sodium sulfite. The ammonium salt solution acts as a reduction promoter, working in conjunction with sodium sulfite to enhance the catalytic reduction efficiency.

[0014] Furthermore, the amount of ammonium salt solution added in step S2, calculated in terms of nitrogen element, is 0.5-2 g / L.

[0015] Further, the method for preparing the amino-functionalized modified mesoporous silica is as follows: under nitrogen protection, mesoporous silica and toluene are mixed at a solid-liquid ratio of 1:19~21, and then the temperature is raised to 75~85℃. AEAPMDS is added dropwise at a mass ratio of 1:4~6 to AEAPMDS. After the addition is complete, 0.05~0.1 mL of glacial acetic acid is added as a catalyst, and the mixture is refluxed for 10~14 h. After the reaction is completed, the mixture is cooled to room temperature, and the solid product is collected by filtration. The product is washed with anhydrous ethanol and dried to obtain the amino-functionalized modified mesoporous silica.

[0016] AEAPMDS refers to 3-(2-aminoethylamino)propylmethyldimethoxysilane, which is an amino-functionalized silane coupling agent.

[0017] Furthermore, the recovery method also includes step S5: the high-nitrogen wastewater in step S4 is adsorbed by an adsorption column to produce denitrified wastewater, and the deammoniation wastewater is sent to a two-stage evaporator crystallizer. The inner wall of the heat exchange tube of the evaporator is coated with a polytetrafluoroethylene anti-scaling coating. The first stage of evaporation utilizes the residual heat of the distillation column in step S1 to evaporate and concentrate the wastewater to a solid-liquid ratio of 8-12% under normal pressure, and the wastewater temperature is controlled at 75-80℃. The second stage of evaporation uses low-pressure steam of 0.05-0.2MPa for auxiliary heating, controls the wastewater temperature at 70-75℃, and continues to concentrate the wastewater to a solid-liquid ratio of 15-20% under normal pressure. Subsequently, the concentrate is centrifuged to obtain industrial-grade solid NaCl salt.

[0018] Furthermore, the recovery method also includes step S6: the concentrate in step S5 is centrifuged to obtain industrial-grade solid NaCl salt and concentrated mother liquor, the pH of the concentrated mother liquor is adjusted to 7.2~7.8, food-grade sodium citrate is added at 0.1~0.3% of the mass of the concentrated mother liquor, the temperature is cooled to 20~25℃ using a program, and the mixture is allowed to stand for crystallization for 10~14 hours. High-purity sodium thiosulfate pentahydrate crystals are obtained by centrifugation.

[0019] Furthermore, the recovery method also includes step S7: the concentrated mother liquor from step S6 is centrifuged to obtain high-purity sodium thiosulfate pentahydrate crystals and crystallization mother liquor; the crystallization mother liquor is passed into an A / O-MBR biological treatment tank, the anaerobic HRT is controlled at 7~9h, and the residual organic matter is degraded by denitrifying bacteria; the aerobic HRT is controlled at 15~17h, the MBR membrane retains highly efficient microorganisms, the MLSS is controlled at 3000~4000mg / L, and 0.5g / L powdered activated carbon is added for adsorption. After precipitation and solid-liquid separation, a supernatant that meets the emission standards is obtained.

[0020] In step S1, during the treatment of cycloazinone production wastewater, a wire mesh woven from stainless steel wire is used as a packing material. This packing material has the characteristics of large specific surface area, high porosity, uniform fluid distribution, and high mass transfer efficiency. It can significantly improve the contact area and mass transfer effect between gas-liquid or liquid-liquid phases, thereby efficiently removing pollutants from the wastewater and achieving purification treatment of cycloazinone production wastewater.

[0021] In step S1, under a pressure of 0.3~0.5MPa, the relative volatility of methanol and water is increased compared with traditional vacuum distillation, thereby improving the purity and recovery rate of methanol collected at the top of the column, reducing the methanol content in the bottom residue, and ultimately reducing the load on subsequent processing.

[0022] In step S2, the mass ratio of ferric oxide to activated carbon is 1:2.5~3.5; the dosage of sodium sulfite solution is 3~5 kg / m³. 3 The residual liquid, that is, the amount of sodium sulfite solution that needs to be added to each cubic meter of residual liquid is 3-5 kg, which is 25-35 wt%.

[0023] Among them, under the action of ferric oxide-activated carbon composite catalyst, the number of catalytic active centers and pollutant adsorption capacity can be effectively improved, making SCN - Selectively reduced to thiosulfate (S2O3) 2- Methanethiol is converted into dimethyl sulfide {(CH3)2S}, which is then recovered with the desorption gas, avoiding the waste of sulfur resources in traditional oxidation processes and significantly reducing the difficulty of biochemical treatment.

[0024] Further, the preparation method of the ferric oxide-activated carbon composite catalyst is as follows: ferric nitrate nonahydrate is dissolved in an ethanol-water mixed solution to prepare an impregnation solution of 0.4~0.6 mol / L, then coconut shell activated carbon is added with a solid-liquid ratio of 1:9~11, and impregnation is carried out for 20~30 hours. Subsequently, 2~4% of APTES by mass of activated carbon is added, and the reaction is continued for 3~5 hours. The solvent is then evaporated to obtain a solid precursor. Finally, the solid precursor is calcined and activated, cooled, washed and dried to obtain the ferric oxide-activated carbon composite catalyst.

[0025] In step S2, the selective catalytic reduction reactor is an environmentally friendly device that uses a catalyst to selectively reduce nitrogen oxides (NOx) in waste gas into harmless nitrogen and water through a reducing agent (such as ammonia, urea, etc.) within a specific temperature range.

[0026] In step S3, the ammonia nitrogen concentration in the wastewater can be determined using Nessler's reagent spectrophotometry. The filtered struvite (MgNH4PO4) The 6H2O crystals are centrifuged to obtain struvite, which can be used for the recovery of high-efficiency phosphate fertilizer.

[0027] Further, in step S6, the programmed cooling refers to: maintaining the temperature at 45~55℃ for 5~15 minutes, then cooling down to 25~35℃ at a rate of 1.5~2.5℃ / h, and then cooling down to 20~25℃ at a rate of 0.8~1.2℃ / h.

[0028] In step S6, this invention effectively blocks Fe by precisely controlling the crystallization system within a weakly alkaline pH window of 7.2-7.8 and synergistically adding sodium citrate as a metal ion chelation inhibitor. 3+ / Cu 2+ The decomposition pathway is catalytically induced by ions. The concentrated mother liquor is rich in S2O3. 2- Sodium thiosulfate pentahydrate (Na2S2O3) was obtained by cooling crystallization. 5H2O can be sold as a chemical raw material.

[0029] In step S7, the degradation of residual organic matter by denitrifying bacteria occurs in an anaerobic environment. Denitrifying bacteria use nitrate or nitrite as electron acceptors to reduce it to nitrogen gas, while using organic matter as a carbon source and electron donor for growth and metabolism, thereby achieving the removal of organic matter and nitrogen.

[0030] The beneficial effects of this invention are: In step S1, this invention achieves efficient separation of methanol and high-boiling-point impurities through pressurized distillation and precise temperature control of the column top and bottom, combined with high-efficiency stainless steel wire mesh packing. In step S2, a ternary synergistic detoxification system is constructed using ferric oxide-activated carbon catalyst, sodium sulfite, and circulating amine salt solution, overcoming the efficiency bottleneck of traditional single reducing agents and achieving synergistic enhancement. In step S3, precise stoichiometric control and innovative electrochemical schemes achieve efficient capture and high-value conversion of ammonia nitrogen. In step S4, a novel approach uses a saturated carbon dioxide aqueous solution with pH 5.3-5.7 to replace organic solvents for adsorption column desorption, significantly improving desorption efficiency and effectively eliminating VOC emissions and hazardous waste disposal risks associated with methanol use. The amine salt solution generated from the desorption product through stripping-absorption is directionally recycled to step S2, increasing the degradation rate of chlorotriazine characteristic intermediates and reducing the amount of sodium sulfite added. This invention's recovery method, while ensuring recovery rate and purity, also improves the reuse rate of organic amines and other substances, reduces recovery costs, and significantly enhances the economic feasibility and industrial applicability of the process. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to specific embodiments, but the scope of protection of this invention is not limited thereto. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or according to the manufacturer's recommendations. Unless otherwise specified, all reagents and materials used are commercially available.

[0032] Example 1

[0033] A method for recovering wastewater from the production of cycloazinone includes the following steps: S1. Take 5 ml of the mother liquor from the cycloazinone reaction. 3 The solution was introduced into a pressurized distillation column (high-efficiency stainless steel wire mesh packing), with controlled pressure of 0.4 MPa, top temperature of 80℃, bottom temperature of 87℃, reflux ratio of 1.5, and residence time of 30 min. 420 L of methanol was collected at the top of the column, with a purity of 98.6% and a recovery rate of 97.2%. 4.5 m³ of distillate was obtained from the bottom of the column. 3 .

[0034] S2. The distillation residue from step S1 is introduced into a selective catalytic reduction reactor. The pH is adjusted to 7.0, the temperature is raised to 40°C, and 81 kg of ferric oxide-activated carbon composite catalyst (approximately 1.8% of the residue mass) and 18 kg of 30% sodium sulfite solution (approximately 4 kg / m³) are added. 3 The residual liquid was stirred and reacted for 50 minutes to obtain detoxified wastewater with a TOC of 92 mg / L and a toxicity unit (TU) of 1.5.

[0035] S3. In the detoxified wastewater, the ammonia nitrogen concentration (as N) was approximately 37.3 mg / L, as determined by Nessler's reagent spectrophotometry (HJ535). According to (NH4) + ):(Mg 2+ ):(PO4 3- Magnesium chloride hexahydrate and potassium dihydrogen phosphate were added in a ratio of 1:1.2:1.1 (molar ratio, in terms of nitrogen). The resulting amount of magnesium chloride hexahydrate was approximately 2.93 kg, and potassium dihydrogen phosphate was approximately 1.8 kg. The pH was adjusted to 8.3, and the mixture was stirred at 30°C for 30 min. After filtration, 0.45 kg of struvite crystals (purity 96.5%) and high-nitrogen wastewater were obtained. The ammonia nitrogen concentration of the high-nitrogen wastewater was reduced to 28 mg / L.

[0036] S4. After adsorbing organic amines onto an amino-functionalized mesoporous silica adsorption column, the high-nitrogen wastewater is desorbed using a saturated aqueous solution of carbon dioxide at pH 5.5 ± 0.1 at a desorption temperature of 30℃ and a flow rate of 2.0 BV / h to obtain an amine-containing desorption solution with a desorption efficiency of 96.2%. The amine-containing desorption solution is then stripped by air (gas-liquid ratio 700:1, 30℃), and the stripping gas is absorbed by 6.0% dilute sulfuric acid to generate an amine salt solution. The pH of the CO2-poor solution after stripping is adjusted back to 5.5 ± 0.1 and recycled.

[0037] Example 2

[0038] In Example 1 above, the high-nitrogen wastewater in step S4 is treated with an amino-functionalized mesoporous silica adsorption column to adsorb organic amines, and the resulting effluent is denitrified wastewater. In this example, based on Example 1, the denitrified wastewater generated after adsorbing organic amines with the amino-functionalized mesoporous silica adsorption column in step S4 is fed into a two-stage evaporator crystallizer. The first stage utilizes the residual heat (temperature 78±1℃) from the bottom of the column in step S1 of Example 1 to evaporate the solid-liquid ratio to 10% at atmospheric pressure. The second stage uses 0.1MPa low-pressure steam heating (temperature 72±1℃) to concentrate the solid-liquid ratio to 18%, followed by centrifugation to obtain 0.65 kg of industrial-grade NaCl solid (purity 99.2%).

[0039] Example 3

[0040] In Example 2 above, the concentrate was centrifuged to obtain industrial-grade NaCl solid and 1.5 ml of concentrated mother liquor. 3(Density approximately 1.032 g / mL). Based on Example 2, this example adjusts the pH of the concentrated mother liquor to 7.5, adds 3.1 kg of food-grade sodium citrate (approximately 0.2% of the concentrated mother liquor mass), stirs to dissolve, and waits for the temperature of the concentrated mother liquor to drop to 50±2℃. It is then kept at this temperature for 10 min, then cooled to 30±2℃ at a rate of 2.0℃ / h, and then further cooled to 22℃ at a rate of 1.0℃ / h. The mixture is allowed to stand for crystallization for 12 h, and then centrifuged to obtain 1.1 kg of sodium thiosulfate pentahydrate crystals (purity 99.1%, whiteness 87).

[0041] Example 4

[0042] In Example 3 above, the concentrated mother liquor was centrifuged to obtain sodium thiosulfate pentahydrate crystals and crystallization mother liquor. In this example, based on Example 3, the crystallization mother liquor was introduced into an A / O-MBR system with an anaerobic HRT of 8h and an aerobic HRT of 16h, MLSS of 3500mg / L, and 0.5g / L of powdered activated carbon was added simultaneously. The effluent COD was 48mg / L, ammonia nitrogen was 8mg / L, and total nitrogen was 14mg / L, which met the Class I standard of the Integrated Wastewater Discharge Standard (GB8978).

[0043] Example 5

[0044] Based on the process of Example 1, in step S2, in addition to adding ferric oxide-activated carbon catalyst and sodium sulfite, an ammonium salt solution generated in step S4 of the original Example 1 (simulating recycling) is added and stirred for 50 minutes to obtain detoxified wastewater. The TOC of the wastewater is reduced to 78 mg / L and the toxicity unit (TU) is <1.

[0045] Comparative Example 1

[0046] Compared with Example 1, the difference in this comparative example is that step S1 of this comparative example is: taking 5 ml of the cycloazinone reaction mother liquor. 3 The methanol was introduced into a pressurized distillation column (with ordinary structured packing), and the pressure was controlled at 0.4 MPa, the top temperature at 75°C, the bottom temperature at 85°C, the reflux ratio at 1.5, and the residence time at 30 min. 380 L of methanol was collected at the top of the column, with a purity of 95.2% (GC detection) and a recovery rate of 90.5%. 4.6 m³ of distillate was obtained from the bottom of the column. 3 The remaining components, preparation steps, and parameters are all the same.

[0047] Comparative Example 2

[0048] Compared with Example 1, the difference in this comparative example is that step S2 of this comparative example is: 4.5m 3 The distillation residue was introduced into the reactor, the pH was adjusted to 7.0, the temperature was raised to 40°C, and a single activated carbon catalyst (1.8% of the residue mass) and a 30% sodium sulfite solution (4 kg / m³) were added.3 The mixture was stirred and reacted for 50 minutes to obtain detoxified wastewater. The TOC of the wastewater was reduced to 120 mg / L, and the toxicity unit (TU) was 1.9. The remaining components, preparation steps, and parameters were consistent.

[0049] Comparative Example 3

[0050] Compared with Example 1, the difference in this comparative example is that in step S3, (NH4) + ):(Mg 2+ ):(PO4 3- The feed ratio was adjusted to 1:1.0:1.0, with approximately 2.44 kg of magnesium chloride hexahydrate and approximately 1.64 kg of potassium dihydrogen phosphate. The remaining components, preparation steps, and parameters remained the same. The resulting struvite crystals weighed 0.35 kg (92.5% purity), and the ammonia nitrogen concentration in the high-nitrogen wastewater was reduced to 35 mg / L.

[0051] Comparative Example 4

[0052] Compared with Example 1, this comparative example differs in that, in step S4, a 3% methanol aqueous solution is used instead of a CO2 saturated aqueous solution for analysis, reducing the analysis efficiency to 85%. All other components, preparation steps, and parameters remain the same.

[0053] Comparative Example 5

[0054] Compared with Example 1, this comparative example differs in that, in step S4, a conventional adsorption column is used instead of an amino-functionalized mesoporous silica adsorption column, resulting in a reduction in the desorption efficiency to 80%. All other components, preparation steps, and parameters remain the same.

[0055] The samples prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to the following performance tests: The test results are shown in Table 1.

[0056] Table 1

[0057] As shown in Table 1, in Example 5, the introduction of amine salt solution in step S2 to enhance detoxification resulted in more complete degradation of the detoxification intermediates, leading to increased struvite production in step S3 and thus improved desorption efficiency in step S4. In Comparative Example 1, the use of ordinary packing material in step S1 resulted in reduced methanol purity and recovery rate, which affected subsequent processes. In Comparative Example 2, the catalyst in step S2 was changed, which resulted in incomplete detoxification in step S3, leaving toxic intermediates and inhibiting struvite crystallization. Although the water quality in Comparative Example 3 was consistent with that in Example 1 for steps S1-S2, the imbalance in step S3 led to increased ammonia nitrogen residue, directly causing a decrease in desorption efficiency in step S4. In Comparative Examples 4 and 5, the changes in desorption conditions in step S4 reduced the selective adsorption capacity of the adsorption column for organic amines, ultimately leading to a decrease in desorption efficiency.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for recovering wastewater from the production of cycloazinone, characterized in that, Includes the following steps: S1. The mother liquor of the cycloazinone reaction is fed into a pressurized distillation column, using high-efficiency stainless steel wire mesh as the packing material. The operating pressure is controlled at 0.3~0.5MPa, the top temperature is 78~82℃, the bottom temperature is 85~90℃, the reflux ratio is 1.2~1.8, and the residence time is 25~35min. Methanol is collected at the top of the column, and the bottom is the residue after distillation. S2. The residual liquid after distillation is introduced into a selective catalytic reduction reactor, the pH is adjusted to 6.5-7.5, the temperature is raised to 35-45℃, and ferric oxide-activated carbon composite catalyst and 25-35 wt% sodium sulfite solution are added. The amount of ferric oxide-activated carbon composite catalyst added is 1.5-2.0% of the residual liquid mass, and the amount of sodium sulfite solution added is 3-5 kg / m³. 3 Residual liquid; stir and react for 40-60 minutes to obtain detoxified wastewater; S3. Introduce the detoxified wastewater into the struvite crystallization reactor. First, measure the concentration and volume of ammonia nitrogen in the wastewater, then proceed according to (NH4) + ):(Mg 2+ ):(PO4 3- Magnesium chloride and potassium dihydrogen phosphate were added in a ratio of 1:(1.15~1.25):(1.05~1.15), the pH was adjusted to 8.0~8.5, and the mixture was stirred at 25~35℃ for 20~40 min. The mixture was then filtered to obtain struvite crystals and high-nitrogen wastewater. S4. High-nitrogen wastewater is passed through a mesoporous silica adsorption column modified with amino functionalization to adsorb organic amines. After the adsorption column is saturated, it is desorbed with a carbon dioxide saturated aqueous solution with a pH of 5.3-5.7 to obtain an amine-containing eluent. The amine-containing eluent is introduced into the stripping-absorption unit. After air stripping, the stripping gas flow is introduced into a 5-8 wt% dilute sulfuric acid absorption tower to generate an ammonium salt solution with dimethylamine sulfate and / or methylamine sulfate as the main components.

2. The method for recovering wastewater from the production of cycloazinone according to claim 1, characterized in that, The recycling method further includes step S5: after the high-nitrogen wastewater in step S4 is adsorbed by the adsorption column, denitrification wastewater is generated. The deammoniation wastewater is sent into a two-stage evaporator crystallizer, and the inner wall of the heat exchange tube of the evaporator is coated with a polytetrafluoroethylene anti-scaling coating. The first stage of evaporation utilizes the residual heat from the distillation column in step S1 to concentrate the wastewater to a solid-liquid ratio of 8-12% under atmospheric pressure, with the wastewater temperature controlled at 75-80℃. The second stage of evaporation uses low-pressure steam (0.05-0.2 MPa) for auxiliary heating, controlling the wastewater temperature at 70-75℃, and continues to concentrate the wastewater to a solid-liquid ratio of 15-20% under atmospheric pressure. The concentrate is then centrifuged to obtain industrial-grade solid NaCl salt.

3. The method for recovering wastewater from the production of cycloazinone according to claim 2, characterized in that, The recovery method further includes step S6: the concentrate in step S5 is centrifuged to obtain industrial-grade solid NaCl salt and concentrated mother liquor. The pH of the concentrated mother liquor is adjusted to 7.2~7.

8. Food-grade sodium citrate is added at 0.1~0.3% of the mass of the concentrated mother liquor. The temperature is then lowered to 20~25℃ using a programmed cooling method. The mixture is allowed to stand and crystallize for 10~14 hours. High-purity sodium thiosulfate pentahydrate crystals are obtained by centrifugation.

4. The method for recovering wastewater from the production of cycloazinone according to claim 3, characterized in that, In step S6, the programmed cooling refers to: maintaining the temperature at 45~55℃ for 5~15 minutes, then cooling down to 25~35℃ at a rate of 1.5~2.5℃ / h, and then cooling down to 20~25℃ at a rate of 0.8~1.2℃ / h.

5. The method for recovering cycloazinone production wastewater according to claim 3, characterized in that, The recovery method further includes step S7: the concentrated mother liquor from step S6 is centrifuged to obtain high-purity sodium thiosulfate pentahydrate crystals and crystallization mother liquor; the crystallization mother liquor is passed into an A / O-MBR biological treatment tank, the anaerobic HRT is controlled at 7~9h, and the residual organic matter is degraded by denitrifying bacteria; the aerobic HRT is controlled at 15~17h, the MBR membrane retains highly efficient microorganisms, the MLSS is controlled at 3000~4000mg / L, and 0.5g / L powdered activated carbon is added for adsorption. After precipitation and solid-liquid separation, the supernatant is obtained.

6. The method for recovering cycloazinone production wastewater according to claim 1, characterized in that, In step S2, the mass ratio of ferric oxide to activated carbon is 1:2.5~3.

5.

7. The method for recovering wastewater from the production of cycloazinone according to claim 1, characterized in that, In step S2, the preparation method of the ferric oxide-activated carbon composite catalyst is as follows: Ferric nitrate nonahydrate was dissolved in an ethanol-water mixture to prepare an impregnation solution of 0.4-0.6 mol / L. Coconut shell activated carbon was then added, with a solid-liquid ratio of 1:9-11. The solution was impregnated for 20-30 hours. Subsequently, 2-4% APTES (by weight of activated carbon) was added, and the reaction was continued for 3-5 hours. The solvent was then evaporated to obtain a solid precursor. Finally, the solid precursor was calcined and activated, cooled, washed, and dried to obtain a ferric oxide-activated carbon composite catalyst.

8. The method for recovering wastewater from the production of cycloazinone according to claim 1, characterized in that, In step S4, the carbon dioxide saturated aqueous solution is dynamically prepared by passing industrial-grade CO2 gas through deionized water, with the pH precisely controlled at 5.3–5.7, the desorption temperature at 25–35°C, and the flow rate at 1.8–2.2 BV / h; the gas-liquid ratio of the air stripping is 600–750:1, and the temperature is 25–30°C.

9. The method for recovering wastewater from the production of cycloazinone according to claim 1, characterized in that, In step S4, the amine salt solution is pumped to the selective catalytic reduction reactor of step S2 via a metering pump to promote the reaction in conjunction with sodium sulfite; the CO2-poor solution after stripping is adjusted to pH 5.3-5.7 and recycled for the preparation of new desorption agent.

10. The method for recovering wastewater from the production of cycloazinone according to claim 1, characterized in that, In step S4, the method for preparing the modified mesoporous silicon after amino-functionalization is as follows: Under nitrogen protection, mesoporous silica and toluene were mixed at a solid-liquid ratio of 1:19-21, and then the mixture was heated to 75-85°C. AEAPMDS was added dropwise at a mass ratio of 1:4-6 to AEAPMDS to mesoporous silica. After the addition was complete, 0.05-0.1 mL of glacial acetic acid was added as a catalyst, and the mixture was refluxed for 10-14 h. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration. The solid product was washed with anhydrous ethanol and dried to obtain modified mesoporous silica with amino functionalization.

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