Paraquat wastewater resourceful treatment method

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly discloses a paraquat wastewater resourceful treatment method which comprises the following steps: placing pyridine production wastewater under a subcritical condition, taking air as an oxidizing agent, enabling pyridine and derivative organic matters thereof to react on the surface of a noble metal catalyst, and degrading the organic matters into CO2, N2 and water; adsorbing residual pyridine at normal temperature by using special resin; and treating by adopting a biochemical process, and discharging after reaching the standard. Adjusting the pH value of the paraquat production wastewater to be acidic; the method comprises the following steps: placing wastewater under a subcritical condition, degrading nitrogen-containing organic matters into CO2, ammonia and water, and removing most cyanide and paraquat; the ammonium chloride and the sodium chloride are separated by hot circulating evaporation, and the recovered ammonium chloride and the recovered sodium chloride meet the recycling standard. By adopting the paraquat wastewater resourceful treatment method disclosed by the invention, the problems that pyridine compounds are difficult to degrade, the biochemical inhibition property is strong, and salt and pyridine resources cannot be effectively recycled in paraquat wastewater treatment in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for the resource-based treatment of paraquat wastewater. Background Technology

[0002] Paraquat (chemical name: 1,1'-dimethyl-4,4'-bipyridine cationic salt) is a highly effective, non-selective herbicide widely used in agricultural production. Its production process mainly involves two stages: pyridine production and paraquat synthesis, both of which generate large amounts of wastewater.

[0003] Pyridine production stage: Acetaldehyde, formaldehyde, and ammonia are used as raw materials to react at 350-550℃ with a catalyst to produce pyridine and 3-methylpyridine. After distillation, wastewater containing pyridine, pyridine derivatives, formaldehyde, acetaldehyde, and ammonia nitrogen is produced. Paraquat synthesis stage: Paraquat is produced by reacting pyridine with chloromethane, cyanide, etc. After extraction, high-salt and highly toxic wastewater containing ammonium chloride, sodium chloride, pyridine, cyanide, and paraquat is produced.

[0004] The pyridine compounds in the aforementioned wastewater exhibit foul odor, neurotoxicity, and corneal damage. Furthermore, due to their stable heterocyclic structure, they are difficult to degrade and possess a strong inhibitory ("bactericidal") effect on microorganisms during biochemical treatment, rendering traditional biochemical methods ineffective. Simultaneously, the failure to recover the salt resources (ammonium chloride, sodium chloride) and pyridine in the wastewater not only wastes resources but also exacerbates environmental pollution. Therefore, developing a method for treating paraquat wastewater that can efficiently degrade pollutants and achieve resource recovery is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the resource-based treatment of paraquat wastewater, which solves the problems of pyridine compounds being difficult to degrade, having strong biochemical inhibitory effects, and being unable to effectively recover salt and pyridine resources in the existing paraquat wastewater treatment technology.

[0006] To achieve the above objectives, the present invention provides a method for the resource-based treatment of paraquat wastewater, comprising the following steps: Step 1, treating pyridine production wastewater by subcritical water catalytic oxidation, placing the pyridine production wastewater under subcritical conditions, using air as an oxidant, and reacting under the action of a noble metal catalyst to obtain an oxidized liquid; Step 2, pyridine recovery: The oxidizing liquid in Step 1 is used to adsorb pyridine at room temperature using two-stage special resins, and then desorbed using 50%~100% methanol or acetone. The desorbed liquid is recovered by distillation, and pyridine is recovered simultaneously during distillation. Step 3, Biochemical Treatment: The wastewater after adsorption in Step 2 is treated using a biochemical anaerobic-aerobic process to meet discharge standards; Step 4: Treat the paraquat production wastewater by adjusting the pH of the wastewater to 2-4 and diluting the wastewater to reduce the concentration of chemical oxygen demand in the wastewater, thus avoiding overheating and salting out. Step 5, subcritical water catalytic oxidation: The wastewater treated in step 4 is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out under the action of rare earth catalyst. Step 6, Salt Recovery: The oxidizing liquid from Step 5 is separated into ammonium chloride and sodium chloride by thermal cyclic evaporation, and the recovered ammonium chloride meets the standards.

[0007] Preferably, in step 1, the oxidant dosage is 105-150 Nm per ton of water. 3 / h air, reaction temperature 250-280℃, reaction pressure corresponding to temperature, reaction time 0.8~2.5h.

[0008] Preferably, in step 1, the noble metal catalyst is at least one of ruthenium, rhodium, palladium and platinum, supported on titanium dioxide or zirconium dioxide support, with a loading rate of 0.5% to 2%.

[0009] Preferably, in step 2, the resin adsorption rate is 1 BV / h, the pyridine content in the wastewater after adsorption is <5 mg / L, and the desorption rate is 3 BV / h.

[0010] Preferably, in step 4, the chemical oxygen demand (COD) concentration of the diluted wastewater is 15,000-20,000 mg / L.

[0011] Preferably, in step 5, the oxidant dosage is 60-80 Nm³ per ton of dilution water. 3 / h air, reaction temperature 260-280℃, reaction pressure corresponding to temperature, reaction time 1~3h.

[0012] Preferably, in step 5, the rare earth catalyst is at least one of cerium and vanadium, supported on a titanium dioxide or zirconium dioxide support, with a loading rate of 1% to 5%.

[0013] The advantages and beneficial effects of the above-mentioned method for the resource utilization of paraquat wastewater are as follows: 1. This invention improves the removal rate of organic matter and total nitrogen in pyridine production wastewater through subcritical water catalytic oxidation; and improves the removal rate of cyanide and paraquat in paraquat production wastewater.

[0014] 2. This invention boasts a high resource recovery rate, with pyridine recovery ≥95% and ammonium chloride recovery meeting agricultural standards, thus achieving resource recycling; it also improves biodegradability, reducing the BOD5 / COD ratio of wastewater after pyridine recovery. Cr ≥0.3, can be discharged in compliance with standards through conventional biochemical treatment, reducing treatment costs; operation is stable and reliable, process parameters are clear, reaction conditions are controllable, and it is suitable for industrial application.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process of this invention. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0019] Unless otherwise defined, all reagents, equipment and other materials used in this invention are commercially available.

[0020] A method for the resource-based treatment of paraquat wastewater, such as Figure 1 The process includes the following steps: Step 1, treating pyridine production wastewater using subcritical water catalytic oxidation. The pyridine production wastewater is placed under subcritical conditions, with air as the oxidant, and the reaction takes place under the action of a noble metal catalyst to obtain an oxidized liquid. The oxidant dosage is 105-150 Nm³ per ton of water. 3 The reaction conditions are as follows: air volume / h, reaction temperature 250-280℃, reaction pressure corresponding to temperature, and reaction time 0.8-2.5 h. The noble metal catalyst is at least one of ruthenium, rhodium, palladium, and platinum, supported on titanium dioxide or zirconium dioxide, with a loading rate of 0.5%-2%.

[0021] Utilizing the enhanced oxygen solubility and increased reactivity of subcritical water under high pressure and temperature, combined with the high catalytic activity of noble metal catalysts (ruthenium / rhodium / palladium / platinum), readily degradable organic matter such as formaldehyde and acetaldehyde in wastewater is completely degraded. Pyridine derivatives are converted into pyridine, with most of the pyridine being converted into carbon dioxide, ammonia nitrogen, and water. The catalyst can simultaneously convert ammonia nitrogen into nitrogen gas, significantly reducing wastewater toxicity and chemical oxygen demand (COD). Cr This significantly reduces the total nitrogen value and the load on subsequent adsorption treatments.

[0022] Step 2, pyridine recovery: The oxidizing liquid from Step 1 is subjected to two-stage adsorption of pyridine using a special resin at room temperature, followed by desorption using 50%–100% methanol or acetone. The desorbed liquid is recovered by distillation, simultaneously recovering the pyridine solution. The resin adsorption rate is 1 BV / h, and the pyridine content in the wastewater after adsorption is <5 mg / L. The desorption rate is 3 BV / h. The special resin selectively adsorbs pyridine from the oxidizing liquid, and after desorption and distillation, high-purity pyridine is recovered and reused in paraquat production.

[0023] Step 3, Biochemical Treatment: The wastewater after adsorption in Step 2 is treated using a biochemical anaerobic / aerobic (A / O) process to meet discharge standards. The biodegradability of the wastewater after pyridine recovery is significantly improved (5-day biochemical oxygen demand BOD5 / chemical oxygen demand COD). Cr (≥0.3), after treatment by the biochemical A / O process, it meets the emission standards.

[0024] Step 4: Treat the paraquat production wastewater by adjusting its pH to 2-4 and diluting it to reduce the concentration of chemical oxygen demand (COD). The COD concentration of the diluted wastewater should be 15,000-20,000 mg / L. Adjusting the pH and diluting the wastewater creates suitable conditions for the subsequent oxidation reaction.

[0025] Step 5, subcritical water catalytic oxidation: The wastewater treated in Step 4 is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out in the presence of a rare earth catalyst; the oxidant dosage is 60-80 Nm³ per ton of dilution water. 3 The reaction process involves applying air at a rate of 260-280℃ per hour, with the reaction pressure corresponding to the temperature, and a reaction time of 1-3 hours. The rare earth catalyst is at least one of cerium or vanadium, supported on a titanium dioxide or zirconium dioxide carrier, with a loading rate of 1%-5%. This step removes most of the organic matter from the water; after the reaction, the organic matter is decomposed into carbon dioxide, water, and a small amount of acetic acid. The rare earth catalyst (cerium / vanadium) efficiently degrades highly toxic substances such as paraquat and cyanide under subcritical conditions, reducing wastewater toxicity and chemical oxygen demand (COD).

[0026] Step 6, Salt Recovery: The oxidation solution from Step 5 is separated into ammonium chloride and sodium chloride through thermal cyclic evaporation. The recovered ammonium chloride meets the standards. By separating ammonium chloride and sodium chloride from the oxidation solution through thermal cyclic evaporation, the recovered ammonium chloride meets agricultural standards, realizing the resource utilization of salt resources.

[0027] Example 1 A factory produces 500 tons / day of wastewater from pyridine production and 200 tons / day of wastewater from paraquat production.

[0028] Before treatment, the pyridine production wastewater contained a chemical oxygen demand (COD) of 28,000 mg / L, ammonia nitrogen of 350 mg / L, pyridine of 410 mg / L, other methylpyridines of 3,400 mg / L, formaldehyde of 5,500 mg / L, and acetaldehyde of 1,200 mg / L. The paraquat production wastewater contained a COD of 46,000 mg / L, a pH of 9.5, free ammonia of 15,000 mg / L, cyanide (CN-) of 3,300 mg / L, and paraquat of 370 mg / L.

[0029] A method for the resource utilization treatment of paraquat wastewater includes the following steps: Step 1: Treat pyridine production wastewater using subcritical water catalytic oxidation. The wastewater is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out in the presence of a 1% ruthenium / titanium dioxide catalyst to obtain an oxidized solution. The oxidant dosage is 100 Nm³ per ton of water. 3 The reaction conditions were: air per hour, reaction temperature 255℃, reaction pressure 5.5MPa (corresponding to temperature), and reaction time 1.5h. The product water contained COD 1800mg / L, ammonia nitrogen 25mg / L, pyridine 130mg / L, methylpyridine 7mg / L, formaldehyde 3mg / L, and acetaldehyde 5mg / L.

[0030] Step 2, pyridine recovery: The oxidizing solution from Step 1 is subjected to two-stage adsorption of pyridine using a special resin at room temperature. The resin adsorption rate is 1 BV / h, and the pyridine content in the wastewater after adsorption is <5 mg / L. Desorption is performed using 90% methanol to obtain 83 kg / d of 75% pyridine solution. The desorbed solution is then distilled to recover the pyridine solution at a desorption rate of 3 BV / h and a recovery efficiency of 97%. The methanol is recycled after distillation.

[0031] Step 3, Biochemical Treatment: The wastewater after adsorption in Step 2 is treated using a biochemical anaerobic / aerobic process to meet discharge standards. The biochemical oxygen demand (B / C) ratio in the recovered wastewater is 0.56, and it meets discharge standards after treatment using a biochemical anaerobic / aerobic (A / O) process.

[0032] Step 4, Pretreatment: Dilute with pure water, adjust the pH of paraquat production wastewater to 4 with hydrochloric acid, and dilute to a COD of 20000 mg / L.

[0033] Step 5, Subcritical water catalytic oxidation: Using a 3% cerium / zirconium dioxide catalyst, 75 Nm³ of catalyst is added per ton of dilution water. 3 With air per hour, the reaction was carried out at a reaction temperature of 270℃ and a corresponding pressure for 2 hours. The COD in the product water was 1500 mg / L, the total cyanide was 3-8 mg / L, and the paraquat was <1 mg / L.

[0034] Salt recovery: Ammonium chloride and sodium chloride are separated by thermal circulating evaporation. The recovered ammonium chloride meets the GB / T2946-2018 standard, and the recovered sodium chloride meets the general solid waste standard.

[0035] After treatment, the pyridine production wastewater has a COD of 1800 mg / L, ammonia nitrogen of 25 mg / L, pyridine of 130 mg / L, and methylpyridine of 7 mg / L. Pyridine recovery: Two-stage special resin adsorption is used, resulting in pyridine concentrations <5 mg / L after adsorption; desorption with 90% methanol yields 83 kg of 75% pyridine solution, with a recovery efficiency of 97%. The methanol is recycled after distillation. Biochemical treatment: After recovery, the wastewater has a biochemical oxygen demand (B / C) ratio of 0.56. After treatment using a biochemical anaerobic / aerobic (A / O) process, it meets discharge standards.

[0036] After treatment, the wastewater from paraquat production has the following characteristics: COD of 1500 mg / L, total cyanide of 3-8 mg / L, and paraquat concentration of <1 mg / L. Salt recovery: Ammonium chloride and sodium chloride are separated using a thermal circulating evaporation method. The recovered ammonium chloride meets the GB / T2946-2018 standard, and the recovered sodium chloride meets general solid waste standards.

[0037] Example 2 A factory produces 800 t / d of wastewater from pyridine production and 400 t / d of wastewater from paraquat production.

[0038] Before treatment, the pyridine production wastewater contained a chemical oxygen demand (COD) of 40,000 mg / L, ammonia nitrogen of 430 mg / L, pyridine of 340 mg / L, other methylpyridines of 2,800 mg / L, formaldehyde of 16,000 mg / L, and acetaldehyde of 1,900 mg / L. The paraquat production wastewater contained a COD of 52,000 mg / L, a pH of 9.1, free ammonia of 21,000 mg / L, cyanide (CN-) of 4,100 mg / L, and paraquat of 420 mg / L.

[0039] A method for the resource utilization treatment of paraquat wastewater includes the following steps: Step 1: Treat pyridine production wastewater using subcritical water catalytic oxidation. The wastewater is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out in the presence of a 0.5% platinum / zirconium dioxide catalyst to obtain an oxidized solution. The oxidant dosage is 140 Nm³ per ton of water. 3 The reaction conditions were: air concentration / h, reaction temperature 265℃, reaction pressure 6.5 MPa (corresponding to temperature), and reaction time 1 h. The product water contained COD 1200 mg / L, ammonia nitrogen 14 mg / L, pyridine 62 mg / L, and methylpyridine 5 mg / L.

[0040] Step 2, pyridine recovery: The oxidizing solution from Step 1 is subjected to two-stage adsorption of pyridine using a special resin at room temperature. The resin adsorption rate is 1 BV / h, and the pyridine content in the wastewater after adsorption is <5 mg / L. Desorption is then performed using 60% acetone to obtain 60 kg of a 75% pyridine solution. The desorbed solution is then distilled to recover the pyridine solution at a desorption rate of 3 BV / h and a recovery efficiency of 95%. Methanol is distilled and recycled.

[0041] Step 3, Biochemical Treatment: The wastewater after adsorption in Step 2 is treated using a biochemical anaerobic-aerobic process to meet discharge standards. The biochemical oxygen demand (B / C) ratio in the recovered wastewater is 0.45, and it meets discharge standards after treatment using a biochemical anaerobic / aerobic (A / O) process.

[0042] Step 4, Pretreatment: Adjust the pH of the paraquat production wastewater to 3.4 with hydrochloric acid, and dilute with pure water until the COD is 18000 mg / L.

[0043] Step 5, Subcritical water catalytic oxidation: Using a 2% vanadium / titanium dioxide catalyst, 65 Nm³ of catalyst is added per ton of dilution water. 3 With air per hour, the reaction was carried out at a reaction temperature of 260℃ and a corresponding pressure for 3 hours. The COD in the product water was 1820 mg / L, the total cyanide was 2 mg / L, and the paraquat was <1 mg / L.

[0044] Salt recovery: Ammonium chloride and sodium chloride are separated by thermal circulating evaporation. The recovered ammonium chloride meets the GB / T2946-2018 standard, and the recovered sodium chloride meets the general solid waste standard.

[0045] After treatment, the pyridine production wastewater has a COD of 1200 mg / L, ammonia nitrogen of 14 mg / L, pyridine concentration of 62 mg / L, and methylpyridine concentration of 5 mg / L. Pyridine recovery: Two-stage adsorption with special resins is used, resulting in pyridine concentrations <5 mg / L after adsorption; desorption with 60% acetone yields 60 kg of a 75% pyridine solution with a recovery efficiency of 95%. The acetone is then recycled after distillation. Biochemical treatment: After recovery, the wastewater has a biochemical oxygen demand (B / C) ratio of 0.45. After treatment using a biochemical anaerobic / aerobic (A / O) process, it meets discharge standards.

[0046] After treatment, the wastewater from paraquat production has the following characteristics: COD of 1820 mg / L, total cyanide of 2 mg / L, and paraquat concentration of <1 mg / L. Salt recovery: Ammonium chloride and sodium chloride are separated by thermal circulating evaporation, and the recovered ammonium chloride meets the standard of GB / T2946-2018.

[0047] Comparative Example 1 For paraquat production wastewater (including pyridine production wastewater and paraquat synthesis wastewater) with the same process as in Example 1, the following steps are taken to simulate the application scenario of traditional direct biochemical treatment: Step 1: Preprocessing.

[0048] Take pyridine production wastewater (COD 28000 mg / L, ammonia nitrogen 350 mg / L, pyridine 410 mg / L) and paraquat production wastewater (COD 46000 mg / L, cyanide 3300 mg / L, paraquat 370 mg / L) and mix them in the actual ratio (5:2). Adjust the pH of the mixed wastewater to 7-8 with hydrochloric acid. No dilution is required.

[0049] Add polyaluminum chloride (PAC) at a dosage of 30 mg / L, stir for 30 min, let stand for 1 h, and filter to remove suspended impurities.

[0050] Step 2: Biochemical treatment.

[0051] The pretreated wastewater was directly fed into the anaerobic tank, with the temperature controlled at 35℃ and the hydraulic retention time (HRT) at 24h, and then inoculated with ordinary anaerobic sludge.

[0052] Anaerobic effluent enters the aerobic tank, where dissolved oxygen (DO) is controlled at 2-4 mg / L, temperature at 25-30℃, and HRT at 18h. Ordinary activated sludge is then inoculated.

[0053] Step 3: Discharge water.

[0054] The effluent from the aerobic tank is directly tested for relevant indicators. If the indicators do not meet the standards, the effluent is recycled to the pretreatment stage.

[0055] Treatment results: Pyridine removal rate: <30%; Cyanide removal rate: <40%; COD removal rate: <50%.

[0056] Resource recovery: No pyridine or ammonium chloride is recovered, and salt resources are discharged with wastewater, causing pollution; Compliance status: Effluent COD>20000mg / L, pyridine>290mg / L, cyanide>1980mg / L, far below the discharge standards.

[0057] Comparative Example 2 For the paraquat production wastewater treated by the process in Example 1, the existing "oxidation and evaporation" treatment route is adopted for wastewater treatment, and the steps are as follows: Step 1: Fenton oxidation treatment of pyridine production wastewater.

[0058] Take pyridine production wastewater (same initial parameters as in Example 1), adjust the pH to 3-4, and add ferrous sulfate (Fe). 2+ The dosage is 500 mg / L. After stirring and dissolving, 30% hydrogen peroxide (H2O2) is slowly added. H2O2 reacts with Fe... 2+ The molar ratio was 10:1, the reaction temperature was controlled at 50℃, and the reaction time was 2h.

[0059] After the reaction is complete, adjust the pH to 8-9, add polyacrylamide (PAM) at a dosage of 5 mg / L, let stand for 2 hours, and then filter to remove the iron sludge.

[0060] Step 2: Evaporate the wastewater from paraquat production.

[0061] Wastewater from paraquat production (same as the initial parameters in Example 1) was directly introduced into an atmospheric pressure evaporator. The evaporation temperature was controlled at 100°C and the evaporation time was 8 hours. The condensate was collected.

[0062] The evaporation residue (containing ammonium chloride, sodium chloride, undegraded paraquat, and cyanide) is disposed of directly as hazardous waste.

[0063] Step 3: Mixing process.

[0064] The filtered water from step 1 is mixed with the condensate from step 2, and the mixture is discharged after testing the relevant parameters.

[0065] Treatment efficiency: Pyridine removal rate: 10%-20%; Cyanide removal rate: 75%-80%; COD removal rate: 65%-70%.

[0066] Resource recovery: No pyridine recovery; evaporation residue contains highly toxic substances; ammonium chloride cannot be recovered; additional hazardous waste disposal costs must be incurred. Compliance status: Mixed effluent COD > 800 mg / L, pyridine > 120 mg / L, cyanide > 660 mg / L, failing to meet standards; and evaporation energy consumption is high.

[0067] Comparative Example 3 The paraquat production wastewater from Example 1 was treated using subcritical oxidation with or without a catalyst, as follows: Step 1: Subcritical oxidation of mixed wastewater.

[0068] Pyridine production wastewater and paraquat production wastewater were mixed at a 5:2 ratio, and the pH was adjusted to 3-5. The mixture was then directly introduced into a subcritical reactor, using air as the oxidant. 130 Nm³ of air was added to each ton of the mixed water. 3 / h air, controlled reaction temperature 270℃, pressure 6MPa, reaction time 2h, no catalyst.

[0069] Step 2: Direct discharge and residue disposal.

[0070] After the reaction is complete, the oxidizing solution is cooled to room temperature and the indicators are directly tested. If the COD, pyridine, and cyanide do not meet the standards, the oxidation is repeated. The salts (ammonium chloride, sodium chloride) in the oxidizing solution dissolve directly in the water. There is no adsorption and recovery of pyridine or salt separation steps. The high-salt wastewater cannot be biochemically treated, and direct discharge will cause salt pollution.

[0071] Treatment efficiency: Pyridine and its derivatives removal rate: 10-20%; Cyanide removal rate: 85%-90%; COD removal rate: 80%-85%.

[0072] Resource recovery: No pyridine recovery, salts dissolve in water and cannot be separated and recovered, resulting in resource waste and salt pollution; Compliance status: Effluent COD>500mg / L, pyridine>1800mg / L, cyanide>330mg / L, which does not meet the standards, and the circulating oxidation leads to a sharp increase in energy consumption.

[0073] Therefore, this invention employs the aforementioned method for the resource-based treatment of paraquat wastewater through subcritical water catalytic oxidation to improve the removal rate of organic matter and cyanide from pyridine production wastewater. It boasts high resource recovery rates, with pyridine recovery ≥95% and ammonium chloride recovery meeting agricultural standards, achieving resource recycling. Biodegradability is improved, with the wastewater's BOD / COD ≥0.3 after pyridine recovery, allowing for conventional biochemical treatment to meet discharge standards and reduce treatment costs. The operation is stable and reliable, with clearly defined process parameters and controllable reaction conditions, making it suitable for industrial applications.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for the resource-based treatment of paraquat wastewater, characterized in that, The process includes the following steps: Step 1, treating pyridine production wastewater by subcritical water catalytic oxidation. The pyridine production wastewater is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out under the action of a noble metal catalyst to obtain an oxidized liquid. Step 2, pyridine recovery: The oxidizing liquid in Step 1 is used to adsorb pyridine at room temperature using two-stage special resins, and then desorbed using 50%~100% methanol or acetone. The desorbed liquid is recovered by distillation, and pyridine is recovered simultaneously during distillation. Step 3, Biochemical Treatment: The wastewater after adsorption in Step 2 is treated using a biochemical anaerobic-aerobic process to meet discharge standards; Step 4: Treat the paraquat production wastewater by adjusting the pH of the wastewater to 2-4 and diluting the wastewater to reduce the concentration of chemical oxygen demand in the wastewater, thus avoiding overheating and salting out. Step 5, subcritical water catalytic oxidation: The wastewater treated in step 4 is placed under subcritical conditions, with air as the oxidant, and the reaction is carried out under the action of rare earth catalyst. Step 6, Salt Recovery: The oxidizing liquid from Step 5 is separated into ammonium chloride and sodium chloride by thermal cyclic evaporation, and the recovered ammonium chloride meets the standards.

2. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 1, the oxidant dosage is 105-150 Nm per ton of water. 3 / h air, reaction temperature 250-280℃, reaction pressure corresponding to temperature, reaction time 0.8~2.5h.

3. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 1, the noble metal catalyst is at least one of ruthenium, rhodium, palladium, and platinum, supported on titanium dioxide or zirconium dioxide, with a loading rate of 0.5% to 2%.

4. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 2, the resin adsorption rate is 1 BV / h, the pyridine content in the wastewater after adsorption is <5 mg / L, and the desorption rate is 3 BV / h.

5. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 4, the chemical oxygen demand (COD) concentration of the diluted wastewater is 15,000-20,000 mg / L.

6. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 5, the oxidant dosage is 60-80 Nm per ton of dilution water. 3 / h air, reaction temperature 260-280℃, reaction pressure corresponding to temperature, reaction time 1~3h.

7. The method for resource-based treatment of paraquat wastewater according to claim 1, characterized in that: In step 5, the rare earth catalyst is at least one of cerium and vanadium, supported on a titanium dioxide or zirconium dioxide support, with a loading rate of 1% to 5%.

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