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CN-121990735-A - Purifying treatment process for pyrazolone production wastewater

CN121990735ACN 121990735 ACN121990735 ACN 121990735ACN-121990735-A

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a purifying treatment process for pyrazolone production wastewater. Aiming at the characteristics of high COD, high total nitrogen, high salt and difficult biochemical degradation of pyrazolone production wastewater, the invention constructs a full-flow synergistic process of targeting pretreatment-resource recovery-mild detoxification-deep purification, acetonitrile is efficiently recovered through composite extraction and pervaporation membrane separation, and the magnesium-aluminum composite catalyst catalyzes alkaline thermal hydrolysis, and the heterocyclic compound is degraded in a mild ring opening manner, so that the biodegradability is improved. The photocatalysis and Fenton-like combination continuously generate hydroxyl free radicals, deeply oxidize and mineralize refractory organic matters, and the modified biochar adsorbs residual micromolecules and chromaticity, so that the risks of metal ion residues and secondary pollution are reduced. The oxidation-adsorption coupling strategy integrates the strong degradation capability of advanced oxidation and the adsorption purification function of biochar, thereby realizing the beneficial improvement of treatment efficiency, ensuring the standard discharge of wastewater, and simultaneously recovering resources, reducing the cost and having environmental and economic benefits.

Inventors

  • WANG WEIGUO
  • XU JUN
  • ZHOU YANG
  • WANG KAI
  • LI WEI
  • HE YIFAN
  • ZHENG YUAN
  • WANG TAO
  • YAN JUNJIANG
  • REN YANG
  • LIU ENZHOU
  • CHEN SHUAI
  • GUO YANG
  • YANG DONGYUAN
  • HU JUN
  • FENG AILING
  • GAO TING
  • Guo you
  • HE YU
  • JI HUI
  • LI JUNPING
  • YAO ZHONGDONG
  • YAO NING
  • WANG YING

Assignees

  • 陕西大美化工科技有限公司

Dates

Publication Date
20260508
Application Date
20260410

Claims (10)

  1. 1. The purifying treatment process of pyrazolone production wastewater, wherein the wastewater is mother liquor and washing wastewater generated in the process of preparing pyrazolone by condensing methyl hydrazine and ethyl acetoacetate under the assistance of acetonitrile in a closed loop manner, is characterized by comprising the following steps of: S1, pretreatment and targeted impurity removal: filtering and regulating pH of the wastewater, and performing two-stage countercurrent extraction by adopting a composite extractant to remove pyrazolone and hydrophobic byproducts in the wastewater so as to obtain a raffinate phase; s2, high-efficiency recovery of acetonitrile: Performing vacuum rectification and pervaporation membrane separation on the extract Yu Xiangyi obtained in the step S1 for the times, and recovering acetonitrile, wherein the vacuum rectification is performed to obtain an acetonitrile crude product, residual liquid at the bottom of the vacuum rectification enters a pervaporation unit, and PDMS (polydimethylsiloxane) pervaporation membrane is used for separation to remove acetonitrile content in the residual liquid to be less than or equal to 200mg/L; S3, mild denitrification and destructive detoxification: Performing base-catalyzed thermal hydrolysis on the wastewater subjected to acetonitrile removal in the presence of a magnesium-aluminum composite catalyst, and converting residual nitriles into organic acids and ring-opening degradation of heterocyclic compounds; S4, reducing concentration and salt recycling: Sequentially carrying out ultrafiltration and nanofiltration treatment on the hydrolyzed wastewater, carrying out mechanical vapor recompression evaporation on nanofiltration produced water, and crystallizing to obtain industrial ammonium sulfate or ammonium chloride, wherein evaporated condensate water is recycled; S5, deep purification: And (3) combining the nanofiltration concentrated solution obtained in the step (S4) with mechanical steam recompression evaporation mother solution, and sequentially carrying out photocatalytic coupling Fenton-like oxidation and modified biochar fixed bed adsorption, wherein the treated effluent reaches the emission or recycling standard.
  2. 2. The purifying treatment process of pyrazolone production wastewater according to claim 1, wherein the compound extractant in the step S1 is a mixture of tributyl phosphate and kerosene, the volume ratio is 1 (3-5), and the extraction ratio is 1 (2-5).
  3. 3. The purification treatment process of pyrazolone production wastewater according to claim 1, wherein the vacuum degree of the reduced pressure rectification in the step S2 is-0.06 to-0.08 MPa, the theoretical plate number is 25-30, and the reflux ratio is 1.5-2.5; And the operation temperature of the PDMS (polydimethylsiloxane) pervaporation membrane adopted by the pervaporation unit is 60-70 ℃.
  4. 4. The purification treatment process of pyrazolone production wastewater according to claim 1, wherein the magnesium-aluminum composite catalyst in the step S3 is MgO-Al 2 O 3 , the crystal form is gamma-Al 2 O 3 loaded MgO, the particle size is 50-100 μm, and the adding amount is 0.5-1 g/L; The magnesium-aluminum composite catalyst is prepared by a coprecipitation method, and is prepared by mixing and dissolving magnesium salt and aluminum salt according to a molar ratio of Mg to Al of 1 (2-3), dropwise adding ammonia water to adjust pH to 9.0-10.0, filtering, washing and drying after precipitation aging, and roasting at 550-650 ℃ for 3-4 hours; The conditions of the base catalytic thermal hydrolysis are that the pH is 11.0-12.0, the reaction temperature is 110-125 ℃, the pressure is 0.15-0.20 MPa, and the reaction time is 60-80 min.
  5. 5. The purification treatment process of pyrazolone production wastewater according to claim 1, wherein the nanofiltration in the step S4 adopts a surface modified alkali-resistant nanofiltration membrane with a molecular weight cut-off of 200-400 da; The mechanical vapor recompression evaporation adopts a titanium alloy evaporator, the evaporation temperature is 70-85 ℃, and the vacuum degree is-0.07 to-0.09 MPa.
  6. 6. The purifying treatment process of pyrazolone production wastewater according to claim 1, wherein in the step S5, coagulant aid is added into the combined wastewater for homogenization pretreatment before the photocatalytic coupling Fenton-like oxidation enters the reactor, the catalyst adopted by the photocatalytic coupling Fenton-like oxidation is g-C 3 N 4 /modified TiO 2 composite catalyst, the adding amount is 0.3-0.8 g/L, the oxidant is H 2 O 2 , the adding amount is 500-800 mg/L, the UV-C is taken as an activating light source, and the reaction time is 30-40 min.
  7. 7. The purification treatment process of pyrazolone production wastewater according to claim 6, wherein the preparation of the g-C 3 N 4 /modified TiO 2 composite catalyst comprises the following steps: (1) Uniformly mixing urea and thiourea according to the mass ratio of 9:1, placing the mixture in a crucible with a cover, roasting the mixture for 2.5 to 3.5 hours at the temperature of 500 to 600 ℃, heating the mixture at the temperature of 5 ℃ per minute, cooling the mixture, performing ball milling, and sieving the mixture with a 200-mesh sieve to obtain g-C 3 N 4 ; (2) Dispersing the g-C 3 N 4 in an ethanol-water mixed solution according to the mass volume ratio of 1g (20-30 mL), performing ultrasonic treatment for 30-40 min, then dropwise adding tetrabutyl titanate, adjusting the pH to 3.0-3.5 by using dilute hydrochloric acid, and stirring in a 60 ℃ water bath for 2-3 h to obtain a g-C 3 N 4 -TiO 2 suspension; (3) Adding ethyl silicate into the suspension, adjusting the pH to 8.5-9.0 by ammonia water, stirring for 1-3 hours at 40-50 ℃ to form a uniform SiO 2 protective film, filtering, washing with deionized water to be neutral, drying at 75-85 ℃, and roasting at 400 ℃ for 2 hours.
  8. 8. The purifying treatment process of pyrazolone production wastewater according to claim 1, wherein the photocatalytic coupling Fenton-like oxidation adopts an industrial ultraviolet reactor, the reactor is arranged in a multi-lamp-tube matrix, the distance between lamp tubes is 15-20 cm, a guide plate is arranged in the reactor, and the light penetration depth is 5-15 cm.
  9. 9. The purification treatment process of pyrazolone production wastewater according to claim 1, wherein the adsorbent of the modified biochar fixed bed in the step S5 is corncob-based modified carbon, and the airspeed is 1-2 h -1 .
  10. 10. The purification treatment process of pyrazolone production wastewater according to claim 9, wherein the preparation of the corncob-based modified carbon comprises the following steps: 1) Crushing corncob, sieving with a 10-20 mesh sieve, washing to remove sediment, drying at 100-110 ℃, then placing in a tube furnace, protecting with N 2 , carbonizing at 400-500 ℃ for 2-3 hours, heating at a temperature rate of 6-10 ℃ per minute, and naturally cooling to obtain corncob-based raw biochar; 2) Mixing corncob-based raw biochar with 10% NaOH solution according to a solid-to-liquid ratio of 1 (4-6), soaking for 2-3 hours at 75-85 ℃, filtering, and drying at 60-70 ℃; 3) And (3) activating for 1-2 hours at 500-600 ℃ in an N 2 atmosphere, cooling to room temperature after activation, soaking for 1-2 hours at room temperature by using 5% H 2 O 2 solution, washing to be neutral, drying at 75-85 ℃, and screening for 1-3 mm to obtain the corncob-based modified biochar.

Description

Purifying treatment process for pyrazolone production wastewater Technical Field The invention belongs to the technical field of wastewater treatment, and particularly relates to a purifying treatment process for pyrazolone production wastewater. Background Pyrazolone is an important intermediate of pesticides, medicines and dyes, and is prepared by condensation cyclization of hydrazine and ketone/ester. The existing main flow process is an acetonitrile auxiliary reaction method, which can improve the selectivity and reduce the impurities, but the wastewater after the reaction has the following characteristics: Residual acetonitrile, pyrazolone intermediate and byproduct salts (sodium chloride/sodium sulfate); COD is high (8000-15000 mg/L), total nitrogen is high, and chromaticity is deep; poor biodegradability (B/C < 0.2), and difficulty in reaching standard in traditional biochemistry; The direct discharge is heavy in pollution and wastes acetonitrile and salt separation resources. At present, the treatment method for pyrazolone production wastewater mainly comprises a physicochemical method and a biological treatment method, wherein the physicochemical method comprises extraction, distillation, adsorption and the like, and the physicochemical method can remove part of organic matters, but has the problems of low resource recovery rate, high treatment cost, easiness in secondary pollution and the like. Biological treatment methods are widely studied due to low cost and environmental friendliness, but the high-salt environment and the complex heterocyclic compounds in the pyrazolone wastewater have strong inhibition effect on microorganisms. The biological treatment efficiency is low, and the standard emission is difficult to realize. In order to improve biodegradability, dilution pretreatment is often required, which not only increases the treatment scale and cost, but also reduces the possibility of resource recovery. In addition, although the simple advanced oxidation technology can effectively degrade refractory organic matters, the problems of high oxidant consumption, high operation cost, incomplete mineralization and the like exist, and toxic and harmful intermediate products can be generated, so that the increasingly strict environmental protection requirements cannot be met. Therefore, development of an efficient, economical and environment-friendly pyrazolone production wastewater treatment process for realizing deep removal of pollutants and effective recovery of resources is a problem to be solved urgently in the field at present. Disclosure of Invention The invention aims at solving the existing problems and provides a purifying treatment process for pyrazolone production wastewater. The invention is realized by the following technical scheme: The purifying treatment process of pyrazolone production wastewater, wherein the wastewater is mother liquor and washing wastewater generated in the process of preparing pyrazolone by condensing methyl hydrazine and ethyl acetoacetate under the assistance of acetonitrile in a closed loop manner, the COD of the wastewater is 8000-35000 mg/L, and the salt content is 5-20%, and the purifying treatment process comprises the following steps: S1, pretreatment and targeted impurity removal: Filtering the wastewater and adjusting the pH value (5.5-6.5), and adopting a composite extractant to perform two-stage countercurrent extraction to remove pyrazolone and hydrophobic byproducts in the wastewater so as to obtain a raffinate phase; s2, high-efficiency recovery of acetonitrile: Performing vacuum rectification and pervaporation membrane separation on the extract Yu Xiangyi obtained in the step S1 for the times, and recovering acetonitrile, wherein the vacuum rectification is performed to obtain an acetonitrile crude product, residual liquid at the bottom of the vacuum rectification enters a pervaporation unit, and PDMS (polydimethylsiloxane) pervaporation membrane is used for separation to remove acetonitrile content in the residual liquid to be less than or equal to 200mg/L; S3, mild denitrification and destructive detoxification: Performing base catalytic thermal hydrolysis on the wastewater after acetonitrile removal in the presence of a magnesium-aluminum composite catalyst, converting residual nitriles into organic acids, and performing ring opening degradation on heterocyclic compounds to improve the biodegradability of the wastewater; S4, reducing concentration and salt recycling: sequentially carrying out ultrafiltration and nanofiltration treatment on the hydrolyzed wastewater, merging nanofiltration concentrated solution into the step S5 for deep purification, carrying out mechanical vapor recompression evaporation on nanofiltration produced water, and crystallizing to obtain industrial ammonium sulfate or ammonium chloride, wherein evaporated condensate water is recycled; S5, deep purification: And (3) combining the nanofiltration concentrated solutio