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CN-117800363-B - Method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater

CN117800363BCN 117800363 BCN117800363 BCN 117800363BCN-117800363-B

Abstract

The invention discloses a method for separating and purifying sodium chloride and sodium acetate from mesotrione wastewater, which comprises the steps of carrying out primary distillation and filtration at 65-80 ℃ on the mesotrione wastewater to obtain sodium chloride, adding an additive into filtrate, wherein the solubility of the additive is at least higher than that of sodium acetate and is not decomposed below 100 ℃, carrying out secondary distillation and filtration at 65-80 ℃, filtering a filter cake to obtain a mixed salt, crystallizing and filtering the first mother liquor at room temperature to obtain sodium acetate trihydrate and a second mother liquor, adding methanol into the mixed salt to carry out reflux washing, filtering at 40-50 ℃ to obtain sodium chloride filter cake, distilling the third mother liquor to recover methanol, filtering at room temperature to separate sodium acetate, and conveying the fourth mother liquor back to a methanol reflux washing section for application. The method has good separation and purification effects, high purity and yield, and is convenient for engineering application.

Inventors

  • CHEN CAN
  • LIU WEIDONG
  • DU SHENGHUA
  • LIU HUAN
  • LIU WEI
  • LI MIN
  • ZENG XUEYUN
  • WANG ZHENZHOU
  • YIN HONGKUI

Assignees

  • 湖南海利常德农药化工有限公司

Dates

Publication Date
20260505
Application Date
20231107

Claims (7)

  1. 1. The method for separating and purifying sodium chloride and sodium acetate from the sulfenamide wastewater is characterized by comprising the following steps of: (1) Extracting sodium chloride, namely filtering a fraction with 75-80% of the distilled water yield of the sulfenamide wastewater at 65-80 ℃ to obtain a concentrated solution, wherein a filter cake is sodium chloride, and the content of the sodium chloride is 98-99%; (2) Extracting sodium acetate trihydrate, namely adding an additive with the mass of 1% -3% of that of the filtrate into the filtrate after filtering sodium chloride, wherein the solubility of the additive is at least higher than that of sodium acetate and is not decomposed below 100 ℃, continuously distilling out 3% -5% of the total amount of raw water, carrying out heat preservation and filtering at 65-80 ℃, and crystallizing and filtering a filter cake which is mixed salt of sodium chloride and sodium acetate trihydrate at room temperature to obtain a first mother solution at room temperature to obtain sodium acetate trihydrate and a second mother solution, wherein the additive is one of zinc chloride, sucrose and urea, and the content of the sodium acetate trihydrate is more than 95%; (3) And (3) treating mixed salt, namely adding methanol with the mass which is 1.5-2 times that of the mixed salt into the mixed salt of sodium chloride and sodium acetate trihydrate obtained in the step (2) for reflux washing, filtering at 40-50 ℃ to obtain sodium chloride filter cake and third mother liquor, distilling the third mother liquor to recover methanol, filtering at room temperature to separate sodium acetate, and returning the obtained fourth mother liquor to a methanol reflux washing section for reuse, wherein the content of the sodium acetate is more than 95%.
  2. 2. The method for separating and purifying sodium chloride and sodium acetate from sulfenamide waste water according to claim 1, wherein in the step (2), the sodium acetate trihydrate obtained after crystallization and filtration at room temperature is taken as a byproduct for takeaway.
  3. 3. The method for separating and purifying sodium chloride and sodium acetate from sulfenamide waste water according to claim 1, wherein in the step (2), the second mother liquor is dried by harrowing, and the obtained harrow is subjected to dry distillation and biochemical treatment.
  4. 4. The method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater according to claim 1, wherein in the step (3), the reflux washing time is 15-40 min, and the third mother liquor is distilled to recover 90% of methanol.
  5. 5. The method for separating and purifying sodium chloride and sodium acetate from the sulfenamide wastewater, which is disclosed in claim 1, is characterized in that the sodium chloride filter cake obtained in the step (3) is mixed with the sodium chloride filter cake obtained in the step (1) and dried, the content of the sodium chloride filter cake reaches more than 98% and can be used as a byproduct industrial salt for take-out, and the sodium acetate can be used as a byproduct sodium acetate for take-out in the step (3).
  6. 6. The method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater according to claim 1, wherein in the step (1), the sulfenamide wastewater is wastewater obtained by alkaline hydrolysis, stripping and Fenton treatment of sulfenamide raw water.
  7. 7. The method for separating and purifying sodium chloride and sodium acetate from sulfenamide waste water according to claim 1, wherein the distilled fraction is subjected to biochemical treatment in the step (1) and the step (2).

Description

Method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater Technical Field The invention relates to the field of pretreatment of three wastes of pesticides, in particular to a method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater. Background The sulfenamide (2 ',4' -dichloro-5 ' - (4-difluoromethyl-4, 5-dihydro-3-methyl-5-oxo-1H-1, 2, 4-triazole-1-yl) methylsulfonylamines) is a novel triazolinone type wheat field herbicide developed by the American FMC company, and the product has special effects on removing weeds with resistance to sulfonylureas, and has the characteristics of safety of aftercrop, wide herbicide spectrum, small consumption and quick weed killing. The dosage of the pesticide is continuously expanded in the international market, and the pesticide is sold in the global of over 3 hundred million dollars in 2020, so that the pesticide has become a popular variety in the pesticide market. The product has six steps of process components, and generates 38.48 tons of wastewater per ton of product, wherein the salt content in the wastewater is about 10-13%, the main content of sodium chloride is about 6-7%, and the sodium acetate is about 4-5%. The cost of the pretreated mixed salt used as the hazardous waste is too high, wherein sodium acetate is a good biochemical carbon source, the market price is about 2400 yuan/ton, and if the two salts can be separated and purified to take out as byproducts, considerable economic benefits can be brought. The common salt separation method mainly comprises distillation crystallization and nanofiltration membrane separation. Because the salt in the sulfentrazone wastewater is sodium chloride and sodium acetate, which are monovalent salts, the nanofiltration membrane is only suitable for separating ions with different valence states, and obviously, the nanofiltration membrane separation method cannot be adopted. The separation and recovery of sulfanilamide, sodium acetate and sodium chloride in sulfanilamide wastewater are disclosed by Shortblin et al (Hebei chemical industry, separation and recovery of sulfanilamide, sodium acetate and sodium chloride in sulfanilamide waste liquid, 1996 (4) 57-58), and the method is summarized as two steps: ① And (3) discharging and settling when the mother solution is concentrated to rho=1.23, opening a door to discharge clear liquid, separating out sediment sodium chloride, adding sodium hydroxide into the clear liquid to adjust the pH value to be=9-10 by ②, pumping the clear liquid into a concentration tank, heating and concentrating to a proper concentration, and naturally cooling the concentrated solution in a crystallization tank after the sodium chloride is completely deposited to obtain sodium acetate trihydrate. The method for separating sodium acetate in the literature adopts a method for separating sodium acetate by adding sodium hydroxide by utilizing the homoionic effect, and has the following problems that ① side door positions can be just opened at a solid-liquid interface, ② can not completely separate solid from liquid by sedimentation, precipitation of sodium acetate trihydrate can affect the purity of sodium chloride if the separation is not complete, ③ can completely deposit sodium chloride, and the point of completely separating two salts is basically unknown, so that the method has no operability, the applicant verifies the process, the yield and purity of the separated sodium chloride and sodium acetate are not high, the yield of the sodium chloride is only 40%, the purity is 65%, the yield of the sodium acetate trihydrate is 30%, and the purity is 50%, and the requirements of the sodium acetate as a byproduct can not be met. Disclosure of Invention The invention aims to solve the technical problems of overcoming the defects of the prior art and providing the method for separating and purifying sodium chloride and sodium acetate from the mesotrione wastewater, which has good separation and purification effects, high purity and high yield and is convenient for industrial application. In order to solve the technical problems, the invention adopts the following technical scheme. A method for separating and purifying sodium chloride and sodium acetate from sulfenamide wastewater comprises the following steps: (1) Extracting sodium chloride, namely filtering a fraction with 75% -80% of the distilled water yield of the sulfenamide wastewater at 65 ℃ -80 ℃ and obtaining a filter cake of sodium chloride; (2) Extracting sodium acetate trihydrate, namely adding an additive with the mass of 1% -3% of that of the filtrate into the filtrate after filtering sodium chloride, wherein the solubility of the additive is at least higher than that of sodium acetate and is not decomposed below 100 ℃, continuously distilling out 3% -5% of the total amount of raw water, carrying out heat preservation and filtration at 65-80 ℃, and crystallizing an