A method for resourceful treatment of natural citral production wastewater

Abstract

The application discloses a kind of natural citral production wastewater resource treatment method, steps are, natural citral production wastewater is acidified using sulfuric acid and is fully aerated;Neutralize to neutral after the wastewater of aeration using sodium hydroxide;Evaporate crystallization, there is sodium sulfate precipitation, centrifugal separation, obtain sodium sulfate coarse salt and evaporation completion liquid;The sodium sulfate coarse salt is washed with water, centrifugal separation is carried out, respectively obtain solid and washing liquid, the solid is dried to obtain sodium sulphate, the washing liquid is evaporated with the liquid obtained in step 3 together crystallization;Evaporation completion liquid is cooled and frozen crystallization, stirring is opened in the freezing process, there is mirabilite precipitation, mirabilite and frozen crystallization mother liquor are obtained after centrifugal separation, and frozen crystallization mother liquor is removed citral production purification process.The application, not only can recover inorganic salt in wastewater, residual citral in wastewater can also be returned to purification process for further recovery, so that the natural citral production wastewater resource, harmless treatment is realized.

Description

Technical Field

[0001] This invention belongs to the field of wastewater resource utilization technology, and particularly relates to a method for the resource utilization of wastewater from the production of natural citral. Background Technology

[0002] Citral is a colorless or slightly yellow transparent liquid with a strong lemon aroma. It has a wide range of uses, including in the preparation of artificial lemon oil and citrus oil, as well as in the production of other citrus flavorings, fruit flavorings, and flavorings for foods such as cherries, coffee, and plums. Furthermore, citral is a raw material for the synthesis of ionones, methyl ionones, and dihydrodamascone, and can also be used as an organic raw material to be reduced to citronellol, nerol, and geraniol, and can be converted into citrate. In the pharmaceutical industry, citral is used to manufacture vitamins A and E, and is also a raw material for phytol.

[0003] Natural citral is found in lemongrass oil, citrus oil, litsea cubeba oil, and verbena oil. In natural essential oils such as lemongrass oil and litsea cubeba oil, the citral content can reach 70%–80%, and crude citral can be obtained by distillation. For higher-quality citral, the sodium bisulfite method can be used for purification, producing crystalline citral sodium bisulfite adducts, which are then obtained by vacuum distillation. This method is currently the main method for producing citral in my country.

[0004] The purification of citral using the sodium bisulfite method introduces compounds such as sodium bicarbonate, sodium sulfite, and sodium hydroxide. These compounds remain in the distillation wastewater after citral recovery, making citral production wastewater a high-salt, high-COD wastewater that is difficult to treat. Treatment of natural citral production wastewater typically employs only a zero-discharge evaporation crystallization process. This not only presents challenges in treatment difficulty and high costs, but also results in the solids generated at the end of the evaporation process being classified as hazardous waste, significantly increasing production costs for enterprises. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-cost method for the resource-based treatment of wastewater from the production of natural citral.

[0006] The technical solution of this invention is summarized as follows: A method for the resource-based treatment of wastewater from the production of natural citral includes the following steps: Step 1: Add sulfuric acid solution to the wastewater from natural citral production to make the pH 3-5; Step 2: Aerate the liquid obtained in Step 1 at an aeration rate of 20-40 m / s. 3 / h, the aeration rate is 20 to 40 times the mass of sodium sulfite in the liquid obtained in step 1; Step 3: Add sodium hydroxide aqueous solution to the liquid obtained in step 2 to make the pH value 7~8; Step 4: Evaporate and crystallize the liquid obtained in Step 3. Sodium sulfate will precipitate out. When the volume of the evaporated liquid is 1 / 5 to 1 / 3 of the volume of the liquid obtained in Step 3, centrifuge to separate the crude sodium sulfate and the evaporated liquid. Step 5: Wash the crude sodium sulfate with water, centrifuge to separate the solid and washing liquid, dry the solid to obtain sodium sulfate, and evaporate the washing liquid and the liquid obtained in step 3 together to crystallize. Step 6: Cool the evaporated liquid obtained in Step 4 to freeze and crystallize. Stirring is turned on during the freezing process, and sodium sulfate is precipitated. After centrifugation, sodium sulfate and frozen crystallization mother liquor are obtained. The frozen crystallization mother liquor is then purified by citral production.

[0007] Preferably, the concentration of the sulfuric acid aqueous solution in step 1 is 0.1~0.5 mol / L, and the pH is 4.

[0008] Preferably, the aeration rate in step 2 is 30m. 3 / h, the aeration rate is 30 times the mass of sodium sulfite in the liquid obtained in step 1.

[0009] Preferably, the concentration of the sodium hydroxide aqueous solution in step 3 is 0.1~0.5 mol / L.

[0010] Preferably, the evaporation and crystallization temperature in step 4 is 103℃~108℃.

[0011] Preferably, in step 5, the amount of water added is 0.5 to 1 times the mass of the crude sodium sulfate; the temperature of the water is 40°C to 50°C.

[0012] Preferably, the freezing temperature in step 6 is -5℃ to 0℃, and the stirring rate is 200r / min to 300r / min.

[0013] Advantages of this invention: This invention addresses the problem of high treatment costs for natural citral wastewater by proposing a method for the resource-based treatment of natural citral production wastewater. The method of this invention can obtain sodium sulfate, mirabilite, and citral enriched solution, achieving the goal of resource-based treatment of citral production wastewater, reducing the pollution and harm caused by natural citral wastewater to the environment, and simultaneously recovering citral from the wastewater, thereby reducing the production cost of citral. Attached Figure Description

[0014] Figure 1 Flowchart of the process for resource-based treatment of wastewater from the production of natural citral. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments.

[0016] First, the components of the natural citral production wastewater (experimental sample) used in each embodiment were analyzed to enable those skilled in the art to better understand the present invention, but this does not limit the present invention.

[0017] The main components of the wastewater from the production of natural citral are detailed in Table 1.

[0018] Table 1 Composition of wastewater from natural citral production

[0019] Secondly, the above-mentioned natural citral production wastewater was treated using the technical solution of the present invention at a room temperature of 20℃~30℃.

[0020] Example 1 A method for the resource-based treatment of wastewater from the production of natural citral includes the following steps: Step 1: Add a 0.3 mol / L sulfuric acid solution to a 3L beaker containing 2L of natural citral production wastewater to adjust the pH to 4; this allows the sodium hydroxide and sodium carbonate to be completely converted to sodium sulfate. Stop adding acid, resulting in a mixed acidic aqueous solution containing sodium sulfate, sodium sulfite, and COD. The chemical reactions involved in the wastewater acidification are as follows: 2NaOH + H₂SO₄ = Na₂SO₄ + H₂O; Na2CO3+H2SO4=Na2SO4+CO2+H2O; Step 2: Aerate the liquid obtained in Step 1 at an aeration rate of 30 m / s. 3 / h, the aeration rate is 30 times the mass of sodium sulfite in the liquid obtained in step 1; The chemical reactions involved in the air oxidation process are as follows: 2Na₂SO₃ + O₂ = 2Na₂SO₄; The resulting solution is an acidic aqueous solution of sodium sulfate and COD.

[0021] Step 3: Add a 0.3 mol / L sodium hydroxide aqueous solution to the liquid obtained in Step 2 to make the pH values ​​7, 7.3, 7.7, and 8 respectively; stop adding the sodium hydroxide aqueous solution to obtain a neutral solution containing sodium sulfate and COD; the chemical reactions involved are as follows: H₂SO₄ + 2NaOH = Na₂SO₄ + H₂O; Liquid phase determination: After step 3, neutral solutions at different pH values ​​were taken and the percentage content (unit wt%) of sodium carbonate, sodium sulfite and sodium sulfate in the filtrate was determined by chemical method, as shown in Table 2.

[0022] Table 2. Percentages of carbonate, sulfite, and sulfate ions after step 3.

[0023] After step 3 is completed, the resulting solution is a neutral solution containing only sodium sulfate and COD.

[0024] Step 4: Evaporate and crystallize the liquid obtained in Step 3 at a temperature of 105°C. Sodium sulfate will precipitate out. When the volume of the evaporated liquid is 1 / 4 of the volume of the liquid obtained in Step 3, centrifuge to separate the liquid and obtain crude sodium sulfate and the evaporated liquid. Step 5: Wash the crude sodium sulfate with water, the amount of water being 0.8 times the mass of the crude sodium sulfate; the water temperature is 45℃, centrifuge to separate the solid and washing liquid, the solid is dried to obtain sodium sulfate, and the washing liquid and the liquid obtained in step 3 are evaporated together to crystallize. Step 6: Cool the evaporated liquid obtained in Step 4 to freeze and crystallize. The freezing temperatures are 0℃, -2℃, -3℃, and -5℃. Stirring is turned on during the freezing process at a speed of 250 r / min. Glauber's salt is precipitated. After centrifugation, Glauber's salt and frozen crystallization mother liquor are obtained. The frozen crystallization mother liquor is returned to the citral production and purification process.

[0025] Liquid phase determination: After the freeze crystallization was completed, solutions at different temperatures were taken and the contents of sodium sulfate and COD in the mother liquor were determined by chemical method, as shown in Table 3.

[0026] Table 3. Content of sodium sulfate and COD in the mother liquor of freeze crystallization

[0027] The mother liquor for cryo-crystallization is a neutral solution containing only a small amount of sodium sulfate and a large amount of COD.

[0028] Example 2 A method for the resource-based treatment of wastewater from the production of natural citral includes the following steps: Step 1: Add a 0.1 mol / L sulfuric acid aqueous solution to a 3L beaker containing 2L of natural citral production wastewater to make the pH=5; Step 2: Aerate the liquid obtained in Step 1 at an aeration rate of 20 m / s². 3 / h, the aeration rate is 20 times the mass of sodium sulfite in the liquid obtained in step 1; Step 3: Add a 0.1 mol / L sodium hydroxide aqueous solution to the liquid obtained in Step 2 to make the pH value = 7; Step 4: Evaporate and crystallize the liquid obtained in Step 3 at a temperature of 103°C. Sodium sulfate will precipitate out. When the volume of the evaporated liquid is 1 / 5 of the volume of the liquid obtained in Step 3, centrifuge to separate the liquid and obtain crude sodium sulfate and the evaporated liquid. Step 5: Wash the crude sodium sulfate with water, the amount of water being 0.5 times the mass of the crude sodium sulfate; the water temperature is 40℃; centrifuge to separate the solid and washing liquid, respectively; dry the solid to obtain sodium sulfate, and evaporate the washing liquid and the liquid obtained in step 3 together to crystallize. Step 6: Cool the evaporated liquid obtained in Step 4 to freeze and crystallize at a temperature of -5°C. Stirring is started during the freezing process at a speed of 200 r / min. Glauber's salt is precipitated. After centrifugation, Glauber's salt and frozen crystallization mother liquor are obtained. The frozen crystallization mother liquor is returned to the citral production and purification process.

[0029] Example 3 A method for the resource-based treatment of wastewater from the production of natural citral includes the following steps: Step 1: Add a 0.5 mol / L sulfuric acid aqueous solution to a 3L beaker containing 2L of natural citral production wastewater to make the pH=3; Step 2: Aerate the liquid obtained in Step 1 at an aeration rate of 40 m / s. 3 / h, the aeration rate is 40 times the mass of sodium sulfite in the liquid obtained in step 1; Step 3: Add a 0.5 mol / L sodium hydroxide aqueous solution to the liquid obtained in Step 2 to make the pH value = 8; Step 4: Evaporate and crystallize the liquid obtained in Step 3 at a temperature of 108°C. Sodium sulfate will precipitate out. When the volume of the evaporated liquid is 1 / 3 of the volume of the liquid obtained in Step 3, centrifuge to separate the liquid and obtain crude sodium sulfate and the evaporated liquid. Step 5: Wash the crude sodium sulfate with water, the amount of water being 1 times the mass of the crude sodium sulfate; the water temperature is 50°C; centrifuge to separate the solid and washing liquid, respectively; dry the solid to obtain sodium sulfate; evaporate and crystallize the washing liquid together with the liquid obtained in step 3. Step 6: Cool the evaporated liquid obtained in Step 4 to freeze and crystallize at a temperature of 0°C. Stirring is started during the freezing process at a speed of 300 r / min. Glauber's salt is precipitated. After centrifugation, Glauber's salt and frozen crystallization mother liquor are obtained. The frozen crystallization mother liquor is returned to the citral production and purification process.

[0030] The mother liquor obtained from the freeze crystallization process in step 6 is returned to the citral production and purification process. Since the solution is a neutral solution containing only a small amount of sodium sulfate and a large amount of COD, it will not affect the citral purification process. Moreover, the enrichment of COD in the solution is beneficial for further recovery of citral from the wastewater.

[0031] Adjusting the process parameters according to the present invention can achieve the goal of resource-based treatment of wastewater from natural citral production. The present invention has been described above as exemplary. It should be noted that any simple modifications, alterations, or equivalent substitutions that can be made by those skilled in the art without creative effort, without departing from the core of the present invention, fall within the protection scope of the present invention.

Claims

1. A method for the resource-based treatment of wastewater from the production of natural citral, characterized in that... Includes the following steps: Step 1: Add sulfuric acid solution to the wastewater from natural citral production to make the pH 3-5; Step 2: Aerate the liquid obtained in Step 1 at an aeration rate of 20-40 m / s. 3 / h, the aeration rate is 20 to 40 times the mass of sodium sulfite in the liquid obtained in step 1; Step 3: Add sodium hydroxide aqueous solution to the liquid obtained in step 2 to make the pH value 7~8; Step 4: Evaporate and crystallize the liquid obtained in Step 3. Sodium sulfate will precipitate out. When the volume of the evaporated liquid is 1 / 5 to 1 / 3 of the volume of the liquid obtained in Step 3, centrifuge to separate the crude sodium sulfate and the evaporated liquid. Step 5: Wash the crude sodium sulfate with water, centrifuge to separate the solid and washing liquid, dry the solid to obtain sodium sulfate, and evaporate the washing liquid and the liquid obtained in step 3 together to crystallize. Step 6: Cool the evaporated liquid obtained in Step 4 to freeze and crystallize. Stirring is turned on during the freezing process, and sodium sulfate is precipitated. After centrifugation, sodium sulfate and frozen crystallization mother liquor are obtained. The frozen crystallization mother liquor is then purified by citral production.

2. The processing method according to claim 1, characterized in that... The concentration of the sulfuric acid aqueous solution in step 1 is 0.1~0.5 mol / L, and the pH is 4.

3. The processing method according to claim 1, characterized in that... In step 2, the aeration rate is 30m. 3 / h, the aeration rate is 30 times the mass of sodium sulfite in the liquid obtained in step 1.

4. The processing method according to claim 1, characterized in that... In step 3, the concentration of the sodium hydroxide aqueous solution is 0.1~0.5 mol / L.

5. The processing method according to claim 1, characterized in that... In step 4, the evaporation and crystallization temperature is 103℃~108℃.

6. The processing method according to claim 1, characterized in that... In step 5, the amount of water added is 0.5 to 1 times the mass of the crude sodium sulfate salt; the temperature of the water is 40℃ to 50℃.

7. The processing method according to claim 1, characterized in that... In step 6, the freezing temperature is -5℃ to 0℃, and the stirring rate is 200r / min to 300r / min.

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