A method for treating irbesartan production wastewater

Abstract

This invention provides a method for treating irbesartan production wastewater, the main steps of which are: (1) removing irbesartan-related substances from the wastewater; (2) removing residual solvents from the wastewater using a stripping tower; and (3) introducing the remaining wastewater into a biochemical system for degradation. This method can avoid the precipitation of solids that may occur during the treatment of irbesartan production wastewater, and can effectively reduce the COD value at the end of the wastewater treatment, thus reducing the difficulty of treating irbesartan production wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating irbesartan production wastewater. Background Technology

[0002] The main components of irbesartan production wastewater are water, ethanol, irbesartan, irbesartan-related impurities, and a small amount of insoluble impurities. This wastewater primarily originates from the centrifugation mother liquor during the crystallization and purification step of crude irbesartan in the irbesartan production process. In the irbesartan preparation process, after the synthesis of free irbesartan, it is treated with acid and purified by recrystallization using an ethanol-water mixed solvent. Therefore, the main solutes in this wastewater are organic molecules containing the irbesartan skeleton, such as free irbesartan and irbesartan impurity A (Formula I) and irbesartan impurity B (Formula II).

[0003]

[0004] Irbesartan and its derivatives have poor water solubility under acidic and neutral conditions, making them prone to precipitation, while they are soluble in water under alkaline conditions. Generally, because the refining process of irbesartan involves acid treatment, the raw wastewater from irbesartan production is acidic. However, due to the presence of a certain amount of ethanol mixed in the raw wastewater, irbesartan and related substances are soluble in the raw wastewater and will not precipitate temporarily. However, when the raw wastewater enters the Fenton reaction tank of the biological treatment system, due to the dilution of the ethanol system and the increase in acidity, irbesartan and its derivatives will precipitate in solid form in the reaction tank, resulting in a large amount of suspended solids. These suspended solids can easily clog the pipelines of the biological treatment system, requiring manual cleaning and deblocking, thus affecting production efficiency. On the other hand, due to the structural characteristics of irbesartan and its derivatives, biodegradation is slow, leading to a longer residence time of wastewater in the biological treatment system, resulting in low wastewater treatment efficiency and increasing the difficulty of wastewater treatment. Summary of the Invention

[0005] To address this issue, we attempted to extract organic impurities using water-based, albeit unsuitable, solvents such as dichloromethane. Residual solvent was then removed via a stripping tower before the wastewater was directed into the biological treatment system. This process effectively shortens the wastewater's residence time in the biological treatment system and results in lower COD levels in the final wastewater. Furthermore, the unsuitable solvent used to extract the organic impurities can be recovered and reused through distillation. After crystallization, the organic impurities are separated into solid and liquid phases using a centrifuge or plate and frame filter press, effectively reducing pollutant emissions.

[0006] The process for treating irbesartan production wastewater is as follows:

[0007] The irbesartan production wastewater was filtered and then extracted using dichloromethane in an extraction tower, and a dichloromethane layer and a water layer were collected.

[0008] The dichloromethane layer was recovered, and the solvent was removed under reduced pressure to obtain crude irbesartan. The stripping tower was preheated until the top temperature reached 92°C. Then, the water layer was passed into the stripping tower to extract the residual organic solvent in the water layer until the COD value of the remaining wastewater was lower than 15,000.

[0009] The remaining wastewater after separation by the stripping tower is fed into a biochemical system for degradation.

[0010] As mentioned earlier, the main source of wastewater from irbesartan production is the mother liquor generated from centrifugal filtration after recrystallization, the final step in the irbesartan production process. In the production process, the solvent used for irbesartan recrystallization is ethanol / water, and there is also an acid treatment step. Therefore, irbesartan production wastewater is an acidic ethanol-water waste liquid mainly containing irbesartan and irbesartan impurities, and may also contain other impurities such as activated carbon. Under the current process, the ethanol content (volume ratio) of irbesartan production wastewater ranges from approximately 20-35%, and the pH is 2-3.

[0011] Based on the above component analysis, the irbesartan production wastewater was first filtered to remove any solid impurities that might have entered the wastewater before treatment. Subsequently, the filtered wastewater was mixed with an organic solvent for extraction. This step aimed to remove most of the organic impurities in the irbesartan production wastewater, ensuring the smooth progress of subsequent biochemical reaction tank treatment steps. The organic impurities removed using the organic solvent mainly included irbesartan, irbesartan impurity A, and irbesartan impurity B. The organic solvent used was dichloromethane or chloroform.

[0012] After extraction, the mixture is separated into an organic phase and an aqueous phase. The organic phase is subjected to reduced pressure to remove the solvent, yielding crude irbesartan containing some impurities. The remaining aqueous phase still contains some organic solvent, which is then passed into a stripping column for organic solvent recovery. During the stripping process, the column top temperature is controlled at 78.3-100℃, preferably 84℃-93℃. When a significant rise in the column top temperature is observed compared to a stable state, the stripping is considered essentially complete and operation can be stopped. The recovered organic solvent can be processed and reused in production.

[0013] After stripping, most of the organic solvents in the wastewater have been removed. The remaining wastewater is then cooled to room temperature and introduced into a biological treatment system. The biological system consists of an equalization tank, a Fenton reactor, a deep hydrolysis tank, a HIC anaerobic tower, a primary A tank, a primary O tank, secondary sedimentation tank 1, secondary A tank, secondary O tank, secondary sedimentation tank 2, a flotation unit, and an effluent outlet. The wastewater undergoes oxidation treatment in the acidic Fenton reactor, with a pH of approximately 2-3. Since organic impurities have been separated, no solids are precipitated, and there is no impact on the pipelines. The wastewater remains in the biological system for approximately 35 days to meet standards, with a final COD level of 100-200. In contrast, if the wastewater is directly degraded without treatment, the final COD level would be 400-600, and it would require more than 40 days to remain in the biological system. Implementation

[0014] Example

[0015] A batch of irbesartan production wastewater was sampled and tested; the ethanol concentration was [missing information].

[0016] The specific steps for wastewater treatment are as follows:

[0017] Step 1: The raw wastewater from irbesartan production is filtered, and then extracted and separated using dichloromethane in an extraction tower. The dichloromethane layer and the water layer are collected in the lower and upper layers of the extraction tower, respectively.

[0018] Step 2: Recover the dichloromethane layer and remove the solvent under reduced pressure to obtain crude irbesartan; introduce steam into the stripping tower and preheat the stripping tower until the top temperature reaches 92°C. Then, keep the valve opening constant and feed the water layer obtained from the previous step into the stripping tower for stripping to separate the residual ethanol and dichloromethane in the water layer; after the feed is completed, observe the top temperature of the tower. When the top temperature rises significantly, stop the steam supply and sample the extracted wastewater for testing. The COD value should not exceed 15000.

[0019] Step 3: The remaining water layer after separation by the stripping tower is fed into the biological treatment system for further treatment. The biological treatment system includes an equalization tank, a Fenton reactor, a deep hydrolysis tank, a HIC anaerobic tower, a primary A tank, a primary O tank, secondary sedimentation tank 1, a secondary A tank, a secondary O tank, a secondary sedimentation tank 2, an air flotation unit, and an effluent outlet. The acid tank in the Fenton reactor contains approximately 7% hydrogen peroxide and 20% sulfuric acid. After the acid reaction is completed, the wastewater enters the iron-carbon micro-electrolysis tank, and finally, caustic soda is added to adjust the pH to 8. The wastewater passes through the above sections sequentially in the biological treatment system, with a total retention time of 35 days. At the end of the biological treatment system, the COD value is measured to be less than 20.

Claims

1. A method for treating irbesartan production wastewater, comprising the following steps: filtering irbesartan production wastewater containing ethanol, irbesartan, compounds of formula I and formula II, and then extracting the wastewater in an extraction tower using dichloromethane to obtain a dichloromethane layer and an aqueous layer; recovering the dichloromethane layer, removing the solvent under reduced pressure to obtain crude irbesartan; preheating a stripping tower until the top temperature is 92°C, and then feeding the aqueous layer into the stripping tower to extract the residual organic solvent in the aqueous layer until the COD value of the remaining wastewater is less than 15000; and feeding the remaining wastewater separated by the stripping tower into a biochemical system for degradation until the COD value is less than 200.

2. The method of claim 1, wherein the biochemical system comprises a Fenton reaction treatment tank.

3. The method of claim 1, wherein the residence time of the remaining wastewater in the biochemical system is 35 days. ​ 。 ​ ​

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