A method for treating bismuth subsalicylate wastewater

Abstract

This invention relates to the field of wastewater treatment technology, specifically a method for treating bismuth hyposalicylate wastewater. The invention first adjusts the pH of the bismuth hyposalicylate wastewater to ensure that the Bi concentration is less than 1 mg / L. Then, by specifying the ratio of salicylic acid to hydrogen peroxide in the wastewater, the oxidation effect and utilization rate of ozone are significantly improved, ultimately effectively increasing the removal rate of salicylic acid. Furthermore, by controlling the pH of the reaction system during the reaction process, this invention can treat bismuth hyposalicylate wastewater with extremely high concentrations of salicylic acid and COD, achieving a salicylic acid removal rate greater than 95% and ensuring that the effluent COD consistently meets national standards. The process is simple and convenient, suitable for batch treatment of production line wastewater. The degree of salicylic acid removal through wastewater oxidation can be easily judged by observing the color fading, ensuring that each batch of treated wastewater consistently meets standards. Batch testing using analytical instruments is unnecessary, significantly reducing analytical testing costs.

Description

Technical Field

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

[0002] Bismuth subsalicylate, also known as basic bismuth salicylate, is a commonly used digestive medication for the treatment of diarrhea, gastritis, colitis, and other digestive disorders. The mechanism of action of bismuth subsalicylate is as follows: ① Anti-inflammatory and anti-infective effects: It can inhibit inflammation, absorb and kill pathogens. ② Antitoxin effects: It can adsorb and kill pathogens, absorb and neutralize enterotoxins. ③ Antisecretive effects: It can inhibit intestinal mucosal secretion and reduce the accumulation of fluid in the intestinal lumen. ④ Mucosal protective effects: It coats the mucosal surface, providing direct protection and aiding in the recovery and regeneration of digestive tract epithelial cells. Therefore, basic bismuth subsalicylate is mainly used in pediatrics for the treatment of digestive tract diseases such as diarrhea and gastritis.

[0003] Patent CN103183608A discloses a method for preparing bismuth hyposalicylate. The patent involves pulverizing bismuth oxide to a specified average particle size, controlling the initial excess coefficient of salicylic acid in the salicylic acid aqueous solution to be 0.05~0.3, gradually adding the pulverized bismuth oxide to the salicylic acid aqueous solution heated to a predetermined temperature, and allowing the salicylic acid and bismuth oxide to react under the predetermined temperature and light-proof and sealed conditions. After the reaction is completed, the mixture is filtered and dried to obtain the bismuth hyposalicylate product.

[0004] Patent CN103435476A discloses a method for preparing bismuth subsalicylate, a synthetic bismuth raw material. The patent specifies a liquid-to-solid ratio, in which analytical grade bismuth hydroxide powder is added to pure water to form a uniform suspension. Salicylic acid is added in a certain amount to the bismuth hydroxide suspension heated to a predetermined temperature within a specified time. The salicylic acid and bismuth hydroxide are reacted under the conditions of maintaining the predetermined temperature and being protected from light and sealed. After the reaction is completed, the product is filtered, washed with boiling water, vacuum dried, pulverized, sieved, and then stored in the dark as the finished bismuth subsalicylate.

[0005] The wastewater generated during the preparation of bismuth hyposalicylate contains bismuth hyposalicylate, excess salicylic acid, bismuth ions, and other residues. It has a low pH, high COD, contains bismuth metal ions, and is prone to yellowing. Currently, there are no literature or patents specifically addressing the treatment of bismuth hyposalicylate wastewater; therefore, it is necessary to develop a superior treatment method for bismuth hyposalicylate.

[0006] In addition, salicylic acid is generally detected using liquid chromatography-ultraviolet (LC-UV) method. The analytical instruments are expensive and the detection steps are cumbersome and complicated, which is not conducive to the sample testing of each batch of wastewater treated in the production workshop. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a method for treating bismuth hyposalicylate wastewater. The treatment method provided by the present invention can treat bismuth hyposalicylate wastewater, with a high salicylic acid removal rate and a low COD content in the treated wastewater.

[0008] This invention provides a method for treating bismuth subsalicylate wastewater, comprising the following steps:

[0009] S1) After adjusting the pH of the bismuth subsalicylate wastewater to 8.5-9, filter it to obtain the filtrate;

[0010] S2) Mix the filtrate obtained in step S1) with hydrogen peroxide, and introduce ozone into it to carry out the reaction; the mass ratio of salicylic acid in the filtrate to the mass of hydrogen peroxide is 1:(2~10).

[0011] This invention first adjusts the pH of bismuth hyposalicylate wastewater to 8.5-9 and then filters it to obtain a filtrate. Specifically, the pH of the bismuth hyposalicylate wastewater is first adjusted to 8.5-9 with an alkali, stirred for 0.5-1 h, and then filtered to obtain a filtrate. The alkali used in this invention is selected from at least one of sodium hydroxide or calcium hydroxide. Preferably, the pH of the bismuth hyposalicylate wastewater is adjusted with calcium hydroxide. Calcium hydroxide not only adjusts the pH but also provides calcium ions. During the oxidation process of salicylic acid, some of it degrades into oxalic acid. Calcium ions react with oxalic acid to form calcium oxalate precipitate, allowing the oxalic acid produced during the reaction to settle promptly, thus promoting oxidation efficiency.

[0012] The filtration described in this invention uses filter media with a pore size of 40-60 micrometers. In some embodiments of this invention, the filtration is performed using a bag filter. This invention adjusts the pH of the bismuth hyposalicylate wastewater to cause bismuth ions in the wastewater to form bismuth hydroxide precipitate. By selecting an appropriate pore size, bismuth hydroxide is recovered through filtration, ensuring that the Bi concentration in the filtrate is <1 mg / L.

[0013] After obtaining the filtrate, this invention mixes it with hydrogen peroxide and then introduces ozone to react. The mass ratio of salicylic acid in the filtrate to hydrogen peroxide is 1:(2~10). The mass concentration of the hydrogen peroxide in this invention is 40 wt%~60 wt%, preferably 50 wt%. The ozone flow rate in this invention is 25 g / h~35 g / h. The reaction time in this invention, i.e., the time for introducing the ozone, is 1 h~5 h. This invention, by specifying the ratio of salicylic acid to hydrogen peroxide in the filtrate derived from bismuth subsalicylate wastewater, first adds a certain amount of hydrogen peroxide and then introduces ozone for oxidation treatment, effectively improving the removal rate of salicylic acid.

[0014] In some embodiments of the present invention, calcium hydroxide is used to control the reaction at a pH of 8-9 during the ozone reaction process. Specifically, calcium hydroxide is added to the reaction system to control the reaction at a pH of 8-9. In some embodiments of the present invention, for bismuth hyposalicylate wastewater with a salicylic acid concentration of 1500 mg / L or higher and a COD concentration of 2000 mg / L or higher, the treatment method for bismuth hyposalicylate wastewater described in the present invention is used. By using calcium hydroxide to control the pH value of the reaction, the oxalic acid produced in the reaction process settles down in time, promoting oxidation efficiency. Thus, the present invention can still have excellent treatment effect on bismuth hyposalicylate wastewater with particularly high salicylic acid and COD concentrations. If sodium hydroxide is used to control the pH, it can only adjust the pH and cannot provide calcium ions, so the oxalic acid produced in the reaction process cannot settle down in time. During ozone oxidation, the salicylic acid needs to be completely degraded into carbon dioxide, resulting in lower oxidation efficiency.

[0015] In some embodiments of the present invention, before step S2), ferric chloride solution is added dropwise to the filtrate obtained in step S1) for color development, making the solution appear light reddish-brown; the mass ratio of ferric chloride in the ferric chloride solution to salicylic acid in the filtrate is 1:(1000~10000). The present invention utilizes the color development through the complexation of ferric chloride with the phenolic hydroxyl groups in the salicylic acid structure. By observing the fading of the color, the degree of salicylic acid removal from the wastewater can be easily determined, ensuring that each batch of wastewater consistently meets standards after treatment. This eliminates the need for batch testing using analytical instruments, significantly reducing analytical testing costs.

[0016] This invention provides a method for treating bismuth hyposalicylate wastewater. First, the pH of the bismuth hyposalicylate wastewater is adjusted to ensure that the Bi concentration in the wastewater is less than 1 mg / L. Then, by specifying the ratio of salicylic acid to hydrogen peroxide in the wastewater, a certain amount of hydrogen peroxide is added first, followed by ozone reaction. This significantly improves the oxidation effect and utilization rate of ozone, saves treatment costs, and ultimately effectively increases the removal rate of salicylic acid. Furthermore, by controlling the pH of the reaction system within a certain range during the reaction process, this invention can treat bismuth hyposalicylate wastewater with extremely high concentrations of salicylic acid and COD, achieving a salicylic acid removal rate greater than 95% and ensuring that the effluent COD stably meets the standard of <100 mg / L in GB8978-1996 "Integrated Wastewater Discharge Standard". The process is simple and convenient, with few steps and easy operation. It is suitable for batch treatment of production wastewater in production lines. Furthermore, the degree of salicylic acid removal from the wastewater can be easily judged by observing the color fading. This ensures that each batch of wastewater can consistently meet the standards after treatment, eliminating the need for batch testing with analytical instruments and greatly saving on analysis and testing costs. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method for treating bismuth subsalicylate wastewater according to the present invention. Detailed Implementation

[0018] This invention discloses a method for treating bismuth subsalicylate wastewater. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The method and application of this invention have been described through preferred embodiments; those skilled in the art can clearly modify or appropriately change and combine the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0019] This invention is generally in accordance with Figure 1 The process shown is used to treat bismuth subsalicylate wastewater. Figure 1 This is a flowchart of the method for treating bismuth subsalicylate wastewater according to the present invention.

[0020] The present invention will be further described below with reference to the embodiments:

[0021] Example 1

[0022] The wastewater produced by a company's bismuth salicylate production line has a Bi content of 307 mg / L, a salicylic acid content of 860 mg / L, and a COD of 1545 mg / L. Measure 500 mL of wastewater into a 1 L beaker, add 32% NaOH solution to adjust pH to 8.5, stir and react for 0.5 h, filter with 50 micron filter paper, Bi < 1 mg / L, add 0.43 mg of 33% ferric chloride solution to the filtrate to make the solution light reddish-brown, add 4.3 g of 50% hydrogen peroxide, and then introduce ozone oxidation. The ozone generator is rated at 30 g / h, the oxygen tank pressure is 15 MPa, the gas valve is opened to 0.1 MPa during use, the oxygen flow rate is 1.3 L / min, and the ozone gas flow rate is 30 g / h. After 4.5 h, the effluent is colorless and clear, the salicylic acid content is 2.1 mg / L, and the COD is 56 mg / L, meeting the standard of COD < 100 mg / L in GB8978-1996 "Integrated Wastewater Discharge Standard".

[0023] Example 2

[0024] The wastewater produced by a company's bismuth salicylate production line has a Bi concentration of 203 mg / L, a salicylic acid content of 648 mg / L, and a COD of 1180 mg / L. 500 mL of wastewater was measured into a 1 L beaker, and 32% NaOH solution was added to adjust the pH to 8.8. The mixture was stirred and reacted for 0.5 h. After filtration with 50-micron filter paper, Bi < 1 mg / L. 0.324 mg of 33% ferric chloride solution was added to the filtrate to make the solution turn light reddish-brown. 3.24 g of 50% hydrogen peroxide was added, and then ozone oxidation was introduced. The ozone generator was rated at 30 g / h, the oxygen tank pressure was 15 MPa, and the gas valve was opened to 0.1 MPa during use. The oxygen flow rate was 1.3 L / min, and the ozone gas flow rate was 30 g / h. After 4 h, the effluent was colorless and clear, with a salicylic acid content of 1.3 mg / L and COD of 48 mg / L, meeting the standard of COD < 100 mg / L in GB8978-1996 "Integrated Wastewater Discharge Standard".

[0025] Example 3

[0026] The wastewater from a company's bismuth subsalicylate production line has a Bi concentration of 307 mg / L, a salicylic acid content of 860 mg / L, and a COD of 1545 mg / L. 500 mL of the wastewater was measured into a 1 L beaker, and 2.13 g / L of Ca(OH)₂ was added to adjust the pH to 8.75. The mixture was stirred for 0.5 h, and 0.43 mg of 33% ferric chloride solution was added to make the solution appear light reddish-brown. 4.3 g of 50% hydrogen peroxide was then added, followed by ozone oxidation. The ozone generator was rated for 30 g / h, the oxygen tank pressure was 15 MPa, and the gas valve was opened to 0.1 MPa during operation. The oxygen flow rate was 1.3 L / min, and the ozone flow rate was 30 g / h. The pH was monitored during the reaction, and 0.21 g / L of Ca(OH)₂ was added cumulatively to maintain the pH of the reaction solution at 8.5-9. After 3 h, the reddish-brown color faded, and the solution was filtered using 50-micron filter paper. The effluent has a Bi content of <1 mg / L, a salicylic acid content of 1.6 mg / L, and a COD of 50 mg / L, meeting the standard of COD <100 mg / L in GB8978-1996 "Integrated Wastewater Discharge Standard".

[0027] Example 4

[0028] The wastewater from a certain company containing bismuth subsalicylate has a pH of 1.45, Bi content of 403 mg / L, salicylic acid content of 1551 mg / L, and COD of 2458 mg / L. Measure 500 mL of wastewater into a 1 L beaker, add 2.39 g / L Ca(OH)2 to adjust the pH to 8.55, stir the reaction for 0.5 h, add 2.35 mg of 33% ferric chloride solution to make the solution turn light reddish-brown, add 7.8 g of 50% hydrogen peroxide, and then introduce ozone for oxidation. The ozone generator is rated at 30 g / h, the oxygen tank pressure is 15 MPa, the gas valve is opened to 0.1 MPa during use, the oxygen flow rate is 1.3 L / min, and the ozone gas flow rate is 30 g / h. Monitor the pH during the reaction process, and add a cumulative 0.48 g / L of Ca(OH)2 to make the pH of the reaction solution 8.5~9. After 3.5 h, the reddish-brown color fades, and the solution is filtered using 50-micron filter paper. The effluent has a Bi content of <1 mg / L, a salicylic acid content of 1.9 mg / L, and a COD of 55 mg / L, meeting the standard of COD <100 mg / L in GB8978-1996 "Integrated Wastewater Discharge Standard".

[0029] Comparative Example 1

[0030] The wastewater produced by a company's bismuth salicylate production line has a Bi concentration of 307 mg / L, a salicylic acid content of 860 mg / L, and a COD of 1545 mg / L. 500 mL of wastewater was measured into a 1 L beaker, and 32% NaOH solution was added to adjust the pH to 8.5. The mixture was stirred and reacted for 0.5 h. After filtration with 50-micron filter paper, Bi < 1 mg / L. 0.43 mg of 33% ferric chloride solution was added to the filtrate to make the solution turn light reddish-brown. Then, ozone oxidation was directly introduced. The ozone generator was rated at 30 g / h, the oxygen tank pressure was 15 MPa, and the gas valve was opened to 0.1 MPa during use. The oxygen flow rate was 1.3 L / min, and the ozone gas flow rate was 30 g / h. After 4.5 h, the effluent was light reddish-brown, with a salicylic acid content of 256 mg / L and a COD of 340 mg / L, which did not meet the COD < 100 mg / L standard of GB8978-1996 "Integrated Wastewater Discharge Standard".

[0031] Comparative Example 2

[0032] The wastewater from a company's bismuth subsalicylate production line has a Bi concentration of 307 mg / L, a salicylic acid concentration of 860 mg / L, and a COD of 1545 mg / L. 500 mL of the wastewater was measured into a 1 L beaker, and 32% NaOH solution was added to adjust the pH to 8.5. The mixture was stirred for 0.5 h, filtered through 50-micron filter paper, and the Bi concentration was found to be <1 mg / L. 0.43 mg of 33% ferric chloride solution was added to the filtrate to make it turn a light reddish-brown color. Then, 4.3 g of 50% hydrogen peroxide was added for oxidation. After 4.5 h, the effluent was light reddish-brown, with a salicylic acid concentration of 857 mg / L and a COD of 1540 mg / L, failing to meet the COD <100 mg / L standard of GB8978-1996 "Integrated Wastewater Discharge Standard".

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating bismuth subsalicylate wastewater, characterized in that, Includes the following steps: S1) The pH of the bismuth subsalicylate wastewater was adjusted to 8.5-9 using calcium hydroxide and then filtered to obtain the filtrate; S2) Mix the filtrate obtained in step S1) with hydrogen peroxide, and introduce ozone into it to carry out the reaction; the mass ratio of salicylic acid in the filtrate to the mass of hydrogen peroxide is 1:(2~10).

2. The processing method according to claim 1, characterized in that, In step S2), the mass concentration of the hydrogen peroxide is 40 wt% to 60 wt%.

3. The processing method according to claim 1, characterized in that, In step S2), the ozone flow rate is 25 g / h to 35 g / h.

4. The processing method according to claim 1, characterized in that, In step S2), the reaction time is 1 h to 5 h.

5. The processing method according to claim 1, characterized in that, In step S2), calcium hydroxide is used to control the reaction to be maintained at a pH of 8-9.

6. The processing method according to claim 5, characterized in that, In step S1), the concentration of salicylic acid in the bismuth hyposalicylate wastewater is above 1500 mg / L, and the COD in the bismuth hyposalicylate wastewater is above 2000 mg / L.

7. The processing method according to claim 1, characterized in that, Step S1) Specifically, the pH of the bismuth subsalicylate wastewater is adjusted to 8.5-9, stirred for 0.5-1 h, and then filtered to obtain the filtrate.

8. The processing method according to claim 1, characterized in that, Before proceeding to step S2), ferric chloride solution is added dropwise to the filtrate obtained in step S1 to develop the color, making the solution appear light reddish-brown.

9. The processing method according to claim 8, characterized in that, The mass ratio of ferric chloride in the ferric chloride solution to salicylic acid in the filtrate is 1:(1000~10000).

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