An environmentally friendly treatment process for glyphosate production mother liquor

Abstract

The present invention discloses an environmentally friendly process for treating glyphosate production mother liquor. This process involves modifying chitosan to produce modified chitosan aerogel, which is then mixed with biochar as an adsorbent to treat the glyphosate production mother liquor. Compared with existing technologies, the present process offers a high adsorption rate, excellent adsorption effects, and is simple, cost-effective, and easy to operate. The modified chitosan aerogel has a higher porosity and large specific surface area, and can form a complex with glyphosate, thereby enhancing adsorption and resulting in a more effective treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of glyphosate mother liquor treatment methods, and in particular to an environmentally friendly treatment process for glyphosate production mother liquor. Background Art

[0002] Glyphosate production mother liquor is a liquid waste generated during the glyphosate production process. Its composition is complex, typically containing 0.5%-4% glyphosate, 15%-20% salts (primarily sodium chloride, but also possible disodium hydrogen phosphate and sodium pyrophosphate), as well as difficult-to-degrade organic impurities such as formaldehyde, formic acid, glyphosate, and diglyphosate. It also contains certain amounts of pollutants such as COD (chemical oxygen demand) and total phosphorus. If discharged directly without effective treatment, it can cause numerous hazards, including water pollution, causing COD and total phosphorus levels in receiving water bodies to exceed standards, leading to eutrophication and disrupting the aquatic ecological balance. Entry into the soil can alter soil physical and chemical properties, affect the structure and function of soil microbial communities, and lead to a decline in soil fertility. It can also accumulate and be transmitted through the food chain, potentially harming the human nervous and endocrine systems, posing risks of carcinogenesis and teratogenicity.

[0003] Currently, methods for treating glyphosate in wastewater include incineration, advanced oxidation, membrane separation, biochemical methods, and adsorption. The concentrated mother liquor is incinerated at high temperatures to convert phosphorus into sodium pyrophosphate or disodium hydrogen phosphate. However, high salt content can easily lead to coking in the incinerator, and the product purity is low. Wet oxidation oxidizes organic matter under high temperature and pressure, with a phosphorus recovery rate of 70%-80%. Pre-desalination with membrane technology is necessary to improve product quality. Membrane technologies such as nanofiltration and reverse osmosis are used to separate inorganic salts (such as sodium chloride) and organic matter from the mother liquor. The salt content of the mother liquor in the glycine method can be reduced to 1%, and the dilute mother liquor in the IDA method can be recycled for use in the synthesis process. This method is energy-efficient and improves concentration efficiency, but the separated dilute liquor still requires evaporation, which is costly. Biochemical methods utilize the biochemical reactions within microorganisms to decompose toxic and hazardous substances in wastewater and solid waste. However, microbial cultivation requires long time, high pretreatment requirements for glyphosate wastewater, and a lengthy process.

[0004] CN1648131A describes a process for treating the mother liquor obtained from the glycine synthesis of glyphosate. This process follows the following steps: First, ammonia gas is introduced into the glyphosate mother liquor to adjust the pH to 7-10. The solution is then allowed to stand for stratification, and the triethylamine in the upper layer is recovered. Next, the lower layer of the mother liquor is subjected to vacuum distillation, cooled, and filtered to remove ammonium chloride crystals, ultimately yielding concentrated glyphosate ammonium salt. This glyphosate mother liquor treatment process offers significant advantages. It not only reduces production costs but also effectively saves energy, protects the environment, and enhances the efficacy of the resulting aqueous solution. By eliminating the need for deacidification after the hydrolysis and desolvation step and instead directly adding a certain amount of alkali to adjust the pH, the yield of technical glyphosate can be increased. Furthermore, this approach improves equipment utilization and reduces energy consumption.

[0005] CN119219249A discloses a multi-stage membrane treatment method for glyphosate mother liquor, comprising the following specific steps: Step 1: Adjusting the pH of the glyphosate mother liquor to recover the triethylamine therein. Step 2: Subjecting the glyphosate salt-containing waste liquor to wet catalytic oxidation treatment to ultimately produce a concentrate and a permeate. Step 3: After filtering the concentrate, transferring it to a primary membrane for separation, resulting in a primary retentate and a primary permeate. Step 4: Transferring the primary retentate to a secondary membrane for further separation, resulting in a secondary retentate and a secondary permeate. Step 5: Transferring the secondary retentate to a tertiary membrane for further separation, resulting in a tertiary retentate and a tertiary permeate. Step 6: Mixing the permeate with the primary permeate, the secondary permeate, and the tertiary permeate to ultimately produce a sodium chloride solution. Step 7: Mixing the tertiary retentate, the secondary retentate, and the primary retentate, followed by cooling and crystallization, results in separation of the glyphosate technical product and a filtrate. The filtrate is mixed with the concentrate and then continues to circulate through the multi-stage membrane treatment.

[0006] Membrane separation methods use selectively permeable inorganic or polymeric materials as the separation layer. However, glyphosate wastewater has high salinity, high organic matter content, and phosphate content. These characteristics can easily lead to membrane pore clogging when treated using membrane separation methods. Biological methods also have certain limitations for treating glyphosate wastewater. Due to the high total phosphorus concentration in glyphosate wastewater, biological methods are not ideal for treating this type of wastewater. In contrast, adsorption methods have attracted widespread attention due to their simplicity, low cost, ease of operation, and high removal rates for most pollutants. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide an environmentally friendly treatment process for glyphosate production mother liquor.

[0008] Physical adsorption is able to treat glyphosate production wastewater primarily because it utilizes the porous structure and large specific surface area of ​​the adsorbent, adsorbing glyphosate molecules onto the adsorbent surface through intermolecular forces (van der Waals forces). This adsorption process does not involve a chemical reaction, the structural changes of the adsorbate molecules are minimal, and the adsorption energy is low. The adsorbed substance can easily detach from the adsorbent surface under appropriate conditions (such as elevated temperature). However, physical adsorption treatment of glyphosate wastewater has some drawbacks. First, the adsorption capacity of the adsorbent is limited, making it difficult to meet the treatment requirements of high-concentration wastewater. Second, the adsorbent's selectivity is poor, and other impurities in the wastewater, such as sodium chloride and phosphate, may affect the adsorption effect.

[0009] Therefore, the present invention provides an environmentally friendly treatment process for glyphosate production mother liquor. Biochar is mixed with modified chitosan aerogel to produce an adsorbent, which is then applied to the treatment of glyphosate production mother liquor. Biochar has a highly developed pore structure and a large specific surface area, enabling it to effectively adsorb organic pollutants such as glyphosate. Furthermore, the biochar surface is rich in oxygen-containing functional groups (such as hydroxyl and carboxyl groups), which can chemically adsorb glyphosate molecules, further enhancing the adsorption effect. Chitosan is a natural polysaccharide material with abundant amino (-NH2) and hydroxyl (-OH) groups. These functional groups can undergo electrostatic adsorption and hydrogen bonding with glyphosate molecules, thereby achieving the adsorption effect. By modifying it and cross-linking it with (3-chloropropyl)-trimethylammonium chloride and metal ions, a modified chitosan aerogel is obtained. Since glyphosate is negatively charged, the modified chitosan with cationic properties can enhance the adsorption effect. The alkaline properties of glyphosate come from the electrons of nitrogen (N) and oxygen (O) atoms in its molecular structure, which can coordinate with metal ions (M + ) form chemical bonds, resulting in a thermodynamically stable complex. Modified chitosan further enhances adsorption due to its ability to form a stable complex. Using adsorbents to treat glyphosate production mother liquor effectively removes harmful substances from wastewater. The method is simple and environmentally friendly, with low adsorbent cost and high adsorption efficiency.

[0010] To achieve the above object, the present invention provides an environmentally friendly treatment process for glyphosate production mother liquor, comprising the following steps:

[0011] S1. Mix chitosan with sodium hydroxide aqueous solution and isopropyl alcohol, heat and stir for 2-4 hours, then add (3-chloropropyl)-trimethylammonium chloride aqueous solution, continue stirring for 4-8 hours after heating, add dilute hydrochloric acid to adjust the pH to neutral, filter, wash, dry and use in the next step;

[0012] S2. Add the product of the previous step to water, mix well, heat and stir for 2-4 hours, add metal salt solution and epichlorohydrin, continue stirring for 2-4 hours, let gel stand, filter, wash and freeze-dry to obtain modified chitosan aerogel;

[0013] S3. Adjust the pH of the glyphosate production mother liquor with dilute hydrochloric acid, filter it, mix the modified chitosan aerogel with biochar and add it to the filtrate as an adsorbent. After oscillation adsorption and filtration, detect the content of various substances in the filtrate and discharge it after meeting the standards.

[0014] Furthermore, the mass ratio of the chitosan to the sodium hydroxide solution, isopropyl alcohol, and (3-chloropropyl)-trimethylammonium chloride solution is 1:2-5:5-10:5-8.

[0015] Furthermore, the temperature range of the heating and stirring is 40-50°C.

[0016] Furthermore, the temperature range of the heating is 70-80°C.

[0017] Furthermore, in step S2, the mass ratio of the product of the previous step to the metal salt solution and epichlorohydrin is 1:2-10:0.02-0.1.

[0018] Furthermore, the mass ratio of the modified chitosan aerogel to biochar is 1 to 5:1.

[0019] Furthermore, the solid-liquid ratio of the adsorbent to the filtrate is 50-100 g / L.

[0020] Furthermore, the pH is adjusted to a range of 2 to 3.

[0021] Furthermore, the temperature of the oscillating adsorption is 40-50° C., and the time is 10-30 hours.

[0022] Furthermore, the metal salt is one of ferric chloride, copper chloride or magnesium chloride.

[0023] Beneficial effects of the present invention:

[0024] 1. Compared with the prior art, the treatment process of the present invention has high adsorption rate, good adsorption effect, simple operation, low cost and easy operation.

[0025] 2. The present invention obtains an adsorbent by mixing biochar and modified chitosan aerogel, and applies it to the treatment of glyphosate production mother liquor. The surface of biochar is rich in oxygen-containing functional groups (such as hydroxyl groups, carboxyl groups, etc.), which can chemically adsorb with glyphosate molecules. Chitosan is cross-linked with (3-chloropropyl)-trimethylammonium chloride and metal ions to obtain modified chitosan aerogel. Since glyphosate is negatively charged, the modified chitosan with cationic properties can enhance the adsorption effect. The alkaline properties of glyphosate come from the electrons of nitrogen (N) and oxygen (O) atoms in its molecular structure, which can be coordinated with metal ions (M + ) form chemical bonds, thereby forming a thermodynamically stable complex. The modified chitosan can further enhance the adsorption effect because it can form a stable complex with it. DETAILED DESCRIPTION

[0026] (3-Chloropropyl)-trimethylammonium chloride, CAS: 1936-95-4.

[0027] Biochar, 300 mesh, model: YT-FM0615, Henan Coconut Carbon Environmental Protection Materials Co., Ltd.

[0028] Example 1

[0029] A process for environmentally friendly treatment of glyphosate production mother liquor comprises the following steps, measured in parts by weight:

[0030] S1. Mix 1 part of chitosan with 3 parts of 40 wt% sodium hydroxide aqueous solution and 8 parts of isopropanol, heat to 50°C and stir for 3 hours, then add 8 parts of 10 wt% (3-chloropropyl)-trimethylammonium chloride aqueous solution, heat to 75°C and continue stirring for 6 hours, add 1 mol / L dilute hydrochloric acid to adjust the pH to neutral, filter, wash, and dry the obtained product for the next step;

[0031] S2. Add 1 part of the product from the previous step to 50 parts of water, mix well, heat to 50° C. and stir for 3 hours, add 5 parts of 20 wt% ferric chloride aqueous solution and 0.05 parts of epichlorohydrin, continue stirring for 3 hours, let stand to gel, filter, wash and freeze-dry to obtain modified chitosan aerogel;

[0032] S3. Adjust the pH of the glyphosate production mother liquor to 2 with 1 mol / L dilute hydrochloric acid, filter, and obtain a filtrate; mix the modified chitosan aerogel and biochar in a mass ratio of 3:1 and add them to the filtrate as an adsorbent, with a solid-liquid ratio of the adsorbent to the filtrate of 80 g / L; adsorb at 45°C under oscillation for 24 hours, filter, and detect the content of various substances in the filtrate. Discharge after meeting the standards.

[0033] Example 2

[0034] The method is basically the same as Example 1, except that the 20 wt % ferric chloride aqueous solution is replaced by a 20 wt % cupric chloride aqueous solution.

[0035] Example 3

[0036] The method is basically the same as Example 1, except that the 20 wt % ferric chloride aqueous solution is replaced by a 20 wt % magnesium chloride aqueous solution.

[0037] Example 4

[0038] The process is basically the same as Example 1, except that the solid-liquid ratio of the adsorbent to the filtrate is 70 g / L.

[0039] Example 5

[0040] The process is basically the same as Example 1, except that the solid-liquid ratio of the adsorbent to the filtrate is 90 g / L.

[0041] Comparative Example 1

[0042] A process for environmentally friendly treatment of glyphosate production mother liquor comprises the following steps, measured in parts by weight:

[0043] The pH of the glyphosate production mother liquor was adjusted to 2 with 1 mol / L dilute hydrochloric acid and filtered. Biochar was added to the filtrate as an adsorbent with a solid-liquid ratio of adsorbent to filtrate of 80 g / L. After adsorption at 45°C for 24 hours, the content of each substance in the filtrate was detected after filtration and discharged after meeting the standards.

[0044] Comparative Example 2

[0045] A process for environmentally friendly treatment of glyphosate production mother liquor comprises the following steps, measured in parts by weight:

[0046] The pH of the glyphosate production mother liquor was adjusted to 2 with 1 mol / L dilute hydrochloric acid, filtered, and chitosan was added to the filtrate as an adsorbent with a solid-liquid ratio of adsorbent to filtrate of 80 g / L. After adsorption at 45°C for 24 hours, the content of each substance in the filtrate was detected after filtration and discharged after meeting the standards.

[0047] Comparative Example 3

[0048] A process for environmentally friendly treatment of glyphosate production mother liquor comprises the following steps, measured in parts by weight:

[0049] The pH of the glyphosate production mother liquor was adjusted to 2 with 1 mol / L dilute hydrochloric acid and filtered. Chitosan and biochar were mixed in a mass ratio of 3:1 and added to the filtrate as an adsorbent. The solid-liquid ratio of the adsorbent to the filtrate was 80 g / L. After oscillation adsorption at 45°C for 24 hours, the content of each substance in the filtrate was detected after filtration and discharged after meeting the standards.

[0050] Test Example 1

[0051] The glyphosate production mother liquor was tested before and after treatment to calculate the adsorption amount and adsorption rate, where adsorption amount = (initial glyphosate concentration - glyphosate concentration after adsorption) × solution volume / adsorbent mass, and adsorption rate = (initial glyphosate concentration - glyphosate concentration after adsorption) / initial glyphosate concentration × 100%.

[0052] Table 1 Glyphosate production mother liquor adsorption effect test results

[0053] Experimental plan Adsorption capacity / mg·g Adsorption rate / % Example 1 123.5 98.8 Example 2 118.1 94.5 Example 3 112.7 90.2 Example 4 110.5 88.4 Example 5 123.4 98.7 Comparative Example 1 65.3 52.3 Comparative Example 2 12.9 10.3 Comparative Example 3 44.5 35.6

[0054] As can be seen from Table 1, the adsorption amount and adsorption rate of glyphosate in the embodiment are significantly better than those in the control example. This may be because control example 1 and control example 2 respectively use biochar and chitosan as adsorbents. Biochar has a rich pore structure and a large specific surface area, and can remove glyphosate by physical adsorption and chemical adsorption. However, glyphosate is negatively charged within a certain pH range, and the surface of biochar may also be negatively charged. There is an electrostatic repulsion between the two, which will hinder the adsorption process. This results in the treatment efficiency of high-concentration glyphosate mother liquor being low when biochar is used alone, making it difficult to completely remove glyphosate. Chitosan contains a large number of active groups such as amino and hydroxyl groups, which can undergo electrostatic interactions and hydrogen bonds with glyphosate, thereby achieving effective adsorption of glyphosate. However, chitosan has poor solubility in water, which limits its direct application in aqueous solutions, thereby affecting the adsorption effect. In the embodiment, chitosan is modified, and the addition of quaternary ammonium salt groups not only improves water solubility but also achieves cationization, thereby enhancing the adsorption effect. Metal salt modification enables glyphosate to be able to bind to metal ions (Mn) by coordination. + ) form chemical bonds with the modified chitosan, resulting in a thermodynamically stable complex. The modified chitosan further enhances the adsorption effect by forming a stable complex with the modified chitosan. Aerogels have higher porosity and a larger specific surface area. These properties enable them to provide more adsorption sites, significantly improving their adsorption capacity for pollutants.

[0055] The alkaline properties of glyphosate come from the electrons of nitrogen (N) and oxygen (O) atoms in its composition, which can coordinate with metal ions (M + ) form chemical bonds, thereby forming thermodynamically stable complexes, but the stability of these complexes is not the same, but is related to the metal ions themselves. This may be the reason for the different adsorption effects in the treatment processes between the examples. The higher the charge density of the metal ion, the stronger its ability to bind to the electron pairs of nitrogen and oxygen atoms in glyphosate. Metal ions with high charge density usually have higher hydration energy and can more effectively bind to polar groups in glyphosate, thereby forming more stable complexes. And Fe 3+The charge density of Fe is higher, so the complexes they form with glyphosate are more stable. The coordination number and coordination stability of the metal ion also affect the stability of the complex. 3+ and Cu 2+ The ion has a high coordination number and can form multiple coordination bonds with the nitrogen and oxygen atoms in glyphosate, thereby enhancing the stability of the complex. 3+ and Cu 2 + It has strong coordination chemical properties and can form stable coordination bonds with the electron pairs in glyphosate. 2+ The chemical properties of chitosan are relatively mild, and the complex formed with glyphosate is relatively unstable. Therefore, the chitosan aerogel modified with ferric chloride in Example 1 has a better adsorption effect on glyphosate, with a higher adsorption rate and adsorption amount.

[0056] Compared with Example 1, Examples 4 and 5 have different amounts of adsorbent. It can be seen that when the amount of adsorbent is small, the adsorption effect will be affected, and when the amount continues to increase, the adsorption effect is not significantly improved. This may be because the adsorption effect in Example 1 has reached saturation. Considering the cost, the solution in Example 1 is the best.

[0057] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A process for environmentally friendly treatment of glyphosate production mother liquor, characterized in that: The steps include: S1. Mix chitosan with sodium hydroxide aqueous solution and isopropyl alcohol, heat and stir for 2-4 hours, then add (3-chloropropyl)-trimethylammonium chloride aqueous solution, continue stirring for 4-8 hours after heating, add dilute hydrochloric acid to adjust the pH to neutral, filter, wash, dry and use in the next step; The mass ratio of chitosan to sodium hydroxide solution, isopropyl alcohol and (3-chloropropyl)-trimethylammonium chloride solution is 1:2-5:5-10:5-8; S2. Add the product of the previous step to water, mix well, and heat with stirring for 2 to 4 hours. Add metal salt solution and epichlorohydrin, continue stirring for 2 to 4 hours, let gel stand, filter, wash, and freeze-dry to obtain modified chitosan aerogel; the mass ratio of the product of the previous step to the metal salt solution and epichlorohydrin is 1:2 to 10:0.02 to 0.1; S3, adjusting the pH of the glyphosate production mother liquor with dilute hydrochloric acid, filtering, adding the modified chitosan aerogel and biochar as an adsorbent to the filtrate, shaking and adsorbing, filtering, and detecting the content of various substances in the filtrate, and discharging after meeting the standards; The mass ratio of modified chitosan aerogel to biochar is 1 to 5:1; The pH is adjusted to a range of 2 to 3; The metal salt is one of ferric chloride, copper chloride or magnesium chloride.

2. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The temperature range of the heating and stirring is 40-50°C.

3. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The temperature range of the heating is 70-80°C.

4. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The solid-liquid ratio of the adsorbent to the filtrate is 50-100 g / L.

5. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The temperature of the oscillating adsorption is 40-50° C., and the time is 10-30 hours.

6. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The method comprises the following steps, in parts by weight: S1. Mix 1 part of chitosan with 3 parts of 40 wt% sodium hydroxide aqueous solution and 8 parts of isopropanol, heat to 50°C and stir for 3 hours, then add 8 parts of 10 wt% (3-chloropropyl)-trimethylammonium chloride aqueous solution, heat to 75°C and continue stirring for 6 hours, add 1 mol / L dilute hydrochloric acid to adjust the pH to neutral, filter, wash, and dry the obtained product for the next step; S2. Add 1 part of the product from the previous step to 50 parts of water, mix well, heat to 50° C. and stir for 3 hours, add 5 parts of 20 wt% ferric chloride aqueous solution and 0.05 parts of epichlorohydrin, continue stirring for 3 hours, let stand to gel, filter, wash and freeze-dry to obtain modified chitosan aerogel; S3. Adjust the pH of the glyphosate production mother liquor to 2 with 1 mol / L dilute hydrochloric acid, filter, and obtain a filtrate; mix the modified chitosan aerogel and biochar in a mass ratio of 3:1 and add them to the filtrate as an adsorbent, with a solid-liquid ratio of the adsorbent to the filtrate of 80 g / L; adsorb at 45°C under oscillation for 24 hours, filter, and detect the content of various substances in the filtrate. Discharge after meeting the standards.