Environment-friendly treatment process for glyphosate production mother liquor

Abstract

The invention discloses an environment-friendly treatment process for glyphosate production mother liquor. According to the treatment process, chitosan is modified to obtain modified chitosan aerogel, the modified chitosan aerogel is mixed with biochar to serve as an adsorbent, and glyphosate production mother liquor is treated. Compared with the prior art, the treatment process disclosed by the invention is high in adsorption rate, good in adsorption effect, simple to operate, low in cost and convenient to operate. The modified chitosan aerogel has higher porosity and large specific surface area, and can form a complex with glyphosate, so that the adsorption effect is improved, and the treatment effect is better.

Description

Technical Field

[0001] The 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. It has a complex composition and usually contains 0.5%-4% glyphosate, 15%-20% salts (mainly sodium chloride, but also disodium hydrogen phosphate, sodium pyrophosphate, etc.), as well as formaldehyde, formic acid, glyphosate, diglyphosate and other organic impurities that are difficult to degrade. It also contains a certain amount of pollutants such as COD (chemical oxygen demand) and total phosphorus. If it is discharged directly without effective treatment, it will bring many hazards, such as polluting water bodies, causing the COD, total phosphorus and other indicators of the receiving water bodies to seriously exceed the standard, leading to eutrophication of water bodies and destroying the water ecological balance; entering the soil will change the physical and chemical properties of the soil, affect the structure and function of the soil microbial community, and lead to a decrease in soil fertility; it may also cause potential harm to the human nervous system, endocrine system, etc. through enrichment and transmission in the food chain, and has the risk of carcinogenicity and teratogenicity.

[0003] At present, the methods for treating glyphosate in wastewater include incineration and advanced oxidation, membrane separation, biochemical method, adsorption method, etc. The mother liquor concentrate is incinerated at high temperature, and phosphorus is converted 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 is the oxidation of organic matter under high temperature and high pressure, with a phosphorus recovery rate of 70%-80%. It is necessary to combine membrane technology for pre-desalting to improve product quality. The inorganic salts (such as sodium chloride) and organic matter in the mother liquor are separated by membrane technologies such as nanofiltration and reverse osmosis. The salt content of the mother liquor of the glycine method can be reduced to 1%, and the dilute liquid of the mother liquor of the IDA method can be recycled for the synthesis process. This method saves energy and improves the concentration efficiency, but the separated dilute liquid still needs to be evaporated and treated, which is costly. The biochemical method uses the biochemical action in microorganisms to decompose toxic and harmful substances in wastewater and solid waste, but the microbial culture time is long, the pretreatment requirements for glyphosate wastewater are high, and the process time is long.

[0004] CN1648131A introduces a treatment process for the mother liquor obtained by synthesizing glyphosate by the glycine method. The treatment process is operated according to the following steps: first, ammonia is introduced into the glyphosate mother liquor to adjust the pH value of the mother liquor to 7-10, and then a static stratification treatment is performed, and the triethylamine in the upper layer is recovered after completion. Then, the lower mother liquor is subjected to a vacuum distillation operation, cooled after distillation, and then the ammonium chloride crystals therein are removed by filtering, and finally a concentrated glyphosate ammonium salt is obtained. This glyphosate mother liquor treatment process has significant advantages. It not only has low production costs, but also can effectively save energy consumption, protect the environment, and improve the efficacy of the obtained aqueous solution. If the deacidification operation is not performed after the hydrolysis and desolvation step, but a certain amount of alkali is directly added to adjust the pH value, so that the solubility of glyphosate is reduced to a minimum, so that it is precipitated from the reaction solution as much as possible, then the yield of glyphosate original drug can be improved. Moreover, this method can also improve equipment utilization and reduce energy consumption.

[0005] CN119219249A discloses a multi-stage membrane treatment method for glyphosate mother liquor, which comprises the following specific steps: Step 1, adjusting the pH value 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 finally obtain a concentrated solution and a permeate. Step 3, filtering the concentrated solution and transporting it to the primary membrane for separation operation to obtain a primary retentate and a primary permeate. Step 4, transporting the primary retentate to the secondary membrane for further separation to obtain a secondary retentate and a secondary permeate. Step 5, transporting the secondary retentate to the tertiary membrane for separation to obtain a tertiary retentate and a tertiary permeate. Step 6, mixing the permeate with the primary permeate, the secondary permeate and the tertiary permeate to finally obtain a sodium chloride solution. Step 7, mixing the tertiary retentate, the secondary retentate and the primary retentate together for cooling and crystallization, and then separating to obtain the glyphosate technical product and the filtrate. The filtrate is mixed with the concentrate and then continues to circulate through the multi-stage membrane treatment.

[0006] The membrane separation method uses inorganic materials or polymer materials with selective permeability as the separation layer. However, glyphosate wastewater has the characteristics of high salt content, high organic matter content and phosphate. When treated by membrane separation, these characteristics easily lead to clogging of membrane pores. There are also certain limitations for the biological method for glyphosate wastewater treatment. Due to the high total phosphorus concentration in glyphosate wastewater, the effect of biological method for treating such wastewater is not ideal. In contrast, the adsorption method has received widespread attention due to its advantages such as simple operation, low cost, easy operation and high removal rate of 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 can treat glyphosate production wastewater mainly because it utilizes the porous structure and large specific surface area of ​​the adsorbent, and adsorbs glyphosate molecules on the adsorbent surface through intermolecular forces (van der Waals forces). This adsorption process does not involve chemical reactions, the structural changes of the adsorbate molecules are very small, and the adsorption energy is low. The adsorbed substances can be easily detached from the adsorbent surface under appropriate conditions (such as increasing the temperature). However, there are some defects in the treatment of glyphosate wastewater by physical adsorption. First, the adsorption capacity of the adsorbent is limited, and it is difficult to meet the treatment requirements of high-concentration wastewater. Secondly, the selectivity of the adsorbent 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, wherein biochar and modified chitosan aerogel are mixed to obtain an adsorbent, which is applied to the treatment of glyphosate production mother liquor. Biochar has a highly developed pore structure and a large specific surface area, and can effectively adsorb organic pollutants such as glyphosate. In addition, the surface of biochar is rich in a large number of oxygen-containing functional groups (such as hydroxyl groups, carboxyl groups, etc.), which can chemically adsorb with glyphosate molecules to further enhance 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 to achieve the adsorption effect. By modifying it and cross-linking it with (3-chloropropyl)-trimethylammonium chloride and metal ions, 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 + ) to form a thermodynamically stable complex. The modified chitosan can form a stable complex with it, thereby further improving the adsorption effect. The treatment of glyphosate production mother liquor by adsorbent can effectively remove harmful substances in wastewater. The method is simple and environmentally friendly, the adsorbent cost is low, and the adsorption rate is high.

[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 isopropanol, 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, adding the product of the previous step into water, mixing evenly, heating and stirring for 2 to 4 hours, adding metal salt solution and epichlorohydrin, continuing to stir for 2 to 4 hours, letting the gel stand, filtering, washing and freeze-drying to obtain modified chitosan aerogel;

[0013] S3. Adjust the pH of the mother liquor produced by glyphosate with dilute hydrochloric acid, filter it, mix the modified chitosan aerogel with biochar and add it to the filtrate as an adsorbent, oscillate and adsorb, filter it, and then detect the content of each substance in the filtrate. Discharge it after meeting the standards.

[0014] Furthermore, the mass ratio of the chitosan to the sodium hydroxide solution, isopropanol 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 the biochar is 1 to 5:1.

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

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

[0021] Furthermore, the oscillating adsorption is carried out at a temperature of 40 to 50° C. and for a time of 10 to 30 hours.

[0022] Furthermore, the metal salt is one of ferric chloride, cupric 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 the adsorbent to the treatment of glyphosate production mother liquor. The surface of biochar is rich in a large number of 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 to form thermodynamically stable complexes. The modified chitosan can form stable complexes with it, thereby further improving the adsorption effect. 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 40wt% sodium hydroxide aqueous solution and 8 parts of isopropanol, heat to 50°C and stir for 3h, then add 8 parts of 10wt% (3-chloropropyl)-trimethylammonium chloride aqueous solution, heat to 75°C and continue stirring for 6h, add 1mol / L dilute hydrochloric acid to adjust the pH to neutral, filter, wash and dry the obtained product for the next step;

[0031] S2, adding 1 part of the product of the previous step to 50 parts of water, mixing evenly, heating to 50°C and stirring for 3 hours, adding 5 parts of 20wt% ferric chloride aqueous solution and 0.05 parts of epichlorohydrin, continuing to stir for 3 hours, letting the gel stand, filtering, washing and freeze-drying to obtain modified chitosan aerogel;

[0032] S3. Adjust the pH value of the mother liquor produced by glyphosate 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, the solid-liquid ratio of the adsorbent to the filtrate is 80 g / L, oscillate and adsorb at 45°C for 24 hours, filter and detect the content of each substance in the filtrate, and discharge it after meeting the standards.

[0033] Example 2

[0034] The method is substantially 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 substantially 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] It is basically the same as Example 1, the only difference being that the solid-to-liquid ratio of the adsorbent to the filtrate is 70 g / L.

[0039] Example 5

[0040] It is basically the same as Example 1, the only difference being that the solid-to-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 value 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 80 g / L to the filtrate. After oscillation at 45°C for 24 hours of adsorption, the content of each substance in the filtrate was detected after filtration and the substance was 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 value of the mother liquor produced by glyphosate 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 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.

[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 value 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 the adsorption amount = (initial glyphosate concentration - glyphosate concentration after adsorption) × solution volume / adsorbent mass, and the 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 protocol Adsorption amount / 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 the control examples 1 and 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 that when biochar is used alone, the treatment efficiency of high-concentration glyphosate mother liquor may be low, and it is difficult to completely remove glyphosate. Chitosan contains a large number of active groups such as amino and hydroxyl groups, which can interact electrostatically and hydrogen bond with glyphosate, thereby achieving effective adsorption of glyphosate. However, the solubility of chitosan in water is poor, 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 the water solubility but also achieves cationization, thereby enhancing the adsorption effect. Metal salt modification enables glyphosate to be able to bind to metal ions (M + ) form chemical bonds to obtain thermodynamically stable complexes. The modified chitosan can form stable complexes with it, thus further improving the adsorption effect. Aerogels have higher porosity and larger specific surface area. These characteristics enable aerogels to provide more adsorption sites, thereby significantly improving the adsorption capacity of pollutants.

[0055] The alkalinity of glyphosate comes from the electrons of nitrogen (N) and oxygen (O) atoms in its composition, which can coordinate with metal ions (M + ) form chemical bonds to form 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 embodiments. 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 to form more stable complexes. 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 will 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, and the adsorption rate and adsorption amount are both high.

[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 preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined 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 isopropanol, 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; S2, adding the product of the previous step into water, mixing evenly, heating and stirring for 2 to 4 hours, adding metal salt solution and epichlorohydrin, continuing to stir for 2 to 4 hours, letting the gel stand, filtering, washing and freeze-drying to obtain modified chitosan aerogel; S3. Adjust the pH of the mother liquor produced by glyphosate with dilute hydrochloric acid, filter it, mix the modified chitosan aerogel with biochar and add it to the filtrate as an adsorbent, oscillate and adsorb, filter it, and then detect the content of each substance in the filtrate. Discharge it after meeting the standards.

2. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The mass ratio of the chitosan to the sodium hydroxide solution, isopropanol and (3-chloropropyl)-trimethylammonium chloride solution is 1:2-5:5-10:5-8.

3. 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.

4. 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.

5. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: 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.

6. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The mass ratio of the modified chitosan aerogel to the biochar is 1 to 5:

1.

7. 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.

8. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The pH value is adjusted to be in the range of 2 to 3.

9. 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.

10. The environmentally friendly treatment process for glyphosate production mother liquor according to claim 1, characterized in that: The metal salt is one of ferric chloride, copper chloride or magnesium chloride.