Multistage membrane treatment method of glyphosate mother liquor

Abstract

The invention discloses a multistage membrane treatment method of glyphosate mother liquor. The method comprises the following steps: (1) adjusting the pH value of the glyphosate mother liquor to recover triethylamine; (2) carrying out wet catalytic oxidation on the glyphosate salt-containing waste liquid to obtain a concentrated solution and a permeate; (3) filtering the concentrated solution and then conveying the concentrated solution into a first-stage membrane for separation to obtain first-stage trapped fluid and first-stage permeated fluid; (4) conveying the first-stage trapped fluid into a second-stage membrane for separation to obtain a second-stage trapped fluid and a second-stage permeate; (5) conveying the second-stage trapped fluid into a third-stage membrane for separation to obtain third-stage trapped fluid and third-stage permeate; (6) mixing the permeate liquid with the first-stage permeate liquid, the second-stage permeate liquid and the third-stage permeate liquid to obtain a sodium chloride solution; and (7) mixing the third-stage trapped fluid, the second-stage trapped fluid and the first-stage trapped fluid, cooling, crystallizing, separating to obtain a glyphosate technical product and filtrate, mixing the filtrate with the concentrated solution, and continuously and circularly carrying out multi-stage membrane treatment.

Description

Technical Field

[0001] The invention relates to the technical field of salt-containing wastewater treatment, and in particular to a multi-stage membrane treatment method for glyphosate mother liquor. Background Art

[0002] There are four main production processes for glyphosate, namely the chloroacetic acid method, the iminodiacetic acid method, the dialkyl phosphite method and the trialkyl phosphite method. Among them, the dialkyl phosphite method uses polyformaldehyde, glycine, and dialkyl phosphite as raw materials, triethylamine as a catalyst, and obtains glyphosate through addition, condensation, and acidolysis. This process is relatively simple, with relatively less wastewater, high yield, low cost, and good product quality. Therefore, this process method is mainly used in China. However, one of the biggest problems with this process method is the treatment of the mother liquor after acidolysis, crystallization, and filtration to obtain the glyphosate original drug. The mother liquor after glyphosate crystallization is a strongly acidic liquid containing a large amount of triethylamine, hydrochloric acid, and glyphosate. Triethylamine is an important catalyst, and it is expensive and needs to be recycled. The currently commonly used method for treating glyphosate mother liquor is to neutralize it with liquid alkali to a pH greater than 10, and triethylamine is separated from the solution as an oil phase, and a glyphosate mother liquor is produced after separation, wherein the glyphosate mother liquor also contains 1-3% glyphosate, about 1% triethylamine, and more than 10% sodium chloride; currently, the prior art method for treating glyphosate mother liquor is to re-concentrate it, increase the concentration of glyphosate to about 5%, separate out sodium chloride crystals, add glyphosate technical to adjust the glyphosate concentration to 7% or 10%, and sell it as a 7% or 10% glyphosate aqueous solution. Since the 7% or 10% glyphosate aqueous solution contains almost saturated sodium chloride, long-term use will cause soil salinization and hardening, causing adverse effects on the environment. Furthermore, the neutralization treatment method of the mother liquor after glyphosate crystallization only recovers the triethylamine therein, while the raw hydrochloric acid used for acidic hydrolysis cannot be recycled but becomes sodium chloride or other chloride pollutants, which not only produces solid waste, but also causes the 7% or 10% glyphosate aqueous solution to contain a large amount of sodium chloride or other chlorides, which harms the environment. More importantly, neutralizing this part of hydrochloric acid also consumes additional liquid alkali, which increases production costs. Summary of the invention

[0003] In view of this, the present invention provides a multi-stage membrane treatment method for glyphosate mother liquor to solve the above-mentioned problems.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] A multi-stage membrane treatment method for glyphosate mother liquor comprises the following steps:

[0006] (1) taking a glyphosate mother liquor, adding a sodium hydroxide solution, adjusting the pH value of the glyphosate mother liquor, stirring evenly and then standing to separate the layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid;

[0007] (2) transporting the glyphosate-containing salt waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation to obtain a concentrated liquid and a permeate;

[0008] (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate and a primary permeate;

[0009] (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate and a secondary permeate;

[0010] (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate and a tertiary permeate;

[0011] (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution;

[0012] (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate and the concentrated solution in step (2) are mixed and then continuously circulated for multi-stage membrane treatment.

[0013] Furthermore, the mass fraction of the sodium hydroxide solution in step (1) is 30-90%

[0014] Furthermore, in step (1), the pH value of the glyphosate mother solution is adjusted to 9-11.

[0015] Furthermore, in step (2), the mass ratio of the glyphosate-containing saline waste liquid to oxygen is 40:3-5.

[0016] Furthermore, the conditions for wet catalytic oxidation in step (2) are a temperature of 200 to 280° C. and a pressure of 2 to 8 MPa.

[0017] Furthermore, in step (3), the concentrated liquid is filtered using at least one of a filter press, a bag filter, a precision filter, a microporous filter, and an ultrafiltration, and the contamination index of the concentrated liquid is ≤5.

[0018] Furthermore, the molecular weight cutoffs of the primary membrane, the secondary membrane and the tertiary membrane are all nanofiltration membranes with a molecular weight cutoff of 80 to 160D, and the pore size of the primary membrane is greater than the pore size of the secondary membrane and greater than the pore size of the tertiary membrane.

[0019] Furthermore, the glyphosate concentration of the primary retentate is 2% to 6%, the glyphosate concentration of the secondary retentate is 5% to 9%, and the glyphosate concentration of the tertiary retentate is 8% to 12%.

[0020] The beneficial effects of the present invention are:

[0021] The invention first recovers triethylamine in a glyphosate mother liquor, and then treats the glyphosate mother liquor by wet catalytic oxidation. The wet catalytic oxidation process can directly remove part of NaCl in the glyphosate mother liquor, thereby reducing the content of NaCl in the glyphosate mother liquor, alleviating the trend of concentration polarization on both sides during membrane separation, reducing the attenuation of slow membrane flux, and thus improving the service life of the membrane. Meanwhile, a nanofiltration membrane with a cutoff molecular weight of 80-160D is selected, and small-molecule NaCl (relative molecular weight: 58.44) can pass through the membrane to a permeate, while macromolecular substances such as glyphosate (relative molecular weight: 263.08) and glyphosate (relative molecular weight: 169.07) cannot pass through the membrane due to their large molecular weight, so they stay in the retentate, thereby realizing the collection of NaCl in the glyphosate mother liquor. Meanwhile, the retentate can be used to extract glyphosate after being cooled and crystallized. The method for treating the glyphosate mother liquor has the advantages of high desalination efficiency, sustainable production, cost saving, and the like, and has the potential for industrial application. DETAILED DESCRIPTION

[0022] The present invention provides a multi-stage membrane treatment method for glyphosate mother liquor, comprising the following steps:

[0023] (1) taking a glyphosate mother liquor, adding a sodium hydroxide solution having a mass fraction of 30 to 90%, adjusting the pH value of the glyphosate mother liquor to 9 to 11, stirring evenly and then standing to separate the layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid;

[0024] (2) transporting the glyphosate-containing saline waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation, wherein the mass ratio of the glyphosate-containing saline waste liquid to oxygen is 40:3-5, and the conditions for the wet catalytic oxidation are a temperature of 200-280° C. and a pressure of 2-8 MPa, to obtain a concentrated solution and a permeate;

[0025] (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate and a primary permeate having a glyphosate concentration of 2% to 6%;

[0026] (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate and a secondary permeate having a glyphosate concentration of 5% to 9%;

[0027] (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate and a tertiary permeate having a glyphosate concentration of 8% to 12%;

[0028] (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution;

[0029] (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate is mixed with the concentrated solution in step (2) and then continuously circulated for multi-stage membrane treatment.

[0030] Wherein, the concentrated liquid is filtered in step (3) by at least one of a filter press, a bag filter, a precision filter, a microporous filter, and an ultrafiltration, and the contamination index of the concentrated liquid is ≤5; the molecular weight cutoffs of the primary membrane, the secondary membrane, and the tertiary membrane are all nanofiltration membranes with a molecular weight cutoff of 80 to 160D, and the pore size of the primary membrane is greater than the pore size of the secondary membrane and greater than the pore size of the tertiary membrane.

[0031] Example 1

[0032] In this embodiment, the molecular weight cutoff of the primary membrane is 80D, the molecular weight cutoff of the secondary membrane is 100D, and the molecular weight cutoff of the tertiary membrane is 120D.

[0033] A multi-stage membrane treatment method for glyphosate mother liquor in this embodiment comprises the following steps:

[0034] (1) taking a glyphosate mother liquor, adding a 30% by mass sodium hydroxide solution, adjusting the pH value of the glyphosate mother liquor to 9, stirring evenly and then standing to separate the layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid;

[0035] (2) transporting the glyphosate-containing saline waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation, wherein the mass ratio of the glyphosate-containing saline waste liquid to oxygen is 40:3, and the conditions for the wet catalytic oxidation are a temperature of 200° C. and a pressure of 2 MPa, to obtain a concentrated solution and a permeate;

[0036] (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate solution and a primary permeate solution having a glyphosate concentration of 2%;

[0037] (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate with a glyphosate concentration of 5% and a secondary permeate;

[0038] (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate with a glyphosate concentration of 8% and a tertiary permeate;

[0039] (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution;

[0040] (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate is mixed with the concentrated solution in step (2) and then continuously circulated for multi-stage membrane treatment.

[0041] Example 2

[0042] In this embodiment, the molecular weight cutoff of the primary membrane is 100D, the molecular weight cutoff of the secondary membrane is 120D, and the molecular weight cutoff of the tertiary membrane is 140D.

[0043] A multi-stage membrane treatment method for glyphosate mother liquor in this embodiment comprises the following steps:

[0044] (1) taking a glyphosate mother liquor, adding a sodium hydroxide solution having a mass fraction of 60%, adjusting the pH value of the glyphosate mother liquor to 10, stirring evenly and then standing to separate the layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid;

[0045] (2) transporting the glyphosate-containing saline waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation, wherein the mass ratio of the glyphosate-containing saline waste liquid to oxygen is 40:4, and the conditions for the wet catalytic oxidation are a temperature of 240° C. and a pressure of 5 MPa, to obtain a concentrated solution and a permeate;

[0046] (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate solution and a primary permeate solution having a glyphosate concentration of 4%;

[0047] (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate having a glyphosate concentration of 7% and a secondary permeate;

[0048] (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate with a glyphosate concentration of 10% and a tertiary permeate;

[0049] (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution;

[0050] (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate is mixed with the concentrated solution in step (2) and then continuously circulated for multi-stage membrane treatment.

[0051] Example 3

[0052] In this embodiment, the molecular weight cutoff of the primary membrane is 120D, the molecular weight cutoff of the secondary membrane is 140D, and the molecular weight cutoff of the tertiary membrane is 160D.

[0053] A multi-stage membrane treatment method for glyphosate mother liquor in this embodiment comprises the following steps:

[0054] (1) taking a glyphosate mother liquor, adding a 90% by mass sodium hydroxide solution, adjusting the pH value of the glyphosate mother liquor to 9-11, stirring evenly and then standing to separate layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid;

[0055] (2) transporting the glyphosate-containing saline waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation, wherein the mass ratio of the glyphosate-containing saline waste liquid to oxygen is 40:3-5, and the conditions for the wet catalytic oxidation are a temperature of 280° C. and a pressure of MPa, to obtain a concentrated solution and a permeate;

[0056] (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate solution with a glyphosate concentration of 6% and a primary permeate solution;

[0057] (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate having a glyphosate concentration of 9% and a secondary permeate;

[0058] (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate having a glyphosate concentration of 12% and a tertiary permeate;

[0059] (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution;

[0060] (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate is mixed with the concentrated solution in step (2) and then continuously circulated for multi-stage membrane treatment.

[0061] The invention first recovers triethylamine in a glyphosate mother liquor, and then treats the glyphosate mother liquor by wet catalytic oxidation. The wet catalytic oxidation process can directly remove part of NaCl in the glyphosate mother liquor, thereby reducing the content of NaCl in the glyphosate mother liquor, alleviating the trend of concentration polarization on both sides during membrane separation, reducing the attenuation of slow membrane flux, and thus improving the service life of the membrane. Meanwhile, a nanofiltration membrane with a cutoff molecular weight of 80-160D is selected, and small-molecule NaCl (relative molecular weight: 58.44) can pass through the membrane to a permeate, while macromolecular substances such as glyphosate (relative molecular weight: 263.08) and glyphosate (relative molecular weight: 169.07) cannot pass through the membrane due to their large molecular weight, so they stay in the retentate, thereby realizing the collection of NaCl in the glyphosate mother liquor. Meanwhile, the retentate can be used to extract glyphosate after being cooled and crystallized. The method for treating the glyphosate mother liquor has the advantages of high desalination efficiency, sustainable production, cost saving, and the like, and has the potential for industrial application.

[0062] With the above-mentioned ideal embodiment of the present invention as inspiration, through the above-mentioned description content, relevant staff can make various changes and modifications without departing from the scope of the present invention. The technical scope of this invention is not limited to the contents in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A multi-stage membrane treatment method for glyphosate mother liquor, characterized in that: The following steps are involved: (1) taking a glyphosate mother liquor, adding a sodium hydroxide solution, adjusting the pH value of the glyphosate mother liquor, stirring evenly and then standing to separate the layers, taking the upper oil phase and purifying it to obtain the catalyst triethylamine, and the lower layer is the glyphosate salt-containing waste liquid; (2) transporting the glyphosate-containing salt waste liquid in step (1) to an oxidation reactor and introducing oxygen for wet catalytic oxidation to obtain a concentrated liquid and a permeate; (3) filtering the concentrated solution in step (2) and transferring it to a primary membrane for separation to obtain a primary retentate and a primary permeate; (4) transporting the primary retentate in step (3) to a secondary membrane for separation to obtain a secondary retentate and a secondary permeate; (5) transporting the secondary retentate in step (4) to a tertiary membrane for separation to obtain a tertiary retentate and a tertiary permeate; (6) mixing the permeate in step (2) with the primary permeate in step (3), the secondary permeate in step (4), and the tertiary permeate in step (5) to obtain a sodium chloride solution; (7) The third-stage retentate in step (5), the second-stage retentate in step (4) and the first-stage retentate in step (3) are mixed and then cooled and crystallized to separate the glyphosate technical product and the filtrate, and the filtrate is mixed with the concentrated solution in step (2) and then continuously circulated for multi-stage membrane treatment.

2. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution in step (1) is 30-90%.

3. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: In the step (1), the pH value of the glyphosate mother solution is adjusted to 9-11.

4. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: In the step (2), the mass ratio of glyphosate salt-containing waste liquid to oxygen is 40:3-5.

5. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: The conditions for wet catalytic oxidation in step (2) are a temperature of 200-280° C. and a pressure of 2-8 MPa.

6. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: In the step (3), the concentrated liquid is filtered using at least one of a filter press, a bag filter, a precision filter, a microporous filter, and an ultrafiltration, and the contamination index of the concentrated liquid is ≤5.

7. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: The molecular weight cutoffs of the primary membrane, the secondary membrane and the tertiary membrane are all nanofiltration membranes with a molecular weight cutoff of 80 to 160D, and the pore size of the primary membrane is greater than the pore size of the secondary membrane and greater than the pore size of the tertiary membrane.

8. The multi-stage membrane treatment method for glyphosate mother liquor according to claim 1, characterized in that: The glyphosate concentration of the first-level intercepted liquid is 2% to 6%, the glyphosate concentration of the second-level intercepted liquid is 5% to 9%, and the glyphosate concentration of the third-level intercepted liquid is 8% to 12%.