A method for recycling and recovering glyphosate mother liquor

Abstract

The present application relates to the technical field of resource recycling, and specifically discloses a resource recycling treatment method for glyphosate mother liquor. The method comprises the following steps: (1) adding an oxidizing agent to the glyphosate mother liquor and adjusting the pH to obtain a pretreated mother liquor; (2) performing constant-current electrolysis on the pretreated mother liquor using a high hydrogen evolution overpotential electrode to obtain a conversion liquid; (3) adjusting the pH of the conversion liquid, adding nano polydopamine biomimetic affinity seed crystals, and performing temperature reduction and crystal growth to separate glyphosate crystals and a crystallization mother liquor; (4) performing adsorption pretreatment and dilution on the crystallization mother liquor, and then recovering hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalted fresh water under the action of a direct current electric field; and (5) heating the hydrochloric acid / phosphoric acid mixed acid solution to the azeotropic point, allowing hydrogen chloride gas to escape, absorbing the hydrogen chloride gas with water to obtain a hydrochloric acid solution, heating and concentrating the residue at the bottom of the kettle to collect a phosphoric acid solution. The method can effectively recycle the glyphosate mother liquor without generating secondary pollutants and waste streams.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, and more specifically, to a method for the resource-based recycling and treatment of glyphosate mother liquor. Background Technology

[0002] Glyphosate is the world's most produced and widely used herbicide. In its mainstream production processes—the iminodiacetic acid (IDA) process or the glycine-dimethyl phosphite process—a large amount of mother liquor wastewater is generated after glyphosate crystallization and separation. This mother liquor has an extremely complex composition and is a typical example of high-salt, high-organic-content, and difficult-to-biodegrade industrial wastewater. Its resource recovery and harmless treatment have always been major challenges restricting the sustainable development of the industry.

[0003] Taking the IDA process as an example, glyphosate mother liquor contains high concentrations of sodium chloride (typically ≥15%), residual glyphosate (0.5%–2.0%), glyphosate (1%–5%), and various organic or phosphorus-containing impurities such as formaldehyde, formic acid, hydroxymethylphosphonic acid, and phosphorous acid. Because the chemical structure of glyphosate is highly similar to that of glyphosate, differing only by the addition of a phosphonomethyl group, separation of the two is extremely difficult, and traditional separation methods struggle to achieve high-value recovery.

[0004] Currently, the main industrial methods for treating this type of mother liquor include evaporation-concentration-incineration / landfill, chemical oxidation / precipitation, membrane separation / adsorption-glyphosate recovery, and bipolar membrane electrodialysis. In recent years, bipolar membrane technology has been attempted for glyphosate mother liquor treatment, aiming to directly convert sodium chloride into hydrochloric acid and caustic soda. However, practice has shown that if a large amount of residual organic impurities (especially organophosphorus compounds such as glyphosate) in the mother liquor enters the membrane system without deep removal, it will cause severe membrane fouling, leading to a sharp decline in current efficiency and a significant reduction in membrane life, thus hindering the industrial application of this method for a long time. Existing technologies have failed to comprehensively address the key common problems of sodium chloride recovery, high-value recovery of glyphosate and glyphosate, complete resource utilization of phosphorus, and the absence of secondary pollution throughout the entire process, from the perspectives of atom economy and system integration. In particular, the targeted conversion and value-added utilization of glyphosate, a structural impurity, is almost entirely absent from existing reports, constituting a critical technical challenge that urgently needs to be overcome in this field. Developing an integrated technology that can simultaneously achieve the directional conversion of glyphosate to glyphosate, the selective separation of high-purity glyphosate, and the resource-based recovery of all components under mild conditions has significant practical needs and industrial value. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for the resource-based recycling and treatment of glyphosate mother liquor.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for the resource recovery and treatment of glyphosate mother liquor includes the following steps:

[0008] (1) Oxidative pretreatment: An oxidant was added to the glyphosate mother liquor, and the reaction was carried out under heating conditions. Then the system was cooled and the pH of the system was adjusted to 1.0-2.5 to obtain the pretreated mother liquor.

[0009] (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane, and a conductive medium without chloride ions is injected into the anode chamber of the electrolytic cell. Constant current electrolysis is performed at the cathode using a high hydrogen evolution overpotential electrode to reduce glyphosate in the mother liquor to glyphosate, thereby obtaining a glyphosate-rich conversion solution.

[0010] (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 2.5-3.0, add nano-polydopamine bionic affinity crystal seeds, and grow crystals by programmed cooling. Then separate high-purity glyphosate crystals and crystallization mother liquor.

[0011] (4) Bipolar membrane electrodialysis resource recovery: After the crystallization mother liquor is pretreated by adsorption and diluted, it is pumped into the bipolar membrane electrodialysis system to recover hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated fresh water under the action of DC electric field;

[0012] (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is then absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated, and collected to obtain phosphoric acid solution.

[0013] Further, the oxidant in step (1) is hydrogen peroxide with a mass fraction of 30-40%, the amount added is 0.3%-0.5% of the mass of glyphosate mother liquor, the heating reaction temperature is 50-70℃, and the reaction time is 0.5-1h.

[0014] Furthermore, in step (2), the anode is a ruthenium-iridium titanium-shaped stable anode, and the cathode is a titanium mesh electrode modified with lead-tin alloy.

[0015] Furthermore, the electrolysis conditions in step (2) are: current density 5-30 mA / cm², electrolyte temperature 25-55℃, and electrolysis time 0.5-4h.

[0016] Furthermore, the cation exchange membrane in step (2) is a monovalent selective cation exchange membrane, and an independently circulating protective chamber is provided between the cathode chamber and the anode chamber. The anolyte in the anode chamber is a sodium sulfate solution.

[0017] Furthermore, the nano-polydopamine biomimetic affinity seed crystals in step (3) have a particle size of 50-200 nm and are added in an amount of 0.1%-0.5% of the glyphosate mother liquor mass.

[0018] Furthermore, in step (3), the programmed cooling rate is 0.1 to 0.5 °C / min, the final temperature is 0 to 8 °C, and the crystal growth time is 1 to 5 h.

[0019] Furthermore, in step (4), the bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane"; the operating parameters are: unit operating voltage 1.5~3.5V, current density 20~80mA / cm², operating temperature 20~35℃, and circulation flow rate of each compartment 0.5~3.0L / min.

[0020] Furthermore, the adsorption pretreatment in step (4) uses macroporous resin adsorption; the dilution is to adjust the conductivity of the mother liquor to 30-60 mS / cm; the total dissolved solids content of the obtained desalinated freshwater is <500 mg / L.

[0021] In summary, this application includes at least the following beneficial effects:

[0022] This invention utilizes electrochemical selective reduction to selectively reduce glyphosate, a notorious impurity in the mother liquor that is extremely similar in properties to glyphosate and is notoriously difficult to treat, by breaking one of its CN bonds at the cathode, directly converting it into the target product, glyphosate. This effectively improves the overall recovery rate of glyphosate, and its atom economy is far superior to the chemical oxidation method that completely mineralizes it.

[0023] This invention applies nano-polydopamine biomimetic affinity seed crystals to the field of glyphosate crystallization. The high-density catechol and amino functional groups on the surface of these seed crystals enable them to specifically recognize and capture glyphosate molecules, similar to a "biological receptor-ligand" relationship, through multi-point hydrogen bonding and electrostatic matching. In complex mother liquor environments with extremely high salinity, this precisely induces glyphosate molecules to oriented, nucleate, and grow on their surface. This mechanism successfully overcomes the common bottleneck of low purity in crystallization products from high-salt organic wastewater, obtaining high-purity glyphosate crystals without the addition of any organic solvents. The process is green and environmentally friendly, effectively improving separation efficiency.

[0024] This invention resolves the logical contradiction of acid and alkali consumption in traditional processes by using in-situ acid production or a protective chamber design in the electrochemical step. Glyphosate products are separated in high-purity form, and the remaining high-salt crystallization mother liquor is treated by bipolar membrane electrodialysis to recover high-value hydrochloric acid and caustic soda in one step. This recovered liquor is then directly returned to the front end of the process for pH adjustment, achieving a closed-loop acid-alkali cycle within the system. Simultaneously, the mixed acid solution is pyrolyzed to obtain pure hydrochloric acid and phosphoric acid products, and the demineralized water can be directly reused. The entire process operates under mild conditions, with both the electrochemical reduction and bipolar membrane electrodialysis processes operating within a low-voltage, high-current-efficiency range. This method significantly reduces energy consumption and carbon emissions, minimizes equipment investment and operational risks, and demonstrates outstanding safety and environmental friendliness. The entire process generates no secondary pollutants or waste streams, perfectly meeting the requirements of green, low-carbon, and sustainable development in modern industry. Detailed Implementation

[0025] It should be noted that, where there is no conflict, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0026] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] This invention provides a method for the resource-based recovery and treatment of glyphosate mother liquor, comprising the following steps:

[0028] (1) Oxidation pretreatment: Add 30-40% hydrogen peroxide by mass to glyphosate mother liquor, the amount added is 0.3%-0.5% of the mass of glyphosate mother liquor, react under heating conditions of 50-70℃ for 0.5-1h, then cool and adjust the pH of the system to 1.0-2.5 to obtain pretreated mother liquor;

[0029] (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane. The cathode is a titanium mesh electrode modified with lead-tin alloy, and the cation exchange membrane is a monovalent selective cation exchange membrane. Sodium sulfate solution is injected into the anode chamber of the electrolytic cell. The anode is a ruthenium-iridium titanium-shaped stable anode. An independent circulating protective chamber is set between the cathode chamber and the anode chamber. Electrolysis is carried out for 0.5 to 4 hours at a current density of 5 to 30 mA / cm² and an electrolyte temperature of 25 to 55°C to reduce glyphosate in the mother liquor to glyphosate and obtain a glyphosate-rich conversion solution.

[0030] (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 2.5-3.0, add polydopamine bionic affinity seed crystals with a particle size of 50-200 nm, the amount added is 0.1%-0.5% of the glyphosate mother liquor mass, cool down to 0-8 °C at a rate of 0.1-0.5 °C / min, and grow crystals for 1-5 h, then separate high-purity glyphosate crystals and crystallization mother liquor;

[0031] (4) Resource recovery by bipolar membrane electrodialysis: The crystallization mother liquor is pretreated by adsorption with macroporous resin and diluted to a conductivity of 30-60 mS / cm. It is then pumped into a bipolar membrane electrodialysis system. The bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane". The operating parameters are: unit operating voltage 1.5-3.5V, current density 20-80mA / cm², operating temperature 20-35℃, and circulation flow rate of each compartment 0.5-3.0L / min. Under the action of DC electric field, hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated fresh water with a total dissolved solids content of <500mg / L are recovered.

[0032] (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated and collected to obtain phosphoric acid solution.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] The resource recovery and treatment method for glyphosate mother liquor in this embodiment includes the following steps:

[0036] (1) Oxidation pretreatment: Add 30% hydrogen peroxide by mass to glyphosate mother liquor, the amount added is 0.3% of the mass of glyphosate mother liquor, react at 50℃ for 0.5h, then cool and adjust the pH of the system to 1.0 to obtain pretreated mother liquor;

[0037] (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane. The cathode is a titanium mesh electrode modified with lead-tin alloy, and the cation exchange membrane is a monovalent selective cation exchange membrane. Sodium sulfate solution is injected into the anode chamber of the electrolytic cell. The anode is a ruthenium-iridium titanium-shaped stable anode. An independent circulating protective chamber is set between the cathode chamber and the anode chamber. Electrolysis is carried out for 0.5 h at a current density of 5 mA / cm² and an electrolyte temperature of 25 °C to reduce glyphosate in the mother liquor to glyphosate and obtain a glyphosate-rich conversion solution.

[0038] (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 2.5, add polydopamine bionic affinity seed crystals with a particle size of 50 nm, the amount added is 0.1% of the glyphosate mother liquor mass, cool down to 0 °C at a rate of 0.1 °C / min, grow crystals for 1 h, and separate high-purity glyphosate crystals and crystallization mother liquor.

[0039] (4) Resource recovery by bipolar membrane electrodialysis: The crystallization mother liquor is pretreated by adsorption with macroporous resin and diluted to a conductivity of 30 mS / cm. It is then pumped into a bipolar membrane electrodialysis system. The bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane". The operating parameters are: unit operating voltage 1.5V, current density 20mA / cm², operating temperature 20℃, and circulation flow rate of each compartment 0.5L / min. Under the action of DC electric field, hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated water with total dissolved solids content <500mg / L are recovered.

[0040] (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is then absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated, and collected to obtain phosphoric acid solution.

[0041] Example 2

[0042] The resource recovery and treatment method for glyphosate mother liquor in this embodiment includes the following steps:

[0043] (1) Oxidation pretreatment: Add 35% hydrogen peroxide to the glyphosate mother liquor, the amount of which is 0.4% of the mass of the glyphosate mother liquor. React at 60℃ for 0.75h, then cool and adjust the pH of the system to 1.5 to obtain the pretreated mother liquor.

[0044] (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane. The cathode is a titanium mesh electrode modified with lead-tin alloy, and the cation exchange membrane is a monovalent selective cation exchange membrane. Sodium sulfate solution is injected into the anode chamber of the electrolytic cell. The anode is a ruthenium-iridium titanium-shaped stable anode. An independent circulating protective chamber is set between the cathode chamber and the anode chamber. Electrolysis is carried out for 2 hours at a current density of 20 mA / cm² and an electrolyte temperature of 40°C to reduce the glyphosate in the mother liquor to glyphosate and obtain a glyphosate-rich conversion solution.

[0045] (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 2.8, add polydopamine bionic affinity seed crystals with a particle size of 100 nm, the amount added is 0.3% of the glyphosate mother liquor mass, cool down to 4 °C at a rate of 0.3 °C / min, grow crystals for 3 h, and separate high-purity glyphosate crystals and crystallization mother liquor.

[0046] (4) Resource recovery by bipolar membrane electrodialysis: The crystallization mother liquor is pretreated by adsorption with macroporous resin and diluted to a conductivity of 45 mS / cm. It is then pumped into a bipolar membrane electrodialysis system. The bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane". The operating parameters are: unit operating voltage 2V, current density 50mA / cm², operating temperature 27℃, and circulation flow rate of each compartment 2L / min. Under the action of DC electric field, hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated fresh water with a total dissolved solids content of <500mg / L are recovered.

[0047] (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is then absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated, and collected to obtain phosphoric acid solution.

[0048] Example 3

[0049] The resource recovery and treatment method for glyphosate mother liquor in this embodiment includes the following steps:

[0050] (1) Oxidation pretreatment: Add 40% hydrogen peroxide by mass to glyphosate mother liquor, the amount added is 0.5% of the mass of glyphosate mother liquor, react at 70℃ for 1h, then cool and adjust the pH of the system to 2.5 to obtain pretreated mother liquor;

[0051] (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane. The cathode is a titanium mesh electrode modified with lead-tin alloy, and the cation exchange membrane is a monovalent selective cation exchange membrane. Sodium sulfate solution is injected into the anode chamber of the electrolytic cell. The anode is a ruthenium-iridium titanium-shaped stable anode. An independent circulating protective chamber is set between the cathode chamber and the anode chamber. Electrolysis is carried out for 4 hours at a current density of 30 mA / cm² and an electrolyte temperature of 55°C to reduce the glyphosate in the mother liquor to glyphosate and obtain a glyphosate-rich conversion solution.

[0052] (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 3.0, add polydopamine bionic affinity seed crystals with a particle size of 200 nm, the amount added is 0.5% of the glyphosate mother liquor mass, cool down to 8 °C at a rate of 0.5 °C / min, grow crystals for 5 h, and separate high-purity glyphosate crystals and crystallization mother liquor.

[0053] (4) Resource recovery by bipolar membrane electrodialysis: The crystallization mother liquor is pretreated by adsorption with macroporous resin and diluted to a conductivity of 60 mS / cm. It is then pumped into a bipolar membrane electrodialysis system. The bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane". The operating parameters are: unit operating voltage 3.5V, current density 80mA / cm², operating temperature 35℃, and circulation flow rate of each compartment 3.0L / min. Under the action of DC electric field, hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated water with total dissolved solids content <500mg / L are recovered.

[0054] (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is then absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated, and collected to obtain phosphoric acid solution.

[0055] Comparative Example 1

[0056] The resource recovery and treatment method of glyphosate mother liquor in this comparative example is the same as that in Example 1. The difference is that after oxidation pretreatment, electrochemical reduction is omitted in this comparative example. The pH is directly adjusted for crystallization, and the mother liquor is evaporated, concentrated, and then incinerated.

[0057] Comparative Example 2

[0058] The resource recovery and treatment method of glyphosate mother liquor in this comparative example is roughly the same as that in Example 1. The difference is that the biomimetic affinity crystallization step is omitted in this comparative example. PDA seed crystals are not added. Instead, a large amount of ethanol is added for solvent crystallization.

[0059] Comparative Example 3

[0060] The resource recovery and treatment method of glyphosate mother liquor in this comparative example is roughly the same as that in Example 1. The difference is that the bipolar membrane electrodialysis step is omitted in this comparative example, and the crystallization mother liquor is not treated but directly treated as wastewater.

[0061] Comparative Example 4

[0062] The resource recovery and treatment method of glyphosate mother liquor in this comparative example is roughly the same as that in Example 1. The difference is that this comparison uses a conventional two-chamber electrolytic cell with no protection chamber design, and sodium sulfate solution is injected into the anode chamber.

[0063] Comparative Example 5

[0064] The resource recovery and treatment method of glyphosate mother liquor in this comparative example is roughly the same as that in Example 1. The difference is that the hydrochloric acid / phosphoric acid mixed solution in this comparison is not subjected to thermal decomposition separation, but is directly added with an equivalent amount of lime milk to precipitate and recover the mixed calcium salt.

[0065] Experimental Example

[0066] The recovered products of Examples 1-3 and Comparative Examples 1-5 were compared, as shown in Table 1.

[0067] Table 1. Performance test results of the embodiments and comparative examples.

[0068] glyphosate total recovery ≥90% ≥90% ≥90% 70% ≥90% ≥90% ≥90% ≥90% glyphosate product purity ≥99.0% ≥99.0% ≥99.0% 95% 90% ≥99.0% ≥99.0% ≥99.0% Where did glyphosate go? Transform into products Transform into products Transform into products Becomes impurities / waste Entering the mother liquor Discard after entering the mother liquor Transform into products Transform into products Sodium chloride resource utilization rate >98% >98% >98% 0% >98% 0% >98% >98% Phosphorus resource utilization rate >98% >98% >98% Low >98% 0% >98% Low Process water reuse rate >95% >95% >95% 0% >95% 0% >95% >95% Anode life >2 years >2 years >2 years not applicable not applicable not applicable 12 months >2 years End-of-life waste generation Zero emissions Zero emissions Zero emissions Large amounts of solid waste / waste liquid Zero emissions Large amounts of high-salinity wastewater Zero emissions Mixed calcium salt sludge Value of recycled acids and alkalis High purity products High purity products High purity products none High purity products none High purity products Mixed low-value substances

[0069] As shown in Table 1, Comparative Example 1, without electrochemical reduction, did not convert glyphosate, which competed with glyphosate during crystallization, resulting in a direct loss of 20% in recovery rate. Furthermore, co-crystallization reduced the product purity to only 95%. This represents a common ceiling for traditional methods. Comparative Example 2 sacrificed the environmental friendliness of the process in pursuit of purity. While organic solvent methods can achieve 99%, they introduce safety and residue risks. Example 1, through the electrochemical reduction method in step 2, employs a "molecular reconstruction" strategy to convert the impurity glyphosate into the target product glyphosate in situ, fundamentally solving the separation problem and directly increasing the upper limit of recovery rate. Step 3, through biomimetic affinity crystallization, achieves specific capture and induced nucleation of glyphosate molecules in an aqueous phase without organic solvents, eliminating residual impurities and overcoming the purity bottleneck of high-salt systems. Both methods synergistically achieve both high yield and high purity.

[0070] Comparative Example 3, with its crystallization mother liquor without electrodialysis, contained high concentrations of sodium chloride and residual phosphorus. Direct treatment resulted in resource waste, and Comparative Example 5 attempted recovery but the pathway was unsatisfactory. The product of the lime neutralization method was a mixed sludge of calcium chloride and calcium phosphate, which was difficult to separate and had extremely low value, transforming "wastewater" into "solid waste," resulting in low phosphorus resource utilization. In Example 1, step 4 used bipolar membrane electrodialysis to "crack" the high-salt wastewater into hydrochloric acid and caustic soda, and recovered pure water, transforming salt and water from "waste" into recyclable production raw materials. Step 5 used pyrolysis to separate the mixed acid into high-value pure hydrochloric acid and phosphoric acid products, avoiding the generation of mixed calcium salts and maximizing the recovery value of phosphorus. These two steps transformed all the outputs at the end of the process into valuable products. Comparative Example 4 lacked a protective chamber, exposing the engineering risks of the electrochemical reduction step. Trace chloride ion migration is an inherent problem in membrane electrolysis; without protection, it would corrode and destroy the expensive ruthenium-iridium-titanium anode within months, leading to soaring costs and operational interruptions. Example 1, on the other hand, had a protective chamber with independent circulation. It does not change the main reaction, but at a very low cost, it ensures a stable lifespan of the core electrode for several years.

[0071] Therefore, this invention provides a resource-based recovery and treatment method for glyphosate mother liquor. It utilizes electrochemical reduction to selectively convert difficult-to-separate glyphosate in the mother liquor into glyphosate, improving atom utilization. Synergistic control of the cathode material, current density, and pH enables site-specific breaking of the CN bonds in aliphatic tertiary amines, ultimately increasing the total glyphosate recovery rate. The introduction of polydopamine nanocrystals, utilizing their surface molecular imprinting effect, allows them to recognize glyphosate molecules through multi-point non-covalent bonds even in extremely high salinity systems, inducing their directional nucleation. This overcomes the common bottleneck of low purity in crystallized products from high-salt organic systems and eliminates the need for additional organic solvents. Subsequent bipolar membrane electrodialysis directly decomposes sodium chloride into high-value hydrochloric acid and caustic soda, while simultaneously recovering process water, hydrochloric acid, and phosphoric acid. The entire process generates no secondary waste, converting salt, phosphorus, and carbon into products, achieving true zero emissions. The entire reaction temperature does not exceed 70℃, and both the electrochemical and bipolar membrane processes operate in the range of low voltage and high current efficiency. Compared with the traditional evaporation-incineration method, energy consumption is greatly reduced, and the risk of equipment corrosion and secondary pollution is extremely small, which has broad application prospects.

[0072] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for the resource-based recovery and treatment of glyphosate mother liquor, characterized in that, Includes the following steps: (1) Oxidative pretreatment: An oxidant was added to the glyphosate mother liquor, and the reaction was carried out under heating conditions. Then the system was cooled and the pH of the system was adjusted to 1.0-2.5 to obtain the pretreated mother liquor. (2) Electrochemical selective reduction: The pretreated mother liquor is pumped into the cathode chamber of an electrolytic cell equipped with a cation exchange membrane, and a conductive medium without chloride ions is injected into the anode chamber of the electrolytic cell. Constant current electrolysis is performed at the cathode using a high hydrogen evolution overpotential electrode to reduce glyphosate in the mother liquor to glyphosate, thereby obtaining a glyphosate-rich conversion solution. (3) Bionic affinity-induced crystallization: Adjust the pH of the conversion solution to 2.5-3.0, add nano-polydopamine bionic affinity crystal seeds, and grow crystals by programmed cooling. Then separate high-purity glyphosate crystals and crystallization mother liquor. (4) Bipolar membrane electrodialysis resource recovery: After the crystallization mother liquor is pretreated by adsorption and diluted, it is pumped into the bipolar membrane electrodialysis system to recover hydrochloric acid / phosphoric acid mixed acid solution, sodium hydroxide solution and desalinated fresh water under the action of DC electric field; (5) Separation of mixed acid solution: The hydrochloric acid / phosphoric acid mixed acid solution is heated to the azeotropic point to release hydrogen chloride gas, which is then absorbed by water to obtain hydrochloric acid solution. The residual liquid at the bottom of the vessel is heated, concentrated, and collected to obtain phosphoric acid solution.

2. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The oxidant in step (1) is hydrogen peroxide with a mass fraction of 30-40%, and the amount added is 0.3%-0.5% of the mass of glyphosate mother liquor. The heating reaction temperature is 50-70℃, and the reaction time is 0.5-1h.

3. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, In step (2), the anode is a ruthenium-iridium titanium-shaped stable anode, and the cathode is a titanium mesh electrode modified with lead-tin alloy.

4. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The electrolysis conditions in step (2) are: current density 5-30 mA / cm², electrolyte temperature 25-55℃, and electrolysis time 0.5-4h.

5. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The cation exchange membrane in step (2) is a monovalent selective cation exchange membrane. An independent circulating protective chamber is provided between the cathode chamber and the anode chamber. The anolyte in the anode chamber is a sodium sulfate solution.

6. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The nano-polydopamine biomimetic affinity seed crystals in step (3) have a particle size of 50-200 nm and are added in an amount of 0.1%-0.5% of the glyphosate mother liquor mass.

7. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The programmed cooling rate in step (3) is 0.1 to 0.5 °C / min, the final temperature is 0 to 8 °C, and the crystal growth time is 1 to 5 h.

8. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, In step (4), the bipolar membrane electrodialysis system adopts a three-compartment repeating unit configuration of "bipolar membrane-anion exchange membrane-cation exchange membrane"; the operating parameters are: unit operating voltage 1.5~3.5V, current density 20~80mA / cm², operating temperature 20~35℃, and circulation flow rate of each compartment 0.5~3.0L / min.

9. The method for resource recovery and treatment of glyphosate mother liquor according to claim 1, characterized in that, The adsorption pretreatment in step (4) uses macroporous resin adsorption; the dilution is to adjust the conductivity of the mother liquor to 40-60 mS / cm; the total dissolved solids content of the obtained desalinated fresh water is <500 mg / L.