A method for cleaning and treating diglycophosphine wastewater

Abstract

The present invention relates to the field of wastewater treatment, in particular to the field of IPC CO2F9, and further relates to a method for cleaning and treating diethylene glycol phosphine wastewater, comprising the following steps: (1) removing mechanical impurities from diethylene glycol phosphine mother liquor and filtering it through a primary membrane to obtain a primary membrane thin liquid and a primary membrane concentrated liquid; (2) adding an oxidant to the primary membrane thin liquid obtained in step (1) for oxidation treatment; (3) adding alkali to adjust the pH of the primary membrane thin liquid obtained in step (2), and filtering it through a secondary membrane to obtain a secondary membrane thin liquid and a secondary membrane concentrated liquid; (4) evaporating the secondary membrane thin liquid obtained in step (3) to obtain sodium chloride; and evaporating the secondary membrane concentrated liquid to obtain sodium chloride and a secondary membrane concentrated liquid residue. The present invention can recycle "waste" substances such as diethylene glycol phosphine, sodium chloride, and phosphorous acid in diethylene glycol phosphine wastewater into resources; the formaldehyde removal rate is above 96%, the diethylene glycol phosphine recovery rate is above 90%, and the sodium chloride content is above 98.5%.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, in particular to the field of IPC CO2F9, and further to a method for cleaning and treating diglycophosphine wastewater. Background Art

[0002] Glyphosate is a foliar herbicide developed by the renowned American company Monsanto. It boasts high efficacy, broad spectrum, low toxicity, low residue, easy microbial decomposition, soil-safety, and lethality to most plants. Common glyphosate synthesis routes include the glycine route (alkyl ester method) and the iminodiacetonitrile (IDA) method. The IDA method involves alkaline hydrolysis and acidification of iminodiacetonitrile followed by a direct condensation reaction with phosphorous acid and formaldehyde. The resulting product, glyphosate, is then concentrated, centrifuged, and dried. However, the acidification process generates a large amount of NaCl, producing a large amount of salt-containing mother liquor during the preparation of glyphosate. This mother liquor is high in impurities, highly acidic, and contains formaldehyde, making it difficult to handle, costly, and environmentally polluting.

[0003] The traditional method for treating wastewater generated during glyphosate production involves adding raw glyphosate powder to a mother liquor containing 10% organophosphorus impurities and nearly 20% sodium chloride to create a 10% aqueous glyphosate solution, which is then sold directly. With growing environmental awareness, my country has gradually increased its efforts to control the "three wastes" from various pesticides, and traditional treatment methods are gradually being phased out.

[0004] Chinese patent CN 101717131 A discloses a method for treating diaminoglyphosate wastewater. Specifically, the method involves adding catalytic oxidants sodium nitrite and sodium hypochlorite to the diaminoglyphosate wastewater in a mixing tank, stirring the wastewater evenly, filtering the wastewater, and concentrating it in a multi-effect evaporator at a temperature of 65-100°C and a vacuum of -0.05 to -0.09 MPa. Chinese patent CN 106746135 A discloses a system and process for treating diaminoglyphosate wastewater. The system includes pretreatment, wet oxidation, air stripping absorption, evaporative crystallization, cooling crystallization, and an MVR evaporative crystallization unit.

[0005] Existing methods for treating bis(glyphosate) wastewater primarily recycle sodium chloride and reduce the organic matter content in the wastewater. However, these methods fail to fully utilize the bis(glyphosate) and phosphorus resources in the wastewater. Purifying bis(glyphosate) wastewater, reusing the phosphorus and chlorine resources, and ultimately achieving zero discharge of bis(glyphosate) wastewater are the goals of industry professionals. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for cleaning and treating diphosphine wastewater, comprising the following steps:

[0007] (1) After removing mechanical impurities from the monoglyphosate mother liquor, it enters the primary membrane filtration to obtain the primary membrane dilute liquor and the primary membrane concentrated liquor;

[0008] (2) adding an oxidant to the primary membrane dilute solution obtained in step (1) for oxidation treatment;

[0009] (3) adding alkali to adjust the pH of the primary membrane dilute solution obtained in step (2), and then filtering it through a secondary membrane to obtain a secondary membrane dilute solution and a secondary membrane concentrated solution;

[0010] (4) The secondary membrane dilute liquid obtained in step (3) is evaporated to obtain sodium chloride; the secondary membrane concentrated liquid is evaporated to obtain sodium chloride and secondary membrane concentrated liquid residual liquid.

[0011] The mother liquor of diglyphosate is high-salt wastewater produced by the IDA process for producing diglyphosate, an intermediate of glyphosate. The wastewater contains 20.0-23.5% sodium chloride, 0.2-0.3% formaldehyde, 1.5-2.0% COD, 0.8-1.2% diglyphosate, 0.2-1.0 pH, and 0.8-1.2% phosphorous acid.

[0012] In some preferred embodiments, the primary membrane in step (1) is selected from any one of an aromatic polyamide nanofiltration membrane, a polysulfoneamide nanofiltration membrane, and an aromatic composite nanofiltration membrane.

[0013] In order to improve the rejection rate of diglyphosate, in some preferred embodiments, the primary membrane in step (1) is an aromatic polyamide composite nanofiltration membrane. The aromatic polyamide composite nanofiltration membrane can separate macromolecular organic substances (such as diglyphosate) from small molecules (such as sodium chloride and phosphorous acid). The surface of the aromatic polyamide composite nanofiltration membrane can adsorb charges, and has a high rejection rate for high-concentration diglyphosate. When the diglyphosate concentration is high, the membrane surface adsorbs more charges, the number of oppositely charged ions present in the membrane pores increases, the amount of positive and negative ions accumulated on both sides of the membrane is also large, the osmotic pressure is high, the effective pressure difference between the two sides of the membrane is small, and the rejection rate is high.

[0014] The recovery rate of diglyphosate in the primary membrane concentrate obtained in step (1) is above 90%, and the diglyphosate concentration in the primary membrane dilute liquid is reduced to below 0.12%; the diglyphosate content in the primary membrane concentrate is concentrated to 3.5-5.0%, and the diglyphosate can be returned to the diglyphosate crystallization system for crystallization recovery of diglyphosate.

[0015] Since the nanofiltration membrane cannot retain formaldehyde in the dimethylaminophosphine mother liquor, the primary membrane thin liquor contains a high concentration of formaldehyde. If it is directly evaporated, the formaldehyde content in the evaporated water is too high to be directly biodegraded. By oxidizing the formaldehyde in the primary membrane thin liquor obtained in step (1), it can be converted into carbon dioxide and water.

[0016] In some preferred embodiments, the oxidant in step (2) is selected from at least one of hydrogen peroxide, hypochlorous acid, sodium hypochlorite, and potassium permanganate.

[0017] In some preferred embodiments, the oxidant is hydrogen peroxide; hydrogen peroxide has the advantages of low cost, no residue, and no introduction of other impurities into the diphosphine wastewater. In addition, hydrogen peroxide can form a homogeneous environment with the diphosphine wastewater, can fully contact with the diphosphine wastewater, and increase the oxidation reaction rate.

[0018] To reduce the oxidation reaction time, in some preferred embodiments, the amount of oxidant added is 0.2-1.5% of the volume of the diphosphine wastewater, preferably 0.5%. Increasing the amount of oxidant added increases the number of effective collisions of activated molecules in the diphosphine wastewater, accelerating the oxidation reaction rate; however, excessively high additions do not significantly improve oxidation efficiency and increase costs.

[0019] In order to further improve the oxidation reaction rate and formaldehyde removal rate, in some preferred embodiments, the oxidation reaction temperature in step (2) is 30-80° C., preferably 50° C. Increasing the temperature is beneficial to accelerating the reaction rate, but too high a temperature will cause ineffective decomposition of hydrogen peroxide, resulting in a decrease in the formaldehyde removal rate.

[0020] In some preferred embodiments, the oxidation reaction time in step (2) is 0.5 to 2 hours, preferably 1 hour.

[0021] The formaldehyde removal rate in the primary membrane dilute liquid obtained in step (2) is above 96%, and the formaldehyde content is reduced to below 0.01%.

[0022] In order to completely convert the phosphorous acid in the primary membrane dilute liquid obtained in step (2) into phosphite, in some preferred embodiments, the base in step (3) is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and sodium carbonate, preferably sodium hydroxide.

[0023] In some preferred embodiments, the pH of the primary membrane dilute liquid after oxidation in step (3) is adjusted to 3 to 7, preferably 4. Excess sodium hydroxide reacts completely with phosphorous acid to convert phosphorous acid into sodium phosphite.

[0024] In order to reduce the total phosphorus content in the primary membrane dilute liquid obtained in step (2), in some preferred embodiments, the secondary nanofiltration membrane is selected from a polypiperazineamide nanofiltration membrane or a sulfonated polyethersulfone nanofiltration membrane, preferably a polypiperazineamide composite nanofiltration membrane; the polypiperazineamide composite nanofiltration membrane has good hydrophilicity and high surface negative charge. Due to the charging effect, monovalent sodium chloride can easily pass through, while polyvalent sodium phosphite is difficult to pass through, thereby separating sodium chloride and sodium phosphite.

[0025] The total phosphorus content in the secondary membrane dilute solution obtained in step (3) can be reduced to 0.035-0.045%; the phosphorous acid content in the secondary membrane concentrated solution is 1.2-1.5%.

[0026] In some preferred embodiments, the secondary membrane dilute solution and the secondary membrane concentrated solution obtained in step (3) are directly evaporated to remove sodium chloride, and the evaporated water can be sent to a biochemical device for treatment and recycling; the evaporated sodium chloride can be sold after drying.

[0027] In step (4), the residual liquid of the secondary membrane concentrate is incinerated to prepare sodium pyrophosphate.

[0028] After drying, the sodium chloride content is above 98.5%, the total phosphorus content is below 50ppm, there is no formaldehyde residue, and the TOC is below 100ppm.

[0029] The total phosphorus content of the residual liquid after evaporation of the secondary membrane concentrate is 7.0-8.0%, and the specific gravity is 1.5-1.55 g / cm 3 , chloride ion content is 1.2~2.0%, and COD is 3.0~4.0%.

[0030] In some preferred embodiments, sodium pyrophosphate is prepared by incinerating the residual liquid obtained by evaporating the secondary membrane concentrate in step (4).

[0031] In some preferred embodiments, the incineration temperature is 600-900° C., preferably 800° C.; the prepared sodium pyrophosphate content is above 95%, and the formaldehyde content of the distilled water is below 0.006%, which can be reused for the preparation of diglycophos.

[0032] Beneficial effects:

[0033] 1. The present invention can convert "waste" substances such as diglyphosate, sodium chloride, phosphorous acid, etc. in diglyphosate wastewater into resources.

[0034] 2. The present invention uses hydrogen peroxide as an oxidant. Hydrogen peroxide is low in cost, easily available, has no residue, and will not introduce other impurities into the diphosphine wastewater.

[0035] 3. The present invention oxidizes formaldehyde into carbon dioxide and water through oxidation reaction, so that the formaldehyde removal rate is above 96%.

[0036] 4. The present invention uses an aromatic polyamide composite nanofiltration membrane to intercept diglycol phosphine, and the recovery rate of diglycol phosphine is above 90%.

[0037] 5. The present invention recovers phosphorous acid through a polypiperazineamide composite membrane, and the total phosphorus in the secondary membrane dilute liquid can be reduced to 0.035-0.045%.

[0038] 6. The sodium chloride content prepared by evaporation in the present invention is above 98.5%, and no formaldehyde remains in the sodium chloride.

[0039] 7. The formaldehyde content in the evaporated water of the present invention is below 0.006%, and can be completely recycled to the production of diglycophos.

[0040] 8. The method for cleaning and treating bis(ethylene glycol)phosphine wastewater of the present invention is simple to operate, low in cost, and reduces the difficulty of treating bis(ethylene glycol)phosphine wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The figure is a schematic flow chart of the method for cleaning and treating diglycophosphine wastewater according to the present invention. DETAILED DESCRIPTION

[0042] The method for cleaning and treating diglycophosphine wastewater of the present invention is further described in detail below with reference to the accompanying drawings.

[0043] Example 1

[0044] Example 1 provides Figure 1 The method for cleaning and treating diglycophosphine wastewater shown comprises the following steps:

[0045] (1) After removing mechanical impurities from the monoglyphosate mother liquor, it enters the primary membrane filtration to obtain the primary membrane dilute liquor and the primary membrane concentrated liquor;

[0046] (2) adding an oxidant to the primary membrane dilute solution obtained in step (1) for oxidation treatment;

[0047] (3) adding alkali to adjust the pH of the primary membrane dilute solution obtained in step (2), and then filtering it through a secondary membrane to obtain a secondary membrane dilute solution and a secondary membrane concentrated solution;

[0048] (4) The secondary membrane dilute liquid obtained in step (3) is evaporated to obtain sodium chloride; the secondary membrane concentrated liquid is evaporated to obtain sodium chloride and secondary membrane concentrated liquid residual liquid.

[0049] The mother liquor of diglyphosate is a high-salt wastewater produced by the production of diglyphosate, an intermediate of glyphosate by the IDA process. The sodium chloride content in the wastewater is 21.8%, the formaldehyde content is 0.18%, the COD is 13680 ppm, the diglyphosate content is 0.85%, the pH is 0.54, and the phosphorous acid content is 0.77%.

[0050] The primary membrane in step (1) is an aromatic polyamide composite nanofiltration membrane purchased from Shandong Yupeng Environmental Protection Technology Co., Ltd., model: HNF40-8040.

[0051] In the step (2), the oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 0.5% of the volume of the diphosphine wastewater.

[0052] The oxidation reaction temperature in step (2) is 50°C.

[0053] The oxidation reaction time in step (2) is 1 h.

[0054] The alkali in step (3) is sodium hydroxide.

[0055] The pH of the primary membrane dilute liquid after oxidation in step (3) is 4.

[0056] The secondary nanofiltration membrane is a polypiperazineamide composite membrane purchased from Dow Chemical Company, model: NF200.

[0057] In the step (4), the residual liquid of the secondary membrane concentrate is incinerated to prepare sodium pyrophosphate.

[0058] The incineration temperature is 800°C.

[0059] Example 2

[0060] Example 2 provides Figure 1 The method for cleaning and treating diglycophosphine wastewater shown comprises the following steps:

[0061] (1) The dimethylphosphine wastewater is filtered through a primary membrane to obtain a primary membrane dilute solution and a primary membrane concentrated solution;

[0062] (2) adding an oxidant to the primary membrane dilute solution obtained in step (1) for oxidation treatment;

[0063] (3) adding alkali to adjust the pH of the primary membrane dilute solution obtained in step (2), and then filtering it through a secondary membrane to obtain a secondary membrane dilute solution and a secondary membrane concentrated solution;

[0064] (4) Evaporating the secondary membrane dilute solution and the secondary membrane concentrated solution obtained in step (3).

[0065] The mother liquor of diglyphosate is a high-salt wastewater produced by the IDA process for the production of diglyphosate, an intermediate of glyphosate. The wastewater contains 24.6% sodium chloride, 0.29% formaldehyde, 16320 ppm COD, 1.54% diglyphosate, 0.14 pH value and 0.98% phosphorous acid.

[0066] The primary membrane in step (1) is an aromatic polyamide composite nanofiltration membrane purchased from Shandong Yupeng Environmental Protection Technology Co., Ltd., model: HNF40-8040.

[0067] In the step (2), the oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 0.5% of the volume of the diphosphine wastewater.

[0068] The oxidation reaction temperature in step (2) is 50°C.

[0069] The oxidation reaction time in step (2) is 1 h.

[0070] The alkali in step (3) is sodium hydroxide.

[0071] The pH of the primary membrane dilute liquid after oxidation in step (3) is 4.

[0072] The secondary nanofiltration membrane is a polypiperazineamide composite membrane purchased from Dow Chemical Company, model: NF200.

[0073] In the step (4), the residual liquid of the secondary membrane concentrate is incinerated to prepare sodium pyrophosphate.

[0074] The incineration temperature is 800°C.

[0075] Example 3

[0076] Example 3 provides the following Figure 1 The method for cleaning and treating diglycophosphine wastewater shown is the same as that of Example 1, except that the oxidant in step (2) is sodium hypochlorite.

[0077] Example 4

[0078] Example 4 provides Figure 1 The method for cleaning and treating diphosphine wastewater shown is the same as that in Example 1, except that the oxidation reaction temperature in step (2) is 80°C.

[0079] Example 5

[0080] Example 5 provides Figure 1 The method for cleaning and treating diglycophosphine wastewater shown is the same as that in Example 1, except that the secondary nanofiltration membrane is a polytetrafluoroethylene nanofiltration membrane purchased from Shandong Bona Group, model: 300D.

[0081] Performance testing method:

[0082] 1. Recovery rate of diglycol phosphine = content of diglycol phosphine after crystallization / content of diglycol phosphine before crystallization × 100%; the diglycol phosphine content was determined using standard DB51 / T1776-2014.

[0083] 2. Formaldehyde removal rate = (formaldehyde content in wastewater before treatment - formaldehyde content in wastewater after treatment) / formaldehyde content in wastewater before treatment × 100%; the formaldehyde content is measured using acetylacetone spectrophotometry.

[0084] 3. Phosphorous acid removal rate = (phosphorous acid content in wastewater before treatment - phosphorous acid content in wastewater after treatment) / phosphorous acid content in wastewater before treatment × 100%; the phosphorous acid content is determined using standard HG / T2520-93.

[0085] 4. Sodium chloride content: Determined by the adsorption indicator method - Fayangsi method.

[0086] 5. Total phosphorus content: Determined by continuous flow-ammonium molybdate spectrophotometry.

[0087] 6. TOC: Measured using a total organic carbon analyzer.

[0088] 7. Sodium pyrophosphate content: measured using standard HG / T 2968-2009.

[0089] Performance test results:

[0090] Treatment results of Example 1: After treatment, the recovery rate of diglycol in the primary membrane concentrate was 92.3%, the formaldehyde removal rate in the primary membrane dilute liquid was 96.1%, and the phosphorous acid removal rate in the secondary membrane dilute liquid was 93.5%; the sodium chloride content of the secondary membrane dilute liquid after evaporation and drying was 98.8%, the total phosphorus was 33 ppm, there was no formaldehyde residue, and the TOC was 82 ppm; the sodium pyrophosphate content prepared by incineration was 96.4%.

[0091] Treatment results of Example 2: After treatment, the recovery rate of dimethyl phosphine in the primary membrane concentrate was 91.7%, the formaldehyde removal rate in the primary membrane dilute liquid was 96.9%, and the phosphorous acid removal rate in the secondary membrane dilute liquid was 91.8%; the sodium chloride content of the secondary membrane dilute liquid after evaporation and drying was 98.6%, the total phosphorus was 37 ppm, there was no formaldehyde residue, and the TOC was 75 ppm; the sodium pyrophosphate content prepared by incineration was 95.7%.

[0092] Treatment results of Example 3: After treatment, the recovery rate of diglycol in the primary membrane concentrate was 92.1%, the formaldehyde removal rate in the primary membrane dilute liquid was 93.8%, and the phosphorous acid removal rate in the secondary membrane dilute liquid was 90.8%; the sodium chloride content of the secondary membrane dilute liquid after evaporation and drying was 97.3%, the total phosphorus was 36 ppm, there was no formaldehyde residue, and the TOC was 86 ppm; the sodium pyrophosphate content prepared by incineration was 94.2%.

[0093] Treatment results of Example 4: After treatment, the recovery rate of diglycol in the primary membrane concentrate was 92.2%, the formaldehyde removal rate in the primary membrane dilute liquid was 93.1%, and the phosphorous acid removal rate in the secondary membrane dilute liquid was 90.5%; the sodium chloride content of the secondary membrane dilute liquid after evaporation and drying was 96.8%, the total phosphorus was 38 ppm, there was no formaldehyde residue, and the TOC was 89 ppm; the sodium pyrophosphate content prepared by incineration was 93.9%.

[0094] Treatment results of Example 5: After treatment, the recovery rate of diglycol in the primary membrane concentrate was 92.2%, the formaldehyde removal rate in the primary membrane dilute liquid was 96.2%, and the phosphorous acid removal rate in the secondary membrane dilute liquid was 92.1%; the sodium chloride content of the secondary membrane dilute liquid after evaporation and drying was 96.6%, the total phosphorus was 35 ppm, there was no formaldehyde residue, and the TOC was 84 ppm; the sodium pyrophosphate content prepared by incineration was 95.7%.

Claims

1. A method for cleaning a monoglyphosate mother liquor, comprising the following steps: (1) After removing mechanical impurities from the monoglyphosate mother liquor, it enters the first-stage membrane filtration to obtain the first-stage membrane dilute liquor and the first-stage membrane concentrated liquor; (2) adding an oxidant to the primary membrane dilute solution obtained in step (1) for oxidation treatment; (3) adding alkali to adjust the pH of the primary membrane dilute solution obtained in step (2), and then filtering it through the secondary membrane to obtain the secondary membrane dilute solution and the secondary membrane concentrated solution; (4) The secondary membrane dilute solution obtained in step (3) is evaporated to obtain sodium chloride; the secondary membrane concentrated solution is evaporated to obtain sodium chloride and secondary membrane concentrated solution residual solution; In step (1), the primary membrane is an aromatic polyamide composite nanofiltration membrane; In step (3), the secondary membrane is a polypiperazineamide nanofiltration membrane; The secondary membrane dilute solution and the secondary membrane concentrated solution obtained in step (3) are directly evaporated to remove sodium chloride, and the evaporated water is sent to a biochemical device for treatment and recycling; In step (4), the residual liquid of the secondary membrane concentrate is incinerated to prepare sodium pyrophosphate; The incineration temperature is 600-900°C.

2. The method for cleaning a monoethylene glycol phosphine mother liquor according to claim 1, wherein: In step (2), the oxidant is selected from any one of hydrogen peroxide, hypochlorous acid, sodium hypochlorite, and potassium permanganate.

3. The method for cleaning a monoethylene glycol phosphine mother liquor according to claim 1, wherein: The amount of oxidant added in step (2) is 0.2-1.5% of the volume of the monoglyphosate mother solution.

4. The method for cleaning a monoethylene glycol phosphine mother liquor according to claim 1, wherein: The reaction temperature of the oxidation treatment process in step (2) is 30-80°C.

5. The method for cleaning a monoethylene glycol phosphine mother liquor according to claim 1, wherein: The reaction time of the oxidation treatment process in step (2) is 0.5 to 2 hours.

6. The method for cleaning a monoethylene glycol phosphine mother liquor according to claim 1, wherein: In step (3), the alkali is selected from any one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

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