A deep phosphorus removal treatment method for glyphosate wastewater

Abstract

The present invention discloses a method for deep phosphorus removal treatment of glyphosate wastewater. First, solid waste salt generated by upstream production units is dissolved into saturated brine, and suspended solids in the brine are removed through a ceramic membrane. A nanofiltration membrane device is then used to intercept phosphorus-containing substances in the brine. The concentrated solution is returned to the upstream production unit for treatment. Finally, the permeate is passed through a phosphorus removal resin to further adsorb residual phosphorus-containing substances. The resulting brine, after adsorption of heavy metal ions by a chelating resin, can be directly used in ion-exchange membrane caustic soda production. By deeply removing phosphorus-containing substances from the waste salt, the method allows it to be used as raw material in the ion-exchange membrane caustic soda industry, turning waste salt into valuable resources and significantly reducing production costs in both the chlor-alkali and glyphosate industries.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced sewage treatment and the field of chlor-alkali chemical industry, and particularly relates to an advanced phosphorus removal treatment method for glyphosate wastewater. Background Art

[0002] Glyphosate is a highly effective, non-selective herbicide. Currently, glyphosate is produced industrially primarily through the glycine process and the iminodiacetic acid (IDA) process. The glycine process, for example, generates large amounts of NaCl during the recovery of the solvent methanol and the catalyst triethylamine.

[0003] Because glyphosate waste salts contain organic raw materials used in glyphosate production and byproducts from the synthesis process, particularly phosphorus-containing substances (inorganic and organic), they cannot be directly used in industrial production, severely restricting the development of the glyphosate industry. With tightening environmental regulations and rising environmental costs, recycling glyphosate waste salts has become a key issue in reducing production costs.

[0004] The existing technologies all use Fenton oxidation followed by precipitation for phosphorus removal, which can effectively remove organic phosphorus in glyphosate production wastewater and reduce the TOC value of wastewater. However, this method has the following defects: During the catalytic oxidation process, Fe 2+ The addition of H2O2 reagent cannot be done uniformly, resulting in a high usage rate of the oxidant and an increase in treatment costs. In addition, the phosphorus removal rate of the wastewater after catalytic oxidation and calcium salt precipitation is low. Chinese invention patent application number 201410224673.5 discloses a method for refining waste brine in glyphosate production. The method adopts the Fenton oxidation method to greatly reduce the total organic matter and total phosphorus content in the waste brine. However, the Fe 2+ The content is as high as 0.036 mol / L. If the treated glyphosate waste brine is used as the raw material for ion-exchange membrane caustic soda production, further treatment of the introduced Fe 2+ . Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a method for deep phosphorus removal treatment of glyphosate wastewater, which uses the physical interception of nanofiltration membranes and the physical adsorption characteristics of phosphorus removal resins to reduce the total phosphorus content in glyphosate wastewater to a level that meets the requirements for ion-exchange membrane caustic soda production. The specific steps are as follows:

[0006] A method for deep impurity removal treatment of glyphosate wastewater, the specific process steps are as follows:

[0007] (1) filtering the glyphosate waste brine with a ceramic membrane to remove suspended solids and making the solid content of the permeate ≤1 ppm to obtain brine;

[0008] (2) filtering the brine from step (1) using a nanofiltration membrane to obtain a permeate;

[0009] (3) adsorbing the permeate with a phosphorus removal resin to obtain a filtrate;

[0010] (4) The filtrate is adsorbed by chelating resin to complete the deep phosphorus removal of glyphosate wastewater.

[0011] The process parameters of glyphosate waste brine are: temperature 50-60℃, NaCl concentration 290-310g / L, pH 6-11, Ca 2+ +Mg 2+ Content ≤2ppm, total phosphorus 80-120ppm.

[0012] In the preferred process, the glyphosate waste brine is maintained at a temperature of 50-55°C and a concentration of 290-300 g / L. This is because ceramic membranes require a processing temperature of 50-60°C, while nanofiltration membrane devices require a feed temperature of 35-40°C. Furthermore, the permeate from the ceramic membrane unit requires the addition of pure water to dilute the NaCl concentration to 270-280 g / L. Both excessively high and low temperature and salt concentrations can reduce the nanofiltration membrane's ability to retain phosphorus-containing substances, so the above process parameters are preferred.

[0013] In step (1), the glyphosate waste brine is filtered through a ceramic membrane and then Na2SO3 is added to remove free chlorine in the permeate. The NaCl content is controlled at 270-280 g / L, the permeate is adjusted to 6.0-8.0, and the temperature is adjusted to 35-40°C.

[0014] When performing the nanofiltration membrane in step (2), a three-stage filtration method is adopted, the pressure entering the nanofiltration membrane is 2-3 MPa, the concentration multiple is 3-5 times, the phosphorus retention rate is ≥80%, and the NaCl retention rate is ≤10%.

[0015] After filtration, the permeate is heated to 40-60°C and the pH is adjusted to 8-10.

[0016] The concentration multiple in step (2) is 3 times, 4 times, or 5 times.

[0017] The concentration factor used in this invention refers to the concentration factor of the brine. After the brine passes through the ceramic membrane, the NaCl concentration and pH are adjusted, free chlorine is removed, and the temperature is lowered before being filtered through a nanofiltration membrane. The permeate is then processed in the next step. The volume of the concentrate corresponds to the concentration factor of the brine. For example, if the volume of the brine is V, the permeate V1 and concentrate V2 are obtained after nanofiltration. The concentration factor is V / V2. The nanofiltration concentrate is returned to the upstream glyphosate production unit for recycling. The total phosphorus content of the permeate after nanofiltration is ≤10.0 ppm.

[0018] The preparation method of the phosphorus removal resin of the present invention comprises the following steps:

[0019] Step (1): Pretreatment: Weigh polystyrene-divinylbenzene polymer, wash it with NaOH and HCl, and then wash it with deionized water until it is neutral;

[0020] Step (2): Post-crosslinking: soaking the pretreated material in 1,2-dichloroethane, fully expanding it, adding 1-10% ferric chloride by mass fraction of polystyrene-divinylbenzene polymer and fully dissolving it, and post-crosslinking it in a water bath to obtain a crosslinked resin;

[0021] Step (3): Chemical modification: the cross-linked resin is fully immersed in a 1,2-dichloroethane solution and filtered, a trimethylamine solution with a mass fraction of 0.1-5% of the polystyrene-divinylbenzene polymer is added to carry out a water bath reaction, and after the reaction is completed, the resin is washed with water until neutral to obtain an adsorption resin;

[0022] Step (4): Loading Fe(OH)3: Adding the adsorption resin to a FeCl3·6H2O-HCl mixed solution for reaction, filtering, vacuum drying, and obtaining a phosphorus removal resin loaded with Fe(OH)3.

[0023] The average pore size of the resin is 5-10 nm; the pore volume is 0.02-0.10 cm 3 / g; specific surface area is 8 to 15m 2 / g; the resin water content is 45-60% by weight.

[0024] During the process of adsorption treatment of the permeate with phosphorus removal resin, the flow rate through the tower is 3-5BV / h and the effluent volume is ≤120BV.

[0025] The filtrate after phosphorus removal resin adsorption is heated to 58-62°C and the pH is maintained at 9-11 for chelate resin adsorption. During the adsorption treatment of the filtrate with the chelate resin, the flow rate through the tower is 3-5BV / h and the effluent volume is ≤120BV.

[0026] Under the above-mentioned phosphorus removal resin process conditions, heating the permeate after nanofiltration membrane filtration to 40-60°C and adjusting the pH to 8-10 with NaOH can promote the phosphorus removal resin to achieve the best adsorption effect, and the organic phosphorus removal rate in the brine after adsorption is ≥50%.

[0027] The chelating resin is a macroporous styrene-based ion exchange resin containing an iminodiacetic acid chelating group, such as any one of the products D401, D402, D403, D751, D850 and D851 of Shanghai Kaiping Resin Co., Ltd.

[0028] Furthermore, the brine obtained in step 4) after adsorption by the phosphorus removal resin is heated to 58-62° C., and the pH is adjusted to 9-11 with NaOH to achieve the best effect of removing metal ions by the chelating resin tower.

[0029] Glyphosate waste salts cannot be directly used in industrial production because they contain organic raw materials used in glyphosate production and byproducts generated during the synthesis process, especially phosphorus-containing substances (inorganic and organic phosphorus). If the problem of organic matter in the waste salts can be solved, the NaCl in the glyphosate waste salts can be used as raw materials in the ion-exchange membrane caustic soda industry. The present invention first dissolves the solid waste salts produced by upstream production units into saturated brine, and removes suspended solids in the brine through a ceramic membrane. Then, a nanofiltration membrane device is used to intercept the phosphorus-containing substances in the brine. The concentrated solution is returned to the upstream production unit for treatment. Finally, the permeate is passed through a special phosphorus removal resin to further absorb the residual phosphorus-containing substances. The resulting brine, after adsorbing heavy metal ions with a chelating resin, can be directly used in ion-exchange membrane caustic soda production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below with reference to the following examples. However, the scope of protection claimed in the present invention is not limited to the scope described in the examples.

[0032] Example 1

[0033] The preparation method of the phosphorus removal resin in this embodiment is:

[0034] Step (1): Pretreatment: Weigh polystyrene-divinylbenzene polymer, wash it with NaOH and HCl, and then wash it with deionized water until it is neutral;

[0035] Step (2): Post-crosslinking: the pretreated material is immersed in 1,2-dichloroethane, and after fully expanding, ferric chloride accounting for 2.8% by mass of the polystyrene-divinylbenzene polymer is added and fully dissolved, and post-crosslinking is performed in a water bath to obtain a cross-linked resin;

[0036] Step (3): Chemical modification: the cross-linked resin is fully immersed in a 1,2-dichloroethane solution and filtered, a trimethylamine solution with a mass fraction of 3.5% of the polystyrene-divinylbenzene polymer is added to carry out a water bath reaction, and after the reaction is completed, the resin is washed with water until neutral to obtain an adsorption resin;

[0037] Step (4): Loading Fe(OH)3: Adding the adsorption resin to a 25% by mass FeCl3·6H2O-HCl mixed solution (mixing solid ferric chloride hexahydrate with concentrated hydrochloric acid at a mass volume ratio of kg / L of 2.5-10 and stirring until the solid is completely dissolved) to react, filtering, vacuum drying, and obtaining a phosphorus removal resin loaded with Fe(OH)3.

[0038] In this embodiment, the chelating resin is a macroporous styrene-based ion exchange resin containing an iminodiacetic acid chelating group, specifically the product D403 produced by Shanghai Kaiping Resin Co., Ltd.

[0039] The deep phosphorus removal treatment method for glyphosate wastewater includes the following steps:

[0040] Step 1): Use a storage tank to receive the glyphosate waste brine provided by the upstream production unit, the NaCl concentration in the brine is 292g / L, and the Ca 2+ +Mg 2+ The content was 1.2 ppm, the total phosphorus content was 66.2 ppm (of which organic phosphorus was 45.6 ppm and inorganic phosphorus was 20.6 ppm), the pH was 8.6, and the temperature was 60.2°C;

[0041] Step 2): using a ceramic membrane to remove suspended solids in the glyphosate waste brine to reduce the solid content to 0.5 ppm, thereby obtaining brine;

[0042] Step 3): Na2SO3 is added to the brine from step 2) to remove free chlorine in the brine, and pure water is added to adjust the NaCl concentration to 275 g / L, the pH is adjusted to 7.5, and the temperature is reduced to 36.8°C via a heat exchanger;

[0043] Step 4): 60 L of the brine treated in step 3) was filtered through a nanofiltration membrane. When the permeate volume reached 40 L, the concentrated solution was returned to the upstream glyphosate production unit for treatment. The permeate was then sent to a brine storage tank. The total phosphorus content of the permeate was 9.8 ppm (6.8 ppm of organic phosphorus and 3.0 ppm of inorganic phosphorus). NaOH was then added to adjust the pH to 9.5, and the temperature was then raised to 58.8° C. via a heat exchanger.

[0044] Step 5): The brine (i.e., permeate) after process adjustment in step 4) is subjected to adsorption by a phosphorus removal resin and a chelating resin, respectively, to achieve deep impurity removal treatment of the glyphosate wastewater. During the adsorption process using the phosphorus removal resin or the chelating resin, the outlet brine (i.e., the filtrate) is controlled at an outlet volume of 120 BV. When the flow rates of the two resins are controlled to be the same, the phosphorus content in the outlet brine is obtained when the flow rates are 5 BV / h, 10 BV / h, and 20 BV / h. The trend of the phosphorus content in the brine after adsorption at different flow rates is shown in Table 1.

[0045]

[0046] As can be seen from Table 1, when the tower flow rate is increased to 20BV / h and the effluent volume is 120BV, the phosphorus removal effect of the resin decreases, and it is necessary to shorten the running time to ensure that the removal rate of organophosphorus remains more than 70%. Meanwhile, adopting the technical scheme of the application to achieve the deep phosphorus treatment efficiency of a flow velocity of 10BV / h, this technical effect is unpredictable. As can also be seen from Table 1 simultaneously, the adsorption capacity of chelating resin to organophosphorus is extremely limited.

[0047] Example 2

[0048] The method and steps are the same as those in Example 1, except that in step 5), the flow rate through the tower is 10 BV / h during the adsorption of the brine by the phosphorus removal resin. The relevant data obtained are shown in Table 2.

[0049] Table 2. Phosphorus content in brine at different effluent volumes (flow rate through the tower is 10 BV / h)

[0050]

[0051] As can be seen from Table 2, when the flow rate through the tower is 10 BV / h and the effluent volume is ≤120 BV, the removal rate of organic phosphorus is ≥60%. This shows that the technical solution of the present application can be applied industrially, can achieve a maximum treatment volume of 120 BV, and has the technical effect of a large effluent volume.

[0052] Example 3

[0053] The method and steps are the same as those in Example 1, except that in step 5), the brine is sequentially adsorbed with a phosphorus removal resin. The filtrate after adsorption by the phosphorus removal resin is heated to 60° C. and the pH is maintained at 10.2. The metal ions in the brine after adsorption by the phosphorus removal resin are treated using a chelating resin tower to meet the requirements of the ion-exchange membrane caustic soda electrolysis process, and then transported to an ion-exchange membrane electrolyzer for the production of NaOH, Cl2, and H2. Simultaneously, the total phosphorus and organic phosphorus contents of the waste brine before and after nanofiltration membrane treatment at different concentration ratios were measured.

[0054] Specifically, 60 L of brine treated in step 3) was filtered through a nanofiltration membrane and subjected to concentration tests at different concentration ratios. Permeate and concentrate samples were collected when the permeate volumes reached 40 L, 45 L, 48 L, and 50 L, respectively, and the total phosphorus and organic phosphorus contents were determined. These corresponding concentration ratios were 3x, 4x, 5x, and 6x, respectively.

[0055] As can be seen from Table 3, when the concentration ratio is 4 times, the total phosphorus removal rate in the waste brine can reach 84%. When the concentration ratio is further increased, the total phosphorus removal rate of the brine gradually decreases. Considering the capital cost of recycling, 4 times the processing volume is also an excellent concentration ratio that can achieve the effect of this case.

[0056] Table 3. Total phosphorus and organic phosphorus content before and after nanofiltration membrane treatment of wastewater at different concentration ratios

[0057]

Claims

1. A method for deep impurity removal of glyphosate wastewater, characterized in that: The specific process steps are as follows: (1) filtering the glyphosate waste brine with a ceramic membrane to remove suspended solids and obtain brine; (2) filtering the brine from step (1) using a nanofiltration membrane, concentrating it 3 or 4 times to obtain a permeate; (3) The permeate is subjected to adsorption treatment with a phosphorus removal resin at a flow rate through the tower of 5 BV / h and a water outlet volume of ≤120 BV to obtain a filtrate. The preparation method of the phosphorus removal resin comprises the following steps: Step 1: Pretreatment: Weigh polystyrene-divinylbenzene polymer, wash it with NaOH and HCl, and then wash it with deionized water until it is neutral; Step 2: Post-crosslinking: The pretreated material is immersed in 1,2-dichloroethane, and after fully swelling, 1-10% by mass of ferric chloride is added and fully dissolved, and post-crosslinking is performed in a water bath to obtain a cross-linked resin; Step 3: Chemical modification: The cross-linked resin is fully immersed in a 1,2-dichloroethane solution and filtered, and a trimethylamine solution with a mass fraction of 0.1-5% of the polystyrene-divinylbenzene polymer is added to react in a water bath. After the reaction is completed, the resin is washed with water until neutral to obtain an adsorption resin; Step 4: Loading Fe(OH)3: Add the adsorption resin to the FeCl3·6H2O-HCl mixed solution for reaction, filter, and vacuum dry to obtain the Fe(OH)3-loaded phosphorus removal resin. The average pore size of the phosphorus removal resin is 5-10 nm; the pore volume is 0.02-0.10 cm 3 / g; specific surface area is 8~15 m 2 / g; (4) The filtrate is adsorbed by a chelating resin with a flow rate through the tower of 5 BV / h and a water volume of ≤120 BV, thereby completing deep phosphorus removal of the glyphosate wastewater. The chelating resin is a macroporous styrene-based ion exchange resin containing an iminodiacetic acid chelating group.

2. The deep impurity removal treatment method for glyphosate wastewater according to claim 1, characterized in that: The process parameters of glyphosate waste brine are: temperature 50~60℃, NaCl concentration 290~310 g / L, pH 6~11, Ca 2+ +Mg 2+ Content ≤2 ppm, total phosphorus 80-120ppm.

3. The deep impurity removal treatment method for glyphosate wastewater according to claim 2, characterized in that: In step (1), the glyphosate waste brine is filtered through a ceramic membrane and then Na2SO3 is added to remove free chlorine in the permeate, and the permeate is adjusted to 6.0-8.0 and the temperature is adjusted to 35-40°C.

4. The deep impurity removal treatment method for glyphosate wastewater according to claim 1, characterized in that: When performing the nanofiltration membrane in step (2), a three-stage filtration method is adopted, and the pressure entering the nanofiltration membrane is 2~3 MPa.

5. The deep impurity removal treatment method for glyphosate wastewater according to claim 4, characterized in that: After filtration in step (2), the permeate is heated to 40-60°C and the pH is adjusted to 8-10.

6. The method for deep impurity removal of glyphosate wastewater according to claim 1, wherein: The water content of the resin is 45-60% by weight.

7. The deep impurity removal treatment method for glyphosate wastewater according to claim 1, characterized in that: The filtrate after phosphorus removal resin adsorption is heated to 58-62°C and the pH is maintained at 9-11 for chelating resin adsorption.

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