CN101538216B - Method for desalting acidified mother solution of iminodiacetic acid using nanofiltration technology - Google Patents

Abstract

The invention belongs to the technical field of desalination of chemical products, and relates to a method for desalting iminodiacetic acid acidified mother liquor by applying nanofiltration technology. First, adjust the pH value of the iminodiacetic acid acidified mother liquor in the reaction system to 3-11 with an inorganic base, and then use a microfiltration membrane module or an ultrafiltration membrane module to treat iminodiacetic acid with a pH value between 3 and 11. Acetic acid acidified mother liquor is subjected to microfiltration pretreatment or ultrafiltration pretreatment; then nanofiltration membrane module is used to perform nanofiltration desalination operation on the permeated liquid after microfiltration pretreatment or ultrafiltration pretreatment, iminodiacetic acid is intercepted, and a large amount of Sodium chloride is continuously discharged with the permeate. The desalted iminodiacetic acid mother liquor will be returned to the acidification pool for recycling. The invention not only has the advantages of simple operation, energy saving and emission reduction, and is easy for continuous production, but also can achieve the purposes of desalination and concentration at the same time, and the recovery rate of iminodiacetic acid in the iminodiacetic acid mother liquor is greater than 95%.

Description

Method for desalting iminodiacetic acid acidified mother liquor by applying nanofiltration technology

field of invention

The invention belongs to the technical field of desalination of chemical products, and relates to a method for desalting iminodiacetic acid acidified mother liquor by applying nanofiltration technology.

Background technique

Iminodiacetic acid is a widely used organic chemical raw material, and its largest consumption is the production of herbicide glyphosate. Since iminodiacetic acid is a chelating agent with good performance, it can form chelates with various metal ions. It is also used in rubber, surfactants, food additives, anticancer drugs, electroplating industry, metal surface treatment materials and ion exchange. Important raw materials and intermediates for products such as resins. The production methods of iminodiacetic acid include chloroacetic acid method, hydrocyanic acid method, diethanolamine catalytic dehydrogenation method, etc. Most of the methods are to generate iminodiacetic acid sodium salt first, and then acidify with concentrated hydrochloric acid in the acidification tank to adjust When the pH value is slightly lower than the isoelectric point of iminodiacetic acid, the crystallization is separated, and the product is obtained after drying. But at the same time, a large amount of iminodiacetic acid acidified mother liquor containing 80-140 g/L of salt will be produced, and the mass fraction of iminodiacetic acid in the mother liquor is 25-60 g/L. In order to recover this part of iminodiacetic acid, the mother liquor can be recycled, but sodium chloride will continue to accumulate in it, and the existence of a large amount of sodium chloride will affect the crystallization of iminodiacetic acid, resulting in a decrease in its yield and a large amount of waste water . In order to improve the yield of iminodiacetic acid, it is not only necessary to reclaim the iminodiacetic acid in the mother liquor, but also to remove the salt in the mother liquor.

The traditional method of desalting iminodiacetic acid acidified mother liquor is to use the different solubility of iminodiacetic acid and sodium chloride to separate the salt in the mother liquor by evaporation, concentration and crystallization, but this method consumes too much energy. In recent years, Zeng Xiaojun and others from the Institute of Applied Chemistry of Changshu College in China have begun to study the use of electrodialysis technology to desalt the mother liquor. However, due to the constant change of the pH of the feed solution during the electrodialysis process, it is difficult to keep it at the isoelectric point in actual operation. It is easy to cause a large amount of loss of iminodiacetic acid, and the cost of this method is relatively high. CN 1663945A discloses adding calcium salt in iminodiacetic acid acidification mother liquor, complex reaction occurs with iminodiacetic acid, forms complex precipitation, realizes the method for separating with sodium chloride, but this method process is complicated, for pH Value, temperature control requirements are high.

Nanofiltration is a new membrane separation technology between reverse osmosis and ultrafiltration. The application advantages of nanofiltration technology in solution desalination mainly include the following two aspects: (1) There is no phase change in the separation process, no heating is required, and the operation is simple , energy saving, easy to scale up and integrate with other separation technologies; (2) Most nanofiltration membranes are charged membranes, and their separation mechanism depends on the electrostatic interaction between the solute and the membrane surface in addition to the sieving effect, which is especially suitable for The separation of charged substances has good effects in the desalination, concentration and purification of sugars, dyes, amino acids and other small molecular substances. Therefore, the present invention proposes to apply nanofiltration technology to desalination of iminodiacetic acid acidified mother liquor, which not only saves energy and reduces emissions, but also improves the yield of iminodiacetic acid. There are no similar reports at home and abroad.

Contents of the invention

The object of the present invention is to provide a kind of method that applies nanofiltration technology to carry out the desalination of iminodiacetic acid acidified mother liquor, and this method can not only remove most of salt in mother liquor, can also improve wherein iminodiacetic acid concentration. The method has the advantages of simple process, energy saving and emission reduction.

The method for desalting the iminodiacetic acid acidified mother liquor using nanofiltration technology of the present invention is to utilize the nanofiltration membrane separation technology to realize the separation of iminodiacetic acid and sodium chloride, reduce the content of sodium chloride in the iminodiacetic acid mother liquor, Realize the recycling of mother liquor. The method is: first adjust the pH value of the iminodiacetic acid acidified mother liquor (pH about 1.96) in the feed liquid tank in the reaction system to between 3 and 11 with an inorganic base, and then use a microfiltration membrane module or ultrafiltration to Membrane module is used to perform microfiltration pretreatment or ultrafiltration pretreatment on iminodiacetic acid acidified mother liquor with a pH value between 3 and 11; The permeate is subjected to nanofiltration desalination operation, iminodiacetic acid is intercepted, and a large amount of sodium chloride is continuously discharged with the permeate. The desalted iminodiacetic acid mother liquor will be returned to the acidification pool for recycling.

Described inorganic base is sodium hydroxide or potassium hydroxide.

The pore size of the microfiltration membrane module used in the microfiltration pretreatment is 0.1-0.45 microns. The material of the microfiltration membrane module is organic polymer materials such as mixed cellulose, polyamide, polyethersulfone or polyvinylidene fluoride.

The molecular weight cut-off of the ultrafiltration membrane module used in the ultrafiltration pretreatment is not less than 100,000 Daltons (Da). The material of the ultrafiltration membrane module is an organic polymer material such as cellulose acetate, polysulfone, polysulfone amide or polyvinylidene fluoride.

The nanofiltration membrane module used in the nanofiltration desalination operation has a molecular weight cut-off of 100 to 500 Da, and the nanofiltration membrane module can be a roll type, a tube type or a flat plate type, and the material of the nanofiltration membrane module can be cellulose acetate, sulfur Polysulfone, polyamide, polyethersulfone, sulfonated polyethersulfone, polypiperazine or polyvinyl alcohol organic polymer materials.

Said nanofiltration desalination operation mode includes diafiltration mode, concentration mode, combination of concentration-diafiltration or combination of diafiltration-concentration.

The diafiltration method in the nanofiltration desalination operation is that when the permeate obtained after the pretreatment of the microfiltration membrane module or ultrafiltration membrane module passes through the nanofiltration membrane module, it is continuously sent to the microfiltration membrane module or ultrafiltration membrane module. Add water to the permeate obtained after the pretreatment of the membrane module, and control the water addition rate to be equal to the permeation flux of the nanofiltration membrane module until the water consumption is equal to the permeate obtained after pretreatment of the microfiltration membrane module or ultrafiltration membrane module. Stop adding water when 1/3 to 4/3 of the liquid volume has passed.

The concentration method in the nanofiltration desalination operation is to pass the permeate obtained after the pretreatment of the microfiltration membrane module or the ultrafiltration membrane module directly through the nanofiltration membrane module until the volume of the retentate is concentrated to the original microfiltration volume. Stop operation when the permeate volume obtained after pretreatment of the membrane module or ultrafiltration membrane module is 1/4 to 2/3.

The temperature range of the reaction system is 10-50°C, preferably 25°C.

The pressure range in the nanofiltration desalination operation is 0.5Mpa-4.0Mpa, preferably the pressure is 1.5Mpa-3.0Mpa.

The pressure in the microfiltration pretreatment is preferably 0.1-0.2Mpa.

The pressure in the ultrafiltration pretreatment is preferably 0.2-1.0 Mpa.

The method for desalting iminodiacetic acid acidified mother liquor by using nanofiltration technology provided by the present invention has the following prominent features and advantages:

1. Simple operation process, energy saving and emission reduction, and easy continuous production.

2. It can not only remove most of the salt in the mother liquor, but also increase the concentration of iminodiacetic acid in it, realize the recycling of mother liquor, improve the yield of iminodiacetic acid, and the recovery rate of iminodiacetic acid in the mother liquor of iminodiacetic acid is greater than 95%.

3. The permeate can be recycled as chlor-alkali water after further treatment.

Description of drawings

Figure 1. Schematic diagram of the process flow for desalination of iminodiacetic acid acidified mother liquor using nanofiltration technology.

reference sign

1. Acidification tank 2. Feed valve 3. Feed tank 4. Feed valve 5. Feed pump

6. Microfiltration or ultrafiltration membrane module 7. Return valve 8. Feed tank 9. Feed valve

10. Feed pump 11. Nanofiltration membrane module 12. Return valve 13. Return pump

Detailed ways

The present invention will be further described below in conjunction with the embodiments, and the protection scope of the subject matter involved in the present invention is not limited to these embodiments.

Example 1

The device shown in Figure 1 can be used as a device for desalting iminodiacetic acid acidified mother liquor using nanofiltration technology. Including acidification tank 1, feed valve 2, feed liquid tank 3, feed valve 4, feed pump 5, microfiltration membrane module 6, return valve 7, feed liquid tank 8, feed valve 9, feed pump 10, The nanofiltration membrane module 11, the return valve 12, and the return pump 13; the nanofiltration desalination process adopts the percolation method.

An acidification tank 1 is communicated with the feed port of the feed liquid tank 3 through a pipeline with a feed valve 2, and the discharge port of the feed liquid tank 3 is connected with the feed pump 5 through a pipeline with a feed valve 4. The feed port is connected, and the discharge port of the feed pump 5 is connected with the feed port of the microfiltration membrane module 6 through a pipeline, and the retained liquid discharge port at one end of the feed port in the microfiltration membrane module 6 passes through a The pipeline of the valve 7 is connected with another feed port of the feed liquid tank 3, and the feed port of the permeate of the microfiltration membrane module 6 is connected with the feed liquid tank 8 through the pipeline, and one outlet of the feed liquid tank 8 The feed port is connected to the feed port of the acidification tank 1 through a pipeline with a return pump 13, and the other discharge port of the feed liquid tank 8 is connected to the feed pump 10 through a pipeline with a feed valve 9. The feed port is connected, and the discharge port of the feed pump 10 is connected with the feed port of the nanofiltration membrane module 11 through a pipeline, and the retentate discharge port at one end of the feed port in the nanofiltration membrane module 11 passes through a The pipeline of 12 is communicated with another feeding port of feed liquid groove 8.

First, put iminodiacetic acid acidified mother liquor (containing iminodiacetic acid about 30g/L, salt content about 80g/L, pH≈1.96) from acidification tank 1 into feed liquid tank 3, and adjust mother liquor with sodium hydroxide pH value to 5.2, then at normal temperature (25°C) and pressure 0.1-0.2Mpa, the mother liquor passes through the microfiltration membrane module 6 with a pore size of about 0.45μm and enters the feed liquid tank 8, and the permeate is 66.37Lm ^-2 The membrane flux of .h ^-1 passes through the flat polyamide nanofiltration membrane module 11 with a molecular weight cut off (MWCO) of about 150Da. In the liquid feed tank 8, control the water addition rate to be equal to the permeation flux of the nanofiltration membrane, stop adding water until the water consumption is equal to the permeate volume obtained after the pretreatment of the microfiltration membrane module, and turn off the feed pump 10 and feed valve 9; the operating pressure in the process is about 2.0Mpa ~ 3.0Mpa. The content of iminodiacetic acid in the mother liquor obtained at this time is about 28.7g/L, the salt content is reduced to 31.5g/L, the loss rate of iminodiacetic acid is about 4.33%, and the desalination rate is about 60.63%. Turn on the return pump 13 to return the desalted mother liquor to the acidification tank 1 for recycling.

Example 2

Using the device in Example 1, the nanofiltration desalination process adopts a concentration method.

The microfiltration operation and conditions of the iminodiacetic acid acidified mother liquor are the same as in Example 1, and the permeate passes through the flat polyamide nanofiltration with a molecular weight cut-off (MWCO) of about 150Da at a membrane flux of 66.37Lm ^- 2.h ^-1 Membrane module 11, until the retentate volume in the feed liquid tank 8 is concentrated to 1/2 of the permeate volume obtained after the pretreatment of the microfiltration membrane module, the operation is stopped, the feed pump 10 and the feed valve 9 are closed, and the process Medium operating pressure is about 2.5 ~ 3.8Mpa. The content of iminodiacetic acid in the mother liquor obtained at this moment is about 58.1g/L, and the salt content becomes 80.8g/L (the desalination rate is calculated by mass, and the quality is related to concentration and volume, and the desalination rate=(80g/L× x-80.8g/L×y)/80g/L×x, where y=x/2, x is the permeate volume obtained after the pretreatment of the microfiltration membrane module; although the concentration of salt has increased, but The concentration of iminodiacetic acid increases more, and this example does not consume water), the loss rate of iminodiacetic acid is about 3.17%, and the desalination rate is about 49.5%. Turn on the return pump 13 to return the desalted mother liquor to the acidification tank 1 for recycling.

Example 3

Using the device of Example 1, the nanofiltration desalination process adopts a combination of concentration and diafiltration.

The microfiltration operation and conditions of the iminodiacetic acid acidified mother liquor are the same as in Example 1, and the permeate passes through the flat polyamide nanofiltration with a molecular weight cut-off (MWCO) of about 150Da at a membrane flux of 66.37Lm ^- 2.h ^-1 Membrane module 11, until the volume of the retained liquid in the feed liquid tank 8 is concentrated to 2/3 of the volume of the permeate obtained after the pretreatment of the microfiltration membrane module, start adding deionized water to the feed liquid tank 8, and control the addition of water The rate is equal to the permeation flux of the nanofiltration membrane, until the water consumption is equal to 1/2 of the volume of the retained liquid in the feed liquid tank 8, the operation is stopped, the feed pump 10 and the feed valve 9 are closed, and the operating pressure in the process is about 2.5～3.0Mpa. The content of iminodiacetic acid in the mother liquor obtained at this moment is about 43.1g/L, and the salt content drops to 49.9g/L (in embodiment 1, the water equal to the volume of feed liquid is consumed, but this embodiment only consumes 1/3 volume water, which saves water in this way), the loss rate of iminodiacetic acid is about 4.22%, and the desalination rate is about 58.42%. Turn on the return pump 13 to return the desalted mother liquor to the acidification tank 1 for recycling.

Example 4

Using the device of Example 1, the nanofiltration desalination process adopts a combination of diafiltration and concentration.

The microfiltration operation and conditions of the iminodiacetic acid acidified mother liquor are the same as in Example 1, and the permeate passes through the flat polyamide nanofiltration with a molecular weight cut-off (MWCO) of about 150Da at a membrane flux of 66.37Lm ^- 2.h ^-1 Membrane module 11, at the same time, deionized water is continuously added to the feed liquid tank 8 containing the permeated liquid obtained after the pretreatment of the microfiltration membrane module, and the rate of water addition is controlled to be equal to the permeation flux of the nanofiltration membrane module. Stop adding water until the water consumption is equal to 1/3 of the volume of the permeate obtained after the pretreatment of the microfiltration membrane module, and then perform the nanofiltration desalination operation in a concentrated manner until the volume of the retained liquid in the feed liquid tank 8 is concentrated to the original microfiltration volume. Stop operation when the permeate volume obtained after the pretreatment of the membrane module is 2/3, close the feed pump 10 and the feed valve 9, and the operating pressure during the process is about 2.2-2.8Mpa. The iminodiacetic acid content is about 43.3g/L in the mother liquor that obtains now, and salt content drops to 58.7g/L, (operation process pressure will be smaller than embodiment 3, energy consumption is little) iminodiacetic acid loss rate is about 3.78%, and the desalination rate is about 51.08%. Turn on the return pump 13 to return the desalted mother liquor to the acidification tank 1 for recycling.

Example 5

The device shown in Figure 1 can be used as a device for desalting iminodiacetic acid acidified mother liquor using nanofiltration technology. Including acidification tank 1, feed valve 2, feed liquid tank 3, feed valve 4, feed pump 5, ultrafiltration membrane module 6, return valve 7, feed liquid tank 8, feed valve 9, feed pump 10, The nanofiltration membrane module 11, the return valve 12, and the return pump 13; the nanofiltration desalination process adopts the percolation method.

An acidification tank 1 is communicated with the feed port of the feed liquid tank 3 through a pipeline with a feed valve 2, and the discharge port of the feed liquid tank 3 is connected with the feed pump 5 through a pipeline with a feed valve 4. The feed port is connected, and the discharge port of the feed pump 5 is connected with the feed port of the ultrafiltration membrane module 6 through a pipeline, and the retentate discharge port at one end of the feed port in the ultrafiltration membrane module 6 passes through a The pipeline of the valve 7 is connected with another feed port of the feed liquid tank 3, and the feed port of the permeate of the ultrafiltration membrane module 6 is connected with the feed liquid tank 8 through the pipeline, and one outlet of the feed liquid tank 8 The feed port is connected to the feed port of the acidification tank 1 through a pipeline with a return pump 13, and the other discharge port of the feed liquid tank 8 is connected to the feed pump 10 through a pipeline with a feed valve 9. The feed port is connected, and the discharge port of the feed pump 10 is connected with the feed port of the nanofiltration membrane module 11 through a pipeline, and the retentate discharge port at one end of the feed port in the nanofiltration membrane module 11 passes through a The pipeline of 12 is communicated with another feeding port of feed liquid groove 8.

First, put iminodiacetic acid acidification mother liquor (containing iminodiacetic acid about 30g/L, salt content about 80g/L, pH≈1.96) from acidification tank 1 into feed liquid tank 3, and adjust the mother liquor with potassium hydroxide pH value to 10, and then at normal temperature (25°C) and pressure of 0.2 to 1.0Mpa, the mother liquor passes through the ultrafiltration membrane module 6 with a molecular weight cut off (MWCO) of about 100,000Da and enters the feed liquid tank 8, and the permeate is 66.37 The membrane flux of Lm ^-2 .h ^-1 passes through the roll-type sulfonated polyethersulfone nanofiltration membrane module 11 with a molecular weight cut-off (MWCO) of about 250Da. At the same time, deionized water is continuously added to the ultrafiltration membrane module In the feed liquid tank 8 of the permeated liquid obtained after pretreatment, the rate of water addition is controlled to be equal to the permeated membrane flux of the nanofiltration membrane module until the water consumption is equal to the volume of permeated liquid obtained after the pretreatment of the ultrafiltration membrane module Stop adding water, close feed pump 10 and feed valve 9; the operating pressure is about 1.9Mpa～2.9Mpa in the process. The content of iminodiacetic acid in the mother liquor obtained at this time is about 28.5g/L, the salt content is reduced to 31.4g/L, the loss rate of iminodiacetic acid is about 5.00%, and the desalination rate is about 60.75%. Turn on the return pump 13 to return the desalted mother liquor to the acidification tank 1 for recycling.

Claims (10)

1. method that using nanofiltration technology carries out the desalination of acidified mother solution of iminodiacetic acid; It is characterized in that: at first the pH value with acidified mother solution of iminodiacetic acid in the reaction system transfers between 3～11 with mineral alkali; Then with micro-filtration membrane module or hyperfiltration membrane assembly, be that acidified mother solution of iminodiacetic acid between 3～11 carries out micro-filtration pre-treatment or ultrafiltration pretreatment to the pH value; And then the liquid that sees through through micro-filtration pre-treatment or ultrafiltration pretreatment is carried out nanofiltration desalination operation with nanofiltration membrane component, and iminodiethanoic acid is trapped, and sodium-chlor is constantly discharged with seeing through liquid.

2. method according to claim 1 is characterized in that: the aperture of the micro-filtration membrane module that described micro-filtration pre-treatment is used is 0.1～0.45 micron.

3. method according to claim 1 is characterized in that: the molecular weight cut-off of the hyperfiltration membrane assembly that described ultrafiltration pretreatment is used is not less than 100000 dalton.

4. method according to claim 1 is characterized in that: the mode of described nanofiltration desalination operation is diafiltration mode, concentrated mode or diafiltration-concentrated mode that combines.

5. method according to claim 4; It is characterized in that: the diafiltration mode in the described nanofiltration desalination operation; When being seeing through liquid and seeing through nanofiltration membrane component of after micro-filtration membrane module or hyperfiltration membrane assembly pre-treatment, to obtain; Constantly add water through in the liquid to what after micro-filtration membrane module or hyperfiltration membrane assembly pre-treatment, obtain; Control adds water speed and equates with the membrane flux that sees through of nanofiltration membrane component, and the liquid that sees through that equals after micro-filtration membrane module or hyperfiltration membrane assembly pre-treatment, to obtain until water loss stopped to add water at long-pending 1/3～4/3 o'clock.

6. method according to claim 4; It is characterized in that: the concentrated mode in the described nanofiltration desalination operation; Be that the liquid that sees through that will after micro-filtration membrane module or hyperfiltration membrane assembly pre-treatment, obtain directly sees through nanofiltration membrane component, until the trapped fluid volume be concentrated into former after micro-filtration membrane module or hyperfiltration membrane assembly pre-treatment, obtain see through the long-pending shut-down operation in 1/4～2/3 o'clock of liquid.

7. according to claim 1,4,5 or 6 described methods, it is characterized in that: the pressure range in the described nanofiltration desalination operation is 0.5Mpa～4.0Mpa.

8. according to claim 1,4,5 or 6 described methods, it is characterized in that: the molecular weight cut-off of used nanofiltration membrane component is 100～500Da in the described nanofiltration desalination operation.

9. method according to claim 8 is characterized in that: described nanofiltration membrane component is rolling, tubular type or flat, and the material of nanofiltration membrane component is FM, SPSF, polymeric amide, polyethersulfone, sulfonated polyether sulfone, gathers piperazine or Z 150PH.

10. method according to claim 1 is characterized in that: the pressure in the described micro-filtration pre-treatment is 0.1～0.2Mpa; Pressure in the described ultrafiltration pretreatment is 0.2～1.0Mpa.

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