A method for removing iron ions from phosphorous acid mother liquor by utilizing electric field effect

Abstract

The present invention discloses a method for removing iron ions from phosphorous acid mother liquor by electric field effect, and belongs to the technical field of phosphorous acid production. The present application innovatively introduces a direct current electric field into the phosphorous acid mother liquor, utilizes the electric field effect, enriches the iron in the solution to the negative electrode of the power supply, and more effectively improves the oxidation efficiency of hydrogen peroxide, and then adds a precipitant compounded by a plurality of compounds to the negative electrode of the electrode, which greatly improves the ability of iron removal, and the activated carbon and ion exchange resin used in addition to ensure the required integrity of the composition of the raw material, and also improves the clarity of the phosphorous acid solution. The present application method can efficiently reduce the concentration of iron ions, and provides a guarantee for the purification and production of phosphorous acid. The method for removing iron from the phosphorous acid mother liquor of the present application is simple to operate, and the phosphorous acid prepared is reduced to less than 10ppm in residual iron concentration compared with the original mother liquor.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphorous acid production, and in particular relates to a method for removing iron ions in phosphorous acid mother liquor by utilizing electric field effect. Background Art

[0002] Phosphorous acid is currently mainly used to make plastic stabilizers, and is also used in the manufacture of synthetic fibers and phosphites. It also plays an important role in wastewater treatment, agriculture, medicine and other fields. At present, there are two main methods for producing phosphorous acid: phosphorus trichloride hydrolysis method and dimethyl phosphite residual liquid hydrolysis method. Iron ions are inevitably introduced into the production process or raw materials. The level of iron ion content directly affects the quality of downstream products and even limits their application in downstream products. Therefore, reducing the iron content in phosphorous acid can effectively improve the product quality of phosphorous acid, which plays a key role in subsequent applications.

[0003] When the precipitation method is used alone, the precipitant is easily left in the phosphorous acid, which causes the chemical and physical properties of the industrially produced phosphorous acid solution to change, affecting the quality of the product. For example, Chinese patent application CN103991852A discloses a method for reducing the iron ion content in phosphorous acid, which reduces the iron ion content by reacting the iron-containing phosphorous acid mother liquor with a sodium ferram solution.

[0004] Although the ion exchange method alone can remove part of the iron in the mother liquor, the capacity of the ion exchange resin is limited, and high concentrations of iron will lead to frequent regeneration of the resin, which is too costly in terms of the efficiency of reducing the iron concentration.

[0005] Therefore, it is particularly important to develop a method for effectively reducing the concentration of iron and obtaining a clarified phosphorous acid solution. Summary of the invention

[0006] The invention aims at the problems existing in the prior art and provides a new method for removing iron ions in phosphorous acid mother liquor. The method is simple to operate, and the purified phosphorous acid mother liquor has low residual iron concentration and good purity, and is suitable for use in various fields.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0008] A method for removing iron ions in phosphorous acid mother solution by utilizing electric field effect comprises the following steps:

[0009] (1) placing the phosphorous acid mother solution to be purified in a container, inserting positive and negative electrodes to form an electric field, applying power for a certain period of time, adding hydrogen peroxide to the negative electrode area of ​​the electrode, and allowing to stand;

[0010] (2) After the standing still, add the precipitant A21 and the precipitant B37 to the negative electrode area. After the addition is completed, remove the electrode, continue to stir the reaction at room temperature, and then stand still. After the standing still is completed, a treated solution is obtained;

[0011] (3) vacuum filtering the treated liquid to preliminarily remove the precipitated substances;

[0012] (4) adding activated carbon to the filtrate after vacuum filtration, stirring continuously and then allowing to stand, filtering out the activated carbon with gauze after the standing period, and subjecting the filtrate after filtration through the gauze to high-speed centrifugation;

[0013] (5) The filtrate obtained by centrifugation is further purified using an ion exchange resin to obtain a purified phosphorous acid mother liquor.

[0014] Preferably, step (1) further comprises a pretreatment step before inserting the electrode, wherein the pretreatment is to add an adsorbent to the phosphorous acid mother liquor to be purified for preliminary adsorption and impurity removal, wherein the adsorbent is one or more of zeolite, activated carbon, and diatomaceous earth, and the amount of the adsorbent added is 1-5% of the mass of the phosphorous acid mother liquor.

[0015] Preferably, the electrodes in step (1) are DC electrodes, which are connected to DC power to form a DC electric field, with a distance between the positive and negative electrodes of 5-50 cm, a power-on time of 10-100 min, and a voltage of 10-100 V.

[0016] Preferably, in step (1), the mass ratio of hydrogen peroxide to the phosphorous acid mother liquor to be purified is 1:(50-200), and the standing time is 10-30 min.

[0017] Preferably, in step (2), the mass ratio of the precipitant A21 to the phosphite mother liquor to be purified is 1:(50-100), and the precipitant A21 is one or more of potassium ferrocyanide, HEDP (hydroxyethylidene diphosphonic acid), sodium ferram, and chromous nitrate hexahydrate; the mass ratio of the precipitant B37 to the phosphite mother liquor to be purified is 1:(200-800), and the precipitant B37 is one or more of potassium ferrocyanide, chromate, EDTA (ethylenediaminetetraacetic acid), and hydroxylamine; and intermittent stirring is performed during the addition of the precipitant to the negative electrode region.

[0018] Preferably, the continuous stirring reaction time in step (2) at room temperature is 4-10 hours, and the standing time is 2-6 hours.

[0019] Preferably, the vacuum filtration pressure in step (3) is 0.1-0.8 MPa, and the filtration time is controlled to be 0.5-4 h.

[0020] Preferably, in step (4), the solid-liquid ratio of activated carbon to the phosphorous acid mother liquor to be purified is 1 g:200 mL, the continuous stirring time is 2-6 h, and the standing time is 4-15 h; the speed of centrifugal separation is controlled at 3500-5000 r / min, and the centrifugation time is 20-100 min.

[0021] Preferably, when the filtrate obtained by centrifugation in step (5) is further purified using an ion exchange resin, the outflow rate of the chromatography column is controlled to be 1 drop per 3-5 seconds.

[0022] Beneficial effects:

[0023] The invention introduces a direct current electric field into the phosphorous acid mother liquor in an innovative way, and utilizes the electric field effect to enrich the iron in the solution to the negative electrode of the power supply, thereby more effectively improving the oxidation efficiency of hydrogen peroxide, and then adding a precipitant compounded by a variety of compounds to the negative electrode of the electrode, greatly improving the ability of iron removal, and the activated carbon and ion exchange resin used in the additional use, on the basis of ensuring the required integrity of the composition of the raw material, also improve the clarity of the phosphorous acid solution. The phosphorous acid mother liquor iron removal method utilizing the electric field effect of the invention can efficiently reduce the iron ion concentration, and provides a guarantee for the purification and production of phosphorous acid. The phosphorous acid mother liquor iron removal method of the invention is adopted, and the operation is simple, and the phosphorous acid prepared is compared with the original mother liquor, and the residual iron concentration is reduced to less than 10ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart of the method for removing iron ions from phosphorous acid mother liquor;

[0025] Figure 2 The electric field schematic diagram of the method for removing iron ions in phosphorous acid mother liquor by utilizing electric field effect of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0027] Example 1

[0028] 100mL of phosphorous acid mother liquor with an iron content of 535ppm was added to the reaction container, two electrodes 8cm apart were placed, and a 20V direct current was connected for 25min. 1.5mL of hydrogen peroxide was added to the negative electrode area of ​​the electrode, and the mixture was allowed to stand for 10min. Then, 0.7g of B37 (potassium ferrocyanide) and 2.5g of A21 (potassium ferrocyanide) were added to the negative electrode area, and the mixture was stirred intermittently with a glass rod. The electrodes were removed, and a magnetic rod was placed and stirred. The reaction temperature was room temperature. After reacting for 4 hours, the mixture was allowed to stand for 2 hours, and then vacuum filtered at 0.1MPa for 0.5h, the filtrate was collected, 0.5g of activated carbon was added, and the mixture was stirred for 2h. After the stirring was completed, the mixture was allowed to stand for 4h. After the standing was completed, the mixture was filtered, and the mixture was centrifuged at 3500r / min for 20min. The filtrate was collected and added to a chromatography column filled with ion exchange resin. The outflow rate of the chromatography column was controlled to be 1 drop per 3 seconds. After the column was completed, the filtrate was collected and the filtrate was clear and transparent. The iron ion concentration was tested according to the method specified in GB / T22596-2008, and the iron content was 7.1 ppm. The following examples all refer to this national standard method.

[0029] The filtrate is concentrated, cooled, and crystallized to obtain white solid phosphorous acid. The content of phosphorous acid is determined by the following test method: 1g of phosphorous acid is weighed, added to a 50mL conical flask, dissolved with 80mL of distilled water, and then 3 drops of thymolphthalein reagent are added. The solution is titrated with NaOH until the light blue color is the end point, and the phosphorous acid content is calculated. After testing, the phosphorous acid content of this embodiment is 99.55%, the phosphorous acid purity is high, and the impurity components are less. The following embodiments all adopt this method to detect the phosphorous acid content.

[0030] Example 2

[0031] 1500mL of phosphorous acid mother liquor with an iron content of 700ppm was added to the reaction vessel, two electrodes 30cm apart were placed, 50V direct current was connected, and the electricity was turned on for 40min. 9mL of hydrogen peroxide was added to the negative electrode region of the electrode, and it was allowed to stand for 15min. Then 5g of B37 (sodium chromate) and 50g of A21 (HEDP) were added to the negative electrode region, and glass rods were used for stirring intermittently. The electrodes were removed, and the magnetic son was placed and stirred. The reaction temperature was normal temperature. After reacting for 8 hours, it was allowed to stand for 4 hours, and then 0.5MPa vacuum filtration was performed for 2h, and the filtrate was collected. 7.5g of activated carbon was added, and stirring was continued for 4h. After stirring, it was allowed to stand for 12h, and after standing, it was filtered, and then centrifuged at high speed for 60min, and the filtrate was collected, and it was added to the chromatography column filled with ion exchange resin. The speed of controlling the outflow of the chromatography column was 1 drop per 3 seconds. After the column was finished, the filtrate was collected, and the filtrate was clear and transparent, and the iron content was 7.8ppm. After testing, the phosphorous acid content of the present embodiment was 99.50%.

[0032] Example 3

[0033] 3500mL of phosphorous acid mother liquor with an iron content of 850ppm was added to a reaction container, two electrodes 50cm apart were placed, a 100V direct current was connected, and the power was turned on for 60min. 35mL of hydrogen peroxide was added to the negative electrode area of ​​the electrode, and the mixture was allowed to stand for 30min. Then, 8g of B37 (EDTA) and 72g of A21 (sodium fumei) were added to the negative electrode area, and the mixture was stirred intermittently with a glass rod. The electrodes were removed, and a magnetic bar was placed and stirred. The reaction temperature was room temperature. After reacting for 10 hours, the mixture was allowed to stand for 6 hours, and then vacuum filtered at 0.6MPa for 3h, the filtrate was collected, 17.5g of activated carbon was added, and the mixture was stirred for 6h. After the stirring was completed, the mixture was allowed to stand for 15h. After the standing was completed, the mixture was filtered, and then centrifuged at high speed for 100min. The filtrate was collected and added to a chromatography column filled with ion exchange resin. The outflow rate of the chromatography column was controlled to be 1 drop per 3 seconds. After the column was completed, the filtrate was collected. The filtrate was clear and transparent, and the iron content was measured to be 6.8ppm. After testing, the phosphorous acid content of this embodiment is 99.62%.

[0034] Example 4

[0035] 500 mL of phosphorous acid mother liquor with an iron content of 900 ppm was added to a reaction container, and zeolite with a mass percentage of 5% of the phosphorous acid mother liquor was added for pretreatment adsorption. After standing for 30 minutes, the pretreatment was completed, and the pretreatment mother liquor was filtered to remove the zeolite. Two electrodes 5 cm apart were placed in the pretreated mother liquor, connected to a 10V direct current, powered on for 100 minutes, 11.2mL of hydrogen peroxide was added to the negative electrode region of the electrode, allowed to stand for 20 minutes, and then 4.125g of B37 (hydroxylamine) and 16.5g of A21 (chromous nitrate hexahydrate) were added to the negative electrode region, intermittently stirred with a glass rod, the electrodes were removed, and a magnetic bar was placed and stirred. The reaction temperature was room temperature. After reacting for 7 hours, it was allowed to stand for 4 hours, and then vacuum filtered at 0.5MPa for 2 hours, the filtrate was collected, 2.5g of activated carbon was added, and stirring was continued for 2 hours. After the stirring ended, it was allowed to stand for 4 hours. After the standing ended, it was filtered, and then centrifuged at 4000r / min for 100 minutes. The filtrate was collected and added to a chromatography column filled with ion exchange resin. The outflow rate of the chromatography column was controlled to be 1 drop per 4 seconds. After the column was passed, the filtrate was collected. The filtrate was clear and transparent, and the iron content was measured to be 6.9ppm. After testing, the phosphorous acid content of this embodiment is 99.60%.

[0036] Example 5

[0037] 800mL of phosphorous acid mother liquor with an iron content of 800ppm was added to the reaction container, two electrodes were placed 10cm apart, and a 90V direct current was connected. The power was turned on for 10min, 4.5mL of hydrogen peroxide was added to the negative electrode area of ​​the electrode, and it was allowed to stand for 15min. Then, 1.65g of B37 (EDTA) and 13.2g of A21 (potassium ferrocyanide) were added to the negative electrode area, and stirred with a glass rod intermittently. The electrodes were removed, and a magnetic rod was placed and stirred. The reaction temperature was room temperature. After reacting for 8 hours, it was allowed to stand for 5 hours. The mixture was then vacuum filtered at 0.8 MPa for 4 hours, the filtrate was collected, 4 g of activated carbon was added, and stirring was continued for 2 hours. After the stirring was completed, the mixture was allowed to stand for 4 hours. After the standing was completed, the mixture was filtered, and then high-speed centrifugation was performed at 5000 r / min for 30 minutes. The filtrate was collected and added to a chromatography column filled with ion exchange resin. The outflow rate of the chromatography column was controlled to be 1 drop per 5 seconds. After the column was completed, the filtrate was collected. The filtrate was clear and transparent, and the iron content was measured to be 7.3 ppm. After testing, the phosphorous acid content in this embodiment was 99.52%.

[0038] Comparative Example 1

[0039] Purification is performed according to a conventional method without introducing an electric field, that is, purification is performed according to the method of Example 5 without introducing an electric field.

[0040] 800mL of phosphorous acid mother liquor with an iron content of 800ppm was added into a reaction container, and 1.65g of B37 (EDTA) and 13.2g of A21 (potassium ferrocyanide) were added. The mixture was stirred after a magnetic bar was placed in the reaction vessel. The reaction temperature was room temperature. After the reaction for 8 hours, the mixture was allowed to stand for 5 hours, and then vacuum filtered at 0.8MPa for 4 hours. The filtrate was collected, 4g of activated carbon was added, and the mixture was continued to be stirred for 2 hours. After the stirring was completed, the mixture was allowed to stand for 4 hours. After the standing was completed, the mixture was filtered, and the mixture was centrifuged at 5000r / min for 30 minutes. The filtrate was collected and added to a chromatography column filled with ion exchange resin. The outflow rate of the chromatography column was controlled to be 1 drop per 5 seconds. After the column was completed, the filtrate was collected. The filtrate was clear and transparent, and the iron content was measured to be 45.6ppm. After testing, the phosphorous acid content of this comparative example was 99.10%.

[0041] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A method for removing iron ions from phosphorous acid mother liquor by utilizing electric field effect, characterized in that: The following steps are involved: (1) placing the phosphorous acid mother liquid to be purified in a container, inserting positive and negative electrodes to form an electric field, applying power for a certain period of time, adding hydrogen peroxide to the negative electrode area of ​​the electrode, and allowing to stand; (2) After the standing still, add the precipitant A21 and the precipitant B37 to the negative electrode area. After the addition is completed, remove the electrode, continue to stir the reaction at room temperature, and then stand still. After the standing still is completed, a treated solution is obtained; (3) vacuum filtering the treated liquid to preliminarily remove the precipitated substances; (4) adding activated carbon to the filtrate after vacuum filtration, stirring continuously and then allowing to stand, filtering out the activated carbon with gauze after the standing period, and subjecting the filtrate after filtration through the gauze to high-speed centrifugation; (5) further purifying the filtrate obtained by centrifugation using an ion exchange resin to obtain a purified phosphorous acid mother liquor; Step (1) The electrodes are DC electrodes, connected to DC to form a DC electric field, the distance between the positive and negative electrodes is 5-50 cm, the power-on time is 10-100 min, and the voltage is 10-100 V; In step (2), the mass ratio of the precipitant A21 to the phosphorous acid mother liquor to be purified is 1:(50-100), and the precipitant A21 is one or more of potassium ferrocyanide, hydroxyethylidene diphosphonic acid, sodium ferram, and chromous nitrate hexahydrate; the mass ratio of the precipitant B37 to the phosphorous acid mother liquor to be purified is 1:(200-800), and the precipitant B37 is one or more of potassium ferrocyanide, chromate, ethylenediaminetetraacetic acid, and hydroxylamine; and intermittent stirring is performed during the process of adding the precipitant to the negative electrode region.

2. The method for removing iron ions from phosphorous acid mother liquor by electric field effect according to claim 1, characterized in that: Step (1) also includes a pretreatment step before inserting the electrode. The pretreatment is to add an adsorbent to the phosphorous acid mother liquor to be purified for preliminary adsorption and impurity removal. The adsorbent is one or more of zeolite, activated carbon, and diatomaceous earth. The amount of adsorbent added is 1-5% of the mass of the phosphorous acid mother liquor.

3. The method for removing iron ions in phosphorous acid mother liquor by electric field effect according to claim 1, characterized in that: In step (1), the mass ratio of hydrogen peroxide to the phosphorous acid mother liquor to be purified is 1:(50-200), and the standing time is 10-30 minutes.

4. The method for removing iron ions from phosphorous acid mother liquor by utilizing electric field effect according to claim 1, characterized in that: In step (2), the reaction time under continuous stirring at room temperature is 4-10 hours, and the standing time is 2-6 hours.

5. The method for removing iron ions from phosphorous acid mother solution by utilizing electric field effect according to claim 1, characterized in that: The vacuum filtration pressure in step (3) is 0.1-0.8 MPa, and the filtration time is controlled to be 0.5-4 h.

6. The method for removing iron ions from phosphorous acid mother solution by utilizing electric field effect according to claim 1, characterized in that: In step (4), the solid-liquid ratio of activated carbon to the phosphorous acid mother liquor to be purified is 1 g: 200 mL, the continuous stirring time is 2-6 h, and the standing time is 4-15 h; the speed of centrifugal separation is controlled at 3500-5000 r / min, and the centrifugation time is 20-100 min.

7. The method for removing iron ions from phosphorous acid mother solution by utilizing electric field effect according to claim 1, characterized in that: When the filtrate obtained by centrifugation in step (5) is further purified using an ion exchange resin, the outflow rate of the chromatography column is controlled to be 1 drop per 3-5 seconds.

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