A method for removing metal and heavy metal ions from wet-process phosphoric acid

Abstract

This invention discloses a method for removing metal and heavy metal ions from wet-process phosphoric acid, comprising the following steps: S1, adding a reducing agent to wet-process phosphoric acid with a P2O5 mass concentration of 14-43% to obtain mixture 1; S2, adjusting the mass concentration ratio of Mg to Na in mixture 1 to 3-10, the mass concentration ratio of Al to Na to 1 to 1-9, the mass concentration ratio of Mg to K to 5-18, and the mass concentration ratio of Al to K to 3-17 to obtain mixture 2; S3, adding a calcium-containing inorganic substance to mixture 2 to obtain mixture 3; S4, adding a precipitant to mixture 3, followed by filtration and washing. This method can effectively remove metal and heavy metal impurities such as sodium, potassium, calcium, and chromium simultaneously, with a low phosphorus loss rate and a phosphorus recovery rate of over 99.3%.

Description

Technical Field

[0001] This invention relates to the field of wet-process phosphoric acid purification technology, specifically a method for removing metal and heavy metal ions from wet-process phosphoric acid. Background Technology

[0002] Wet-process phosphoric acid is an important intermediate product in the phosphate chemical industry. However, due to the characteristics of raw materials and processes, it contains a large amount of metal and heavy metal impurities, which limits the quality and use of phosphoric acid. In order to make the quality of wet-process phosphoric acid meet the requirements for producing industrial-grade, feed-grade, and even food-grade phosphates, it is necessary to purify and concentrate it.

[0003] Currently, the main purification processes for wet-process phosphoric acid include chemical precipitation, ion exchange, crystallization, solvent precipitation, and solvent extraction. Chemical precipitation is the most widely used and economical method in production. It involves adding a certain amount of precipitant to precipitate impurities. This is one of the commonly used methods for defluorinating wet-process dilute phosphoric acid or removing various harmful heavy metals. The process is simple, requires low operational control, has low investment, and low production costs. However, this method is difficult to effectively remove both metal and heavy metal ions simultaneously, has a high phosphorus loss rate, insufficient purification depth, and can introduce other ions, creating new problems for deep purification. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, this invention provides a method for removing metal and heavy metal ions from wet-process phosphoric acid. This method can effectively remove metal and heavy metal impurities such as sodium, potassium, calcium and chromium at the same time, and the phosphorus loss rate is low, with a phosphorus yield of over 99.3%.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for removing metal and heavy metal ions from wet-process phosphoric acid includes the following steps:

[0007] S1. Add a reducing agent to wet-process phosphoric acid with a P2O5 mass concentration of 14-43% to react and obtain mixture 1;

[0008] S2. Adjust the mass concentration ratio of Mg to Na in mixture 1 to 3-10, the mass concentration ratio of Al to Na to 1-9, the mass concentration ratio of Mg to K to 5-18, and the mass concentration ratio of Al to K to 3-17 to obtain mixture 2;

[0009] S3. Add calcium-containing inorganic substance to the mixture 2 to obtain mixture 3;

[0010] S4. After adding a precipitant to the mixture 3, filter and wash.

[0011] The wet-process phosphoric acid described in this invention includes residual phosphoric acid, such as one or more of sulfuric acid-extracted phosphoric acid, nitric acid-extracted phosphoric acid, and hydrochloric acid-extracted phosphoric acid.

[0012] This invention requires strict control of the P2O5 mass concentration in wet-process phosphoric acid. If the P2O5 content exceeds the limit specified in this invention, no precipitate will be formed upon subsequent addition of the precipitant, the concentration product of NaMgAlF6 and KMgAlF6 will increase, making impurity removal impossible. Furthermore, the liquid viscosity will increase with excessively high phosphoric acid concentration, making the solution difficult to filter. Conversely, if the P2O5 content is below the limit specified in this invention, since the impurity removal method is chemical precipitation, there is a certain impurity removal limit, leading to poor economic efficiency. For example, the P2O5 mass concentration in S1 is any one of 14%, 23.5%, 25%, and 42.7%, or a value between two of these. In some embodiments of this invention, the P2O5 mass concentration in the wet-process phosphoric acid is adjusted using water and dilute phosphoric acid or the washing water from S4.

[0013] The reducing agent described in this invention primarily functions to reduce hexavalent dichromate ions in phosphoric acid to trivalent chromium ions. The trivalent chromium ions then react with a precipitant to form a precipitate, thereby removing chromium ions. Preferably, the reducing agent in S1 is selected from one or more of hydrogen sulfide, sodium sulfide, potassium sulfide, ascorbic acid, and sodium thiosulfate.

[0014] Preferably, the mass ratio of wet-process phosphoric acid with a P2O5 mass concentration of 14-43% to the reducing agent in S1 is (55-200):(0.02-0.5). Exemplarily, the mass ratio of mixture 1 to the reducing agent in S1 is any one of 100:0.02, 100:0.5, 100:0.3, 200:0.5, 55:0.3, or a value between two of these.

[0015] Preferably, after adding the reducing agent in S1, the mixture is stirred at 10–60 rpm.

[0016] Preferably, the reaction temperature of S1 is 30-60°C and the reaction time is 0.5-2 hours.

[0017] In the impurity removal process of this invention, the mass concentration ratio of magnesium, sodium, aluminum, and potassium has a significant impact on the removal efficiency of metals and heavy metals. The main principle for removing potassium and sodium lies in the formation of NaMgAlF6 and KMgAlF6. Within the concentration ratio range defined by this invention, the removal effect is better. If the range is exceeded, as the content of Al and Mg ions in the solution becomes too high, MgF2 and AlF3 are easily formed, resulting in poor removal of Na, K, Ca, and Cr. Furthermore, the mass concentration ratio of magnesium, sodium, aluminum, and potassium is also closely related to the mass concentration of P2O5 in wet-process phosphoric acid. As the phosphoric acid concentration increases, the concentration product of NaMgAlF6 and KMgAlF6 increases, resulting in poorer removal efficiency. Therefore, both ratios need to be strictly controlled. In some embodiments of this invention, the mass concentrations of magnesium, sodium, aluminum, and potassium are adjusted by adding magnesium-containing inorganic substances and / or aluminum-containing inorganic substances to mixture 1.

[0018] Preferably, the magnesium-containing inorganic substance in S2 is selected from any one or more of magnesium oxide, magnesium sulfate, magnesium sulfate heptahydrate, magnesium chloride, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, and magnesium phosphate.

[0019] Preferably, the aluminum-containing inorganic material in S2 is selected from any one or more of aluminum oxide, aluminum sulfate, aluminum chloride, aluminum phosphate, and aluminum dihydrogen phosphate.

[0020] For example, in S2, the mass concentration ratio of Mg to Na is any one or a combination of 3, 5, 5.1, 6, 6.7, 6.8, 7, 7.1, 9, and 9.2; the mass concentration ratio of Al to Na is any one or a combination of 1, 1.9, 2, 2.4, 2.9, 3, 3.9, 4, 4.8, 5, 5.9, 8, and 8.6; the mass concentration ratio of Mg to K is any one or a combination of 5, 5.9, 9.9, 10, 13, 13.9, 14, 14.2, 16, 16.5, 17, 17.8, and 18; and the mass concentration ratio of Al to K is any one or a combination of 3, 3.7, 5, 5.6, 6, 7, 7.6, 11, 11.9, 12, 12.3, 16.6, and 17. Preferably, in step S2, the mass concentration ratio of Mg to Na is adjusted to 6-7, the mass concentration ratio of Al to Na is adjusted to 3-5, the mass concentration ratio of Mg to K is adjusted to 14-16.5, and the mass concentration ratio of Al to K is adjusted to 5.6-12.

[0021] The purpose of adding calcium-containing inorganic substances to S3 in this invention is to form CaMg2Al2F with F, Mg and Al ions in wet-process phosphoric acid. 12 CaMg2Al2F 12 The large crystal particles achieve a physical filtration effect, meaning that the calcium-containing inorganic matter here plays a role in promoting filtration.

[0022] Preferably, the calcium-containing inorganic substance in S3 is selected from any one or more of calcium oxide, calcium sulfate dihydrate, calcium sulfate hemihydrate, and hydroxyapatite.

[0023] Preferably, the mass ratio of mixture 2 to calcium-containing inorganic matter in S3 is (55-204):(0.1-2). Exemplarily, the mass ratio of mixture 2 to calcium-containing inorganic matter in S3 is any one of or between two of the following: 100:0.1, 105.5:2, 110:2, 115:1, 112:2, 113.5:2, 125.5:1.5, 103:1, 203.5:1, and 55:1.

[0024] Preferably, the precipitant in S4 is selected from one or more of hydrofluoric acid, phosphorus pentafluoride, silicon tetrafluoride, fluorosilicic acid, calcium fluoride, and aluminum fluoride.

[0025] Preferably, the mass ratio of mixture 3 to precipitant in step S4 is (56-205):(2-15). Exemplarily, the mass ratio of mixture 3 to precipitant in step S3 is any one of 100:15, 107.5:7, 112:8, 116:15, 114:8, 115.5:8, 127:7, 104:2, 204.5:10, or 56:5, or a value between two of these.

[0026] Preferably, after adding the precipitant in step S4, the mixture is aged at 50–100°C for 1–5 hours and then filtered.

[0027] Preferably, in step S4, the washing process involves rinsing the filter residue with water at a ratio of 1 to 5 times its mass.

[0028] The beneficial effects of this invention are:

[0029] In the process of removing metal and heavy metal ions from wet-process phosphoric acid, this invention first requires controlling the mass concentration of P2O5 in the wet-process phosphoric acid to maintain optimal precipitation conditions. Then, a reducing agent is added to reduce hexavalent dichromate ions in the wet-process phosphoric acid for subsequent precipitation. Next, magnesium-containing and / or aluminum-containing inorganic substances are added. By controlling the mass concentration ratio of magnesium, sodium, aluminum, and potassium, the content and form of various impurity ions in the wet-process phosphoric acid are adjusted. Finally, calcium-containing inorganic substances and a precipitant are added. This effectively removes sodium, potassium, calcium, and chromium from phosphoric acid as acid-insoluble double salt precipitates. This method features a short process, high removal rate, and low phosphorus loss rate, with a phosphorus recovery rate exceeding 99.3%. Attached Figure Description

[0030] Figure 1 The XRD pattern of the precipitate phase after adding the precipitant in Example 9;

[0031] Figure 2The image shows the XRD pattern of the precipitate phase after adding the precipitant in Comparative Example 3. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of the invention, the invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1

[0034] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0035] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0036] 2. Add 0.02 g of sodium thiosulfate to the wet-process phosphoric acid from step 1, stir at 10 rpm, and react at 30 °C for 0.5 h to obtain 100.02 g of mixture 1; the mass concentration ratio of Mg to Na in mixture 1 is 3.0, the mass concentration ratio of Al to Na is 1.9, the mass concentration ratio of Mg to K is 5.9, and the mass concentration ratio of Al to K is 3.7.

[0037] 3. Add 0.1g of calcium sulfate dihydrate to mixture 1 and stir well to obtain 100.12g of mixture 2;

[0038] 4. Add 15g of silicon tetrafluoride to mixture 2, stir evenly, age at 50℃ for 1h, filter to obtain purified phosphoric acid, rinse the filter residue with water equal to the weight of the filter residue, and mix the washing water and filtrate.

[0039] The detection data of metal and heavy metal impurity removal rates in Example 1 are shown in Table 1:

[0040] Table 1

[0041] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 24.4 K (ppm) 1222.9 685.2 42.90 Na (ppm) 2375.3 1752.3 24.83 Ca (ppm) 2324.6 637.9 72.04 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 22.4 35.34 Mass (g) 100 101.9

[0042] The phosphorus yield in this embodiment is 99.45%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0043] Example 2

[0044] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0045] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0046] 2. Add 0.5g of ascorbic acid to the wet phosphoric acid from step 1, stir at 60rpm, and react at 60℃ for 2h to obtain mixture 1;

[0047] 3. Add 5.0g of MgSO4·7H2O to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 5.1, the mass concentration ratio of Al to Na to 1.9, the mass concentration ratio of Mg to K to 9.9, and the mass concentration ratio of Al to K to 3.7 to obtain 105.5g of mixture 2;

[0048] 4. Add 2g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 107.5g of mixture 3;

[0049] 5. Add 7g of fluorosilicic acid to the mixture 3 obtained from S4, stir evenly, age at 100℃ for 5h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0050] The detection data of metal and heavy metal impurity removal rates in Example 2 are shown in Table 2:

[0051] Table 2

[0052] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 23.6 K (ppm) 1222.9 545.2 52.97 Na (ppm) 2375.3 1273.4 43.44 Ca (ppm) 2324.6 578.4 73.75 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 23.5 29.77 Mass (g) 100 105.5

[0053] The phosphorus yield in this embodiment is 99.59%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0054] Example 3

[0055] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0056] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0057] 2. Add 0.3g of hydrogen sulfide to the wet phosphoric acid from step 1, stir at 30rpm, and react at 40℃ for 1h to obtain mixture 1;

[0058] 3. Add 10.0g of MgSO4·7H2O to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 7.1, the mass concentration ratio of Al to Na to 1.9, the mass concentration ratio of Mg to K to 13.9, and the mass concentration ratio of Al to K to 3.7 to obtain 110.3g of mixture 2;

[0059] 4. Add 2g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 112.3g of mixture 3;

[0060] 5. Add 8g of hydrofluoric acid to the mixture 3 obtained from S4, stir evenly, age at 80℃ for 3h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0061] The detection data of metal and heavy metal impurity removal rates in Example 3 are shown in Table 3:

[0062] Table 3

[0063] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 22.7 K (ppm) 1222.9 482.6 56.71 Na (ppm) 2375.3 896.3 58.61 Ca (ppm) 2324.6 556.7 73.73 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 21.2 34.12 Mass (g) 100 109.7

[0064] The phosphorus yield in this embodiment is 99.61%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0065] Example 4

[0066] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0067] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0068] 2. Add 0.3g of hydrogen sulfide to the wet phosphoric acid from step 1, stir at 20rpm, and react at 40℃ for 1h to obtain mixture 1;

[0069] 3. Add 15.0g of MgSO4·7H2O to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 9.2, the mass concentration ratio of Al to Na to 1.9, the mass concentration ratio of Mg to K to 17.8, and the mass concentration ratio of Al to K to 3.7 to obtain 115.3g of mixture 2;

[0070] 4. Add 1g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 116.3g of mixture 3;

[0071] 5. Add 15g of silicon tetrafluoride to the mixture 3 obtained from S4, stir evenly, age at 70℃ for 3h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0072] The detection data of metal and heavy metal impurity removal rates in Example 4 are shown in Table 4:

[0073] Table 4

[0074] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 21.9 K (ppm) 1222.9 471.8 56.25 Na (ppm) 2375.3 845.7 59.63 Ca (ppm) 2324.6 587.6 71.34 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 18.5 40.57 Mass (g) 100 113.4

[0075] The phosphorus yield in this embodiment is 99.34%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0076] Example 5

[0077] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0078] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0079] 2. Add 0.3g of ascorbic acid to the wet phosphoric acid from step 1, stir at 40rpm, and react at 50℃ for 1.5h to obtain mixture 1;

[0080] 3. Add 10.0g MgSO4·7H2O+1.5g Al2(SO4)3 to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 7.1, the mass concentration ratio of Al to Na to 2.9, the mass concentration ratio of Mg to K to 13.9, and the mass concentration ratio of Al to K to 5.6 to obtain 111.8g of mixture 2;

[0081] 4. Add 2g of calcium sulfate hemihydrate to mixture 2 obtained from S3 and stir well to obtain 113.8g of mixture 3;

[0082] 5. Add 8g of hydrofluoric acid to the mixture 3 obtained from S4, stir evenly, age at 75℃ for 3.5h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0083] The detection data of metal and heavy metal impurity removal rates in Example 5 are shown in Table 5:

[0084] Table 5

[0085] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 22.5 K (ppm) 1222.9 324.6 70.70 Na (ppm) 2375.3 297.6 86.17 Ca (ppm) 2324.6 556.3 73.58 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 19.8 38.08 Mass (g) 100 110.4

[0086] The phosphorus yield in this embodiment is 99.36%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0087] Example 6

[0088] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0089] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0090] 2. Add 0.5g of sodium thiosulfate to the wet phosphoric acid from step 1, stir at 20rpm, and react at 55℃ for 1h to obtain mixture 1;

[0091] 3. Add 10.0g MgSO4·7H2O+3.0g Al2(SO4)3 to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 7.1, the mass concentration ratio of Al to Na to 3.9, the mass concentration ratio of Mg to K to 13.9, and the mass concentration ratio of Al to K to 7.6 to obtain 113.5g of mixture 2;

[0092] 4. Add 2g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 115.5g of mixture 3;

[0093] 5. Add 8g of fluorosilicic acid to the mixture 3 obtained from S4, stir evenly, age at 95℃ for 3h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0094] The detection data of metal and heavy metal impurity removal rates in Example 6 are shown in Table 6:

[0095] Table 6

[0096] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 22.4 K (ppm) 1222.9 335.9 69.46 Na (ppm) 2375.3 307.8 85.59 Ca (ppm) 2324.6 587.3 71.91 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 20.7 34.79 Mass (g) 100 111.2

[0097] The phosphorus yield in this embodiment is 99.64%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0098] Example 7

[0099] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0100] 1. Take 100g of wet-process phosphoric acid with a P2O5 mass concentration of 25%;

[0101] 2. Add 0.5g of ascorbic acid to the wet phosphoric acid from step 1, stir at 20rpm, and react at 40℃ for 1h to obtain mixture 1;

[0102] 3. Add 15.0g MgSO4·7H2O+10g Al2(SO4)3 to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 9.2, the mass concentration ratio of Al to Na to 8.6, the mass concentration ratio of Mg to K to 17.8, and the mass concentration ratio of Al to K to 16.6 to obtain 125.5g of mixture 2;

[0103] 4. Add 1.5g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 127g of mixture 3;

[0104] 5. Add 7g of phosphorus pentafluoride to the mixture 3 obtained from S4, stir evenly, age at 70℃ for 2h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0105] The detection data of metal and heavy metal impurity removal rates in Example 7 are shown in Table 7:

[0106] Table 7

[0107] Test items Before wet phosphoric acid purification After wet phosphoric acid purification Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 25.00 24.7 K (ppm) 1222.9 467.8 55.32 Na (ppm) 2375.3 769.4 62.17 Ca (ppm) 2324.6 797.4 59.93 Mg (ppm) 7201.1 Al (ppm) 4539.3 Cr (ppm) 35.3 18.9 37.46 Mass (g) 100 116.8

[0108] The phosphorus yield in this example is 99.67%. (The phosphorus yield in this example is the ratio of P2O5 in the acid after impurity removal to (P2O5 in the acid before impurity removal + P2O5 generated from the hydrolysis of phosphorus pentafluoride)).

[0109] Example 8

[0110] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0111] 1. Add 50g of water, dilute phosphoric acid, or the washing water obtained in step 5 to 50g of raffinate phosphoric acid with a P2O5 mass concentration of 47% to adjust the P2O5 mass concentration in wet phosphoric acid to 23.5% to obtain the adjusted raffinate phosphoric acid.

[0112] 2. Add 0.3g of ascorbic acid to 100g of the regulated phosphoric acid obtained in step 1, stir at 20rpm, and react at 50℃ for 0.5h to obtain mixture 1;

[0113] 3. Add 3g of Al2(SO4)3 to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 6.7, the mass concentration ratio of Al to Na to 4.8, the mass concentration ratio of Mg to K to 16.5, and the mass concentration ratio of Al to K to 11.9; to obtain 103.3g of mixture 2;

[0114] 4. Add 1g of calcium oxide to mixture 2 obtained from S3 and stir evenly to obtain 104.3g of mixture 3;

[0115] 5. Add 2g of hydrofluoric acid to the mixture 3 obtained from S4, stir evenly, age at 60℃ for 2h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water and filtrate.

[0116] The detection data of metal and heavy metal impurity removal rates in Example 8 are shown in Table 8:

[0117] Table 8

[0118] Test items Before removing impurities from residual phosphoric acid After removing impurities from the residual phosphoric acid Metal / Heavy Metal Removal Rate <![CDATA[P2O5(%)]]> 47.00 22.7 K (ppm) 1587.9 237.8 69.09 Na (ppm) 3925.4 366.5 80.73 Ca (ppm) 312.7 55.3 63.50 Mg (ppm) 26172.7 Al (ppm) 9494.3 Cr (ppm) 67.8 19.5 40.64 Mass (g) 50 103.2

[0119] The phosphorus yield in this embodiment is 99.69%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0120] Example 9

[0121] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0122] 1. Add 150g of water, dilute phosphoric acid, or the washing water obtained in step 5 to 50g of raffinate phosphoric acid with a P2O5 mass concentration of 47% to adjust the P2O5 mass concentration in wet phosphoric acid to 14% to obtain the adjusted raffinate phosphoric acid.

[0123] 2. Add 0.5g of hydrogen sulfide to 200g of regulated phosphoric acid obtained in step 1, stir at 30rpm, and react at 50℃ for 1h to obtain mixture 1;

[0124] 3. Add 3g of Al2(SO4)3 to mixture 1 from step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 6.8, the mass concentration ratio of Al to Na to 5.9, the mass concentration ratio of Mg to K to 14.2, and the mass concentration ratio of Al to K to 12.3 to obtain 203.5g of mixture 2;

[0125] 4. Add 1g of calcium sulfate dihydrate to mixture 2 obtained from S3 and stir well to obtain 204.5g of mixture 3;

[0126] 5. Add 10g of fluorosilicic acid to the mixture 3 obtained from S4, stir evenly, age at 70℃ for 3h, filter to obtain purified phosphoric acid, rinse the filter residue with 3 times the weight of the filter residue with water, and mix the washing water with the filtrate.

[0127] The detection data of metal and heavy metal impurity removal rates in Example 9 are shown in Table 9:

[0128] Table 9

[0129]

[0130] The phosphorus yield in this embodiment is 99.62%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0131] The precipitate phase after adding the precipitant in step 5 of Example 9 was analyzed, and the results are shown in [the table below]. Figure 1 XRD pattern, from Figure 1 It can be seen that the precipitate contains NaMgAlF6 and CaMg2Al2F6. 12 Precipitated phases include MgF2, KMgAlF6, etc. The main elemental contents of the complex salt are:

[0132] K (ppm) Na (ppm) Ca (ppm) Mg (ppm) Al(ppm) F(％) 9720.4 34460.7 65490.5 150704.1 129500.2 59.2

[0133] Example 10

[0134] The method for removing metal and heavy metal ions from wet-process phosphoric acid in this embodiment includes the following steps:

[0135] 1. Add 5g of water, dilute phosphoric acid, or the washing water obtained in step 5 to 50g of raffinate phosphoric acid with a P2O5 mass concentration of 47% to adjust the P2O5 mass concentration in wet phosphoric acid to 42.7% to obtain the adjusted raffinate phosphoric acid.

[0136] 2. Add 0.3g of hydrogen sulfide to 55g of the regulated phosphoric acid obtained in step 1, stir at 30rpm, and react at 45℃ for 1h to obtain 55.3g of mixture 1; the mass concentration ratio of Mg to Na in mixture 1 is 6.7, the mass concentration ratio of Al to Na is 2.4, the mass concentration ratio of Mg to K is 16.5, and the mass concentration ratio of Al to K is 6.0.

[0137] 3. Add 1g of calcium oxide to the obtained mixture 1 and stir evenly to obtain 56.3g of mixture 2;

[0138] 4. Add 5g of hydrofluoric acid to the obtained mixture 2, stir evenly, age at 60℃ for 2.5h, filter to obtain purified phosphoric acid, rinse the filter residue with 5 times the weight of the filter residue with water, and reuse the washing water in step 1.

[0139] The detection data of metal and heavy metal impurity removal rates in Example 10 are shown in Table 10:

[0140] Table 10

[0141]

[0142]

[0143] The phosphorus yield in this embodiment is 99.65%. Phosphorus yield = (phosphorus content after impurity removal + phosphorus content in wash water) / phosphorus phosphate content before treatment.

[0144] Comparative Example 1

[0145] Same as Example 5, except that in step 1, water, dilute phosphoric acid, or the washing water described in step 5 is added to adjust the mass concentration of P2O5 in wet-process phosphoric acid to 5%.

[0146] The detection data of metal and heavy metal impurity removal rates for Comparative Example 1 are shown in Table 11:

[0147] Table 11

[0148]

[0149] The phosphorus yield in this comparative example was 99.83%. Phosphorus yield = (Phosphorus content after impurity removal + Phosphorus content in wash water) / Phosphorus phosphate content before treatment.

[0150] Comparative Example 2

[0151] Same as Example 5, except that the mass concentration of P2O5 in wet-process phosphoric acid is controlled to 50% by concentration.

[0152] The detection data of metal and heavy metal impurity removal rates for Comparative Example 2 are shown in Table 12:

[0153] Table 12

[0154]

[0155] The phosphorus yield in this comparative example was 99.83%. Phosphorus yield = (Phosphorus content after impurity removal + Phosphorus content in wash water) / Phosphorus phosphate content before treatment.

[0156] Comparative Example 3

[0157] Same as Example 5, except that:

[0158] Add 20.0g MgSO4·7H2O+15g Al2(SO4)3 to mixture 1 in step 2, and adjust the mass concentration ratio of Mg to Na in the mixture to 11.2, the mass concentration ratio of Al to Na to 11.9, the mass concentration ratio of Mg to K to 21.8, and the mass concentration ratio of Al to K to 23.1.

[0159] The detection data of metal and heavy metal impurity removal rates for Comparative Example 3 are shown in Table 13:

[0160] Table 13

[0161]

[0162]

[0163] The phosphorus yield in this comparative example was 99.51%. Phosphorus yield = (Phosphorus content after impurity removal + Phosphorus content in wash water) / Phosphorus phosphate content before treatment.

[0164] The precipitate phase after adding the precipitant in step 5 of this comparative example was analyzed, and the results are shown in the figure. Figure 2 XRD pattern, from Figure 1 It can be seen that the precipitate phase contains only MgAlF5·2H2O, indicating that the mass concentration ratio of magnesium, sodium, aluminum and potassium elements has an important influence on the removal of metals and heavy metals. If it exceeds the scope of this invention, MgF2 and AlF3 are easily formed, resulting in poor removal of Na, K, Ca and Cr.

[0165] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for removing metal and heavy metal ions from wet-process phosphoric acid, characterized in that, Includes the following steps: S1. Add a reducing agent to wet-process phosphoric acid with a P2O5 mass concentration of 14~43% to react and obtain mixture 1; S2. Adjust the mass concentration ratio of Mg to Na in mixture 1 to 3~10, the mass concentration ratio of Al to Na to 1~9, the mass concentration ratio of Mg to K to 5~18, and the mass concentration ratio of Al to K to 3~17 to obtain mixture 2; S3. Add calcium-containing inorganic substance to the mixture 2 to obtain mixture 3; S4. After adding a precipitant to the mixture 3, filter and wash. The reducing agent in S1 is selected from one or more of hydrogen sulfide, sodium sulfide, potassium sulfide, ascorbic acid, and sodium thiosulfate; the precipitating agent in S4 is selected from one or more of hydrofluoric acid, phosphorus pentafluoride, silicon tetrafluoride, fluorosilicic acid, calcium fluoride, and aluminum fluoride.

2. The method of claim 1, wherein, The mass ratio of wet-process phosphoric acid with a P2O5 mass concentration of 14-43% to the reducing agent in S1 is (55-200):(0.02-0.5).

3. The method of claim 1, wherein, The reaction temperature of S1 is 30~60℃, and the reaction time is 0.5~2h.

4. The method of claim 1, wherein, In step S2, the mass concentrations of magnesium, sodium, aluminum, and potassium are adjusted by adding magnesium-containing inorganic substances and / or aluminum-containing inorganic substances to mixture 1.

5. The method of claim 1, wherein, The calcium-containing inorganic substance in S3 is selected from any one or more of calcium oxide, calcium sulfate dihydrate, calcium sulfate hemihydrate, and hydroxyapatite.

6. The method of claim 1, wherein, The mass ratio of mixture 2 to calcium-containing inorganic matter in S3 is (55~204):(0.1~2).

7. The method of claim 1, wherein, The mass ratio of mixture 3 to precipitant in S4 is (56~205):(2~15).

8. The method of claim 1, wherein, After adding a precipitant to S4, it is aged at 50~100℃ for 1~5 hours and then filtered.

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