Method for preparing condensed aluminum phosphate from phosphorus-containing waste acid

Abstract

The invention discloses a method for preparing condensed aluminum phosphate from phosphorus-containing waste acid, and relates to the technical field of solid waste treatment. The invention discloses a method for preparing condensed aluminum phosphate from phosphorus-containing waste acid. The method comprises the following steps: S1, alkali dissolution; s2, purifying; s3, synthesis: supplementing phosphoric acid into the purified phosphorus-containing waste acid, adding the aluminum-containing mother liquor in the S1, and reacting to obtain pasty aluminum phosphate; and S4, polycondensation: carrying out high-temperature drying and dehydration condensation on the pasty aluminum phosphate in S3 to obtain the condensed aluminum phosphate. The high-purity condensed aluminum phosphate finished product is synthesized through extraction and alkali dissolution purification, impurity stripping and full recovery of phosphorus and aluminum resources in the waste, the purity of the condensed aluminum phosphate product obtained through the preparation method can reach 94.2% or above and can reach 96.7% at most, the recovery rate of phosphorus in the solid waste reaches 71% or above and can reach 91% at most, and the method is suitable for industrial production. The recovery rate of aluminum resources reaches 69% or above, and the highest recovery rate can reach 90%.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, and more specifically, to a method for preparing condensed aluminum phosphate from phosphoric acid-containing waste acid. Background Art

[0002] In the electroplating aluminum alloy anodic oxidation chemical polishing process, due to the use of phosphorus-containing reagents, a large amount of phosphoric acid-containing waste acid is generated during phosphating and polishing. The main components are 10-40% phosphoric acid, 5-20% sulfuric acid, 1-5% aluminum ions and a small amount of heavy metal ions. According to the requirements of the "National Hazardous Waste List" in 2021, the phosphoric acid-containing waste acid in the aluminum profile surface treatment industry belongs to hazardous waste of HW34 waste acid and HW17 surface treatment waste, and it is urgent to be properly treated and disposed of by qualified units. Traditional treatment processes generally use calcium oxide or calcium oxide-sodium hydroxide neutralization precipitation methods to remove phosphorus by combining calcium ions with phosphate ions to form insoluble calcium salts. This not only causes a huge waste of phosphorus resources, but also generates a large amount of secondary hazardous waste sludge as by-products, increasing the production cost of enterprises and aggravating environmental secondary pollution, and the disadvantages are particularly obvious. Therefore, the recovery and utilization of phosphoric acid in the waste liquid is of great significance both economically and environmentally. The commonly used recovery processes in the prior art include diffusion dialysis, electrodialysis, ion exchange, extraction, etc., which mainly focus on the recovery of phosphoric acid. Since the recovery process often produces dilute acid solutions, it must be concentrated before recycling to reach the required concentration for reuse. Currently, the main methods for concentrating phosphoric acid in industry are high-temperature concentration and vacuum evaporation concentration. The concentration process has high energy consumption, large equipment volume, large investment, and is prone to entrainment and other phenomena. To sum up, the current comprehensive utilization technologies for various phosphoric acid-containing waste acids generated during phosphating and polishing all have deficiencies such as complex processes, high energy consumption, low utilization efficiency and value of phosphoric acid, high impurity content in products, and affecting the use performance. Therefore, it is urgent to seek a more economical treatment process for phosphorus-containing wastewater from the anodic oxidation of aluminum and its alloys.

[0003] The prior art discloses a method for treating aluminum oxide sludge and waste acid, including Step 1, a detection step of sampling and detecting the aluminum oxide sludge and chemical polishing waste acid to be recycled; Step 2, an acidification step of putting the sludge to be recycled into an acidification kettle and adding acid solution for dissolution; Step 3, a pressure filtration step of pressure-filtering the mixed liquid through a diaphragm pressure filter to obtain a calcium phosphate product with a certain water content; Step 4, a complexation step of introducing the filtrate generated in the pressure filtration step into a complexation kettle, and complexing the heavy metal ions in the filtrate with a complexing agent to form a solid filter residue; Step 5, a liquid separation step of adsorbing trace heavy metal ions in the filtrate in the complexation step through a resin adsorption column to respectively obtain filtrate A and filtrate B, where filtrate A is mainly the acidified sludge with sulfuric acid, and filtrate B is mainly the acidified sludge with chemical polishing waste acid; Step 6, a pressure filtration step of transferring filtrate A into a dephosphorization kettle, adding a dephosphorizing agent to form a precipitate, and then performing pressure filtration to obtain an aluminum phosphate product and filtrate C; Step 7, for the filtrate C product obtained in the pressure filtration step, a part of it can be used as an aluminum sulfate water purifying agent product, and the other part is introduced into a neutralization kettle, adding alkali for neutralization to form a precipitate, and then performing pressure filtration in a diaphragm pressure filter to obtain a hydrated aluminum hydroxide product, and the filtrate after pressure filtration enters Step 8; Step 8, concentrating and crystallizing the filtrate obtained in Step 7 to obtain an anhydrous sodium sulfate product and condensed water; the condensed water is recycled for use in sulfuric acid dilution and dispersion water in production; Step 9, transferring filtrate B obtained in the liquid separation step into a preparation kettle, adding phosphoric acid to adjust the acidity and content of the solution to obtain a liquid aluminum dihydrogen phosphate product; Step 10, further concentrating and drying a part of the liquid aluminum dihydrogen phosphate product in Step 9 to obtain a solid aluminum dihydrogen phosphate product. This prior art realizes the recycling of aluminum phosphate products from aluminum oxide sludge and waste acid, but on the one hand, its operation steps are complex, requiring multiple steps such as detection - acidification - pressure filtration - complexation - adsorption - dephosphorization, and the phosphorus content and aluminum content of the obtained aluminum phosphate product are low, and the efficient recycling and utilization of phosphorus and aluminum resources cannot be achieved. Summary of the Invention

[0004] The object of the present invention is to overcome the defects and deficiencies that the existing process steps for recycling phosphorus-containing chemical polishing waste acid and aluminum-containing sludge are complex and the recovery rates of phosphorus and aluminum resources are not high, and to provide a method for preparing condensed aluminum phosphate using phosphorus-containing waste acid.

[0005] The above object of the present invention is achieved by the following technical solutions:

[0006] A method for preparing condensed aluminum phosphate using phosphorus-containing waste acid, including the following steps:

[0007] S1. Alkali dissolution: Adding aluminum-containing sludge to dilute alkali solution, fully dissolving and reacting, and obtaining an aluminum-containing mother liquor after pressure filtration;

[0008] S2. Purification: Add an extractant to the phosphorous-containing waste acid, and perform countercurrent forward extraction to separate the raffinate and the loaded organic phase; use water to perform countercurrent back-extraction and regeneration on the loaded organic phase, and add a desulfurizing agent to the back-extract after separation, and then obtain the purified phosphorous-containing waste acid after pressure filtration;

[0009] S3. Synthesis: Supplement phosphoric acid to the purified phosphorous-containing waste acid, add the aluminum-containing mother liquor in S1, control the pH of the reaction solution to be 1.5 - 3.0, stir and react at 120 - 150 °C for 3 - 5 h, and obtain paste-like aluminum phosphate after pressure filtration;

[0010] S4. Polycondensation: Dry the paste-like aluminum phosphate in S3 at a high temperature of 100 - 120 °C for 4 - 6 h, then raise the temperature to 300 - 400 °C for dehydration and polycondensation for 8 - 10 h, and pulverize to obtain condensed aluminum phosphate.

[0011] Among them, it should be noted that:

[0012] In step S1, in order to ensure sufficient reaction, it is preferably stirred and reacted at 50 - 60 °C for 0.3 - 0.5 h.

[0013] In the method for preparing condensed aluminum phosphate from phosphorous-containing waste acid of the present invention, in step S3, in order to fully precipitate aluminum phosphate, it is necessary to control the pH to be 1.5 - 3.0.

[0014] In the polycondensation step of S4, high-temperature drying is to remove the free water between particles, and dehydration and polycondensation is to remove the bound water in the molecule.

[0015] Condensed aluminum phosphate is a kind of aluminum phosphate, which is mainly used as a curing agent for high-temperature furnace refractory materials, a flux for special glass, a catalyst for ceramics and organic synthesis, etc. The method for preparing condensed aluminum phosphate from phosphorous-containing waste acid of the present invention uses phosphorous-containing waste acid and aluminum-containing sludge and other wastes as raw materials, uses extraction and alkali dissolution for purification and refinement, strips impurities, fully recovers the phosphorus and aluminum resources in the waste, synthesizes high-purity condensed aluminum phosphate products, and realizes the maximum value of the coordinated disposal and resource utilization of waste.

[0016] In the specific implementation manner, the extractant for extraction in step S2 of the present invention can be n-butanol or tributyl phosphate, and n-butanol is preferred.

[0017] When using n-butanol as the extractant, phosphoric acid is extracted in the form of molecules, and metal impurity ions are basically not extracted by n-butanol, ensuring the extraction rate of phosphoric acid and the purity of condensed aluminum phosphate.

[0018] Preferably, the phase ratio of countercurrent forward extraction in S2 is O / A = 2 - 4.

[0019] Preferably, the phase ratio of countercurrent back-extraction in S2 is O / A = 2 - 3.

[0020] Among them, it should be noted that:

[0021] The extraction phase ratio O / A is the volume ratio of the organic phase to the aqueous phase. The extraction phase ratio not only affects the dosage of the extractant but also relates to the extraction rate. Controlling an appropriate phase ratio can ensure the utilization rate of the extractant, improve the extraction effect, and increase the purity of the final condensed aluminum phosphate product.

[0022] In the specific implementation manner, preferably, the molar ratio of phosphoric acid in the S3 reaction solution to Al2O3 in the aluminum-containing mother liquor is 2 - 3:1.

[0023] In the specific implementation manner, the aluminum-containing sludge of the present invention is dissolved with a dilute alkali solution, and the mass concentration of the dilute alkali solution is 10% - 15%.

[0024] Preferably, the mass ratio of the aluminum-containing sludge to the dilute alkali solution added in S1 is 1:(0.8 - 1.2).

[0025] In the specific implementation manner, the desulfurizer of the present invention is barium carbonate or barium hydroxide. Preferably, the addition amount of the desulfurizer is the amount required to control the molar ratio of Ba 2+ to SO4 2- to be 1.0 - 1.1:1.

[0026] The method for preparing condensed aluminum phosphate using phosphorus-containing waste acid of the present invention can effectively recover the phosphorus resources and aluminum resources in the phosphorus-containing pickling waste acid. The phosphorus-containing waste acid has a phosphoric acid content of 10 - 20 wt%, a sulfuric acid content of 5 - 10 wt%, and an aluminum ion content of 1 - 5 wt%.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention prepares condensed aluminum phosphate using phosphorus-containing waste acid, taking waste materials such as phosphorus-containing waste acid and aluminum-containing sludge as raw materials, using extraction and alkali dissolution for purification and impurity stripping, fully recovering the phosphorus and aluminum resources in the waste materials, and synthesizing high-purity condensed aluminum phosphate finished products. The purity of the condensed aluminum phosphate product obtained by the preparation method of the present invention can reach 94.2% and above, up to 96.7% at most, achieving a phosphorus recovery rate in the solid waste of 71% and above, up to 91% at most, and an aluminum resource recovery rate of 69% and above, up to 90% at most.

[0029] Attached is the specific implementation manner

[0030] The following further illustrates the present invention in combination with the specific implementation manner, but the embodiments do not limit the present invention in any form. Unless otherwise stated, the raw material reagents used in the embodiments of the present invention are conventional raw material reagents purchased.

[0031] Among them, the effective component contents of the aluminum-containing sludge and phosphorus-containing waste acid used in the embodiments and comparative examples of the present invention are as follows:

[0032] The aluminum content of the aluminum-containing sludge is 14.7% (calculated as Al2O3).

[0033] The phosphoric acid content of the phosphoric acid-containing waste acid is 15.6% (calculated as H3PO4), the sulfuric acid content is 7.8% (calculated as H2SO4), and the aluminum ion content is 2.9% (calculated as Al2O3);

[0034] Example 1

[0035] A method for preparing condensed aluminum phosphate using phosphoric acid-containing waste acid, comprising the following steps:

[0036] S1. Alkaline dissolution: Add the aluminum-containing sludge to a 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60°C for 0.5 h, and obtain the aluminum-containing mother liquor after pressure filtration.

[0037] S2. Purification: Add a n-butanol extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 3, perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; perform countercurrent back-extraction and regeneration on the loaded organic phase with pure water at a phase ratio of O / A = 3 for 0.5 h, add 1.0 mol of barium carbonate desulfurizer to the back-extracted solution after separation, and obtain the purified phosphoric acid-containing waste acid after pressure filtration.

[0038] S3. Synthesis: According to the material ratio, add an appropriate amount of phosphoric acid to the purified phosphoric acid-containing waste acid, and then slowly add the aluminum-containing mother liquor in S1 (until n(P2O5):n(Al2O3) = 3:1 in the solution), control the solution pH = 2.5, stir and react at 140°C for 4 h, and obtain paste-like aluminum phosphate after pressure filtration.

[0039] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry at 110°C for 5 h, then raise the temperature to 400°C for dehydration and condensation for 10 h, and pulverize to obtain the high-purity condensed aluminum phosphate product.

[0040] Example 2

[0041] A method for preparing condensed aluminum phosphate using phosphoric acid-containing waste acid, comprising the following steps:

[0042] S1. Alkaline dissolution: Add the aluminum-containing sludge to a 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60°C for 0.5 h, and obtain the aluminum-containing mother liquor after pressure filtration.

[0043] S2. Purification: Add a n-butanol extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 2, perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; perform countercurrent back-extraction and regeneration on the loaded organic phase with pure water at a phase ratio of O / A = 2 for 0.5 h, add 1.0 mol of barium carbonate desulfurizer to the back-extracted solution after separation, and obtain the purified phosphoric acid-containing waste acid after pressure filtration.

[0044] S3. Synthesis: According to the material ratio, appropriate amount of phosphoric acid is added to the purified phosphorus-containing waste acid, and then the aluminum-containing mother liquor in S1 is slowly added (until n(P2O5):n(Al2O3) = 3:1 in the solution), the pH of the solution is controlled at 2.5, and the mixture is stirred and reacted at 140 °C for 4 h, and then filtered to obtain paste-like aluminum phosphate.

[0045] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry it at 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0046] Example 3

[0047] A method for preparing condensed aluminum phosphate from phosphorus-containing waste acid, comprising the following steps:

[0048] S1. Alkaline dissolution: Add aluminum-containing sludge to 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60 °C for 0.5 h, and filter to obtain the aluminum-containing mother liquor.

[0049] S2. Purification: Add n-butanol extractant to the phosphorus-containing waste acid according to the phase ratio O / A = 4, perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; perform countercurrent back-extraction and regeneration on the loaded organic phase with pure water according to the phase ratio O / A = 3 for 0.5 h, and after separation, add 1.0 mol of barium carbonate desulfurizer to the back-extract, and filter to obtain the purified phosphorus-containing waste acid.

[0050] S3. Synthesis: According to the material ratio, appropriate amount of phosphoric acid is added to the purified phosphorus-containing waste acid, and then the aluminum-containing mother liquor in S1 is slowly added (until n(P2O5):n(Al2O3) = 3:1 in the solution), the pH of the solution is controlled at 2.5, and the mixture is stirred and reacted at 140 °C for 4 h, and then filtered to obtain paste-like aluminum phosphate.

[0051] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry it at 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0052] Example 4

[0053] A method for preparing condensed aluminum phosphate from phosphorus-containing waste acid, comprising the following steps:

[0054] S1. Alkaline dissolution: Add aluminum-containing sludge to 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60 °C for 0.5 h, and filter to obtain the aluminum-containing mother liquor.

[0055] S2. Purification: Add n-butanol extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 3, and perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; use pure water to perform countercurrent back-extraction and regeneration on the loaded organic phase at a phase ratio of O / A = 3 for 0.5 h. After separation, add 1.0 mol of barium carbonate desulfurizer to the back-extraction solution, and after pressure filtration, the purified phosphoric acid-containing waste acid can be obtained.

[0056] S3. Synthesis: According to the material ratio, add an appropriate amount of phosphoric acid to the purified phosphoric acid-containing waste acid, and then slowly add the aluminum-containing mother liquor in S1 (until n(P2O5):n(Al2O3) = 2:1 in the solution), control the solution pH = 2.5, and stir and react at 140 °C for 4 h. After pressure filtration, paste-like aluminum phosphate can be obtained.

[0057] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry at a high temperature of 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0058] Example 5

[0059] A method for preparing condensed aluminum phosphate using phosphoric acid-containing waste acid, comprising the following steps:

[0060] S1. Alkaline dissolution: Add aluminum-containing sludge to 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60 °C for 0.5 h, and after pressure filtration, the aluminum-containing mother liquor can be obtained.

[0061] S2. Purification: Add n-butanol extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 3, and perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; use pure water to perform countercurrent back-extraction and regeneration on the loaded organic phase at a phase ratio of O / A = 3 for 0.5 h. After separation, add 1.0 mol of barium carbonate desulfurizer to the back-extraction solution, and after pressure filtration, the purified phosphoric acid-containing waste acid can be obtained.

[0062] S3. Synthesis: According to the material ratio, add an appropriate amount of phosphoric acid to the purified phosphoric acid-containing waste acid, and then slowly add the aluminum-containing mother liquor in S1 (until n(P2O5):n(Al2O3) = 1:1 in the solution), control the solution pH = 2.5, and stir and react at 140 °C for 4 h. After pressure filtration, paste-like aluminum phosphate can be obtained.

[0063] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry at a high temperature of 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0064] Example 6

[0065] A method for preparing condensed aluminum phosphate using phosphoric acid-containing waste acid, comprising the following steps:

[0066] S1. Alkaline dissolution: Add aluminum-containing sludge to 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60 °C for 0.5 h, and obtain the aluminum-containing mother liquor after pressure filtration.

[0067] S2. Purification: Add tributyl phosphate extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 3, perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; perform countercurrent back-extraction and regeneration on the loaded organic phase with pure water at a phase ratio of O / A = 3 for 0.5 h, and add 1.0 mol barium carbonate desulfurizer to the back-extracted solution after separation, and obtain the purified phosphoric acid-containing waste acid after pressure filtration.

[0068] S3. Synthesis: According to the material ratio, add an appropriate amount of phosphoric acid to the purified phosphoric acid-containing waste acid, and then slowly add the aluminum-containing mother liquor in S1 (until n(P2O5):n(Al2O3) = 3:1 in the solution), control the solution pH = 2.5, stir and react at 140 °C for 4 h, and obtain paste-like aluminum phosphate after pressure filtration.

[0069] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry at 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0070] Comparative Example 1

[0071] A method for preparing condensed aluminum phosphate from phosphoric acid-containing waste acid, comprising the following steps:

[0072] S1. Alkaline dissolution: Add aluminum-containing sludge to 15% sodium hydroxide solution at a mass ratio of 1:1, stir and react at 60 °C for 0.5 h, and obtain the aluminum-containing mother liquor after pressure filtration.

[0073] S2. Purification: Add n-butanol extractant to the phosphoric acid-containing waste acid at a phase ratio of O / A = 3, perform countercurrent forward extraction for 1 h to separate the raffinate and the loaded organic phase; perform countercurrent back-extraction and regeneration on the loaded organic phase with pure water at a phase ratio of O / A = 3 for 0.5 h, and add 1.0 mol barium carbonate desulfurizer to the back-extracted solution after separation, and obtain the purified phosphoric acid-containing waste acid after pressure filtration.

[0074] S3. Synthesis: According to the material ratio, add an appropriate amount of phosphoric acid to the purified phosphoric acid-containing waste acid, and then slowly add the aluminum-containing mother liquor in S1 (until n(P2O5):n(Al2O3) = 3:1 in the solution), control the solution pH = 4, stir and react at 140 °C for 4 h, and obtain paste-like aluminum phosphate after pressure filtration.

[0075] S4. Polycondensation: Transfer the paste-like aluminum phosphate in S3 to a high-temperature converter, first dry at 110 °C for 5 h, then raise the temperature to 400 °C for dehydration and polycondensation for 10 h, and pulverize to obtain the finished product of high-purity condensed aluminum phosphate.

[0076] Result detection

[0077] The effective indicators of the condensed aluminum phosphate prepared in the above examples and comparative examples were compared and evaluated with the commercially purchased condensed aluminum phosphate. The specific results are shown in Table 1 below. The product purity and the recovery effects of phosphorus and aluminum resources are shown in Table 2:

[0078] Among them, the detection methods for each index are as follows:

[0079] For the detection method of phosphorus pentoxide, refer to GB / T 1871.1-1995 Determination of phosphorus pentoxide content in phosphate rock and concentrate - Quinoline phosphomolybdate gravimetric method and volumetric method;

[0080] For the detection method of aluminum oxide, refer to GB / T 1871.3-1995 Determination of aluminum oxide content in phosphate rock and concentrate - Volumetric method and spectrophotometric method;

[0081] For the detection method of moisture, refer to HJ 613-2011 Determination of soil dry matter and moisture - Gravimetric method;

[0082] For the detection method of residue on sieve, refer to HG / T 3852-2006 Method for determination of residue on sieve of pigments.

[0083] Table 1 Main performance indicators of condensed aluminum phosphate products

[0084] Serial number Appearance <![CDATA[P2O5 / %]]> <![CDATA[Al2O3 / %]]> Moisture content / % Residue on sieve (325 mesh) / % Purchased condensed aluminum phosphate White powder 63～65 15～16 ≤1.0 ≤0.5 Example 1 White powder 64.8 15.5 0.5 0.2 Example 2 White powder 64.3 15.4 0.4 0.3 Example 3 White powder 64.2 15.3 0.5 0.2 Example 4 White powder 64.7 15.5 0.7 0.3 Example 5 White powder 64.6 15.3 0.8 0.4 Example 6 White powder 63.1 15.0 0.5 0.1

[0085] Table 2 Purity of condensed aluminum phosphate products and recovery rates of phosphorus and aluminum resources

[0086]

[0087]

[0088] As can be seen from Table 1 above, the condensed aluminum phosphate products prepared by the method of preparing condensed aluminum phosphate using phosphorous-containing waste acid in the present invention can fully meet the product standards of commercially purchased condensed aluminum phosphate, indicating that the preparation method of the present invention can make full use of solid waste resources such as phosphorous-containing waste acid and aluminum-containing sludge, realize the high-value recovery of phosphorus and aluminum therein, and prepare high-quality condensed aluminum phosphate products.

[0089] Table 2 shows the purity of the condensed aluminum phosphate products prepared by the method of preparing condensed aluminum phosphate using phosphorous-containing waste acid in the present invention. It can be seen that the purity of the condensed aluminum phosphate products obtained by the preparation method of the present invention can reach 94.2% and above, and the highest can reach 96.7%. Among them, relative to the contents of phosphorus and aluminum in the raw materials, the recovery rate of phosphorus in the condensed aluminum phosphate products prepared in the present invention can reach more than 71%, and the highest can reach 91%, and the recovery rate of aluminum resources can reach more than 69%, and the highest can reach 90%.

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing condensed aluminum phosphate from phosphorous-containing waste acid, characterized in that, It includes the following steps: S1. Alkaline dissolution: Add the aluminum-containing sludge into dilute alkali solution, fully dissolve and react, and obtain the aluminum-containing mother liquor after pressure filtration; S2. Purification: Add an extractant to the phosphorus-containing waste acid, and separate the raffinate and the loaded organic phase by countercurrent forward extraction; Use water to carry out countercurrent back-extraction regeneration on the loaded organic phase, add a desulfurizing agent to the back-extract after separation, and obtain the purified phosphorus-containing waste acid after pressure filtration; S3. Synthesis: Supplement phosphoric acid to the purified phosphorus-containing waste acid, add the aluminum-containing mother liquor in S1, control the pH of the reaction solution to be 1.5 - 3.0, stir and react at 120 - 150 °C for 3 - 5 h, and obtain paste-like aluminum phosphate after pressure filtration; S4. Polycondensation: Dry the paste-like aluminum phosphate in S3 at a high temperature of 100 - 120 °C for 4 - 6 h, then raise the temperature to 300 - 400 °C for dehydration and polycondensation for 8 - 10 h, and pulverize to obtain condensed aluminum phosphate.

2. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as claimed in claim 1, wherein, The extractant in S2 is n-butanol.

3. The method for preparing condensed aluminum phosphate by using phosphorous-containing waste acid as described in claim 1, wherein The phase ratio of countercurrent forward extraction in S2 is O / A = 2 - 4.

4. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as claimed in claim 1, wherein The phase ratio of countercurrent back-extraction in S2 is O / A = 2 - 3.

5. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as claimed in claim 1, wherein The molar ratio of phosphoric acid in the reaction solution in S3 to Al2O3 in the aluminum-containing mother liquor is 2 - 3:

1.

6. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as described in claim 1, characterized in that, The mass concentration of the dilute alkali solution in S1 is 10% - 15%.

7. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as claimed in claim 6, wherein, The mass ratio of the aluminum-containing sludge to the dilute alkali solution added in S1 is 1:(0.8 - 1.2).

8. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as described in claim 1, characterized in that, The desulfurizing agent in S2 is barium carbonate or barium hydroxide.

9. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as claimed in claim 8, wherein The addition amount of the desulfurizer in S2 is the amount required to achieve a molar ratio of Ba 2+ to SO4 2- in the stripping solution of 1.0 - 1.1:

1.

10. The method for preparing condensed aluminum phosphate using phosphorous-containing waste acid as described in claim 1, characterized in that, The phosphoric acid content of the phosphorus-containing waste acid described in S2 is 10 - 20 wt%, the sulfuric acid content is 5 - 10 wt%, and the aluminum ion content is 1 - 5 wt%.

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