Method for preparing crystalline aluminum phosphate using aluminum material polishing waste liquid

Abstract

This invention discloses a method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid, comprising the following steps: Step S1. Adding water and alkali to the aluminum polishing waste liquid, adjusting the pH to 2-5, to obtain a mixed solution; Step S2. Taking the mixed solution obtained in Step S1, filtering, to obtain an amorphous precipitate; Step S3. Taking the precipitate from Step S2, washing, to obtain a washed precipitate; Step S4. Adding water to the washed precipitate from Step S3 and transferring it to a hydrothermal reactor for crystallization, to obtain crude aluminum phosphate; Step S5. Taking the crude aluminum phosphate from Step S4, filtering, washing, and drying, to obtain crystalline aluminum phosphate; wherein, in Step S4, the crystallization temperature is 160-210℃, and the crystallization time is not less than 3 hours. This method is simple, easy to operate, and the reaction conditions are easy to control. It not only solves the environmental problems encountered in the chemical polishing process of aluminum materials, but also improves the industrial value of aluminum polishing waste liquid.

Description

Technical Field

[0001] This invention relates to a method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid, specifically a method for preparing crystalline aluminum phosphate from aluminum and phosphorus in aluminum chemical polishing waste liquid, belonging to the fields of environmental protection, wastewater treatment, and resource recycling technology. Background Technology

[0002] Aluminum is widely used in aerospace, defense, transportation, construction, and communications due to its various excellent properties. Before use, polishing is often performed to improve its surface smoothness and corrosion resistance. Chemical polishing solutions composed of phosphoric acid and a certain proportion of sulfuric acid can lead to the accumulation of aluminum ions over long-term use. When the concentration reaches a certain level, it can no longer be used and becomes polishing waste liquid. Its main components are phosphoric acid, sulfuric acid, and aluminum ions, and it is highly corrosive, belonging to HW17 category in the "National Hazardous Waste List." Due to its large volume and strong corrosiveness, it is an environmental problem that the aluminum chemical polishing industry urgently needs to solve. Traditional treatment involves neutralization with alkali (such as lime or sodium hydroxide) before discharge. This method consumes large amounts of alkali, generates large amounts of phosphorus-containing sludge that pose a risk of secondary pollution, and has low added value, resulting in resource waste.

[0003] Aluminum phosphate is commonly used in glass production as a flux, ceramic binder, high-temperature and corrosion-resistant coating, and as an additive in special cements and other materials.

[0004] Since aluminum polishing waste liquid contains a large amount of aluminum and phosphorus, and aluminum phosphate has high industrial value, preparing aluminum phosphate from aluminum polishing waste liquid can solve environmental problems and improve the industrial value of aluminum polishing waste liquid.

[0005] Existing technology discloses a method for recycling waste acid from aluminum profile chemical polishing tanks. In this process, the waste acid is diluted, separated into solid and liquid components, and heated to produce aluminum phosphate. Aluminum phosphate seed crystals are then added to induce crystallization, resulting in aluminum phosphate precipitate. However, the pH value of the heating reaction is still less than 1, indicating excessive acidity. This results in a significant amount of aluminum ions remaining in the waste acid, preventing separation and leading to a low yield of aluminum phosphate. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing method of preparing aluminum phosphate from aluminum polishing waste liquid with low yield, and to provide a method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid, which can produce high-purity crystalline aluminum phosphate with a high recovery rate.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid includes the following steps:

[0009] Step S1. Add water and alkaline solution to the aluminum polishing waste liquid, adjust the pH to 2-5, and obtain a mixed solution;

[0010] Step S2. Take the mixture obtained in step S1, filter it, and obtain an amorphous precipitate;

[0011] Step S3. Take the precipitate from step S2, wash it, and obtain the washed precipitate;

[0012] Step S4. After washing the precipitate in step S3, add water and transfer it to a hydrothermal reactor for crystallization to obtain crude aluminum phosphate.

[0013] Step S5. Take the crude aluminum phosphate from step S4, filter, wash, and dry to obtain crystalline aluminum phosphate;

[0014] In step S4, the crystallization temperature is 160-210℃ and the crystallization time is no less than 3 hours.

[0015] In step S1 of this invention, adjusting the pH value by adding alkali solution allows for a higher pH level compared to direct dilution with water. This enables more aluminum ions to separate from the waste acid, thus increasing the yield of aluminum phosphate. In step S1, if the pH is too low, crystalline aluminum phosphate cannot be produced.

[0016] In step S4 of this invention, the amorphous precipitate after cleaning is directly crystallized, which transforms aluminum phosphate from an amorphous state to a crystalline state, thereby improving the purity of aluminum phosphate.

[0017] Compared to existing technologies that require the use of aluminum phosphate seeds or other induced crystallization methods, the method of this invention does not require the addition of seeds, thus offering the advantage of lower cost.

[0018] Moreover, in step S4 of the present invention, crystalline aluminum phosphate can be obtained at a crystallization temperature of 160-210°C, without the need for a higher crystallization temperature.

[0019] If the crystallization temperature is too low, the purity of the prepared crystalline aluminum phosphate will be significantly reduced, failing to meet the purity requirements of crystalline aluminum phosphate.

[0020] If the crystallization time is too short, some of the prepared crystalline aluminum phosphate will contain water of crystallization, which will reduce the purity of the crystalline aluminum phosphate and fail to meet the purity requirements.

[0021] The method of this invention is simple, easy to operate, and the reaction conditions are easy to control. It not only solves the environmental problems encountered in the surface treatment of aluminum materials, but also turns waste into treasure and improves the industrial value of aluminum polishing waste liquid.

[0022] Preferably, in step S1, the alkaline solution is one or more of ammonia, sodium hydroxide, or potassium hydroxide.

[0023] Compared to other high-valence metal alkaline solutions, ammonia, sodium hydroxide, or potassium hydroxide solutions do not form insoluble salts with sulfuric acid or phosphoric acid, which is beneficial for improving purity.

[0024] Preferably, in step S1, the pH is adjusted to 2.5-3.5.

[0025] More preferably, in step S1, the pH is adjusted to 2.8-3.

[0026] Preferably, in step S4, the crystallization temperature is 170-200℃.

[0027] A higher crystallization temperature is more conducive to removing the water of crystallization from aluminum phosphate crystals, thereby improving the purity of crystalline aluminum phosphate.

[0028] More preferably, in step S4, the crystallization temperature is 175-200℃.

[0029] More preferably, in step S4, the crystallization temperature is 175-185℃.

[0030] Preferably, in step S4, the crystallization time is 3-96 hours.

[0031] Preferably, in step S1, the main component of the aluminum polishing waste liquid is Al. 3+ H2SO4, H3PO4, of which Al 3+ The concentration is 20-50 g / L, the concentration of H2SO4 is 80-200 g / L, and the concentration of H3PO4 is 200-270 g / L.

[0032] Preferably, in step S4, the filling degree of the hydrothermal reactor is 50-85%.

[0033] More preferably, in step S4, the filling degree of the hydrothermal reactor is 70-80%.

[0034] A higher filling density in the hydrothermal reactor is more conducive to improving purity and reducing costs.

[0035] Preferably, in step S1, the reaction time is not less than 0.5 h.

[0036] Preferably, in step S1, the reaction time is 0.5 to 3 hours.

[0037] Preferably, in step S3, the cleaning conditions are that the water is rinsed with deionized water at least twice.

[0038] Preferably, in step S5, the drying temperature is 30-110℃.

[0039] More preferably, in step S5, the drying temperature is 100-105°C.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) The method of preparing crystalline aluminum phosphate from aluminum polishing waste liquid of the present invention uses aluminum polishing waste liquid to prepare high-purity crystalline aluminum phosphate, which solves the problem of difficult treatment of aluminum polishing waste liquid and realizes the transformation of waste into treasure. In actual production process, the aluminum ion content of aluminum polishing waste liquid is 20-50 / L, and 70-90% of aluminum can be recovered in the preparation of aluminum phosphate. The purity of crystalline aluminum phosphate exceeds 95%.

[0042] (2) The method of the present invention provides a new way to prepare high-purity crystalline aluminum phosphate simply by using aluminum polishing waste liquid as raw material. In the preparation process of high-purity crystalline aluminum phosphate, the original aluminum and phosphorus in the waste liquid are utilized, thus saving costs. Attached Figure Description

[0043] Figure 1 These are the X-ray diffraction (XRD) patterns of crystalline aluminum phosphate prepared in Examples 1-4 of this invention.

[0044] Figure 2 These are scanning electron microscope (SEM) images of the crystalline aluminum phosphate prepared in Examples 1-4 of this invention. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0046] Example 1

[0047] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0048] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0049] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 0.5 hours, filter, and obtain the precipitate for later use;

[0050] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0051] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0052] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180℃ for 96 hours to obtain crude aluminum phosphate.

[0053] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0054] Example 2

[0055] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0056] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 41.28g / L, H2SO4 122.84g / L, H3PO4249.90g / L;

[0057] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 0.5 hours, filter, and obtain the precipitate for later use;

[0058] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0059] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 80%.

[0060] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 200℃ for 48 hours to obtain crude aluminum phosphate.

[0061] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 105℃ to obtain crystalline aluminum phosphate.

[0062] Example 3

[0063] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0064] Step S1. The waste liquid from aluminum polishing is mainly composed of Al. 3+ 42.63g / L, H2SO4 182.28g / L, H3PO4253.82g / L;

[0065] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 2.8, react for 1 hour, filter, and obtain the precipitate for later use;

[0066] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0067] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0068] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180℃ for 48 hours to obtain crude aluminum phosphate.

[0069] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 105℃ to obtain crystalline aluminum phosphate.

[0070] Example 4

[0071] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0072] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 43.17g / L, H2SO4 155.82g / L, H3PO4288.12g / L;

[0073] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 3 hours, filter, and obtain the precipitate for later use;

[0074] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0075] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0076] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 170℃ for 48 hours to obtain crude aluminum phosphate.

[0077] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 105℃ to obtain crystalline aluminum phosphate.

[0078] Example 5

[0079] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0080] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0081] Take the waste liquid from aluminum polishing, add water and sodium hydroxide to neutralize it, adjust the final pH to 3.0, react for 0.5 h, filter, and obtain the precipitate for later use;

[0082] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0083] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0084] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180℃ for 96 hours to obtain crude aluminum phosphate.

[0085] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0086] Unlike Example 1, in step S1, water and sodium hydroxide are added to adjust the pH to 3.

[0087] Example 6

[0088] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0089] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0090] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 0.5 hours, filter, and obtain the precipitate for later use;

[0091] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0092] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 50%.

[0093] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180℃ for 96 hours to obtain crude aluminum phosphate.

[0094] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0095] Unlike Example 1, in step S3, the hydrothermal reactor is filled to 50%.

[0096] The rest is the same as in Example 1, and will not be repeated here.

[0097] Example 7

[0098] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0099] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0100] Take the aluminum polishing waste liquid from step S1, add water and ammonia to neutralize it, adjust the endpoint pH to 3.0, react for 0.5 h, filter, and obtain the precipitate for later use;

[0101] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0102] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0103] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180°C for 3 hours to obtain crude aluminum phosphate.

[0104] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0105] Unlike Example 1, in step S4, the crystallization time is 3 hours.

[0106] The rest is the same as in Example 1, and will not be repeated here.

[0107] Comparative Example 1

[0108] A method for treating waste liquid from aluminum polishing specifically includes the following steps:

[0109] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 41.55g / L, H2SO4 124.65g / L, H3PO4251.06g / L;

[0110] Step S2. Take the aluminum polishing waste liquid from step S1, add water and ammonia to neutralize it, adjust the endpoint pH to 1.0, react for 1 hour, and no precipitate is produced.

[0111] Comparative Example 2

[0112] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0113] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0114] Take the aluminum polishing waste liquid from step S1, add water and ammonia water to neutralize it, adjust the endpoint pH to 6.0, react for 0.5 h, filter, and obtain the precipitate for later use;

[0115] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0116] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0117] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180℃ for 96 hours to obtain crude aluminum phosphate.

[0118] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0119] Unlike Example 1, in step S1, the pH is adjusted to 6.

[0120] The rest is the same as in Example 1, and will not be repeated here.

[0121] Comparative Example 3

[0122] A method for treating waste liquid from aluminum polishing specifically includes the following steps:

[0123] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.05g / L, H2SO4 159.41g / L, H3PO4267.12g / L;

[0124] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 1 hour, filter, and obtain the precipitate for later use;

[0125] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0126] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a flask with a filling degree of 70%.

[0127] Step S4. In step S3, the flask is refluxed at 100°C and atmospheric pressure for 96 hours to obtain the crude product;

[0128] Step S5. Take the crude product from step S4, filter and wash it, and dry it at 105℃. The resulting product is still an amorphous substance.

[0129] Comparative Example 4

[0130] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0131] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0132] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 0.5 hours, filter, and obtain the precipitate for later use;

[0133] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0134] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0135] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 150°C for 96 hours to obtain crude aluminum phosphate.

[0136] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0137] Unlike Example 1, in step S4, the crystallization temperature is 150°C.

[0138] The rest is the same as in Example 1, and will not be repeated here.

[0139] Comparative Example 5

[0140] A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid specifically includes the following steps:

[0141] Step S1. The main component of the aluminum polishing waste liquid is Al. 3+ 42.36g / L, H2SO4 117.56g / L, H3PO4247.94g / L;

[0142] Take the waste liquid from aluminum polishing, add water and ammonia to neutralize it, adjust the final pH to 3.0, react for 0.5 hours, filter, and obtain the precipitate for later use;

[0143] Step S2. Take the precipitate from step S1 and wash it with water three times to obtain the washed precipitate;

[0144] Step S3. Add water to the precipitate after washing in step S2 and transfer it to a hydrothermal reactor with a filling degree of 70%.

[0145] Step S4. In step S3, the hydrothermal reactor is used for crystallization at 180°C for 1 hour to obtain crude aluminum phosphate.

[0146] Step S5. Take the crude aluminum phosphate from step S4, filter and wash it, and dry it at 100℃ to obtain crystalline aluminum phosphate.

[0147] Unlike Example 1, in step S4, the crystallization time is 1 hour.

[0148] The rest is the same as in Example 1, and will not be repeated here.

[0149] Performance testing

[0150] Figure 1 (1) to (4) are the X-ray diffraction (XRD) patterns of crystalline aluminum phosphate prepared in Examples 1-4 of this invention, respectively. Figure 1 It can be seen that the present invention can obtain crystalline aluminum phosphate with sharp diffraction peaks, no impurity peaks, and high purity.

[0151] Figure 2 Images (1) to (4) are, respectively, scanning electron microscope (SEM) images of crystalline aluminum phosphate prepared in Examples 1-4 of this invention. Figure 2 As can be seen, the crystal surface is smooth and intact, with no other crystals present.

[0152] The method for testing the purity of crystalline aluminum phosphate is as follows:

[0153] wt(AlPO4)=wt(Al2O3)+wt(P2O5)

[0154] The wt(Al2O3) value was calculated by determining the aluminum content in the sample using EDTA back titration.

[0155] The phosphorus content in the sample was calculated by determining the phosphorus content in the wt(P2O5) using the quinomolybdicone gravimetric method.

[0156] Where wt is the mass fraction, %.

[0157] The test method for aluminum ion recovery rate is as follows:

[0158]

[0159] The purity of the crystalline aluminum phosphate in each embodiment is shown in Table 1:

[0160] Table 1

[0161]

[0162] The purity of the crystalline aluminum phosphate in each comparative example is shown in Table 2:

[0163] Table 2

[0164] Test performance Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 purity(%) - 80.16 - 87.09 92.86 Recovery rate (%) - 89.63 - 81.53 82.26

[0165] As can be seen from Examples 1 to 7, the method for preparing crystalline aluminum phosphate using aluminum polishing waste liquid of the present invention solves the problem of difficult treatment of aluminum polishing waste liquid and realizes the transformation of waste into treasure. In the actual production process, the aluminum ion content of aluminum polishing waste liquid is 20-50 / L, and the crystalline aluminum phosphate prepared can recover 70-90% of the aluminum, and the purity of the crystalline aluminum phosphate exceeds 95%.

[0166] As can be seen from the examples and Comparative Example 1, no precipitate was produced in Comparative Example 1, indicating that the pH was too low to produce aluminum phosphate.

[0167] As can be seen from the examples and Comparative Example 2, in Comparative Example 2, the purity of aluminum phosphate was too low, indicating that the pH was too high and the purity of aluminum phosphate was too low, which could not meet the purity requirements for crystalline aluminum phosphate.

[0168] As can be seen from Examples and Comparative Example 3, the product is an amorphous material, which indicates that amorphous aluminum phosphate cannot be crystallized hydrothermally under normal pressure.

[0169] As can be seen from the examples and Comparative Example 4, in step S4, the crystallization temperature was too low, and some of the generated aluminum phosphate contained water of crystallization. The purity of the aluminum phosphate obtained was only 87.09%, which could not meet the purity requirements for crystalline aluminum phosphate.

[0170] As can be seen from the examples and comparative example 5, in step S4, the crystallization time is too short, and some of the generated aluminum phosphate also contains water of crystallization. The purity of the aluminum phosphate obtained is only 92.86%, which cannot meet the purity requirements for crystalline aluminum phosphate.

[0171] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid, characterized in that, Includes the following steps: Step S1. Add water and alkaline solution to the aluminum polishing waste liquid, adjust the pH to 2-5, and obtain a mixed solution; Step S2. Take the mixture obtained in step S1, filter it, and obtain an amorphous precipitate; Step S3. Take the precipitate from step S2, wash it, and obtain the washed precipitate; Step S4. After washing the precipitate in step S3, add water and transfer it to a hydrothermal reactor for crystallization to obtain crude aluminum phosphate. Step S5. Take the crude aluminum phosphate from step S4, filter, wash, and dry to obtain crystalline aluminum phosphate; In step S1, the main component of the aluminum polishing waste liquid is Al. 3+ H2SO4, H3PO4, of which Al 3+ The concentration is 20-50 g / L, the concentration of H2SO4 is 80-200 g / L, and the concentration of H3PO4 is 200-270 g / L; In step S4, the crystallization temperature is 160-210℃ and the crystallization time is 3-96h.

2. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S1, the alkaline solution is one or more of ammonia, sodium hydroxide, or potassium hydroxide.

3. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S1, the pH is adjusted to 2.5-3.

5.

4. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S4, the crystallization temperature is 170-200℃.

5. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 4, characterized in that, In step S4, the crystallization temperature is 175-185℃.

6. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S4, the filling degree of the hydrothermal reactor is 50-85%.

7. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S1, the reaction time is not less than 0.5 hours.

8. The method for preparing crystalline aluminum phosphate from aluminum polishing waste liquid as described in claim 1, characterized in that, In step S5, the drying temperature is 30-110℃.

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