Method for preparing iron phosphate dihydrate from phosphoric acid pickling waste liquid

Abstract

The invention relates to a method for preparing iron phosphate dihydrate from phosphoric acid pickling waste liquid, in particular to the field of preparation of iron phosphate dihydrate, and the method comprises the following steps: carrying out adsorption treatment on the phosphoric acid pickling waste liquid, and carrying out solid-liquid separation to obtain an adsorbed liquid; adding an iron source into the adsorbed liquid, and then sequentially carrying out pH value adjustment and heat-preservation stirring reaction to obtain slurry; carrying out solid-liquid separation on the slurry, and sequentially pulping and spray-drying the obtained solid phase to obtain iron phosphate dihydrate; wherein the phosphoric acid pickling waste liquid comprises phosphoric acid, iron ions, a corrosion inhibitor and a wetting agent. According to the scheme provided by the invention, the phosphoric acid pickling waste liquid is subjected to a specific treatment process, so that the preparation of high-quality iron phosphate dihydrate is realized, and meanwhile, the particle size distribution uniformity of the obtained iron phosphate dihydrate is obviously improved under the action of the corrosion inhibitor and the wetting agent in the phosphoric acid pickling waste liquid.

Description

Technical Field

[0001] The invention relates to the field of preparation of ferric phosphate dihydrate, and in particular to a method for preparing ferric phosphate dihydrate by utilizing phosphoric acid pickling waste liquid. Background Art

[0002] At present, the process for preparing iron phosphate generally uses ferrous sulfate to prepare an iron salt solution, then mixes it with a phosphate solution, adjusts the pH, heats and ages it, and then uses deionized water to wash it to meet the standards. Different drying technologies are used to prepare the required iron phosphate products according to requirements. Alternatively, iron is used as the raw material, phosphoric acid is used to dissolve it, and then ammonia water, liquid alkali, etc. are used to adjust the pH, and then heats and ages it, and then uses deionized water to wash it to meet the standards. Different drying technologies are used to prepare the required iron phosphate products according to requirements.

[0003] For example, CN105895914A discloses a method for preparing iron phosphate dihydrate, which comprises adding 115-126 parts by weight of phosphoric acid to 400 parts by weight of deionized water to prepare a phosphoric acid solution, maintaining the solution temperature at 50-65°C, adding 56 parts by weight of reduced iron powder under stirring, reacting for 1-3 hours, adding the resulting product to a ball mill, and ball milling to obtain a ball-milled material; taking out the ball-milled material and placing it in a container, adding 56-68 parts by weight of hydrogen peroxide thereto, stirring evenly, and placing it in a reactor for treatment at a temperature of 60-140°C for a treatment time of 6-12 hours to obtain a reaction product; stirring and dispersing the reaction product evenly, and then spray drying it at 150-180°C to obtain iron phosphate dihydrate.

[0004] CN117105194A discloses a method for preparing high-purity ferric phosphate dihydrate and removing impurities, comprising:

[0005] Step S1, reacting the iron ore concentrate with pure water and acid to obtain acid leaching solution and acid leaching residue;

[0006] Step S2, subjecting the acid leaching solution and the phosphorus source to a homogeneous precipitation reaction at a certain temperature to synthesize ferric phosphate dihydrate;

[0007] Step S3, adding pure water to the ferric phosphate dihydrate for washing to obtain ferric phosphate dihydrate;

[0008] Step S4, reacting the above-mentioned ferric phosphate dihydrate with phosphoric acid of a certain concentration, filtering the solid-liquid mixture obtained after the reaction is completed, and obtaining high-purity ferric phosphate dihydrate.

[0009] However, the existing process for preparing ferric phosphate dihydrate still has the defects of complex preparation process, low purity of ferric phosphate dihydrate product and uneven particle size distribution of the product. Summary of the invention

[0010] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, so as to solve the defects of the process for preparing ferric phosphate dihydrate, such as complex preparation process, low purity of ferric phosphate dihydrate product and uneven product particle size distribution.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] The present invention provides a method for preparing ferric phosphate dihydrate by using phosphoric acid pickling waste liquid, the method comprising:

[0013] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0014] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0015] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate;

[0016] The phosphoric acid pickling waste liquid comprises phosphoric acid, iron ions, corrosion inhibitor and wetting agent.

[0017] The solution provided by the present invention realizes the preparation of high-quality ferric phosphate dihydrate by performing a specific treatment process on phosphoric acid pickling waste liquid, and at the same time, by utilizing the effects of corrosion inhibitors and wetting agents in the phosphoric acid pickling waste liquid, the uniformity of the particle size distribution of the obtained ferric phosphate dihydrate is significantly improved.

[0018] As a preferred technical solution of the present invention, the solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is (0.1-0.5) g / mL:100.

[0019] Preferably, the adsorbent used in the adsorption treatment comprises activated carbon and / or molecular sieve.

[0020] As a preferred technical solution of the present invention, the iron source includes iron salt.

[0021] Preferably, the iron salt comprises: one or a combination of at least two of ferric sulfate, ferric carbonate, ferric chloride or ferric nitrate.

[0022] As a preferred technical solution of the present invention, the amount of the iron source added is 40-60% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid.

[0023] As a preferred technical solution of the present invention, the pH value adjustment includes: adjusting the pH value of the solution to 5.8-6.2 using ferric hydroxide.

[0024] As a preferred technical solution of the present invention, the insulation temperature in the insulation stirring reaction is 50-80°C.

[0025] As a preferred technical solution of the present invention, the stirring rate in the heat-insulating stirring reaction is 40-90 r / min.

[0026] As a preferred technical solution of the present invention, the time of the heat-insulating stirring reaction is 4-20 hours.

[0027] As a preferred technical solution of the present invention, the slurrying includes: mixing the solid phase obtained by solid-liquid separation with a solvent to form a slurry.

[0028] Preferably, the solid mass percentage in the slurry obtained by beating is 40-60%.

[0029] As a preferred technical solution of the present invention, the feed rate of the spray drying is 50-200 L / h.

[0030] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0031] (1) The preparation of iron phosphate using phosphoric acid pickling wastewater as raw material can fully recover the iron and phosphorus resources in the wastewater.

[0032] (2) By adjusting the amount of iron salt and iron hydroxide added, the system reaches the optimal pH without introducing other impurities.

[0033] (3) The corrosion inhibitors and wetting agents originally present in the wastewater make the prepared iron phosphate product have uniform particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention provides a flowchart of a method for preparing ferric phosphate dihydrate by using phosphoric acid pickling waste liquid.

[0035] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0036] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0037] This embodiment provides a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid. The flow chart is as follows Figure 1 As shown, the method includes:

[0038] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0039] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0040] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate.

[0041] The phosphoric acid pickling waste liquid comprises phosphoric acid, iron ions, corrosion inhibitor and wetting agent.

[0042] In the present invention, the total mass percentage of the corrosion inhibitor and the wetting agent in the phosphoric acid pickling waste liquid is 0.2-1%, the phosphoric acid content is 15-20%, and the iron content is 3-5%.

[0043] In the present invention, the corrosion inhibitor is illustratively one of sodium silicate, sodium tripolyphosphate or POCA, or a combination of at least two thereof.

[0044] In the present invention, the wetting agent can be selected from one or a combination of at least two of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, polyoxyethylene fatty secondary alcohol ether, etc.

[0045] In the present invention, iron ions refer to trivalent iron ions unless otherwise specified.

[0046] Among them, the solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is (0.1-0.5):100, for example, it can be 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, 0.45:100 or 0.5:100, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0047] Wherein, the adsorbent used in the adsorption treatment includes activated carbon and / or molecular sieve.

[0048] Wherein, the iron source includes iron salt.

[0049] Wherein, the iron salt includes: one or a combination of at least two of ferric sulfate, ferric carbonate, ferric chloride or ferric nitrate.

[0050] Illustratively, the combination of iron salts includes a combination of iron sulfate and iron carbonate, a combination of iron carbonate and iron chloride, a combination of iron chloride and iron nitrate, and the like.

[0051] Wherein, the addition amount of the iron source is 40-60% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or 60%, etc., but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0052] The pH value adjustment includes: adjusting the pH value of the solution to 5.8-6.2 using ferric hydroxide, for example, it can be 5.8, 5.85, 5.9, 5.95, 6, 6.05, 6.1, 6.15 or 6.2, but is not limited to the listed values, and other values ​​not listed in this range also meet the requirements.

[0053] Wherein, the insulation temperature in the insulation stirring reaction is 50-80°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0054] Wherein, the stirring rate in the heat-insulating stirring reaction is 40-90r / min, for example, it can be 40r / min, 43r / min, 47r / min, 50r / min, 53r / min, 57r / min, 60r / min, 63r / min, 67r / min, 70r / min, 73r / min, 77r / min, 80r / min, 83r / min, 87r / min or 90r / min, but is not limited to the listed values, and other values ​​not listed in this range also meet the requirements.

[0055] The time for the heat-insulating stirring reaction is 4-20 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0056] The slurrying comprises: mixing the solid phase obtained by solid-liquid separation with a solvent to form a slurry.

[0057] Among them, the solvent in the pulping process includes water and / or ethanol and other commonly used solvents.

[0058] Among them, the solid mass percentage of the slurry obtained by beating is 40-60%, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or 60%, etc., but is not limited to the listed values, and other values ​​not listed in this range also meet the requirements.

[0059] Wherein, the feed rate of the spray drying is 50-200 L / h, for example, it can be 50 L / h, 60 L / h, 70 L / h, 80 L / h, 90 L / h, 100 L / h, 110 L / h, 120 L / h, 130 L / h, 140 L / h, 150 L / h, 160 L / h, 170 L / h, 180 L / h, 190 L / h or 200 L / h, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0060] In the present invention, the solid-liquid separation method includes pressure filtration, suction filtration, centrifugal separation and other methods for achieving solid-liquid separation in the art.

[0061] The slurry may be optionally washed with water during solid-liquid separation to purify the solid phase obtained by solid-liquid separation to remove impurities adhering to the surface.

[0062] Further, in order to illustrate the good quality of the ferric phosphate dihydrate prepared by the method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid provided by the present invention, an actual example is used for illustration, as follows:

[0063] Example 1

[0064] This embodiment provides a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, which is as follows:

[0065] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0066] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0067] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate;

[0068] The phosphoric acid pickling waste liquid comprises, by mass percentage, 16% phosphoric acid, 5% iron, 0.3% corrosion inhibitor (sodium silicate) and wetting agent (sodium dodecylbenzene sulfonate);

[0069] The solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 0.2:100 g / mL; the adsorbent used in the adsorption treatment is activated carbon;

[0070] The iron source is ferric sulfate; the amount of the iron source added is 50% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid;

[0071] The pH value adjustment comprises: adjusting the pH value of the solution to 6 using ferric hydroxide;

[0072] The insulation temperature in the insulation stirring reaction is 60° C.; the stirring rate in the insulation stirring reaction is 60 r / min; and the insulation stirring reaction time is 10 h;

[0073] The beating comprises: mixing the solid phase obtained by solid-liquid separation with solvent water to form a slurry; the solid mass percentage of the slurry obtained by the beating is 50%;

[0074] The feed rate of the spray drying was 100 L / h.

[0075] Example 2

[0076] This embodiment provides a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, which is as follows:

[0077] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0078] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0079] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate;

[0080] The phosphoric acid pickling waste liquid comprises, by mass percentage, 18% phosphoric acid, 4% iron, 0.3% corrosion inhibitor (sodium tripolyphosphate) and wetting agent (sodium lauryl sulfate);

[0081] The solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 0.3:100 g / mL; the adsorbent used in the adsorption treatment is activated carbon;

[0082] The iron source is ferric sulfate; the amount of the iron source added is 55% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid;

[0083] The pH value adjustment includes: adjusting the pH value of the solution to 6.1 using ferric hydroxide;

[0084] The insulation temperature in the insulation stirring reaction is 70° C.; the stirring rate in the insulation stirring reaction is 80 r / min; and the insulation stirring reaction time is 15 h;

[0085] The beating comprises: mixing the solid phase obtained by solid-liquid separation with solvent water to form a slurry; the solid mass percentage of the slurry obtained by the beating is 55%;

[0086] The feed rate of the spray drying was 150 L / h.

[0087] Example 3

[0088] This embodiment provides a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, which is as follows:

[0089] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0090] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0091] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate;

[0092] The phosphoric acid pickling waste liquid comprises, by mass percentage, 17% phosphoric acid, 5% iron, 0.4% corrosion inhibitor (sodium silicate and sodium tripolyphosphate) and wetting agent (polyoxyethylene fatty secondary alcohol ether);

[0093] The solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 0.1:100 g / mL; the adsorbent used in the adsorption treatment is activated carbon;

[0094] The iron source is ferric chloride; the amount of the iron source added is 40% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid;

[0095] The pH value adjustment includes: adjusting the pH value of the solution to 5.8 using ferric hydroxide;

[0096] The insulation temperature in the insulation stirring reaction is 50° C.; the stirring rate in the insulation stirring reaction is 90 r / min; and the insulation stirring reaction time is 20 h;

[0097] The beating comprises: mixing the solid phase obtained by solid-liquid separation with solvent water to form a slurry; the solid mass percentage of the slurry obtained by the beating is 60%;

[0098] The feed rate of the spray drying was 200 L / h.

[0099] Example 4

[0100] This embodiment provides a method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, which is as follows:

[0101] The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation;

[0102] Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry;

[0103] The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate;

[0104] The phosphoric acid pickling waste liquid comprises, by mass percentage, 15% phosphoric acid, 3% iron, 0.2% corrosion inhibitor (sodium silicate, sodium tripolyphosphate and POCA) and wetting agent (sodium dodecylbenzene sulfonate and sodium lauryl sulfate);

[0105] The solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 0.5:100 g / mL; the adsorbent used in the adsorption treatment is activated carbon;

[0106] The iron source is ferric nitrate; the amount of the iron source added is 60% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid;

[0107] The pH value adjustment includes: adjusting the pH value of the solution to 6.2 using ferric hydroxide;

[0108] The insulation temperature in the insulation stirring reaction is 80° C.; the stirring rate in the insulation stirring reaction is 40 r / min; and the insulation stirring reaction time is 4 h;

[0109] The beating comprises: mixing the solid phase obtained by solid-liquid separation with solvent water to form a slurry; the solid mass percentage of the slurry obtained by the beating is 40%;

[0110] The feed rate of the spray drying was 50 L / h.

[0111] Example 5

[0112] The only difference from Example 1 is that the solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 2:100 g / mL.

[0113] Example 6

[0114] The only difference from Example 1 is that the solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is 0.01:100 g / mL.

[0115] Example 7

[0116] The only difference from Example 1 is that the pH value of the solution after pH adjustment is 7.

[0117] Example 8

[0118] The only difference from Example 1 is that the pH value of the solution after pH adjustment is 4.

[0119] Example 9

[0120] The only difference from Example 1 is that no stirring is performed during the heat-insulating stirring reaction.

[0121] Example 10

[0122] The only difference from Example 1 is that the reaction was not stirred and insulated.

[0123] Embodiment 11

[0124] The only difference from Example 1 is that the phosphoric acid pickling waste liquid is replaced by waste liquid not containing sodium silicate.

[0125] Example 12

[0126] The only difference from Example 2 is that the phosphoric acid pickling waste liquid is replaced by a waste liquid that does not contain sodium tripolyphosphate.

[0127] Comparative Example 13

[0128] The only difference from Example 1 is that the phosphoric acid pickling waste liquid is replaced by a waste liquid that does not contain sodium dodecylbenzene sulfonate.

[0129] Comparative Example 14

[0130] The only difference from Example 2 is that the phosphoric acid pickling waste liquid is replaced by a waste liquid that does not contain sodium lauryl sulfate.

[0131] The ferric phosphate dihydrate obtained in the above example was subjected to purity analysis and particle size analysis, and the results are shown in Table 1 below.

[0132] Table 1

[0133] purity / % <![CDATA[Apparent density g / cm 3 > Example 1 99.65 1.47 Example 2 99.72 1.41 Example 3 99.58 1.29 Example 4 99.83 1.55 Example 5 99.32 1.14 Example 6 97.63 1.41 Example 7 87.26 1.23 Example 8 93.57 1.18 Example 9 95.59 1.26 Example 10 94.37 1.34 Embodiment 11 98.63 1.23 Example 12 98.48 1.22 Embodiment 13 98.55 1.27 Embodiment 14 98.77 1.21

[0134] As can be seen from Table 1, in the solution provided by the present invention, the preparation of high-quality ferric phosphate dihydrate is achieved by subjecting the phosphoric acid pickling waste liquid to a specific treatment process, and at the same time, the uniformity of the particle size distribution of the obtained ferric phosphate dihydrate is significantly improved by virtue of the effects of the corrosion inhibitor and wetting agent in the phosphoric acid pickling waste liquid.

[0135] It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0136] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0137] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0138] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing ferric phosphate dihydrate using phosphoric acid pickling waste liquid, characterized in that: The method comprises: The phosphoric acid pickling waste liquid is subjected to adsorption treatment, and the adsorbed liquid is obtained by solid-liquid separation; Adding an iron source to the adsorbed liquid, and then adjusting the pH value and performing heat preservation and stirring reactions in sequence to obtain a slurry; The slurry is subjected to solid-liquid separation, and the obtained solid phase is sequentially subjected to pulping and spray drying to obtain ferric phosphate dihydrate; The phosphoric acid pickling waste liquid comprises phosphoric acid, iron ions, corrosion inhibitor and wetting agent.

2. The method according to claim 1, characterized in that The solid-liquid ratio of the adsorbent to the phosphoric acid pickling waste liquid in the adsorption treatment is (0.1-0.5) g / mL: 100; Preferably, the adsorbent used in the adsorption treatment comprises activated carbon and / or molecular sieve.

3. The method according to claim 1 or 2, characterized in that The iron source includes an iron salt; Preferably, the iron salt comprises: one or a combination of at least two of ferric sulfate, ferric carbonate, ferric chloride or ferric nitrate.

4. The method according to any one of claims 1 to 3, characterized in that: The amount of the iron source added is 40-60% of the mass content of phosphoric acid in the phosphoric acid pickling waste liquid.

5. The method according to any one of claims 1 to 4, characterized in that: The pH value adjustment includes: adjusting the pH value of the solution to 5.8-6.2 using ferric hydroxide.

6. The method according to any one of claims 1 to 5, characterized in that: The insulation temperature during the insulation and stirring reaction is 50-80°C.

7. The method according to any one of claims 1 to 6, characterized in that: The stirring rate in the heat-insulating stirring reaction is 40-90 r / min.

8. The method according to any one of claims 1 to 7, characterized in that: The time of the heat preservation and stirring reaction is 4-20 hours.

9. The method according to any one of claims 1 to 8, characterized in that The slurrying comprises: mixing the solid phase obtained by solid-liquid separation with a solvent to form a slurry; Preferably, the mass percentage of solids in the slurry obtained by beating is 40-60%.

10. The method according to any one of claims 1 to 9, characterized in that: The feed rate of the spray drying is 50-200 L / h.

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