CN114671538A - Resource utilization method of phosphorus-containing wastewater generated by azoxystrobin intermediate - Google Patents

Abstract

The invention provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, which comprises the following steps: (1) adjusting the pH value of the phosphorus-containing wastewater to 2-8 to obtain adjusted wastewater; (2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then carrying out solid-liquid separation to obtain sodium chloride solid and sodium dihydrogen phosphate solution; (3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) to obtain a sodium hexametaphosphate product. The resource utilization method provided by the invention can realize the utilization of the phosphorus-containing wastewater generated by the azoxystrobin intermediate, and convert trisodium phosphate therein into sodium dihydrogen sulfate, so as to obtain a sodium hexametaphosphate product, and the resource utilization method has a simple process, and can ensure that the recovery rate of phosphorus in the phosphorus-containing wastewater is more than 95%.

Description

Resource utilization method of phosphorus-containing wastewater generated by azoxystrobin intermediate

Technical Field

The invention belongs to the technical field of environmental protection, relates to a wastewater treatment method, and particularly relates to a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate.

Background

The pyrimidine compounds have active molecular structures, are intermediates of a plurality of medicines and pesticides, and attract attention of broad scholars due to the important function of the pyrimidine compounds in the pesticide and medicine field. When the compound is used as a medical intermediate, the compound is mainly used for producing sulfonamides, and 4, 6-dichloropyrimidine is also an important intermediate for synthesizing sulfonamides and bactericide azoxystrobin.

The prior art has reported many processes for the preparation of 4, 6-dichloropyrimidine, the most common being: reacting 4, 6-dihydroxypyrimidine with tertiary amine such as triethylamine, pyridine, N-dimethylaniline and the like and phosphorus oxychloride at a certain temperature, distilling the obtained reaction mixture under reduced pressure, recovering the excessive phosphorus oxychloride, pouring into ice water, extracting with an organic solvent, drying and dehydrating, and recovering the organic solvent to obtain the 4, 6-dichloropyrimidine. Although the method can prepare 4, 6-dichloropyrimidine, a large amount of organic alkali is required in the preparation process, a large amount of liquid alkali is added for neutralization and recycling in the post-treatment process, and the treatment operation of the generated waste water and waste residues is very complicated and high in cost because the waste water contains a large amount of phosphoric acid and hydrochloric acid.

CN 1092646A discloses a preparation method of 4, 6-dichloropyridine, which does not use any organic alkali, but adds excessive phosphorus trichloride and chlorine gas in the reaction process, recovers phosphorus oxychloride and phosphorus trichloride after the reaction is finished, and carries out reduced pressure distillation to obtain the product. Although the method solves the problem of large alkali consumption, chlorine gas needs to be added at a higher temperature, the control is very difficult, and the use of phosphorus trichloride in the production process greatly increases the risk of the process.

According to the data, the phosphorus oxychloride process has the biggest problem that after the amine catalyst is recycled, the wastewater contains a large amount of trisodium phosphate and sodium chloride, the national emission requirement on phosphorus-containing wastewater is extremely strict, and the wastewater contains a large amount of sodium chloride and trisodium phosphate and cannot be separated.

Therefore, it is desirable to provide a method for recycling wastewater containing sodium chloride and trisodium phosphate.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, which can realize the utilization of the phosphorus-containing wastewater generated by the azoxystrobin intermediate and convert trisodium phosphate therein into sodium dihydrogen sulfate so as to obtain a sodium hexametaphosphate product, and the recovery rate of phosphorus is more than 95%.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, which comprises the following steps:

(1) adjusting the pH value of the phosphorus-containing wastewater to 2-8 to obtain adjusted wastewater;

(2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then carrying out solid-liquid separation to obtain sodium chloride solid and sodium dihydrogen phosphate solution;

(3) and (3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) to obtain a sodium hexametaphosphate product.

The phosphorus-containing wastewater generated by the azoxystrobin intermediate is phosphorus-containing wastewater obtained after catalyst recovery, contains a large amount of trisodium phosphate and sodium chloride, is directly discharged, easily causes environmental pollution, and causes waste of phosphorus resources. The pH value of the phosphorus-containing wastewater is adjusted to 2-8, and then the trisodium phosphate is converted into sodium dihydrogen phosphate by evaporation and concentration.

The solubility of the sodium dihydrogen phosphate in water at high temperature is extremely high, and the separation of the sodium dihydrogen phosphate and sodium chloride is easy to realize; sodium dihydrogen phosphate also reduces the solubility of sodium chloride in water at high temperatures. Therefore, the invention can obtain the sodium dihydrogen phosphate solution with less sodium chloride content through solid-liquid separation, thereby realizing the separation of the sodium chloride. Then, industrial-grade sodium hexametaphosphate can be obtained by calcining, and the recycling of phosphorus resources in the phosphorus-containing wastewater is realized.

The invention firstly adjusts the pH value of the phosphorus-containing wastewater to 2-8, such as 2, 3, 4, 5, 6, 7 or 8, but not limited to the cited values, and other values in the range of the values are also applicable; preferably 4 to 5.

Preferably, the phosphorus-containing wastewater in step (1) contains sodium chloride and trisodium phosphate.

Preferably, the concentration of sodium chloride in the phosphorus-containing wastewater of step (1) is 8-15 wt%, for example, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the concentration of trisodium phosphate in the phosphorus-containing wastewater of step (1) is 8-15 wt%, for example, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the pH value of the phosphorus-containing wastewater in the step (1) is more than 12, for example, 12, 12.5, 13, 13.5 or 14, but is not limited to the recited values, and other values in the range of the values not recited are also applicable.

Preferably, the step (1) uses an acid solution to adjust the pH of the phosphorus-containing wastewater.

Preferably, the acid solution comprises any one of hydrochloric acid, sulfuric acid or acetic acid or a combination of at least two of the same; typical but non-limiting combinations are hydrochloric acid and sulfuric acid, hydrochloric acid and acetic acid, acetic acid and sulfuric acid; hydrochloric acid is preferred.

Preferably, the hydrochloric acid has a concentration of 1 to 32% by weight, and may be, for example, 1%, 5%, 10%, 15%, 20%, 25%, 30% or 32% by weight, but is not limited to the recited values, and other values not recited within the numerical range are equally applicable; preferably 20 to 32 wt%.

In the present invention, the parameters for the evaporation concentration in step (2) are not specifically limited, and the concentration of sodium dihydrogen phosphate in the filtered sodium dihydrogen phosphate solution may be 68 wt% or more and the concentration of sodium chloride may be 0.5 wt% or less.

Preferably, the solid-liquid separation method in step (2) comprises filtration.

Preferably, the filtration temperature is 60-100 ℃, for example can be 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but not limited to the enumerated values, other non-enumerated values within the range of values are equally applicable; preferably 70-90 deg.c.

Preferably, the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 68 wt% or more, and the concentration of sodium chloride is 0.5 wt% or less.

Preferably, the temperature of the calcination in step (3) is 600-700 ℃, and may be, for example, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃ or 700 ℃, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

As a preferable technical solution of the resource utilization method of the present invention, the resource utilization method includes the steps of:

(1) adjusting the pH value of the phosphorus-containing wastewater to 2-8 by using an acid solution to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 8-15 wt%, the concentration of the trisodium phosphate is 8-15 wt%, and the pH value is more than 12;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at the temperature of 60-100 ℃ to obtain sodium chloride solid and sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is above 68 wt%, and the concentration of sodium chloride is below 0.5 wt%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at the temperature of 600 ℃ and 700 ℃ to obtain a sodium hexametaphosphate product.

The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.

Compared with the prior art, the invention has the beneficial effects that:

the pH value of the phosphorus-containing wastewater is adjusted to 2-8, and then trisodium phosphate is converted into sodium dihydrogen phosphate by evaporation and concentration; the solubility of the sodium dihydrogen phosphate in water at high temperature is extremely high, and the separation of the sodium dihydrogen phosphate and sodium chloride is easy to realize; sodium dihydrogen phosphate also reduces the solubility of sodium chloride in water at high temperatures. Therefore, the invention can obtain the sodium dihydrogen phosphate solution with less sodium chloride content through solid-liquid separation, thereby realizing the separation of the sodium chloride. Then, industrial-grade sodium hexametaphosphate can be obtained by calcining, so that the phosphorus resource in the phosphorus-containing wastewater can be recycled, and the recovery rate of phosphorus is over 95 percent.

Detailed Description

The technical solution of the present invention is further described below by way of specific embodiments.

Example 1

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using an acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 4 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 10 wt%, the concentration of the trisodium phosphate is 10 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 32 wt%;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at 70 ℃ to obtain sodium chloride solid and 50.79g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 68.9 wt%, the concentration of sodium chloride is 0.5 wt%, and the recovery rate of phosphorus is 95.64%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 650 ℃ to obtain a sodium hexametaphosphate product.

Example 2

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using an acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 5 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 10 wt%, the concentration of the trisodium phosphate is 10 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 32 wt%;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at 90 ℃ to obtain sodium chloride solid and 50.1g of sodium dihydrogen phosphate solution; the concentration of the sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 72 wt%, the concentration of the sodium chloride is 0.3 wt%, and the recovery rate of the phosphorus is 98.58%;

(3) and (3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at the temperature of 620 ℃ to obtain a sodium hexametaphosphate product.

Example 3

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) adjusting the pH value of 500g of phosphorus-containing wastewater to 5 by using an acid solution to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 10 wt%, the concentration of the trisodium phosphate is 10 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 32 wt%;

(2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then filtering at 80 ℃ to obtain sodium chloride solid and 50.5g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 71.5 wt%, the concentration of sodium chloride is 0.3 wt%, and the recovery rate of phosphorus is 98.68%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 680 ℃ to obtain a sodium hexametaphosphate product.

Example 4

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) adjusting the pH value of 500g of phosphorus-containing wastewater to 4.5 by using an acid solution to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 9 wt%, the concentration of the trisodium phosphate is 9 wt%, and the pH value is 13; the acid solution is hydrochloric acid with the concentration of 27 wt%;

(2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then filtering at 80 ℃ to obtain sodium chloride solid and 45.1g of sodium dihydrogen phosphate solution; the concentration of the sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 70.9 wt%, the concentration of the sodium chloride is 0.4 wt%, and the recovery rate of the phosphorus is 97.07%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 680 ℃ to obtain a sodium hexametaphosphate product.

Example 5

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 4.5 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 12 wt%, the concentration of the trisodium phosphate is 12 wt%, and the pH value is 14; the acid solution is hydrochloric acid with the concentration of 20 wt%;

(2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then filtering at 80 ℃ to obtain sodium chloride solid and 60.1g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 72.1 wt%, the concentration of sodium chloride is 0.3 wt%, and the recovery rate of phosphorus is 98.71%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 680 ℃ to obtain a sodium hexametaphosphate product.

Example 6

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using an acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 8 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 8 wt%, the concentration of the trisodium phosphate is 8 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 10 wt%;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at the temperature of 60 ℃ to obtain sodium chloride solid and 40.1g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 69.7 wt%, the concentration of sodium chloride is 0.5 wt%, and the recovery rate of phosphorus is 95.43%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 600 ℃ to obtain a sodium hexametaphosphate product.

Example 7

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using an acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 2 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 15 wt%, the concentration of the trisodium phosphate is 15 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 1 wt%;

(2) evaporating and concentrating the conditioning wastewater obtained in the step (1), and then filtering at 100 ℃ to obtain sodium chloride solid and 75.1g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 69.4 wt%, the concentration of sodium chloride is 0.2 wt%, and the recovery rate of phosphorus is 95.02%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 700 ℃ to obtain a sodium hexametaphosphate product.

Example 8

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, which is the same as that in the embodiment 1 except that the filtering is carried out at 50 ℃ in the step (2).

Due to the reduction of the filtration temperature, the reduction range of the solubility of sodium chloride is reduced, and the concentration of sodium chloride in the obtained sodium dihydrogen phosphate solution is 0.8 wt%, which affects the purity of the obtained sodium hexafluorophosphate product.

Example 9

The embodiment provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, which is the same as that in the embodiment 1 except that the filtering is carried out at 110 ℃ in the step (2).

Due to the excessive filtration temperature, there was a phenomenon of water evaporation during the filtration process, resulting in a decrease in the quality of the obtained sodium dihydrogen phosphate solution to 46.4g, a concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution of 72.1 wt%, and a recovery rate of phosphorus of 91.33%.

Comparative example 1

The comparative example provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) 500g of phosphorus-containing wastewater is evaporated and concentrated, wherein the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, the concentration of the sodium chloride is 10 wt%, the concentration of the trisodium phosphate is 10 wt%, and the pH value is 12; then filtering the mixture at 70 ℃ to obtain sodium chloride solid and 66g of sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 50.27 wt%, the concentration of sodium chloride is 10 wt%, and the recovery rate of phosphorus is 90.68%;

(2) calcining the sodium dihydrogen phosphate solution obtained in the step (1) at 650 ℃ to obtain a sodium hexametaphosphate product.

The purity of the sodium hexametaphosphate obtained was greatly reduced compared to example 1 due to the higher concentration of sodium chloride in the sodium dihydrogen phosphate solution.

Comparative example 2

The comparative example provides a resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate, wherein the azoxystrobin intermediate is 4, 6-dichloropyridine, and the phosphorus-containing wastewater is 4, 6-dichloropyridine wastewater after catalyst recovery; the resource utilization method comprises the following steps:

(1) using an acid solution to adjust the pH value of 500g of phosphorus-containing wastewater to 1 to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 10 wt%, the concentration of the trisodium phosphate is 10 wt%, and the pH value is 12; the acid solution is hydrochloric acid with the concentration of 32 wt%;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at 70 ℃ to obtain sodium chloride solid and 50.79g of sodium dihydrogen phosphate solution, wherein the pH value of the sodium dihydrogen phosphate solution is adjusted to be consistent with that of the sodium dihydrogen phosphate solution in the example 1; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 68.9 wt%, the concentration of sodium chloride is 0.5 wt%, and the recovery rate of phosphorus is 95.64%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 650 ℃ to obtain a sodium hexametaphosphate product.

Because the pH value of the wastewater is too low, the pH value of the sodium dihydrogen phosphate solution needs to be adjusted back, and the economical efficiency of the resource utilization method is influenced.

In conclusion, the pH value of the phosphorus-containing wastewater is adjusted to 2-8, and then the trisodium phosphate is converted into sodium dihydrogen phosphate by evaporation and concentration; the solubility of the sodium dihydrogen phosphate in water at high temperature is extremely high, and the separation of the sodium dihydrogen phosphate and sodium chloride is easy to realize; sodium dihydrogen phosphate also reduces the solubility of sodium chloride in water at high temperatures. Therefore, the invention can obtain the sodium dihydrogen phosphate solution with less sodium chloride content through solid-liquid separation, thereby realizing the separation of the sodium chloride. Then, industrial-grade sodium hexametaphosphate can be obtained by calcining, so that the recycling of phosphorus resources in the phosphorus-containing wastewater is realized, and the recovery rate of phosphorus is over 95 percent.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A resource utilization method of phosphorus-containing wastewater generated by an azoxystrobin intermediate is characterized by comprising the following steps:

(1) adjusting the pH value of the phosphorus-containing wastewater to 2-8 to obtain adjusted wastewater;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then carrying out solid-liquid separation to obtain sodium chloride solid and sodium dihydrogen phosphate solution;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) to obtain a sodium hexametaphosphate product.

2. The resource utilization method according to claim 1, wherein the phosphorus-containing wastewater in step (1) contains sodium chloride and trisodium phosphate.

3. The resource utilization method according to claim 2, wherein the concentration of sodium chloride in the phosphorus-containing wastewater in the step (1) is 8-15 wt%;

preferably, the concentration of trisodium phosphate in the phosphorus-containing wastewater in the step (1) is 8-15 wt%.

4. A resource utilization method according to claim 2 or 3, wherein the pH value of the phosphorus-containing wastewater in the step (1) is 12 or more;

preferably, the pH value of the phosphorus-containing wastewater is adjusted to 4-5 in the step (1).

5. The resource utilization method according to any one of claims 1 to 4, wherein the pH value of the phosphorus-containing wastewater is adjusted by using an acid solution in the step (1);

preferably, the acid solution comprises any one of hydrochloric acid, sulfuric acid or acetic acid or a combination of at least two of the same; preferably hydrochloric acid;

preferably, the concentration of the hydrochloric acid is 1 to 32 wt%, preferably 20 to 32 wt%.

6. The resource utilization method according to any one of claims 1 to 5, wherein the solid-liquid separation method of step (2) includes filtration.

7. The resource utilization method according to claim 6, wherein the temperature of the filtration is 60 to 100 ℃, preferably 70 to 90 ℃.

8. A resource utilization method according to any one of claims 1 to 7, wherein the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is 68 wt% or more, and the concentration of sodium chloride is 0.5 wt% or less.

9. The resource utilization method as claimed in any one of claims 1 to 8, wherein the temperature of the calcination in step (3) is 600-700 ℃.

10. The resource utilization method according to any one of claims 1 to 9, characterized by comprising the steps of:

(1) adjusting the pH value of the phosphorus-containing wastewater to 2-8 by using an acid solution to obtain adjusted wastewater; the phosphorus-containing wastewater contains sodium chloride and trisodium phosphate, wherein the concentration of the sodium chloride is 8-15 wt%, the concentration of the trisodium phosphate is 8-15 wt%, and the pH value is more than 12;

(2) evaporating and concentrating the adjusted wastewater obtained in the step (1), and then filtering at the temperature of 60-100 ℃ to obtain sodium chloride solid and sodium dihydrogen phosphate solution; the concentration of sodium dihydrogen phosphate in the sodium dihydrogen phosphate solution is above 68 wt%, and the concentration of sodium chloride is below 0.5 wt%;

(3) calcining the sodium dihydrogen phosphate solution obtained in the step (2) at 600-700 ℃ to obtain a sodium hexametaphosphate product.