Method for preparing pure phosphorus-containing solution based on purification of sludge gasification slag pickle liquor

Abstract

The invention discloses a method for preparing a pure phosphorus-containing solution based on purification of sludge gasification slag pickle liquor, and belongs to the technical field of sludge treatment. An acid solvent is added into the sludge gasification slag obtained after ore grinding for dissolution, stirring and acid leaching are conducted, and mixed slurry is obtained; carrying out solid-liquid separation on the mixed slurry, and taking phosphorus-containing supernate; diluting the phosphorus-containing supernate, adding strong acidic cationic resin after dilution, and purifying at normal temperature; when the acid solvent is industrial waste acid, strongly acidic cationic resin is added into the feed liquid obtained after the first purification for secondary adsorption and purification; and after purification, carrying out solid-liquid separation on the obtained feed liquid to obtain a pure phosphorus-containing solution. The purification method provided by the invention is simple in process, good in selectivity and low in phosphorus loss, and provides a high-quality raw material solution guarantee for preparing a phosphorus product with high purity and high additional value from the sludge gasification slag.

Description

A method for preparing pure phosphorus-containing solution based on acid leaching liquor from sludge gasification residue. Technical Field 1. Technical Field:

[0001] This invention relates to the field of sludge treatment technology, and specifically to a method for preparing a pure phosphorus-containing solution based on the purification of acid leaching solution from sludge gasification residue. Background Technology II. Background Technology:

[0002] With the widespread adoption of sludge gasification technology, the production of its byproduct—gasification slag—is increasing daily. Gasification slag is rich in phosphorus and is considered a potential "urban phosphate mine," playing a crucial role in alleviating the phosphorus resource crisis. However, gasification slag has a complex composition and contains certain amounts of iron (Fe), aluminum (Al), and various heavy metal impurities, posing environmental risks when directly utilized. Currently, acid leaching is widely used to extract phosphorus from gasification slag due to its high efficiency and low cost, transferring the vast majority of phosphorus to the liquid phase.

[0003] Acid leaching can transfer phosphorus to the liquid phase, but the resulting acid leaching solution has a complex composition, including a high concentration of Fe3+. + The presence of cations such as Al3+ can severely interfere with the purification and high-value conversion of phosphorus. For example, during the subsequent precipitation synthesis of calcium phosphate, they compete with phosphate ions for reaction, generating amorphous Fe / Al phosphate coprecipitates, leading to problems such as low purity, poor crystal form, and difficulty in increasing the added value of the target product.

[0004] Currently, the purification of phosphorus-containing solutions mostly employs chemical precipitation methods (such as adjusting pH to form hydroxide precipitates). However, this method has the following drawbacks: it generates a large amount of sludge containing heavy metals, causing secondary pollution; the precipitation process entrains or coats some phosphorus, leading to phosphorus loss; the operation steps are cumbersome, requiring precise pH control, and it is easy to introduce new impurities, making it difficult to selectively remove specific ions, resulting in limited impurity removal efficiency. Therefore, developing a purification method that can efficiently and selectively remove Fe, Al, and heavy metal ions from the acid leaching liquid of sludge gasification residue, while maximizing the retention of phosphorus and avoiding secondary pollution, has become a key technological bottleneck for achieving its high-value resource recovery.

[0005] Currently, there are also patent literature reports on sludge gasification slag treatment technology, such as: 1. Patent application CN202411219700.X discloses a method for recovering and utilizing phosphorus from sludge gasification slag. In this method, the sludge gasification slag is acid-leached using a dilute sulfuric acid solution. This effectively prevents the leaching of other impurities while extracting phosphorus, resulting in high extraction efficiency and ensuring the purity of the obtained struvite product. However, the purity of the product prepared by this process is limited, and it contains a certain amount of impurity elements, limiting its application scenarios. 2. Patent application CN 202511208828.0 discloses a method for resource utilization of sludge gasification slag. In this method, municipal sludge gasification residue is pulverized and then acid-leached to obtain an acid leaching solution and acid leaching residue. Iron in the acid leaching solution is recovered, while the acid leaching residue is subjected to alkaline leaching. Under alkaline conditions, a calcium source is added to the alkaline leaching solution, resulting in calcium phosphate precipitation and recovery of iron from the alkaline leaching separation solution. Calcium ion solution is generated during both the iron recovery from the acid leaching solution and the calcium phosphate refining process, and can be used as a calcium source for comprehensive utilization. However, this process has limited separation principle and selectivity, a complex process flow, high reagent consumption, and the purity and recovery rate of the obtained products are mutually restrictive, placing considerable pressure on waste and wastewater treatment. III. Summary of the Invention:

[0006] The technical problem this invention aims to solve is: addressing the environmental impact of sludge gasification slag stockpiling, and the severe interference from impurity ions in existing acid leaching recovery processes, which affects the synthesis and purity of value-added products. This invention provides a method for purifying sludge gasification slag acid leaching solution to prepare a pure phosphorus-containing solution. This invention is a simple, selective, and low-phosphorus-loss purification method, providing a high-quality feedstock for the preparation of high-purity, high-value-added phosphorus products from sludge gasification slag.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing a pure phosphorus-containing solution based on the purification of acid leaching liquor from sludge gasification residue, the method comprising the following steps:

[0009] a. Place the sludge gasification residue after grinding in a container, then add acid solvent to dissolve and stir. After stirring and acid leaching, a mixed slurry is obtained.

[0010] b. Perform solid-liquid separation on the obtained mixed slurry and take the phosphorus-containing supernatant;

[0011] c. The phosphorus-containing supernatant is diluted and pretreated, and then purified by adding a strong acidic cation exchange resin at room temperature.

[0012] d. When the acid solvent in step a is industrial waste acid, add an equal amount of strong acid cation exchange resin to the purified liquid obtained in step c, and perform secondary adsorption purification at room temperature.

[0013] e. After purification, the liquid obtained in step c or step d is subjected to solid-liquid separation to obtain a pure phosphorus-containing solution.

[0014] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching solution of sludge gasification residue, the particle size of the sludge gasification residue after grinding in step a is ≥88.6% -200 mesh.

[0015] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching solution of sludge gasification residue, the acid solvent in step a is sulfuric acid, hydrochloric acid or industrial waste acid; the concentration of the acid solvent is 0.2-1.0 mol / L; and the liquid-to-solid ratio is controlled to be 10-50 ml / g when adding the acid solvent.

[0016] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching liquid of sludge gasification residue, the acid leaching time in step a is 6-10 h.

[0017] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching liquid of sludge gasification residue, the phosphorus-containing supernatant in step c is diluted by a factor of 5 to 10.

[0018] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching liquid of sludge gasification residue, the strong acid cation exchange resin in step c is a 732 type strong acid cation exchange resin; the mass ratio of the strong acid cation exchange resin to the sludge gasification residue is 1 to 5:1, and the purification time is 1 to 4 hours.

[0019] According to the above method for preparing a pure phosphorus-containing solution based on the acid leaching liquid of sludge gasification residue, the time for the secondary adsorption purification in step d is 1 to 3 hours.

[0020] The technical solution of this invention is for the detection of ions in solution, and ICP-OES is used for the determination. The results are all measured after dilution.

[0021] The positive and beneficial effects of this invention are:

[0022] 1. The technical solution of this invention achieves "precise capture" of target impurity ions and "efficient release" of target phosphorus elements from complex systems through the synergistic combination of the technical characteristics of "strong acidic cation exchange resin" and "specific acidic pH environment". This overcomes the problems of co-precipitated phosphorus loss and secondary pollution caused by traditional chemical precipitation methods for impurity removal, and provides an indispensable and high-quality raw material guarantee for the high-value recovery of phosphorus resources in sludge gasification residue.

[0023] 2. The present invention provides a purification method for treating sludge gasification slag, which can efficiently and selectively remove Fe, Al and heavy metal ions from the acid leaching solution of sludge gasification slag, while retaining phosphorus to the maximum extent and without generating secondary pollution. This method has become a key technical bottleneck for realizing the high-value resource recovery of sludge gasification slag.

[0024] 3. This invention is a purification method with simple process, good selectivity and low phosphorus loss, which provides a high-quality raw material guarantee for the strategic recovery of phosphorus resources from sludge gasification residue and sludge thermal treatment products to prepare high-purity and high-value-added phosphorus products.

[0025] 4. This invention reduces the adsorption concentration by diluting the acid leaching solution (i.e., the obtained phosphorus-containing supernatant), thereby reducing the free acid concentration (i.e., increasing the pH) and total ionic strength in the feed solution, creating an optimal adsorption environment for the resin, minimizing phosphorus complexation loss and competitive adsorption, and thus obtaining a final pure phosphorus-containing solution.

[0026] 5. This invention precisely controls the P retention rate and the removal rates of Al, Fe, etc. by controlling the amount of resin added and the purification time, thereby ensuring maximum resource utilization.

[0027] 6. This invention, through secondary adsorption purification, verifies that it also has a good purification effect in the waste acid leaching system.

[0028] 7. The operation process of this invention is simple, flexible, easy to control and industrially applied.

[0029] 8. This invention can be applied to the resource-based treatment of wastewater and waste residue and the high-value utilization of waste resources, thereby greatly improving the utilization of solid waste resources and the recovery of strategic phosphorus resources.

[0030] In summary, this invention removes Fe and Al while retaining most of the phosphorus resources, exhibiting high selectivity, effective separation, and reduced loss of phosphorus due to entrainment and co-precipitation. Furthermore, it reduces heavy metal ions in the acid leaching solution, lowering the cost and environmental risk of subsequent treatment. In addition, the acid leaching solution purification method provided by this invention can achieve high cation removal and phosphorus retention rates in industrial waste acid systems. This invention promotes efficient phosphorus recovery, with a phosphorus recovery and retention rate exceeding 90%. This invention is easily automated, making it highly suitable for large-scale industrial continuous production, providing a feasible technical path for the large-scale resource utilization of sludge gasification residue. This invention provides a fundamental guarantee for the subsequent generation of high-purity, well-crystalled, and high-value-added products. Figure 4. Figure Description:

[0031] Figure 1. Analysis of the effect of adsorption time of the strong acid cation exchange resin of the present invention on the leaching content of each element.

[0032] Figure 2 shows the effect of the amount of strong acid cation exchange resin used in this invention on the leaching content of each element. Detailed Implementation Method Five: Detailed Implementation Method

[0033] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0034] The particle size of the gasification slag from the sludge after grinding used in the following examples is -200 mesh ≥ 88.6%; SO4 in industrial waste acid 2- The concentration was 69278.83 mg / L, F - The concentration was 2133.44 mg / L, Cl - The concentration was 5459.33 mg / L.

[0035] Example 1:

[0036] This invention relates to a method for preparing a pure phosphorus-containing solution from the acid leaching liquor of sludge gasification residue. The detailed steps are as follows:

[0037] a. Place 5g of the sludge gasification residue after grinding into a 50mL beaker, then add 50mL of 0.5mol / L sulfuric acid solution, place it on a magnetic stirrer, and stir and acid leaching at room temperature for 8 hours to obtain a mixed slurry;

[0038] b. Perform solid-liquid separation on the obtained mixed slurry and take 40 mL of phosphorus-containing supernatant;

[0039] c. Dilute 40 mL of the phosphorus-containing supernatant with water to 400 mL, then add 4 g of 732 type strong acid cation exchange resin and stir to purify for 4 h.

[0040] d. After purification, filter the solution obtained in step c to obtain a pure phosphorus-containing solution.

[0041] The pure phosphorus-containing solution obtained in Example 1 was diluted, and the concentrations of P, Al, Fe and other heavy metal elements were measured by ICP-OES after dilution (see Table 2 for details).

[0042] Example 2:

[0043] This invention relates to a method for preparing a pure phosphorus-containing solution from the acid leaching liquor of sludge gasification residue. The detailed steps are as follows:

[0044] a. Place 5g of the sludge gasification residue after grinding into a 50mL beaker, then add 50mL of 0.5mol / L sulfuric acid solution, place it on a magnetic stirrer, and stir and acid leaching at room temperature for 8 hours to obtain a mixed slurry;

[0045] b. Perform solid-liquid separation on the obtained mixed slurry and take 40 mL of phosphorus-containing supernatant;

[0046] c. Dilute 40 mL of the phosphorus-containing supernatant with water to 400 mL, then add 12 g of 732 type strong acid cation exchange resin and stir to purify for 4 h.

[0047] d. After purification, filter the solution obtained in step c to obtain a pure phosphorus-containing solution.

[0048] The pure phosphorus-containing solution obtained in Example 2 was diluted, and the concentrations of P, Al, Fe and other heavy metal elements were measured by ICP-OES after dilution (see Table 2 for details).

[0049] Example 3:

[0050] This invention relates to a method for preparing a pure phosphorus-containing solution from the acid leaching liquor of sludge gasification residue. The detailed steps are as follows:

[0051] a. Place 5g of the sludge gasification residue after grinding into a 50mL beaker, then add 50mL of 0.5mol / L sulfuric acid solution, place it on a magnetic stirrer, and stir and acid leaching at room temperature for 8 hours to obtain a mixed slurry;

[0052] b. Perform solid-liquid separation on the obtained mixed slurry and take 40 mL of phosphorus-containing supernatant;

[0053] c. Dilute 40 mL of the phosphorus-containing supernatant with water to 400 mL, then add 20 g of 732 type strong acid cation exchange resin and stir to purify for 4 h.

[0054] d. After purification, filter the solution obtained in step c to obtain a pure phosphorus-containing solution.

[0055] The pure phosphorus-containing solution obtained in Example 3 was diluted, and the concentrations of P, Al, Fe and other heavy metal elements were measured by ICP-OES after dilution (see Table 2 for details).

[0056] Example 4:

[0057] This invention relates to a method for preparing a pure phosphorus-containing solution from the acid leaching liquor of sludge gasification residue. The detailed steps are as follows:

[0058] a. Place 5g of the sludge gasification residue after grinding into a 50mL beaker, then add 50mL of industrial waste acid, place it on a magnetic stirrer, stir and acid leaching at room temperature for 8 hours to obtain a mixed slurry;

[0059] b. Perform solid-liquid separation on the obtained mixed slurry and take 40 mL of phosphorus-containing supernatant;

[0060] c. Dilute 40 mL of the phosphorus-containing supernatant with water to 200 mL, then add 20 g of 732 type strong acid cation exchange resin and stir to purify for 3 h.

[0061] d. Add an equal amount of 732 type strong acid cation exchange resin to the purified solution obtained in step c, and perform secondary adsorption purification at room temperature for 2 hours.

[0062] e. After purification, the liquid obtained in step d is subjected to solid-liquid separation to obtain a pure phosphorus-containing solution.

[0063] The pure phosphorus-containing solution obtained in Example 4 was diluted, and the concentrations of P, Al, Fe and other heavy metal elements were measured by ICP-OES after dilution (see Table 3 for details).

[0064] Example 5:

[0065] This invention relates to a method for preparing a pure phosphorus-containing solution from the acid leaching liquor of sludge gasification residue. The detailed steps are as follows:

[0066] a. Place 5g of the sludge gasification residue after grinding into a 50mL beaker, then add 50mL of industrial waste acid, place it on a magnetic stirrer, stir and acid leaching at room temperature for 8 hours to obtain a mixed slurry;

[0067] b. Perform solid-liquid separation on the obtained mixed slurry and take 40 mL of phosphorus-containing supernatant;

[0068] c. Dilute 40 mL of the phosphorus-containing supernatant with water to 400 mL, then add 20 g of 732 type strong acid cation exchange resin and stir to purify for 3 h.

[0069] d. Add an equal amount of 732 type strong acid cation exchange resin to the purified solution obtained in step c, and perform secondary adsorption purification at room temperature for 2 hours.

[0070] e. After purification, the liquid obtained in step d is subjected to solid-liquid separation to obtain a pure phosphorus-containing solution.

[0071] The pure phosphorus-containing solution obtained in Example 4 was diluted, and the concentrations of P, Al, Fe and other heavy metal elements were measured by ICP-OES after dilution (see Table 3 for details).

[0072] The treatment and regeneration method for the strongly acidic cation exchange resin used in this invention is implemented according to GB / T16496-1996. The treated strongly acidic cation exchange resin is neutralized by washing with water and then filtered for recycling.

[0073] Appendix Table 1 shows the concentrations of various elements in the phosphorus-containing supernatant obtained after acid leaching and filtration, as well as the phosphorus-containing solution obtained by directly purifying the undiluted phosphorus-containing supernatant with a strong acid cation exchange resin. Table 1 shows that purification with a strong acid cation exchange resin can reduce a significant portion of Al and Fe elements, but phosphorus (P) is also lost, exceeding 50%. Therefore, the phosphorus-containing supernatant obtained after acid leaching and filtration needs to be diluted (generally controlled at 5-10 times, with an optimal dilution ratio of 8-10 times) before purification with a strong acid cation exchange resin to effectively reduce P loss. Table 1 further shows that after purification with a strong acid cation exchange resin, the concentrations of most heavy metal ions decrease, even to almost zero, demonstrating that resin purification effectively reduces the influence of impurity ions in the phosphorus-containing solution.

[0074] Table 1. Concentrations of various elements in phosphorus-containing supernatant and purified phosphorus-containing solution.

[0075]

[0076] (Continued) Table 1 Concentrations of other elements in phosphorus-containing supernatant and purified phosphorus-containing solution

[0077]

[0078] Appendix Table 2 shows that after dilution and pretreatment of the phosphorus-containing supernatant, it was found that when the mass ratio of strong acid cation exchange resin to gasification slag was 5:1, the dilution factor was 10 times, and the resin purification time was 4 hours, the concentrations of Al and Fe were effectively reduced, while the P concentration decreased slightly. The removal rate of Al reached 87%, the removal rate of Fe reached 61.51%, while the loss of P was only 15.6%. Continuing from Table 2, it can be seen that after dilution and purification with strong acid cation exchange resin, when the resin dosage was 5 g / g, the content of other metal elements in the solution was extremely low, almost non-existent.

[0079] Table 2. Concentrations of various elements in the phosphorus-containing supernatant diluted 10 times and the purified phosphorus-containing solution obtained after resin purification.

[0080]

[0081] (Continued) Table 2 Concentrations of other elements in phosphorus-containing supernatant diluted 10 times and purified phosphorus-containing solutions obtained by resin purification

[0082]

[0083] Appendix Table 3 shows the resin purification results when using industrial waste acid as the acid solvent for acid leaching, verifying whether the resin still has a better purification effect in the waste acid system. To further remove the influence of Al and Fe impurities, secondary adsorption is required in the acid leaching solution within the waste acid system. The resin dosage for both primary and secondary adsorption is 5 g / g of gasification slag. As shown in Table 3, due to the high concentration of industrial waste acid and the presence of other impurities, the concentration of each element in the leachate is higher compared to pure sulfuric acid leaching. However, through resin purification, the metal ions in the solution can still be effectively removed in the waste acid system. Furthermore, through secondary adsorption, the concentrations of Al and Fe are further reduced, while the loss of P remains relatively unchanged. This verifies that secondary adsorption has a better effect in the waste acid system. However, the removal of Al and Fe and the retention of P are not significantly different between 1 h and 2 h of secondary adsorption. Therefore, controlling the secondary adsorption time to 1-2 h yields the best results.

[0084] Table 3 shows that, when using industrial waste acid as the acid solvent for acid leaching, and with the phosphorus-containing supernatant obtained after filtration diluted 5 times, secondary adsorption can achieve a removal rate of 78.3% for Al, 76.4% for Fe, and a retention rate of 88% for P. With a dilution of 10 times, secondary adsorption can achieve a removal rate of 85.4% for Al, 91.3% for Fe, and a retention rate of 93.3% for P. The comparison under both conditions further confirms that the resin has excellent selective adsorption capacity for Al and Fe, while its adsorption of P is very weak, maintaining good performance even in the waste acid leaching system. This selectivity rule still holds even under higher initial concentrations (a 5-fold dilution is higher than a 10-fold dilution), but the higher concentration also results in a greater absolute removal of impurities and may slightly increase the loss of P. Therefore, resin purification for impurity removal is most effective when the phosphorus-containing supernatant obtained after acid leaching is diluted 10 times. As can be seen from Appendix 3, in the industrial waste acid system, impurities are mixed, but through resin purification, a relatively pure phosphorus-containing solution can still be obtained, which can be widely used in subsequent product synthesis and industrial production.

[0085] Table 3. Concentrations of various elements in the diluted phosphorus-containing supernatant and the resulting pure phosphorus-containing solution under industrial waste acid conditions.

[0086]

[0087] Table 3. Concentrations of various elements in the diluted phosphorus-containing supernatant and the resulting pure phosphorus-containing solution under industrial waste acid conditions.

[0088]

[0089] Table 3. Concentrations of other elements in the diluted phosphorus-containing supernatant and the resulting pure phosphorus-containing solution under industrial waste acid conditions.

[0090]

[0091] Figure 1 shows the effect of adsorption time of strongly acidic cation exchange resin on the leaching content of each element (the treatment conditions are a resin to gasification slag mass ratio of 5:1 and the purification results of phosphorus-containing supernatant diluted 10 times). As the adsorption time increases, the contents of Al and Fe elements decrease, and the contents of P element decrease slightly. Under suitable conditions, while ensuring the removal of Al and Fe elements, P is maintained in the optimal retention form. When the resin purification time is 4 hours, the phosphorus leaching retention rate reaches 91.59%.

[0092] Figure 2 shows the effect of the amount of strongly acidic cation exchange resin on the leaching content of each element (the treatment conditions were a resin to gasification slag mass ratio of 5:1 and a phosphorus-containing supernatant diluted 10 times). It can be seen that increasing the amount of resin has a significant removal effect on Al and Fe, which indicates that strongly acidic cation exchange resin is beneficial to the separation, removal and recovery of metal ions in liquids.

Claims

1. A method for preparing a pure phosphorus-containing solution based on the purification of sludge gasification residue acid leaching liquor, characterized in that, The method includes the following steps: a) placing the sludge gasification residue after grinding in a container, then adding an acid solvent for dissolution and stirring, and obtaining a mixed slurry after stirring and acid leaching; b) performing solid-liquid separation on the obtained mixed slurry and taking the phosphorus-containing supernatant; c) diluting and pretreating the obtained phosphorus-containing supernatant, then adding a strong acid cation exchange resin for purification at room temperature; d) when the acid solvent in step a is industrial waste acid, adding an equal amount of strong acid cation exchange resin to the slurry obtained after purification in step c, and performing secondary adsorption purification at room temperature; e) after purification, performing solid-liquid separation on the slurry obtained in step c or step d to obtain a pure phosphorus-containing solution.

2. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The particle size of the sludge gasification residue after grinding in step a is -200 mesh ≥ 88.6%.

3. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The acid solvent mentioned in step a is sulfuric acid, hydrochloric acid, or industrial waste acid; the concentration of the acid solvent is 0.2 to 1.0 mol / L; the liquid-to-solid ratio is controlled to be 10 to 50 ml / g when adding the acid solvent.

4. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The acid leaching time in step a is 6 to 10 hours.

5. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The phosphorus-containing supernatant in step c is diluted by a factor of 5 to 10.

6. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The strong acid cation exchange resin mentioned in step c is type 732 strong acid cation exchange resin; the mass ratio of the strong acid cation exchange resin to the sludge gasification residue is 1 to 5:1, and the purification time is 1 to 4 hours.

7. The method for preparing a pure phosphorus-containing solution based on the acid leaching liquor of sludge gasification residue according to claim 1, characterized in that: The secondary adsorption purification time in step d is 1 to 3 hours.

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