CN113800681A

CN113800681A - Method for removing heavy metal ions in domestic garbage incineration fly ash eluent

Info

Publication number: CN113800681A
Application number: CN202111160782.1A
Authority: CN
Inventors: 徐乐瑾; 吴洁; 胡红云
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2021-12-17
Anticipated expiration: 2041-09-30
Also published as: CN113800681B

Abstract

The invention belongs to the technical field related to household garbage treatment, and discloses a method for removing heavy metal ions in household garbage incineration fly ash eluent, which comprises the following steps: s1: adjusting the domestic garbage incineration fly ash eluent to be acidic, and then adding Fe²⁺And H₂O₂To carry out Fenton reaction; s2: adjusting the pH value of the reacted supernatant to 5-7.5, adding activated zero-valent iron, and continuously adding Fe in the reaction process²⁺、Fe³⁺And an oxidant and continuously stirring, or continuously adding Fe in the reaction process²⁺And Fe³⁺Continuously aerating, and reacting for a preset time; s3: the solution after the reaction of step S2 is adjusted to be alkalineThe supernatant liquid after standing realizes the removal of heavy metal ions. The application can realize deep removal of heavy metal ions in the domestic waste incineration fly ash eluent, remarkably improves the removal efficiency of the heavy metal ions, and has remarkable economic benefit.

Description

Method for removing heavy metal ions in domestic garbage incineration fly ash eluent

Technical Field

The invention belongs to the technical field related to household garbage treatment, and particularly relates to a method for removing heavy metal ions in household garbage incineration fly ash eluent.

Background

With social progress and economic growth, the living standard of people is improved day by day, the daily production and living of human beings are active day by day, the yield of domestic garbage is increased day by day and the garbage composition is more complex. At present, three methods are mainly used for treating domestic garbage: (1) the waste incineration is used for generating power or supplying heat, but fly ash with high salt content can be generated in the process, and the heavy metal content of the waste incineration fly ash is high; (2) composting, namely performing biodegradation on the garbage by using microorganisms to generate a fertilizer for soil improvement, wherein the compostable garbage is kitchen garbage and garbage percolate is inevitably generated in the composting process; (3) sanitary landfill, more than seventy percent of domestic garbage in China is treated by the sanitary landfill, the investment and the operation cost of the sanitary landfill are low compared with those of garbage incineration, but the components of the sanitary landfill are complex, and a large amount of garbage leachate enriched with heavy metals and organic pollutants is generated. The first waste incineration mode is widely applied at present, but the defect is that the waste incineration fly ash has high heavy metal content and needs to be eluted. The final elution water in the current process still has high heavy metal content, and can not reach the discharge standard under most conditions.

Although the chinese patent CN110655172A provides a method for simply activating zero-valent iron to rapidly remove pollutants in water, the method can achieve the standard of heavy metal content when treating heavy metal ions in natural water, but is ineffective for incineration, washing and dehydration of household garbage containing multiple organic matters and heavy metals. Therefore, it is necessary to design a method with wider application range and better heavy metal ion treatment.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a method for removing heavy metal ions in domestic garbage incineration fly ash eluent, which can realize deep removal of the heavy metal ions in the domestic garbage incineration fly ash eluent, can realize the standard reaching of the heavy metal ions in the eluent, obviously improves the removal efficiency of the heavy metal ions and has obvious economic benefit.

Is made ofIn accordance with one aspect of the present invention, there is provided a method for removing heavy metal ions from an eluate of fly ash from incineration of household garbage, the method comprising: s1: adjusting the domestic garbage incineration fly ash eluent to be acidic, and then adding Fe²⁺And H₂O₂To carry out Fenton reaction; s2: adjusting the pH value of the reacted supernatant to 5-7.5, adding activated zero-valent iron, and continuously adding Fe in the reaction process²⁺、Fe³⁺And an oxidant and continuously stirring, or continuously adding Fe in the reaction process²⁺And Fe³⁺Continuously aerating, and reacting for a preset time; s3: the solution after the reaction in step S2 is adjusted to be alkaline and left standing, and the supernatant is the supernatant, so that the heavy metal ions are removed.

Preferably, the concentration of the activated part iron in the step S2 is 30-60 g/L.

Preferably, Fe is used in step S2²⁺And Fe³⁺The molar ratio of (A) to (B) is 2: 1.

Preferably, the oxidant in step S2 is one or more of dissolved oxygen, nitric acid, nitrate or hydrogen peroxide.

Preferably, NaOH and NaCO are used in step S2₃Or NaHCO₃Adjusting the pH value of the reacted supernatant to 5-7.5, wherein the stirring speed is 200-500 rpm, and the preset time is 6-24 h.

Preferably, the activated zero-valent iron is obtained in the following manner: mixing 30-60g/L iron powder and 1-3 g/L NaHNO₃And 1-3 g/L of FeSO₄Obtained after full reaction.

Preferably, the domestic waste incineration fly ash eluent in the step S1 is obtained by eluting domestic waste incineration fly ash through garbage leachate.

Preferably, the liquid-solid ratio of the household garbage incineration fly ash eluted through the garbage leachate is 2-4 mg/L.

Preferably, Fe in step S1²⁺The concentration of the solution is 1500-3000 ppm, H₂O₂The concentration of the solution is 4000-6000 mg/L.

Preferably, in the step S1, hydrochloric acid is used to adjust the pH of the domestic garbage incineration fly ash eluate to 3-5.

In general, compared with the prior art, the method for removing heavy metal ions in the domestic garbage incineration fly ash eluent has the following beneficial effects:

1. the method comprises the steps of firstly adopting a Fenton process to pretreat eluent, wherein a Fenton reaction can form hydroxyl free radicals OH, the hydroxyl free radicals are nonselective and can remove various organic matters, on one hand, the removal of the organic matters can reduce the probability of complexing of heavy metal ions and the organic matters, on the other hand, the complex of the heavy metal ions and the organic matters can be opened, so that the heavy metal ions are dissociated in a solution to be conveniently removed subsequently, and the oxidation product of the Fenton reaction is CO₂And H₂O, green and pollution-free, and no burden on subsequent treatment.

2. The zero-valent iron is activated to form a unique core-shell structure with an inner core of zero-valent iron and an outer layer of iron oxide (ferric oxide, ferroferric oxide, hydroxyl iron oxide and the like) coating, and the core-shell structure has higher reaction activity; the internal zero-valent iron can reduce hexavalent chromium ions, mercury ions, copper ions and the like, and iron oxides (ferric oxide, ferroferric oxide, hydroxyl oxygen iron and the like) on the surface and iron ions in the system can remove various heavy metal ions in water through the actions of precipitation, adsorption, lattice substitution and the like. Under the neutral condition, the activated zero-valent iron removes heavy metal ions in the eluent through multiple actions of oxidation reduction, electrostatic adsorption, flocculation precipitation and the like, and particularly has remarkable treatment efficiency on Pb, Mn, Cu, As, Se and Hg ions. And the zero-valent iron can further remove organic pollutants in the system through adsorption.

3. Under the alkaline condition, residual metal ions in the system can be precipitated, and pollutants in the eluent can be further removed.

4. The eluent in the application is obtained by eluting the fly ash generated by burning the household garbage through the garbage percolate, so that the waste is treated by the waste, and the obvious economic benefit is achieved.

5. The eluent is treated by combining Fenton oxidation and activated zero-valent iron, so that the reaction time can be obviously shortened, the treatment efficiency is high, most heavy metals can be removed, and powerful help and support are provided for subsequent treatment.

Drawings

FIG. 1 is a process diagram of a method for removing heavy metal ions from the fly ash eluate from incineration of household garbage;

fig. 2 is a schematic diagram of a process of generating a processing target eluent in the present embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The pure activated zero-valent iron has a good effect in treating natural wastewater, but the effect in treating domestic waste wastewater, particularly waste incineration fly ash elution water is very general, and the heavy metal content in the elution water cannot reach the discharge standard. The application provides a method for removing heavy metal ions in a domestic garbage incineration fly ash eluent, which specifically comprises the following steps S1-S3, as shown in FIG. 1.

S1: adjusting the domestic garbage incineration fly ash eluent to be acidic, and then adding Fe²⁺And H₂O₂To perform the Fenton reaction.

In this embodiment, the eluent is obtained by eluting fly ash from domestic waste through landfill leachate, for example, the effluent of the supernatant after the fly ash from domestic waste is eluted three times through landfill leachate is shown in fig. 2. The liquid-solid ratio of the domestic garbage incineration fly ash eluted by the garbage leachate is 2-4 mg/L, and the washing time is 30-60 min each time.

Fe²⁺The concentration of the solution is 1500-3000 ppm, H₂O₂The concentration of the solution is 4000-6000 mg/L, and the Fenton reaction time is 15-60 min.

And (3) adjusting the pH value of the domestic waste incineration fly ash eluent to 3-5 by adopting hydrochloric acid, and further preferably adjusting the pH value of the domestic waste incineration fly ash eluent to 4 by adopting hydrochloric acid.

The Fenton reaction mechanism is shown in the following formulas (1) to (4).

Fe²⁺+H₂O₂→Fe³⁺+·OH+OH^- (1)

Fe³⁺+H₂O₂→Fe²⁺+·HO²+H⁺ (2)

2·HO₂→H₂O₂+O₂ (3)

·OH+R-H→H₂O+R·→...→CO₂+H₂O (4)

The organic contaminants reduce the amount of metal ion adsorption by competing with the adsorbent surface ligands for metal ions, and the organic contaminants may also compete with the metal ions for adsorption sites to inhibit adsorption of the metal ions. S1 takes a Fenton method as a pretreatment method, hydroxyl free radicals OH are formed in the oxidation reaction, the hydroxyl free radicals are not selective, various organic pollutants can be removed, heavy metal ions in the system are prevented from being complexed with the organic pollutants, heavy metals in the system are dispersed in the solution in a free state, and accordingly the heavy metal removal effect in the system is improved.

The Pb ions are combined on the surface of zero-valent iron in the form of oxides or form hydroxide precipitates at a high pH value; mn ions are mainly removed by precipitation; cu ions are removed through adsorption and precipitation; the removal of As and Se ions is mainly electrostatic adsorption, and the main chemical form of selenium in neutral solution is HSeO₃ ^-、SeO₄ ^2-And SeO₃ ^2-As (V) is H with negative charge₂AsO₄ ^-The existence of the iron with zero valence has stronger electrostatic attraction effect on anions; hg ions are easily reduced to be simple substance Hg precipitate, and Hg is simultaneously precipitated²⁺Hydrolysis to form Hg (OH)₂，Hg(OH)₂Is easy to be adsorbed and fixed on the surface of the solid particles. Ferrous ions will accelerate to zeroThe electron-donating process of the valence iron surface influences the surface reaction active sites of the valence iron, thereby influencing Cu²⁺、Pb²⁺The ferric iron ions form ferric hydroxide colloid which is a good flocculating agent after the reduction of the metal ions. The partial reaction formula is as follows:

pb²⁺+2OH^-＝Pb(OH)₂↓ (7)

Hg²⁺+2e^-＝Hg↓ (8)

2H₂O+Hg²⁺→Hg(OH)₂+2H⁺ (9)

in this example, the activated zero-valent iron removes heavy metal ions in the eluate by multiple actions such as oxidation reduction, electrostatic adsorption, flocculation precipitation, and the like.

S2: adjusting the pH value of the reacted supernatant to 5-7.5, adding activated zero-valent iron, and continuously adding Fe in the reaction process²⁺、Fe³⁺And an oxidant and continuously stirring, or continuously adding Fe in the reaction process²⁺And Fe³⁺And continuously aerating, and reacting for a preset time.

In this embodiment, NaOH and NaCO are preferably used₃Or NaHCO₃And adjusting the pH value of the reacted supernatant to 5-7.5.

The activated zero-valent iron is obtained as follows:

mixing 30-60g/L iron powder and 1-3 g/L NaHNO₃And 1-3 g/L of FeSO₄And (3) obtaining after full reaction, continuously stirring in the reaction process, wherein the rotating speed of a stirring paddle is 300-700 rpm, and the activation time is 72-120 h. The zero-valent iron is oxidized to form a unique core-shell structure with a core of zero-valent iron and an outer layer of iron oxide (iron oxide, ferroferric oxide, hydroxyl iron oxide and the like) coating in the process of activating the zero-valent iron, and the iron-based composite material has higher reaction activityAnd (4) sex.

The concentration range of the activated part iron is 30-60 g/L. The dosage of the activated zero-valent iron can be kept for reacting the wastewater of the same batch for five times or more, and can be increased or reduced properly according to the actual condition. After excessive reaction, the activated zero-valent iron can be directly utilized or cleaned by clear water for 1-3 times.

Said Fe²⁺And Fe³⁺The molar ratio of (A) to (B) is 2: 1.

The oxidant is one or a mixture of more of dissolved oxygen, nitric acid, nitrate or hydrogen peroxide, and the concentration of the iron ions and the oxidant is 20-200 mM. The oxidant can continuously oxidize zero-valent iron to generate oxides such as ferric oxide, ferroferric oxide, hydroxyl ferric oxide and the like, so as to prevent the surface of the oxides from being passivated, the ferric salt maintains the activity of activated zero-valent iron, the ferrous iron converts the iron oxide on the surface of the zero-valent iron into the ferroferric oxide, and the ferric iron plays a role in iron ion balance and certain flocculation.

The rotating speed of the stirring paddle is preferably 200-500 rpm, and the preset time is preferably 6-24 h. The rotating speed of the stirring paddle just ensures that zero-valent iron does not accumulate at the bottom of the reactor, and the low-zero-valent iron and the eluent are not uniformly mixed at the rotating speed, so that the reaction is insufficient; the zero-valent iron shell with the over-high rotating speed adsorbs organic matters to scatter.

S3: the solution after the reaction in step S2 is adjusted to be alkaline and left standing, and the supernatant is the supernatant, so that the heavy metal ions are removed.

Further preferably, the pH value in the step is 9-9.5. The above processes can be carried out at normal temperature and normal pressure, and the reaction conditions are not harsh and are easy to carry out.

Example 1

In this embodiment, a single Fenton process, a single zero-valent iron activation process, a simultaneous zero-valent iron + Fenton activation treatment process, a Fenton process performed after the zero-valent iron activation treatment, and the method of the present application are respectively performed with metal ion removal, and the results are shown in table 1 below.

Fenton technology alone: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 4 with 5M dilute hydrochloric acid solution, adding 4500ppm FeSO₄Mixing all the materialsAfter homogenizing, 3300ppm H was added₂O₂The reaction was carried out at 25 ℃ for 1 hour with a shaker at 300rpm, and the concentration of each ion and COD were measured after filtration.

The process for separately activating the zero-valent iron comprises the following steps: the eluent was subjected to an experiment. 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding activated zero-valent iron 30-60g/L and FeSO 20ppm₄And 10ppm FeCl₃The reaction is carried out in a constant temperature water bath at 25 ℃ and at a stirring speed of 300rpm for 120 minutes, and the concentration of each ion and COD are measured after filtration.

The simultaneous treatment process of activated zero-valent iron and Fenton comprises the following steps: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting the pH value to 7 by NaOH, adding 30-60g/L excessive activated zero-valent iron, and adding 4500ppm FeSO₄After mixing uniformly, 3300ppm H was added₂O₂Reacting for 1h, sampling, filtering, measuring COD concentration, and adding 20ppm FeSO₄And 10ppm FeCl₃The reaction was carried out at 25 ℃ and a stirring speed of 300 rpm. The reaction time is 2 h. After sampling and filtering at intervals, the concentration of each ion is measured.

The Fenton process after activation of zero-valent iron: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding 30-60g/L excess activated zero-valent iron and 20ppm FeSO₄And 10ppm FeCl₃The reaction is carried out in a constant temperature water bath at 25 ℃ and at a stirring speed of 300rpm, and the reaction time is 2 h. After sampling and filtering at intervals, the concentration of each ion is measured. Taking supernatant after the reaction to perform Fenton reaction, adjusting the pH to be 4 by using dilute hydrochloric acid, and adjusting the pH to be 5000ppm H₂O₂The solution is stirred evenly and reacted for 30 min. In the whole process, the COD value and the ion concentration are measured after sampling and filtering at intervals.

The process for activating zero-valent iron after Fenton: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 4 with 5M dilute hydrochloric acid solution, adding 4500ppm FeSO₄After mixing uniformly, 3300ppm H was added₂O₂The reaction was carried out at 25 ℃ on a shaker at 300 rpm. Adjusting the pH value of the supernatant after the reaction to 7 by NaOH, adding 30-60g/L excessive activated zero-valent iron and 20ppm FeSO₄And 10ppm FeCl₃The reaction is carried out in a constant temperature water bath at 25 ℃ and at a stirring speed of 300rpm, and the reaction time is 2 h. After sampling and filtering at intervals, the concentration of each ion is measured.

TABLE 1

In the process, the COD value of the water sample is determined according to HJ/T399-; detecting the content of copper in the wastewater according to GB 7475-87 water quality-copper determination-atomic absorption spectrophotometry; detecting the contents of iron and manganese in the wastewater according to GB 11911-89 water quality-determination of iron and manganese-flame atomic absorption spectrophotometry; according to the HJ 694-2014 water quality-the determination of mercury, arsenic and selenium-the atomic fluorescence method, the content of mercury, arsenic and selenium in the wastewater is detected.

As can be seen from table 1, compared with the Fenton alone, the zero-valent iron alone activated, the simultaneous treatment process of the zero-valent iron and the Fenton activated, and the Fenton after zero-valent iron activated process, the synergistic process of the zero-valent iron activated after Fenton in the present application can improve the COD removal rate and significantly reduce the heavy metal concentration of the effluent.

Example 2

The method of the present application was used to examine the effect of different reaction times on the removal of heavy metals, and the results are shown in table 2 below.

Step S2 reaction for 2 h: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding 30-60g/L excess activated zero-valent iron and 20ppm FeSO₄And 10ppm FeCl₃Reacting in 25 deg.C constant temperature water bath at stirring speed of 300rpmFor 120 minutes. After sampling and filtering at intervals, the concentration of each ion is measured.

Step S2 reaction for 6 h: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding activated zero-valent iron 30-60g/L, reacting in 25 deg.C constant temperature water bath at stirring speed of 300rpm, and adding FeSO 20ppm every 2h₄And 10ppm FeCl₃And the reaction time is 6 h. After sampling and filtering at intervals, the concentration of each ion is measured.

Step S2 reaction for 24 h: 2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding activated zero-valent iron 30-60g/L, reacting in 25 deg.C constant temperature water bath at stirring speed of 300rpm, and adding FeSO 20ppm every 2h₄And 10ppm FeCl₃And the reaction time is 24 hours. After sampling and filtering at intervals, the concentration of each ion is measured.

TABLE 2

As can be seen from Table 2, the removal rate of each heavy metal ion becomes higher and higher with the increase of the reaction time, and after 6 hours, the removal rate of the metal ions other than Pb is substantially maintained stable.

Example 3

The embodiment is used for verifying that the method has good treatment effect when treating the eluent with high heavy metal concentration.

2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 4 with 5M dilute hydrochloric acid solution, adding 4500ppm FeSO₄After mixing uniformly, 3300ppm H was added₂O₂The reaction was carried out at 25 ℃ on a shaker at 250 rpm. Adjusting pH to 7 with NaOH, adding activated zero-valent iron 30-60g/L, reacting in 25 deg.C constant temperature water bath at stirring speed of 300rpm, and adding FeSO 20ppm every 2h₄And 10ppm FeCl₃Reaction time 6h. The mixture was left standing for 30 minutes with the pH adjusted to 9, and then sampled. After sampling and filtering at intervals, the concentration of each ion is measured. The results are shown in Table 3.

TABLE 3

As can be seen from Table 3, the Fenton and activated zero-valent iron process has a good effect of removing heavy metal salts in the domestic garbage incineration fly ash eluate.

Example 4

2ppm of Mn, Pb, Cu, As, Se and Hg ions were added to the eluate, and the eluate with a high heavy metal concentration was simulated using actual wastewater. Adjusting pH to 7 with NaOH, adding activated zero-valent iron 5, 20, 60, 100g/L, reacting in 25 deg.C constant temperature water bath at stirring speed of 300rpm, and adding FeSO 20ppm every 2 hr₄And 10ppm FeCl₃And the reaction time is 6 h. The mixture was left standing for 30 minutes with the pH adjusted to 9, and then sampled. After sampling and filtering at intervals, the concentration of each ion is measured. The results are shown in Table 4.

TABLE 4

As can be seen from Table 4, the removal effect of the activated zero-valent iron on each heavy metal ion is basically unchanged after the addition amount of the activated zero-valent iron is more than 5g/L, and the experiments of 30-60g/L active iron are adopted in the experiments for economy and sustainable utilization.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for removing heavy metal ions in domestic waste incineration fly ash eluent is characterized by comprising the following steps:

s1: adjusting the domestic garbage incineration fly ash eluent to be acidic, and then adding Fe²⁺And H₂O₂To carry out Fenton reaction;

s2: adjusting the pH value of the reacted supernatant to 5-7.5, adding activated zero-valent iron, and continuously adding Fe in the reaction process²⁺、Fe³⁺And an oxidant and continuously stirring, or continuously adding Fe in the reaction process²⁺And Fe³⁺Continuously aerating, and reacting for a preset time;

2. The method as claimed in claim 1, wherein the concentration of the activated part iron in step S2 is 30-60 g/L.

3. The method according to claim 1 or 2, wherein the Fe is in step S2²⁺And Fe³⁺The molar ratio of (A) to (B) is 2: 1.

4. The method according to claim 1, wherein the oxidant in step S2 is one or more of dissolved oxygen, nitric acid, nitrate or hydrogen peroxide.

5. The method of claim 1, wherein NaOH and NaCO are used in step S2₃Or NaHCO₃Adjusting the pH value of the reacted supernatant to 5-7.5, wherein the stirring speed is 200-500 rpm, and the preset time is 6-24 h.

6. The method according to claim 1 or 5, characterized in that the activated zero-valent iron is obtained by:

mixing 30-60g/L iron powder and 1-3 g/L NaHNO₃And 1-3 g/L of FeSO₄Fully reactAnd (4) obtaining.

7. The method according to claim 1, wherein the domestic waste incineration fly ash eluent in the step S1 is obtained after the domestic waste incineration fly ash is eluted by landfill leachate.

8. The method according to claim 7, wherein the liquid-solid ratio of the domestic waste incineration fly ash eluted by the landfill leachate is 2-4 mg/L.

9. The method of claim 1, wherein Fe in step S1²⁺The concentration of the solution is 1500-3000 ppm, H₂O₂The concentration of the solution is 4000-6000 mg/L.

10. The method according to claim 1, wherein the pH of the domestic waste incineration fly ash eluate in step S1 is adjusted to 3-5 with hydrochloric acid.