阅读说明：本技术 一种脱除粉煤灰中重金属及含重金属尾液净化方法 (Purification method for removing heavy metals from fly ash and heavy metal-containing tail liquid ) 是由 马淑花 王晓辉 刘福立 于 2020-06-28 设计创作，主要内容包括：本发明提供一种脱除粉煤灰中重金属及含重金属尾液净化方法,所述方法包括以下步骤：(1)将粉煤灰与酸溶液混合并进行反应,反应后固液分离得到浸出液和浸出渣；(2)对步骤(1)得到的浸出渣进行浆洗,得到浆洗液以及脱除重金属的粉煤灰；(3)合并步骤(1)得到的浸出液以及步骤(2)得到的浆洗液得到含重金属尾液,向所述尾液中加入铝源调节Al～(3+)与SO-(4)～(2-)以及Si～(4+)的摩尔浓度比例,再加入钙源调节所述尾液的pH,反应后固液分离,完成对所述含重金属尾液的净化。所述方法重金属的去除率高,工艺简单,成本低,可有效提升粉煤灰的利用率。(The invention provides a purification method for removing heavy metals in fly ash and tail liquid containing the heavy metals, which comprises the following steps: (1) mixing the fly ash and an acid solution, reacting, and performing solid-liquid separation after reaction to obtain a leaching solution and leaching residues; (2) performing slurry washing on the leaching residue obtained in the step (1) to obtain slurry washing liquid and fly ash for removing heavy metals; (3) merging the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain a heavy metal-containing tail liquid, and adding an aluminum source into the tail liquid to adjust Al 3+ With SO 4 2‑ And Si 4+ And adding a calcium source to adjust the pH value of the tail liquid according to the molar concentration ratio, and performing solid-liquid separation after reaction to finish the purification of the heavy metal-containing tail liquid. The method has the advantages of high removal rate of heavy metals, simple process and low cost, and can effectively improve the utilization rate of the fly ash.)

1. A purification method for removing heavy metals and heavy metal-containing tail liquid in fly ash is characterized by comprising the following steps:

(1) mixing the fly ash and an acid solution, reacting, and performing solid-liquid separation after reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1) to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) merging the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain a heavy metal-containing tail liquid, and adding an aluminum source into the tail liquid to adjust Al³⁺With SO₄ ^2-And Si⁴⁺And adding a calcium source to adjust the pH value of the tail liquid according to the molar concentration ratio, and performing solid-liquid separation after reaction to finish the purification of the heavy metal-containing tail liquid.

2. The method according to claim 1, wherein the concentration of the acid solution in the step (1) is 0.1-2 mol/L;

preferably, the volume-mass ratio of the acid solution to the fly ash is 2-5: 1L/kg.

3. The method according to claim 1 or 2, wherein the acid solution of step (1) is a sulfuric acid solution.

4. The method according to any one of claims 1 to 3, wherein the reaction time in step (1) is 20 to 60 ℃;

preferably, the reaction time in the step (1) is 30-150 min;

preferably, the reaction of step (1) is carried out under stirring.

5. The method according to any one of claims 1 to 4, wherein the volume mass ratio of the slurry water used in the step (2) to the leaching residue is 2-8: 1L/kg.

6. The method of any one of claims 1-5, wherein step (3) adjusts Al³⁺The molar concentration of (0.60-0.72) times of SO₄ ^2-Molar concentration of (0.45 to 0.60) times of Si⁴⁺The sum of the molar concentrations of (c);

preferably, the aluminum source in step (3) is aluminum hydroxide.

7. The method according to any one of claims 1 to 6, wherein the pH of the tail liquid is adjusted to 10-12.5 by adding the calcium source in the step (3);

preferably, the calcium source is calcium hydroxide and/or calcium oxide.

8. The method according to any one of claims 1 to 7, wherein the temperature of the reaction in step (3) is 20 to 60 ℃;

preferably, the reaction time in the step (3) is 30-120 min.

9. The method of any one of claims 1 to 8, wherein the fly ash is ball milled prior to step (1).

10. Method according to any of claims 1-9, characterized in that the method comprises the steps of:

(1) mixing the fly ash and an acid solution with the concentration of 0.1-2 mol/L, reacting under stirring, wherein the volume mass ratio of the acid solution to the fly ash is 2-5: 1L/kg, the reaction time is 20-60 ℃, the reaction time is 30-150 min, and performing solid-liquid separation after reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 2-8: 1L/kg, so as to obtain slurry washing liquid and fly ash from which heavy metals are removed;

(3) merging the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain a heavy metal-containing tail liquid, and adding an aluminum source into the tail liquid to adjust Al³⁺The molar concentration of (0.60-0.72) times of SO₄ ^2-Molar concentration of (0.45 to 0.60) times of Si⁴⁺Adding a calcium source to adjust the pH value of the tail liquid to 10-12.5, carrying out solid-liquid separation after reaction at the temperature of 20-60 ℃ for 30-120 min, and finishing the purification of the heavy metal-containing tail liquid.

Technical Field

The invention belongs to the field of treatment of heavy metals in solid waste and waste liquid, and relates to a purification method for removing heavy metals in fly ash and tail liquid containing the heavy metals.

Background

Fly ash is fly ash generated after high-temperature combustion of coal, and is one of industrial solid wastes with the largest production amount in China at present. Because the fly ash contains a certain amount of heavy metal elements, such as arsenic, mercury, lead, chromium and the like, and the occurrence state of the heavy metal elements is relatively complex, the possibility of migration exists in the natural environment, and the expansion of the comprehensive utilization approach of the fly ash is restricted. Therefore, it is necessary to develop a method for efficiently removing heavy metal elements from fly ash.

At present, the technology for removing heavy metal elements in fly ash is less researched. CN108237137A discloses a fly ash demercuration device, comprising: a thermal desorption unit for volatilizing mercury in the fly ash to form gaseous mercury; a plasma reactor for oxidizing the gaseous mercury to oxidized mercury; and the adsorption unit is used for adsorbing the oxidized mercury. A fly ash demercuration method is also provided. The device and the method combine the thermal desorption of the fly ash and the super-oxidation process of the mercury, ensure the high-efficiency desorption of the mercury from the fly ash, and realize the high-efficiency demercuration of the fly ash. The method adopts a high-temperature gasification method to remove mercury in the pulverized coal, but the applicability of the high-temperature gasification method is limited due to various heavy metal elements in the pulverized coal, complex and various forms and properties. Meanwhile, the high-temperature method has high energy consumption and high cost. The new method for removing the heavy metal from the fly ash by the low-temperature wet method, which is simple in development process and low in cost, is a problem which needs to be solved urgently by the resource utilization of the fly ash at present.

CN 109942114A discloses a method for simultaneously removing heavy metals in fly ash and industrial wastewater, which comprises the following steps: crushing unburned carbon to obtain adsorption carbon; adding tap water into the adsorption carbon to prepare adsorption carbon liquid, then adding kerosene, uniformly stirring, then carrying out flotation, carrying out vacuum filtration after flotation, and then drying to obtain modified adsorption carbon; respectively adding modified adsorption carbon into a plurality of connected adsorption tanks, sequentially passing the wastewater containing heavy metals through the adsorption tanks to adsorb the heavy metals, adding a liquid precipitator into the modified adsorption carbon for adsorbing the heavy metals to precipitate the heavy metals, and filtering to remove the heavy metals. The method needs to convert the fly ash into the adsorption carbon, and the heavy metal is adsorbed and then precipitated by using the precipitator, but the adsorption carbon has small pore diameter and is difficult to completely remove the heavy metal elements adsorbed by the adsorption carbon, and the method has low overall heavy metal removal efficiency.

After the heavy metals are removed from the fly ash by a wet method, the heavy metals in the fly ash are transferred to a liquid phase, and the purification treatment of the liquid phase containing the heavy metals is necessary to avoid secondary pollution. In addition, during the wet-process removal of heavy metals from fly ash, a small amount of aluminum, silicon, calcium ions and other impurity ions may enter the liquid phase to form a complex multi-ion system, and these impurity ions also need to be purified together. For removing heavy metal ions in a liquid phase, the conventional methods comprise a chemical precipitation method, an ion exchange method, an electrolysis method, an adsorption method and the like, but the conventional methods have certain defects and shortcomings, and are difficult to effectively treat a complex system containing a plurality of trace heavy metal elements and a plurality of ions. Therefore, how to overcome the defects of the traditional treatment method and research an efficient and environment-friendly purification treatment method of complex solution containing heavy metal elements and various ions becomes a problem to be solved urgently.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a purification method for removing heavy metals in fly ash and tail liquid containing the heavy metals, which has the advantages of high removal rate of the heavy metals, simple process and low cost, and can effectively improve the utilization rate of the fly ash.

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

the invention provides a purification method for removing heavy metals in fly ash and tail liquid containing the heavy metals, which comprises the following steps:

(1) mixing the fly ash and an acid solution, reacting, and performing solid-liquid separation after reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1) to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) merging the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain a heavy metal-containing tail liquid, and adding an aluminum source into the tail liquid to adjust Al³⁺With SO₄ ^2-And Si⁴⁺And adding a calcium source to adjust the pH value of the tail liquid according to the molar concentration ratio, and performing solid-liquid separation after reaction to finish the purification of the heavy metal-containing tail liquid.

In the invention, the fly ash is obtained by a conventional coal combustion process, and contains various heavy metal elements including Cr, As, Cd, Hg, Pb and the like. Through the occurrence morphological analysis of the heavy metal in the fly ash, the following results are found: most heavy metals in the fly ash are enriched in amorphous components in the fly ash, and are water-soluble and acid-soluble. However, since the heavy metal is not present on the surface of the fly ash particles but present in the amorphous phase of the fly ash, the heavy metal cannot be sufficiently dissolved out with water, and the heavy metal can be effectively dissolved out only by sufficiently breaking the structure of the amorphous phase through an acid solution with a specific concentration under the conditions of a specific temperature and a specific reaction time to sufficiently expose the heavy metal present therein. Therefore, the structure of the amorphous component can be effectively destroyed through acid leaching treatment under proper conditions, and the heavy metal in the amorphous component is fully exposed and then dissolved out.

In the invention, after the fly ash is subjected to acid leaching, part of heavy metal enters the acid leaching solution and the slurry washing solution, and a small amount of ions such as aluminum, silicon, calcium, iron, magnesium and the like and sulfate ions enter the acid leaching solution to form tail solution containing heavy metal and a plurality of ions. In order to avoid secondary pollution caused by tail liquid and realize purification and utilization of the tail liquid, the invention utilizes the characteristic that the tail liquid is acidic and contains aluminum, silicon and sulfate ions, and adjusts Al/SO by adding an aluminum source and a calcium source into the tail liquid₄ ^2-Al/Si ratio and system pH value, and in-situ generates ettringite (Ca)₆Al₂(SO₄)₃(OH)₁₂·26H₂O) and zeolite (Ca)₄Al₈Si₁₆O₄₈·14H₂O) mixed double salt precipitation, aluminum, silicon, calcium and sulfate ions in the solution can be nearly completely precipitated, and other major elements such as iron and magnesium and most heavy metal elements in the solution can be synchronously precipitated in modes of adsorption, entrainment, flocculation and the like, so that the deep purification of the tail solution is realized. The ettringite has higher crystallinity and weaker flocculation capacity, while the turbid zeolite is a siliceous phase and has poorer crystallinity, has certain gelation effect, can play a role in promoting the flocculation of the ettringite and obviously improves the purification effect.

As a preferred embodiment of the present invention, the concentration of the acid solution in step (1) is 0.1 to 2mol/L, such as 0.2mol/L, 0.5mol/L, 0.8mol/L, 1mol/L, 1.2mol/L, 1.5mol/L, or 1.8mol/L, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the volume-to-mass ratio of the acid solution to the fly ash is 2-5: 1L/kg, such as 2.5L/kg, 3L/kg, 3.5L/kg, 4L/kg, or 4.5L/kg, but not limited to the recited values, and other values not recited in the range of values are also applicable.

As a preferable technical scheme of the invention, the acid solution in the step (1) is a sulfuric acid solution.

In a preferred embodiment of the present invention, the reaction time in step (1) is 20 to 60 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃ or 55 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the reaction time in step (1) is 30-150 min, such as 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min or 140min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the reaction of step (1) is carried out under stirring.

In a preferred embodiment of the present invention, the volume/mass ratio of the slurry water to the leached residue in the step (2) is 2 to 8:1L/kg, for example, 3:1L/kg, 4:1L/kg, 5:1L/kg, 6:1L/kg or 7:1L/kg, but the present invention is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

As a preferable embodiment of the present invention, the adjusting Al in the step (3)³⁺The molar concentration of (0.60-0.72) times of SO₄ ^2-Molar concentration of (0.45 to 0.60) times of Si⁴⁺The sum of the molar concentrations of (c).

Wherein may be SO₄ ^2-0.61 times, 0.62 times, 0.63 times, 0.64 times, 0.65 times, 0.66 times, 0.67 times, 0.68 times, 0.69 times, 0.70 times, 0.71 times, etc. of the molar concentration of (A) may be Si⁴⁺0.46 times, 0.47 times, 0.48 times, 0.49 times, 0.50 times, 0.51 times, 0.52 times, 0.53 times, 0.54 times, 0.55 times, 0.56 times, 0.57 times, 0.58 times, or 0.59 times the molar concentration of (A) and (B) are not limited to the values listed, and other values not listed in the above numerical ranges are also applicable.

Preferably, the aluminum source in step (3) is aluminum hydroxide.

In a preferred embodiment of the present invention, the calcium source is added in step (3) to adjust the pH of the tail solution to 10 to 12.5, such as 10.2, 10.5, 10.8, 11.0, 11.2, 11.5, 11.8, 12.0, 12.2, or 12.4, but the pH is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

Preferably, the calcium source is calcium hydroxide and/or calcium oxide.

In a preferred embodiment of the present invention, the temperature of the reaction in step (3) is 20 to 60 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃ or 55 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the reaction time in step (3) is 30-120 min, such as 40min, 50min, 60min, 70min, 80min, 90min, 100min or 110min, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

As a preferable technical scheme of the invention, the fly ash is subjected to ball milling treatment before the step (1).

As a preferred technical scheme of the invention, the purification method for removing heavy metals from fly ash and tail liquid containing the heavy metals comprises the following steps:

(1) mixing the fly ash and an acid solution with the concentration of 0.1-2 mol/L, reacting under stirring, wherein the volume mass ratio of the acid solution to the fly ash is 2-5: 1L/kg, the reaction time is 20-60 ℃, the reaction time is 30-150 min, and performing solid-liquid separation after reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 2-8: 1L/kg, so as to obtain slurry washing liquid and fly ash from which heavy metals are removed;

(3) merging the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain a heavy metal-containing tail liquid, and adding an aluminum source into the tail liquid to adjust Al³⁺The molar concentration of (0.60-0.72) times of SO₄ ^2-Molar concentration of (0.45 to 0.60) times of Si⁴⁺Adding a calcium source to adjust the pH value of the tail liquid to 10-12.5, carrying out solid-liquid separation after reaction at the temperature of 20-60 ℃ for 30-120 min, and finishing the purification of the heavy metal-containing tail liquid.

Compared with the prior art, the invention at least has the following beneficial effects:

(1) the invention provides a purification method for removing heavy metals and heavy metal-containing tail liquid in fly ash, which has the advantages of simple process and high industrial feasibility, and through simple acid leaching treatment, the removal rate of Cr, As, Cd, Hg, Pb, Ni, Cu and Zn in the fly ash can reach 30-90%, so that the synchronous removal of various heavy metal elements in the fly ash is realized;

(2) the invention provides a purification method for removing heavy metals and heavy metal-containing tail liquid in fly ash, which can synchronously remove the heavy metals and other ions in the tail liquid, the removal rate of the heavy metals can reach more than 96 percent, and the removal rate of aluminum, silicon, calcium, iron, magnesium and sulfate ions can reach more than 91 percent, thereby realizing the deep purification of the tail liquid. The obtained ettringite and turbid zeolite precipitates can be used for preparing cement and concrete, and heavy metals in the ettringite and turbid zeolite precipitates can be solidified and cannot migrate in the environment.

Drawings

FIG. 1 is an XRD test spectrum of a solid obtained by solid-liquid separation in step (3) of example 1;

FIG. 2 is an XRD test spectrum of a solid obtained by solid-liquid separation in step (3) of comparative example 1.

The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows:

example 1

The embodiment provides a purification method for removing heavy metals from fly ash and tail liquid containing the heavy metals, which comprises the following steps:

the fly ash used in this example is fly ash from a certain power plant of reonbell, inner Mongolia, and the heavy metal content is shown in Table 1;

(1) mixing the fly ash and a sulfuric acid solution with the concentration of 0.5mol/L, reacting under stirring, wherein the volume mass ratio of the sulfuric acid solution to the fly ash is 4:1L/kg, the reaction time is 20 ℃, the reaction time is 60min, and performing solid-liquid separation after the reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 8:1L/kg, so as to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) combining the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain heavy metal-containing tail liquid, and adding aluminum hydroxide to the tail liquid to adjust Al³⁺Has a molar concentration of 0.68 times SO₄ ^2-Molar concentration of (3) and 0.50 times of Si⁴⁺Adding calcium hydroxide to adjust the pH value of the tail liquid to 11.0, reacting under stirring, and carrying out solid-liquid separation at the reaction temperature of 20 ℃ for 90min to complete the purification of the heavy metal-containing tail liquid.

XRD test of the solid phase obtained by solid-liquid separation in step (3) revealed that the solid phase contained ettringite and a turbid zeolite phase, as shown in FIG. 1.

Example 2

The embodiment provides a purification method for removing heavy metals from fly ash and tail liquid containing the heavy metals, which comprises the following steps:

the fly ash used in this example is fly ash from a power plant, yucca, inner Mongolia, and the heavy metal content is shown in Table 1;

(1) mixing the fly ash and a sulfuric acid solution with the concentration of 0.2mol/L, reacting under stirring, wherein the volume mass ratio of the sulfuric acid solution to the fly ash is 3:1L/kg, the reaction time is 40 ℃, the reaction time is 90min, and performing solid-liquid separation after the reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 4:1L/kg, so as to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) combining the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain heavy metal-containing tail liquid, and adding aluminum hydroxide to the tail liquid to adjust Al³⁺Molar concentration ofIs 0.64 times SO₄ ^2-Molar concentration of (3) and 0.55 times of Si⁴⁺Adding calcium hydroxide to adjust the pH value of the tail liquid to 12.5, reacting under stirring, and carrying out solid-liquid separation at 40 ℃ for 60min to complete the purification of the heavy metal-containing tail liquid.

Example 3

The embodiment provides a purification method for removing heavy metals from fly ash and tail liquid containing the heavy metals, which comprises the following steps:

the fly ash used in the embodiment is fly ash of a power plant for Shanxi Changzhi, and the heavy metal content is shown in Table 1;

(1) mixing the coal ash and a sulfuric acid solution with the concentration of 2.0mol/L, reacting under stirring, wherein the volume mass ratio of the sulfuric acid solution to the coal ash is 2:1L/kg, the reaction time is 60 ℃, the reaction time is 30min, and performing solid-liquid separation after the reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 6:1L/kg, so as to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) combining the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain heavy metal-containing tail liquid, and adding aluminum hydroxide to the tail liquid to adjust Al³⁺Has a molar concentration of 0.60 times SO₄ ^2-Molar concentration of (3) and 0.60 times Si⁴⁺Adding calcium hydroxide to adjust the pH value of the tail liquid to 11.5, reacting under stirring, and carrying out solid-liquid separation at the reaction temperature of 60 ℃ for 120min to complete the purification of the heavy metal-containing tail liquid.

Example 4

The embodiment provides a purification method for removing heavy metals from fly ash and tail liquid containing the heavy metals, which comprises the following steps:

the fly ash used in this example is fly ash from a certain power plant in Ordors, inner Mongolia, and the heavy metal content is shown in Table 1;

(1) mixing the fly ash and a sulfuric acid solution with the concentration of 0.1mol/L, reacting under stirring, wherein the volume mass ratio of the sulfuric acid solution to the fly ash is 5:1L/kg, the reaction time is 30 ℃, the reaction time is 150min, and performing solid-liquid separation after the reaction to obtain a leaching solution and leaching residues;

(2) performing slurry washing on the leaching residue obtained in the step (1), wherein the volume mass ratio of water for slurry to the leaching residue is 2:1L/kg, so as to obtain slurry washing liquid and fly ash for removing heavy metals;

(3) combining the leachate obtained in the step (1) and the pulp washing liquid obtained in the step (2) to obtain heavy metal-containing tail liquid, and adding aluminum hydroxide to the tail liquid to adjust Al³⁺Has a molar concentration of 0.72 times SO₄ ^2-Molar concentration of (3) and 0.45 times of Si⁴⁺Adding calcium oxide to adjust the pH value of the tail liquid to 10.0, reacting under stirring, and carrying out solid-liquid separation, wherein the reaction temperature is 30 ℃ and the reaction time is 30min, thereby completing the purification of the heavy metal-containing tail liquid.

Example 5

This example was carried out under the same conditions as in example 2 except that the fly ash used was ball-milled for 10min by a ball mill. The d (0.5) particle size of the fly ash before ball milling is 48.3 mu m, and the d (0.5) particle size of the fly ash after ball milling is 20.1 mu m.

Comparative example 1

This comparative example was compared with example 1, with the modification of Al (OH) in step (3)₃Adjusting Al in tail liquid³⁺Has a molar concentration of 0.68 times SO₄ ^2-Molar concentration and 0 time of Si⁴⁺The molar concentrations are summed to obtain an adjusted tail solution, and the rest conditions are the same as in example 1.

The removal rates of heavy metals in the fly ash from which heavy metals were removed obtained in examples 1 to 5 and comparative examples 1 and 2 were measured, and the results are shown in table 2; the contents of each element and ion in the heavy metal-containing tail liquid are shown in table 3, and the removal rates of each element and ion in the purified tail liquid are shown in table 4.

The method for testing the content of each element and ion in the fly ash for removing heavy metals and the tail liquid containing the heavy metals comprises the following steps: and (3) digesting the fly ash without the heavy metals by using microwaves to prepare a solution sample, measuring the content of the heavy metals in the solution sample by using an inductively coupled plasma mass spectrometry, and measuring the content of silicon, aluminum, calcium, iron and magnesium in the solution sample by using an inductively coupled plasma atomic emission spectrometry. Directly preparing heavy metal-containing tail liquid into a solution sample, measuring the content of heavy metal in the solution sample by adopting an inductively coupled plasma mass spectrometry, measuring the content of silicon, aluminum, calcium, iron and magnesium in the solution sample by adopting an inductively coupled plasma atomic emission spectrometry, and measuring the sulfate radical concentration in the solution sample by adopting a titration method.

TABLE 1

	Cr/(μg/g)	Pb/(μg/g)	As/(μg/g)	Cd/(μg/g)	Hg/(μg/g)
						Example 1	55.49	45.38	12.24	0.45	0.62
Example 2	61.17	77.93	8.29	0.95	0.82
						Example 3	49.82	41.92	6.14	1.24	0.5
Example 4	43.87	84.29	19.89	1.06	1.27

TABLE 2

TABLE 3

TABLE 4

From the test results in the above table, it can be seen that in example 5, after the fly ash is ball-milled, the removal rate of the heavy metals in the fly ash for removing the heavy metals is improved compared with that in example 2, because the ball milling reduces the particle size of the treated fly ash, the fly ash is more fully contacted with the acid solution, the dissolution rate of the heavy metals is improved, and thus the removal rate of the heavy metals is improved. Comparative example 1 from the results of XRD tests shown in fig. 2, only an ettringite phase and no turbidity zeolite phase were contained in the solid phase obtained by solid-liquid separation in step (3), and it can be seen from table 4 that the removal rate of each element in the tail liquid of comparative example 1 was lower than that of example 1.

The applicant declares 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 be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.