CN112592720A - Method for preparing composite curing agent by taking fly ash as raw material and application of composite curing agent in repairing mining area soil - Google Patents

Abstract

The invention discloses a method for preparing a composite curing agent for restoring heavy metals in mining area soil by taking fly ash as a raw material, which comprises the following steps: step 1, preparing different types of zeolite molecular sieves by taking fly ash as a raw material; step 2, determining occurrence states of heavy metals in the soil of the mining area to be repaired; step 3, determining the repairing effect of the zeolite molecular sieves of different types prepared in the step 1 on the heavy metals in the mining area soil to be repaired; and 4, compounding different types of zeolite molecular sieves according to the repairing effect obtained in the step 3 to obtain the compound curing agent. The invention realizes the harmless and resource utilization of the fly ash and reduces the land occupation of the fly ash landfill while solving the ecological problem caused by heavy metal in the soil of the mining area.

Description

A method for preparing composite curing agent with fly ash as raw material and its application in repairing soil in mining areas

technical field

The invention relates to the technical field of soil heavy metal pollution remediation, in particular to a method for preparing a composite curing agent using fly ash as a raw material, and the application of the composite curing agent in soil restoration in mining areas.

Background technique

With the development of the national economy and the highly developed industry, the demand for mineral resources has increased, resulting in serious heavy metal pollution in the soil around the mining area. Heavy metal is a persistent and potentially toxic pollutant. The continuous mining of mines by human activities and the random stacking of slag have caused heavy metal pollution to the soil around the mining area. Heavy metals are difficult to be biodegraded after entering the soil. Long-term accumulation will cause the reduction of soil biological activity, resulting in the weakening or even loss of soil ecosystem functions, which will reduce the carrying capacity of the land and affect the activities of surface animals and plants. Moreover, heavy metals in soil have the characteristics of transfer, bioaccumulation and biomagnification along the food chain, which is a long-term and slow accumulation process. Therefore, many scholars have also done a lot of research work on the restoration of heavy metals in mining soil. Due to the advantages of low cost, short remediation time, multi-composite heavy metal pollution, and easy operation, solidification/stabilization technology has become a relatively mature and cost-effective remediation technology for heavy metal-contaminated soils.

Fly ash appears in the waste discharged from thermal power plants and is one of the by-products of coal-fired power generation. Its reasonable resource application is an effective way to solve its pollution. Fly ash contains a large amount of silicon and aluminum, which is similar in composition to zeolite. Using fly ash as raw material to prepare different types of zeolite molecular sieves as curing agents to remediate polluted soil in mining areas is a technology that has both economic and environmental benefits. . However, the currently studied curing agents generally have low passivation stability and single effect, which cannot achieve a good curing effect on the soil to be repaired in different areas, resulting in a low utilization rate.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for preparing a composite curing agent with fly ash as a raw material and its application in repairing the soil in the mining area, so as to solve the ecological problem caused by heavy metals in the soil in the mining area, and at the same time realize that the fly ash is free of Harmful and resource utilization.

To achieve the above object, the technical scheme adopted in the present invention is:

A method for preparing a composite solidifying agent for repairing heavy metals in soil in a mining area by using fly ash as a raw material, comprising the following steps:

Step 1, using fly ash as raw material to prepare different types of zeolite molecular sieves;

Step 2, determine the occurrence state of heavy metals in the soil of the mining area to be repaired;

Step 3, measuring the remediation effect of the different types of zeolite molecular sieves prepared in step 1 to remediate heavy metals in the soil of the mining area;

Step 4, according to the repairing effect obtained in step 3, compound different types of zeolite molecular sieves to obtain a composite curing agent.

In the step 1, the method for preparing the zeolite molecular sieve is a hydrothermal synthesis method, a two-step hydrothermal synthesis method, an alkali fusion hydrothermal method or an acid modification method.

In the step ₁ , different types of zeolite molecular sieves include: 4A zeolite molecular sieve, A1 type zeolite molecular sieve, _A2 type zeolite molecular sieve, _X1 type zeolite molecular sieve, _X2 type zeolite molecular sieve, and P type zeolite molecular sieve.

In the step 2, the content of heavy metals in the soil of the mining area to be repaired and the forms of the contained heavy metals in the soil are determined.

In the step 3, the different types of zeolite molecular sieves prepared in the step 1 are separately applied to the soil in the mining area to be repaired to obtain the repairing effect of the different types of zeolite molecular sieves on one or several heavy metals in the soil.

In the step 4, according to the data measured in the step 3, the proportion of each zeolite molecular sieve required for repairing the soil in the mining area is calculated by the following compounding method, and the composite curing agent is obtained by mixing in proportion;

The compounding method is:

_Excessive heavy metals in the soil to be _repaired : _{n 1} , _{n 2} , _{n 3} .

为吸附土壤中n₁所需N₁的最小投加量，g/kg；in,

The minimum dosage of N ₁ required to adsorb n ₁ in the soil, g/kg;

为n₁在土壤中的含量，mg/kg；

is the content of n ₁ in the soil, mg/kg;

为N₁对n₁的最大吸附量，mg/g；

is the maximum adsorption amount of N ₁ to n ₁ , mg/g;

Similarly, get

由过量系数计算出复合固化剂的配比：If the amount of the composite curing agent added is the sum of f _N , the adsorption capacity of the curing agent will be excessive, so an excess coefficient is introduced.

Calculate the ratio of the composite curing agent from the excess coefficient:

为过量系数，量纲为1；同理，得

in,

is the excess coefficient, and the dimension is 1; in the same way, we get

Find the minimum excess factor

Then the dosage of different zeolite molecular sieves is:

The application of the composite curing agent of the present invention in repairing heavy metals in the soil of a mining area is specifically as follows: uniformly distributing the composite curing agent on the soil of the mining area to be repaired, and then ploughing to make it evenly mixed, stacking and aging for 15- 25d, the repair process is completed. Wherein, the dosage of the composite curing agent is 80-200kg/mu. The heavy metal is one or more of Cd, Pb, Hg, Cu, Cr, and Ni.

Beneficial effects: The present invention uses fly ash as the main raw material, and carries out targeted modification treatment to prepare various curing agents with different properties. Based on the occurrence characteristics of heavy metals in the soil, various curing agents are compounded and used in the soil. Heavy metal solidification and restoration, the method not only solves the ecological problems caused by heavy metals in the soil of the mining area, but also realizes the harmless and resource utilization of fly ash, and reduces the land occupation of fly ash landfill.

Detailed ways

The present invention will be further described below in conjunction with the examples.

A method for preparing a composite solidifying agent for repairing heavy metals in soil in a mining area by using fly ash as a raw material of the present invention comprises the following steps:

Step 1, using fly ash as raw material, prepare different types of zeolite molecular sieves by hydrothermal synthesis method, two-step hydrothermal synthesis method, alkali fusion hydrothermal method or acid modification method in the prior art; Zeolite molecular sieves include _: 4A zeolite molecular sieve, A1 type zeolite molecular sieve, _A2 type zeolite molecular sieve, _X1 type zeolite molecular sieve, _X2 type zeolite molecular sieve, and P type zeolite molecular sieve.

Step 2, measuring the content of heavy metals in the soil of the mining area to be repaired and the forms of the contained heavy metals in the soil.

In step 3, the different types of zeolite molecular sieves prepared in step 1 are separately applied to the soil of the mining area to be repaired to obtain the repairing effects of different types of zeolite molecular sieves on one or several heavy metals in the soil.

Step 4, according to the data measured in step 3, calculate the proportion of each zeolite molecular sieve required for repairing the soil in the mining area by the following compound method, and mix in proportion to obtain a composite curing agent;

Among them, the compound method is:

_Excessive heavy metals in the soil to be _repaired : _{n 1} , _{n 2} , _{n 3} .

为吸附土壤中n₁所需N₁的最小投加量，g/kg；in,

The minimum dosage of N ₁ required to adsorb n ₁ in the soil, g/kg;

为n₁在土壤中的含量，mg/kg；

is the content of n ₁ in the soil, mg/kg;

为N₁对n₁的最大吸附量，mg/g；

is the maximum adsorption amount of N ₁ to n ₁ , mg/g;

Similarly, get

由过量系数计算出复合固化剂的配比：If the amount of the composite curing agent added is the sum of f _N , the adsorption capacity of the curing agent will be excessive, so an excess coefficient is introduced.

Calculate the ratio of the composite curing agent from the excess coefficient:

为过量系数，量纲为1；同理，得

in,

is the excess coefficient, and the dimension is 1; in the same way, we get

Find the minimum excess factor

Then the dosage of different zeolite molecular sieves is:

The present invention will be further described below in conjunction with the embodiments.

Example 1

Prepare different types of zeolite molecular sieves with fly ash as raw material; determine the occurrence state of heavy metals in the soil of the mining area to be rehabilitated; determine the remediation effect of different types of adsorption materials on the heavy metals in the soil of the mining area; from the measured data, compound and prepare a composite type of curing agent. The restoration site is the soil of a mining area in Xuzhou.

Different types of zeolite molecular sieves include: 4A zeolite molecular sieve, A ₁ type zeolite molecular sieve, A ₂ type zeolite molecular sieve, X type zeolite molecular sieve, and P type zeolite molecular sieve.

The content of heavy metals in the soil of the mining area to be restored is determined in Table 1;

Table 1: Content of heavy metals in the soil of the mining area to be rehabilitated

Heavy metal elements Cd, Hg, Cu and Pb, whose elements exist in acid extractable state, reducible state and oxidizable state account for 59.4%-78.6% of their element content; Cr and Ni elements account for relative residual state content more.

The described determination of the remediation effect of different types of zeolite molecular sieves on heavy metals in the soil of the mining area is specifically as follows: the prepared different types of zeolite molecular sieves are respectively applied to the soil of the mining area to be repaired to obtain the effect of different adsorption materials on one or several heavy metals in the soil. The repair effect is shown in Table 2.

Table 2: The results of the soil in the mining area to be rehabilitated by the action of different adsorbent materials

From the data obtained from the above two steps, the required proportion of single zeolite molecular sieve is calculated by the compounding method provided by the present invention, wherein: 4A zeolite molecular sieve 8%, A ₁ type zeolite molecular sieve 23%, A ₂ type zeolite molecular sieve 17% %, X ₁ type zeolite molecular sieve 8%, X ₂ type zeolite molecular sieve 26%, P type zeolite molecular sieve 18%; mixed in proportion to obtain the required composite curing agent.

The composite curing agent was evenly distributed on the polluted soil in the proportion of 120kg/mu, and then ploughed to make it evenly mixed, stacked and aged for 20 days to complete the restoration process. The content of heavy metals in soil after restoration is shown in Table 3.

Table 3: Content of heavy metals in the soil of the mining area after the composite curing agent has been repaired

Example 2

Prepare different types of zeolite molecular sieves with fly ash as raw material; determine the occurrence state of heavy metals in the soil of the mining area to be repaired; determine the remediation effect of different types of zeolite molecular sieves on the heavy metals in the soil of the mining area; from the measured data, compound and prepare a composite type of curing agent. The restoration site is the soil of a mining area in Xuzhou.

Different types of zeolite molecular sieves include: 4A zeolite molecular sieve, A ₁ type zeolite molecular sieve, A ₂ type zeolite molecular sieve, X type zeolite molecular sieve, and P type zeolite molecular sieve.

The content of heavy metals in the soil of the mining area to be restored is determined in Table 4;

Table 4: Content of heavy metals in the soil of the mining area to be rehabilitated

Heavy metal elements Hg, Cu, Cd and Cr, whose elements exist in acid extractable state, reducible state and oxidizable state account for 56.3%-79.1% of their element content; Pb and Ni elements account for relative residual state content more.

The prepared different types of zeolite molecular sieves were respectively applied to the soil of the mining area to be repaired, and the repairing effects of different adsorption materials on one or several heavy metals in the soil were obtained as shown in Table 5.

Table 5: The results of the soil in the mining area to be rehabilitated by the action of different adsorbent materials

From the data obtained from the above two steps, the ratio of the required single adsorbent material is calculated by the compounding method provided by the present invention, wherein: 18% of 4A zeolite molecular sieve, ₂₆ % of A1 type zeolite molecular sieve, ₁₀ % of A2 type zeolite molecular sieve %, X ₁ type zeolite molecular sieve 9%, X ₂ type zeolite molecular sieve 24%, P type zeolite molecular sieve 13%; mixed in proportion to obtain the required composite curing agent.

The composite curing agent is evenly distributed on the polluted soil at the proportion of 150kg/mu, and then ploughed to make it evenly mixed, stacked and aged for 18 days to complete the restoration process. The content of heavy metals in soil after remediation was determined in Table 6.

Table 6: Contents of heavy metals in the soil of the mining area after remediation by the composite curing agent

The above-mentioned embodiments are only some preferred solutions of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the technical solutions of the present invention may be modified or equivalently replaced, and these modifications and equivalent replacements should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method for preparing a composite curing agent for restoring heavy metals in mining area soil by taking fly ash as a raw material is characterized by comprising the following steps: the method comprises the following steps:

step 1, preparing different types of zeolite molecular sieves by taking fly ash as a raw material;

step 2, determining occurrence states of heavy metals in the soil of the mining area to be repaired;

step 3, determining the repairing effect of the zeolite molecular sieves of different types prepared in the step 1 on the heavy metals in the mining area soil to be repaired;

and 4, compounding different types of zeolite molecular sieves according to the repairing effect obtained in the step 3 to obtain the compound curing agent.

2. The method for repairing heavy metals in mining area soil by using fly ash as a raw material and preparing a compound curing agent according to claim 1, which is characterized in that: in the step 1, the method for preparing the zeolite molecular sieve is a hydrothermal synthesis method, a two-step hydrothermal synthesis method, an alkali fusion hydrothermal method or an acid modification method.

3. The method for repairing heavy metals in mining area soil by using fly ash as a raw material and preparing a compound curing agent according to claim 1, which is characterized in that: in step 1, the different types of zeolite molecular sieves include: 4A Zeolite molecular Sieve, A₁Zeolite type molecular sieves, A₂Zeolite type molecular sieve, X₁Zeolite type molecular sieve, X₂Zeolite type molecular sieve, P type zeolite molecular sieve.

4. The method for repairing heavy metals in mining area soil by using fly ash as a raw material and preparing a compound curing agent according to claim 1, which is characterized in that: in the step 2, the content of heavy metals in the mining area soil to be restored and the form of the contained heavy metals in the soil are determined.

5. The method for repairing heavy metals in mining area soil by using fly ash as a raw material and preparing a compound curing agent according to claim 1, which is characterized in that: in the step 3, the zeolite molecular sieves of different types prepared in the step 1 are respectively and independently acted on the soil of the mining area to be repaired, so that the repairing effect of the zeolite molecular sieves of different types on one or more heavy metals in the soil is obtained.

6. The method for repairing heavy metals in mining area soil by using fly ash as a raw material and preparing a compound curing agent according to claim 1, which is characterized in that: in the step 4, according to the data measured in the step 3, the proportion of each zeolite molecular sieve required for restoring the soil of the mining area is calculated by the following compounding method, and the composite curing agent is obtained by mixing the zeolite molecular sieves in proportion;

the compounding method comprises the following steps:

and (3) exceeding heavy metals in the soil to be repaired: n is₁、n₂、n₃…n_iIt corresponds to zeolite molecular sieve with best adsorption effect respectively: n is a radical of₁、N₂、N₃…N_iThen, then

Wherein,

for adsorbing n in soil₁Required N₁The minimum dosage of (2), g/kg;

is n₁Content in soil, mg/kg;

is N₁To n₁Maximum adsorption amount of (2), mg/g;

by the same way, obtain

If the amount of the composite curing agent added is f_NIn total, the adsorption capacity of the curing agent is excessive, thereby introducing an excessive factor

The proportion of the composite curing agent is calculated by the excess coefficient:

wherein,

is an excess factor, dimension 1; by the same way, obtain

Finding the minimum excess coefficient

The adding amount of the different zeolite molecular sieves is as follows:

7. a composite type curing agent prepared according to the method of any one of claims 1 to 6.

8. The application of the compound curing agent of claim 7 in repairing heavy metals in mine soil.

9. Use according to claim 7, characterized in that: and uniformly spreading the composite curing agent on the soil of the mining area to be repaired, ploughing, uniformly mixing, stacking and aging for 15-25d, and finishing the repairing process.

10. Use according to claim 8, characterized in that: the dosage of the compound curing agent is 80-200 kg/mu, and the heavy metal is one or more of Cd, Pb, Hg, Cu, Cr and Ni.