Acid wastewater permeable reactive barrier filling material as well as preparation method and application thereof

Abstract

The invention discloses an acid wastewater permeable reactive barrier filling material as well as a preparation method and application thereof, and belongs to the technical field of acid mine wastewater treatment and water environment remediation, the filling material comprises the following components in percentage by mass: 20-60% of modified tailing sand and 40-80% of municipal sludge biochar. According to the permeable reactive barrier filler, the gelling performance and compressive strength of the filler are enhanced through modification of the iron ore tailings, the adsorption capacity of the filler to toxic and harmful metal is increased through the municipal sludge biochar, meanwhile, attached growth of sulfate reducing bacteria is promoted through biochar pores and organic matter contained in the biochar, and the service cycle of the permeable reactive barrier filler is prolonged; the treatment efficiency of the acid wastewater is improved. The composite filler has the characteristics of wide raw material sources, simple preparation process, rich reaction ways and the like, and has a better market application prospect in the aspects of mine wastewater treatment and water environment restoration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acid mine drainage treatment and water environment remediation, in particular to an acid wastewater permeable reactive barrier filling material and a preparation method and application thereof. BACKGROUND

[0002] Acid mine drainage is often associated with the process of mining and utilization of mineral resources, which induces toxic and harmful metal elements into the natural water environment, seriously endangering the safety of the surrounding water environment in the mining area. Lime / limestone neutralization process and sulfate-reducing bacteria microbial treatment process are the most commonly used acid wastewater treatment technologies. However, the neutralization process relies on the addition of a large amount of alkaline substances, has high treatment cost, and has the risk of secondary pollution. The treatment efficiency of the microbial treatment process is low in the acid environment, and the sulfate-reducing bacteria have poor tolerance to metal ions. Therefore, there is still a need for treatment technology with higher adaptability to acid mine drainage.

[0003] Permeable reactive barrier (PRB) is a widely used in-situ treatment technology for waste water, and the main body is a permeable wall that can react with pollutants by physical and chemical, biochemical reactions. For PRB treating acid mine water, the internal reaction medium of the wall is mainly alkaline neutralizing agent, adsorbent material, etc., which mainly achieves the purpose of intercepting and removing pollutants through chemical neutralization reaction, adsorption, precipitation, etc. The treatment effect of PRB on acid wastewater is greatly affected by the performance of the wall filling material, and the filling material needs to have the characteristics of strong acid resistance, stable internal structure, not easy to passivate and blockage, etc. to achieve long-term and stable treatment effect. However, the traditional single medium PRB filling material is easily eroded by acid mine drainage, and the phenomenon of erosion and loss occurs, and it generally has the problems of high cost, difficult recovery and low utilization efficiency.

[0004] Iron mine tailings are relatively stable solid waste materials, which contain alkaline substances remaining after the beneficiation process. The modified tailings have high corrosion resistance and compressive strength, and the mineral components contained therein can combine with metal ions, but the adsorption capacity of the tailings for metals is limited. Municipal sludge activated carbon is an active material with strong adsorption capacity and good biocompatibility, which can release biologically available organic matter, but the toughness and compressive strength are limited. By mixing municipal sludge biochar in the modified tailings, a composite filling material for acid wastewater treatment can be formed, which can combine the material properties of tailings and the adsorption performance of municipal sludge, and provide a part of organic carbon source for attached microorganisms to promote the biochemical coupling of sulfate-reducing bacteria in the PRB treatment system. Therefore, the use of two common solid waste materials, mine tailings and municipal activated sludge, to synthesize PRB filling material has great development space in the efficient treatment of acid mine wastewater. SUMMARY

[0005] The purpose of this invention is to provide a permeable reactive wall filling material for acidic wastewater, its preparation method, and its application. By modifying iron ore tailings sand, the cementitious properties and compressive strength of the filling material are enhanced. By mixing municipal sludge biochar, the adsorption capacity of the filling material for toxic and harmful metals is expanded. Furthermore, the pores and organic matter contained in the biochar promote the attachment and growth of sulfate-reducing bacteria, thereby extending the service life of the permeable reactive wall filling material and improving the treatment efficiency of acidic wastewater.

[0006] To achieve the above objectives, the present invention provides a permeable reactive wall filling material for acidic wastewater, wherein the composition and mass fraction of the filling material are: 20-60% modified tailings sand and 40-80% municipal sludge biochar.

[0007] This invention also provides a method for preparing a permeable reactive wall filling material for acidic wastewater, comprising the following steps:

[0008] S1. Modify iron ore tailings sand under high temperature conditions to obtain modified tailings sand;

[0009] S2. Modified tailings sand and municipal sludge biochar are mixed and compacted to obtain a permeable reactive wall filling material for acidic wastewater.

[0010] Preferably, in S1, the iron ore tailings sand is coarse-grained, loose tailings obtained by concentrating the tailings slurry produced by the mineral processing process.

[0011] Preferably, in S1, the iron ore tailings sand includes calcium sulfate.

[0012] Preferably, in S1, the high temperature condition is 600–800°C.

[0013] Preferably, in S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 20-60% and 40-80%, respectively.

[0014] Preferably, in S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 30-50% and 50-70%, respectively.

[0015] Preferably, in S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 40% and 60%, respectively.

[0016] Preferably, in S2, the mixing method is mechanical stirring.

[0017] The present invention also provides an application of an acidic wastewater permeable reactive wall filling material, wherein the above-mentioned acidic wastewater permeable reactive wall filling material is applied to the preparation of an acidic wastewater permeable reactive wall.

[0018] Therefore, the present invention, employing the above-mentioned acidic wastewater permeable reactive wall filling material, its preparation method, and its application, has the following beneficial effects:

[0019] (1) Use the remaining metal sulfides and alkaline substances in the tailings to treat acidic wastewater, and enhance the cementing performance and compressive strength of the packing through tailings modification.

[0020] (2) The adsorption capacity of the packing material for toxic and harmful metals is expanded by mixing municipal sludge biochar, and the attachment and growth of sulfate-reducing bacteria are promoted by the pores of biochar and the organic matter contained therein, thereby extending the service life of the permeable reactive wall packing material and improving the treatment efficiency of acidic wastewater.

[0021] (3) Composite fillers have the characteristics of wide availability of raw materials, simple preparation process and rich reaction pathways, and have good market application prospects in mine wastewater treatment and water environment restoration.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the preparation and application of a permeable reactive wall filling material for acidic wastewater, its preparation method, and application examples according to the present invention.

[0024] Figure 2 This invention relates to a permeable reactive wall filling material for acidic wastewater, its preparation method, and its application. The diagram shows a simulation experiment of a permeable reactive wall wastewater treatment system composed of permeable reactive wall wastewater filling material in Example 1.

[0025] Figure 3 This invention relates to a permeable reactive wall filling material for acidic wastewater, its preparation method, and its application. The diagram illustrates the treatment of acidic mine wastewater in a permeable reactive wall wastewater treatment system composed of the permeable reactive wall wastewater filling material in Example 1. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] This invention provides a permeable reactive wall filling material for acidic wastewater, its preparation method, and its application. Specific embodiments are as follows:

[0029] Example 1

[0030] A permeable reactive wall filling material for acidic wastewater, comprising the following components and mass fractions: 20% modified tailings sand and 80% municipal sludge biochar.

[0031] like Figure 1 As shown, the preparation method of this acidic wastewater permeable reactive barrier filling material includes the following steps:

[0032] S1. Modified iron ore tailings sand is obtained by modifying it at 600℃. The iron ore tailings sand is a coarse-grained, loose tailings obtained by concentrating tailings slurry produced in the mineral processing process. The iron ore tailings sand contains calcium sulfate. Modification of the iron ore tailings sand with calcium sulfate under high temperature conditions can improve its cementing properties and compressive strength.

[0033] S2. Modified tailings sand and municipal sludge biochar are mixed evenly at a mass ratio of 1:4 and compacted to obtain a permeable reactive wall packing material for acidic wastewater. The addition of municipal sludge biochar expands the packing material's adsorption capacity for toxic and harmful metals, provides attachment sites and organic matter for sulfate-reducing bacteria growth, extends the service life of the permeable reactive wall packing material, and improves the treatment efficiency of acidic wastewater.

[0034] Example 2

[0035] A permeable reactive wall filling material for acidic wastewater, comprising the following components and mass fractions: 40% modified tailings sand and 60% municipal sludge biochar.

[0036] The preparation method of this acidic wastewater permeable reactive wall filling material includes the following steps:

[0037] S1. Modified iron ore tailings sand is obtained by modifying iron ore tailings sand at 700℃. The iron ore tailings sand is coarse-grained, loose tailings obtained by concentrating tailings slurry produced in the mineral processing process. The iron ore tailings sand contains calcium sulfate. Modification of the iron ore tailings sand with calcium sulfate under high temperature conditions can improve the cementing properties and compressive strength of the iron ore tailings sand.

[0038] S2. Mix modified tailings sand and municipal sludge biochar at a mass ratio of 2:3, and compact them to obtain a permeable reactive wall filling material for acidic wastewater.

[0039] Example 3

[0040] A permeable reactive wall filling material for acidic wastewater, comprising the following components and mass fractions: 60% modified tailings sand and 40% municipal sludge biochar.

[0041] The preparation method of this acidic wastewater permeable reactive wall filling material includes the following steps:

[0042] S1. Modified iron ore tailings sand is obtained by modifying the tailings sand at 800℃. The iron ore tailings sand is a coarse-grained, loose tailings obtained by concentrating the tailings slurry produced in the mineral processing process. The iron ore tailings sand contains calcium sulfate. Modification of the iron ore tailings sand with calcium sulfate under high temperature conditions can improve the cementing properties and compressive strength of the iron ore tailings sand.

[0043] S2. Mix modified tailings sand and municipal sludge biochar at a mass ratio of 3:2, and compact them to obtain a permeable reactive wall filling material for acidic wastewater.

[0044] This invention achieves stable and efficient treatment of PRB acidic wastewater based on the following mechanism:

[0045] (1) Neutralization effect of alkaline substances in tailings: The alkaline drugs remaining in the mineral processing process are mixed in the tailings, so that the tailings solid waste has the function of neutralizing acidic wastewater with alkalinity.

[0046] (2) Tailings sand modification stabilizes material structure: The modified tailings sand has higher toughness and compressive strength, which improves the strength of PRB filling material and provides a stable structural space for the mixed adsorbent material.

[0047] (3) Municipal sludge biochar enhances metal ion adsorption: Municipal sludge biochar has a rich pore structure. When mixed with modified tailings, it improves the problem of low strength and makes it more conducive to giving full play to the role of the pore structure and enhancing the adsorption capacity of metal ions.

[0048] (4) Municipal sludge biochar promotes the enrichment of sulfate-reducing bacteria: The porous structure of municipal sludge biochar is conducive to the attachment and growth of microorganisms. The organic matter contained therein can be gradually released. Under the combined action of sulfate ions in the wastewater, it promotes the growth of sulfate-reducing bacteria, thereby achieving the effects of metal ion precipitation and acid neutralization.

[0049] In pyrite, minerals react with oxygen and water to form acidic mine wastewater. This invention simulates the components of acidic mine wastewater and prepares a simulated acidic mine wastewater with an initial pH of 2.4–3.2, an iron content of 800–1200 mg / L, and a manganese content of 95–119 mg / L. The acidic wastewater permeable reactive wall filling material prepared in Example 1 is used to prepare an acidic wastewater permeable reactive wall, and a permeable reactive wall wastewater treatment system is constructed in a multi-stage series configuration to treat the simulated acidic mine wastewater. Figure 2 As shown, the permeable reactive wall wastewater treatment system consists of three permeable reactive walls connected in series, simulating a hydraulic retention time of 24 hours for acidic mine wastewater in each permeable reactive wall.

[0050] Figure 3This illustrates the treatment effect of a permeable reactive wall wastewater treatment system on simulated acidic mine wastewater. Figure 3 (a) in the figure represents the pH change. Figure 3 (b) shows the change in the iron content of the influent. Figure 3 (c) shows the change in the manganese content of the influent. Figure 3 Figure (d) shows the changes in the effluent iron and manganese content. The influent pH of each permeable reactive barrier ranged from 2.4 to 3.2, and the pH of the treated effluent reached 6.9 to 7.6. The iron concentration in the influent of each permeable reactive barrier was 800–1200 mg / L, and the effluent iron concentration ranged from 2.8 mg / L to 4.7 mg / L, with an iron treatment rate of 99.4% to 99.7%. The manganese concentration in the influent of each permeable reactive barrier was 95–120 mg / L, and the effluent manganese concentration ranged from 1.7 mg / L to 3.4 mg / L, with a manganese treatment rate of 96% to 99%. Furthermore, significant microbial attachment was observed in the pores of the composite packing material, indicating that microorganisms, including sulfate-reducing bacteria, played a role in the treatment of acidic mine wastewater. The permeable reactive wall composite filler material proposed in this invention can efficiently treat acidic mine wastewater and has a significant removal effect on metal ions in it.

[0051] Therefore, this invention employs the aforementioned permeable reactive wall filling material for acidic wastewater, its preparation method, and its application. By modifying iron ore tailings sand, the cementitious properties and compressive strength of the filling material are enhanced. By mixing municipal sludge biochar, the adsorption capacity of the filling material for toxic and harmful metals is expanded. Furthermore, the pores and organic matter contained in the biochar promote the attachment and growth of sulfate-reducing bacteria, thereby extending the service life of the permeable reactive wall filling material and improving the treatment efficiency of acidic wastewater.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A permeable reactive wall filling material for acidic wastewater, characterized in that, The composition and mass fraction of the filling material are: 20-60% modified tailings sand and 40-80% municipal sludge biochar.

2. The method for preparing a permeable reactive wall filling material for acidic wastewater as described in claim 1, characterized in that, Includes the following steps: S1. Modify iron ore tailings sand under high temperature conditions to obtain modified tailings sand; S2. Modified tailings sand and municipal sludge biochar are mixed and compacted to obtain a permeable reactive wall filling material for acidic wastewater.

3. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S1, iron ore tailings sand is coarse-grained, loose tailings obtained by concentrating tailings slurry produced during the mineral processing.

4. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S1, the iron ore tailings sand contains calcium sulfate.

5. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S1, the high-temperature conditions are 600–800℃.

6. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 20-60% and 40-80%, respectively.

7. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 30-50% and 50-70%, respectively.

8. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S2, the mass fractions of modified tailings sand and municipal sludge biochar in the acidic wastewater permeable reactive wall filling material are 40% and 60%, respectively.

9. The method for preparing a permeable reactive wall filling material for acidic wastewater according to claim 2, characterized in that, In S2, the mixing method is mechanical stirring.

10. An application of a permeable reactive barrier filling material for acidic wastewater, characterized in that, The acidic wastewater permeable reactive wall filling material according to claim 1 is used to prepare an acidic wastewater permeable reactive wall.

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