A composite medium filling material for mine site acidic surface runoff interception ditch and application thereof

Abstract

The application discloses a mine area acid surface runoff interception ditch composite medium filling material and application. The application adopts biochar and natural non-metallic mineral material in a certain particle size range and is compounded according to a certain volume ratio, and the filling material obtained through the compounding has a good composite heavy metal removal effect, and a permeability coefficient is greater than 10 ‑3 cm / s, so that the problem that the permeability coefficient of the filling material of the interception ditch and the composite heavy metal pollutant removal effect are difficult to coordinate is solved, and the mine area acid surface runoff process blocking treatment is particularly suitable, and reliable technical support can be provided for scientific treatment and engineering optimization of the mine area acid surface runoff.

Description

Technical Field

[0001] This invention relates to the field of water environment management technology, specifically to a composite medium filling material and its application as a filling material for intercepting acidic surface runoff in mining areas. Background Technology

[0002] Sulfide minerals in mine waste rock dumps, open-pit mine slopes, and spoil heaps, under the oxidation of microorganisms and leached by rainwater, generate large amounts of acidic surface runoff containing heavy metal ions, causing serious pollution to the surrounding soil and surface / groundwater environment. Currently, the main technologies for controlling acidic surface runoff in mining areas include source control, process interruption, and end-of-pipe treatment. Process interruption often employs interception trench technology filled with heavy metal adsorption materials. However, current filling materials often exhibit problems such as good permeability but poor heavy metal removal efficiency, or vice versa. There is an urgent need to develop a method for synergistically regulating the permeability of the interception trench filling material with the heavy metal pollutant removal performance, in order to achieve the goal of efficient removal of complex heavy metal pollution from acidic surface runoff in mining areas while ensuring the interception trench filling material has a high permeability and is less prone to clogging. Summary of the Invention

[0003] The purpose of this invention is to address the problem of the difficulty in synergistically improving the permeability and heavy metal removal efficiency of existing interception trench filling materials, and to provide a composite medium filling material for interception trenches in acidic surface runoff in mining areas and its application. Based on the adsorption and removal of composite heavy metals from acidic surface runoff in mining areas by fine-particle biochar, this invention fully utilizes mineral particles with a certain adsorption effect on heavy metals and a larger particle size to regulate the porosity of the interception trench filling material, thereby increasing the water flow velocity and permeability, and maximizing both permeability and the removal rate of composite heavy metals. Specifically, it uses biochar of different particle sizes and organically combines it with zeolite, bentonite, and vermiculite of different particle sizes to form multiple groups of "combined materials." Through experimental testing and adjustment of the permeability and heavy metal removal rate of these combined materials, the optimal combination with both excellent permeability and heavy metal removal efficiency is selected. This combined material can achieve a permeability greater than 10. -3 The optimal synergistic target of achieving a removal rate of over 85% for composite heavy metals such as copper, lead, and cadmium ions at a speed of cm / s is achieved, breaking through the technical bottleneck of poor permeability in traditional interception trench backfill materials for efficient adsorption and removal of composite heavy metals in acidic mine surface runoff.

[0004] The technical solution adopted in this invention is as follows:

[0005] A composite medium filling material is composed of natural non-metallic mineral materials and biochar mixed in a volume ratio of (1~5):(9~5); the natural non-metallic mineral materials are two or three of natural clinoptilolite, bentonite and vermiculite; the biochar is a porous material obtained by oxygen-limited pyrolysis of agricultural and forestry waste.

[0006] The natural mineral materials are chosen with a relatively coarse particle size to increase the porosity of the intercepting trench filling material by interspersing fine biochar particles, thereby improving the permeability coefficient of the filling material. Furthermore, the mineral materials themselves have a certain adsorption capacity for heavy metal ions under acidic conditions. The biochar is chosen with a fine particle size because biochar itself has a strong adsorption capacity for heavy metals, and the finer the particle size, the stronger the adsorption and removal capacity for heavy metal ions. Choosing a fine particle size ensures that the intercepting trench achieves good removal efficiency for heavy metals.

[0007] Preferably, the particle size range of the natural non-metallic mineral material is -2.0 mm to +0.5 mm; and the particle size range of the biochar is -0.25 mm to +0.074 mm.

[0008] Preferably, the oxygen-limited pyrolysis is performed by pyrolysis at a pyrolysis temperature of 500°C and a heating rate of 10°C / min under a nitrogen atmosphere for 1 hour.

[0009] Preferably, the biochar is alfalfa pyrolysis biochar.

[0010] This invention also provides the application of the above-mentioned composite medium filling material as a filling material for intercepting acidic surface runoff in mines.

[0011] Preferably, the pH of the acidic surface runoff from the mine is less than 4.5, and the composite pollutants in the acidic surface runoff from the mine include heavy metals such as copper ions, cadmium ions, lead ions, and sulfate ions.

[0012] Mining areas experience significant flows of acidic surface runoff, especially during the rainy season. Therefore, the composite materials used for filling interception trenches must possess excellent permeability and a high capacity for removing heavy metal pollutants. Existing technologies using composite materials for interception trench filling, such as large-particle gravel and zeolite, while exhibiting good permeability, suffer from poor heavy metal pollutant removal capabilities. While fine-particle biochar offers good heavy metal removal, its poor permeability leads to clogging after a period of operation. The composite material for interception trench filling provided by this invention not only demonstrates excellent heavy metal pollutant removal but also boasts a high permeability coefficient, making it particularly suitable for intercepting and treating complex heavy metal pollution from acidic surface runoff in mining areas.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. This invention proposes a composite medium filling material, which is a combination of biochar with different particle sizes and natural non-metallic mineral materials in a certain volume ratio. The resulting filling material not only has a good composite heavy metal removal effect, but also has a permeability coefficient greater than 10. -3cm / s, effectively solving the contradiction between the removal effect of composite heavy metals in interception trenches and the permeability coefficient, is particularly suitable for the application of interception trenches to treat composite heavy metal pollution in acidic surface runoff in mining areas, and has excellent pollution removal performance and economic applicability.

[0015] 2. The composite medium filling material in this invention has a wide range of raw material sources, low cost, and is easy to apply in engineering. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments.

[0017] In the following examples, the composite medium filling material of the present invention is used for pH=3.5, containing Cu 2+ 10 mg / L, Cd 2+ 0.05 mg / L, Pb 2+ Acidic surface runoff from the mining area at a concentration of 0.6 mg / L was treated. The permeability coefficient was determined using a constant head permeability test. The alfalfa pyrolysis biochar in this example was prepared by pyrolyzing alfalfa as raw material at a pyrolysis temperature of 500℃ and a heating rate of 10℃ / min under a nitrogen atmosphere for 1 hour. The particle size of the mineral material was optimized through experimental research.

[0018] Example 1

[0019] S1. The biochar selected is alfalfa pyrolysis biochar with a particle size of -0.15mm +0.075mm. Two mineral materials are selected: natural clinoptilolite and vermiculite, both with a particle size of -2mm +1mm.

[0020] S2. Mix 0.7L of alfalfa pyrolysis biochar with 0.2L of natural clinoptilolite and 0.1L of vermiculite in a beaker until homogeneous.

[0021] S3. Take 0.5L of the above mixed medium for permeability coefficient determination, and conduct dynamic adsorption test of acidic surface runoff composite heavy metals in 0.5L of mixed medium. The effective volume of the interception ditch is 0.6L, the adsorption time is 2 hours, the influent flow rate is 250ml / hour, and after reaching adsorption equilibrium, take the supernatant and determine the heavy metal ion concentration using ICP-MS.

[0022] Example 2

[0023] S1. The biochar selected is alfalfa pyrolysis biochar with a particle size of -0.15mm +0.075mm. Two mineral materials are selected: natural clinoptilolite and vermiculite, both with a particle size of -2mm +1mm.

[0024] S2. Mix 0.8L of alfalfa pyrolysis biochar with 0.1L of natural clinoptilolite and 0.1L of vermiculite in a beaker until homogeneous.

[0025] S3. Take 0.5L of the above mixed medium for permeability coefficient determination, and conduct dynamic adsorption test of acidic surface runoff composite heavy metals in 0.5L of mixed medium. The effective volume of the interception ditch is 0.6L, the adsorption time is 2 hours, the influent flow rate is 250ml / hour, and after reaching adsorption equilibrium, take the supernatant and determine the heavy metal ion concentration using ICP-MS.

[0026] Example 3

[0027] S1. The biochar was selected as alfalfa pyrolysis biochar with a particle size of -0.15mm +0.075mm. Three mineral materials were selected as natural clinoptilolite, vermiculite and bentonite, all with a particle size of -2mm +1mm.

[0028] S2. Mix 0.6 L of alfalfa pyrolysis biochar with 0.1 L of natural clinoptilolite, 0.1 L of vermiculite, and 0.1 L of bentonite in a beaker until homogeneous.

[0029] S3. Take 0.5L of the above mixed medium for permeability coefficient determination, and conduct dynamic adsorption test of acidic surface runoff composite heavy metals in 0.5L of mixed medium. The effective volume of the interception ditch is 0.6L, the adsorption time is 2 hours, the influent flow rate is 250ml / hour, and after reaching adsorption equilibrium, take the supernatant and determine the heavy metal ion concentration using ICP-MS.

[0030] Comparative Example 1

[0031] The preparation method is the same as in Example 1, except that Comparative Example 1 only uses alfalfa pyrolysis biochar and does not use the two mineral materials.

[0032] Comparative Example 2

[0033] The preparation method is the same as in Example 1, except that Comparative Example 2 uses only two mineral materials and does not use alfalfa pyrolysis biochar.

[0034] The methods used for the dynamic adsorption test of composite heavy metals in acidic surface runoff in Comparative Examples 1 and 2 were the same as those in Example 1. The experimental results of Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0035] Table 1. Permeability coefficient and heavy metal removal efficiency of filling materials with different ratios

[0036]

[0037] Results Analysis: As shown in Table 1, the interception trench filling materials of Examples 1-3, under a water flow rate of 250 ml / h, all exhibited adsorption and removal rates of more than 85% for heavy metal ions (copper, cadmium, and lead), and permeability coefficients greater than 1×10⁻⁶. -3 The speed of cm / s fully meets the target requirements of engineering applications. This indicates that the interception trench filling material of this application has a strong adsorption and removal capacity for composite heavy metals and good permeability, which can solve the problem of good heavy metal removal effect but easy clogging of previously reported interception trench filling materials, and is conducive to industrial application.

[0038] Comparative Examples 1 and 2 demonstrate that only filling materials obtained through the material type, particle size, and volume ratio control methods specified in this application can achieve both excellent permeability coefficient of the interception trench and high adsorption and removal rate of composite heavy metal pollutants.

[0039] This specification is intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.

Claims

1. A composite medium filling material, characterized in that, It is composed of natural non-metallic mineral materials and biochar in a volume ratio of (1~5):(9~5); the natural non-metallic mineral materials are two or three of natural clinoptilolite, bentonite and vermiculite; the biochar is a porous material obtained by oxygen-limited pyrolysis of agricultural and forestry waste.

2. The composite medium filling material according to claim 1, characterized in that, The particle size range of the natural non-metallic mineral material is -2.0 mm to +0.5 mm; the particle size range of the biochar is -0.25 mm to +0.074 mm.

3. The composite medium filling material according to claim 1, characterized in that, The volume ratio of two of the natural clinoptilolite, bentonite and vermiculite is (7~5):(3~5), and the volume ratio of the three is 1:1:

1.

4. The composite medium filling material according to claim 1, characterized in that, The oxygen-limited pyrolysis is performed by pyrolysis at a temperature of 500℃ and a heating rate of 10℃ / min under a nitrogen atmosphere for 1 hour.

5. The composite medium filling material according to claim 1, characterized in that, The biochar is alfalfa pyrolysis biochar.

6. The application of the composite medium filling material according to any one of claims 1-3 as a filling material for acidic surface runoff interception ditches in mining areas.

7. The application according to claim 4, characterized in that, The pH of the acidic surface runoff in the mining area is less than 4.5, and the composite pollutants in the acidic surface runoff include heavy metals such as copper ions, cadmium ions, lead ions, and sulfate ions.

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