Method for removing zinc ions from mine wastewater

Abstract

To provide a method for removing zinc ions from mine wastewater that can suppress the rise in pH of treated water after treatment of mine wastewater and remove zinc ions from mine wastewater while meeting wastewater discharge standards. [Solution] A method for removing zinc ions from mine wastewater, comprising: a first water flow step of passing mine wastewater containing zinc ions through a first treatment tank containing dolomite; and a second water flow step of passing the mine wastewater, after passing through the first water flow step, through a second treatment tank containing concrete material.

Description

[Technical Field]

[0001] This invention relates to a method for removing zinc ions from mine wastewater. [Background technology]

[0002] Mine wastewater discharged from mine entrances and other locations in metal mines is generally highly acidic and contains harmful metals such as zinc ions. Therefore, to prevent mining pollution caused by these substances, mine wastewater is treated by neutralization and other methods.

[0003] For example, Non-Patent Document 1 discloses a method for removing harmful metal elements using a composite channel that combines an open lime channel with an alkaline material channel, using reaction transfer simulations.

[0004] Furthermore, Patent Document 1 discloses a method for removing heavy metal ions from wastewater by packing a column with partially calcined dolomite and passing wastewater containing heavy metal ions through the column. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-240325 [Non-patent literature]

[0006] [Non-Patent Document 1] Journal of MMIJ, "Prediction of Treatment of Acidic Mine Wastewater Using Open Lime-Alkaline Channels and Implications for the Introduction of Passive Treatment," Vol. 138, No. 2, 2022, pp. 19-27. [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the method described in Non-Patent Document 1 had the problem that the pH of the treated water exceeded the wastewater standard value (pH 8.6), making it unsuitable for discharge.

[0008] Therefore, the present invention aims to provide a method for removing zinc ions from mine wastewater that can suppress the rise in pH of treated water after treatment of mine wastewater and remove zinc ions from mine wastewater while meeting wastewater discharge standards. [Means for solving the problem]

[0009] The above objective is achieved by the present invention as described below. [1] The first water flow process involves passing mine wastewater containing zinc ions through a first treatment tank containing dolomite, The second watering step involves passing the mine wastewater, which has been passed through the first watering step, through a second treatment tank containing concrete material. A method for removing zinc ions from mine wastewater, comprising the following components.

[0010] [2] The average particle size D of the dolomite 50 The method for removing zinc ions from mine wastewater as described in [1], wherein the diameter is 3 mm or more.

[0011] [3] The average particle size D of the aforementioned concrete material 50 A method for removing zinc ions from mine wastewater as described in [1], wherein the size is 5 mm or more and 20 mm or less. [4] The method for removing zinc ions from mine wastewater according to [1], wherein the concrete material contains at least 20% by mass of calcium. [5] The method for removing zinc ions from mine wastewater according to [1], wherein the amount of concrete material contained in the second treatment tank is within the range of 0.1 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of dolomite contained in the first treatment tank. [6] The method for removing zinc ions from mine wastewater according to [1], wherein the ratio of magnesium carbonate to calcium carbonate in the dolomite is within the range of 1.1 to 1.7 parts by mass of calcium carbonate with respect to 1 part by mass of magnesium carbonate.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a method for removing zinc ions from mine wastewater that can suppress the increase in pH of the treated water after treating the mine wastewater and remove zinc ions from the mine wastewater while meeting the drainage standards.

Brief Description of the Drawings

[0013] [Figure 1] It is a flowchart of the method for removing zinc ions from mine wastewater according to the embodiment. [Figure 2] It is a schematic configuration diagram of the treatment equipment used in the test of the example. [Figure 3] It is a plan view of the first treatment tank in the treatment equipment used in the test of the example.

Modes for Carrying Out the Invention

[0014] Hereinafter, the method for removing zinc ions from mine wastewater according to the embodiment, which is an exemplary aspect of the present invention, will be specifically described with reference to the drawings. FIG. 1 is a flowchart of the method for removing zinc ions from mine wastewater according to the embodiment.

[0015] As shown in FIG. 1, the method for removing zinc ions from mine wastewater according to the present embodiment includes (1) a first water passing step and (2) a second water passing step, and finally treated water is obtained through these steps.

[0016] (1) First water passing step In the present embodiment, the first water passing step is a step of passing mine wastewater containing zinc ions through a first treatment tank containing dolomite.

[0017] Mine wastewater refers to wastewater discharged from abandoned or closed mines. Mine wastewater contains heavy metal ions such as zinc ions and iron ions, as well as sulfate ions. Mine wastewater containing zinc ions is wastewater with a zinc ion concentration exceeding the discharge standard value (zinc ion content of 2 mg / L) under the Water Pollution Control Law.

[0018] The mine wastewater treated in this embodiment has a zinc ion concentration of 2 mg / L to 100 mg / L and a pH of 5.0 to 7.5. Of course, the zinc ion concentration and pH of the mine wastewater to be treated may be outside these ranges. It may also contain other heavy metal ions such as iron ions or sulfate ions.

[0019] The dolomite used in the first water flow process is a natural mineral or rock containing 54% to 60% calcium carbonate and 36% to 46% magnesium carbonate. The density of dolomite is 2.7 g / cm³. 3 More than 2.9g / cm 3 The following applies. In this embodiment, when converting from volume to mass or from mass to volume of dolomite, the density of dolomite is assumed to be 2.8 g / cm³. 3 I used it.

[0020] The ratio of magnesium carbonate to calcium carbonate in the dolomite contained in the first treatment tank is preferably within the range of 1.1 parts by mass to 1.7 parts by mass of calcium carbonate per 1 part by mass of magnesium carbonate, and more preferably within the range of 1.3 parts by mass to 1.5 parts by mass. If the ratio of calcium carbonate to magnesium carbonate is too low, the dolomite may easily break down, and there is a concern that the gaps between the dolomite particles may become blocked. If it is too high, there is a concern that the amount of bicarbonate ions eluted will decrease.

[0021] A container or channel can be used as the first treatment tank for containing the dolomite. Generally, a container is used if the flow rate of mine wastewater to be treated is small, and a channel is used if the flow rate is large. The container or channel used as the first treatment tank may be open at the top or closed at the top.

[0022] The first treatment tank is a container or channel in which dolomite is contained. In the case of a channel, the dolomite is laid on the surface of the channel. At this time, the amount of dolomite relative to the volume of the first treatment tank is preferably half or more of the volume of the first treatment tank, and more preferably 80% or more by volume. On the other hand, there is no particular upper limit on the amount of dolomite relative to the volume of the first treatment tank, but it is important to note that if there is too much dolomite, the volume occupied by the dolomite in the tank will increase, and the effective volume of the first treatment tank will decrease.

[0023] However, mine wastewater passing at a higher level than the dolomite contained in the first treatment tank may be discharged from the first treatment tank without coming into contact with the dolomite. The flow rate and water quality of mine wastewater fluctuate depending on factors such as climate and season, including after rainfall and during snowmelt. If there is a concern that the amount of bicarbonate ions that can be eluted to remove zinc ions may not be secured due to the flow rate or water quality, it is preferable to fill the first treatment tank with dolomite to full or near full capacity. By filling the tank with dolomite to full capacity, it is possible to suppress the generation of mine wastewater that does not come into contact with the dolomite.

[0024] The amount of dolomite to be placed in the first treatment tank is determined by the flow rate of the mine wastewater and the zinc ion concentration. It is sufficient if the amount is such that at least twice the amount of bicarbonate ions as zinc ions can be eluted. This can be confirmed by taking a small sample of mine wastewater beforehand and conducting preliminary tests. The principle of zinc ion removal is the same even at low flow rates of mine wastewater, so this can be confirmed by preliminary tests. For example, for a mine wastewater flow rate of 0.01 L / min to 100 L / min, the amount of dolomite is 10 kg to 100 t. Generally, for a mine wastewater flow rate of 1 L / min, the amount of dolomite is 1 t.

[0025] The volume of the container or channel used in the first treatment tank should be appropriate to the flow rate of the mine wastewater. For example, the flow rate of mine wastewater is typically between 0.01 L / min and 100 L / min. Generally, the flow rate of mine wastewater is around 1 L / min, and the volume of the first treatment tank should be around 750 L.

[0026] Water is supplied to the first treatment tank by allowing mine wastewater to flow in from the upper end of the first treatment tank and out from the upper end on the opposite side of the tank.

[0027] When mine wastewater is passed through the first treatment tank, it comes into contact with dolomite, and bicarbonate ions, calcium ions, and magnesium ions are leached from the dolomite. Dolomite has the characteristic of leaching slowly compared to other neutralizing agents such as slaked lime. The leached bicarbonate ions, calcium ions, and magnesium ions undergo a neutralization reaction with acidic substances in the mine wastewater, so the pH of the mine wastewater is often 6 to 7. Acidic substances here refer to substances that release hydrogen ions in aqueous solution. Acidic substances in mine wastewater include iron oxides, sulfuric acid, etc., which are produced by the oxidation and dissolution of ore and dissolved in the mine wastewater.

[0028] The average particle size D of the dolomite contained in the first treatment tank. 50 The average particle size D is preferably 3 mm or larger, and more preferably 5 mm or larger. 50 This refers to the particle size at which 50% of the pass-through mass is distributed. Preferably, more than 80% of the particles are 2 mm or larger. The particle size of the dolomite can be measured, for example, using a sieve. Generally, some heavy metal ions, such as iron ions, contained in mine wastewater produce deposits such as hydroxides, and these deposits adhere to the surface of the dolomite. If the particle size of the dolomite is too small, there is a concern that the gaps between the dolomite particles will be blocked by the deposits adhering to the dolomite surface, hindering water flow.

[0029] On the other hand, if the particle size is too large, the contact area with the mine wastewater will be small, raising concerns that the amount of bicarbonate ions eluted will be insufficient. Therefore, the particle size should be adjusted appropriately within a range that does not obstruct water flow. Average particle size D 50 Generally, a diameter of 20 mm or less is preferred, 10 mm or less is more preferred, and 5 mm or less is even more preferred.

[0030] (2)Second water passage process In this embodiment, the second water passing step is to pass the pit wastewater after being passed through the first water passing step into a second treatment tank containing a concrete material with an average particle size D 50 of 5 mm or more and 20 mm or less and containing at least 20% by mass of calcium. By passing through the second water passing step, treated water is finally obtained.

[0031] The concrete material used in the second water passing step is a material made by immersing concrete waste materials in an alkaline solution and then drying and pulverizing them. In this embodiment, when converting from the volume to the mass of the concrete material or from the mass to the volume, a density of 1.0 g / cm 3 is used.

[0032] The concrete material accommodated in the second treatment tank preferably contains at least 20% by mass of calcium, and more preferably 25% by mass or more. The main components of the concrete waste materials that are the raw materials of the concrete material are aggregate and cement, but due to the waste materials, impurities and foreign substances are contained. When the concrete waste materials are immersed in an alkaline solution, the proportion of calcium increases, but the proportion of calcium changes depending on the types and amounts of the contained impurities and foreign substances. If the calcium is too little, there may be many impurities and foreign substances contained in the concrete waste materials, and the impurities and foreign substances may inhibit the removal of zinc ions in the pit wastewater. Note that the upper limit of the calcium amount in the concrete material is 50% by mass.

[0033] As the second treatment tank for accommodating the concrete material, a container or a water channel is used. Generally, a container is used when the flow rate of the pit wastewater to be treated is small, and a water channel is used when it is large. The container or water channel as the second treatment tank may be in an open state or a closed state at the upper part.

[0034] The second treatment tank is a container or channel in which concrete material is contained. In the case of a channel, the concrete material is laid in the channel. At this time, the amount of concrete material relative to the volume of the second treatment tank is preferably half or more of the volume of the second treatment tank, and more preferably 80% or more by volume. On the other hand, the upper limit of the amount of concrete material relative to the volume of the second treatment tank is preferably 100% or less by volume of the volume of the second treatment tank, and more preferably 90% or less by volume.

[0035] Water is supplied to the second treatment tank by allowing the mine wastewater, which has been supplied through the first water supply process, to flow into the second treatment tank from the upper end and out from the upper end opposite the inlet.

[0036] By passing the mine wastewater, which has been passed through the first water flow process, through the second treatment tank, the mine wastewater comes into contact with the concrete material, causing calcium, a cement-derived component in the concrete, to dissolve and the pH of the mine wastewater to rise. This rise in pH removes zinc ions from the mine wastewater. The pH at which zinc ions can be removed is 8.0 or higher, when zinc ions react with carbonate ions or bicarbonate ions and precipitate as zinc carbonate.

[0037] The average particle size D of the concrete material to be placed in the second treatment tank 50 Preferably, the particle size is 5 mm to 20 mm, and more preferably 10 mm to 15 mm. The particle size of the concrete material can be measured, for example, using a sieve. If the particle size of the concrete material is too small, some heavy metal ions, such as iron ions, contained in the mine wastewater may form deposits such as hydroxides, which may adhere to the surface of the concrete material, blocking the gaps between the concrete pieces and hindering water flow.

[0038] Furthermore, if the particle size of the concrete material is too small, the surface area is large, which can cause the pH to rise rapidly and potentially exceed the wastewater standard of pH 8.6. On the other hand, if the particle size of the concrete material is too large, the contact area with the mine wastewater is small, resulting in poor reactivity and making it difficult to raise the pH to 8.0, which is necessary to remove zinc ions.

[0039] The amount of concrete material contained in the second treatment tank is preferably within the range of 0.1 parts by mass to 10 parts by mass, more preferably within the range of 0.5 parts by mass to 5 parts by mass, and even more preferably within the range of 1 part by mass to 2 parts by mass, relative to 100 parts by mass of dolomite contained in the first treatment tank. If the ratio of concrete material to dolomite is too low, the amount of calcium ions leached from the concrete material will be insufficient, making it difficult to raise the pH to 8.0 or higher. On the other hand, if the ratio of concrete material to dolomite is too high, the amount of calcium leached from the concrete material will be excessive, making it easy for the pH to rise to 8.6 or higher.

[0040] The volume of the container or channel used in the second treatment tank should be appropriate to the flow rate of the mine wastewater. Generally, the flow rate of mine wastewater is about 1 L / min, and the volume of the second treatment tank should be about 60 L.

[0041] As previously mentioned, the flow rate and quality of mine wastewater fluctuate depending on factors such as climate and season, including after rainfall and during snowmelt. Therefore, in practice, it is preferable to collect a small amount of mine wastewater in advance and determine the amount and balance of dolomite and concrete material that allows the pH to stably remain between 8.0 and 8.6 through preliminary tests.

[0042] Specifically, the calculation can be done as follows: If the flow rate of mine wastewater is 1 L / min and the first treatment tank has a capacity of 750 L, then to accommodate half of the first treatment tank's capacity, 375 L of dolomite, 500 kg of dolomite is required. Similarly, if the second treatment tank has a capacity of 60 L, then to accommodate half of the second treatment tank's capacity, 30 L of concrete, 5 kg of concrete is required.

[0043] As in this embodiment, adjusting the pH of mine wastewater to between 8.0 and 8.6 makes it possible to remove zinc ions from the mine wastewater. Furthermore, since the pH of the treated water, which is the mine wastewater from which zinc ions have been removed, is 8.6 or lower, which is the discharge standard value, the treated water can be discharged without back-neutralization.

[0044] When the pH of mine wastewater rises, heavy metal ions become plaques such as hydroxides, which then adhere to the surface of dolomite or concrete. Over time, this adhesion can clog gaps between dolomite or concrete pieces, potentially hindering water flow. Alternatively, the adhesion of plaques reduces the surface area that can come into contact with the mine wastewater, making it difficult for the pH of the wastewater to rise. Therefore, it is desirable to perform maintenance regularly (usually once a month) by removing the plaques from the dolomite or concrete, or by replacing the dolomite or concrete.

[0045] Abandoned mines are often located far from urban areas, making visits by workers difficult. Therefore, it is preferable for workers to visit infrequently, and a maintenance frequency of about once a month is ideal.

[0046] Generally, the removal of zinc ions from wastewater, including mine wastewater, is often carried out using the coagulation-sedimentation method, which involves adding an alkaline agent to generate zinc hydroxide, which is then precipitated and removed. In this method, alkaline agents such as caustic soda, slaked lime, and quicklime are used to raise the pH of the wastewater to 9.0-10.5, thereby removing the zinc ions.

[0047] Therefore, since the treated water after zinc ion removal has a pH exceeding the wastewater standard, it is necessary to add acid or other substances to bring the pH within the wastewater standard before discharging it into rivers or other bodies of water. To bring the pH within the wastewater standard, auxiliary equipment such as an additive pump for adding acid and agitators for mixing are required. The added acid needs to be replenished periodically, and the additive pump and agitators also require regular maintenance.

[0048] In contrast, the zinc ion removal method for mine wastewater according to this embodiment does not require the addition of acid or other substances to the treated water after zinc ion removal, and can be discharged as is. Therefore, it does not require any auxiliary equipment and is excellent for application in closed or abandoned mines.

[0049] The flow rate of mine wastewater increases after rainfall and during snowmelt. When the flow rate of mine wastewater increases, the flow velocity increases, and the residence time of the mine wastewater in the first treatment tank decreases. When the residence time decreases, the time that the mine wastewater is in contact with dolomite also decreases. In order to ensure as much opportunity as possible for the mine wastewater to come into contact with dolomite, one or more (for example, five) partition plates can be installed in the first treatment tank, preferably at equal intervals, so that the direction in which the mine wastewater flows meanders horizontally or vertically. If no partition plates are present, they can be installed in a direction intersecting (preferably perpendicular) to the direction in which the mine wastewater flows. [Examples]

[0050] The present invention will be described in more detail below with reference to examples.

[0051] (Preparing mine wastewater) For the test, we prepared mine wastewater from a closed or abandoned mine in Japan. The zinc ion concentration of the mine wastewater was measured using ICP-AES. As a result, the zinc ion concentration of the mine wastewater was 6.3 mg / L. The pH of the mine wastewater was 7.2.

[0052] (Prepare dolomite) The dolomite used for the test was coarsely crushed magnesium carbonate (average particle size D) manufactured by Oji Wood & Greenery Co., Ltd. 50 A sample of dolomite (3 mm) was prepared. The density of this dolomite was 2.8 g / cm³. 3 That was the case.

[0053] (Preparation of concrete materials) For the test, concrete material was prepared by alkali treatment of concrete waste. This concrete material had a calcium content of 29% and a particle size of 5-20 mm (average particle size D). 50 It was 12mm.

[0054] (Processing equipment) Figure 2 shows a schematic diagram of the treatment equipment used in the test of the embodiment. The treatment equipment 1 used in the test of the embodiment mainly consists of a mine wastewater tank 2, a first treatment tank 3, a second treatment tank 4, and a treated water tank 5. The mine wastewater tank 2 and the first treatment tank 3 are connected by piping 7, the first treatment tank 3 and the second treatment tank 4 are connected by piping 8, and the second treatment tank 4 and the treated water tank 5 are connected by piping 9.

[0055] Cylindrical tanks with open tops were used as mine wastewater tank 2 and treatment tank 5. Rectangular tanks with open tops were used as the first treatment tank 3 and the second treatment tank 4. The capacities of mine wastewater tank 2, the first treatment tank 3, the second treatment tank 4, and the treatment tank 5 are 200L (φ550mm × 900mmH), 11L (360mm × 240mm × 130mm), 3L (100mm × 155mm × 175mm), and 200L (φ550mm × 900mmH), respectively.

[0056] A metering pump 6 is incorporated into the piping 7, enabling the transfer of mine wastewater stored in the mine wastewater tank 2 to the first treatment tank 3. A solenoid-type metering diaphragm pump (TSP-100 manufactured by Takato Technica) was used for the metering pump 6.

[0057] Figure 3 shows a plan view of the first treatment tank 3 in the treatment facility 1 used in the embodiment test. The horizontal dimension (hereinafter referred to as the "width direction") in Figure 3 is 360 mm, and the vertical dimension (hereinafter referred to as the "depth direction") is 240 mm. In the first treatment tank 3, the inlet 34 of the piping 7 is located on the left side in Figure 3, and the outlet 35 to the piping 8 is located on the right side. Therefore, the left side in Figure 3 is the upstream side, and the right side is the downstream side.

[0058] Inside the first treatment tank 3, partition plates 31, 32, and 33 are provided at equal intervals (90 mm apart) in the width direction as shown in Figure 3. The partition plates 31, 32, and 33 are installed perpendicular to the direction in which mine wastewater would flow if they were not present (i.e., the width direction). The partition plates 31, 32, and 33 have a depth dimension of 210 mm, which is shorter than the depth dimension of the first treatment tank 3 (240 mm).

[0059] The first processing tank 3 is divided into approximately four chambers by these three partitions. Of these, the partition plate 33 divides the three upstream chambers into a single pre-chamber 37, and the single downstream chamber into a rear chamber 38. 10 kg of dolomite (indicated by 36 in Figure 3) was placed in the pre-chamber (volume 7.5 L) 37. The volume of the dolomite is 3.5 L, and the void volume is 4 L.

[0060] The partition plates 31, 32, and 33 are in contact with the inner wall surface of the first treatment tank 3 on one side, but separated on the other. Specifically, the upstream and downstream partition plates 31 and 33 are in contact with the inner wall surface on the near side in the depth direction, while the intermediate partition plate 32 is in contact with the inner wall surface on the far side in the depth direction. The mine wastewater flowing in from the inlet 34 can move to the next chamber by passing alongside each partition plate 31, 32, and 33, as indicated by the arc-shaped arrows. Therefore, the mine wastewater flows in a meandering manner within the front chamber 37, effectively providing opportunities for contact with dolomite. The mine wastewater that has passed through the front chamber 37 flows directly into the rear chamber 38 and is discharged from the outlet 35, and then flows down through the piping 8 to the second treatment tank 4.

[0061] The inlet of pipe 8 to the second treatment tank 4 is located above one end of the second treatment tank 4 in the longitudinal direction, and the liquid is sent down into the second treatment tank 4. The second treatment tank 4 has a volume of 0.6 L and contains 100 g of the prepared concrete material. The volume of the concrete material is 0.1 L, and the void volume of the second treatment tank 4 is 0.5 L. The other end of the second treatment tank 4 in the longitudinal direction is designed to allow treated water to overflow at a height of 20 cm, and the overflowing treated water is sent to the treated water tank 5 via pipe 9. The treated water tank 5 stores the treated water from which zinc ions have been removed by this equipment.

[0062] (Treatment of mine wastewater) 200 liters of mine wastewater were stored in mine wastewater tank 2. The flow rate of the metering pump 6 was set to 10 ml / min, and the mine wastewater was introduced into the first treatment tank 3 via piping 7 to begin the treatment of the mine wastewater. The average residence time in each tank was approximately 400 minutes for the first treatment tank 3 and approximately 60 minutes for the second treatment tank 4. After continuing the treatment for 7 days, approximately 100 liters of treated water were stored in the treated water tank 5.

[0063] (Measurement of treated water) Treated water stored in treatment tank 5 was collected, and the zinc ion concentration of the treated water was measured using an ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) analyzer. The pH of the treated water was also measured. The results are shown in Table 1 below.

[0064] [Table 1]

[0065] As can be seen in Table 1, by treating the mine wastewater with a zinc ion removal method comprising a first water flow step of passing water through a first treatment tank 3 containing dolomite, and a second water flow step of passing the mine wastewater after passing through the first water flow step through a second treatment tank 4 containing concrete material, it is possible to reduce the zinc ion concentration to 2 mg / L or less while keeping the pH of the treated water below 8.6. Furthermore, by using dolomite with a large average particle size, the gaps between dolomite particles did not become blocked even when debris adhered to the dolomite surface. As a result, it is possible to extend the treatment period without hindering water flow. [Industrial applicability]

[0066] According to the method for removing zinc ions from mine wastewater according to the present invention, treated water can be obtained in which the zinc ion concentration has been reduced to 2.0 mg / L or less, which is within the general wastewater standard value, while maintaining a pH (8.6 or less) within the general wastewater standard value. The obtained treated water can then be discharged directly into rivers or other bodies of water. [Explanation of symbols]

[0067] 1: Processing equipment, 2: Mine wastewater tank, 3: First treatment tank, 4: Second treatment tank, 5: Treatment tank, 6: Metering pump, 7,8,9: Piping, 31, 32, 33: Partition plates, 34: Inlet, 35: Outlet, 36: Dolomite, 37: Vestibule, 38: back chamber

Claims

1. The first water flow process involves passing mine wastewater containing zinc ions through a first treatment tank containing dolomite, The process involves passing the mine wastewater, which has been passed through the first water flow process, through a second treatment tank containing concrete material, and A method for removing zinc ions from mine wastewater, comprising the following components.

2. The average particle size D of the dolomite ５０ The method for removing zinc ions from mine wastewater according to claim 1, wherein the diameter is 3 mm or more.

3. The average particle size D of the aforementioned concrete material ５０ The method for removing zinc ions from mine wastewater according to claim 1, wherein the size is 5 mm or more and 20 mm or less.

4. The method for removing zinc ions from mine wastewater according to claim 1, wherein the concrete material contains at least 20% by mass or more of calcium.

5. The method for removing zinc ions from mine wastewater according to claim 1, wherein the amount of concrete material contained in the second treatment tank is within the range of 0.1 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of dolomite contained in the first treatment tank.

6. The method for removing zinc ions from mine wastewater according to claim 1, wherein the ratio of magnesium carbonate to calcium carbonate in the dolomite is within the range of 1.1 parts by mass or more and 1.7 parts by mass or less of calcium carbonate per 1 part by mass of magnesium carbonate.

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