Ph adjusting material

Abstract

To improve a technique for purifying groundwater.SOLUTION: The pH adjusting material is used for increasing the pH of the groundwater and is previously molded or formed into a rod-like shape adaptable to a boring hole provided in the basin of the groundwater containing iron ions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to pH adjusters. [Background technology]

[0002] It is said that there are around 6,000 abandoned mines in Japan, of which around 80 are still generating mine wastewater. Although the quality of mine wastewater is gradually improving through various measures, it is expected to take a considerable amount of time, effort, and expense until the mine wastewater from all abandoned mines meets the effluent standards. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-336838 Summary of the Invention [Problem to be solved by the invention]

[0004] There are many abandoned mines where the original mining companies have ceased to exist and there is no one to take responsibility for mine wastewater treatment. In these abandoned mines, local governments are left to treat the mine wastewater with government subsidies. Technology is needed to improve the efficiency of mine wastewater treatment and reduce costs.

[0005] The present disclosure has been made in view of these problems, and its purpose is to improve techniques for purifying groundwater. [Means for solving the problem]

[0006] To solve the above problems, a pH adjuster according to one embodiment of the present disclosure is intended to increase the pH of groundwater, and is pre-molded or formed into a rod-like shape that can fit into a borehole located in a basin of groundwater containing iron ions. [Effects of the Invention]

[0007] The present disclosure provides improved techniques for purifying groundwater. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a purification facility as an example of a structure according to an embodiment of the present disclosure; [Figure 2] 1 is a flowchart showing the steps of a cleaning method according to an embodiment of the present disclosure. [Figure 3] FIG. 10 is a diagram illustrating another example of a purification facility according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this disclosure, techniques for purifying groundwater containing metal ions, such as iron ions, are described.

[0010] 1 is a schematic diagram of a purification facility 10, which is an example of a structure according to an embodiment of the present disclosure. The purification facility 10 is installed underground to purify mine wastewater 3 flowing from an abandoned mine 1 having an abandoned mine 2. The purification facility 10 includes a borehole 4 drilled in the catchment area of ​​the mine wastewater 3, which contains metal ions such as iron ions, and a pH adjuster 5 installed inside the borehole 4.

[0011] Mine wastewater 3 flowing out of an abandoned mine 1 generally contains concentrated sulfuric acid and is acidic. Iron ions dissolve in acidic mine wastewater 3, but are almost insoluble in neutral to alkaline conditions. Instead, they precipitate or form colloids in the form of α-, β-, γ-, or δ-iron oxyhydroxide, iron(III) oxide, or iron(III) hydroxide. pH adjuster 5 contains compounds such as calcium carbonate, which dissolves in water to become alkaline, in order to increase the pH of the groundwater flowing into borehole 4 and precipitate or form colloids of iron ions. Iron compounds 6, including precipitated iron compounds and colloidal iron compounds in the process of precipitating, are adsorbed on the surface of pH adjuster 5.

[0012] 2 is a flowchart showing the steps of a purification method according to an embodiment of the present disclosure. A borehole 4 is drilled in a basin of groundwater, such as mine wastewater 3, containing iron ions (S10). A pH adjuster 5 is provided inside the borehole 4 (S12). Purification facility 10 is constructed according to the above steps.

[0013] When groundwater containing iron ions flows into the borehole 4 and comes into contact with the surface of the pH adjuster 5, compounds such as calcium carbonate contained near the surface of the pH adjuster 5 dissolve in the water, and a neutralization reaction occurs, raising the pH of the groundwater near the pH adjuster 5. As a result, the iron ions dissolved in the groundwater precipitate or form colloids near the pH adjuster 5 (S14). Iron colloids in the process of precipitating, and precipitated amorphous or crystallized iron compounds, are adsorbed onto the surface of the pH adjuster 5. This is the same process as iron concretion.

[0014] Iron concretions are formed when iron ions contained in acidic groundwater precipitate on the surface of a spherical core of calcite or other material, forming a shell of iron oxide. When iron concretions form, the sediment fills minute voids in the strata and soil, reducing the porosity by approximately 80-90%. The formed iron concretions are insoluble in water in the neutral to slightly alkaline environment of the earth's surface, and remain stable for long periods of time.

[0015] When the iron ions contained in the mine wastewater 3 precipitate or colloidize as the pH of the mine wastewater 3 is increased by the pH adjuster 5 and are adsorbed onto the surface of the pH adjuster 5, it is thought that, similar to iron concretions, they are fixed to the surface of the pH adjuster 5 while sealing voids inside and around the pH adjuster 5. Therefore, the purification equipment 10 of this embodiment can reduce the concentration of iron ions contained in the mine wastewater 3 and can also reduce the flow rate of the mine wastewater 3 flowing downstream.

[0016] Iron oxides are known to co-precipitate heavy metal compounds when they precipitate or form colloids. Therefore, they can reduce the concentrations of not only iron ions in the mine wastewater 3, but also heavy metal ions such as lead (Pb), cadmium (Cd), and arsenic (As), and light metal ions such as aluminum (Al).

[0017] The pH adjuster 5 includes at least one of calcium carbonate, calcium bicarbonate, calcium oxide, and calcium hydroxide. The pH adjuster 5 may include concrete, cement, cement clinker, alite, belite, aluminate, ferrite, etc.

[0018] The pH adjusting material 5 may be in the form of a powder or particles. In this case, in S12, the pH adjusting material 5 may be injected into the borehole 4. The pH adjusting material 5 may be injected from the bottom of the borehole 4 using a boring rod, or the pH adjusting material 5 may be injected from the top of the borehole 4 after the borehole 4 has been drilled.

[0019] The particle size, surface area, porosity, amount of the pH adjuster 5, the type and amount of compounds contained in the pH adjuster 5, etc. may be adjusted according to the flow rate, flow velocity, catchment area, pH, type and concentration of metal ions contained in the mine wastewater 3, etc.

[0020] The pH adjusting material 5 may be pre-formed into a rod-like shape that can fit into the borehole 4. The pH adjusting material 5 may be formed using a mold that fits the shape of the borehole 4, or may be formed using any other method. In this case, the pH adjusting material 5 may be inserted into the borehole 4 in S12.

[0021] The shape, diameter, surface area, length, type and amount of compounds contained in the pH adjuster 5, etc. may be adjusted according to the flow rate, flow velocity, catchment area, pH, type and concentration of metal ions contained in the mine wastewater 3, etc.

[0022] A plurality of boreholes 4 may be provided. For example, as shown in Figure 1, a plurality of first boreholes 4a may be provided upstream of the drainage basin of the mine wastewater 3, and a second borehole 4b may be provided downstream of the flow path of the mine wastewater 3 that flows between the plurality of first boreholes 4. This makes it possible to more effectively reduce the flow rate and metal ion concentration of the mine wastewater 3 flowing downstream.

[0023] The number, diameter, shape, depth, etc. of the boreholes 4 may be adjusted according to the flow rate, flow velocity, catchment area, pH, type and concentration of metal ions contained in the mine wastewater 3, etc., of the mine wastewater 3, and the treatment policy for the mine wastewater 3. The treatment policy for the mine wastewater 3 may be, for example, treatment whose main purpose is to reduce the heavy metal ions contained in the mine wastewater 3, treatment whose main purpose is to reduce the flow rate of the mine wastewater 3 downstream, etc.

[0024] FIG. 3 shows another example of a purification system 10 according to an embodiment of the present disclosure. FIG. 3(a) shows an example of the arrangement of boreholes 4 when the main purpose is to reduce the heavy metal ions contained in the mine wastewater 3. The intervals between the boreholes 4 on the downstream side are wider than those on the upstream side, so that heavy metal ions that could not be precipitated or converted into colloids on the upstream side are captured on the downstream side. This makes it possible to effectively reduce the concentration of heavy metal ions contained in the mine wastewater 3 while ensuring an appropriate flow path for groundwater.

[0025] Figure 3(b) shows an example of the arrangement of boreholes 4 when the main purpose is to reduce the flow rate of mine wastewater 3 downstream. The spacing between boreholes 4 is narrower than in the case shown in Figure 3(a), strengthening the sealing of the flow path of mine wastewater 3. This makes it possible to effectively reduce the flow rate of mine wastewater 3 flowing downstream of the purification facility 10.

[0026] The present disclosure has been described above based on examples. These examples are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0027] Although the embodiments have mainly described techniques for purifying mine wastewater, the techniques of the present disclosure can be used to purify any groundwater that contains heavy metal ions such as iron ions.

[0028] An outline of one aspect of the present disclosure is as follows.

[0029] A purification method according to one embodiment of the present disclosure includes the steps of creating a hole in a basin of groundwater containing iron ions, placing a pH adjuster inside the hole to increase the pH of the groundwater, and precipitating the iron ions contained in the groundwater that has flowed into the hole. This reduces the iron ions contained in the groundwater. In this disclosure, the term "hole" includes a hole with a bottom. Furthermore, "providing" a pH adjuster includes terms such as "filling," "injecting," "putting," "inserting," and "encapsulating," depending on the form of the pH adjuster.

[0030] In this purification method, the precipitated iron compounds are adsorbed onto the surface of the pH adjuster, which fixes the iron compounds so that they do not flow downstream.

[0031] A purification method according to another aspect of the present disclosure includes the steps of providing a hole in a basin of groundwater containing iron ions, providing a pH adjuster inside the hole to increase the pH of the groundwater, and colloidizing the iron ions contained in the groundwater that has flowed into the hole, thereby reducing the iron ions contained in the groundwater.

[0032] In this purification method, colloidal iron compounds are adsorbed onto the surface of the pH adjuster, which fixes the iron compounds so that they do not flow downstream.

[0033] In this purification method, heavy metal compounds that co-precipitate with iron compounds are adsorbed onto the surface of the pH adjuster, thereby immobilizing the heavy metal compounds so that they do not flow downstream.

[0034] The pH adjuster may include at least one of calcium carbonate, calcium bicarbonate, calcium oxide, and calcium hydroxide, which can reduce the cost of purifying groundwater.

[0035] The pH adjuster may be in a powder or granular form, which allows selection of a form suitable for the environment in which the pH adjuster is installed, thereby enabling efficient purification of groundwater while keeping costs down.

[0036] The pH adjuster may be rod-shaped. This allows the selection of a shape suitable for the environment in which the pH adjuster is to be installed, thereby reducing costs and efficiently purifying groundwater. Furthermore, by precasting the pH adjuster into a shape (e.g., rod-shaped) that fits the shape of the hole, the efficiency of the work of installing the pH adjuster can be improved.

[0037] A plurality of holes may be provided, and the plurality of holes may include a plurality of first holes provided upstream of the groundwater basin and a second hole provided downstream of the groundwater flow path that flows between the plurality of first holes. This makes it possible to more effectively reduce the amount of iron ions flowing downstream.

[0038] A structure according to an embodiment of the present disclosure includes a hole present in a basin of groundwater containing iron ions, and a pH adjuster present inside the hole for increasing the pH of the groundwater, thereby reducing the iron ions contained in the groundwater.

[0039] The pH adjuster may include at least one of calcium carbonate, calcium bicarbonate, calcium oxide, and calcium hydroxide, which can reduce the cost of purifying groundwater.

[0040] The pH adjuster may be in a powder or granular form, which allows selection of a form suitable for the environment in which the pH adjuster is installed, thereby enabling efficient purification of groundwater while keeping costs down.

[0041] The pH adjuster may be rod-shaped. This allows the selection of a shape suitable for the environment in which the pH adjuster is to be installed, thereby reducing costs and efficiently purifying groundwater. Furthermore, by precasting the pH adjuster into a shape (e.g., rod-shaped) that fits the shape of the hole, the efficiency of the work of installing the pH adjuster can be improved.

[0042] The structure may have a plurality of holes, and the plurality of holes may include a plurality of first holes provided upstream of a groundwater flow basin and a second hole provided downstream of a groundwater flow path that flows between the plurality of first holes, thereby more effectively reducing the amount of iron ions flowing downstream.

[0043] This workpiece contains iron compounds on the surface of the pH adjusting material, which fixes the iron compounds so that they do not flow downstream.

[0044] This workpiece contains heavy metal compounds on the surface of the pH adjusting material, which can fix the heavy metal compounds so that they do not flow downstream.

[0045] The pH adjuster of one embodiment of the present disclosure is pre-molded or formed into a shape that fits into a hole in the basin of groundwater containing iron ions, and is intended to increase the pH of the groundwater. This allows for the selection of a shape that is appropriate for the environment in which the pH adjuster is to be installed, thereby reducing costs and efficiently purifying the groundwater. Furthermore, by pre-molding the pH adjuster into a shape (e.g., a rod) that fits the shape of the hole as a precast product, the efficiency of the work of installing the pH adjuster can be improved. [Explanation of symbols]

[0046] 1. Abandoned mine, 2. Abandoned mine, 3. Mine wastewater, 4. Borehole, 5. pH adjuster, 6. Iron compounds, 10. Purification equipment.

Claims

1. A pH adjuster that is pre-formed or molded into a rod shape that can fit into a borehole in a basin where groundwater containing iron ions flows, and is used to increase the pH of the groundwater.

2. Contains at least one of calcium carbonate, calcium bicarbonate, calcium oxide, and calcium hydroxide The pH adjuster according to claim 1 .

3. Contains iron compounds on the surface The pH adjuster according to claim 1 or 2.

4. Contains heavy metal compounds on the surface The pH adjuster according to any one of claims 1 to 3.

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