JP2013081907A - Method and device for desalting soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for desalting soil, which can easily remove salt content from soil without almost requiring manual operation.SOLUTION: There is provided the method for desalting soil in which a bar-like in-soil electrode 1 is buried in soil for which desalting is executed, a soil surface electrode 3 is installed on the surface of the soil for covering an area subjected to the desalting, a direct current is sent between both the electrodes, chloride ions in the soil are moved to a positive electrode side of both the electrodes and the salt content is removed from the soil having a depth required for at least crop growth.

Description

  TECHNICAL FIELD The present invention relates to a soil desalting method and a soil desalting apparatus for removing salt from a field flooded with seawater and modifying the soil.

  When seawater is inundated into a field by tsunami, storm surge, etc., especially when the field is completely submerged in seawater, even if the seawater penetrates into the ground and the seawater is pulled, Salinity also remains inside. In this case, the growth of crops is inhibited by salt damage. Therefore, when planting crops such as rice and vegetables, it is first necessary to remove salt from the fields.

  At present, for example, as a method for removing salt from rice fields, water is applied to the rice fields, the soil is stirred, the salt content is diluted, and then drained. This operation is repeated several times until the residual salinity is below a predetermined concentration. Such work is costly and time consuming and requires a large amount of manual work.

  Furthermore, in fields and the like, it is difficult to secure a large amount of water, and a method of diluting and removing salt using water cannot be performed.

In Patent Document 1, in order to prevent salt damage to concrete, an electrolyte is infiltrated into the concrete surface and an electric current is applied to attract chloride ions (Cl ⁻ ) to the + electrode provided on the concrete surface, A method for removing ions is disclosed.

  Patent Document 2 discloses a method for improving a reclaimed land, sea surface landfill, etc. to a green soil in the short term. As a soil improving material, a phosphate supply source such as lime superphosphate, gypsum, calcium sulfate. It has been proposed to remove soil by mixing rainwater and watering water, such as calcium sources such as pearlite and clay, and organic nutrients such as fallen leaves and compost.

JP 7-89773 A JP 2006-219604 A JP 2003-175383 A JP 2003-27262 A

  In view of such circumstances, the present invention provides a soil desalting method and a soil desalting apparatus that can easily remove salt from soil without requiring manual labor.

  The present invention embeds a rod-shaped soil electrode in the soil to be desalted, installs a soil surface electrode that covers the area to be desalted on the surface of the soil, energizes a direct current between both electrodes, The present invention relates to a method for desalinating soil in which chloride ions in soil are moved to the + electrode side of both electrodes, and salt is removed from the soil at a depth necessary for growing the crop at least.

  In the present invention, an electrolytic layer is formed in the desalting range of the soil surface, the soil surface electrode is a positive electrode, chloride ions are collected in the electrolytic layer, and the electrolytic layer is removed after the desalting treatment. It relates to a method of desalting soil.

  Further, the present invention provides an insulating treatment except for the tip so that the tip of the soil electrode functions as a positive electrode, and makes the depth of the tip deeper than a depth necessary for crop growth, It relates to a method for desalinating soil in which the concentration is concentrated below the depth necessary for crop growth.

  The present invention also relates to a soil desalting method in which an electroless layer having a large electrical resistance is formed around the soil electrode.

  Further, the present invention is embedded in soil for desalination, the lower end portion functions as an electrode, the lower end portion has a rod-like soil electrode deeper than the depth necessary for crop growth, and the surface of the soil. The present invention relates to a soil desalination apparatus comprising a soil surface electrode covering a range where desalting is performed, and a constant current power source for passing a direct current between both electrodes.

  The present invention also relates to a soil desalination apparatus in which an electrolytic layer is formed to cover a range where the desalting of the surface of the soil is performed, and the electrolytic layer is impregnated with an electrolytic solution in an absorbent material.

  According to the present invention, a rod-shaped soil electrode is embedded in the soil to be desalted, a soil surface electrode is installed on the surface of the soil to cover the area to be desalted, and a direct current is passed between both electrodes. In addition, it moves the chloride ions in the soil to the + electrode side of both electrodes and removes the salt from the soil at least at the depth necessary for the growth of the crop, so it is easy and requires almost manual work. It is possible to remove salt from the soil without using water.

  According to the present invention, the rod-shaped soil electrode embedded in the soil for desalination, the lower end functions as an electrode, and the position of the lower end is deeper than the depth necessary for the growth of the crop, It is equipped with a ground electrode that covers the area where surface desalting is to be performed and a constant current power source that allows direct current to flow between both electrodes. It can remove salt from soil at a deep depth, and can easily remove salt from soil without requiring manual labor and without using water. Demonstrate.

It is a schematic diagram which shows the 1st Example of this invention. It is a schematic diagram which shows the 2nd Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  After the fields are immersed in seawater due to tsunami, storm surge, etc., and the seawater is pulled, the salinity remaining in the soil exists in the form of chloride ions (-ions). In the present invention, electrodes are installed on the ground surface, electrodes are embedded in the soil, electricity is passed between both electrodes, chloride ions are attracted to the positive electrode side, and chloride ions are excluded from the range necessary for crop cultivation. To do.

  First, a first embodiment will be described with reference to FIG.

  FIG. 1 is a schematic diagram of the first embodiment, in which a ground electrode 1 having a predetermined depth is buried in the soil, an electrolytic layer 2 is formed on the soil surface, and the surface of the electrolytic layer 2 or A ground electrode 3 is laid in the electrolytic layer 2, and a DC constant current power source 4 is connected to the soil electrode 1 and the ground electrode 3. The earth electrode 1 is connected to the negative electrode of the DC constant current power source 4, and the earth electrode 3 is connected to the positive electrode of the DC constant current power source 4.

The underground electrode 1 is a metal material that does not corrode the material (that does not melt and generate metal ions), for example, a rod-shaped electrode made of titanium, and is covered with an insulating material with only the lower end portion 1a exposed. As a method of embedding, for example, it is assumed to be inserted vertically into the soil. In addition, the lower end portion 1a serving as an electrode may be titanium itself, but in a normal state, an oxide film (TiO ₂ ) is formed on the titanium surface, and the electrolysis efficiency is poor as an electrode material. It is preferable to perform gold plating or coat with ruthenium oxide.

  Furthermore, the depth of embedding the electrode 1 in the soil, that is, the depth of the lower end 1a depends on the range of soil to be desalted and the quality of the soil, but the desalting depth is about 1 m as a guideline. If it is 10 m square, the depth is preferably 5 m or more. Therefore, the soil electrode 1 is required to have a strength that can be inserted to a depth of 5 m (can withstand the pushing force), and those having a diameter of about 10 mm to 30 mm are used. The underground electrode 1 may be buried vertically or obliquely. In short, it is only necessary that the depth of the lower end 1a is deeper than the required desalting depth.

  Furthermore, the gap generated between the soil and the soil electrode 1 becomes a current flow path, and there is a possibility that the current flowing in the soil is reduced. Therefore, preferably, the electroless layer 6 is formed around the soil electrode 1 so that the electrical resistance around the soil electrode 1 is increased.

  As an example of forming the anaerobic layer 6, a substance which does not affect the growth of crops even if left in the soil, pulverized limestone, etc. are put between the soil electrode 1 and the soil, or the soil Etc.

  The earth surface electrode 3 is wide enough to cover the area to be desalted and is not corroded by chloride ions, for example, made of the above-mentioned titanium, titanium plated with titanium, or ruthenium oxide of titanium. The one coated with is used.

  The electrolytic layer 2 is obtained by impregnating an absorbent material with an electrolytic solution. Examples of the absorbent material include those obtained by granulating sodium polyacrylate, and the thickness is preferably about several cm to 10 cm. . Further, after the desalting treatment, the electrolytic layer 2 can be removed alone. Further, as the electrolytic solution, one that does not adversely affect the soil after the desalting treatment is used, and the components of the soil improver as described in Patent Document 2 or Patent Document 3 and Patent Document 4 are described. And the like that specifically adsorb anions such as chloride ions.

The DC constant current power source 4 supplies a current necessary for desalting. The current density required for desalting is about 1 A / m ² . The optimum current density for desalting varies depending on the soil quality and the like, and the optimum current density is determined by the soil to be desalted.

The current density required for desalination as 1A / m ^2, a 10m square ie 100 m ² per 100A. Further, since the voltage when a constant current of 1 A / m ² is supplied is several V at most, assuming a 100 V commercial power supply, the voltage is several A, which is a capacity that can be sufficiently covered by the commercial power supply. Furthermore, if it is used in combination with a power source such as a solar battery, it becomes possible to supply power for desalination more rationally.

  When a constant current is passed between the earth electrode 1 and the earth electrode 3, the earth electrode 1 and earth electrode 3 are insoluble electrodes (those that the electrode melts and does not generate metal ions) There is no supply of cations from the electrode side, and chloride ions, which are anions in the soil, move to the soil surface electrode 3 side and are collected by the electrolytic layer 2.

  In this embodiment, the electrolysis is performed under conditions that move to the vicinity of the electrodes, and the conditions are such that no electrolytic reaction occurs. Therefore, chlorine gas (toxic) is not generated, and chloride ions are collected and concentrated in the electrolytic layer 2. By conducting energization (electrolysis) for a required period, removing and discarding the electrolytic layer 2, chloride ions can be completely removed from the soil without omission. Further, since the electrolytic layer 2 is made of an absorbent material, it is easy to handle.

During electrolysis, not only chloride ions are attracted, but other anions (OH ⁻ ) are also attracted, but since no ions are supplied from the electrodes, the following changes do not occur.
4OH ⁻ → 2H ₂ O + O ₂ ↑ + 4e ⁻

Similarly, it does not lead to O ₂ . Accordingly, OH ⁻ is concentrated and the environment is alkalized.

In addition, when the electrolysis is terminated and left in a state where chloride ions or OH ⁻ is concentrated, a cation such as Na ⁺ or K is used to maintain electrical neutrality without any external electrolysis. ⁺ Etc. move.

  Therefore, before carrying out desalting, the neutralizing agent when NaOH and KOH are produced is mixed in the soil and stirred. Examples of the neutralizing agent include lime superphosphate and calcium sulfate.

  In addition, since the neutralizing agent is mixed in the soil in advance, the soil can be homogenized by mixing and stirring the soil to the required depth with a tiller or the like. For this reason, since the path | route where the electric current flows easily specifically is destroyed, the effect that desalting electrolysis is performed uniformly can also be expected.

  Next, in FIG. 1, a curve A indicates a salinity concentration remaining in the soil after seawater is immersed. The position of the underground electrode 1 (that is, the position of the lower end 1a) is set to be further below the lowest position impregnated with seawater.

  By energizing between the earth electrode 1 and the earth electrode 3, chloride ions in the earth are attracted and moved to the earth electrode 3 side, which is a positive electrode, and collected in the electrolytic layer 2. Then, the electrolytic layer 2 is migrated. The salt concentration in a state where electricity is passed through the soil and chloride ions are collected in the electrolytic layer 2 is shown by a curve B.

  In the case of desalting according to the present embodiment, the salinity concentration in the soil does not have to be 0, and it may be removed to the extent that does not hinder the growth of the crop. Also, the salinity that does not hinder the growth of crops varies depending on the crop. For example, in the case of paddy fields, if it exceeds 0.4%, it will hinder rice growth, and even about 0.1% is said to have an effect. Yes.

  After carrying out desalting for a predetermined period, when the salt concentration in the soil reaches a predetermined value, the electrolytic layer 2 is removed, and the soil electrode 1 and the soil surface electrode 3 are further removed.

  FIG. 2 shows a second embodiment.

  In the second embodiment, the earth electrode 1 is connected to the + electrode of the DC constant current power source 4, and the earth surface electrode 3 is connected to the − electrode of the DC constant current power source 4. In the second embodiment, the construction of the soil electrode 1 and the soil surface electrode 3 is the same as that of the first embodiment, and the description thereof will be omitted.

  In the second embodiment, since the soil electrode 1 is a positive electrode, chloride ions migrating into the soil are attracted to the lower end 1 a of the soil electrode 1. Accordingly, the salinity increases as the depth increases in the soil. In FIG. 2, curve A shows the salinity concentration remaining in the soil after the seawater is immersed, and curve B shows the salinity concentration after the desalting treatment in this example.

  It suffices if the depth D of the soil necessary for the crop to grow is less than or equal to a predetermined salinity, and the depth of the lower end portion 1a in the soil is less than a predetermined salinity at the depth D. Set to

  In the case of the second embodiment, the electrolytic layer 2 can be omitted.

DESCRIPTION OF SYMBOLS 1 Underground electrode 1a Lower end part 2 Electrolytic layer 3 Earth surface electrode 4 DC constant current power supply 6 Negative current layer

Claims (6)

  A rod-shaped soil electrode is embedded in the soil to be desalted, and a soil surface electrode is installed on the surface of the soil to cover the area where desalting is to be performed. A method for desalinating soil, characterized in that salt ions are removed from the soil at a depth necessary for growing a crop at least by moving object ions to the + electrode side of both electrodes.   The electrolytic layer is formed in the desalting range of the surface of the soil, the soil surface electrode is used as a positive electrode, chloride ions are collected in the electrolytic layer, and the electrolytic layer is removed after the desalting treatment. Soil desalination method.   The tip of the soil electrode is insulated so that the tip functions as a positive electrode, and the depth of the tip is made deeper than the depth necessary for growing the crop, and the salinity is increased. The soil desalination method according to claim 1, wherein the soil is concentrated below a depth required for the soil.   The soil desalination method according to any one of claims 1 to 3, wherein an electroless layer having a large electrical resistance is formed around the soil electrode.   Desalting the surface of the soil and the rod-shaped soil electrode that is buried in the soil where desalination is performed, the lower end functions as an electrode, and the position of the lower end is deeper than the depth required for crop growth A soil desalination apparatus comprising a soil surface electrode covering a range and a constant current power source for passing a direct current between both electrodes.   The soil desalination apparatus according to claim 5, wherein an electrolytic layer is formed to cover a range where the desalting of the surface of the soil is performed, and the electrolytic layer is formed by impregnating an absorbent with an electrolytic solution.

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