Soil modifier

Abstract

To provide a soil modifier that uses an alternative substance instead of an anionic polymeric coagulant as a modification auxiliary combined with a water-absorbing polymer, to reduce environmental load, while providing modification effects that are not inferior to conventional products.SOLUTION: A soil modifier contains a water-absorbing polymer, a modification auxiliary, a solidifying agent, and a dispersant. The soil modifier uses thickening polysaccharides instead of anionic polymeric coagulants, thereby reducing environmental impact while offering modification effects that are not inferior to conventional products.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a soil conditioner for treating soft soil that is mainly moist. [Background technology]

[0002] For soil that contains a lot of moisture, such as sedimentary soil caused by tsunami or storm surge damage, construction sludge, and soft soil, sieves can be used to remove waste such as plants, stones, and debris contained in the soil for reuse, or the soil can be modified to have finer particles that are easier to handle so that it can be transported and removed smoothly using heavy machinery.Soft soil can also be modified by solidifying and strengthening it so that it can be used for other purposes such as residential areas or parks.If soft soil contains hazardous substances, it can be insolubilized to prevent the hazardous substances from leaching from the soil.

[0003] In response to this, soil conditioners containing a flocculant, a modification aid, a solidifying agent, and a dispersant are used as treatment agents for converting turbid water, high-water content sludge, etc. into loose soil that is easy to handle. For example, the soil conditioner described in Patent Document 1, which uses a water-absorbent polymer as the flocculant and an anionic polymer flocculant as the modification aid, is known.

[0004] In addition, a soil improvement solidification agent described in Patent Document 2 is known which is used for highly water-rich soil by adding and mixing a cement-based solidification agent, a pH adjuster, a flocculant, and a water-absorbency enhancer to strengthen and improve soft soil to make it suitable for the intended use.

[0005] Furthermore, a conventional insolubilization method is disclosed in Patent Document 3, which uses a treatment agent containing magnesium oxide as the main component to insolubilize harmful substances in contaminated soil that is generated in mountainous areas and urban areas, thereby preventing the harmful substances from leaching out of the contaminated soil. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-6614 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-363560 [Patent Document 3] Patent Publication No. 2021-011574 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the above Patent Documents 1 to 3, it is possible to modify highly water-containing soil to make it easier to handle, to strengthen weak ground, and to prevent harmful metals from leaching out of the soil. However, because the soil modifiers contain many petroleum-derived components, there is a problem in that the environmental load on the soil being treated is high.

[0008] The object of the present invention is to provide a soil conditioner that has a lower environmental impact than when an anionic polymer flocculant is used as a modification aid in combination with a water-absorbing polymer, and that can exhibit various modification performances equal to or greater than those of the case where an anionic polymer flocculant is used as a modification aid in combination with a water-absorbing polymer. [Means for solving the problem]

[0009] As a result of intensive research to solve the above problems, the present inventors have discovered that in a soil conditioner containing a water-absorbent polymer, a modification aid, a solidifying agent, and a dispersant, adding a thickening polysaccharide instead of an anionic polymer flocculant can achieve the same modification performance with a lower environmental impact, and have completed the present invention. The present invention is as follows.

[0010] [1] A soil conditioner comprising a water-absorbing polymer and a soil conditioner auxiliary, wherein the soil conditioner auxiliary is a thickening polysaccharide. [2] A soil conditioner characterized in that tapioca flour is used as the thickening polysaccharide. [3] The thickening polysaccharide is contained in an amount of 0.6 to 3%. [4] The water-absorbing polymer is contained in an amount of 0.1% or more. [5] A soil conditioner characterized by using magnesium oxide as the solidifying agent. [6] A soil conditioner characterized by the addition of a pH adjuster. [7] A soil conditioner characterized by using calcium carbonate or zeolite as a dispersant. [Effects of the Invention]

[0011] According to the present invention configured as described above, by using a thickening polysaccharide instead of an anionic polymer flocculant as a modification aid to be combined with a water-absorbent polymer, it is possible to fully exert the effect of modifying wet soil while reducing the environmental load. [Brief explanation of the drawings]

[0012] [Figure 1] This is a table showing the results of an experiment comparing the modification performance of the comparative modifier with soil modifiers 1 and 2. [Figure 2] This is a table comparing the experimental results when the comparative modifier and soil modifier 1 were used on sample soils with moisture contents of 42%, 45%, 48%, and 52%. [Figure 3] FIG. 1 is a table showing the relationship between the amount of soil modifier added and the amount of arsenic elution. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described. Note that % in this specification is based on mass unless otherwise specified.

[0014] The soil conditioner according to an embodiment of the present invention contains a water-absorbing polymer, a thickening polysaccharide that is also used as a soil conditioner aid, a solidifying agent, a pH adjuster, and a dispersant, and is in a powder form that is easy to carry around.

[0015] The soil conditioner described above effectively absorbs moisture in the soil by combining a water-absorbing polymer that absorbs and swells with a modifier adjuvant with a flocculating effect, thereby modifying wet soil into a loose (crumbly) granular form. Furthermore, by incorporating a thickening polysaccharide as the modifier adjuvant instead of an anionic polymer flocculant made from petroleum-derived components, soil modification effects equivalent to or greater than those achieved when using an anionic polymer flocculant can be achieved while significantly reducing the burden on the environment. The specific configuration of the soil conditioner of the present invention is described below.

[0016] (water-absorbent polymer) A water-absorbent polymer (SAP) is a polymeric resin that absorbs water and swells when it comes into contact with water. Examples of water-absorbent polymers include starch-based, cellulose-based, polyvinyl alcohol-based, and acrylic-based resins.

[0017] In addition, the water-absorbing polymer exhibits a soil improvement effect if it is contained in an amount of 0.1% or more of the total soil conditioner, and the improvement effect increases as the content of the water-absorbing polymer increases. Specifically, the water-absorbing polymer is preferably about 1 to 6% of the total soil conditioner.

[0018] (Thickening polysaccharides) Naturally derived thickening polysaccharides were used as the modifying aids to be combined with the water-absorbent polymer instead of conventional anionic polymer flocculants. Thickening polysaccharides include mixtures of multiple polysaccharides, such as guar gum, locust bean gum, tara gum, xanthan gum, alginic acid, carrageenan, tamarind gum, glucomannan, cationized starch, cationized guar gum, quince seed, agar, methylcellulose, carboxymethylcellulose, tapioca starch, and soybean polysaccharides, as well as salts or derivatives thereof, as well as by-products containing thickening polysaccharides generated during the manufacturing process, such as flying powder. Furthermore, the above thickening polysaccharides may be used alone or in combination as a modifying aid. In this invention, tapioca powder processed into a powder was particularly used.

[0019] The content of the thickening polysaccharide is preferably about 0.6 to 3.0%, and particularly preferably about 0.8 to 1.6%, of the total soil conditioner.

[0020] (Solidifying agent) The solidification agent is a solidification / insolubilization agent containing either or both of a magnesium component and a calcium component as the main component, and can solidify the soil to be treated and insolubilize harmful substances contained in the soil. Specifically, magnesium oxide, calcium oxide, etc. are used.

[0021] The amount of solidifying agent to be added is determined by the soil quality (type) and moisture content of the wet soil, and the intended use of the improved treated soil (specifically, whether to transport and process it, sift through etc. to remove impurities, increase the strength of soft ground, or insolubilize harmful metals in the soil). In other words, while the soil can be improved without adding a solidifying agent, the amount to be added is adjusted depending on the intended use of the treated soil that has been improved and turned into granules. Depending on the intended use, it may be included so that it constitutes more than 50% of the total soil improver.

[0022] (pH adjuster) The pH adjuster may be any agent capable of adjusting the pH of the soil conditioner, which becomes alkaline due to the solidification agent. Specifically, examples of the pH adjuster include organic acids and derivatives thereof, such as citric acid, malic acid, adipic acid, fumaric acid, maleic acid, succinic acid, and tartaric acid; sulfates such as ammonium sulfate, ferrous sulfate, aluminum sulfate, lithium sulfate, magnesium sulfate, and potassium sulfate; phosphates such as ammonium phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, and potassium dihydrogen phosphate; chloride salts such as ammonium chloride; carbonates and hydrogen carbonates such as sodium carbonate, potassium carbonate, dolomite, sodium bicarbonate, and potassium bicarbonate; hydroxides such as magnesium hydroxide; metal oxides such as amylna; and acid clays such as acid clay and activated clay.

[0023] The pH of the soil conditioner can be adjusted as desired by increasing the content of pH adjuster relative to the solidification agent if the pH of the soil conditioner is to be acidic, or by reducing (not adding) the content of pH adjuster relative to the solidification agent if the pH of the soil conditioner is to be alkaline. Soil conditioners are usually neutral, but if the soil to which they are added is acidic or alkaline, the pH of the soil conditioner can be adjusted in advance to neutral or close to neutral after the amendment.

[0024] (dispersant) The dispersant is primarily an inorganic powder, which facilitates the distribution of the water-absorbent polymer and the modification aid throughout the soil to be treated, thereby improving the efficiency of moisture removal from the soil and reducing the amount of soil modifier used. Examples of dispersants that can be used in this invention include, but are not limited to, powdered calcium carbonate, zeolite, gypsum, coal ash, diatomaceous earth, volcanic ash, and paper sludge. Among these, calcium carbonate and zeolite powders are more preferred, as they prevent the modified soil from clumping. The dispersant may be used alone or in combination of two or more.

[0025] The powdered soil conditioner according to the present embodiment described above can be produced by mixing a water-absorbent polymer, a thickening polysaccharide, a solidifying agent, a pH adjuster, and a dispersant in a mixer, etc. Incidentally, in order to achieve the effect of modifying wet soil into a loose granular form, it is sufficient to contain at least a water-absorbent polymer and a thickening polysaccharide to achieve a certain degree of effect, but in order to strengthen and modify soft soil or to insolubilize harmful substances contained in the soil, it is necessary to also contain a solidifying agent.

[0026] (Soil improvement method) The soil modification method using the soil modifier of the present invention includes an addition step of adding the above-mentioned soil modifier to the moist soil to be treated, and an agitation step of agitating the soil so that the soil modifier is uniformly contained within the soil, thereby enabling the moist soil to be modified into a loose (granular) state. [Example]

[0027] The present invention will be specifically described below using experimental examples. However, the present invention is not limited to these examples. First, an experimental example relating to a soil conditioner using tapioca flour processed as a modification adjuvant (thickening polysaccharide) will be described.

[0028] (Experimental example) First, yellow soil and clay were mixed in a 4:1 ratio, and water was added until the moisture content reached 42% to create a sample soil. The soil conditioners 1 to 4 and the comparative conditioner were added to the sample soil and stirred, and the modification effects of the sample soil (moisture-containing soil) were compared for each conditioner. The amounts of soil conditioner added to the sample soil were adjusted to 0.04g, 0.08g, and 0.16g per 100g of sample soil, and the results were compared.

[0029] It was confirmed whether the soil could be improved by adding and mixing anionic polymers, processed tapioca flour, or processed potato flour to the above sample soil.

[0030] Figure 1 is a table comparing the soil improvement effects when anionic polymers, processed tapioca flour, or processed potato flour were added to sample soil. As shown in the experimental results in Figure 1, both tapioca flour and potato flour were confirmed to have some degree of soil improvement effect. Among these, tapioca flour was found to have a higher improvement effect than potato flour, and was confirmed to have an improvement effect equivalent to that of anionic polymer flocculants.

[0031] Furthermore, when an anionic polymer flocculant was added to the sample soil, the sample soil became somewhat viscous, whereas when tapioca flour was added, the sample soil exhibited almost no viscosity. In other words, by using tapioca flour instead of an anionic polymer flocculant as a modification aid, the treated soil after modifying the wet soil became less viscous and more flaky. This improves the handleability of the treated soil, making it easier to transport the treated soil and to remove foreign matter using sieves, etc.

[0032] (Experimental Example 2) First, a comparative modifier consisting of 6% water-absorbent polymer (sodium polyacrylate), 0.8% anionic polymer flocculant, and 83.2% dispersant (calcium carbonate) was prepared, and a soil modifier of the present invention consisting of 6% water-absorbent polymer (sodium polyacrylate), 1.6% thickening polysaccharide (processed tapioca flour), and 82.4% dispersant (calcium carbonate) was prepared.

[0033] The moisture content of the sample soil was increased stepwise to 42%, 45%, 48%, and 52%, and the soil amendment performance of the soil amendment described above and a comparative amendment was compared at each moisture content. The amount and concentration of the soil amendment added were adjusted based on the results of Experiment 1, so that the amount of amendment supplement added was 0.024g or 0.048g per 100g of sample soil, and the comparison was made. Incidentally, the sample soil with a moisture content of 48% was just beginning to float to the surface of the soil, while the sample soil with a moisture content of 52% was in a muddy state.

[0034] Figure 2 is a table comparing the experimental results when the comparative modifier and the soil modifier were used on sample soils with moisture contents of 42%, 45%, 48%, and 52%. As shown in the experimental results in Figure 2, it was confirmed that the soil modifier of the present application exhibited the same modification performance as the comparative modifier when the moisture contents of the sample soils were 42%, 45%, and 48%. Furthermore, no moisture regurgitation phenomenon was observed in any of the treated soils within 24 hours after treatment.

[0035] (Experimental Example 3) First, a soil conditioner of the present invention was prepared, consisting of 4.4% water-absorbent polymer (sodium polyacrylate), 0.6% thickening polysaccharide (processed tapioca flour), 13.3% solidifying agent (magnesium oxide), 5.4% pH adjuster (ferrous sulfate), and 76.3% dispersant (calcium carbonate).

[0036] Next, the sample soil was enriched with trace amounts of arsenic as a harmful substance, and the amount of arsenic leaching from the sample soil was examined by adding a soil conditioner.

[0037] Figure 3 is a table showing the relationship between the amount of soil modifier added and the amount of arsenic eluted. As shown in the figure, it was confirmed that by treating soil containing harmful substances with the soil modifier of the present invention, the harmful substances in the soil can be insolubilized.

[0038] In addition, the soil strength was measured for treated soil that had been amended with soil conditioners. The cone index immediately after amendment was 500 kN / m 2 After curing for about 7 days, the strength is 1300kN / m 2 In other words, it was confirmed that soil conditioners containing solidifying agents can also be used to strengthen and improve soft ground and soil.

Claims

1. A soil conditioner comprising a water-absorbing polymer and a soil conditioner adjuvant, The modifying aid is a thickening polysaccharide. Soil conditioner.

2. The thickening polysaccharide is characterized in that tapioca flour is used. The soil conditioner according to claim 1.

3. Contains 0.6 to 3% of the thickening polysaccharide The soil conditioner according to claim 1.

4. The water-absorbing polymer is contained in an amount of 0.1% or more. The soil conditioner according to claim 1.

5. Contains magnesium oxide as a solidifying agent The soil conditioner according to claim 1.

6. pH adjuster added The soil conditioner according to claim 1.

7. Calcium carbonate or zeolite was used as a dispersant. The soil conditioner according to claim 1.

Images