Soil cleaning method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KAO CORP
- Filing Date
- 2023-08-25
- Publication Date
- 2026-07-02
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for washing soil. [Background technology]
[0002] In recent years, there have been many cases of serious soil contamination in a variety of situations, including illegal dumping of industrial waste, waste disposal in factories, and accidental leakage of hazardous substances from final disposal sites, as well as accidental or long-term leakage of various oils at the sites or former sites of petroleum refineries, gas stations, chemical plants, etc.
[0003] Conventionally, methods for remediating such contaminated soil have included incineration after excavation, solidification / fixation, containment, bioremediation, soil washing, and other techniques, but among these, technologies that remove contaminants from the soil and purify it are becoming mainstream.
[0004] Compared to other methods, the soil washing method is highly versatile because it can purify different types of contaminants (oil, heavy metals), can be used as a pretreatment process for bioremediation, etc., can treat a large amount of contaminated soil, and has the potential to reduce the overall cost of purification. Usually, soil washing uses a cleaning agent that contains a surfactant.
[0005] Patent Document 1 discloses a method for treating soil contaminated with a pollutant selected from the group consisting of petroleum products and aromatic hydrocarbons, the method comprising a step of contacting the soil with an aqueous solution combining hydrogen peroxide and a hydroxide source. Furthermore, Patent Document 2 discloses a method for separating and removing oil from soil contaminated with a high concentration of oil, which comprises a step of subjecting a slurry in which the soil contaminated with a high concentration of oil is dispersed in water to a first flotation treatment under specified conditions to separate the oil, and then classifying fine particles in the soil, and then subjecting the soil to a second flotation treatment under specified conditions to further separate the oil. Furthermore, Patent Document 3 discloses an in-situ purification method for oil-contaminated soil, which includes an injection step of injecting washing water containing a surfactant into the oil-contaminated soil, a standing step of leaving the washing water to stand for a sufficient period of time to allow it to permeate into the oil-contaminated soil, and a recovery step of pumping and recovering the oil that has been peeled off from the oil-contaminated soil together with the washing water after the standing step. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] Special Publication No. 2017-518868 [Patent Document 2] JP 2007-98316 A [Patent Document 3] JP 2023-30770 A Summary of the Invention [Problem to be solved by the invention]
[0007] There are two methods for remediating oil-contaminated soil: bioremediation and flotation. However, bioremediation takes time because microorganisms decompose oil slowly. In addition, although flotation can separate oil from soil, it is difficult to remove all the oil adhering to fine particles, and waste is always generated after classification. In contrast, soil washing using a washing solution involves contacting oil-contaminated soil with a washing solution, and the soil is washed by separating the oil from the soil through the action of the washing solution, so theoretically the work period is short and classification is not required. However, there have been few cases in which the method of washing soil with a washing solution has actually been implemented due to reasons such as low cleaning power and difficulty in wastewater treatment after washing. Therefore, it is desirable to wash soil using a simpler method that has excellent cleaning power for oil-contaminated soil. The present invention provides a soil washing method that has excellent cleaning power for oil-contaminated soil and washes the soil using a simple application method. [Means for solving the problem]
[0008] The present invention relates to a soil washing method which comprises obtaining a slurry having a pH of 9 to 13, containing oil-contaminated soil and (A) a surfactant and water, and allowing the soil in the slurry to settle. Effect of the Invention
[0009] According to the present invention, there is provided a soil washing method which has excellent cleaning power for oil-contaminated soil and can wash soil using a simple construction method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The mechanism by which the soil washing method of the present invention has excellent washing power for oil-contaminated soil and can wash soil with a simple application method is unclear, but is thought to be as follows. By adjusting the pH of the slurry containing oil-contaminated soil, surfactant, and water to 9-13, the interaction between the soil surface and the oil is weakened, promoting the lifting of the oil stains from the soil. Furthermore, the presence of an appropriate surfactant in the water is thought to promote the separation of the oil and water that have been separated from the soil without emulsifying them. This allows the oil adhering to the soil to be efficiently separated from the soil and water, and is thought to simplify not only the soil washing process but also the post-treatment process of the water used to wash the soil. As a result, the soil washing method of the present invention not only improves the washing power in washing soil contaminated with oil, but also brings about the unexpected effect of making the washing operation easy to carry out. However, the soil washing method of the present invention is not limited to this mechanism.
[0011] <Soil washing method> The soil washing method of the present invention involves obtaining a slurry (hereinafter also referred to as the slurry of the present invention) containing oil-contaminated soil, a surfactant (A) (hereinafter referred to as component (A)), and water, and allowing the soil in the slurry to settle. The slurry may be a suspension containing oil-contaminated soil, component (A), and water, and having a pH of 9 to 13. Allowing the soil in the slurry to settle may involve leaving the slurry to stand and allowing the soil in the slurry to settle, or may involve leaving the slurry to stand and causing oil adhering to the soil in the slurry to float to the surface and allowing the soil to settle. In addition, the soil washing method of the present invention may be a soil washing method including step 1 of preparing a slurry containing oil-contaminated soil, (A) a surfactant, and water and having a pH of 9 to 13 (hereinafter referred to as step 1), and step 2 of settling the soil in the slurry (hereinafter referred to as step 2).
[0012] <Soil contaminated by oil> The soil washing method of the present invention may be a method for washing soil contaminated with oil or further with petroleum-based compounds. That is, the present invention may be a soil washing method for washing oily stains such as petroleum-based compounds in soil. The oil may be, for example, one or more oils selected from animal oils, vegetable oils, and chemically synthesized oils. Examples of the petroleum-based compounds include petroleum-based hydrocarbons. The petroleum-based compounds may be, for example, gasoline, kerosene, light oil, heavy oil, machine oil, etc. The petroleum-based compounds may also include aromatic compounds such as benzene and toluene.
[0013] In the soil washing method of the present invention, the soil is not particularly limited, but examples include one or more types selected from coarse-grained soils such as gravelly soil and sandy soil, and fine-grained soils such as clayey soil, organic soil, and volcanic ash clayey soil. From the viewpoint of realizing the effects of the present invention, the soil preferably contains particles having a particle size of 150 μm or less in an amount of preferably 2 mass % or more, more preferably 5 mass % or more, even more preferably 8 mass % or more, and even more preferably 10 mass % or more, and from the viewpoint of the settling property of the slurry, the soil preferably contains 60 mass % or less, more preferably 50 mass % or less, and even more preferably 30 mass % or less. The particle size distribution of soil is a value measured by the soil particle size test specified in JIS A 1204.
[0014] <Component (A)> Component (A) is a surfactant, and may be at least one selected from the group consisting of (A1) a nonionic surfactant (hereinafter referred to as component (A1)), (A2) anionic surfactant (hereinafter referred to as component (A2)), and (A3) amphoteric surfactant (hereinafter referred to as component (A3)). From the viewpoints of improving the cleaning properties and the oil-water separability, the component (A) is preferably one or more surfactants containing the component (A1), and the component (A1) is more preferable.
[0015] <Component (A1)> The component (A1) is a nonionic surfactant. The component (A1) is a component that is preferably used from the viewpoint of improving the cleaning property and the separation property between oil and water. Examples of the nonionic surfactant include polyoxyalkylene alkyl or alkenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, fatty acid monoglyceride, polyethylene glycol fatty acid ester, etc. These can be used alone or in combination of two or more kinds.
[0016] From the viewpoints of improving the cleaning properties and the oil-water separation properties, the component (A1) is preferably a polyoxyalkylene alkyl or alkenyl ether, more preferably a polyoxyalkylene alkyl ether. The oxyalkylene group of the polyoxyalkylene alkyl or alkenyl ether is preferably one or more selected from those having from 2 to 18 carbon atoms, more preferably an oxyethylene group. The component (A1) is preferably a polyoxyalkylene alkyl or alkenyl ether in which the carbon number of the alkyl or alkenyl group is preferably 10 or more and preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less, the oxyalkylene group is one or more selected from oxyalkylene groups having from 2 to 18 carbon atoms, preferably an oxyethylene group, and the average number of moles of the oxyalkylene group added is preferably 3 or more, more preferably 4 or more, and preferably 10 or less. When the oxyalkylene group of the polyoxyalkylene alkyl or alkenyl ether contains a plurality of different oxyalkylene groups, the different oxyalkylene groups may be randomly bonded or block-bonded.
[0017] From the viewpoint of improving cleaning properties, the component (A1) is preferably a polyoxyethylene alkyl or alkenyl ether in which the carbon number of the alkyl or alkenyl group is preferably from 10 to 18, and the average number of moles of oxyethylene groups added is preferably 3 or more, more preferably 4 or more, and preferably 10 or less [hereinafter referred to as component (A1-1)]. The alkyl or alkenyl group of the component (A1-1) may be either straight-chain or branched-chain; from the standpoint of improving cleaning properties, straight-chain groups are preferred. The number of carbon atoms in the alkyl or alkenyl group of the component (A1-1) is preferably 10 or more and preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less. From the viewpoint of improving cleaning properties, the number of carbon atoms in the alkyl or alkenyl group of the component (A1-1) is even more preferably 10 or 12. The average number of moles of oxyethylene groups added in the component (A1-1) is preferably 3 or more, more preferably 4 or more, from the viewpoint of improving detergency, and is preferably 10 or less from the viewpoint of oil-water separability. The component (A1-1) is preferably one having an alkyl group, that is, a polyoxyethylene alkyl ether from the viewpoint of improving detergency and oil / water separability.
[0018] <(A2) component> The component (A2) is an anionic surfactant. The component (A2) can be used alone or in combination of two or more. The component (A2) can be an anionic surfactant having a molecular weight of 200 or more and 1000 or less. From the viewpoint of improving cleaning properties, the molecular weight of the (A2) component is preferably 200 or more, more preferably 250 or more, and preferably 1000 or less, more preferably 600 or less.
[0019] From the viewpoint of improving cleaning properties, examples of the component (A2) include anionic surfactants having a molecular weight of 200 or more and 1,000 or less, selected from fatty acid salts, sulfate salts, sulfonates, and phosphate salts.
[0020] From the viewpoint of improving the cleaning property, the number of carbon atoms of the fatty acid in the fatty acid salt is preferably 10 to 18. Specific examples of the fatty acid salt include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and salts thereof, such as alkali metal salts and organic amine salts. The fatty acid may be a mixed fatty acid.
[0021] From the viewpoint of improving cleaning properties, examples of the sulfate ester salt include sulfate ester salts having an alkyl or alkenyl group having 10 to 20 carbon atoms. Specific examples of the sulfate ester salt include sulfate ester salts (AS) having an alkyl or alkenyl group having 10 to 20 carbon atoms, polyoxyalkylene alkyl or alkenyl ether sulfate ester salts (AES) (for example, alkyl or alkenyl ether sulfate ester salts having an average added mole number of oxyalkylene groups having 2 to 4 carbon atoms of 0.5 moles to 10 moles and having a linear or branched alkyl or alkenyl group having 10 to 20 carbon atoms), polyoxyalkylene alkyl or alkenyl phenyl ether sulfate ester salts having a linear or branched alkyl or alkenyl group having 10 to 20 carbon atoms, and castor oil sulfate ester salts.
[0022] Specific examples of the sulfonate, from the viewpoint of improving cleaning properties, include alkanesulfonates (SAS) having from 10 to 20 carbon atoms, linear or branched alkylbenzenesulfonates (LAS or ABS) having an alkyl group having from 8 to 18 carbon atoms, α-olefinsulfonates (AOS) having from 10 to 20 carbon atoms, di- or monoalkylsulfosuccinates (e.g., sodium di(2-ethylhexyl)sulfosuccinate (AOT)), saturated or unsaturated α-sulfofatty acids having from 8 to 20 carbon atoms or methyl, ethyl or propyl ester salts thereof.
[0023] The phosphate ester salt may be a salt of a phosphate ester having an alkyl or alkenyl group having 10 to 20 carbon atoms from the viewpoint of improving cleaning properties. Specific examples of the phosphate ester salt include polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether phosphate, and long-chain alkyl phosphate. As the phosphate salt, for example, any slurry of a monoester, a diester, or a mono- and di-ester (sesquiester) may be used.
[0024] From the viewpoint of cost, the component (A2) is preferably one or more anionic surfactants selected from sulfate ester salts (AS), polyoxyalkylene alkyl or alkenyl ether sulfate salts (AES), and alkylbenzene sulfonates (LAS). From the viewpoint of improving cleaning properties, the component (A2) is more preferably one or more anionic surfactants selected from sulfate ester salts (AS) and polyoxyalkylene alkyl or alkenyl ether sulfate salts (AES).
[0025] From the viewpoints of improving cleaning properties and costs, the component (A2) is preferably an anionic surfactant having a molecular weight of 200 or more and 1,000 or less selected from alkyl sulfate salts, polyoxyethylene alkyl ether sulfate salts, and alkylbenzene sulfonates, and more preferably an anionic surfactant having a molecular weight of 200 or more and 1,000 or less selected from alkyl sulfate salts and polyoxyethylene alkyl ether sulfate salts.
[0026] From the viewpoint of improving cleaning properties, the alkyl sulfate is preferably an alkyl sulfate having an alkyl group having 10 or more and 18 or less carbon atoms. From the viewpoint of improving cleaning properties, the polyoxyethylene alkyl ether sulfate is preferably a polyoxyethylene alkyl ether sulfate having an alkyl group with 10 or more and 18 or less carbon atoms and an average added mole number of oxyethylene groups of 0.5 or more and 5.0 or less. From the viewpoint of improving cleaning properties, the alkylbenzenesulfonate is preferably an alkylbenzenesulfonate having an alkyl group with 10 or more and 14 or less carbon atoms.
[0027] Examples of the salt of the anionic surfactant of component (A2) include alkali metal salts, alkaline earth metal salts, amine salts, ammonium salts, alkanolamine salts, etc. From the viewpoint of solubility, this salt is preferably a salt selected from alkali metal salts and alkanolamine salts, and more preferably a sodium salt or alkanolamine salt.
[0028] The component (A3) is an amphoteric surfactant, and examples of the component (A3) include one or more amphoteric surfactants selected from amino acid types, betaine types, and amine oxides.
[0029] The (A) component preferably contains at least the (A1) component. When the (A) component contains the (A1) component, the ratio of the content of the (A1) component to the content of the total surfactants in the slurry of the present invention [(A1) / (total surfactants)] is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and preferably 100% by mass or less, and may be 100% by mass. The content of the total surfactants in the slurry of the present invention may be the total content of the (A1) component, the (A2) component, and the (A3) component in the slurry.
[0030] <Composition, etc.> The slurry of the present invention contains the component (A) in an amount of preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more from the viewpoint of washability, and in an amount of preferably 4 mass % or less, more preferably 2 mass % or less, even more preferably 1.5 mass % or less, and even more preferably 0.5 mass % or less from the viewpoint of wastewater treatability.
[0031] In the soil washing method of the present invention, the slurry of the present invention is obtained by mixing the soil and the component (A) so that the component (A) in the slurry is preferably 0.05 mass % or more, more preferably 0.3 mass % or more, and even more preferably 1 mass % or more, relative to the soil contained in the slurry, from the viewpoint of improving washability, and is preferably 8 mass % or less, more preferably 5 mass % or less, and even more preferably 3 mass % or less, from the viewpoint of wastewater treatability.
[0032] The slurry of the present invention contains water. Examples of water include tap water, river water, lake water, and groundwater. In the soil washing method of the present invention, the soil and water are mixed so that the water content of the soil in the slurry is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 100% by mass or more from the viewpoint of improving washability and ease of application, and is preferably 200% by mass or less, more preferably 150% by mass or less, and even more preferably 130% by mass or less from the viewpoint of reducing the amount of wastewater, to obtain the slurry of the present invention.
[0033] The slurry of the present invention contains water in an amount of preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more from the viewpoint of improving cleanability and ease of application, and preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less from the viewpoint of reducing the amount of wastewater.
[0034] The pH of the slurry of the present invention is 9 or more, preferably 9.5 or more, more preferably 10 or more, from the viewpoint of weakening the interaction between the soil surface and oil and enhancing washability, and is 13 or less, preferably 12 or less, more preferably 11.5 or less, from the viewpoint of wastewater treatability. The pH of the slurry of the present invention is preferably within the above range at the temperature when washing the soil [hereinafter referred to as the washing temperature]. If the pH at 25°C is within the above range, it can be said that the pH at the washing temperature also maintains the above range. The temperature when washing the soil may be the temperature after preparing the slurry.
[0035] <pH measurement method> Specifically, the pH of the slurry of the present invention at 25°C can be measured by the following pH measurement method. Connect a combined electrode for pH measurement (for example, made by Horiba, Ltd., glass sliding sleeve type) with the internal solution of the pH electrode being a saturated potassium chloride aqueous solution (3.33 mol / L) to a pH meter (for example, pH / Ion Meter F-23 made by Horiba, Ltd.). Next, fill 100 mL beakers with pH 4.01 standard solution (phthalate standard solution), pH 6.86 (neutral phosphate standard solution), and pH 9.18 standard solution (borate standard solution) respectively, and immerse them in a constant temperature bath at 25°C for 30 minutes. Immerse the pH measurement electrode in the standard solution adjusted to a constant temperature for 3 minutes, and perform calibration operations in the order of pH 6.86 → pH 9.18 → pH 4.01. Adjust the slurry of the present invention to be measured to 25°C, immerse the electrode of the above pH meter in this slurry, and measure the pH after 1 minute. In addition, the pH of the slurry of the present invention at the washing temperature can be measured by the same method as above, by reading "25°C" as "washing temperature" in the above description.
[0036] <Component (B)> In the soil washing method of the present invention, in order to adjust the pH of the slurry within the above range, an alkali agent (B) [hereinafter referred to as component (B)] can be mixed into the slurry. Also, when the pH of the slurry is too high (for example, when it exceeds 13), an acid can be mixed, or water can be additionally added for dilution. Component (B) includes one or more selected from inorganic base compounds and organic base compounds.
[0037] Examples of the inorganic base compound of component (B) include sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide, while examples of the organic base compound of component (B) include alkylamines such as diethylamine, triethylamine, propylamine, n-butylamine, di-n-butylamine and tert-butylamine, alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and methanolamine, and polyethyleneamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. From the viewpoint of solubility in water, the component (B) is preferably one or more selected from sodium hydroxide, potassium hydroxide, and alkanolamines.
[0038] In addition to the components (A) and (B), the slurry of the present invention may optionally contain components such as oxidizing agents, oxidation promoters, chelating agents, gelling inhibitors, thickeners, fragrances, dyes, pigments, bactericides, preservatives, and pH adjusters (excluding those corresponding to the components (A) and (B)). Examples of the oxidizing agents include hydrogen peroxide, sodium percarbonate, and sodium persulfate. Examples of the oxidation promoters include ferrous sulfate and ferric sulfate. Examples of the chelating agents include phosphoric acid, sodium tripolyphosphate, sodium citrate, and sodium tartrate.
[0039] The soil washing method of the present invention will be described below by giving specific examples, but the soil washing method of the present invention is not limited to the specifically given methods. The soil washing method of the present invention can wash oil-contaminated soil by carrying out step 1 of preparing a slurry having a pH of 9 to 13 containing oil-contaminated soil, a surfactant, and water, and step 2 of settling the soil in the slurry. In each step, the preferred embodiments of the oil-contaminated soil, component (A), component (B) (optional component), and water, the contents of component (A) and water in the slurry and their mixing ratios with respect to the soil, and the preferred pH range of the slurry are the same as those described above.
[0040] <Process 1> Step 1 is a step of mixing oil-contaminated soil, component (A), and water to obtain a slurry with a pH of 9 or more and 13 or less. Step 1 may be a step of mixing oil-contaminated soil and water containing component (A) to obtain a slurry with a pH of 9 or more and 13 or less. The pH of the slurry is adjusted by mixing (B) with the slurry or with water containing component (A). Methods for mixing the slurry include stirring with heavy machinery or a shovel, stirring with a stirrer, and applying vibration. In step 1, for example, 1 m 3 The contaminated soil is placed in the notch tank, a cleaning agent prepared in advance from component (A) and water is added, followed by component (B), and the pH of the slurry is adjusted to between 9 and 13, and the mixture is thoroughly stirred with a shovel, etc. If step 1 is to be carried out in situ, the contaminated soil can be loosened slightly with a backhoe and the same operations as above can be carried out.
[0041] In step 1, from the viewpoint of uniform washing, it is preferable to stir and mix the slurry. The time for stirring and mixing the slurry is not particularly limited, but from the viewpoint of uniform mixing, it is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more, and from the viewpoint of workability, it is preferably 120 minutes or less, more preferably 60 minutes or less, and even more preferably 30 minutes or less.
[0042] <Process 2> Step 2 is a step of allowing the soil in the slurry to settle. Step 2 may be a step of allowing the slurry to stand and allowing the soil in the slurry to settle. Step 2 may also be a step of allowing the slurry to stand and causing the oil adhering to the soil in the slurry to float to the surface and allowing the soil to settle. In step 2, from the viewpoint of oil-water separability, the slurry obtained in step 1 is allowed to stand for preferably 20 minutes or more, more preferably 30 minutes or more, and even more preferably 60 minutes or more, and from the viewpoint of workability, preferably 48 hours or less, more preferably 30 hours or less, and even more preferably 24 hours or less. In the present invention, the term "standing still" refers to a state in which the slurry obtained in step 1 is left standing. During the standing, a stirring operation such as stirring the slurry may be appropriately performed in the same manner as in the mixing method of the slurry described in step 1.
[0043] <Process 3> Note that step 3 of removing oil from the supernatant of the slurry can be optionally carried out after step 2. That is, the soil washing method of the present invention may be a soil washing method further comprising removing oil from the supernatant of the slurry after step 2. As a method for removing oil from the supernatant of the slurry, it is preferable to recover the oil from the supernatant of the slurry using a means selected from an oil absorbing mat, an oil skimmer, a pumping pump, and the like. When the following step 4 is carried out after step 2, step 3 may be carried out after step 4.
[0044] <Step 4> After step 2 or 3, step 4 (hereinafter referred to as step 4) may be performed to separate the soil that has settled from the slurry. Step 4 may be, for example, a simple standing process or a coagulation and sedimentation process. Centrifugation or a dehydrator may be used to separate the soil from the slurry. The soil separated in step 4 may be rinsed with water, but rinsing is not required.
[0045] In the soil washing method of the present invention, the excavated soil may be washed at the location where the soil exists (on-site), or at a location other than the original location (outside the site). For example, the excavated soil can be washed in a washing facility installed in a location other than the site. In this case, for example, soil collected by excavation from the site can be transferred to a washing facility installed in a location other than the site and washed. The washing facility is preferably installed near the site. For example, soil can be collected at a specified location (on-site) in a certain area, and the washing facility can be installed in a location other than the collection location in the same area. In this way, the excavated soil can be washed by installing the washing facility as a so-called on-site plant.
[0046] In addition, the soil washing method of the present invention can wash, for example, excavated soil. Therefore, the present invention provides a method for washing excavated soil, which washes excavated soil contaminated with petroleum compounds. In the method for washing excavated soil of the present invention, rinsing of the washed excavated soil may or may not be performed. From the viewpoint of simplifying the process, the present invention does not require a rinsing step. The excavated soil after washing can be reused by filling it back in the place where it was collected or in another place.
[0047] <Soil Cleaning Agent Composition> In the soil washing method of the present invention, soil contaminated with oil, a soil washing agent composition containing components (A) and (B), and water can be mixed to prepare a slurry having a pH of 9 to 13. That is, the present invention provides a soil washing agent composition containing components (A) and (B).
[0048] The preferred embodiments of the components (A) and (B) in the soil washing composition of the present invention are the same as those of the components (A) and (B) described in the soil washing method of the present invention. The soil washing composition of the present invention may contain any of the optional components described in the soil washing method of the present invention. In the soil washing method of the present invention, a washing solution can be prepared by diluting the soil washing agent composition with water immediately before washing the soil contaminated with oil.
[0049] From the viewpoint of improving cleaning properties, the soil washing agent composition of the present invention contains component (A) in an amount of preferably 1 mass % or more, more preferably 5 mass % or more, and even more preferably 10 mass % or more, and from the viewpoint of handleability, the amount is preferably 85 mass % or less, more preferably 80 mass % or less, and even more preferably 70 mass % or less.
[0050] From the viewpoint of improving cleaning properties, the soil washing agent composition of the present invention contains component (B) in an amount of preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, and from the viewpoint of handleability, the amount is preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 10 mass % or less. EXAMPLES
[0051] Steps 1 and 2 were carried out under the conditions shown in Table 1, and the cleaning properties of the soil cleaning test were evaluated by the following method. The results are shown in Table 1. The following components (A), (B), and water were used for cleaning the soil.
[0052] <Component (A)> A-1: C12(EO)6: Polyoxyethylene linear alkyl (carbon number 12) ether with an average of 6 moles added A-2: C12(EO)5: Polyoxyethylene linear alkyl (carbon number 12) ether with an average added mole number of 5 A-3: C12(EO)8: Polyoxyethylene linear alkyl (carbon number 12) ether with an average of 8 moles added A-4: C12-13(EO)5: Polyoxyethylene branched alkyl ether (having 12 to 13 carbon atoms) with an average number of moles of 5 <(B) component> Potassium hydroxide: Fujifilm Wako Pure Chemical Industries, Ltd. <Water> Tap water
[0053] (1) Preparation of oil-contaminated soil Soil 1 and Soil 2 in Table 1 were prepared by the following method. (1-1) Soil 1 To Akagien Grafting Sand (manufactured by Akagi Horticulture Co., Ltd.), light oil was added so that the amount of light oil per 1 kg of Akagien Grafting Sand was 4,500 mg / kg (Total Petroleum Hydrocarbon, hereinafter referred to as TPH). After stirring with a mortar mixer for 5 minutes, the obtained mixture was put into a pale can and sealed. Then, in order to fix the oil to the sand, it was stored at 25°C for 7 days to prepare Soil 1 contaminated with oil. The Akagien Grafting Sand contained 8.3 mass% of particles with a particle size of 150 μm or less. (1-2) Soil 2 In Soil 1, except that a mixture of No. 6 silica sand (manufactured by Atom House Paint Co., Ltd.) and No. 7 silica sand (manufactured by Atom House Paint Co., Ltd.) mixed at a mass ratio of 1:1 was used instead of Akagien Grafting Sand, Soil 2 was prepared in the same manner as Soil 1. The mixture contained 2 mass% of particles with a particle size of 150 μm or less. Note that the particles with a particle size of 150 μm or less contained in Soil 1 and Soil 2 were measured by the soil particle size test specified in JIS A 1204.
[0054] (2) Washing test (2-1) Preparation of slurry (Step 1) 100 g of the Soil 1 prepared in (1) above was put into a 300 ml polyethylene cup, and the component (A) and water were further mixed so as to be in the ratio shown in Table 1, and manually stirred with a spoon for 1 minute to prepare the slurry shown in Table 1. The component (A) was previously dissolved in water and mixed with the soil. Also, the pH of the slurry was measured by the following method, and potassium hydroxide was added and stirred to adjust it to the value shown in the table.
[0055] <Method for measuring pH> A composite electrode for pH measurement (e.g., glass-sleeve type, manufactured by Horiba, Ltd.) with a saturated potassium chloride aqueous solution (3.33 mol / L) as the pH electrode internal solution was connected to a pH meter (e.g., pH / ion meter F-23, manufactured by Horiba, Ltd.). Next, a pH 4.01 standard solution (phthalate standard solution), a pH 6.86 standard solution (neutral phosphate standard solution), and a pH 9.18 standard solution (borate standard solution) were filled in 100 mL beakers and immersed in a thermostatic bath at 25°C for 30 minutes. The pH measurement electrode was immersed in the thermostatically adjusted standard solution for 3 minutes, and calibration operations were performed in the order of pH 6.86 → pH 9.18 → pH 4.01. The electrode of the pH meter was immersed in the slurry immediately after preparation, and the pH was measured after 1 minute at 25°C.
[0056] (2-2) Settling of soil in slurry (Step 2) The soil obtained in (2-1) above was allowed to stand at 25° C. to allow the soil in the slurry to settle. The standing time for each example is shown in Table 1. After the standing time shown in Table 1 had elapsed, the water layer of the slurry was visually observed from the side of the cup to confirm that the soil had settled and the water was not cloudy.
[0057] (2-3) Oil removal process (process 3) After leaving the slurry of (2-2) to stand, the oil floating on the top of the slurry and the water containing the oil were sucked up with a dropper, and the oil was removed from the supernatant of the slurry.
[0058] (3) Evaluation of cleaning ability After washing, a portion of the soil (sediment) was sampled and subjected to a sensory evaluation of the oily odor and a measurement of TPH. The TPH measurement was performed according to the Oil Pollution Guidelines (March 2006) 2.2.1 Document-3 (Oil Pollution Countermeasures Guidelines, [online], Ministry of the Environment, Internet)<URL:https: / / www.env.go.jp / water / dojo / oil / full.pdf> The test was performed in accordance with the TPH test method using the GC / FID method described in
[0059] (3-1) Sensory evaluation of oily odor After washing, 10 g of the soil was weighed into a 50 ml screw tube, which was then covered and sealed for 10 minutes. After 10 minutes, the tube was opened and the oily odor was evaluated. The sensory evaluation of the oily odor was based on the judgment of one experimenter. The oily odor of soil was evaluated based on the following index. The lower the oily odor sensory evaluation score, the less diesel oil remained in the soil after washing, and the better the soil washing method for washing soil contaminated with oil. Oil odor evaluation index 0: Odorless 1: I smell something that I can't identify. 2: You can detect a faint odor that you can identify. 3: The smell is strong enough that you can detect what it is. 4: There is a strong odor. 5: There is a strong odor.
[0060] (3-2) Measurement of TPH (GC-FID method) The TPH measurement was performed in accordance with the Oil Contamination Guidelines (March 2006), 2.2.1 Document-3, TPH test method by GC / FID method. An example of the procedure is shown below. 1. The settled soil in (2-2) above was collected in a 100 mL screw tube. 2. 30 g of anhydrous sodium sulfate was weighed out, placed in the screw tube, and the tube was then capped and shaken by hand. 3. 30 mL of carbon disulfide was added to the screw tube, shaken for 30 minutes on a shaker, and then allowed to stand for 2 hours. 4. After standing, the supernatant was transferred to a 100 mL measuring flask. 30 mL of carbon disulfide was added again to the screw tube, and the tube was shaken on a shaker for 30 minutes and then left to stand for 2 hours (second extraction). The supernatant was transferred to the measuring flask. 30 mL of carbon disulfide was added again to the screw tube, and the tube was shaken on a shaker for 30 minutes and then left to stand for 2 hours (third extraction). The supernatant was transferred to the measuring flask. 5. Carbon disulfide was added to the measuring flask from step 4 to make exactly 100 mL. 6. After filtering 2 mL of the extracted carbon disulfide solution through a 0.45 μm filter, the light oil content was quantified using an Agilent Technologies 6850A gas chromatograph. A calibration curve was prepared using ASTM standard light oil. The standard sample concentrations were 250, 500, 1,000, 5,000, and 10,000 μg / mL. 7. The measurement results were fitted to the calibration curve to determine the TPH concentration in the sample extract solution, and the oil content in the soil was then calculated using the following formula (1).
[0061]
number
[0062] [Table 1]
Claims
1. A soil washing method comprising obtaining a slurry containing soil contaminated with oil, (A) a surfactant (hereinafter referred to as (A) component), and water, with a pH of 9 to 13, and settling the soil in the slurry.
2. The soil washing method according to claim 1, wherein the slurry is left to stand to allow the soil in the slurry to settle.
3. Furthermore, the soil washing method according to claim 1 or 2, wherein after the soil in the slurry has settled, oil is removed from the supernatant of the slurry.
4. The soil washing method according to claim 1 or 2, wherein the soil contaminated with oil contains 5% by mass or more of particles with a particle size of 150 μm or less.
5. The soil washing method according to claim 1 or 2, wherein the slurry is left to stand for 20 minutes or more to allow the soil in the slurry to settle.
6. The soil washing method according to claim 1 or 2, wherein the soil in the slurry is mixed with water such that the amount of water is 10% by mass or more and 200% by mass or less to obtain the slurry.
7. (A) The soil washing method according to claim 1 or 2, wherein component (A) comprises at least a nonionic surfactant.