Soil cleaning composition

Abstract

To provide a soil cleaner composition that contributes to improving the power of cleaning the soil contaminated with pollutants such as oil.SOLUTION: A soil cleaner composition comprises a component (A) and a component (B) [excluding the component (A)], with the mass content ratio between the component (A) and the component (B), (A) / (B), of 50 / 50 or more and 99 / 1 or less. The component (A): polyoxyalkylene alkyl ether and the component (B): a nonionic polymer compound with a weight average molecular weight of 3,000 or more and 1,000,000 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a soil washing composition and a method for washing soil. [Background technology]

[0002] At the sites or former sites of oil-handling facilities and equipment, such as petroleum refineries, gas stations, storage tanks, and chemical plants, soil can become contaminated with oil due to oil leaks caused by long-term use. Known methods for remediating such contaminated soil include washing the soil, heating the soil, treating the soil with adsorbents, chemically breaking down soil contaminants, and using microorganisms to break down soil contaminants (bioremediation). Among these, soil washing is considered to have advantages such as its ability to treat a wide range of contaminants, its ability to be used as a pretreatment process for bioremediation, and its ability to treat a large amount of contaminated soil.

[0003] Patent Document 1 discloses a method for purifying contaminated soil, etc., which includes a step of transferring the contaminants from the solid content of the soil to a liquid phase by mixing and washing the contaminated soil, etc. with a surfactant, a step of separating the mixture into solid and liquid, and extracting the solid phase as a purified product, and a step of separating the combined surfactant and contaminants after solid-liquid separation. In the examples, it is disclosed that the contaminated soil was washed using an alcohol-based nonionic surfactant. Patent Document 2 discloses a soil washing method in which one or more surfactants selected from nonionic surfactants, anionic surfactants, and amphoteric surfactants are added to the soil and the soil is washed. In the examples, it is disclosed that artificially contaminated soil was washed using polyoxyethylene (10 mol) lauryl ether alone, or a mixture of polyoxyethylene (3 mol)-N-2-hydroxyethyl-N-2-hydroxydodecyl-β-alanine sodium, polyoxyethylene (10 mol) lauryl ether, and sodium oleate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-033812 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-017955 Summary of the Invention [Problem to be solved by the invention]

[0005] In the cleaning of soil contaminated with contaminants such as oil, further improvement in soil cleaning power is desired.

[0006] The present invention provides a soil detergent composition and a soil washing method that contribute to improving the detergency for soil contaminated with contaminants such as oil, for example, soil contaminated with petroleum-based compounds. [Means for solving the problem]

[0007] The present invention relates to a soil detergent composition containing the following components (A) and (B) (excluding component (A)), in which the mass ratio (A) / (B) of the content of component (A) to the content of component (B) is 50 / 50 or more and 99 / 1 or less: Component (A): Polyoxyalkylene alkyl ether (B) Component: a nonionic polymer compound with a weight-average molecular weight of 3,000 to 1,000,000

[0008] The present invention relates to a method for washing soil, which comprises washing soil with the soil washing composition. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a soil washing agent composition and a soil washing method that contribute to improving the detergency for soil contaminated with contaminants such as oil. DETAILED DESCRIPTION OF THE INVENTION

[0010] The mechanism by which the soil detergent composition of the present invention improves the detergency of soil contaminated with contaminants such as oil is not clear, but is presumed to be as follows. When soil is washed with a soil washing composition, it is thought that the amount of component (A), which is an effective component for washing, that acts on contaminants is reduced due to adsorption of the component (A) onto the soil, thereby reducing the washing power of the soil washing composition. Therefore, it is believed that by using the soil cleaning composition of the present invention in combination with component (A) and component (B), component (B) is preferentially adsorbed to the soil over component (A), thereby reducing the amount of component (A) adsorbed to the soil without impairing the soil cleaning action of component (A). As a result, it is thought that the decrease in the amount of component (A) that acts on contaminants can be suppressed, and the detergency of the soil detergent composition is improved. However, the mechanism of action of the soil detergent composition of the present invention is not limited to this mechanism.

[0011] <Soil Cleaning Composition> The soil cleaning composition of the present invention contains the following components (A) and (B) (excluding component (A)), and the mass ratio (A) / (B) of the content of component (A) to the content of component (B) is 50 / 50 or more and 99 / 1 or less. Component (A): Polyoxyalkylene alkyl ether (B) Component: a nonionic polymer compound with a weight-average molecular weight of 3,000 to 1,000,000

[0012] Component (A) is a polyoxyalkylene alkyl ether (excluding component (B)). Component (A) may be, for example, one or more compounds selected from compounds represented by the following general formula (1):

[0013] R 1a -(AO) n -H (1) [In the formula, R 1a represents an alkyl or alkenyl group having 10 to 20 carbon atoms, AO represents an alkyleneoxy group having 2 to 3 carbon atoms, and n represents the average number of moles of AO added, which is a number of 3 to 20.

[0014] R 1a The number of carbon atoms in R is 10 or more, preferably 12 or more, from the viewpoint of detergency against petroleum-based compounds, and is 20 or less, preferably 18 or less, more preferably 14 or less, from the viewpoint of improving detergency. 1a is an alkyl group or an alkenyl group, and preferably an alkyl group. 1a is a straight chain or branched chain, preferably a straight chain.

[0015] From the viewpoint of detergency for petroleum-based compounds, AO is preferably one or more alkyleneoxy groups selected from ethyleneoxy groups and propyleneoxy groups, and more preferably ethyleneoxy groups. When AO contains ethyleneoxy groups and propyleneoxy groups, the ethyleneoxy groups and propyleneoxy groups may be bonded in a block or random manner.

[0016] From the viewpoint of cleanability against petroleum-based compounds, n is 3.0 or more, preferably 4.0 or more, more preferably 5.0 or more, and from the viewpoint of cleanability against petroleum-based compounds, n is 20.0 or less, preferably 10.0 or less, more preferably 8.0 or less, and even more preferably 7.0 or less.

[0017] From the viewpoint of cleaning ability against petroleum-based compounds, the HLB value of component (A) according to the Griffin method is preferably 8.0 or more, more preferably 9.0 or more, even more preferably 10.0 or more, and from the viewpoint of cleaning ability against petroleum-based compounds, it is preferably 15.0 or less, more preferably 13.0 or less, even more preferably 11.0 or less.

[0018] Component (B) is a nonionic polymer compound, and examples of component (B) include compounds represented by the following general formula (b1).

[0019] [ka]

[0020] [In the formula, X is a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a group represented by >N-CH2-CH2-N<. AO is one or more oxyalkylene groups selected from oxyalkylene groups having 2 to 3 carbon atoms. n is the average number of moles added and is 20 to 23,000. s is a group (AO) bonded to X. n and is a number of 1 or more and not more than the valence of X. When AO is two or more types of oxyalkylene groups, AO may be a random bond or a block bond.

[0021] In the general formula (b1), AO is preferably one or more oxyalkylene groups selected from oxyalkylene groups having 2 or more and 3 or less carbon atoms. n is preferably 20 or more, more preferably 70 or more, even more preferably 100 or more, and preferably 23,000 or less, more preferably 20,000 or less, even more preferably 15,000 or less, still more preferably 5,000 or less, and even more preferably 1,000 or less. s is 1 or more and not more than the valence of X, more preferably the valence of X. Specifically, when X is a hydroxyl group (valence 1), s is 1. When X is an alkylene group (valence 2) having 2 to 6 carbon atoms, s is 1 or more and not more than 2, preferably 2; when X is an alkoxy group (valence 1) having 1 to 6 carbon atoms, s is 1; and when X is a group represented by >N-CH2-CH2-N< (valence 4), s is 1 or more and not more than 4, preferably 4.

[0022] Examples of the component (B) in which X in general formula (b1) is a hydroxyl group include compounds represented by the following general formula (b2): The compound represented by general formula (b2) is a compound in which X in general formula (b1) is a hydroxyl group and s is 1. In general formula (b2), preferred embodiments such as AO and n are the same as those in general formula (b1).

[0023] [ka]

[0024] (In the formula, AO represents one or more oxyalkylene groups selected from oxyalkylene groups having from 2 to 3 carbon atoms. n represents the average number of moles added, and is from 20 to 23,000. When AO represents two or more types of oxyalkylene groups, AO may be randomly or block-bonded.)

[0025] Examples of the component (B) in which X in general formula (b1) is a hydroxyl group include one or more nonionic polymers selected from polyethylene ethylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene copolymers. From the viewpoints of improving cleaning properties and one-component stability, one or more nonionic polymers selected from polyethylene ethylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene block polymers are preferred, and polyethylene glycol and polyoxyethylene polyoxypropylene block polymers are more preferred. Furthermore, examples of the component (B) in which X in general formula (b1) is a hydroxyl group include compounds in which an oxyalkylene having from 2 to 3 carbon atoms is added to an alkylene glycol having from 2 to 3 carbon atoms, such as a polyoxyethylene-polyoxypropylene block polymer of ethylene glycol and a polyoxyethylene-polyoxypropylene block polymer of propylene glycol, and the polyoxyethylene-polyoxypropylene block polymer of ethylene glycol is preferred as this component (B).

[0026] Examples of the component (B) in which X in general formula (b1) is an alkoxy group having 1 to 6 carbon atoms include methoxypolyethylene glycol, ethoxypolyethylene glycol, butoxypolyethylene glycol, and methoxypolyethylenepolypropylene glycol.

[0027] Examples of the component (B) in which X in general formula (b1) is a group represented by >N-CH-CH-N< include polyoxyethylene-polyoxypropylene block polymers of ethylenediamine, and such components (A) are commercially available from ADEKA Corporation under the trade name ADEKA Pluronic TR (registered trademark) (e.g., TR-701, TR-704).

[0028] Component (B) is preferably a compound having a polyoxyethylene group (EO) or a polyoxypropylene group (PO). When component (A) contains EO and PO, the EO and PO may be randomly or block-bonded, with block bonding being preferred. Examples of such compounds include EO-PO copolymers, EO-PO-EO copolymers, and PO-EO-PO copolymers.

[0029] An example of the EO-PO copolymer is a compound represented by the following general formula (b3): ​​An example of such a compound is an oxyethylene propylene block polymer. HO(C2H4O) a -(C3H6O) b H (b3) [Wherein, a and b are the average number of moles added. a and b can be selected arbitrarily so that the weight average molecular weight is 3,000 or more and 1,000,000 or less. (C2H4O) in the total molecular weight a It is preferable that the mass of the above is 40 mass % or more and 80 mass % or less.]

[0030] Furthermore, the EO-PO-EO copolymer may be a compound represented by the following general formula (b4): Such a compound is commercially available, for example, from BASF under the trade name Pluronic (registered trademark). HO(C2H4O) c -(C3H6O) d -(C2H4O) e H (b4) [Wherein, c, d, and e are the average number of moles added. c, d, and e can be selected arbitrarily so that the weight average molecular weight is 3,000 or more and 1,000,000 or less. (C2H4O) in the total molecular weightc and (C2H4O) e The total mass of the above is preferably 40% by mass or more and 80% by mass or less.]

[0031] Furthermore, the PO-EO-PO copolymer may be a compound represented by the following general formula (b5): Such a compound is commercially available, for example, from BASF under the trade name Reverse Pluronic (registered trademark). HO(C3H6O) f -(C2H4O) g -(C3H6O) h H (b5) (Wherein, f, g, and h are the average number of moles added. f, g, and h can be selected arbitrarily so that the weight average molecular weight is 3,000 or more and 1,000,000 or less.) g It is preferable that the mass of the above is 40 mass % or more and 80 mass % or less.]

[0032] The weight average molecular weight of component (B) is 3,000 or more, preferably 5,000 or more, more preferably 8,000 or more, from the viewpoint of soil adsorption, and 1,000,000 or less, preferably 750,000 or less, preferably 600,000 or less, more preferably 100,000 or less, from the viewpoint of one-component stability. The weight-average molecular weight of component (B) can be measured by gel permeation chromatography (GPC) using high performance liquid chromatography. The GPC measurement conditions are shown below. *GPC conditions Apparatus: GPC (HLC-8320GPC) manufactured by Tosoh Corporation Column: G4000PWXL + G2500PWXL (Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN=9 / 1 Flow rate: 1.0mL / min Column temperature: 40℃ Detection: RI Sample size: 0.2 mg / mL Standard substance: Polyethylene glycol equivalent (monodisperse polyethylene glycol: molecular weight 250,000, 145,000, 87,500, 46,000, 24,000)

[0033] <Composition and other components of the soil cleaning composition of the present invention> The soil detergent composition of the present invention may contain component (A) in an amount of preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of cleaning ability against petroleum-based compounds, and in an amount of preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of one-component stability.

[0034] The soil detergent composition of the present invention may contain component (B) in an amount of preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more from the viewpoint of improving cleaning properties, and in an amount of preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less from the viewpoint of one-component stability.

[0035] In the soil cleaner composition of the present invention, the total content of components (A) and (B) is preferably 6% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of cleaning ability against petroleum-based compounds, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of one-component stability.

[0036] In the soil cleaning composition of the present invention, the mass ratio (A) / (B) of the content of component (A) to the content of component (B) is 50 / 50 or more, preferably 60 / 40 or more, more preferably 70 / 30 or more, and even more preferably 75 / 25 or more, from the viewpoint of cleaning ability against petroleum-based compounds, and is 99 / 1 or less, preferably 95 / 5 or less, and more preferably 90 / 10 or less, from the viewpoint of sacrificial adsorption effect.

[0037] The detergent composition of the present invention may optionally contain (C) an anionic surfactant (hereinafter referred to as component (C)).

[0038] Component (C) may be one or more compounds selected from fatty acid salts, sulfate ester salts, sulfonate salts, and phosphate ester salts. Component (C) is preferably an anionic surfactant having a molecular weight of 200 to 1,000.

[0039] The fatty acid salts include compounds in which the carbon number of the fatty acid is preferably from 10 to 18. Specific examples of fatty acid salts include alkali metal salts and organic amine salts of capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and mixtures thereof.

[0040] Examples of sulfate salts include salts of sulfate esters having an alkyl or alkenyl group having from 10 to 20 carbon atoms. Specific examples of sulfate salts include sulfate salts (AS) having an alkyl or alkenyl group having from 10 to 20 carbon atoms, polyoxyalkylene alkyl (or alkenyl) ether sulfate salts (AES) (for example, alkyl or alkenyl ether sulfate salts having an average added mole number of alkylene oxide having from 2 to 4 carbon atoms of from 0.5 to 10 moles and having a linear or branched alkyl or alkenyl group having from 10 to 20 carbon atoms), polyoxyalkylene alkyl or alkenyl phenyl ether sulfate salts having a linear or branched alkyl or alkenyl group having from 10 to 20 carbon atoms, and castor oil sulfate salts.

[0041] Specific examples of sulfonates 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 mono-alkyl sulfosuccinates (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.

[0042] Examples of phosphate ester salts include salts of phosphate esters having an alkyl or alkenyl group having 10 to 20 carbon atoms. Specific examples of phosphate ester salts include polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkyl phenyl ether phosphates, and long-chain alkyl phosphates. Examples of phosphate ester salts that can be used include monoesters, diesters, and any mixtures of mono- and di-esters (e.g., sesquiesters).

[0043] From the viewpoint of promoting penetration of component (A), component (C) is preferably one or more anionic surfactants selected from sulfate ester salts (AS), polyoxyalkylene alkyl or alkenyl ether sulfate ester salts (AES), and alkylbenzene sulfonates (LAS). The component (C) is more preferably one or more anionic surfactants selected from sulfate ester salts (AS) and polyoxyalkylene alkyl or alkenyl ether sulfate ester salts (AES).

[0044] Component (C) is one or more anionic surfactants selected from alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, and alkylbenzene sulfonates, preferably anionic surfactants having a molecular weight of 200 or more and 1,000 or less, and more preferably one or more anionic surfactants selected from alkyl sulfate ester salts and polyoxyethylene alkyl ether sulfate ester salts, and anionic surfactants having a molecular weight of 200 or more and 1,000 or less.

[0045] From the viewpoint of improving detergency, the alkyl sulfate salt is preferably an alkyl sulfate salt having an alkyl group with 10 to 18 carbon atoms. From the viewpoint of improving detergency, the polyoxyethylene alkyl ether sulfate is preferably a polyoxyethylene alkyl ether sulfate having an alkyl group with 10 to 18 carbon atoms and an average number of moles of ethylene oxide added of 0.5 to 5.0. From the viewpoint of improving cleaning properties, the alkylbenzenesulfonic acid is preferably an alkylbenzenesulfonate having an alkyl group with 10 or more and 14 or less carbon atoms.

[0046] Examples of the salt of the anionic surfactant of component (C) include alkali metal salts, alkaline earth metal salts, amine salts, ammonium salts, and alkanolamine salts. From the viewpoint of one-component stability, the salt of the anionic surfactant of component (C) is preferably a salt selected from alkali metal salts and alkanolamine salts, and more preferably a sodium salt or alkanolamine salt. The alkanolamine salt is preferably a salt of an alkanolamine having from 1 to 3 alkanol groups each having from 1 to 3 carbon atoms.

[0047] The soil detergent composition of the present invention may contain component (C) in an amount of preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more from the viewpoint of improving cleaning properties, and in an amount of preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less from the viewpoint of suppressing foaming.

[0048] In the soil detergent composition of the present invention, the mass ratio (A) / (C) of the content of component (A) to the content of component (C) is preferably 85 / 15 or more, more preferably 88 / 12 or more, and even more preferably 90 / 10 or more, from the viewpoint of improving cleaning performance, and is preferably 99 / 1 or less, more preferably 98 / 2 or less, and even more preferably 95 / 5 or less, from the viewpoint of one-component stability.

[0049] The soil cleaning composition of the present invention may contain water from the viewpoints of ease of handling and storage stability. The water may be tap water, groundwater, river water, or lake water. The water may be the remainder excluding component (A), component (B), component (C), and other optional components.

[0050] The soil detergent composition of the present invention may contain a nonionic surfactant other than components (A) and (B) (hereinafter referred to as "other nonionic surfactants"), such as sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, fatty acid monoglycerides, and polyethylene glycol fatty acid esters. From the viewpoint of cleaning performance, the proportion of component (A) in the nonionic surfactants contained in the soil detergent composition of the present invention (excluding component (B)) is preferably 50 mass% or more, more preferably 60 mass% or more, and 100 mass% or less. The proportion of component (A) in the nonionic surfactants contained in the soil detergent composition of the present invention (excluding component (B)) may be 100 mass%, i.e., the nonionic surfactant contained in the soil detergent composition of the present invention may be a nonionic surfactant consisting of component (A).

[0051] The soil washing composition of the present invention may optionally contain a soil dispersant, an antifoaming agent, an antiseptic, and a solvent.

[0052] The soil to be treated with the soil detergent composition of the present invention is not particularly limited, and can be used, for example, to wash soil contaminated with petroleum compounds. The soil detergent composition of the present invention may be used to wash oily stains such as petroleum compounds in soil. Examples of petroleum compounds include petroleum hydrocarbons. Examples of petroleum compounds include gasoline, kerosene, light oil, heavy oil, and machine oil.

[0053] <How to wash soil> The present invention provides a method for washing soil, which comprises washing soil with the soil washing composition of the present invention. The method for washing soil of the present invention may be a method for washing soil in which the soil washing composition of the present invention is brought into contact with the soil. The present invention also provides a method for washing soil contaminated with petroleum compounds using a soil washing composition containing component (A), component (B), and water, comprising: The present invention also provides a method for washing soil, in which the content of component (A) and the content of component (B) are used so that the mass ratio (A) / (B) is 50 / 50 or more and 99 / 1 or less. The soil washing method of the present invention can be appropriately applied to the matters described for the soil washing composition of the present invention. For example, specific examples and preferred embodiments of components (A), (B), and (C) in the soil washing method of the present invention are the same as those in the soil washing composition of the present invention. The soil washing method of the present invention can use the soil washing composition of the present invention.

[0054] In the soil washing method of the present invention, soil and water are mixed together, and then a soil washing composition containing components (A) and (B) can be added to the mixture. This soil washing composition may optionally contain component (C). In the soil washing method of the present invention, soil and water are mixed to prepare a mixture having a specific gravity of preferably 1.05 or more, more preferably 1.18 or more, and preferably 1.40 or less, more preferably 1.25 or less, and this mixture can be mixed with a soil washing agent composition containing component (A) and component (B).

[0055] In the soil washing method of the present invention, the soil washing composition can be used so that the amount of component (A) mixed with the soil and water mixture is preferably 0.04 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.1 mass% or more from the viewpoint of washing performance, and preferably 0.4 mass% or less, more preferably 0.3 mass% or less, and even more preferably 0.2 mass% or less from the viewpoint of economy.

[0056] In the soil washing method of the present invention, the soil washing composition can be used so that the amount of component (B) mixed with the soil and water mixture is preferably 0.01 mass% or more, more preferably 0.015 mass% or more, and preferably 0.1 mass% or less.

[0057] In the soil washing method of the present invention, the soil washing composition can be used so that the total amount of components (A) and (B) relative to the soil and water mixture is preferably 0.05 mass% or more, more preferably 0.06 mass% or more, and preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and even more preferably 0.2 mass% or less.

[0058] In the soil washing method of the present invention, rinsing of the washed soil may or may not be performed. From the viewpoint of simplifying the process, the rinsing step may not be performed in the present invention.

[0059] In the soil washing method of the present invention, soil can also be washed by contacting a mixture containing the soil washing composition of the present invention and water and having a pH of 6 to 8. That is, in the soil washing method of the present invention, a mixture containing component (A), component (B), and water and having a pH of 6 to 8 can be mixed with soil. The mixture may be the soil washing composition of the present invention or a dilution thereof with water. The mixture may also contain the optional components described above for the soil washing composition of the present invention.

[0060] The contents of components (A) and (B) in the mixture are preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.0% by mass or less.

[0061] Furthermore, in the mixture, the mass ratio (A) / (B) of the content of the component (A) to the content of the component (B) is 50 / 50 or more, preferably 60 / 40 or more, more preferably 70 / 30 or more, and even more preferably 75 / 25 or more, from the viewpoint of cleaning properties against petroleum-based compounds, and is 99 / 1 or less, preferably 95 / 5 or less, and more preferably 90 / 10 or less, from the viewpoint of sacrificial adsorption effect.

[0062] The soil washing method of the present invention can be preferably applied to a soil excavation and washing method in which soil is excavated and the excavated soil obtained is washed, and a soil washing method in which a washing solution is injected into the soil to wash the soil.

[0063] In the soil washing method of the present invention, the soil may be washed at the location where the soil is present (on-site), or at a location other than the original location (off-site). For example, the soil can be washed in a washing facility installed at a location other than the on-site. In this case, for example, soil collected by excavation from the on-site can be transported to a washing facility installed at a location other than the on-site and washed. The washing facility is preferably installed near the on-site. For example, soil can be collected at a predetermined location (on-site) within a certain area, and the washing facility can be installed at a location other than the collection location within the same area. In this way, the soil can be washed using a washing facility installed as a so-called on-site plant. The washed soil can be reused by filling it back in the location where it was collected or at another location.

[0064] Furthermore, in the soil washing method of the present invention, for example, the soil can be washed by injecting the soil washing composition of the present invention or a washing solution obtained by diluting the washing composition with water into the soil without excavation. In the soil washing method of the present invention, for example, the soil washing composition of the present invention can be injected into contaminated soil at a predetermined location, allowed to pass through the contaminated soil, and then recovered at a location different from the predetermined location. In this way, contaminants in the soil, such as petroleum-based compounds, can be captured and recovered by the soil washing composition of the present invention passing through the soil. The soil washing composition of the present invention can be recovered by a pumping method, specifically by a pumping means such as a pump. Then, contaminants such as petroleum-based compounds can be separated from the recovered soil washing composition of the present invention. [Example]

[0065] A soil detergent composition (solid content concentration: 100% by mass) was prepared using the following components (A), (B), and (C), and a cleaning test was carried out in the following manner. <Component (A)> Component (A-1): Polyoxyethylene alkyl ether (alkyl group carbon number: 12, average number of ethyleneoxy groups added: 6), manufactured by Kao Corporation (A-2) Polyoxyethylene alkyl ether (alkyl group carbon number: 12, average number of ethyleneoxy groups added: 4), manufactured by Kao Corporation Component (A-3): Polyoxyethylene alkyl ether (alkyl group carbon number: 18, average number of ethyleneoxy groups added: 8), manufactured by Kao Corporation <(B) component> (B-1) Polyethylene glycol (weight average molecular weight 6,000), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (B-2) Polyethylene glycol (weight average molecular weight 13,000), manufactured by Sanyo Chemical Industries, Ltd. (B-3) Polyethylene glycol (weight average molecular weight 600,000), manufactured by Meisei Chemical Industry Co., Ltd. (B-4) Polyoxyethylene-polyoxypropylene copolymer (weight average molecular weight 10,000), product name: ADEKA Pluronic F-68, manufactured by ADEKA Corporation <(B') component> (B'-1) Polyethylene glycol (weight average molecular weight 1,000), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (B'-2) Polyethylene glycol (weight average molecular weight 2,000,000), manufactured by Fujifilm Wako Co., Ltd. (B'-3) Polyethyleneimine (weight average molecular weight 10,000), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. <(C) component> (C-1) Alkyl sulfate triethanolamine salt (alkyl group carbon number: 12), manufactured by Kao Corporation Water: Tap water

[0066] (1) Cleaning test (1-1) Preparation of simulated oil-contaminated fine-grained soil A simulated oil-contaminated fine-grained soil was prepared by mixing 400 g of finely powdered clay for civil engineering (Sumiclée, Sumitomo Osaka Cement Co., Ltd.) and 6.2 g of diesel fuel with a hand mixer until homogeneous. The diesel fuel had been previously dyed with Sudan (IV) (Fujifilm Wako Pure Chemical Industries, Ltd.). The finely powdered clay for civil engineering contained 90% or more by mass of fine particles with a particle size of 0.075 mm or less.

[0067] (1-2) Washing of simulated oil-contaminated fine soil A 100 ml Erlenmeyer flask was charged with 16.7 g of simulated oil-contaminated fine soil and 83.3 g of water to prepare a mixture with a specific gravity of 1.2. The soil detergent composition shown in the table was then added to the Erlenmeyer flask so that the total solids concentration of all components in the mixture of simulated oil-contaminated fine soil and water was 0.2 mass %, and the mixture was then stirred with a magnetic stirrer for 30 minutes. The HLB values ​​of component (A) in the table are those determined by the Griffin method. After 30 minutes, stirring was stopped, and the mixture was divided into two 50 ml Violamo centrifuge tubes and centrifuged at 1000 G for 5 minutes in a multi-rack centrifuge (H-80F, manufactured by Kokusan Co., Ltd.). After centrifugation, the supernatant was collected and subjected to UV measurement by the method described below to evaluate the cleaning properties of the soil detergent composition.

[0068] (1-3)UV measurement method 1.0 g of the supernatant collected in (1-2) above was taken and diluted with water to 5.0 g to obtain a sample of the same concentration. The absorbance at 260 nm of this sample was measured using an ultraviolet-visible spectrophotometer (UV-160A, manufactured by Shimadzu Corporation). It is believed that the greater the absorbance, the greater the amount of oil recovered in the supernatant by washing. Therefore, the greater the absorbance value, the greater the cleaning ability of the soil washing composition.

[0069] [Table 1]

Claims

1. A method for washing soil, comprising washing the soil with a soil washing composition containing the following components (A) and (B), wherein the mass ratio (A) / (B) of the content of component (A) to the content of component (B) is 70 / 30 or more and 95 / 5 or less, wherein the soil is contaminated with petroleum-based compounds, and the soil washing composition is used so that the total amount of components (A) and (B) relative to a mixture of soil and water is 0.05% by mass or more and 0.5% by mass or less: Component (A): a polyoxyalkylene alkyl ether represented by the following general formula (1): R 1a -(AO) n -H (1) [In the formula, R 1a represents a linear alkyl or alkenyl group having from 10 to 20 carbon atoms, AO represents an alkyleneoxy group having from 2 to 3 carbon atoms, and n represents the average number of moles of AO added, which is from 3 to 20.] Component (B): a nonionic polymer compound having a weight-average molecular weight of 3,000 to 1,000,000, which is at least one selected from polyethylene glycol, polypropylene glycol, and oxyethylene-oxypropylene copolymers

2. A method for cleaning soil as described in claim 1, wherein the cleaning composition further contains (C) an anionic surfactant.

3. A method for washing soil as described in claim 2, wherein the component (C) is one or more selected from alkyl sulfate ester salts and polyoxyethylene alkyl ether sulfate ester salts, and is an anionic surfactant having a molecular weight of 200 or more and 1,000 or less.

4. The method for washing soil according to any one of claims 1 to 3, wherein the HLB of component (A) measured by the Griffin method is 8.0 or more and 15.0 or less.

5. A method for cleaning soil described in any one of claims 1 to 4, wherein the cleaning composition contains 5% by mass or more and 40% by mass or less of component (A) and 1% by mass or more and 40% by mass or less of component (B).

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