JP2005138062A - Method of separating oil content in water and determination method of oil content in water containing oil content using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method of separating an oil content from water, in which specific polymeric compound is used, the oil content in the water is caught in solid aggregate with very little moisture content, and even if an amount of the addition of flocculant increases, it does not become a dispersion stabilizer of the oil content. <P>SOLUTION: The method of separating oil content from water comprises (a) a process of adding, to water containing the oil content maintaining a predetermined temperature, low-temperature hydrophilic-high temperature hydrophobic heat-reversible thermosensitive polymeric compound having a higher transition temperature than the temperature of the water to dissolve and prepare an aqueous solution, (b) a process of warming the aqueous solution obtained in (a) more than the transition temperature of the low-temperature hydrophilic-high temperature hydrophobic heat-reversible thermosensitive polymeric compound, and forming solid matter of thermosensitive polymeric compound catching the oil content, and (c) a process of separating the solid matter from a water phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel method for separating oil in water and a method for quantifying oil in water containing oil using the separation method.

Most of COD and BOD in industrial wastewater and household wastewater containing oil depend on oil, and therefore, BOD can be greatly reduced by removing this oil.
Therefore, these wastewaters are discharged into sewage and rivers as water quality standards for designated water areas based on the Water Quality Conservation Law, or after removing oil to a level below the regulation standards of the Sewerage Law.

  By the way, as a method for removing oil in these wastewaters, gravity or pressurized flotation separation methods occupy the mainstream, but it is sufficient to remove oil below the reference value that can be discharged as described above. Since it does not require oil removal, it is not necessarily a suitable method for use in purification to completely remove oil or analysis for measuring oil content.

  On the other hand, it is known that when an organic or inorganic flocculant is used, oil in an emulsified state can be efficiently captured. And as such a flocculant, the flocculant (refer patent document 1) which consists of a powdery mixture of the calcium chloride impregnation clay for cutting oil wastewater, and an anionic polymer compound, a cationic polymer compound, or a cationic polymer A flocculant composed of a powdered mixture of a compound and an anionic polymer compound (see Patent Document 2), a flocculant for car wash drainage containing alginate and ammonium sulfate (see Patent Document 3), and an oil-water separation ability produced by microorganisms An oil separating agent comprising a flocculant mainly composed of a polymer compound (see Patent Document 4), an oil-absorbing polymer that absorbs oil to form a floc, and a flocculant for agglomerating fine particles in water (Patent Document 5) Have been proposed).

  However, all of these flocculants have been proposed for the treatment of a large amount of industrial wastewater, and are intended for quantitative separation and analysis of oil completely or for obtaining purified water containing no oil. Is not always satisfactory.

  On the other hand, there are Japanese Industrial Standard “Factory Wastewater Test Method (JIS K 0102)” and sanitary test methods as methods for quantifying mineral oils and animal and vegetable oils, which are one of the trace pollutants in environmental water. In the method, a sample is made slightly acidic, extracted with hexane, and then the substance remaining after volatilization of hexane is weighed and quantified.

  However, in this quantification method, since a large amount of sample water is used to collect a large amount of hexane, a complicated operation and a large amount of heat energy are required, so that the processing cost is inevitable.

Recently, as a technique suitable for on-site analysis, a heavy metal detection material and a method for producing the same (see Patent Document 6), a method for quantifying environmental pollutants, and a kit for quantification used therein (see Patent Document 7) have been proposed. It was.
However, this technique aims to quantify harmful heavy metal ions and uses a hydrophobic chelate-forming color reagent that forms a chelate compound with a heavy metal ion, and does not form a chelate compound or color. It is not used to determine the oil content.

JP 51-30585 (Claims and others) JP-A-60-202787 (Claims and others) JP 2003-170007 (Claims and others) Japanese Patent Laid-Open No. 2000-70955 (claims and others) JP 2000-328048 (Claims and others) JP 2003-149226 A (Claims and others) JP 2003-194798 A (Claims and others)

  The present invention uses a specific polymer compound, traps oil in water in a solid agglomerate having a very low water content, and can be a dispersion stabilizer for oil even if the amount of flocculant added is increased. Providing a new method for separating oil in water, and a new method capable of on-site analysis of minute amounts of oil in water such as environmental water in the field simply, quickly, with high accuracy, at low cost and without secondary contamination It was made for the purpose of providing a method for quantitatively determining the oil content in water.

  As a result of intensive research in view of the above problems, the present inventors made use of the characteristics of a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound to solidify the total amount of trace oil in water on the high temperature side. The oil content can be separated and concentrated in the product, and the amount of oil can be quantified easily, quickly and with high accuracy by using an oil suspension obtained by dissolving this solid in a small amount of water on the low temperature side. Based on this finding, the present invention has been completed.

  That is, the present invention comprises (a) a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than the oil-containing water maintained at a predetermined temperature, (B) The aqueous solution obtained in (a) is heated to a temperature higher than the transition temperature of the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound to capture the oil component. A step of forming a solid of a molecular compound, and (c) a method of separating oil in water, the step of separating the solid from the aqueous phase, and (b) oil-containing water kept at a predetermined temperature. A step of adding a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than that temperature to dissolve and preparing a mixed solution, (b) mixing obtained in (a) Liquid above low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive high content In the step of forming a solid of a heat-sensitive polymer compound that has captured the oil by raising the temperature above the transition temperature of the compound, (c) a step of separating the solid from the aqueous phase, (d) in (c) Adding a predetermined amount of pure water to the obtained solid at a temperature lower than the transition temperature of the thermosensitive polymer compound to form an aqueous suspension of oil; and (e) the aqueous suspension. The present invention provides a method for quantifying oil content in oil-containing water, which comprises the step of calibrating the oil content in a suspension.

Next, the present invention will be described in more detail.
The present invention adds a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than that temperature to waste water containing a trace amount of oil held at a predetermined temperature, and below the transition temperature. Dissolve, then raise the temperature above the transition temperature to capture (capture / concentrate) the oil in the solidified / precipitated solid, and then separate the solid from the aqueous phase. A separation method and a solid obtained by using the separation method are dissolved by adding a predetermined amount of pure water at a temperature lower than the transition temperature of the thermosensitive polymer compound, and the thermosensitive polymer. This is a method for quantifying the oil content in oil-containing water by suspending the oil content using a compound aqueous solution as a dispersion medium and measuring the turbidity and the like.
Here, the transition temperature refers to a lower critical solution temperature (Lower Critical Solution Temperature).

First, in order to facilitate understanding of the present invention, the function and action mechanism of the low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound in the present invention will be described.
The present invention captures oil in water in a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound and then separates it from the aqueous phase. The solid obtained by using this separation method The turbidity is measured by redispersing the water in water. The low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound functions as follows in each stage.

That is, the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound added to the oil-containing water in the separation step is dehydrated and becomes hydrophobic when the temperature is raised above the transition temperature. Produces sex. As a result, the oil is taken into the solidified polymer solid (solid) and highly concentrated. Therefore, if the solid is separated from the aqueous phase, the oil is separated.
In this way, the oil present in an extremely dilute state in water is also subjected to a concentration treatment and becomes separable.

  Oil-containing flocs produced by the conventional agglomeration method are agglomerates of hydrophilic colloids and contain a large amount of moisture, but the solids of the present invention utilize the high-temperature hydrophobic characteristics of thermosensitive polymer compounds to absorb moisture. It can be recovered as a low solid content.

  Next, in the quantitative method step, the low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound aqueous solution functions as an oil dispersion medium. A thermosensitive polymer compound exhibits a surfactant-like property having both hydrophobic and hydrophilic properties, and its aqueous solution forms a micelle including the oil component, whereby the oil component can be suspended and dispersed as small particles. it can. The suspension remains highly stable over time and its turbidity is proportional to the oil content. Moreover, since the suspended particle diameter can be kept small, high sensitivity can be obtained in turbidity measurement.

  Thus, in the present invention, a trace amount of oil in water is rapidly and highly quantified by using a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound as a concentration medium and an aqueous solution thereof as a dispersion medium. be able to.

  The mechanism of substance uptake in the extraction process by the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound, which is a medium for extraction and dispersion in the present invention, is determined between the substance to be separated and the thermosensitive polymer compound. It uses affinity based on hydrophobicity, and the extraction of the target substance with a thermosensitive polymer compound is basically the case of the organic solvent extraction method (by controlling the partition coefficient between water and organic solvent). Can be thought of as well.

  That is, the property of the polymer aggregate phase as an extraction solvent is, for example, in the case of poly (N-isopropylacrylamide), the partition coefficient between the water-thermosensitive polymer compound aggregate phase is the partition constant between water and octanol (the hydrophobicity of the compound). (See “Analytical Chemistry”, 1999, Vol. 71, p. 4506-4512), and the determination of oil-in-water according to the present invention. The method is considered to be consistent with the measurement method of hexane extract.

  The mechanism of action of the low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound aqueous solution in the present invention as a dispersion medium is a micelle-like core with the hydrophobic group of the polymer on the inside and the hydrophilic group on the outside. It is considered that a hydrophobic substance uptake field is formed in an aqueous solution, and the oil is retained and dispersed to maintain a stable suspension of oil-in-water. The microscopic hydrophobic environment formed by the aqueous solution of the thermosensitive polymer compound is on the order of lower alcohol on average ["Taranta", 1998, Vol. 46, p. 541-550].

Next, specific low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compounds used in the present invention will be described.
The low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound used in the present invention is a polymer hydrate (oxonium hydroxide) produced at a predetermined temperature, that is, a low temperature below the transition temperature. It has the physical property that the polymers are aggregated and become solid by dehydrating at a higher temperature than the transition temperature, and it is hydrophilic and dissolves in water below the transition temperature, but it is higher than the transition temperature. Is hydrophobic and becomes a solid.

  In the present invention, a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature in the range of 0 to 90 ° C., preferably 10 to 60 ° C. is used. From the viewpoint of on-site analysis using the method for quantifying oil content in the oil-containing water of the present invention, those having a transition temperature that is hydrophilic at ambient temperature and hydrophobic when heated are preferred.

  This transition temperature can be changed depending on the type of monomer constituting the thermosensitive polymer compound and the content ratio of the comonomer, but by adjusting the salt concentration and pH of the aqueous solution. Can also be changed.

The low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound used in the present invention is a known substance, and examples thereof include Nn-propylacrylamide, N-isopropylacrylamide, N-cyclopropylacrylamide, The weight of at least one monomer selected from N, N-ethylmethylacrylamide, N, N-diethylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine and the corresponding methacrylamide derivative. Copolymers or copolymers, or these monomers and hydrophilic monomers such as N-vinylpyrrolidone, vinylpyridine, acrylamide, methacrylamide, N-methylacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxymethyl acrylate Relate, unsaturated carboxylic acids such as acrylic acid and methacrylic acid and their salts, unsaturated sulfonic acids such as vinyl sulfonic acid and styrene sulfonic acid, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl Acrylamide, etc. or hydrophobic monomers such as acrylic acid esters such as ethyl acrylate, methyl methacrylate, glycidyl methacrylate, methacrylic acid, N-alkyl substituted acrylamides or methacrylamides, vinyl chloride, acrylonitrile, styrene, vinyl acetate, etc. And a copolymer with at least one monomer selected from.
Among them, a polymer of at least one monomer selected from N, N-diethylacrylamide, N-isopropylacrylamide, Nn-propylacrylamide, N-cyclopropylacrylamide or a corresponding N-methacrylamide derivative Alternatively, a copolymer is particularly preferably used.

  In general, copolymerization with a hydrophilic monomer raises the transition temperature compared to a homopolymer, and copolymerization with a hydrophobic monomer lowers the transition temperature than a homopolymer. Thus, a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound having a desired transition temperature can be formed.

  The transition temperature can also be changed by adjusting the salt concentration and pH when the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound is used as an aqueous solution. Low temperature hydrophilicity-high temperature hydrophobic thermoreversible thermosensitive polymer compound solubilization and solid agglomeration are due to hydration and dehydration, respectively. Promotes aggregation of thermoreversible thermosensitive polymer compounds. As the salts, those having a large salting-out effect are useful, and various salts other than sodium chloride and sodium perchlorate can be used, and it is preferable to select a salt and a concentration suitable for each system. .

Next, the method for separating oil in water according to the present invention will be described according to each step.
Step (a) First, a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than that temperature is added to an oil-containing water kept at a predetermined temperature and dissolved to prepare an aqueous solution.
The oil-containing water can be arbitrarily selected from, for example, a water purification and reuse stock solution, a sample for oil content determination, and the like.

  Since the separation method of the present invention is particularly effective for water with a small amount of oil content, when the oil concentration is high, it is advantageous to apply to water containing a small amount of oil after the primary treatment by an oil-water separation method such as a conventional coagulation method. It is.

Examples of the oil component include mineral oil and animal and vegetable oils, specifically lubricating oil such as engine oil, liquid paraffin, salad oil, rapeseed oil, olive oil, sesame oil and safflower oil.
The amount of the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound can be appropriately determined according to the treated water. Even if it is added in a large amount, it is separated from water in the subsequent process, so there is no particular problem.

(B) Step Next, the obtained aqueous solution is heated to a temperature equal to or higher than the transition temperature of the low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound, and the solid of the thermosensitive polymer compound capturing the oil component. To form.
The temperature elevation temperature may be equal to or higher than the transition temperature, and is preferably set to be slightly higher than the transition temperature in terms of cost.

(C) Step Next, the solid is separated from the aqueous phase. This separation needs to be performed above the transition temperature. For the separation, the solid matter may be taken out by an appropriate means, and the aqueous phase may be removed by an appropriate means.

On the other hand, the method for quantifying the oil content in the oil-containing water of the present invention is performed according to each step.
(B) Step First, a predetermined amount of oil-containing water such as environmental water is collected and used as a sample. Examples of the environmental water include industrial wastewater, inflow water to a sewage treatment plant, sewage treatment plant treatment water, river water, lake water, seawater, and the like. Moreover, the mineral oil and animal and vegetable oil mentioned above can be mentioned as an oil component of a measuring object substance.
The amount of sample collected per measurement is preferably a predetermined amount within the range of 10 to 200 ml from the viewpoints of simplicity, speed, and low cost.

  Next, a predetermined amount of a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than the ambient temperature is added to this sample, mixed well and dissolved to obtain a mixed solution. The predetermined amount is usually added to a specific concentration within the range of 100 to 500 mg / liter. Within this concentration range, the quantification method of the present invention can obtain particularly high measurement accuracy.

The low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound is advantageously prepared in advance as an aqueous polymer solution and added to the sample in a predetermined amount from the viewpoint of shortening the working time. In this case, the concentration of the polymer aqueous solution is preferably 1 to 2% by mass.
In order to adjust the transition temperature, salts and pH adjusters can be added as necessary, but it is also preferable to prepare them in advance as an aqueous solution and add a predetermined amount thereof.

(B) Step Next, the liquid mixture (dissolved solution) obtained in the step (a) is heated to a temperature higher than the above transition temperature (the transition temperature when adjusted by addition of salts or the like). At this stage, the low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound becomes hydrophobic and precipitates as a solid. Then, all of the oil is extracted and concentrated in the solid.

Step (c) Next, the solid is separated from the liquid portion using an appropriate means (such as decantation) while keeping the temperature above the transition temperature. By shaking at the time of this separation, the solid matter has a property of adhering to the wall surface of the container (a container such as a glass container or polypropylene), and only the solid substance can be obtained easily and rapidly. Moreover, as a heating means, simple means, such as a hot water bath, can be taken.

(D) Step Next, a predetermined amount of pure water is added to the solid material obtained in step (c) at a temperature lower than the transition temperature of the heat-sensitive polymer compound to dissolve it, and an aqueous suspension of oil is added. A turbid liquid is formed. The temperature lower than the transition temperature may be the same temperature as the ambient temperature in the step (a). In addition, the specified amount of pure water is a specific amount in which the concentration of the thermosensitive polymer compound is in the range of 1 to 2 g / liter. It is particularly preferable in that it can be obtained.

(E) Step Next, the oil content in the suspension obtained in the step (d) is weighed. The calibration method is performed by measuring turbidity, measuring absorbance, or using other appropriate methods to determine the content of trace oil in the sample.

The calibration method in step (e) is particularly preferably a measurement method based on turbidity from the viewpoint of on-site analysis. Although the turbidity varies depending on the type and particle size of the suspended substance and the measurement method, the following equation has been obtained empirically between the suspended solid concentration (C), particle size (d), and turbidity (T). (Refer to the water supply test method explanation)
C = K · T · d ^m
K and m are constants that vary depending on the turbidity and the measurement method.

  That is, the turbidity concentration and turbidity are in a proportional relationship under a certain condition, and a larger turbidity is obtained as the particle size is smaller. In the present invention, by using an aqueous solution of a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound as a dispersion medium, the oil can be used for measurement as a stable turbid substance having a smaller constant particle size. In this respect, turbidity measurement is particularly advantageous.

The turbidity measurement method includes a transmitted light method, a scattered light method, and an integrating sphere method. In the present invention, any method can be applied. In the case of using the transmitted light method, the Lambert-Beer law is applied in a certain concentration range, and quantification can be performed using a calibration curve method. In this case, it is desirable that the measurement wavelength is in a wavelength range of 600 nm or more which is usually used for turbidity measurement.
In the present invention, by using an aqueous solution of a low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound as a dispersion medium, a reproducible result can be obtained with constant experimental conditions.

  The quantification method of the present invention is preferably performed using a quantification kit in which tools are combined so that each step can be smoothly performed. FIG. 1 is a perspective view showing an example of such a quantification kit.

  The kit shown in FIG. 1 collects a necessary amount (30 ml) of environmental water, a container (1) for preparing a measurement sample, and an aqueous HCl solution having a predetermined concentration (0.5 mol / liter) a predetermined number of times. A container (2) containing a minute amount (30 times), a container containing a predetermined concentration (1.2% by mass) of a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound aqueous solution a predetermined number of times (30 times) ( 3) a container (4) containing a predetermined concentration (3.2 mol / liter) of NaCl aqueous solution for a predetermined number of times (30 times), a container (5) containing pure water for a predetermined number of times (30 times), and a container (2 ) From a predetermined amount (0.5 ml) of HCl aqueous solution, and add the dropper (6) to the container (1) and a predetermined amount (1.0 ml) of the thermosensitive polymer compound aqueous solution from the container (3). Dropper to collect and add to container (1) 7) A predetermined amount (3.0 ml) of NaCl aqueous solution is collected from the container (4) and added to the container (1), a dropper (8), and a predetermined amount (5.0 ml) of purified water from the container (5). A syringe (9) for collecting and adding to the container (1), and a syringe (10) fitted with a lock needle at the tip for extracting the aqueous phase from the container (1) after aggregating the thermosensitive polymer compound And a cup (11) for bathing the container (1).

  In consideration of ease of use and the like, the container (1) is a glass screw mouth bottle with a polypropylene lid, the containers (2), (3), (4) and (5) are polypropylene screw mouth bottles, The syringes (6), (7), and (8) are made of polyethylene, the syringes (9) and (10) are made of polypropylene, and the cup (11) is made of a polyethylene cup (11).

A method for quantifying oil content in environmental water using the quantification kit shown in FIG. 1 will be described according to each step.
Step (a) First, 30 ml of environmental water is collected in a container (1), and 0.5 ml of an aqueous HCl solution in the container (2) is added thereto using a dropper (6) and mixed. Next, 1.0 ml of the aqueous solution of low temperature hydrophilicity-high temperature hydrophobic thermoreversible thermosensitive polymer compound in the container (3) is added and mixed using a dropper (7). Further, add 3.0 ml of NaCl aqueous solution in the container (4) using a dropper (8) and mix. Here, the aqueous solution of the thermosensitive polymer compound may be added after the mixed aqueous solution of HCl and NaCl is added first.

(B) Step Next, immerse the container (1) in a cup (11) filled with hot water above the prepared transition temperature, take out after about 1 minute, and vigorously shake to precipitate solid matter. In order to condense and further solidify into a lump, it is immersed again in hot water and left for about 1-3 minutes.

(C) Step Next, the container (1) was taken out from the hot water, the lid was removed, and the syringe (10) was inserted into the bottom of the container (1) while keeping the temperature above the transition temperature, and then condensed and floated. Remove the liquid slowly by suction, taking care not to take up solids. At this time, the solid matter that has floated adheres to the surrounding glass inner wall surface as the liquid level drops. Therefore, by this operation, the outflow of solid matter due to decantation can be greatly reduced, and variations in measurement results can be suppressed.

(D) Step Next, after cooling the solid-containing container (1) obtained in the step to a temperature (ambient temperature etc.) lower than the above transition temperature, 5 ml of pure water in the container (5) is syringed (9). Is added and shaken to dissolve the heat-sensitive polymer compound constituting the solid, thereby obtaining an aqueous suspension of oil.

(E) Step Finally, the turbidity (for example, absorbance at 660 nm) of the obtained aqueous suspension of oil is measured, and the amount of oil in the environmental water sample is calculated.

  According to the method for separating oil in water of the present invention, a method for separating oil in water that captures the oil in water in a solid aggregate having an extremely small amount of water is provided.

  Furthermore, according to the method for quantifying oil content in the oil-containing water of the present invention, on-site analysis can be performed in a field for trace amounts of oil contained in environmental water, etc. easily, quickly and accurately, at low cost and without secondary contamination. A novel method for quantifying oil content in oil-containing water is provided.

  Next, the best mode for carrying out the present invention will be described by way of examples.

  A certain amount of sewing oil was weighed, and water was added and dispersed to a total volume of 800 ml to prepare a stock solution. Next, this stock solution was diluted with water to obtain a sample having an oil content of 0 to 83 ppm. Next, 50 ml of each of these samples was dispensed into a bottle with a lid, and after adding 1.0 ml of 0.5 M HCl aqueous solution and mixing, poly (N-isopropylacrylamide) (mass average molecular weight of about 100,000, 1.0 ml of a 2.0 mass% aqueous solution having a transition temperature of 32 ° C. was added, and 4 ml of 4M-NaCl aqueous solution was further added and mixed.

  Next, the mixture thus obtained was heated at 55 ° C. for 1 to 3 minutes, and then vigorously shaken while maintaining the temperature to aggregate the precipitated solid. The oil was recovered from the aqueous phase by carefully separating the aqueous phase by decantation from the solids thus agglomerated. In this example, similar results were obtained when lubricating oil or paraffin oil was used instead of sewing machine oil.

  A certain amount of sesame oil was weighed, and water was added and dispersed until the total amount reached 800 ml to prepare a stock solution. Next, this stock solution was diluted with water to obtain a sample having an oil content of 0 to 83 ppm. Next, 50 ml of each of these samples was dispensed into a bottle with a lid, and after adding 1.0 ml of 0.5 M HCl aqueous solution and mixing, the same poly (N-isopropylacrylamide) used in Example 1 was used. 1.0 ml of an aqueous solution having a concentration of 2.0% by mass, and 4 ml of 4M-NaCl aqueous solution were added and mixed.

  Next, the mixture thus obtained was heated at 55 ° C. for 3 minutes, and then vigorously shaken while maintaining the temperature to aggregate the precipitated solid. The oil was recovered from the aqueous phase by carefully separating the aqueous phase by decantation from the solids thus agglomerated. In this example, similar results were obtained when salad oil, rapeseed oil, olive oil, safflower oil were used instead of sesame oil.

  To the solid content obtained in Example 1, 5 ml of water at 20 ° C. or lower was added and shaken to dissolve it, and the turbidity of the produced oil emulsion was measured as the absorbance at a wavelength of 660 nm. The results are shown in FIG. 2A as a graph showing the change in turbidity with respect to the sewing machine oil concentration. For reference, B is the result of measuring the turbidity of the sample before the concentration operation as it is, and the turbidity with respect to the oil concentration [not including poly (N-isopropylacrylamide)] expected to be obtained when concentrated. As C.

  As can be seen from this figure, when the sewing oil is concentrated 10 times, the turbidity A detected by the method of the present invention is obtained when the sewing oil having a concentration expected to be obtained when concentrated is dispersed in water. The value is larger than the turbidity C, and the sensitivity is increased 10 times or more. This indicates that poly (N-isopropylacrylamide) not only plays a role as an oil scavenger, but its aqueous solution contributes to the refinement and stabilization of emulsion particles as a dispersion medium. Yes.

  Using the solid content obtained in Example 2, this was dissolved in 10 ml of water at 20 ° C., and the relationship between the concentration of sesame oil and turbidity was determined in the same manner as in Example 3 and is shown as a graph in FIG. In the figure, A is a graph for a sample concentrated according to the present invention, B is a graph for a sample before the concentration operation, and C is an oil component having a concentration expected to be obtained when concentrated [poly (N-isopropylacrylamide)] It is a graph about what disperse | distributed.

  The effluent discharged from the sewage treatment plant in Kawasaki City, which is discharged under the Denenchofu weir in the downstream area of the Tama River that flows between Tokyo and Kanagawa Prefecture, is directly collected at the drain to the Tama River, and a known amount of oil is added to it. The measured data obtained by using the standard addition method is shown below. Furthermore, the measurement data which added the anionic surfactant sodium dodecylbenzenesulfonate (henceforth DBS) which is one of the most widely used surfactants are shown.

  That is, a certain amount of sewing oil or salad oil was weighed, and the actual sample was added and dispersed / dissolved until the total amount of the sewing oil was 800 ml and the total amount of the salad oil was 400 ml, thereby preparing the raw water of the oil-added actual sample. Next, the raw water of the oil-added real sample is diluted with a separate real sample, and an oil-added real sample having an oil content of 0 to 14.7 mg / liter for sewing oil and an oil content of 0 to 64 mg / liter for salad oil is obtained. Prepared.

  The quantitative operation was according to the same procedure as in Example 1. The results for the sewing machine oil thus obtained are shown in FIG. 4, and the results for the salad oil are shown in FIG.

  In these figures, graph A is a case where only oil is added, graph B is a case where oil and DBS 12 mg / liter are added, and graph C is a standard solution of oil concentration expected to be obtained when concentrated for comparison. The measurement results are shown.

  As can be seen from these figures, in the case of sewing oil (FIG. 4), the linear relationship between the added concentration and the turbidity of the sewing oil is almost the same as the calibration curve obtained with the standard solution not containing the actual sample. Is obtained. When DBS is further added to the sample water at 12 mg / liter, the measurement value is not affected when the sewing oil is 10 mg / liter or less, but a decrease of about 25% is observed at more than that.

  In the case of salad oil (FIG. 5), a result that is in good agreement with the calibration curve obtained with the standard solution is obtained between the concentration of added salad oil and the turbidity, regardless of whether DBS is added.

  In ordinary sewage and its treated water, most of the oil is considered to be vegetable oil, and the anionic surfactant coexists at a high concentration of 10 mg / liter or more in the inflow water and treated water to the sewage treatment plant. It is almost unthinkable to do. Therefore, based on the above results, this quantification method can be applied to most of the water that is obliged to measure oil content, such as environmental water and inflow water to sewage treatment plants and treated water. And linearity is maintained also in DBS coexistence (FIG. 4). Since the method of the present invention can also be applied to wastewater from a specific factory that uses mineral oil, it is suitable as a method for quickly monitoring oil in the field.

  The method of the present invention can be used for water purification and determination of oil content in water.

A kit suitable for use in the quantification method of the present invention. The graph which shows the change of the turbidity with respect to the oil concentration in Example 3. The graph which shows the change of the turbidity with respect to the oil concentration in Example 4. The graph which shows the change of the turbidity with respect to the density | concentration about the sewing machine oil in Example 5. FIG. The graph which shows the change of the turbidity with respect to the density | concentration about the salad oil in Example 5. FIG.

Explanation of symbols

1 Screw cap bottle made of polypropylene with lid 2,3,4,5 Screw cap bottle made of polypropylene 6,7,8 Polyethylene syringe 9,10 Polypropylene syringe 11 Polyethylene cup

Claims (4)

(A) A step of preparing an aqueous solution by adding a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than that temperature to an oil-containing water kept at a predetermined temperature and dissolving the same.
(B) The aqueous solution obtained in (a) is heated to a temperature higher than the transition temperature of the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound, and the solid of the thermosensitive polymer compound capturing the oil. And (c) a method for separating oil from water, the method comprising separating the solid from the aqueous phase. (A) a step of preparing a mixed solution by adding a low temperature hydrophilic-high temperature hydrophobic thermoreversible thermosensitive polymer compound having a transition temperature higher than the temperature to an oil-containing water kept at a predetermined temperature and dissolving it;
(B) The temperature of the mixed liquid obtained in (a) above the transition temperature of the low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound, and the solid of the thermosensitive polymer compound capturing the oil Forming a product,
(C) a step of separating the solid matter from the aqueous phase;
(D) a step of adding a predetermined amount of pure water to the solid obtained in (c) at a temperature lower than the transition temperature of the thermosensitive polymer compound to form an aqueous suspension of oil; And (e) a method for quantifying the oil content in the oil-containing water, comprising the step of calibrating the oil content in the aqueous suspension.   The method according to claim 1 or 2, wherein the oil-containing water in the step (i) is industrial wastewater containing mineral oil or animal and vegetable oil, inflow water to a sewage treatment plant, sewage treatment plant treatment water, river water, lake water, or seawater. . (B) Low-temperature hydrophilic-high-temperature hydrophobic thermoreversible thermosensitive polymer compound added in the step is Nn-propylacrylamide, N-isopropylacrylamide, N-cyclopropylacrylamide, N, N-ethylmethylacrylamide, N , N-diethylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine and a corresponding methacrylamide derivative, a polymer or copolymer of at least one monomer, or a monomer thereof. The method according to claim 1, 2 or 3, which is a copolymer of a monomer and other hydrophilic monomer or hydrophobic monomer.

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