JP2007105665A - Treating method of water-soluble processing oil waste solution and treating apparatus of water-soluble processing oil waste solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemically treating method of a water-soluble processing oil waste solution by which treatment of high efficiency can be performed by using a compact apparatus with small electric energy consumption and to provide a treating apparatus for performing this treating method. <P>SOLUTION: In this treating method of the water-soluble processing oil waste solution, the water-soluble processing oil waste solution is made to turn into a state where oil/water separation can be performed by electrolytic treatment using electrically conductive diamond at least at an anode and then is subjected to oil/water separation. The treating apparatus for performing this treating method is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for efficiently treating a waste liquid of a water-soluble processing oil used for machining or the like by an electrochemical method, and a water-soluble processing oil waste liquid treatment apparatus used for carrying out the method. .

  In the machining of metals and ceramics, a processing oil is used for the purpose of reducing frictional heat generated between a workpiece and a tool and preventing chip welding. By using the processing oil, it is possible to improve the tool life and suppress the variation in the workpiece size.

  Most of this processing oil is treated as industrial waste after use. This treatment has a very large environmental load, and in view of recent trends that place importance on environmental problems, a treatment method with a small waste environmental impact is desired.

  As processing methods for processing oil as industrial waste, usually, (1) physical methods such as sedimentation, flotation, filtration, and centrifugation, (2) coagulation sedimentation, redox, neutralization, adsorption, ion exchange, dialysis, etc. (3) Biochemical methods such as activated sludge and microbial treatment, (4) In addition, incineration, drying, etc. are used. However, (1) physical methods and (3) biochemical methods require a large amount of processing equipment, (2) the physicochemical methods are inefficient, and (4) incineration has a high environmental impact. is there. In the case of a water-soluble processing oil, since it is diluted with water and used, it is desired to separate it from water during the treatment of the waste liquid. (3) In the biochemical method, the oil and water are separated. There is a problem that it is impossible to remove the oil component by separating them.

  Japanese Patent Laid-Open No. 2005-21744 (Patent Document 1) proposes a method for decomposing hydrophobic organic substances such as oil by a compact apparatus by an electrochemical method. This method is characterized in that diamond having a strong oxidizing power is used for the anode and the oil is oxidatively decomposed. However, in this method, processing is performed with a large current density, and as a result, the life of the electrode is shortened, and problems such as inefficiency due to the use of electric energy for electrolysis of water that is originally unnecessary occur.

Therefore, there has been a demand for a method of electrochemically treating a waste liquid of processing oil, which uses a compact device and enables high-efficiency treatment with small electric energy.
JP 2005-21744 A

  The present invention provides a method for treating a waste liquid of a water-soluble processing oil by an electrochemical method, which uses a compact device and enables high-efficiency treatment with small electric energy. Is an issue. The present invention also provides a processing apparatus for performing this processing method.

  As a result of the study, the present inventors have found that a water-soluble processing oil waste liquid can be efficiently treated by combining electrolytic treatment (electrochemical method) using at least conductive diamond for the anode and oil-water separation. . More specifically, by this electrolytic treatment, it is possible to make the water-soluble processing oil waste liquid separable into oil-water-separable state without requiring a large current density. The present inventors have found that the processing oil waste liquid can be efficiently processed and the above-mentioned problems can be achieved, and the present invention has been completed.

  The present invention described in claim 1 is characterized in that the water-soluble processing oil waste liquid is made into a state in which oil-water separation is possible by electrolytic treatment using conductive diamond at least as an anode, and then subjected to oil-water separation treatment. It is a processing method of a processing fluid waste liquid.

  Here, the water-soluble processing oil agent is a processing oil agent which is made water-soluble by adding a surfactant, and is usually diluted with water and used. The water-soluble processing oil used for metal processing or the like mainly comprises an oil component that does not dissolve in water such as mineral oil or fatty acid oil, and a surfactant such as an emulsifier. This surfactant makes the oil hydrophilic and enables mixing of the oil and water. On the other hand, the water-soluble processing oil used after diluting in water is difficult to process because it does not separate the oil from water. It has become.

  As described above, in the treatment method of the present invention, first, the waste liquid, which is a water-soluble processing oil diluted in water, is made oil-water-separable by electrolytic treatment using a conductive diamond electrode as the anode. It is considered that the surfactant, which is an organic substance in the water-soluble processing oil, is preferentially decomposed by the electrolytic treatment, the hydrophilicity of the oil is lost, and the oil / water can be separated.

  At this stage, the oil in the waste liquid is not decomposed. That is, in the method of the present invention, the surfactant in the waste liquid is decomposed preferentially, and no oil decomposition is necessary (oil is removed by oil-water separation). When the oil component is decomposed, a large current density is required, but in the method of the present invention, no oil component decomposition is necessary, so a large current density is not necessary, and as a result, without shortening the life of the electrode, In addition, electric energy used for electrolysis of water is small, and highly efficient electrolytic treatment can be performed.

  In addition, when water-soluble processing oil waste liquid is processed by conventional processing methods such as physical methods and physicochemical methods, the waste liquid cannot be sufficiently detoxified even if a large-scale processing facility is used. Therefore, incineration disposal that is not an environmentally good method was necessary. According to the treatment method of the present invention, it is possible to efficiently treat a water-soluble processing oil waste liquid that has been very difficult to treat with a compact treatment apparatus.

  The electrolytic treatment in the treatment method of the present invention is characterized in that conductive diamond is used at least for the anode. Conductive diamond has a high oxygen generation potential compared to common anode materials such as platinum, ruthenium oxide, iridium oxide, etc., so it does not decompose water, and it does not decompose organic substances (surfactants) in water. It can be efficiently oxidized and decomposed.

The electrolytic treatment is preferably performed at a current density of about 1 to 100 mA / cm ² . When performing the electrolytic treatment, it is preferable to add an electrolyte in order to promote the electrolytic reaction. As the electrolyte, sulfate ions such as sodium sulfate and calcium sulfate, and chloride ions such as sodium chloride and potassium chloride can be added. The concentration of the electrolyte is not particularly limited, but if the concentration is extremely low, the electrical resistance of the treatment liquid increases and the electrical efficiency deteriorates.

  By the electrolytic treatment, the surfactant in the treatment waste liquid is decomposed and removed, and the effect of the surfactant that has been made hydrophilic by mixing the oil with water is lost. As a result, the oil and water can be separated. . In the treatment method of the present invention, after this electrolytic treatment, the oil is not electrolyzed and is removed from the waste liquid by oil-water separation treatment.

  The oil / water separation treatment can be easily performed by utilizing the difference in specific gravity and the difference in surface tension between water and oil. The separated oil can be recovered and incinerated or reused, and moisture can be discharged with reduced environmental burden because substances such as oil that are harmful to the environment have been removed.

  The electrolytic treatment and the oil / water separation treatment can be performed in one circulation path in which the water-soluble processing oil waste liquid is circulated. In many cases, it is difficult to make all of the oil in the water-soluble processing oil waste liquid into a state in which oil and water can be separated by only one electrolytic treatment. Surfactant is decomposed and removed, the oil is gradually separated, and most of the oil in the water-soluble processing oil waste liquid can be removed by repeating the circulation. Claim 2 corresponds to this aspect.

  Instead of the above-described embodiment, only the electrolytic treatment is performed in the circulation path, and the circulation of the water-soluble processing oil waste liquid surfactant is almost completely decomposed and removed, and then the oil-water separator provided outside the circulation path. The method of performing an oil-water separation treatment by the method is also mentioned. Claim 3 corresponds to this aspect.

  In addition to the above-described treatment method, the present invention has an electrolytic treatment device and an oil-water separator that use conductive diamond at least as an anode as a device for performing this treatment method. (Claim 4).

  Since both the electrolytic treatment apparatus and the oil / water separator can use a compact apparatus, the treatment apparatus of the present invention can also be made compact.

  As described above, it is often difficult to make all the oil content in the water-soluble processing oil waste liquid into a state where oil and water can be separated by only one electrolytic treatment. Therefore, the water-soluble processing oil waste liquid is circulated and electrolyzed. Therefore, an electrolytic treatment apparatus may be provided in the circulation path. Also, the oil / water separator may be provided in the same circulation path as the electrolytic treatment apparatus, or may be provided outside the circulation path.

  By installing the water-soluble processing oil waste liquid treatment device of the present invention in a machining device such as a lathe, a machining center, or a grinding machine, the environmental load of the water-soluble processing oil waste liquid generated by the use for machining is greatly reduced. can do.

  According to the method of the present invention, conventionally, the waste liquid of water-soluble processing oil that has been very difficult to treat can be detoxified with a compact device by electrolytic treatment by an electrochemical method, and the waste liquid is discharged. Can greatly reduce the environmental load. Further, the electrolytic treatment can be performed with a small electric energy and does not require a large current density, so that the treatment can be performed with high efficiency without shortening the life of the electrode.

  The processing apparatus of the present invention can be a compact apparatus, and the processing method having the above-described excellent features can be easily performed using this apparatus.

  Next, a more specific form of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view schematically showing an example of the processing apparatus of the present invention. In FIG. 1, reference numeral 1 denotes an electrolytic treatment apparatus, and a conductive diamond electrode is attached to the anode 2. As the cathode 3, a general metal electrode can be used. In this case, scale may be deposited during operation, and the electrolytic reaction may not proceed. This problem can be prevented by reversing the anode and the cathode. However, when a general metal electrode is inverted to the anode, the electrode is eluted, so it is preferable to use a diamond electrode for the cathode. .

  As the conductive diamond electrode mounted on the anode 2, a semiconductor silicon, a metal such as Nb, Ta or Ti is used as a substrate, a hydrocarbon gas such as methane and hydrogen as raw materials, a hot filament CVD method or a microwave plasma CVD. Examples thereof include those synthesized on the substrate by the above method, or those obtained by attaching particulate diamond to a metal such as Nb, Ta, or Ti. The synthesis of particulate diamond can be performed by a method of converting graphite through a metal solvent under an ultrahigh pressure and a high temperature.

  In the CVD method, when diamond is synthesized, conductivity can be imparted to the diamond by mixing a small amount of a gas containing boron such as diborane with the source gas. In the case of particulate diamond, electrical conductivity can be imparted by adding boron to one or both of the metal solvent and the raw material graphite during synthesis.

  If the amount of boron in the diamond is too small, the electrical conductivity of the diamond is low and the loss of electrical energy due to resistance is large, which is not practical. Since the electrical resistance of diamond can be reduced if the amount of boron is large, it is preferable as electrical efficiency, but there is a limit amount for maintaining the crystallinity of diamond. As a specific addition amount, 100 ppm to 10,000 ppm is suitable.

  In the water-soluble processing oil waste liquid treatment apparatus of FIG. 1, the water-soluble processing oil waste liquid is stored in the waste liquid tank 4. It is preferable to remove insoluble substances such as metal powder and processing waste in advance from the water-soluble processing oil waste liquid. Therefore, preferably, the water-soluble processing oil waste liquid treatment apparatus has means for removing insoluble substances such as metal powder and processing waste, for example, filtering means, but this means is not shown in FIG. .

  In the water-soluble processing oil waste liquid treatment apparatus of FIG. 1, the water-soluble processing oil waste liquid stored in the waste liquid tank 4 is first sent to the electrolytic treatment apparatus 1 by the pump 6 and between the anode 2 and the cathode 3 of the electrolytic treatment apparatus 1. The waste liquid passes through the electrolytic treatment. The electrolyzed waste liquid is in a state in which oil and water can be separated, and the oil is separated and recovered by the oil and water separator 7. The treatment liquid from which the oil has been separated and recovered is returned to the waste liquid tank 4, but since the oil is removed from this treatment liquid, the oil content of the water-soluble processing oil waste liquid in the waste liquid tank 4 is added by adding this treatment liquid. The amount drops.

  In the water-soluble processing oil waste liquid treatment device of FIG. 1, the electrolytic treatment device 1 and the oil / water separation device 7 are provided in one circulation path 5. Therefore, the electrolytic treatment and the oil / water separation treatment are performed in one circulation path. In many cases, it is difficult to make all the oil components in the waste liquid separable by simply passing the water-soluble processing oil waste liquid through the electrolytic treatment apparatus 1 once. However, the circulation as described above is repeated. Thus, the surfactant in the waste liquid is gradually decomposed and removed, and the oil is gradually separated, so that most of the oil in the water-soluble processing oil waste liquid can be removed.

  In the example of FIG. 1, the oil / water separator 7 is installed in the middle of the circulation path 5, but the oil / water separator 7 may be provided in the waste liquid tank 4. In this case, the surfactant in the waste liquid is gradually decomposed and removed by repeating the circulation of the waste liquid tank 4, the pump 6, and the electrolytic treatment apparatus 1. Then, after the surfactant of the water-soluble processing oil waste liquid in the waste liquid tank 4 is almost completely decomposed and removed, the oil component can be separated and removed by the oil / water separator provided in the waste liquid tank 4.

  The waste liquid (treatment liquid) from which the oil has been separated and removed in this manner does not contain environmentally hazardous substances such as organic substances, and is a wastewater that has a low environmental load.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, the scope of the present invention is not limited by this Example.

Two boron-added CVD diamond plates (size: 5 cm × 5 cm × 0.32 cm) synthesized on a conductive Si substrate having a thickness of 3 mm were immersed in 500 ml of sample water placed in a glass beaker having a capacity of 700 ml. The distance between the two diamond plates was 1 cm, and connected to the respective DC power sources to form an anode and a cathode. The sample water was obtained by diluting a stock solution of a water-soluble cutting fluid (trade name: Cosmo Clean Cool) to 1/100 with pure water, and sodium sulfate was added as an electrolyte at a rate of 0.1 mol / L. While stirring the solution in the beaker with a stirrer, a current having a current density of 0.1 A / cm ² was passed between the conductive diamond plates. After 8 hours and 20 hours of electrolysis, the sample water in the beaker was in an oily state. The sample water (separated sample water) after separating and removing the oil was analyzed for chemical oxygen demand (COD) and the amount of normal hexane extract.

(Comparative example)
The electrolytic treatment was performed in the same manner as in the example except that two platinum plates (size: 5 cm × 5 cm × 0.2 cm) were used instead of the boron-added CVD diamond plate. No particular change was observed in the sample water of the beaker after 8 hours of electrolysis, and the oil content could not be separated. This sample water (treated sample water) was also analyzed for chemical oxygen demand (COD) and the amount of normal hexane extract.

  Table 1 shows the results of analyzing the treated sample water (Example) subjected to electrolytic treatment using a boron-added CVD diamond plate and the treated sample water (Comparative Example) treated electrolytically using a platinum plate. From this table, it was confirmed that the water-soluble processing oil waste liquid was effectively treated by the method of the present invention.

It is a schematic diagram which shows an example of the water-soluble processing oil agent waste liquid processing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolytic processing apparatus 2 Anode 3 Cathode 4 Waste liquid tank 5 Circulation path 6 Pump 7 Oil-water separator

Claims (4)

  A method for treating a water-soluble processing oil waste liquid, wherein the water-soluble processing oil waste liquid is made into a state in which oil-water separation is possible by electrolytic treatment using conductive diamond at least as an anode, and thereafter oil-water separation treatment is performed.   2. The method for treating a water-soluble processing oil waste liquid according to claim 1, wherein the electrolytic treatment and the oil-water separation treatment are performed in one circulation path in which the water-soluble processing oil waste liquid is circulated.   The oil / water separation treatment is performed by an oil / water separator provided outside the circulation path after the electrolytic treatment is performed in a circulation path in which the water-soluble processing oil waste liquid is circulated. Of water-soluble processing oil waste liquid. A water-soluble processing oil waste liquid treatment device comprising an electrolytic treatment device and an oil-water separator using conductive diamond at least for an anode.

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