JPH0534041B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention is a method for separating and removing oil by electrolysis from emulsified oil waste water containing oil such as cutting oil, rolling oil, degreased oil, etc. in an emulsified state. [Prior Art] Oil-containing wastewater discharged from machinery, metal processing factories, etc. contains cutting oil, rolling oil, etc. Since such oil-containing wastewater is highly emulsified by an emulsifier, it has been extremely difficult to separate and remove the oil by conventional methods such as oil-water separation, activated sludge treatment, and adsorption treatment. In addition, machinery, metal processing factories, etc. are industries that do not use water, and the absolute amount of wastewater is small, so we cannot expect any effect of diluting emulsified oil wastewater with other wastewater, and urgent measures are needed to prevent emulsified oil wastewater. It was requested. The reason why it is difficult to treat emulsified oil wastewater is that the oil in the wastewater is emulsified and dispersed by an emulsifier, and most of the oil particles are less than 10μ and remain extremely stable, so the oil does not separate from the aqueous phase. It's for a reason. Therefore, it cannot be treated by ordinary physical means such as oil/water separation or adsorption treatment. In addition, although it is possible in principle to destroy the emulsified state using chemicals, there are problems with secondary treatment of the added chemicals, and the composition of emulsified oil wastewater is complex, making the conditions for selecting chemicals complicated. It is extremely difficult to realize this for several reasons. Furthermore, methods using only electrode reactions do not generate secondary products and can provide good treatment results, but they have the problem of requiring a long time for treatment and consuming a large amount of power. [Object of the Invention] The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to provide a method that can effectively separate and remove oil in a short time with less electric power. be. [Structure of the Invention] The method for treating emulsified oil wastewater of the present invention that achieves the above object includes placing emulsified oil wastewater between electrodes, mixing an additive made of a poorly soluble polyvalent metal compound with the emulsified oil wastewater, and then The present invention is characterized in that electricity is applied between the electrodes to separate and remove oil in the emulsified oil waste water. In the present invention, the oil forming the emulsified oil wastewater to be subjected to electrolytic treatment may be of any type, and oil in an emulsified state, including the above-mentioned cutting oil, rolling oil, etc., can be treated. . In the method of the present invention, emulsified oil waste water is placed in an electrolytic tank equipped with electrodes, and an additive consisting of a poorly soluble polyvalent metal compound is added thereto, and in a well-dispersed state, emulsified oil waste water is placed in an electrolytic tank equipped with an electrode. This is done by passing electricity between them. In the method of the present invention, any insoluble conductor can be used as the electrode, but it is preferable to use an anode with a high oxygen overvoltage, such as platinum, lead dioxide (PbO ₂ ), carbon, ferrite, etc. is preferred. Also, effective additives used here include poorly soluble compounds such as oxides, hydroxides, and silicides of polyvalent metals selected from calcium, magnesium, aluminum, and zinc. The particle size of the additive varies depending on the type, but is generally 0.005 to 3 mm, preferably 0.01 to 0.5 mm.
mm, and the amount added is 0.005 to 5 mm in wastewater 1.
g, preferably 0.05 to 0.5 g. In practice, these additives are added to emulsified oil wastewater, stirred to form a suspension, and then electrolyzed for a certain period of time. When the treated water is allowed to stand after electrolysis, the oil that has reacted with some of the additives is removed. It becomes scum and floats to the surface of the water and separates.
This scum can be easily removed by simply scraping the water surface, and has good dehydration and filtration properties. In addition, since unreacted additives settle to the bottom, they can be reused after separation. Furthermore, there is no wear of the anode or adhesion of electrolytic products, and stable continuous operation for long periods of time is possible. The electrolytic treatment temperature is usually
The temperature is room temperature to 60°C, and the electrolytic voltage is usually 5 to 20 volts. Further, the oil concentration in the emulsified oil wastewater is not particularly limited, but is generally about 100 to 5000 ppm. [Effects of the Invention] Unlike conventional wastewater treatment methods, the method of the present invention separates and removes oil by integrating electrolytic oxidation, coagulation action by additive ions, flotation action by generated gas, etc. In other words, under the surface activity of the emulsifier caused by electrolytic oxidation, the aggregation effect of polyvalent metal ions eluted by electrolytic oxidation of additives, and the flotation and separation effect of oil by oxygen gas and hydrogen gas generated by electrolysis are integrated. A synergistic effect can be exerted to efficiently separate oil from emulsified oil wastewater. 1/10 to 1/10 compared to electrolytic oxidation alone
A removal rate of the same level or higher is achieved with 0.00 processing time or power. Furthermore, compared to treatment using only additives, the removal rate is several times higher. Further, according to the method of the present invention, the above-mentioned effects are combined, so the type of emulsifier,
It can be carried out regardless of the type of oil content.
Further, according to the present invention, the scum containing oil produced by the treatment has good filterability and dehydration properties and can be easily separated and removed. Further, when the stirring is stopped after the reaction, the additive will precipitate at the bottom, so it can be recovered and reused. Furthermore, since the processing capacity can be freely controlled by voltage and current,
Even if the amount of wastewater or the oil content in the wastewater changes during the treatment, it can be easily handled so that the treatment meets the preset standards. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Diluted with water to give an emulsified oil concentration of 0.2g/
Use JIS Class 1 No. 1 water-soluble cutting oil as emulsified oil drainage, put 100ml of it into an electrolytic tank, and use it as an additive.
Added 50 mg of CaSi ₂ powder (less than 64 mesh).
As electrodes, platinum plates measuring 2 cm x 2 cm were used for both the anode and cathode, and a direct current of 0.2 A was applied while stirring.
Electrolytic treatment was performed for 2 hours. The electrolysis voltage was 19.8-16V. The electrolyte, which was initially emulsified, gradually becomes more transparent through the electrolytic treatment, and when stirring is stopped after the reaction is complete, the oil-containing scum immediately floats to the surface of the electrolyte, and the unreacted additives lose their specific gravity. Since it was large, it settled and separated at the bottom, and the electrolyte became completely colorless and transparent. As a result, the amount of total organic carbon (hereinafter referred to as TOC), which corresponds to all organic substances such as oil and surfactants in water-soluble cutting oil, increased from 159 ppm before electrolysis to 19.4 ppm after 2 hours of electrolysis treatment, and its removal rate was 87.8%. The scum generated by this process is mostly oil and contains some hydroxides such as Ca, but most of it can be separated and removed by scraping the surface of the electrolyte. ,
Further, by performing ordinary separation operations such as filtration, it was possible to easily and completely separate and remove the oil. Furthermore, the additives that had settled and separated at the bottom could be recovered and reused, and the electrodes could be used continuously for electrolytic treatment without any substances that would inhibit electrode reactions attached to them. In addition, when the same sample was electrolyzed for 2 hours under the same conditions without adding any additives,
The TOC removal rate was 28.2%, and when treated by adding additives and stirring for 2 hours without applying electricity,
The TOC removal rate was 36.0%, which does not provide a sufficient treatment effect. Example 2 The same sample was electrolyzed for 2 hours under the same conditions as in Example 1, except that the anode was replaced with lead dioxide and the cathode was replaced with a stainless steel plate. As a result, the TOC was 159 ppm before electrolysis, and after 2 hours of electrolysis treatment.
The removal rate was 22.1 ppm, and the removal rate was 86.1%, and almost the same treatment results as in Example 1 were obtained. The overall reaction situation, such as oil separation and electrolyte transparency, was almost the same as in Example 1, and the electrolysis voltage was 16.3~
It was 12V. Example 3 Table 1 summarizes the results of electrolytic treatment of the same sample as in Example 1 using different additives and electrodes. Sample: JIS Class 1 No. 1 water-soluble cutting oil 0.2g/,
TOC159ppm Processing amount: 100ml Additive amount: 50mg Electrode area: 2cm x 2cm Current: 0.2A Electrolysis time: 2 hours

[Table] As shown in Table 1 above, when CaSi ₂ and MgSiFe are used as additives, there is almost no difference in treatment effect due to the difference between platinum and lead dioxide electrodes.
When AlSi was used as an additive, the lead dioxide electrode had a slightly better treatment effect. Other general reaction conditions such as generation of scum, oil separation, and sedimentation of unreacted additives were almost the same as in Example 1, and oil could be effectively separated and removed. Example 4 Diluted with water to give emulsified oil concentration of 1.0g/
JIS Class 1 No. 1 water-soluble cutting oil was used as emulsified oil waste water, 100 ml of which was placed in an electrolytic bath, and 5 mg or 10 mg of magnesium oxide (MgO) powder was added as an additive. Using platinum plates as electrodes for both the anode and cathode, a direct current of 0.2 A was applied while stirring the electrolytic solution, and electrolytic treatment was performed for 10 to 30 minutes. The results are shown in Table 2. Sample: JIS Class 1 No. 1 water-soluble cutting oil 1.0g/,
TOC867ppm Processing amount: 100ml Additive: Magnesium oxide (MgO) Electrode: Platinum plate electrode area for both anode and cathode: 2cm x 2cm Current: 0.2A

【table】

[Table] Shows the results.
As shown in Table 2 above, when MgO was used as an additive, oil could be sufficiently separated and removed with an addition amount of 5 mg and an electrolysis time of 10 minutes. When stirring is stopped after the reaction is complete, the scum containing oil floats to the surface of the electrolyte and unreacted MgO settles, but the separation is more incomplete than when using silicide, so normal filtration etc. It is necessary to perform a separation operation. The dewaterability of the scum and the like was good, and the oil content could be easily separated and removed by filtration.

Claims (1)

[Claims] 1 Emulsified oil wastewater is placed between the electrodes, and a sparingly soluble polyvalent metal compound consisting of an oxide, hydroxide or silicide of a polyvalent metal selected from calcium, magnesium, aluminum and zinc is added to the emulsified oil wastewater. A method for treating emulsified oil wastewater, which comprises adding powder at a rate of 0.005 to 5 g per powder, and then applying electricity between the electrodes to separate and remove oil in the emulsified oil wastewater.