JPH0722650B2 - Oil-water separation method for emulsified oil wastewater containing nonionic surfactant - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention is to add a small amount of a special additive from an emulsified oil-containing wastewater in which oil and fat are highly emulsified by a nonionic surfactant. The present invention relates to a method for separating and removing oil by the electrolytic method.

[Prior art]

Nonionic surfactants are stable in the dispersion and emulsifying power of organic substances such as fats and oils, coloring materials, etc. even in water quality containing salts such as alkaline earth metals, low foaming property, and water rinsability. It has good properties and does not corrode the metal surface due to its non-ionic nature. Therefore, it has excellent performance as an emulsifying cleaning agent for oils and greases, so it has recently been used as a cleaning agent for machines and metal materials. In addition, it is widely used as a machine cleaning agent in ships where it is difficult to obtain good water quality. Further, since it is less irritating to the skin, it has come to be used in a wide range of applications as a general-purpose general-purpose detergent.

While the nonionic surfactant has the above-mentioned advantages, oil-containing wastewater containing an oil component emulsified and dispersed by the nonionic surfactant is extremely difficult to separate oil / water by a conventional method. That is, the oil content in the waste water is highly emulsified by the strong emulsifying power, and in many cases the oil droplet size is made finer to 1 μm or less, so that oil-water separation based on gravity separation cannot be expected at all.

Furthermore, these fine oil droplets bind to the nonionic surfactant and are stabilized by the hydration layer, so unlike the ionic surfactant which is stabilized by the repulsive force of the same kind of ions, the interionic reaction is prevented. Almost no reaction with the basic aluminum, iron, or calcium-based flocculant, and the application of the usual flocculation treatment is impossible. Furthermore, it has not been possible to purify by an electrolytic treatment method using a soluble electrode, which is extremely effective in treating emulsified oil wastewater containing an anionic surfactant.

Therefore, the emulsified oil wastewater emulsified by the nonionic surfactant is adsorbed in a multi-stage adsorption filtration by one or various adsorbent layers using activated carbon, modified synthetic resin adsorbent, organic-inorganic composite adsorbent. The only treatment measure is to remove it by adsorption, but in general, the adsorption efficiency of these adsorbents is not high, and since the adsorption capacity is not large, it cannot be applied to anything other than dilute drainage, and the adsorbent layer Since it has drawbacks such as need for frequent replacement, it is only a secondary method, and a radical treatment method in this field is currently desired.

There are many types of nonionic surfactants, but each is an ether or ester bond product of a hydrophobic part and a hydrophilic part. The hydrophobic part is mainly higher alcohols,
Consists of alkylphenol, higher fatty acid, higher amine, hydrophilic part is polyethylene glycol, glycerin, sorbitan, industrially most used type is alkylphenol and ether bond type of ethylene oxide or propylene oxide, or higher fatty acid It is of the ester bond type of polyethylene glycol. Others are used for special purposes such as food or medicine. The most frequently used alkylphenol is the nonylphenyl type, and the higher fatty acid has 12 to 18 carbon atoms. The number of added moles of polyethylene glycol can be freely adjusted in relation to HLB, but usually 10-20
Those with a degree (about 9.2 to 15.5 for HLB) are widely used.

These alkylphenol-ethylene oxide-bonded or higher fatty acid-polyethylene glycol-bonded nonionic surfactants are extremely stable because they do not have an ionic group or a reactive group, and ordinary flocculation treatment is impossible.
Irradiation for several hours is also required by the ultraviolet-oxidizing method, which is not practical. That is because the ether bond of the polyethylene glycol group is scientifically extremely stable, and in water the ether bond is hydrated by a hydrogen bond,
This is probably because it is a stable aqueous solution. Therefore, it is possible to use the so-called cloud point that reduces hydration by heating and insolubilizes the surfactant, but the cloud point of a high HLB (10 or more) surfactant used in emulsified oil is usually 60 ° C or more. Yes, it is virtually impossible to heat large volumes of wastewater.

As described above, it has been virtually impossible by the conventional method to destroy the surface activity of the nonionic surfactant by the physicochemical means to separate the emulsified oil from water. Further, even with the biological treatment method, the decomposition of the ether bond is difficult, so that the biodegradation of the nonionic surfactant containing polyethylene glycol having a large number of ether bonds is virtually impossible.

[Structure of Invention]

The present inventors have conducted diligent research on practical treatment technology of emulsified oil wastewater containing nonionic surfactants of alkylphenyl and ethylene oxide bonding type, or higher fatty acid and polyethylene glycol bonding type, and as a result, certain substances are specific. It was found that the above method was effective, and the method for treating the above wastewater was established.

That is, in an electrolytic treatment method using a soluble electrode such as aluminum, the following specifically effective substance as an oil-water separating agent is added to the electrolytic solution, and then electrolysis is performed to emulsify the nonionic surfactant. We have developed a method that allows oil wastewater to be treated in the same way as emulsified oil wastewater using an anionic surfactant.

The specific properties are roughly divided into three groups, the first group of which is hydroxybenzene sulfonic acid,
It is composed of salicylic acid, abietic acid, and saponin.

Although the mechanism of action between these substances and the above nonionic surfactants has not been sufficiently clarified, it forms a kind of complex with the above nonionic surfactants, and as a whole, from nonionic to anionic. As a result, the agglomeration can be achieved by an electrolytic method using a soluble electrode such as aluminum.

The second group is polyacrylic acid, nitrohumic acid,
It is composed of a water-soluble salt of thiolignin, polyvinyl alcohol, polyvinyl methyl ether, and polyvinylpyrrolidone.

The interaction between these substances and nonionic surfactants is not yet clear, but for example, in the case of polyacrylic acid, it is known to form a water-soluble aggregate with high molecular weight polyethylene oxide. Therefore, it is considered that the polyethylene glycol residue, which is a low-molecular-weight polyethylene oxide, also forms some association with polyacrylic acid, and this association is generated by the aluminum ion generated in the electrolysis by the aluminum electrode as in the first group. It is considered to be aggregated. The above-mentioned other high components also generate aggregates by a substantially similar mechanism,
It is considered that this is aggregated by aluminum ions. Unlike other substances, nitrohumic acid is not linear, but since it has a large number of carboxylic acid or sulfonic acid groups and phenolic hydroxyl groups in the molecule, it simultaneously forms the same complex as the first group. It is thought to be done.

The third group are anionic surfactants. Substances belonging to this group include higher fatty acid soap-based compounds, alkylbezene sulfonic acid-based compounds, and sulfuric acid ester-based compounds of higher alcohols, which are commonly used as anionic surfactants.

When these anionic surfactants are added to emulsified oils emulsified with nonionic surfactants, the nonionic surfactants that were bound to the oil component are replaced with anionic surfactants, resulting in It is considered that the emulsified oil can be changed by using an anionic surfactant and can be processed by the electrolytic method using an aluminum electrode. Particularly effective ones in this group are sodium salts of dodecylbenzenesulfonic acid and dodecylsulfate, and soaps of higher fatty acids are slightly less effective.

The substances of the three types of groups can be effectively used alone, but they can be used in combination with each other to obtain a synergistic effect. For example, by using the first group and the second group together, it is possible to further enhance the oil-water separation effect as compared with the second group alone, and
The electrolysis time can be shortened as compared with the first group alone. Further, a similar electrolysis promoting effect is recognized by the combined use of the first group and the third group. Also second
The same effect can be expected by using the third group together with the third group. The order of addition at the time of use does not particularly affect, but it is generally more effective to add the high molecular weight substance first and then add the low molecular weight substance. For example, the method of adding the first group after adding the second group, and the method of adding the third group after adding the third group often give favorable results. Furthermore, the same effect can be expected by adding all of the first, second, and third groups.

Further, in the case of the above electrolytic treatment, the supply amount of aluminum ions necessary for the electrolysis of the emulsified oil by the nonionic surfactant, that is, the electrolysis time, is the electrolytic treatment of the emulsified oil containing almost the same amount of anionic surfactant. A little more than in the case of.
This is because the complex or association of the above groups with the nonionic surfactant is weaker in anionic property than the anionic surfactant, and therefore, weaker in reactivity with the aluminum ion, so that a larger amount of It is considered that this is because it is necessary to supply aluminum ions.

Further, if the pH of the emulsified oil is high, it becomes difficult to form a complex or an aggregate. Therefore, it is preferable that the emulsified oil is neutral or weakly acidic, avoiding alkalinity during the treatment. Furthermore, the formation of flocs of watercolorized aluminum is an essential condition for the treatment of emulsified oils with aluminum ions, and if alkaline, the formation of aluminates causes the formation of flocs, which makes it difficult to produce flocs. In the case of the electrolysis method using an aluminum electrode, the alkaline solution approaches neutral due to the elution of aluminum ions that are amphoteric electrolytes, and the acidic solution also tends to neutralize, so adjustment of PH is not essential, but It is economically inconvenient to utilize electrolysis for the neutralization itself, so that it is preferable to neutralize in advance when the solution is alkaline.

The method of the present invention, the specific substance as an oil-water separator is added to the emulsified oil drainage alone or in admixture, and after sufficient mixing and dissolution, as in the case of ordinary electrolytic treatment, as an electrode. It is performed by energizing using a soluble electrode.

In this case, the addition amount of the oil / water separating agent depends on the type of the oil / water separating agent,
Depending on the oil content in the wastewater and the concentration of nonionic surfactant, etc., usually several ppm per emulsified oil concentration of 1,000 ppm
It is suitable to be in the range of several tens of ppm, and addition of an excessive amount may rather diminish the effect. Especially the second
It is preferable to use the polymers belonging to the above group in an amount of about 10 ppm or less.

Aluminum or iron can be used as the soluble electrode, but in the case of iron, the valence of the eluted ions is divalent, so it is necessary to oxidize this to make it trivalent. It is preferable to use an aluminum-based electrode to be supplied. As the cathode, any kind of conductive material can be used.

The electrolyte should always be agitated during electrolysis, and mechanical agitation or bubble agitation can usually be used.

Further, the main purpose of the electrolysis in the case of using a soluble electrode is to supply ions, and since the Faraday's law is followed, the strength of current and voltage can be arbitrarily selected. In this case, if the resistance of the electrolyte is large, current is consumed to heat the solution, so the conductivity of the electrolyte is preferably 1 mS / cm or more, and when the conductivity of the drainage is lower than that, salt is used as the supporting electrolyte. It is necessary to add an alkali metal salt such as.

Furthermore, the oil content concentration in the emulsified oil wastewater is not particularly limited, but if it is 10,000 ppm or more, the electrolytic effect may decrease, and it is generally preferable that it is in the range of 100 to 1,000 ppm.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 An anode obtained by twisting aluminum wires in a circumferential shape is inserted into an electrolytic cell having a capacity of 1, and a lead wire is covered with insulating silicon rubber. Insert the ball-shaped G3 glass filter together with the lead wire, and generate bubbles through pressurized air. Further, a stainless wire mesh is used for the cathode, and an agitator is put in the circumference of the aluminum wire so that the magnetic stirrer can be agitated.

A sample was prepared by using kerosene containing about 25% nonionic surfactant as a main ingredient, and diluting a commercially available emulsion detergent 1,000 times with water as model drainage. Further, salt was added as a supporting electrolyte at a concentration of 1,000 ppm. The conductivity of sample water is 20
It was about 1.7 mS / cm at ℃.

Model drainage of 0.8 was put in the above electrolytic cell, an oil-water separating agent was added and dissolved, and then electrolysis was performed by adding a constant current direct current of 0.12 or 0.2 A. The electrolytic solution was collected with time, filtered with a paper filter, and the absorbance at 400 nm was measured using a 10 mm square quartz cell to follow the progress of electrolysis. The absorbance of the original model wastewater is usually around 1.3. The total organic carbon (TOC) is 512ppm
Met.

When sodium hydroxybenzene sulfonate as an oil-water separator was added to a concentration of 25 ppm and electrolysis was performed at a current of 0.12 A, the solution became transparent after 3 minutes and the absorbance reached 0.01. Liquid TO
C was 45.8 ppm.

Examples 2 to 5 The results of carrying out the substances belonging to the first group using the same apparatus and method as those described in Example 1 are as shown in the table below.

Example 6 Using the same apparatus and method as described in Example 1, sodium polyacrylate (polymerization degree: about 50,000) was added to a concentration of 3.1 ppm, the current was 0.2 A, and the absorbance after electrolysis for 10 minutes was 0.036. became. TOC was 18.2 ppm.

Examples 7 and 8 When polyacrylamide was added to a concentration of 7.5 ppm in the same manner as in the above Examples to electrolyze, the absorbance of the solution reached 0.033 after 15 minutes, and the TOC after 17 minutes of electrolysis was 52.3 ppm.

Similarly, add polyacrylamide to the same concentration, and
When ppm tannic acid was added, the solution became transparent after 16 minutes and the TOC after 18 minutes electrolysis was 22.7 ppm.

Example 9 When polyvinyl alcohol was added to a concentration of 7.5 ppm in the same manner as in the above example and electrolysis was performed, the absorbance of the solution reached 0.03 after 16 minutes and the TOC after 20 minutes of electrolysis was 46.5 ppm.

Example 10 Polyvinylpyrrolidone (K90) was added to 12.
When added at a concentration of 5 ppm and electrolyzed, the absorbance of the solution reached 0.018 after 16 minutes, and the TOC after 20 minutes of electrolysis was 58.5 ppm.

Example 11 Polymethyl vinyl ether was added at 12.5 pp as in the previous example.
After adding electrolysis at a concentration of m, the absorbance of the solution after 17 minutes
It reached 0.018, and TOC was 50.7 ppm after 20 minutes of electrolysis.

Example 12 10 pp of thiolignin ammonium salt was added as in the previous example.
When added to the concentration of m and electrolyzed, the absorbance of the solution is 10 minutes later.
The value reached 0.046, and the TOC after 20 minutes of electrolysis was 38.6 ppm.

Example 13 When potassium oleate was added to a concentration of 125 ppm and electrolysis was carried out in the same manner as in the above Example, the absorbance of the solution after 20 minutes reached 0.02, and the TOC after 22 minutes of electrolysis was 20.8 ppm.

When the concentration of potassium oleate is 25 ppm, the absorbance of the solution after 11 minutes electrolysis reaches 0.02, but the TOC is 200 ppm or more, the oil is removed, but most of the nonionic surfactant remains in the solution. Is shown to do.

Example 14 When sodium dodecylbenzene sulfonate was added at a concentration of 25 ppm to perform electrolysis in the same manner as in the above example, the absorbance of the solution after 11 minutes reached 0.014, and the TOC after 16 minutes of electrolysis was 18.4 ppm.

Example 15 In the same manner as in the above Example, sodium dodecyl sulfate was added to the concentration of 25 ppm to perform electrolysis, and the absorbance of the solution after 11 minutes was 0.00
It reached 6, and the TOC after electrolysis for 15 minutes was 18.1 ppm.

Example 16 12.5 ppm sodium dodecyl sulfate as in the above example
Add sodium polyacrylate to the concentration of 3.
When it was added to a concentration of 1 ppm and electrolyzed, the absorbance of the solution reached 0.016 after 14 minutes of electrolysis, and the TOC was 18.3 ppm.

Example 17 Polyvinyl alcohol was added to a concentration of 5 ppm in the same manner as in the above Example, and sodium dodecyl sulfate was added to a concentration of 12.5 ppm to perform electrolysis, and the absorbance of the solution after 11 minutes of electrolysis was
Reached 0.019.

Example 18 Polyvinylpyrrolidone was added at a concentration of 6.25 ppm as in the above Example, and sodium dodecyl sulfate was further added at 12.5 pp.
When added to the concentration of m and electrolyzed, the absorbance after 13 minutes electrolysis is
Reached 0.013.

Continued Front Page (72) Inventor, Koji Abe, 1-1, Higashi, Yatabe-cho, Tsukuba-gun, Ibaraki Inside Institute for Chemical Research, Institute of Industrial Technology (72) Inventor, Kozo Fujita, 6-7-5, Minatojima, Nishiyodogawa-ku, Osaka-shi, Osaka No. 72 Sasakura Machinery Works Co., Ltd. (72) Inventor Yu Shiomi, 6-7-5 Minejima, Nishiyodogawa-ku, Osaka-shi, Osaka Prefecture Examiner Naoto Noda, Sasakura Machinery Works Co., Ltd. (56) References JP-A-57-45306 (JP) , A) JP-A-52-75058 (JP, A)

Claims (2)

[Claims] 1. A first group consisting of hydroxybenzenesulfonic acid, salicylic acid, abietic acid and saponin, and polyacrylic acid in the oil-water separation of emulsified oil wastewater containing oil and fat emulsified with a nonionic surfactant. , A nitrohumic acid, a water-soluble salt of thiolignin, polyvinyl alcohol, polyvinyl methyl ether, and polyvinylpyrrolidone, and a third group of water-soluble salts of higher fatty acids, alkylbenzene sulfonic acids, and sulfuric acid esters of higher fatty acids. At least 1 out of
A method for separating oil-water from emulsified oil wastewater containing a nonionic surfactant, which comprises adding one or more compounds and dissolving the wastewater in the wastewater, and then using the soluble electrode as an anode to electrolyze the wastewater. 2. The addition amount of the compound of each group with respect to the content of the activator contained in the emulsified oil drainage is the first and the third.
About 1/10 or less for the compounds of the first group, and about 1/20 for the compounds of the second group.
The method for separating oil-water from emulsified oil wastewater containing the nonionic surfactant according to claim 1, characterized in that