JPH11128948A - Removal of anionic surfactant in wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new treatment method for removing an anionic surfactant in wastewater in a small scale facility. SOLUTION: This method is for easily removing a synthetic anionic surfactant in wastewater in a relatively small scale facility. A first method includes processes of taking an aqueous solution containing an anionic surfactant and sodium chloride in a cathode chamber and an aqueous sodium chloride solution in an anode chamber, installing a partitioning membrane such as cellophane membrane between both chambers, and applying d.c. while using an iron net as the anode and carbon as the cathode. Consequently, the anionic surfactant is moved to the anode chamber and bonded with iron ion produced in the anode chamber and precipitated and removed. A second method for removing an anionic surfactant includes processes of bonding a cationic pigment and an anionic surfactant in an aqueous solution and passing the resultant anionic surfactant through an adsorptive solid body represented by silica gel or previously depositing a cationic pigment on an adsorptive solid and then passing an aqueous solution containing an anionic surfactant through the solid. An anionic surfactant in wastewater can easily be treated in a relatively small scale facility by employing those methods.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing synthetic anionic surfactants from domestic wastewater and industrial wastewater.

[0002]

2. Description of the Related Art Conventionally, anionic surfactants have been removed by treatment with microorganisms using activated sludge, photo-oxidation using hypochlorous acid, adsorption using activated carbon, and positive ions derived from aluminum chloride or ferric chloride. A method of adsorbing and precipitating on a colloid is used.

[0003]

At present, the method generally used for the treatment of anionic surfactants, particularly in domestic wastewater, is the treatment of microorganisms with activated sludge, but requires a large-scale facility. Takes a long time for processing.

[0004]

Means for Solving the Problems The present inventors have intensively studied a method for treating a synthetic anionic surfactant which can be easily carried out without using a large-scale facility, and as a result, the present invention has been achieved. A metal having a relatively large ionization tendency, such as iron, was used as an anode, and various electrodes, such as carbon, were used as a cathode. A diaphragm, such as a cellophane film, was placed between the cathode and the anode. An aqueous solution containing an anionic surfactant and sodium chloride was placed in the cathode chamber, and an aqueous sodium chloride solution was placed in the anode chamber, and a DC voltage was applied. When a voltage was applied while the pH in the anode chamber was constantly maintained between 10 and 11, the concentration of the synthetic anionic surfactant decreased to less than the original 15% in about 15 minutes.

[0005] The initial concentration of the anionic surfactant in the aqueous solution is preferably 3 to 10 ppm. As the electrolyte in the treatment aqueous solution, sodium chloride, which is an electrolyte generally contained in wastewater, is most effective. The concentration of sodium chloride is preferably 10 g or more per liter of water.

On the other hand, the inventor has noticed that a cationic dye typified by methyl violet and an anionic surfactant are strongly bonded in an aqueous solution, and an anionic surfactant is contained in a fine powdery solid carrying a cationic dye. When passed through an aqueous solution containing a surfactant, the anionic surfactant is effectively adsorbed,
It has been found that its concentration is greatly reduced.

As a solid carrying a dye, a fine powdery solid having a large adsorption surface area represented by silica gel for chromatography is effective.

The cationic dyes used include, in addition to methyl violet, ethyl violet, crystal violet, fuchsin, methyl green, neutral red, brilliant cresyl blue, rhodamine B,
Many were effective, such as safranin, but the most effective was methyl violet.

In the method in which a cationic dye and an anionic surfactant are preliminarily mixed and adsorbed on a solid, only methyl violet is effective when silica gel for chromatography is used, and good results are obtained with other cationic dyes. Was not obtained.

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 A 150 ml aqueous solution containing about 1% sodium chloride and 4 ppm of an anionic surfactant (a mixture of dodecylbenzenesulfonic acid type and alkyl ether sulfate type) was placed in a container having a cellophane film fixed to the bottom. Hereinafter, this is referred to as a cathode chamber solution), and a carbon electrode (Bincho charcoal) was inserted. This container was placed in 250 ml of an aqueous solution of sodium chloride of the same concentration (hereinafter, referred to as an anode compartment solution) and fixed. A 1 mm mesh iron mesh cut into 5 cm × 10 cm was inserted into the anode compartment solution. A carbon electrode was connected to the negative electrode of the DC power supply, and a wire mesh electrode was connected to the positive electrode, and a voltage of 6 V was applied. An aqueous solution of sodium hydroxide was appropriately added to the solution in the anode chamber, and the pH value was kept between 10 and 11. The cathode compartment solution and the anode compartment solution were sampled at regular intervals, and the concentration of the anionic surfactant contained in each solution was measured according to the usual method of the ethyl violet method. FIG. 1 shows a graph of the change in the concentration of the obtained anionic surfactant.

Example 2 After arranging absorbent cotton in a plastic column having a diameter of 3 cm, 1 g of silica sand was added, and 10.0 g of silica gel for chromatography was filled from above. Into this, 50 ml of an aqueous solution containing 0.1% of methyl violet was poured. After the water was completely drained from the end of the column, 100 ml of an aqueous solution containing 3 ppm of an anionic surfactant (a mixture of dodecylbenzenesulfonic acid type and alkyl ether sulfate type) was used.
Was flowed through the column. The aqueous solution flowing out from the tip
Each ml was collected (sample numbers 1 to 10), and the concentration of the anionic surfactant contained in each sample was measured in accordance with the usual method of the ethyl violet method. FIG. 2 shows a graph of the obtained concentration change.

Example 3 After arranging absorbent cotton in a plastic column having a diameter of 3 cm, 1 g of silica sand was added, and 10.0 g of silica gel for chromatography was filled thereon. 50 ml of an aqueous solution containing 6 ppm of an anionic surfactant (a mixture of dodecylbenzenesulfonic acid-based and alkyl ether sulfate-based) was added to 0.5 ml of an aqueous solution.
An aqueous solution mixed with 50 ml of an aqueous solution containing 1% methyl violet was passed through the column. A 10 ml portion of the aqueous solution flowing out from the tip was sampled (sample numbers 1 to 10), and the concentration of the anionic surfactant contained in each sample was measured according to the standard method of the ethyl violet method. FIG. 3 shows a graph of the obtained concentration change.

【The invention's effect】

By utilizing the method of the present invention, the treatment of an anionic surfactant can be performed in a relatively small facility in a single hour.

[Procedure amendment]

[Submission date] April 17, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a diagram showing a change over time in the concentration of an anionic surfactant in a cathode chamber in Example 1. The solid line in the figure represents the concentration change of the anionic surfactant, and the dotted line represents the decrease rate (%) of the surfactant concentration when the initial concentration of the anionic surfactant is set to 100.

FIG. 2 is a diagram showing the concentration of an anionic surfactant in an aqueous solution (sample numbers 0 to 10) flowing out of a column in Example 2. The solid line in the figure represents the concentration change of the anionic surfactant, and the dotted line represents the initial concentration of the anionic surfactant of 100.
Represents the reduction rate (%) of the surfactant concentration.

FIG. 3 is a diagram showing the concentration of an anionic surfactant in an aqueous solution (sample numbers 0 to 10) flowing out of a column in Example 3. The solid line in the figure represents the concentration change of the anionic surfactant, and the dotted line represents the initial concentration of the anionic surfactant of 100.
Represents the reduction rate (%) of the surfactant concentration.

Claims (3)

[Claims] 1. An anionic surfactant is moved to an anode chamber by a two-chamber DC electrolysis using a metal anode, and then bound to a metal cation generated by an electrode reaction, and then precipitated, whereby the anion is precipitated. A treatment method for removing a surfactant from an aqueous solution. 2. A method for removing an anionic surfactant from an aqueous solution by passing an aqueous solution containing an anionic surfactant through a column packed with a solid on which a cationic ionic dye has been adsorbed. Alternatively, a method in which a cationic dye aqueous solution and an anionic surfactant aqueous solution are mixed, and the mixture is passed through a column filled with a solid to remove the anionic surfactant from the aqueous solution. 3. A method for removing an anionic surfactant from an aqueous solution by combining the methods of claim 1 and 2.