JP2012091164A - Method for making colored turbid water purifying functional water and method for using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for making electrolytic functional water having a function capable of efficiently decoloring and purifying colored turbid water without producing sludge, and a simple and economical colored turbid water purifying treatment method for decoloring and purifying the colored turbid water by adding the made functional water to the colored turbid water.SOLUTION: A method for the purifying treatment of organic colored turbid water employs a system for passing an aqueous solution containing an electrolyte through an electrolytic reaction tank as an ascending flow to subject the obtained electrolytic water to gas-liquid separation and adding electrolytic functional water effective for discoloration and purification to wastewater. An iridium oxide or conductive diamond type electrode is used as an anode.

Description

  The present invention relates to a decolorizing and purifying treatment for colored polluted water. Specifically, the present invention relates to a method for producing and using functional water effective for decolorizing contaminated water containing organic coloring substances.

  Pollution of public water areas due to colored wastewater impairs aesthetics. In particular, when the color-causing substance is an organic substance, the dissolved oxygen concentration decreases as the pollution progresses, killing living creatures that live in the water, or generating an unpleasant odor and deteriorating the surrounding living environment. It is rare.

Conventional methods for decolorizing organic colored polluted water include an adsorption method using activated carbon, activated alumina or an ion exchanger, an ion exchange method, or a coagulation precipitation method using a coagulant such as aluminum sulfate or iron salt.
In the adsorption method or ion exchange method, it is necessary to replace the adsorbent or ion exchanger having a reduced removal effect with a new one or regenerate and use it repeatedly. When it is replaced with a new one, there is a problem that the replacement cost is required and the running cost becomes high. In addition, when regenerated and used, high-concentration regenerated waste liquid is discharged along with the regenerating operation, which necessitates disposal of the processing and further costs, and makes the operation complicated. .
In the coagulation sedimentation method, there is a problem in that sludge is generated along with the reaction and the disposal is required.

There is an electrolytic decolorization method as a decolorization method that does not generate sludge. In this method, the colored wastewater is passed under the condition that a necessary amount of current is supplied to the electrolytic reaction tank to decolorize. In the electrolytic decolorization method, colored polluted water can be purified by setting the amount of electricity charged and the residence time in the electrolytic reaction tank according to the state of contamination of the colored waste water. However, the surface of the electrode often deteriorates due to the influence of various coexisting substances in the polluted wastewater, and the durability of the electrode used is shortened. In some cases, it cannot be used. Therefore, for practical use, it is necessary to take careful measures such as filtering and removing suspended substances in the colored polluted water in advance.

In addition, a method has been developed in which functional water generated by electrolysis of water containing an electrolyte in a colored solution is brought into contact with the colored liquid under light irradiation to remove the color (see Patent Document 1). In this method, since there is a limit to the depth of penetration of the irradiated light into the colored solution, the contact efficiency between the colored solution and the irradiated light is low, and there remains a problem that it takes a long time to purify a large amount of colored polluted water. ing.

In addition, as an improvement in the durability of the electrode, an electrolysis apparatus using a special electrode prepared using platinum and iridium oxide as an electrode active material for an anode and a cathode, and a pair of aqueous solutions containing chloride ions in an aqueous solution. A method of generating hypochlorous acid water by immersing it as an electrode and subjecting it to direct current electrolysis while changing the polarity at regular intervals has also been studied. Decolorization is mentioned as one of the utilization methods of the hypochlorous acid water produced | generated by this method (refer patent document 2). Although this method is expected to improve the durability of the electrodes, there is a problem that the power supply operation circuit for converting the polarity of the pair of electrodes every predetermined time becomes complicated.

Further, there is a wastewater treatment method characterized by gas-liquid separation of treated water in an electrolytic reaction tank, and then liquid passing treatment in a subsequent electrolytic reaction tank (see Patent Document 3). This method is an electrolytic treatment method using a conductive diamond electrode for wastewater containing an oxidizable substance and an electrolyte substance. The wastewater is directly passed through an electrolytic reaction tank to separate the treated water from gas and liquid. Thus, the resistance in the subsequent electrolytic reaction tank is reduced. This is because the drainage is brought into direct contact with the surface of the electrode, so that problems such as early deterioration of the electrode and increased cost can be considered.

JP 2000-79386 Japanese Laid-Open Patent Publication No. 2004-204328 JP 2003-236552 A

Journal of Japan Society on Water Environment, 22 (6), 498-504 (1999) Journal of Japan Society on Water Environment, 22 (11), 938 (1999) Thermal nuclear power generation, 51 (12), 1712 (2000)

In order to solve the problems of the prior art as described above, the present invention uses a method for producing electrolyzed functional water effective for decolorizing and purifying colored contaminated water that hardly causes electrode degradation, and the produced electrolyzed functional water. A decolorization method is provided.

An iridium oxide electrode or a conductive diamond electrode is used as the anode, a SUS electrode is used as the cathode, and an aqueous solution containing an electrolyte is passed through a flow-type electrolytic reaction apparatus configured by setting both electrodes at a predetermined interval. A gas-liquid separation tank that separates the gas components generated from the electrolytic treatment water and the electrolytic reaction is installed at the outflow part of the electrolytic treatment water, and only the electrolyzed functional water after the separation of the gas components is added to the organic colored waste water at a predetermined rate and reacted Thus, decolorization and decomposition of organic substances are performed.

It is the schematic of the gas component separation electrolysis reaction apparatus figure of this invention. It is a graph of the residual chlorine concentration measurement result of Examples 1-5 and Comparative Examples 1-5. It is a graph of the absorbance measurement result of paste coloring waste water (comparative example 10) and Example 11.

When the electrode used for the anode is an iridium oxide electrode, an electrode base material having a surface of a titanium material having a thickness of 1 to 5 mm coated with a thin film of iridium oxide to a thickness of 0.5 to 5 μm can be used. The thickness of the titanium material used for the base material can be arbitrarily selected in consideration of its strength depending on the size of the electrode used for the electrolysis apparatus, but is practically used in a thickness range of 1 to 5 mm. The thickness of the iridium oxide thin film may be 0.5 μm or more, but 1 to 5 μm is suitable in consideration of wear during long-term use. However, if it is allowed to increase the manufacturing cost, there is no problem in performance even if the thickness is 5 μm or more.

When the electrode used for the anode is a conductive diamond electrode, an electrode base material having a surface of a niobium material having a thickness of 1 to 5 mm and a conductive diamond thin film coated to a thickness of 2 to 20 μm can be used. The thickness of the niobium substrate is not particularly limited, but usually a niobium substrate having a thickness of 2 to 3 mm is used. The thickness of the conductive diamond thin film is suitably 3 to 10 μm considering the manufacturing cost and the stability of performance.
Silicone can also be used for the electrode substrate instead of niobium. When silicone is used as a base material, it is limited to the case of using a relatively small electrode having a single electrode area of 400 cm ² or less, and when using a larger electrode than that, niobium is used as the base material in terms of electrode strength. It is better to use it.

  As the electrolyte solution, an aqueous solution containing chloride ions and / or sulfate ions is used. Specifically, seawater containing chloride ions and sulfate ions can be used. In places where it is difficult to obtain seawater, an aqueous solution in which sodium chloride or sodium sulfate is dissolved to a predetermined concentration can be used. The salt concentration in these aqueous solutions is 0.5-5 wt. %, But considering the current efficiency, 1 to 3 wt. % Range is practical.

The condition for passing the electrolyte solution through the electrolytic reaction tank is an upward flow. High flow rate conditions are desirable. When the flow rate is slow, the time that the gas generated by the electrolytic reaction stays in the electrolytic reaction tank becomes longer, and the current resistance between both electrodes is increased to increase the voltage between the electrodes and increase the power consumption. .

The electrolytically treated water at the outlet of the electrolytic reaction tank contains a gas component which is a reaction product in addition to the oxidation active substance. This gas contains hydrogen gas generated on the cathode surface, and reduces the activity of the oxidation active substance generated on the anode surface and contained in the electrolytically treated water. Therefore, it is important that the electrolytically treated water at the outlet of the electrolytic cell is promptly separated in the gas-liquid separation tank, and the liquid phase portion separated from the electrolytically treated water containing the oxidation active substance is used as electrolytic functional water.
The structure of the gas-liquid separation tank is not particularly limited as long as it is a structure that efficiently separates the gas and the liquid part, but the simplest structure has an electrolysis water outlet at the top of the electrolytic reaction tank and a gas at the top. It is sufficient to adopt a structure in which a certain amount of electrolytically treated water is stored in the lower part and a liquid outlet that allows only the liquid to flow out from the liquid storage part is provided. It is more effective if the structure (Fig. 1) is filled with inert particles to enhance the gas-liquid separation effect of the liquid storage tank, but the structure is not necessarily filled with a filler in order to make the structure simpler. Can be achieved.

Examples 1-5
An electrode material in which a surface of a titanium material (size: 50 mm × 50 mm) having a thickness of 2 mm is coated on the anode and iridium oxide having a thickness of 1 to 3 μm is coated, and SUS316L having the same size is used for the cathode, and the distance between the electrodes is 5 mm. In the electrolytic reaction cell set as described above, the sodium chloride concentration was 0.25 to 3.0 wt. Obtained by conducting an electrolysis experiment under a constant current condition of 3A, and subjecting the electrolyzed water to gas-liquid separation. Electrolytic functional water was collected and the residual chlorine concentration was measured. The measurement results are shown in Table 1.

Comparative Examples 1-5
Instead of the electrode used in Example 1, a surface of a titanium material (size: 50 mm × 50 mm) having a thickness of 2 mm was coated with platinum having a thickness of 2 to 3 μm on the anode, and SUS316L of the same size was used on the cathode. Otherwise, the electrolysis experiment of the aqueous solution containing sodium chloride was conducted under the same conditions as in Example 1, and the residual chlorine concentration in the electrolysis functional water was measured. The measurement results are shown in Table 2.











As can be seen from Table 1, the residual chlorine concentration tends to increase as the NaCl concentration used as the electrolyte increases. When the generated residual chlorine concentration is compared, the NaCl concentration is 0.5 wt. % Or more, especially 1-3 wt. It can be seen that the concentration under the condition of% is high.
It was also found that the concentration of residual chlorine produced by the electrolytic reaction was lower when a platinum electrode was used than when an iridium oxide electrode was used. The result of Examples 1-5 and the result of Comparative Examples 1-5 are shown in FIG. From these results, it has been found that when an electrolyte containing chloride ions is used as the electrolyte, it is more effective to use the iridium oxide electrode than the platinum electrode to increase the generation efficiency of residual chlorine.

Comparative Example 6
Of the conditions of Examples 1 to 5, sodium chloride was changed to sodium sulfate, the same experiment was performed, and 1 ml of the obtained electrolyzed functional water was added to 50 ml of waste water (absorbance 0.103 at a wavelength of 560 nm) and stirred. After mixing, the decolorization effect was compared by measuring the absorbance after standing for about 1 hour.
Under this condition, no decolorization effect was obtained. This indicates that the iridium oxide electrode is not suitable when an aqueous solution containing sulfate ions is used as the electrolyte.

Examples 6-7, Comparative Examples 7-9
A surface of a niobium material (size: 50 mm × 50 mm) having a thickness of 3 mm is coated with 2.5 to 3 μm thick conductive diamond on the anode, and SUS316L is used on the cathode. The experiment was conducted under the same conditions as in Examples 1 to 5, except that the flow rate of sodium was changed from 3 L / h to 0.3 L / h. Then, 1 ml of the electrolyzed functional water obtained was added to 50 ml of waste water (absorbance 0.088 at a wavelength of 560 nm), mixed with stirring, and then the absorbance at a wavelength of 560 nm was measured after standing for about 1 hour to change the absorbance. The rate of decrease was determined from the amount. The results are shown in Table 3.











As can be seen from Table 3, it can be seen that the decolorization rate increases as the electrolyte concentration increases. From this, it was found that decolorization can be achieved by using electroconductive functional water produced by an electrolytic reaction using sodium sulfate as an electrolyte using a conductive diamond electrode as an anode. Further, it was found from Comparative Example 6 and Examples 6 to 7 that it is suitable to use conductive diamond for the anode when an aqueous solution containing an appropriate amount of sulfate ion is used for the electrolyte.

Examples 8-11, Comparative Example 10
An electrode material in which 2.5 to 3 μm thick conductive diamond was coated on the surface of a 3 mm thick niobium material (size: 50 mm × 50 mm) was used for the anode, and SUS316L of the same size was used for the cathode. Inside the electrolytic reaction cell in which the distance between the electrodes was set to 10 mm, the sodium chloride concentration was 3.0 wt. % Of the aqueous solution adjusted to a concentration of 0.3% / h, and the electrolytic function water was obtained by conducting an electrolysis experiment with an input current of 0.25 to 1.5 A. After adding 5 ml to 40 ml of waste-colored waste water and stirring and mixing, the absorbance at TOC, TN, and 560 nm after standing for about 1 hour was measured. The results are shown in Table 4.












As can be seen from Table 4, it can be seen that the bleaching rate increases as the current value is increased. However, the increase rate of the decolorization rate under the condition that the current value is increased from 1A to 1.5A is lower than the increase tendency of the decolorization rate at 0.25 to 1A. From this, it was found that there is an appropriate current value for decolorizing reasonably. In addition, TOC and TN were reduced by adding electrolyzed functional water, so organic substances were decomposed and denitrified, and it was found that increasing the current value increased the reduction rate. .

1. 1. Electrolyte solution 2. exhaust gas Electrolytic functional water 4. Anode 5. Cathode 6. 6. Gas-liquid separation tank Gas-liquid separation accelerator packed bed 8. Product gas9. 9. Measurement result of residual chlorine concentration in electrolyzed functional water when using iridium oxide electrode 11. Measurement result of residual chlorine concentration in electrolyzed functional water when platinum electrode is used Nori-colored waste water 12.3 wt. Treatment water after addition of% NaCl electrolytic functional water

Claims (5)

An electrolytic functional water characterized by separating the generated gas component and the electrolyzed water after passing an aqueous solution containing an electrolyte upward through an electrolytic reactor using an iridium oxide electrode or a conductive diamond electrode as an anode A method for decolorizing and purifying organic colored wastewater, characterized in that the manufacturing method and the produced electrolyzed functional water are added to organic colored wastewater and allowed to react for a predetermined time.  The method for producing electrolyzed functional water according to claim 1, wherein the iridium oxide electrode is an electrode material having a titanium base surface coated with a thin iridium oxide film having a thickness of 0.5 to 5 µm. Purification method for organic colored wastewater. 2. The method for decolorizing and purifying organic colored wastewater according to claim 1, wherein the conductive diamond electrode is an electrode material having a surface of a niobium base material coated with a thin conductive diamond of 2 to 20 [mu] m. 4. The method for decolorizing and purifying organic colored wastewater according to claim 3, wherein the aqueous solution containing the electrolyte is an aqueous solution containing chloride ions or sulfate ions or both ions, and conductive diamond is used for the anode. The method for decolorizing and purifying organic colored wastewater according to claim 1 and 2, wherein an aqueous solution containing chloride ions is used as an electrolyte.