JPS586554B2 - High speed inoji youkahouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying wastewater by charging wastewater into an electrolytic cell in which an anode and a cathode are arranged and performing direct current electrolysis.

Recently, electrolysis has been widely adopted as a method for treating various types of industrial water, and has achieved outstanding effects in various fields.

The most common electrolysis method is to use aluminum or aluminum alloy for the anode and iron or stainless steel for the cathode to conduct direct current electrolysis of wastewater. It is said to be based on the active colloidal aluminum hydroxide formed in the aluminum hydroxide.

However, the aluminum or aluminum alloy anode has the disadvantage that scale is formed on the surface of the anode due to long-term electrolysis, making it difficult for current to flow, and as a result, the purifying effect of the electrolysis is also reduced.

In order to eliminate this drawback, as a method of supplying aluminum hydroxide produced in wastewater, chemical agents such as aluminum sulfate, aluminum chloride, aluminum nitrate, alum, polyaluminum chloride, etc. are directly added to the wastewater and used as an anode. There is a purification method using direct current electrolysis of wastewater using insoluble electrodes.

As a result of our search for a chemical agent with even better purifying action, the present inventors found that sodium aluminate gave significantly better results than the above-mentioned agents.

The present invention is based on the above findings, and is a method in which aluminum hydroxide is generated by directly adding sodium aluminate to wastewater, and the wastewater is subjected to direct current electrolysis using an insoluble anode.

The sodium aluminate used in the method of the present invention is
Compared to the methods using aluminum sulfate, aluminum chloride, aluminum nitrate, alum, and polyaluminum chloride described above, the purification effect of wastewater is extremely superior.

The reason for this is that the above chemicals, such as aluminum sulfate, are hydrolyzed in wastewater to produce aluminum hydroxide and acid, while sodium aluminate is hydrolyzed in wastewater to produce aluminum hydroxide and alkali. It is thought that it is based on

Although the other detailed mechanisms are not clear, experimental results have shown that the combination of addition of sodium aluminate and direct current electrolysis using an insoluble anode has an excellent effect.

The amount of sodium aluminate used in the method of the present invention is such that the aluminum concentration in wastewater is 1 to 1,500 p.
pm, and it may be added in advance to wastewater before electrolysis, or it may be added directly to the tank where electrolysis is being carried out.

Further, the materials of the insoluble anode used in the method of the present invention include, for example, carbon, lead, titanium, platinum, magnetic iron oxide,
Anodes made of high-silicon cast iron or the like are almost insoluble.

The cathode material is not particularly limited and any conductive material can be used.

When wastewater is purified by the method of the present invention, not only is the purification effect extremely excellent, but also there is no tendency for the purification effect to deteriorate because no scale is observed on the anode even after long-term electrolysis.

Examples are shown below.

Example Acidic wastewater with a zinc concentration of 10 ppm and a nickel concentration of 10 ppm was adjusted to pH 7.5 with caustic soda, and the concentration of zinc and nickel in the sap was analyzed using P paper for quantitative analysis. 7.2 ppm, nickel concentration 9. It was 3 ppm.

Add sodium aluminate to the above filtrate as aluminum.
ppm, and further adjust the pH to 7.5 with hydrochloric acid.
The solution in this state was used as an electrolyte, the carbon plate was used as an anode, the iron plate was used as a cathode, and a direct current of 0.1 ampere per liter of electrolyte was passed for 30 minutes.

As a result of analyzing the concentration of zinc and nickel in the electrolyte before and after electrolysis, the concentration of zinc and nickel in the P solution was analyzed using P paper for quantitative analysis.The zinc concentration before electrolysis was 5. 4ppm, nickel concentration 7. The zinc concentration after electrolysis was 0.8 ppm, and the nickel concentration was 0.8 ppm.

Note that the above zinc concentration 7. 2ppm, nickel concentration 9.
To a 3 ppm solution, aluminum sulfate was added to one side, and polyaluminum chloride was added to the other to give an aluminum content of 5 ppm, and the subsequent operations were exactly the same as above. As a result, the results before electrolysis when aluminum sulfate was added Zinc concentration 6.6 ppm, nickel concentration 8.2 ppm, zinc concentration after electrolysis 3. 8 ppm, nickel concentration 4.5 ppm, and zinc concentration before electrolysis when polyaluminum chloride is added. 9ppm, nickel concentration 8. 4 ppm, zinc concentration after electrolysis 4. 1 1ppm, nickel concentration 5.
It was 3 ppm.

Claims (1)

[Claims] 1. A method for purifying wastewater by electrolysis, characterized by adding sodium aluminate to the wastewater supplied to the electrolytic cell to generate aluminum hydroxide in the wastewater, and electrolyzing using an insoluble anode. Wastewater purification method.