JPS5931398B2 - Treatment method for wastewater containing thiocyanine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating wastewater containing thiocyanide, and more specifically, the present invention relates to a method for treating wastewater containing thiocyanide, and more specifically, the thiocyanide in the wastewater is removed by contacting the wastewater containing thiocyanine with oxygen in the presence of a Raney copper catalyst and oxidatively decomposing the thiocyanide. It is related to the method of

The term thiocyanine used herein refers to compounds that liberate thiocyanine ions, such as thiocyanic acid and thiocyanate.

Since thiocyanate is generally used in the production of synthetic resins, dyes, pharmaceuticals, etc., it is often contained in these wastewaters.

In addition, fluid catalytic cracking equipment (F
Wastewater discharged from CC) always contains thiocyanate.

Furthermore, coke oven wastewater produced in steel manufacturing and the like contains high concentrations of thiocyanide, which poses a problem in its treatment.

Since thiocyanide is not included in cyanide, it is not a harmful substance, but since it is detected in chemical oxygen demand (COD) (thiocyanide: COD - approximately 1:1), when discharging wastewater containing thiocyanide, Naturally, that processing is necessary.

At present, thiocyanide in wastewater is treated together with other COD components by microbial treatment methods such as activated sludge and trickling filters.

However, in order to treat thiocyanine with microorganisms,
If the contact time required to decompose the thiocyanide is long and the concentration of thiocyanide ions is high,
It may even inhibit microorganisms.

Furthermore, the microbial treatment method requires maintenance of DH suitable for microbial treatment, addition of nutrients (nitrogen, phosphorus, etc.), sludge concentration (ML
This requires complicated operations such as adjusting SS) and processing excess sludge.

In addition, thiocyanine-containing wastewater is treated at high temperature and high pressure (30KV/c).
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There is also a method of wet oxidation at a temperature of about 200°C, but it is not economical and is therefore not widely used.

The present inventors have already applied for a "method for treating wastewater containing polyvinyl alcohol" as a method for effectively treating wastewater containing thiocyanine in a short time by overcoming the drawbacks of the microbial treatment method and wet oxidation method. (Special application 1805-1983)
We have discovered that thiocyanine ions can be easily oxidized and decomposed by using the same Raney copper catalyst as used in ``Method for treating cyanide-containing wastewater'' (Japanese Patent Application No. 36461/1983). be.

In particular, sulfur-containing compounds such as thiocyanide are often poisonous substances for catalysts, and the ability to oxidize and decompose such poisonous substances using a catalyst is revolutionary.

The present invention is characterized in that wastewater containing thiocyanide is brought into contact with one or more selected from the group consisting of pure oxygen, oxygen-containing gas, and oxygen-generating substances in the presence of a Raney copper catalyst. A method for treating wastewater containing thiocyanide is provided.

The Raney copper catalyst used in the present invention refers to copper and one or two metals (magnesium, aluminum, zinc, iron, nickel, tin, lead, silica, titanium, boron, etc.) that are attacked by water, alkalis, acids, etc. It means something obtained by applying an alkaline aqueous solution such as sodium hydroxide or an acid aqueous solution such as hydrochloric acid to an alloy with at least one species, and the amount of metal eluted from outside the copper plate by the alkali or acid is not particularly limited.

In addition, the weight ratio of copper to copper plate outer metal is usually 1:
1 is used, but it is not limited to this ratio.

An example of a Raney copper catalyst preparation method is 1:1 by weight.
When a sodium hydroxide aqueous solution is applied to the copper-aluminum alloy, an elution reaction occurs rapidly, and a Raney copper catalyst in which more than 90% of the aluminum in the alloy is eluted is obtained.

In this way, the Raney copper catalyst becomes porous due to the elution of metal outside the copper plate.

The Raney copper catalyst obtained as described above is usually adjusted to have a particle size of about 200 mesh from the viewpoint of strength.
It is desirable to select an appropriate particle size depending on the method of contact reaction with thiocyanine-containing wastewater, and it is not necessary to select this particle size.

Next, the method of contacting the thiocyanine-containing wastewater with the Raney copper catalyst is not particularly limited, and any method such as a completely mixed type, fixed bed, fluidized bed, or moving bed may be used.

Further, the oxygen necessary for oxidative decomposition may be dissolved in the raw water containing thiocyanide in advance, or may be supplied in a reaction tank.

Further, oxygen may be pure oxygen gas, liquid oxygen, air, oxygen-containing waste gas, oxygen-generating substances such as hydrogen peroxide, etc., and may be used alone or in combination.

Regarding the amount of oxygen supplied, it is sufficient to supply about 1.2 times the theoretical amount of oxygen required to oxidize thiocyanide.

Further, the reaction temperature and reaction pressure may be normal temperature or normal pressure, and there is no need to particularly raise the temperature or apply pressure.

However, if it is desired to increase the reaction efficiency, this can be achieved by increasing the temperature or applying pressure.

According to the present invention, thiocyanine ions in thiocyanide-containing wastewater can be easily removed by oxidative decomposition using oxygen in the presence of a Raney copper catalyst at room temperature and pressure, which requires less complicated operations than conventional treatment methods. It has the advantage of being able to be oxidized and decomposed in a short time.

Furthermore, the reaction equipment is also smaller compared to microbial treatment.

Furthermore, when the Raney copper catalyst contains aluminum, iron, etc., these are oxidized and eluted as hydroxides, which have the effect of coagulating suspended substances in wastewater.

The present invention will be explained in detail below using examples.

Example 1 2 tons of wastewater containing about 1100 pp of potassium thiocyanate
1. Raney copper catalyst (particle size: 20C mesh, copper content: 96.2wt) was placed in two beakers of 1.5t each.
%, aluminum content: 3.8wt%, manufactured by Yoken Fine Chemical Ho) 30 cc was added to one of them, and no catalyst was added to the other one, and the same amount of air was blown into each and stirred; Oxidative decomposition of thiocyanate was carried out.

The results are shown in Table 1.

As is clear from Table 1, oxidative decomposition of thiocyanate is not observed at all with a contact time of 3 hours in the case without catalyst, but oxidative decomposition easily occurs in the case in which Raney copper catalyst is added.

In addition, when 30 tons of the same wastewater containing 1100 pp of potassium thiocyanate was adjusted to pH 7.0 and treated with activated sludge admixed with thiocyanate (MLSS = 2000
ppm), and the thiocyanine concentration was 10 ppm after 3 hours.
It became.

This also shows that the oxidation rate using the Raney copper catalyst is faster.

Claims (1)

[Claims] 1. Thiocyanide-containing wastewater, which is characterized by contacting thiocyanin-containing wastewater with one or more selected from the group consisting of pure oxygen, oxygen-containing gas, and oxygen-generating substances in the presence of a Raney copper catalyst. Wastewater treatment methods.