WO2016190108A1

WO2016190108A1 - Method for treating cyanogen-containing wastewater

Info

Publication number: WO2016190108A1
Application number: PCT/JP2016/064012
Authority: WO
Inventors: 村上　誠; 玲奈田上; 英則平嶋
Original assignee: 株式会社片山化学工業研究所; ナルコジャパン合同会社
Priority date: 2015-05-22
Filing date: 2016-05-11
Publication date: 2016-12-01
Also published as: JPWO2016190108A1; CN107614444A; JP2020104115A; AU2016268593A1; KR102119234B1; KR20180010244A; JP7204140B2

Abstract

A method for treating cyanogen-containing wastewater, comprising adding a hypochlorite and hydrogen peroxide simultaneously or separately to cyanogen-containing wastewater, inducing decomposition of the cyanogen in the wastewater and/or formation of a water-insoluble compound with the cyanogen, and removing the cyanogen from the wastewater.

Description

Treatment method of wastewater containing cyanide

The present invention relates to a method for treating cyanide-containing wastewater that can suppress the amount of chemicals added as much as possible and remove cyanide in wastewater safely and inexpensively with a simple operation.
In the present invention, all cyan contained in the wastewater in various forms, that is, the hardly decomposable cyan complex, the easily decomposable cyan complex and the cyanide ion can be treated by a simple operation.

Cyan has a strong negative impact on ecosystems, and cyanide-containing wastewater (also referred to as “cyan wastewater”) cannot be released directly into nature. Cyan drainage standards are established based on the Water Pollution Control Law. Cyan removal processing is performed so as to satisfy this standard (1 mg / L or less). Further, depending on the region, an additional drainage standard that is lower than the above-mentioned drainage standard value is set by regulations.
Cyan is present in the wastewater in three forms of a hardly-decomposable cyanide complex, an easily-decomposable cyanide complex, and a cyanide ion, although there are some contents due to the origin of the wastewater.

Various methods have been proposed and put to practical use for removing cyan from waste water containing cyan, and all have their advantages and disadvantages, and are used properly according to the state of waste water.
For example, (1) alkaline chlorine method in which cyanide-containing wastewater is adjusted to alkalinity and then injected with chlorine to oxidatively decompose cyanide. (2) cyanide is oxidized and decomposed into nitrogen gas and bicarbonate with strong ozone oxidizing power. (3) Oxidation decomposition method such as electrolytic oxidation method (electrolysis method) in which cyanide is electrolyzed by using an insoluble electrode and an oxidation reaction (electrolysis method) is performed; As a feed compound, for example, ferrous sulfate is added to form a poorly soluble ferri / ferrocyanide, and the bitumen method in which this is precipitated and removed, (5) zinc chloride and a reducing agent are added, and the insoluble produced (7) Insoluble complex methods such as zinc white method for precipitating and removing complex and (6) reducing copper salt method for adding and removing divalent copper salt and reducing agent and precipitating and removing generated insoluble complex; Acclimatized microorganisms (cyanolytic bacteria A biological treatment method for decomposing cyanide; (8) a thermal hydrolysis method in which cyanide-containing wastewater is kept at a high temperature to hydrolyze cyanide compounds into ammonia and formic acid, and coexisting heavy metals are precipitated as simple substances or oxides; 9) In addition to the decomposition of cyanide, there are hydrothermal reactions such as a wet oxidation method that also oxidizes and decomposes organic pollutants.

Further, the applicant of the present invention has proposed the following method for treating cyanide-containing wastewater.
(A) A manganese compound that is soluble in hypochlorite and water and capable of forming manganese ions in water is added to the cyanide-containing wastewater, and the generated water-insoluble manganese salt is removed from the wastewater. Cyanide-containing wastewater treatment method for removing cyan in the interior (see Japanese Patent No. 4106415: Patent Document 1)
(B) After adding the amount of formaldehyde corresponding to 1.4 mol or more of the amount of cyanide compound to the cyanide compound-containing wastewater, the first stage reaction is carried out, and then a substantially effective reaction amount of hydrogen peroxide is added. Method of treating cyanide-containing wastewater by adding 3.0 mol or more of cyanide content and performing second-stage reaction at pH 7.0 or more (see JP-A-02-35991: Patent Document 2)

However, the above-described prior art requires complicated steps and operations, and accordingly, a plurality of reaction vessels may be required. In addition, depending on the type of waste water, such as waste water containing thiocyanate ions or ammonium ions, the effect of removing cyan is not sufficient, and the cyan concentration of the waste water after treatment cannot be set to the drainage standard (1 mg / L or less). In some cases, the treated wastewater cannot be discharged directly into sewage.
Based on the Water Pollution Control Law, the drainage standard for hydrogen ion concentration (pH) is set to 5.0 to 9.0 for sea areas and 5.8 to 8.6 for areas outside sea areas. In the above prior art, when the pH of wastewater is adjusted to acidic or alkaline, neutralization treatment is required to adjust not only the cyanide concentration of wastewater but also the pH within the drainage standard range before discharging into sewage etc. Sometimes it becomes.

Japanese Patent No. 4106415 JP 02-35991 A

For example, in the method (A) of Patent Document 1 described above, if an excessive amount of drug is added to cyanide-containing wastewater, the cyan concentration can be reduced to a specified value or less, but the drug addition amount is suppressed as much as possible. There is a demand for safer cyan processing.
Therefore, the present invention suppresses the amount of chemicals added as much as possible and removes cyanide in wastewater safely and inexpensively with a simple operation regardless of the type of wastewater in which thiocyanate ions or ammonium ions are present. It is an object of the present invention to provide a method for treating cyan-containing wastewater to be obtained.

The inventors of the present invention, as a result of intensive research to solve the above problems, surprisingly, by adding an effective amount of hypochlorite and hydrogen peroxide simultaneously or separately, unexpectedly, conventionally In addition, the present inventors have found the fact that cyanide in wastewater can be removed safely and inexpensively with a simple operation while minimizing the amount of drug added, and the present invention has been completed.

Thus, according to the present invention, hypochlorite and hydrogen peroxide are added to cyanide-containing wastewater simultaneously or separately to decompose cyanide in the wastewater and / or produce water-insoluble compounds with cyanide. To provide a process for treating cyanide-containing wastewater comprising removing cyanide from the wastewater.

According to the present invention, cyanide can be removed safely and inexpensively with a simple operation regardless of the type of wastewater in which thiocyanate ion or ammonium ion exists, as much as possible, compared to the conventional method. A method for treating contained wastewater can be provided.
That is, according to the present invention, all the cyan contained in the wastewater in various forms, that is, the hardly decomposable cyan complex, the easily decomposable cyan complex, and the cyanide ion, the amount of the drug added can be suppressed as much as possible, and simple. Can be handled by operation.
Therefore, even if the wastewater treated by the method of the present invention is released to nature as it is, the influence on the environment is very small, and the amount of water-insoluble salt (waste) generated after the treatment can be reduced. Is extremely useful in industry.

Moreover, the processing method of the cyan containing waste water of this invention exhibits said effect more, when satisfy | filling any one of the following conditions.
(1) Cyanide content in cyanide-containing wastewater is measured in advance, and 0.1 mol equivalent or more of hydrogen peroxide and 0.1 mol equivalent of hydrogen peroxide as effective chlorine concentration with respect to the measured content Add more,
(2) The cyanide-containing wastewater originally contains one or more metal ions selected from manganese ions, iron ions, and copper ions.
(3) One or more metal compounds selected from manganese compounds, iron compounds, and copper compounds are further added, and (4) cyanide-containing wastewater has a pH of 9 or less.

In the method for treating cyanide-containing wastewater according to the present invention, hypochlorite and hydrogen peroxide are added simultaneously or separately to the cyanide-containing wastewater to decompose cyanide and / or water insoluble with cyanide. It is characterized in that cyanide is removed from the wastewater by producing a compound.

Although the removal of cyan from waste water containing cyanide in the present invention involves “decomposition of cyanide in wastewater” and “generation of water-insoluble compounds with cyanide in wastewater”, the decomposition / generation mechanism is not clear.
The inventors of the present invention said that "decomposition of cyanide in wastewater" is that cyanide is oxidized by added hypochlorous acid and hydrogen peroxide, and further, the produced cyanic acid generates ammonium hydrogen carbonate by hydrolysis. I think it is due to
In addition, the inventors of the present invention indicate that “the production of a water-insoluble compound with cyanide in wastewater” is due to the production of a water-insoluble salt by a cyanide component and metal ions when metal ions are present in the wastewater. I believe.
As described above and clearly from the results of the examples, the treatment method for cyanogen-containing wastewater according to the present invention is based on the combined use effect of hypochlorite and hydrogen peroxide, and originally in cyanide-containing wastewater. Since these compounds and metal ions effectively act on the decomposition of cyan and / or the formation of water-insoluble compounds with cyan, due to the combined effect of existing metal ions or further added metal ions, It is considered that cyanide in wastewater can be removed even with a small amount of chemical added.

(Hypochlorite)
The hypochlorite used in the present invention is not particularly limited as long as it is a compound capable of generating hypochlorous acid in water. For example, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite And alkali metal salts and alkaline earth metal salts of hypochlorous acid such as magnesium hypochlorite, and hydantoin derivatives. In particular, sodium hypochlorite and potassium hypochlorite are industrially easily available and are preferably used in the present invention. Moreover, the hypochlorite obtained by electrolyzing salt solution and seawater with an electrolytic cell may be sufficient.

(hydrogen peroxide)
Examples of the hydrogen peroxide used in the present invention include a hydrogen peroxide aqueous solution having a concentration of 3 to 60%, which is commercially available mainly for industrial use.
In addition, hydrogen peroxide generated from a hydrogen peroxide supply compound (also referred to as a “hydrogen peroxide generator”), or hydrogen peroxide generated by electrolysis of water or an alkaline solution can be used.
Examples of the hydrogen peroxide supplying compound include inorganic peracids such as percarbonate, perboric acid and peroxysulfuric acid capable of releasing hydrogen peroxide in water, organic peracids such as peracetic acid, and salts thereof. Examples of these salts include sodium percarbonate and sodium perborate.
The hydrogen peroxide and the hydrogen peroxide supply compound may be used by diluting or dissolving with water so that a desired hydrogen peroxide concentration is obtained upon addition.

(Addition of compounds)
According to the method of the present invention, a cyanide-containing wastewater is subjected to hypochlorous for removing cyanide from the wastewater by causing decomposition of cyanide in the wastewater and / or formation of cyanide and a water-insoluble compound in the wastewater. Chlorate and hydrogen peroxide are added simultaneously or separately.
Hypochlorite and hydrogen peroxide are each preferably added in the form of an aqueous solution. The concentration of each aqueous solution may be determined in consideration of the workability when adding them to cyanide-containing wastewater, the reactivity between cyan and the added compound, etc. Specifically, the concentration of hypochlorite Is about 10 to 7000 mg / L, and the concentration of hydrogen peroxide is about 10 to 3500 mg / L.

The amount of hypochlorite and hydrogen peroxide is affected by the type and concentration of cyanide-containing wastewater, as well as the type and concentration of other metal ions contained in cyanate-containing wastewater. Therefore, these addition amounts may be appropriately determined according to the conditions. Specifically, the cyan concentration of the cyan-containing wastewater before the treatment is measured in advance, and the addition amount of each additive may be determined based on the measured value.

As described above, the addition amount of the compound varies depending on the cyan content contained in the target cyanide-containing wastewater, but hypochlorite has an effective chlorine concentration of 0.1% as compared to the cyan content in the wastewater. It is preferable that the molar equivalent or more and the hydrogen peroxide is 0.1 molar equivalent or more. More preferably, the hypochlorite has an effective chlorine concentration of 0.5 molar equivalent or more and the hydrogen peroxide is 0.5 molar equivalent or more with respect to the cyan content in the wastewater.
When hypochlorite has an effective chlorine concentration of less than 0.1 molar equivalent, cyanide is removed because hypochlorite is consumed (decomposed) depending on the type of wastewater, such as thiocyanate ions and ammonium ions in wastewater. The effect may be insufficient. Further, when the hydrogen peroxide is less than 0.1 molar equivalent, the effect of removing cyan may be insufficient.
The specific lower limit (molar equivalent) of the effective chlorine concentration of the preferred hypochlorite is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0,. 7, 0.8, 0.9, 1.0, and 1.5.
Specific lower limit values (molar equivalents) of hydrogen peroxide are, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, and 1.5.

(Cyanide wastewater)
Examples of cyanide-containing wastewater to be treated in the present invention include metal cyanide, cyanide, cyanide complex, and cyano complex ion discharged from steel factories, chemical factories, plating factories, coke factories, metal surface treatment factories, etc. And cyan-containing wastewater discharged from a processing apparatus for soil. In particular, the method for treating cyanide-containing wastewater of the present invention is suitable for treating cyanide-containing wastewater having a strong buffering action, such as coke oven wastewater, that is, cyanide-containing wastewater containing ammonium ions.

The cyan content in the cyan-containing wastewater to be treated in the present invention is not particularly limited, but the above-mentioned cyan-containing wastewater is generally about 2 to 500 mg / L in terms of the total cyan concentration. When treating such cyanide-containing wastewater, hypochlorite is used in an effective chlorine concentration of 10 to 7000 mg / L, preferably 10 to 2000 mg / L with respect to the cyanine-containing wastewater. Hydrogen oxide may be added to the cyanide-containing wastewater so that the amount of hydrogen oxide is 10 to 3500 mg / L, preferably 10 to 1000 mg / L.

It is preferred that the cyan-containing wastewater originally contains one or more metal ions selected from manganese ions, iron ions and copper ions.
The cyanide-containing wastewater originally contains the above metal ions, thereby generating water-insoluble manganese salt, iron salt and copper salt by reaction with cyanide in the wastewater, respectively, and promoting the cyan removal effect of the present invention. become.
Although metal ions can have various valences depending on the metal species, in the present invention, manganese ions are preferably divalent, iron ions are divalent, and copper ions are preferably monovalent and divalent.

The manganese ion concentration contained in the cyan-containing wastewater is about 0.1 to 500 mg / L.
If the manganese ion concentration is less than 0.1 mg / L, the effect of removing cyan may be insufficient. On the other hand, if the manganese ion concentration exceeds 500 mg / L, dissolved manganese exceeding the drainage standard remains, which not only adversely affects the environment, but is also not economically preferable.
Specific manganese ion concentration (mg / L) is, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100, 125, 150, 200. , 250, 300, 350, 400, 450, 500.
A preferable manganese ion concentration is 0.1 to 150 mg / L, more preferably 5 to 100 mg / L.

The iron ion concentration contained in the cyan-containing wastewater is about 0.1 to 500 mg / L.
If the iron ion concentration is less than 0.1 mg / L, the effect of removing cyan may be insufficient. On the other hand, if the iron ion concentration exceeds 500 mg / L, dissolved iron exceeding the drainage standard remains, which not only adversely affects the environment, but is also not economically preferable.
Specific iron ion concentration (mg / L) is, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100, 125, 150, 200. , 250, 300, 350, 400, 450, 500.
A preferable iron ion concentration is 0.1 to 150 mg / L, and more preferably 2 to 100 mg / L.

The concentration of copper ions contained in the cyan-containing wastewater is about 0.1 to 500 mg / L.
When the copper ion concentration is less than 0.1 mg / L, the effect of removing cyan may be insufficient. On the other hand, if the copper ion concentration exceeds 500 mg / L, dissolved copper above the drainage standard remains, which not only adversely affects the environment, but is also not economically preferable.
Specific copper ion concentration (mg / L) is, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100, 125, 150, 200. , 250, 300, 350, 400, 450, 500.
The copper ion concentration is preferably 0.1 to 150 mg / L, more preferably 2 to 100 mg / L.

(Metal compound)
In the present invention, it is preferable to further add one or more metal compounds selected from manganese compounds, iron compounds, and copper compounds to cyanide-containing wastewater.
If the cyanide-containing wastewater does not originally contain manganese ions, iron ions, or copper ions, or if it is contained at a low concentration, the same effect as above can be obtained by adding the above metal compound to the cyanine-containing wastewater. Can be obtained.

(Manganese compounds)
The manganese compound used in the present invention is not particularly limited as long as it is soluble in water and can form manganese ions in water, and examples thereof include manganese chloride, manganese sulfate, manganese nitrate, and manganese acetate. . Among these, manganese chloride and manganese sulfate are particularly preferable from the viewpoint of the removal effect of the cyanide compound, and manganese chloride is particularly preferable from the viewpoint of the treatment cost of the cyanogen-containing wastewater.
In the present invention, “soluble in water” means that the compound has a solubility of about 1 g or more with respect to 100 g of water.

(Iron compounds)
The iron compound used in the present invention is not particularly limited as long as it is soluble in water. For example, divalent iron in water such as ferrous chloride, ferrous sulfate, ferrous nitrate, and ferrous acetate. Examples include compounds that can form ions. Among these, ferrous chloride and ferrous sulfate are particularly preferable from the viewpoint of the removal effect of the cyanide compound, and ferrous chloride is particularly preferable from the viewpoint of the treatment cost of the cyanogen-containing wastewater.

In the method of the present invention, an iron compound capable of forming trivalent iron ions in water is added as an iron compound to a cyanide-containing wastewater together with a reducing agent, or trivalent iron ions are added to the reducing cyanide-containing wastewater in water. And a divalent iron ion supply compound produced by reducing an iron compound capable of forming trivalent iron ions in the waste water.
Examples of the reducing agent include sulfite and hydrazine.

(Copper compound)
The copper compound used in the present invention is not particularly limited as long as it is a copper compound that is soluble or easily dispersible in water and can form copper ions in water, and includes a cuprous compound and a cupric compound, They may be either organic copper compounds or inorganic copper compounds.
Examples of the organic copper compound include cupric compounds such as cupric acetate, cupric benzoate, cupric citrate, copper naphthenate, and cupric oleate.

Examples of inorganic copper compounds include monovalent copper ions in water such as cuprous chloride, cuprous fluoride, cuprous bromide, cuprous iodide, cuprous nitrate, and cuprous sulfate. Cuprous compounds that can be formed and divalent copper ions in water such as cupric chloride, cupric fluoride, cupric bromide, cupric iodide, cupric nitrate, cupric sulfate, etc. The cupric compound which can be formed is mentioned.
Since the organic copper compound may increase the COD in the treated cyanide-containing wastewater, inorganic copper compounds are preferred among the above-mentioned copper compounds, and are inorganic in terms of the effect of removing cyan and the cost of treating cyanide-containing wastewater. Cuprous compounds are more preferred, cuprous chloride and cuprous sulfate are more preferred, and cuprous chloride is particularly preferred.

Further, when the cuprous compound is a cuprous salt, a cuprous salt solution containing hydrogen chloride water, an aqueous alkali metal halide solution or ethanol as a solvent is used to stabilize the cuprous salt. It is preferable from the point.
In the method of the present invention, as the copper compound, the cupric compound is added to the cyanide-containing wastewater together with the reducing agent, or the cupric compound is added to the reducing cyanide-containing wastewater, and the cupric compound is added to the wastewater. A cuprous ion supply compound produced by reducing the compound is included.
Examples of the reducing agent include sulfites, divalent iron salts, hydrazine, and the like.

(Compound addition form and concentration)
The above metal compound may be treated with a metal scavenger so as to have a desired metal equivalent concentration upon addition to the cyanide-containing wastewater. Further, it may be used after diluting or dissolving with water such as industrial water.
As said metal scavenger, a liquid chelating agent etc. are mentioned, for example.

The metal compound is preferably added in the form of an aqueous solution. The concentration of the aqueous solution may be determined in consideration of workability when it is added to cyanide-containing wastewater, reactivity between cyan and the added compound, and specifically, the manganese compound has a manganese ion concentration of 0. The iron compound concentration is about 0.1 to 500 mg / L, and the copper compound concentration is about 0.1 to 500 mg / L.
When the cyan-containing wastewater contains manganese ions, iron ions, and copper ions, the addition amounts of the manganese compound, iron compound, and copper compound may be set in consideration of the contents.

As described above, the amount of the compound added varies depending on the target cyanogen-containing wastewater, but the concentration of the manganese compound to be added is about 0.1 to 500 mg / L as the manganese ion concentration.
When the concentration of the manganese compound is less than 0.1 mg / L as the manganese ion concentration, the effect of removing cyan may be insufficient. On the other hand, when the concentration of the manganese compound exceeds 500 mg / L as the manganese ion concentration, dissolved manganese exceeding the drainage standard remains, which not only adversely affects the environment but is also not economically preferable.
The specific concentration of the manga compound is, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100 as manganese ion concentration (mg / L). , 125, 150, 200, 250, 300, 350, 400, 450, 500.
The concentration of the manganese compound is preferably 0.1 to 150 mg / L, more preferably 5 to 100 mg / L as the manganese ion concentration.

As described above, the amount of the compound added varies depending on the target cyanogen-containing wastewater, but the concentration of the iron compound to be added is about 0.1 to 500 mg / L as the iron ion concentration.
When the concentration of the iron compound is less than 0.1 mg / L as the iron ion concentration, the effect of removing cyan may be insufficient. On the other hand, when the concentration of the iron compound exceeds 500 mg / L as the iron ion concentration, dissolved iron exceeding the drainage standard remains, which not only adversely affects the environment but is also not economically preferable.
Specific iron compound concentrations are, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100 as iron ion concentration (mg / L). , 125, 150, 200, 250, 300, 350, 400, 450, 500.
The preferable iron compound concentration is 0.1 to 150 mg / L, more preferably 2 to 100 mg / L as the iron ion concentration.

As described above, the amount of the compound added varies depending on the target cyanogen-containing wastewater, but the concentration of the copper compound to be added is about 0.1 to 500 mg / L as the copper ion concentration.
When the copper compound concentration is less than 0.1 mg / L as the copper ion concentration, the effect of removing cyan may be insufficient. On the other hand, when the concentration of the copper compound exceeds 500 mg / L as the copper ion concentration, dissolved copper exceeding the drainage standard remains, which not only adversely affects the environment but is also not economically preferable.
The specific copper compound concentration is, for example, 0.1, 0.5, 1.0, 2.0, 5.0, 10, 25, 50, 75, 100 as the copper ion concentration (mg / L). , 125, 150, 200, 250, 300, 350, 400, 450, 500.
The concentration of the copper compound is preferably 0.1 to 150 mg / L, more preferably 2 to 100 mg / L as the copper ion concentration.

(Method of adding compound)
The order of addition of hypochlorite and hydrogen peroxide to the cyanate-containing wastewater is not particularly limited, and both compounds may be added simultaneously in the order of hypochlorite and hydrogen peroxide or in reverse order.
Further, the order of addition is not particularly limited when a metal compound is further added, and hypochlorite, hydrogen peroxide, and metal compound are simultaneously added to cyanide-containing wastewater, and three kinds of compounds are separately added to each of three kinds. Two of these may be added simultaneously, and the remaining one may be added thereafter.

That is, as the addition method, there are a one-stage process, a two-stage process, and a three-stage process, and the following combinations can be given. The following “/” means a delimiter of processing, and “(A + B)” means simultaneous addition of A and B (processing in the same stage).
One-stage treatment (1-1) (Hypochlorite + Hydrogen peroxide)
(1-2) (Hypochlorite + Hydrogen peroxide + Metal compound)

Two-stage treatment (2-1) (Hypochlorite) / (Hydrogen peroxide)
(2-2) (hydrogen peroxide) / (hypochlorite)
(2-3) (Hypochlorite + Metal compound) / (Hydrogen peroxide)
(2-4) (hydrogen peroxide + metal compound) / (hypochlorite)
(2-5) (Hypochlorite + Hydrogen peroxide) / (Metal compound)
(2-6) (Hypochlorite) / (Hydrogen peroxide + Metal compound)
(2-7) (hydrogen peroxide) / (hypochlorite + metal compound)
(2-8) (Metal compound) / (Hypochlorite + Hydrogen peroxide)

3-stage treatment (3-1) (Hypochlorite) / (Hydrogen peroxide) / (Metal compound)
(3-2) (Hypochlorite) / (Metal compound) / (Hydrogen peroxide)
(3-3) (hydrogen peroxide) / (hypochlorite) / (metal compound)
(3-4) (hydrogen peroxide) / (metal compound) / (hypochlorite)
(3-5) (metal compound) / (hydrogen peroxide) / (hypochlorite)
(3-6) (Metal compound) / (Hypochlorite) / (Hydrogen peroxide)

Among these, the one-stage process or the two-stage process is preferable from the viewpoint of work efficiency.
In the case of multistage treatment, it is preferable to separate the treated wastewater by sedimentation between each stage or after all treatments, particularly after treatment with a metal compound. In the case of sedimentation between each stage, the next stage compound is added to the resulting supernatant. A specific example is Test Example 3.
In addition, when relatively high cyan wastewater having a COD (COD _Mn : chemical oxygen demand by the acidic high temperature permanganate method) value of 50 mg / L or more is treated in two stages in the field, hypochlorite is used in the preceding stage. It is desirable to add at. Moreover, it is desirable to add hydrogen peroxide at a later stage in terms of safety.

(PH of cyanide-containing wastewater and supernatant)
The cyan-containing wastewater preferably has a pH of 9 or less.
When the cyan-containing wastewater exceeds pH 9, generation of water-insoluble compounds may be incomplete, and cyan may not be efficiently removed.
Moreover, it is preferable that the supernatant liquid when adding a metal compound further is pH 9 or less.
If the supernatant exceeds pH 9, the formation of a water-insoluble compound may be incomplete, and cyan may not be efficiently removed.
The preferable lower limit of the pH of the cyan-containing waste water and the supernatant is about 6, but the pH of the cyan-containing waste water to be treated is usually about 6 to 9, so there is no need for pH adjustment.
However, when the cyan-containing wastewater and the supernatant liquid are above pH 9 and below pH 6, an acid or alkali that does not interfere with the reaction in the treatment of the present invention, such as sulfuric acid or sodium hydroxide, may be added to the treated wastewater.

When adding hypochlorite, hydrogen peroxide and a metal compound, and when reacting these added compounds with cyanide, it is preferable to stir the mixed solution from the viewpoint of the effect of removing cyanide. This stirring is preferably performed every time each compound is added.
In order to promote the reaction during stirring, the mixed solution is preferably in a state of being heated to some extent so that the added compound is not decomposed, and the liquid temperature is about 20 to 50 ° C.
Furthermore, the time required for the reaction during stirring varies depending on the amount of cyanide-containing wastewater, the type and concentration of cyanide, the form of the treatment apparatus and the scale thereof, etc. Just decide. Usually, the stirring time may be 10 minutes or more, more preferably 20 to 60 minutes.

(Processing and precipitation separation)
For a series of operations such as addition of compound, stirring and mixing, sedimentation separation, removal of water-insoluble salt, known apparatuses such as an additive tank, a reaction treatment tank, a thickener and a turbidity sedimentation basin can be used. The device may be diverted.
In the method for treating cyanide-containing wastewater of the present invention, known agents such as a rust inhibitor, a corrosion inhibitor, a scale dispersant, and a slime control agent may be used in combination as long as the effects of the present invention are not impaired.
Further, in the sedimentation separation, a surfactant or a flocculant may be added as long as the effects of the present invention are not impaired.
Here, in the present invention, “water-insoluble” means that the compound (salt) has a solubility of 1 g or less with respect to 100 g of water at 20 ° C., and the compound can be separated from the liquid phase by sedimentation separation or filtration. It means that there is.

Through the above treatment, the amount of chemicals added is suppressed as much as possible, and cyanide in wastewater can be removed safely and inexpensively with a simple operation regardless of the type of wastewater containing thiocyanate ions or ammonium ions. Cyanide concentration (total cyan content (mg / L)) can be significantly reduced below the wastewater standard value, and the wastewater after treatment can be discharged or reused as is to sewage without neutralization. it can.
In the method of the present invention, when the treated wastewater is discharged as it is, it is sufficient to add an amount of a compound necessary for lowering the total cyan concentration below the wastewater standard value, but the treated wastewater is diluted with other wastewater. In the case of discharge, the compound may be added so that the waste water after dilution is less than the above waste water reference value.
Usually, in a factory or the like, the treated wastewater is often diluted with other wastewater and discharged, and it is preferable to control the amount of each active ingredient added in consideration of the cost effect.
Therefore, when the total cyan density after processing does not become 1 mg / L or less, it is understood that the processing is also included in the present invention when it becomes approximately 5 mg / L or less.

The present invention will be specifically described with reference to test examples, but the present invention is not limited to these test examples.

In Test Example 1-1 below, cyan-containing wastewater A (pH 8.3) having water quality shown in Table 1 collected from a coke oven wastewater line at Sakai Steel Works was used.

In Test Example 1-2 below, cyan-containing wastewater B (pH 7.8) having water quality shown in Table 2 collected from raw water of blast furnace dust collected at Sakai Works was used.

In the following Test Examples 2-1, 2-3 and 2-4, cyan-containing wastewater C (pH 8.0) having the water quality shown in Table 3 prepared as follows was used.
Cyan-containing wastewater C was prepared using an aqueous potassium ferrocyanide solution, an aqueous potassium cyanide solution, an aqueous potassium thiocyanate solution, an aqueous calcium chloride dihydrate solution, an aqueous sodium chloride solution, an aqueous sodium sulfate solution, an aqueous ammonium chloride solution and an aqueous sodium hydrogen carbonate solution.

In Test Example 2-2 below, cyan-containing wastewater D (pH 8.0) having the water quality shown in Table 4 prepared as follows was used.
Cyan-containing wastewater D was prepared using an aqueous potassium cyanide solution, an aqueous calcium chloride dihydrate solution, an aqueous sodium chloride solution, an aqueous sodium sulfate solution, and an aqueous sodium hydrogen carbonate solution.

(Test Example 1-1)
300 mL of cyan-containing wastewater A was dispensed into a 300 mL capacity beaker, and sodium hypochlorite, manganese chloride, and hydrogen peroxide were added to the concentrations shown in Table 5 to obtain test water.
In some test waters, an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution was added to adjust the pH of the test water to the values shown in Table 5.
Next, the obtained test water was used with a stirrer (manufactured by Miyamoto Seisakusho Co., Ltd., jar tester (sample water agglomeration reactor), model: MJS-6, stirrer blade shape: two blades, stirrer blade maximum diameter 60 mm). And stirred for 30 minutes at 120 rpm.
Subsequently, the total cyan density | concentration (T-CN) in test water was measured based on JISK0102, and the removal effect of the cyanide compound in each test water was evaluated.
In this test, a blank test (Comparative Example 4) in which sodium hypochlorite, manganese chloride and hydrogen peroxide were not added was simultaneously performed.
The obtained results are shown in Table 5 together with the additive compound, its addition amount, and the pH of the test water.

The following can be seen from the test results in Table 5.
-Combined treatment of sodium hypochlorite and hydrogen peroxide at pH 7-9 (Examples 1-3), Combined treatment of sodium hypochlorite, manganese chloride, and hydrogen peroxide at pH 8 and 9 (Example 4) ~ 7) has a sufficient cyan removal effect. On the other hand, in the treatment using only sodium hypochlorite (Comparative Example 1), the cyan content of the treatment liquid is higher than in the blank (Comparative Example 4). (This is probably due to the oxidation of thiocyanate ions in wastewater to cyan)
-In the treatment by the alkali chlorine method (Comparative Example 2), sufficient cyan removal effect cannot be obtained despite the addition of an excessive amount of sodium hypochlorite.-Sodium hypochlorite and manganese chloride In the combination treatment with (Comparative Example 3), it was assumed that the effect of cyan removal was obtained, but the amount of chemical addition may be insufficient, and sufficient cyan removal effect cannot be obtained.

(Test Example 1-2)
1 L of cyan-containing waste water B was dispensed into a 1 L capacity beaker and heated in a water bath set at 55 ° C. Manganese chloride was added to a concentration shown in Table 6 and stirred for 2 minutes, and an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution was added to adjust the pH of the test water to 8.0.
Next, sodium hypochlorite was added to the obtained test water so as to have a concentration shown in Table 6, and a stirrer (manufactured by Miyamoto Seisakusho Co., Ltd., jar tester (sample water agglomeration reactor), model: MJS- 6. Stirring blade shape: 2 blades, stirring blade maximum diameter 60 mm) was used for stirring for 1 hour at 120 rpm.
The test water was adjusted so that the pH of the test water was 8.0 by adding an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution. The cyanide content (T-CN) and chemical oxygen demand (COD _Mn ) of the obtained test water (1) were measured.

Next, an inorganic flocculant (polyaluminum chloride) was added to the obtained test water (1) so as to be 3 mg / L, and the mixture was stirred for 2 minutes at a rotation speed of 200 rpm using a stirrer. Further, a polymer flocculant (product name: Floclan A-1240, manufactured by Katayama Chemical Industry Laboratory Co., Ltd.) was added so as to be 1 mg / L. The mixture was stirred at 60 rpm for 1 minute 30 seconds. The obtained test water was allowed to stand for 5 minutes, and then the appearance was observed.
Next, 250 mL of the supernatant of the obtained test water was collected, transferred to a 300 mL beaker, and heated in a water bath set at 55 ° C. The rest is No. Filtered with 5A filter paper.
Hydrogen peroxide is added to the obtained supernatant test water so as to have the concentration shown in Table 6, and an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution is added to adjust the pH of the test water to 8.0. The mixture was stirred for 2 hours at 120 rpm using a stirrer.
No. after stirring. The sample was filtered with 5A filter paper, and the cyan content (T-CN) and chemical oxygen demand (COD _Mn ) of test water (2) were measured.
Table 6 shows the obtained results.

The following can be seen from the test results in Table 6.
・ After the first stage treatment, the cyanide content (T-CN) decreased to about 3 mg / L and the chemical oxygen demand (COD _Mn ) also decreased. In Examples 8 and 9, hydrogen peroxide was added. After that, the cyan content (T-CN) was less than 1 mg / L

(Test Example 2-1 1-stage treatment test of cyanate-containing wastewater containing cyano complex)
Cyan-containing wastewater was used in the same manner as in Test Example 1, except that cyanogen-containing wastewater C was used as the cyanide-containing wastewater, and sodium hypochlorite, manganese chloride, and hydrogen peroxide were added to the concentrations shown in Table 7. C was processed.
In some test waters, an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution was added to adjust the pH of the test water to the values shown in Table 7.
Next, the water-insoluble product in the test water was filtered off, and the total cyan concentration (T-CN) in the filtrate was measured according to JIS K0102, and the removal effect of the cyanide compound in each test water was evaluated.
In this test, a blank test (Comparative Example 11) in which sodium hypochlorite, manganese chloride and hydrogen peroxide were not added was simultaneously performed.
The obtained results are shown in Table 7 together with the additive compound, its addition amount, and the pH of the test water.

The following can be seen from the test results in Table 7.
-When treated with an additive compound (Examples 10 to 16) having a pH of 6.5 to 9 using sodium hypochlorite, manganese chloride and hydrogen peroxide in combination (Examples 10 to 16). In addition, the treatment using only sodium hypochlorite at pH 8 (Comparative Example 5) and the treatment using only manganese chloride at pH 8 (Comparative Example 6) do not provide a sufficient cyan removal effect. It was assumed that the combined treatment of sodium hypochlorite and manganese chloride in Comparative Example 9 (Comparative Examples 7 to 9) would have the effect of removing cyanide, but the effect was not sufficient in this wastewater. The treatment using only hydrogen peroxide (Comparative Example 10) has almost no effect despite the addition of an excessive amount of hydrogen peroxide.

(Test Example 2-2 / One-stage treatment test of cyanide-containing wastewater containing cyanide ions)
Cyan-containing waste water D was used in the same manner as in Test Example 2-1, except that cyan-containing waste water D was used as the cyan-containing waste water, and sodium hypochlorite and hydrogen peroxide were added to the concentrations shown in Table 8. Processed.
In some test waters, an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution was added to adjust the pH of the test water to the values shown in Table 8.
Next, the water-insoluble product in the test water was filtered off, and the total cyan concentration (T-CN) in the filtrate was measured according to JIS K0102, and the removal effect of the cyanide compound in each test water was evaluated.
The obtained results are shown in Table 8 together with the additive compound, its addition amount, and the pH of the test water.

The following can be seen from the test results in Table 8.
-It has a sufficient cyan removal effect when treated with an additive compound of pH 8 (Examples 17 to 19) using sodium hypochlorite and hydrogen peroxide in combination.

(Test Example 2-3 / Two-stage test for cyanogen-containing wastewater containing cyano complex)
Dispense 300 mL of cyanide-containing waste water C into a 300 mL beaker, and add one or two selected from sodium hypochlorite, manganese chloride, and hydrogen peroxide to the concentrations shown in Table 9. The test water was obtained.
To some test waters, an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution was added to adjust the pH of the test water to the values shown in Table 9.
Next, the obtained test water was stirred for 30 minutes at a rotation speed of 120 rpm using the stirring device.
Next, the water-insoluble product in the test water was filtered off, and the filtrate (supernatant) was separated into a 200 mL beaker, and sodium hypochlorite, manganese chloride and One or two kinds selected from hydrogen peroxide were added, respectively, and stirred for 30 minutes at a rotation speed of 120 rpm using the stirring device.
Subsequently, the total cyan density | concentration (T-CN) in test water was measured based on JISK0102, and the removal effect of the cyanide compound in each test water was evaluated.
The obtained results are shown in Table 9 together with the additive compound, its addition amount, and the pH of the test water.

From the test results of Table 9, it can be seen that even when the chemical used in the method of the present invention is used in two stages, a sufficient cyan removal effect is exhibited.

(Test Example 2-4 / One-stage treatment test for cyanogen-containing wastewater containing cyano complex)
Cyanide-containing wastewater C was treated in the same manner as in Test Example 2-1, except that sodium hypochlorite, a metal compound, and hydrogen peroxide were added to the concentrations shown in Table 10. Regarding metal compounds, ferrous chloride tetrahydrate (Fe ²⁺ ), zinc chloride (Zn ²⁺ ), cuprous chloride (Cu ⁺ ), and cupric sulfate pentahydrate (Cu ^2+). ) Were used.
The obtained results are shown in Table 10 together with the additive compound, its addition amount, and the pH of the test water.

The following can be seen from the test results in Table 10.
In the case of treating with sodium hypochlorite, a specific metal compound (a compound capable of forming a divalent iron ion in water and a copper compound) and an additive compound (Examples 27 to 32) using hydrogen peroxide in combination Have sufficient cyan removal effect.

Claims

Hypochlorite and hydrogen peroxide are added to cyanide-containing wastewater simultaneously or separately to cause decomposition of cyanide in the wastewater and / or formation of water-insoluble compounds with cyanide. Of treating wastewater containing cyanide comprising removing water.
Cyan content in the cyan-containing wastewater is measured in advance, and 0.1 mol equivalent or more of the hydrogen peroxide and 0.1 mol equivalent of the hypochlorite as an effective chlorine concentration with respect to the measured content The processing method of the cyanate containing wastewater of Claim 1 added above.
The method for treating cyan-containing wastewater according to claim 1 or 2, wherein the cyan-containing wastewater originally contains one or more metal ions selected from manganese ions, iron ions, and copper ions.
The method for treating cyanide-containing wastewater according to any one of claims 1 to 3, wherein one or more metal compounds selected from manganese compounds, iron compounds and copper compounds are further added.
The method for treating cyanide-containing wastewater according to any one of claims 1 to 4, wherein the cyanide-containing wastewater has a pH of 9 or less.