JP2023093640A - Treatment method and treatment installation of cyan-containing water - Google Patents

Abstract

To provide a treatment method of cyan-containing water capable of stably and sufficiently conducting removal treatment of a cyan component from water to be treated even in a case where a cyanide ion concentration and an iron cyano-complex concentration in the water to be treated vary.SOLUTION: A treatment method of cyan-containing water includes: a step (A) of adding hydrogen peroxide to water to be treated containing a cyanide ion and an iron cyano-complex, followed by reacting; a step (B2) of bringing hydrogen peroxide remover into contact with a reaction liquid obtained by the step (A), followed by reacting to decrease a concentration of the hydrogen peroxide residing in the reaction liquid; a step (C) of adding a copper (I) compound to the reaction liquid obtained by the step (B2), followed by reacting; and a step (D) of conducting solid-liquid separation treatment of the reaction liquid obtained by the step (C).SELECTED DRAWING: None

Description

The present invention relates to a cyanogen-containing water treatment method and a cyanide-water treatment facility.

As a treatment method for removing cyanide components from wastewater containing cyanide components such as cyanide ions, an alkali chlorine method for oxidatively decomposing the cyanide components in wastewater is widely applied. In the alkaline chlorine method, sodium hypochlorite is generally added to cyanide-containing wastewater under alkaline conditions to remove cyanide ions and easily decomposable cyano complexes (cyano complexes of zinc, copper, etc.) in the wastewater. Can be oxidatively decomposed.

On the other hand, in the alkali chlorine method, it is difficult to decompose refractory cyano complexes such as iron cyano complexes. A method of separating and removing by a precipitation method (sparingly soluble salt precipitation method) has also been proposed. In addition, in Patent Document 1, wastewater containing complex cyanide is allowed to coexist with a specific cuprous compound and hydrogen peroxide under conditions of pH 6 to 9, and water-insoluble salts generated in the wastewater are removed. , a method for treating complex cyanogen-containing wastewater has been proposed.

JP 2017-80699 A

With reference to the method proposed in Patent Document 1, the present inventors added hydrogen peroxide and a copper (I) compound to various waters to be treated containing cyanide ions and iron cyano complexes with different concentrations. As a result, it was found that the cyanide component could not be sufficiently removed depending on the water to be treated.

Therefore, according to the present invention, even when the concentration of cyanide ions and the concentration of the iron cyano complex in the water to be treated varies, it is possible to stably and sufficiently remove the cyanide component from the water to be treated. It is an object of the present invention to provide a possible method for treating cyanide-containing water.

As described above, the present inventors conducted a beaker test in which hydrogen peroxide and a copper (I) compound coexist in various waters containing cyanide ions and iron cyano complexes. We investigated in detail the cause of the problem that the removal performance of cyanide components from treated water was degraded. Specifically, for the water to be treated in which such problems have occurred, the properties of the water to be treated are analyzed, and when hydrogen peroxide and a copper (I) compound are added to the water to be treated at the same time, excess The above cause was investigated by examining the difference in treatment performance from the case where the copper (I) compound was added after the addition of hydrogen oxide. As a result, when a copper (I) compound is added to the water to be treated, if a relatively large amount of hydrogen peroxide remains in the water to be treated, the ability to remove cyanide components from the water to be treated tends to decrease. I found out.

Based on these findings, the present inventors discovered that when a copper (I) compound is added to the reaction solution after hydrogen peroxide has been added to the water to be treated and reacted, residual hydrogen peroxide in the reaction solution The present inventors have completed the present invention based on the belief that the above-mentioned problems can be solved if the concentration is sufficiently low or if residual hydrogen peroxide can be substantially eliminated.

That is, the present invention includes a step (A) of adding hydrogen peroxide to water to be treated containing cyanide ions and an iron cyano complex to react, and residual in the reaction solution obtained in the step (A) a step (B1) of measuring the concentration of the hydrogen peroxide, a step (C) of adding a copper (I) compound to the reaction solution obtained in the step (A) and reacting it, and the step ( A step (D) of subjecting the reaction solution obtained in C) to solid-liquid separation treatment, wherein the amount of hydrogen peroxide added to the water to be treated in the step (A) is determined in the step (B1) Provided is a method for treating cyanide-containing water, which controls the measured hydrogen peroxide concentration to 10 mg-H ₂ O ₂ /L or less.

Further, the present invention includes a step (A) of adding hydrogen peroxide to water to be treated containing cyanide ions and an iron cyano complex to react, the reaction solution obtained in the step (A), and A step (B2) of contacting and reacting with a hydrogen peroxide removing agent that reduces the concentration of the hydrogen peroxide remaining in the reaction solution, and adding copper (I) to the reaction solution obtained in the step (B2) Provided is a method for treating cyanide-containing water, comprising a step (C) of adding and reacting a compound, and a step (D) of subjecting the reaction liquid obtained in the step (C) to solid-liquid separation treatment.

According to the present invention, even when the concentration of cyanide ions and the concentration of the iron cyano complex in the water to be treated varies, the cyanide component capable of stably and sufficiently removing the cyanide component from the water to be treated is used. A method for treating contained water can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing showing an example of schematic structure of the processing equipment which can perform the processing method of the cyanide-containing water of 1st embodiment of this invention, and a processing flow. FIG. 4 is an explanatory diagram showing an example of a schematic configuration of a treatment facility and a treatment flow capable of executing the cyanogen-containing water treatment method of the second embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a schematic configuration of an example of an exhaust gas treatment facility and a treatment flow on the assumption that a method for treating cyanide-containing water according to an embodiment of the present invention is applied;

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

With reference to the method proposed in Patent Document 1, the present inventors added hydrogen peroxide and a copper (I) compound to various waters to be treated containing cyanide ions and iron cyano complexes with different concentrations. A beaker test was conducted in which the coexistence of As a result, it has been found that, depending on the water to be treated, the problem arises that the cyanide component cannot be sufficiently and effectively removed from the water to be treated.

The iron cyano complex refers to a complex containing Fe and CN. Iron cyano complexes include ferrocyanide ion ([Fe(CN) ₆ ] ⁴⁻ ; hexacyanoferrate(II) ion) and ferricyanide ion ([Fe(CN) ₆ ] ³⁻ ; hexacyanoferrate(III) acid ion), and iron carbonyl cyano complexes ([Fe(CN) ₅ (CO)] ^3- and [Fe(CN) ₄ (CO) ₂ ] ^2- ).

Regarding the cause of the above problem, the present inventors analyzed the properties of the water to be treated in which the problem occurred, and found that when hydrogen peroxide and a copper (I) compound were added simultaneously to the water to be treated, or when hydrogen peroxide and a copper (I) compound were added to the water. A study was conducted by confirming the difference in treatment performance from the case where the copper (I) compound was added after adding hydrogen. In the study, it was found that the above-mentioned problems are less likely to occur, for example, when both the concentration of cyanide ions and the concentration of iron cyano complexes in the water to be treated are low. On the other hand, it has been found that, for example, when the iron cyano complex concentration is higher than the cyanide ion concentration in the water to be treated, the above-mentioned problems tend to occur. Further, the iron cyano complex contained in the water to be treated contains ferrocyanide ions and/or ferricyanide ions, and [Fe(CN) ₅ (CO)] ^3- and/or [Fe(CN ) ₄ (CO) ₂ ] ^2- , it was found that the above-mentioned problems tend to occur. As described above, it has been found that even if the amount of hydrogen peroxide or copper(I) compound added is adjusted according to the properties of the water to be treated, the treatment performance differs.

Generally, in actual cyanide-containing wastewater (water to be treated), the concentration of cyanide components such as cyanide ions and iron cyano complexes in the wastewater fluctuates every moment. Therefore, in an actual wastewater treatment facility, if the cyanide-containing wastewater is treated in the presence of hydrogen peroxide and a copper (I) compound, depending on the cyanide-containing wastewater flowing into the wastewater treatment facility, It is considered that the cyan component removal performance may deteriorate. In an actual wastewater treatment facility, when cyanide-containing wastewater, which is unlikely to cause the above-mentioned problems, continues, the treatment is continued without noticing the problem. If cyanogen-containing wastewater comes in, it can cause confusion.

Therefore, regardless of whether or not the above problems are likely to occur, the cyanide component can be removed from the water to be treated even when the concentration of cyanide ions and the concentration of the iron cyano complex in the water to be treated varies. A method that allows stable and sufficient processing would be useful in practice.

The inventors of the present invention conducted investigations to find out the cause of the above problem, and found that relatively large amounts of hydrogen peroxide were present in the water to be treated when a copper (I) compound was added to the water to be treated. It was found that the removal performance of the cyanide component from the water to be treated tends to decrease when the Based on these findings, the present inventors discovered that when a copper (I) compound is added to the reaction solution after hydrogen peroxide has been added to the water to be treated and reacted, residual hydrogen peroxide in the reaction solution The present invention has been completed based on the idea that the above-mentioned problems can be solved if the concentration is sufficiently low or if the residual hydrogen peroxide can be substantially eliminated.

<Method for treating water containing cyanide>
The method for treating cyanide-containing water according to the first embodiment of the present invention comprises a step (A) of adding hydrogen peroxide to the water to be treated containing cyanide ions and an iron cyano complex to cause a reaction; A step (B1) of measuring the concentration of hydrogen peroxide remaining in the reaction solution obtained in A), and adding a copper (I) compound to the reaction solution obtained in the above step (A) for reaction. The step (C) and the step (D) of subjecting the reaction liquid obtained in the step (C) to solid-liquid separation treatment, wherein the amount of hydrogen peroxide added to the water to be treated in the step (A) is The amount is controlled so that the hydrogen peroxide concentration value measured in the step (B1) is 10 mg-H ₂ O ₂ /L or less.

In addition, the method for treating cyanide-containing water according to the second embodiment of the present invention includes a step (A) of adding hydrogen peroxide to the water to be treated containing cyanide ions and an iron cyano complex to cause a reaction, and a step (B2) of bringing the reaction solution obtained in step (A) into contact with a hydrogen peroxide removing agent that reduces the concentration of hydrogen peroxide remaining in the reaction solution, and reacting the reaction solution (B2); A step (C) of adding a copper (I) compound to the reaction solution obtained in step (C) for reaction, and a step (D) of subjecting the reaction solution obtained in step (C) to solid-liquid separation treatment It is in.

According to the method for treating cyanide-containing water of the above first and second embodiments (hereinafter collectively referred to simply as "this embodiment"), first, cyanide ions and an iron cyano complex are The step (A) of adding and reacting hydrogen peroxide to the water to be treated containing (hereinafter sometimes simply referred to as "water to be treated") is performed. As a result, hydrogen peroxide undergoes an oxidation reaction with cyanide ions (CN ⁻ ) in the water to be treated, and the cyanide ions can be decomposed. If the water to be treated contains, in addition to ^CN- , easily decomposable cyano complexes such as zinc cyano complexes, nickel cyano complexes, and copper cyano complexes, such cyano complexes are also included in the process ( A) can be expected to decompose. The reaction time in step (A) is preferably 3 to 60 minutes, more preferably 5 to 30 minutes. The reaction temperature in step (A) is preferably 15 to 80°C, more preferably 35 to 60°C.

Further, in the treatment method of the present embodiment, the reaction solution obtained in the step (A) or the reaction solution obtained in the step (B2) is reacted by adding a copper (I) compound to the step (C). )I do. As a result, the iron cyano complex present in the water to be treated is made sparingly soluble, and a sparingly soluble iron cyano complex can be produced in the reaction solution. The reaction time in step (C) is preferably 3 to 60 minutes, more preferably 5 to 30 minutes. The reaction temperature in step (C) is preferably 15 to 80°C, more preferably 35 to 60°C.

The poorly soluble substances that can be produced in the step (C) can be separated and removed by the step (D) of subjecting the reaction solution obtained in the step (C) to a solid-liquid separation treatment. In addition, by this step (D), treated water from which cyan components have been removed can be obtained.

As described above, in the treatment method of the present embodiment, before adding the copper (I) compound to the water to be treated, the step (A) of adding hydrogen peroxide to the water to be treated and reacting it is performed. I) When a sparingly soluble substance is produced by adding a compound, the amount of cyanide contained in the sparingly soluble substance can be appropriately reduced. Therefore, since the amount of cyanide contained in the poorly soluble substance is reduced, it also leads to the advantage of being able to reduce the possibility and degree of elution of cyanide when disposing of the poorly soluble substance.

(First embodiment)
Then, in the treatment method of the first embodiment, the amount of hydrogen peroxide added to the water to be treated in the step (A) is measured in the step (B1) and obtained in the step (A). The concentration of hydrogen peroxide in the reaction solution is controlled to 10 mg-H ₂ O ₂ /L or less. As a result, when the copper (I) compound is added to the reaction solution after hydrogen peroxide has been added to the water to be treated and reacted, the concentration of residual hydrogen peroxide in the reaction solution can be kept sufficiently low. . Therefore, even when the concentration of cyanide ions and the concentration of the iron cyano complex in the water to be treated varies, it is possible to stably and sufficiently remove the cyanide component from the water to be treated.

In the treatment method of the first embodiment, while confirming the value of the hydrogen peroxide concentration measured in step (B1), until the value is 10 mg-H ₂ O ₂ /L or less, the treated in step (A) The amount of hydrogen peroxide added to the water can be adjusted. Therefore, effective treatment by adding hydrogen peroxide to the water to be treated can be more reliably performed, and the efficiency of treatment by oxidative decomposition of cyanide ions in the water to be treated can be enhanced.

The amount of hydrogen peroxide added to the water to be treated in step (A) is such that the concentration of hydrogen peroxide measured in step (B1) is preferably 5 mg-H ₂ O ₂ /L or less, more preferably 3 mg. It is preferable to control the amount to -H ₂ O ₂ /L or less. As a result, the concentration of residual hydrogen peroxide in the reaction solution when the copper (I) compound is added can be kept sufficiently low, so that the removal of cyanide components from various types of water to be treated can be performed more stably and sufficiently. easier to go to The lower limit of the value of the hydrogen peroxide concentration measured in step (B1) is 0.1 mg-H ₂ It is preferably O ₂ /L or more, more preferably 0.5 mg-H ₂ O ₂ /L or more.

The measurement of the hydrogen peroxide concentration in step (B1) may be performed in a batch system or in a continuous system. By adding hydrogen peroxide to the water to be treated in step (A) while monitoring the value of hydrogen peroxide concentration measured in step (B1), while confirming the measured value of hydrogen peroxide concentration, This is preferable because it is easy to adjust the amount of hydrogen peroxide added to the water to be treated in step (A). From the viewpoint of facilitating the adoption of such a method, it is preferable to continuously measure the concentration of hydrogen peroxide remaining in the reaction solution obtained in step (A) in step (B1). Monitoring of the hydrogen peroxide concentration value measured in step (B1) can also be performed by intermittent measurement (at predetermined intervals) in a batch manner.

(Second embodiment)
Then, in the treatment method of the second embodiment, before adding the copper (I) compound to the reaction solution obtained in the step (A), the reaction solution obtained in the step (A) and the A step (B2) of contacting and reacting with a hydrogen peroxide removing agent that reduces the concentration of hydrogen peroxide remaining in the reaction solution is carried out. As a result, the concentration of residual hydrogen peroxide in the reaction solution to which the copper(I) compound is added (the reaction solution that has undergone step (A)) can be brought to a sufficiently low level. Therefore, even when the concentration of cyanide ions and the concentration of the iron cyano complex in the water to be treated varies, it is possible to stably and sufficiently remove the cyanide component from the water to be treated.

In step (B2), the reaction solution obtained in step (A) is brought into contact with the hydrogen peroxide removing agent. Often, the hydrogen peroxide removing agent may be brought into contact with the reaction liquid obtained in step (A), or both of them may be carried out. The reaction time in step (B2) is preferably 1 to 30 minutes, more preferably 1 to 15 minutes. The reaction temperature in step (B2) is preferably 15 to 80°C, more preferably 35 to 60°C.

In the second embodiment, the reaction solution obtained in step (A) is brought into contact with a hydrogen peroxide remover to react with the reaction solution (B2), whereby the excess in the reaction solution obtained in step (A) is removed. Since the concentration of hydrogen oxide can be reduced, the amount of hydrogen peroxide added to the water to be treated in step (A) is not particularly limited. The amount of hydrogen peroxide to be added in this step (A) can be an amount sufficient to treat cyanide ions in the water to be treated by oxidative decomposition or the like. The amount of hydrogen peroxide added is, for example, preferably 10 to 300 mg-H ₂ O ₂ /L, more preferably 10 to 200 mg-H ₂ O ₂ /L, and more preferably 10 to 100 mg-H _{2 .} More preferably, it is O ₂ /L.

In the treatment method of the second embodiment, the concentration of hydrogen peroxide remaining in the reaction solution obtained in step (A) is measured in the same manner as step (B1) in the treatment method of the first embodiment. It is preferable to further include the step (B1) of If the value of the hydrogen peroxide concentration measured in this step (B1) is 10 mg-H ₂ O ₂ /L or less, the above step (B2) can be omitted. The processing method of the embodiment can be adopted. For this reason, the step (B2) is particularly significant when the value of the hydrogen peroxide concentration measured in the step (B1) exceeds 10 mg-H ₂ O ₂ /L. It is also quite significant to carry out the step (B2) when the hydrogen peroxide concentration value measured in the step (B1) is 0.1 to 10 mg-H ₂ O ₂ /L. The step (B2) can further reduce the hydrogen peroxide concentration in the reaction solution to which the copper (I) compound is added in the step (C), thereby removing the cyanide component from various waters to be treated. is more stable and sufficiently easy to perform.

Moreover, the treatment method of the second embodiment preferably further includes a step (B3) of measuring the concentration of hydrogen peroxide remaining in the reaction solution obtained in step (B2). Through this step (B3), the effect of reducing the hydrogen peroxide concentration by the hydrogen peroxide remover in step (B2) can be confirmed. Further, by the step (B3), the value of the hydrogen peroxide concentration measured in the step (B3) is 10 mg-H ₂ O ₂ /L or less (preferably 5 mg-H 2 O 2 /L or less, more preferably 3 mg-H ₂ O ₂ /L or less). H ₂ O ₂ /L or less), the amount of the hydrogen peroxide remover used in step (B2) can be adjusted.

The measurement of the hydrogen peroxide concentration in the step (B3) may be performed either batchwise or continuously, as in the step (B1) described above. While monitoring the value of the hydrogen peroxide concentration measured in step (B3), in step (B2), if the reaction solution obtained in step (A) is brought into contact with a hydrogen peroxide remover, peroxide It is preferable because it is easy to adjust the amount of the hydrogen peroxide remover while confirming the effect of the hydrogen remover. From the viewpoint of facilitating the adoption of such a method, it is preferable in step (B3) to continuously measure the concentration of hydrogen peroxide remaining in the reaction solution obtained in step (B2). Monitoring of the hydrogen peroxide concentration value measured in the step (B3) can also be carried out intermittently (at predetermined intervals) in a batch manner.

In the processing method of the second embodiment, when performing the above-described steps (B1) and (B3), it is also possible to measure the hydrogen peroxide concentration in each step using the same measuring device at the same place. be. In addition, the hydrogen peroxide concentration in steps (B1) and (B3) can be measured continuously in steps (B1) and (B3), and in steps (B1) and (B3) It is also possible to carry out successively without distinction.

The hydrogen peroxide removing agent used in step (B2) in the treatment method of the second embodiment preferably contains either one or both of a hydrogen peroxide reducing agent and a hydrogen peroxide decomposition catalyst. Examples of reducing agents for hydrogen peroxide include sulfites such _as sodium sulfite ( _{Na 2} SO ₃ ) and potassium sulfite (K ₂ SO ₃ ); Hydrogen sulfite (also known as bisulfite); iron (II) salts such as iron (II) sulfate and iron (II) nitrate (also known as divalent iron salts and ferrous salts); ascorbic acid and its salts, etc. can be mentioned. When using such a hydrogen peroxide reducing agent as the hydrogen peroxide removing agent, the hydrogen peroxide removing agent (hydrogen peroxide reducing agent) is added to the reaction solution obtained in step (A). Therefore, it is preferable to bring a hydrogen peroxide removing agent into contact with the reaction solution obtained in step (A). The form in which the hydrogen peroxide reducing agent is added may be in the form of a powder or a solution dissolved in a solvent, and the form of a solution is preferred.

As the hydrogen peroxide decomposition catalyst, a liquid decomposition catalyst or a solid decomposition catalyst can be used. Examples of liquid decomposition catalysts include catalase and activated sludge used in sewage treatment plants. Examples of solid decomposition catalysts include powdery or granular manganese dioxide and granular or pelletized activated carbon. When the hydrogen peroxide decomposition catalyst as described above is used as the hydrogen peroxide removing agent, the hydrogen peroxide removing agent (hydrogen peroxide decomposition catalyst) is added to the reaction solution obtained in step (A). It is preferable to bring a hydrogen peroxide removing agent into contact with the reaction solution obtained in step (A). Alternatively, a hydrogen peroxide decomposition catalyst supported on a base material may be immersed in the reaction liquid, or a solid decomposition catalyst may be processed into a fibrous or mesh shape and immersed in the reaction liquid. , The reaction solution obtained in step (A) is brought into contact with the hydrogen peroxide removing agent (hydrogen peroxide decomposition catalyst) by passing the reaction solution through a tank filled with a solid decomposition catalyst. is also preferred.

Next, a preferred configuration common to the processing method of the first embodiment and the processing method of the second embodiment will be described.

As the water to be treated that is suitable for the treatment method of the present embodiment, as described above, the water to be treated that has a higher iron cyano complex concentration than the cyanide ion concentration can be mentioned. Further, as suitable water to be treated, the iron cyano complex contained in the water to be treated contains either one or both of ferrocyanide ions and ferricyanide ions, and [Fe(CN) ₅ (CO) ] ^3- and [Fe(CN) ₄ (CO) ₂ ] ^2- , or those containing both. Wastewater containing an iron carbonyl cyano complex is disclosed, for example, in JP-A-2018-39004 and JP-A-2018-69227.

The iron carbonyl cyano complex is an environment in which an iron carbonyl complex such as pentacarbonyl iron (Fe(CO) ₅ ) coexists with hydrogen cyanide (HCN) or CN ⁻ ; iron (II) ion (Fe ²⁺ ), carbon monoxide (CO) and HCN or ^CN- coexisting environment; [Fe(CN) ₆ ] ^4- and CO co-existing environment; and the like. For example, in the wastewater discharged from a plating factory, although ^CN- and iron salts may coexist, it is unlikely that CO or pentacarbonyl iron will be present, and the environment described above is rare. It is considered to be Therefore, it is considered that conventional techniques for treating cyanide-containing water rarely treat iron carbonyl cyano complexes that can be generated from the environment as described above. A study by the present inventors confirmed that pentacarbonyl iron was contained in the exhaust gas generated from a coke-fueled furnace, and it was found that it could vary greatly depending on the operating conditions of the furnace. rice field. Since pentacarbonyl iron is said to have the property of starting to decompose in a low temperature range of 100° C. or less, it is considered that the content of pentacarbonyl iron in the exhaust gas fluctuates depending on the temperature distribution in the furnace. There is a possibility that one of the controlling factors in this temperature distribution is the property of coke (and the property of coal, which is the raw material for coke). In view of the above, one example of suitable water to be treated is waste water for cleaning exhaust gas. An example of a more suitable water to be treated is dust-collected water obtained by wet-type dust collection treatment of exhaust gas containing suspended solids, and discharged water that has been subjected to solid-liquid separation treatment for removing suspended solids. Gas wash wastewater may be mentioned.

In the treatment method of the present embodiment, the pH of the liquid to be treated during treatment in each step is preferably 5 to 10, more preferably 5.5 to 9.5, and even more preferably 6 to 8. You may adjust pH of the process target liquid in each process. At that time, for example, pH adjusters such as hydrochloric acid and sodium hydroxide can be used.

The copper (I) compound used in step (C) in the treatment method of the present embodiment is a monovalent copper compound (cuprous compound). Examples of copper (I) compounds include copper (I) chloride, copper (I) oxide (cuprous oxide), and copper (I) sulfate. One or more of these copper (I) compounds can be used. The form of the copper (I) compound when adding the copper (I) compound may be a powder form or a solution form dissolved in a solvent, and a solution form is preferred. In step (C) of the present embodiment, cuprous oxide (copper(I) oxide) is more preferably used as the copper(I) compound.

In the step (D) of solid-liquid separation treatment of the reaction solution obtained in the step (C), as described above, if a poorly soluble iron cyano complex is produced by the addition of the copper (I) compound, it is separated. can be removed. If the water to be treated or the reaction solution obtained in step (C) contains other suspended solids (SS), the SS can be removed in step (D). Methods of solid-liquid separation treatment in the step (D) include precipitation treatment, membrane separation treatment, filtration treatment, etc. Among these, precipitation treatment is preferred. During the solid-liquid separation treatment, a flocculant may be added to the reaction liquid to be subjected to the solid-liquid separation treatment. Examples of the flocculant include inorganic flocculants such as polyaluminum chloride, aluminum sulfate, polyferric sulfate, and ferric chloride, and polymer flocculants. The above can be used.

When the method for treating cyanide-containing water of the present embodiment is applied to the cleaning wastewater of the exhaust gas obtained by the solid-liquid separation treatment of the dust collection water, the treatment method includes the following steps (E) and ( F) is preferably included. That is, for the slurry containing the solid content separated from the liquid content in the step (D), the step (E) of performing either one or both of the concentration treatment and the dehydration treatment, and the separated water obtained in the step (E) is sent to the solid-liquid separation treatment for obtaining waste water for cleaning the exhaust gas (F). The slurry containing solids obtained in step (D) contains poorly soluble substances and the like that may be generated by the above step (C), and the water content in the slurry is affected by oxidation, pH change, temperature change, etc. There is a possibility that the cyan component will be eluted. On the other hand, by carrying out the steps (E) and (F), it is possible to more stably remove the cyan component from the water to be treated. Examples of the solid-liquid separation treatment for removing suspended matter from the collected water obtained by wet dust collection treatment of the exhaust gas containing suspended matter include sedimentation separation treatment, membrane separation treatment, and filtration treatment. Among these, sedimentation separation treatment is preferred.

In the treatment method of the present embodiment, either the water to be treated to which hydrogen peroxide is added in the step (A) or the reaction liquid to which the copper (I) compound is added in the step (C), or It is preferred to add a reducing agent to both as well. Examples of reducing agents include thiosulfates, sulfites, bisulfites, ferrous chloride, and alkali metal sulfides such as sodium sulfide and sodium tetrasulfide. The above can be used. Examples of salt-forming cations in thiosulfate, sulfite, and bisulfite include sodium ion, potassium ion, calcium ion, ammonium ion, and organic ammonium ion. Examples of the form of the reducing agent to be added to the water to be treated include a powder form and a solution form dissolved in a solvent, and a solution form is preferred.

In the treatment method of the present embodiment, it is preferable to further add a quaternary ammonium compound to the reaction solution to which the copper (I) compound is added in step (C). A quaternary ammonium compound is a compound having a quaternary ammonium cation and may be monomeric or polymeric. As the quaternary ammonium compound, tetraalkylammonium compounds, cationic polymers, and the like can be suitably used. The quaternary ammonium compound may be added in the form of a powder or a solution dissolved in a solvent, and the form of a solution is preferred.

Preferred tetraalkylammonium compounds are didecyldimethylammonium salts, hexadecyltrimethylammonium salts, dioctyldimethylammonium salts, didodecyldimethylammonium salts, trioctylmethylammonium salts, and benzyldodecyldimethylammonium salts. Furthermore, the anion paired with the quaternary ammonium cation in these is preferably a halide ion, more preferably a chloride ion and a bromide ion.

The cationic polymer may be any polymer having a quaternary ammonium cation. Examples include salt-acrylamide copolymer compounds, polycondensates of dimethylamine and epichlorohydrin, and polycondensates of dimethylamine, epichlorohydrin and ammonia.

In the treatment method of the present embodiment, the step (A) using hydrogen peroxide and the step (C) using a copper(I) compound may be performed in a common reaction tank or in separate reaction tanks. good too. For example, in the treatment method of the first embodiment described above, when step (A) and step (C) are performed in a common reaction tank, hydrogen peroxide is added and hydrogen peroxide is added in the common reaction tank. Measurement of residual hydrogen peroxide concentration and addition of a copper (I) compound to the reaction solution obtained after the reaction of (1) can be carried out. Since it is preferable to proceed to the next step after the reaction with hydrogen peroxide in step (A) is completed (more preferably after hydrogen peroxide is consumed by the reaction), step (A) and step ( C) is preferably carried out in separate reactors.

Further, in the processing method of the second embodiment described above, when the hydrogen peroxide removing agent is added in the step (B2), the step (A) of adding hydrogen peroxide and the removal of hydrogen peroxide The step (B2) of adding the agent may be performed in a common tank. Similarly, in this case, the step (B2) of adding the hydrogen peroxide remover and the step (C) of adding the copper (I) compound may be carried out in a common tank, and these steps (A), (B2) and (C) may be carried out in a common tank, or may be carried out in separate tanks. For example, in the treatment method of the second embodiment described above, when the step (A) and the step (B2) are performed in a common tank, hydrogen peroxide is added and a hydrogen peroxide remover is added in the common tank. It is possible to measure the concentration of residual hydrogen peroxide in the reaction solution after the addition and, if necessary, the reaction with hydrogen peroxide or after the reaction with the hydrogen peroxide remover. When step (B2) and step (C) are performed in a common tank, the common tank is used to add a hydrogen peroxide remover, add a copper (I) compound, and, if necessary, peroxide It is possible to measure the concentration of residual hydrogen peroxide in the reaction solution before adding the hydrogen removing agent or after the reaction with the hydrogen peroxide removing agent. When step (A), step (B2), and step (C) are performed in a common tank, addition of hydrogen peroxide, addition of hydrogen peroxide remover, addition of copper (I) compound, and if necessary Accordingly, it is possible to measure the concentration of residual hydrogen peroxide in the reaction liquid after the reaction with hydrogen peroxide or after the reaction with the hydrogen peroxide remover. It is preferable to proceed to the next step after completing the reaction with hydrogen peroxide in step (A), and to proceed to the next step after completing the reaction with the hydrogen peroxide remover in step (B2). It is preferred that step (A), step (B2) and step (C) are carried out in separate tanks.

Hereinafter, each step in the cyanogen-containing water treatment method of the first embodiment and the second embodiment will be further described with reference to the drawings showing the schematic configuration of the treatment equipment and treatment flow that can perform these treatment methods. state. In addition, the same code|symbol is attached|subjected about the part which is common in each figure in drawing, and the description may be abbreviate|omitted. 1 and 2 represent water to be treated and its treatment process.

FIG. 1 is an explanatory diagram showing an example of a schematic configuration of a treatment facility and a treatment flow capable of executing the cyanogen-containing water treatment method of the first embodiment described above. As shown in FIG. 1, the treatment facility 10 includes a first reaction tank (a) 11, a hydrogen peroxide concentration measuring device (b1) 13, a second reaction tank (c) 12, a solid-liquid separation device (d ) 16 and a control unit 17 . The above step (A) is performed in the first reaction tank (a) 11, the above step (B1) is performed in the measuring device (b1) 13, and the above step (B) is performed in the second reaction tank (c) 12. C) can be subjected to the above step (D) in the solid-liquid separator (d) 16 . Descriptions of (a), (b1), (c), and (d) are omitted below.

The first reaction tank 11 is a tank in which hydrogen peroxide is added to the water to be treated W ₁₀ that has flowed in and reacted. The first reaction vessel 11 can be provided with a device (hydrogen peroxide addition device) 111 for adding hydrogen peroxide. The second reaction tank 12 is a tank in which a copper (I) compound is added to the reaction solution W11 obtained in the first reaction tank ₁₁ and reacted. The second reaction tank 12 can be provided with a device (copper (I) compound addition device) 121 for adding a copper (I) compound. The solid-liquid separation device 16 is a device for solid-liquid separation of the reaction liquid W ₁₂ obtained in the second reaction tank 12 . As the solid-liquid separation device 16, for example, a sedimentation device such as a thickener, various filters, membrane separators, and the like can be used. When a flocculant is used in the treatment by the solid-liquid separator 16, the solid-liquid separator 16 may be provided with a device for adding the flocculant (flocculant addition device). The hydrogen peroxide addition device 111, the copper (I) compound addition device 121, and the coagulant addition device, for example, are equipped with a tank for storing each material, and a pump and supply pipe for supplying each material. can be done. The treatment facility 10 may have a relay tank between the second reaction tank 12 and the solid-liquid separator 16 or the like.

In the step (A), when a reducing agent such as the thiosulfate described above is used together with hydrogen peroxide, the first reaction tank 11 is provided with a device for adding the reducing agent to the first reaction tank 11 ( reducing agent addition device) can be provided. Further, in the step (C), when the reducing agent described above or the quaternary ammonium compound described above is used together with the copper (I) compound, the second reaction tank 12 includes a reducing agent addition device and a second reaction A device may be provided for adding the quaternary ammonium compound to the vessel.

The hydrogen peroxide concentration measuring device 13 is a device for measuring the concentration of hydrogen peroxide remaining in the reaction liquid W ₁₁ obtained in the first reaction tank 11 . The hydrogen peroxide concentration measuring device 13 can be either a batch-type measuring device or a continuous-type measuring device, and a continuous-type measuring device is more preferable. As a batch-type measuring device, for example, trade names "RQ Flex" and "Reflectquant Peroxide Test" (manufactured by Kanto Kagaku Co., Ltd.) can be used. As a continuous measuring device, for example, a trade name “Q46/84 type hydrogen peroxide meter” (manufactured by ATI) can be used.

The control unit 17 controls the amount of hydrogen peroxide added to the water W ₁₀ to be treated in the first reaction tank 11 so that the hydrogen peroxide concentration value measured by the hydrogen peroxide concentration measuring device 13 is 10 mg-H _{2 .} The amount is controlled to be O ₂ /L or less. From the viewpoint of facilitating this control, the control unit 17 preferably cooperates with the hydrogen peroxide concentration measuring device 13 and the first reaction tank 11 (the hydrogen peroxide adding device 111 provided therein). For example, when the hydrogen peroxide concentration value measured by the measuring device 13 is within a predetermined range (for example, a range of 0 to 5 mg-H ₂ O ₂ /L), the hydrogen peroxide adding device 111 (injection pump) is activated. , the measuring device 13 and the hydrogen peroxide addition device 111 (injection pump) are interlocked by the control unit 17 so that the hydrogen peroxide addition device 111 (injection pump) is stopped when the upper limit value of the predetermined range is exceeded. can be done. The control unit 17 can be configured to include, for example, a power supply unit, a CPU unit, an input unit, an output unit, a storage unit, etc., and can use a personal computer.

In FIG. 1, the first reaction vessel 11 and the second reaction vessel 12 are separated to facilitate the explanation of the step (A) using hydrogen peroxide and the step (C) using a copper(I) compound. Although shown separately, the first reactor 11 and the second reactor 12 may be the same (common) reactor. On the other hand, it is preferable to proceed to the next step after completing the reaction with hydrogen peroxide in step (A) (more preferably after hydrogen peroxide is consumed by the reaction), so the first reaction vessel 11 and second reaction tank 12 are preferably separate tanks. In order to facilitate the explanation of the step (B1) of measuring the concentration of hydrogen peroxide remaining in the reaction solution obtained in the step (A), in FIG. Although it is provided between the first reaction vessel 11 and the second reaction vessel 12 (the flow path between them), it may be installed in the first reaction vessel 11, and may be installed in the common reaction vessel. may

FIG. 2 is an explanatory diagram showing an example of a schematic configuration of a treatment facility and a treatment flow capable of executing the cyanogen-containing water treatment method of the second embodiment described above. As shown in FIG. 2, the treatment facility 20 includes a first reaction tank (a) 21, a removal tank (b2) 24, a second reaction tank (c) 22, and a solid-liquid separator (d) 26. . The above-mentioned step (A) is carried out in the first reaction tank (a) 21, the above-mentioned step (B2) is carried out in the removal tank (b2) 24, and the above-mentioned process ( C) can be subjected to the above step (D) in a solid-liquid separator (d) 26 . Descriptions of (a), (b2), (c), and (d) are omitted below.

The first reaction vessel 21 in the treatment facility 20 shown in FIG. 2 is the same as the first reaction vessel 11 in the treatment facility 10 described above. The solid-liquid separation device 26 for solid-liquid separation of the reaction liquid W ₂₂ obtained in the second reaction tank 22 in the processing equipment 20 is the same as the solid-liquid separation device 16 in the processing equipment 10 described above. Further, the second reaction vessel 22 in the treatment facility 20 shown in FIG. 2 is similar to the second reaction vessel 12 in the treatment facility 10 shown in FIG. 1 except that the liquids flowed therein are different. The treatment facility 20 may also include a relay tank between the second reaction tank 22 and the solid-liquid separator 26 or the like.

The removal tank 24 is a tank into which the reaction liquid W 21 obtained in the first reaction tank ₂₁ is flowed, and is a tank in which the reaction liquid W ₂₁ is brought into contact with the above-described hydrogen peroxide removing agent to react. be. In this removing tank 24, a reaction liquid _W24 in which the concentration of hydrogen peroxide remaining in the reaction liquid _W21 is reduced can be obtained. The removal tank 24 can be provided with a device 241 (a tank, a pump, a supply pipe, etc.) for adding a hydrogen peroxide removing agent to the reaction liquid W ₂₁ obtained in the first reaction tank 21 . Further, when the aforementioned decomposition catalyst is used as the hydrogen peroxide remover, a base material carrying the decomposition catalyst may be provided in the removal tank 24 . By passing the reaction liquid W21 obtained in the first reaction tank ₂₁ through the removal tank 24, the base material supporting the decomposition catalyst may be immersed in the reaction liquid _W21 . Furthermore, when the solid decomposition catalyst described above is used as the hydrogen peroxide remover, the removal tank 24 may be a tank filled with the solid decomposition catalyst. The reaction liquid W ₂₁ obtained in the first reaction tank 21 may be passed through the removal tank 24 to bring the reaction liquid W ₂₁ and the hydrogen peroxide remover into contact with each other.

The treatment equipment 20 includes a measuring device (b1) 23 for measuring the concentration of hydrogen peroxide remaining in the reaction liquid W 21 obtained in the first reaction tank ₂₁ , and a residual hydrogen peroxide concentration in the reaction liquid W 24 obtained in the removal tank ₂₄ . A hydrogen peroxide concentration measuring device (b3) 25 is preferably provided. The above-described step (B1) can be performed by the measuring device (b1) 23 and the above-described step (B3) can be performed by the measuring device (b3) 25 . These measuring devices 23 and 25 can also be similar to the hydrogen peroxide concentration measuring device 13 in the treatment facility 10 shown in FIG. is.

In order to facilitate the explanation of the above steps (B1) and (B3), an example in which the hydrogen peroxide concentration measuring devices 23 and 25 are provided was described, but instead of the measuring devices 23 and 25, steps (B1) and (B3) The same (common) measuring device 27 can also be used in each step (B3). In this case, the hydrogen peroxide concentration measuring device 27 is installed in the removal tank 24, and in the removal tank 24, the residual hydrogen peroxide concentration in the reaction liquid W ₂₁ is measured (step (B1)), and the reaction liquid W _{24 is} measured. Measurement of the residual hydrogen peroxide concentration (step (B3)) can be performed.

The hydrogen peroxide concentration measuring device 27 can also cooperate with the aforementioned controller. Specifically, the value of the hydrogen peroxide concentration measured by the measuring device 27 is a predetermined value or less (for example, 10 mg-H ₂ O ₂ /L or less, more preferably 5 mg-H ₂ O ₂ /L or less, further preferably is 3 mg-H ₂ O ₂ /L or less, particularly preferably 0 mg-H ₂ O ₂ /L). ) are preferably linked. For example, when the value of the hydrogen peroxide concentration measured by the measuring device 27 exceeds the predetermined value, the adding device 241 (injection pump) for the hydrogen peroxide remover is operated, and the hydrogen peroxide measured by the measuring device 27 is The measurement device 27 and the addition device 241 (injection pump) for the hydrogen peroxide removal agent are interlocked so that the addition device 241 (injection pump) for the hydrogen peroxide removal agent stops when the concentration value becomes equal to or less than the predetermined value. can be made

In addition, in FIG. 2, the first step (A) using hydrogen peroxide, the step (B2) using a hydrogen peroxide remover, and the step (C) using a copper (I) compound are illustrated for ease of explanation. Although the reaction vessel 21, the removal vessel 24, and the second reaction vessel 22 are each shown separately, the first reaction vessel 21 and the removal vessel 24; the removal vessel 24 and the second reaction vessel 22; The tank 21, the removal tank 24, and the second reaction tank 22 may be the same (common) tank. On the other hand, it is preferable to proceed to the next step after completing the reaction with hydrogen peroxide in step (A) (more preferably after hydrogen peroxide is consumed by the reaction), and in step (B2) Since it is preferable to proceed to the next step after finishing the reaction with the hydrogen peroxide removing agent, the first reaction tank 21, the removal tank 24, and the second reaction tank 22 are separate tanks. is preferred.

Also, in FIG. 2, the hydrogen peroxide concentration measuring device 23 is placed between the first reaction tank 21 and the removal tank 24 (a flow path ), the measuring device 23 may be installed in the first reaction tank 21 or may be installed in the common tank that also serves as the first reaction tank 21 . Furthermore, in FIG. 2, the hydrogen peroxide concentration measuring device 25 is placed between the removal tank 24 and the second reaction tank 22 (a flow path between the removal tank 24 and the second reaction tank 22) to facilitate the explanation of the step (B3) that can be performed as necessary. ), the measuring device 25 may be installed in the removal tank 24 or may be installed in the common tank that also serves as the removal tank 24 .

As described above, the waste water from exhaust gas cleaning is preferable as the water to be treated. Therefore, the method for treating cyanide-containing water according to the present embodiment can also be applied to equipment for treating waste water from cleaning exhaust gas. FIG. 3 is an explanatory diagram showing a schematic configuration of an example of an exhaust gas treatment facility and a treatment flow on the assumption that the cyanide-containing water treatment method of the present embodiment is applied.

The exhaust gas G treatment equipment 300 _shown in FIG. 302 and a primary treated water tank 303 for storing the supernatant liquid W ₃₀₂ obtained by the sedimentation separation as primary treated water. In addition, part of the supernatant liquid (primary treated water) sent to the primary treated water tank ₃₀₃ is returned to the wet dust collector 301 as circulating water W 303 while supplementary water W ₃₀₄ is added to wash the exhaust gas G. It may be used cyclically. Furthermore, a dehydrator 38 may be provided for dehydrating the sediment S ₃₀₂ obtained by sedimentation separation in the sedimentation tank 302, a part of which is processed by the dehydrator 38 is processed as a dehydrated cake C, and another part is processed. A portion may be resent to settling tank 302 as desorbed liquid (dehydrated filtrate) _W38 .

When the primary treated water in the primary treated water tank 303 contains cyanide ions and an iron cyano complex, the primary treated water is treated in the method for treating cyanide-containing water of the present embodiment. It can be water _W10 . In FIG. 3, the primary treated water in the primary treated water tank 303 is sent as blow water (water to be treated W ₁₀ ) to the above-described treatment facilities 10 and 20 (the first reaction tanks 11 and 21 in them), and the present embodiment The case of performing the method for treating cyanide-containing water is exemplified. The slurry containing the solid content separated from the liquid content by the solid-liquid separators 16 and 26 in the treatment facilities 10 and 20 is sent to the dehydrator 38 for dehydration treatment, and the separated water obtained by the dehydrator 38 (separated liquid , dehydrated filtrate) is preferably sent to the sedimentation tank 302 . The dehydrator 38 shown in FIG. 3 may be a thickening tank, or the thickening tank and the dehydrator 38 may be used together. In addition to the dehydrated filtrate, the sedimentation tank 302 may be supplied with the separated water obtained in the concentration tank, or may be supplied with the surplus slurry. In addition, instead of the sedimentation tank 302, various membrane separators, filters, and the like may be used.

The cyanide-containing water treatment technology described in detail above can have the following configuration.
[1] A step (A) of adding hydrogen peroxide to the water to be treated containing cyanide ions and an iron cyano complex to react, and the excess remaining in the reaction solution obtained in the step (A) A step (B1) of measuring the concentration of hydrogen oxide, a step (C) of adding a copper (I) compound to the reaction solution obtained in the step (A) and allowing it to react, and the step (C). and a step (D) of solid-liquid separation treatment of the obtained reaction liquid, wherein the amount of hydrogen peroxide added to the water to be treated in the step (A) is measured in the step (B1). A method for treating cyanide-containing water, wherein the amount of hydrogen peroxide concentration is controlled to 10 mg-H ₂ O ₂ /L or less.
[2] The amount of hydrogen peroxide added to the water to be treated in the step (A) is such that the hydrogen peroxide concentration value measured in the step (B1) is 5 mg-H ₂ O ₂ /L or less. The method for treating cyanide-containing water according to the above [1], wherein the amount is controlled to be
[3] Add the hydrogen peroxide to the water to be treated in the step (A) while monitoring the value of the hydrogen peroxide concentration measured in the step (B1) [1] or [ 2].
[4] A step (A) of adding hydrogen peroxide to the water to be treated containing cyanide ions and an iron cyano complex to react, the reaction solution obtained in the step (A), and the reaction solution A step (B2) of contacting and reacting with a hydrogen peroxide removing agent that reduces the concentration of the hydrogen peroxide remaining in the solution, and adding a copper (I) compound to the reaction solution obtained in the step (B2). and a step (D) of subjecting the reaction liquid obtained in the step (C) to a solid-liquid separation treatment.
[5] The method for treating cyanide-containing water according to [4] above, further comprising the step (B1) of measuring the concentration of the hydrogen peroxide remaining in the reaction solution obtained in the step (A).
[6] The cyanide-containing water according to [4] or [5] above, further comprising a step (B3) of measuring the concentration of the hydrogen peroxide remaining in the reaction solution obtained in the step (B2). Processing method.
[7] The cyanide-containing water according to any one of the above [4] to [6], wherein the hydrogen peroxide remover contains either one or both of a hydrogen peroxide reducing agent and a hydrogen peroxide decomposition catalyst. How to handle.
[8] In the step (A), the cyanide ions in the water to be treated are decomposed by the hydrogen peroxide, and in the step (C), the copper (I) compound obtained in the step (C) The cyanogen-containing water according to any one of the above [1] to [7], wherein a sparingly soluble substance of the iron cyano complex is produced in the reaction solution obtained, and the sparingly soluble substance is separated and removed in the step (D). How to handle.
[9] The water to be treated is exhaust gas that has been subjected to a solid-liquid separation treatment for removing the suspended matter from the dust collection water obtained by wet dust collection treatment of the exhaust gas containing suspended matter. A step (E) of performing either one or both of a concentration treatment and a dehydration treatment on a slurry that is washing wastewater and contains solids separated from the liquid in the step (D), and Cyanogen-containing water according to any one of the above [1] to [8], further comprising a step (F) of sending the obtained separated water to the solid-liquid separation treatment for obtaining the washing wastewater of the exhaust gas. How to handle.
[10] Either the water to be treated to which the hydrogen peroxide is added in the step (A) or the reaction liquid to which the copper (I) compound is added in the step (C) Alternatively, the method for treating cyanide-containing water according to any one of [1] to [9] above, wherein a reducing agent is further added to both.
[11] The cyanide according to any one of [1] to [10] above, wherein a quaternary ammonium compound is further added to the reaction solution to which the copper (I) compound is added in the step (C). Contained water treatment method.
[12] The method for treating cyanide-containing water according to any one of the above [1] to [11], wherein the step (A) and the step (C) are performed in separate reaction tanks.
[13] The iron cyano complex contains either one or both of ferrocyanide ions and ferricyanide ions, and [Fe(CN) ₅ (CO)] ^3- and [Fe(CN) ₄ (CO) ₂ ^] The method for treating cyanide-containing water according to any one of [1] to [12] above, including either or both of 2-.
[14] Hydrogen peroxide is added to the water to be treated containing cyanide ions and iron cyano complexes in a reaction tank (a), and residual hydrogen peroxide remains in the reaction solution obtained in the reaction tank (a). a measuring device (b1) for measuring the concentration of hydrogen peroxide; a reaction vessel (c) in which a copper (I) compound is added to the reaction solution obtained in the reaction vessel (a) and reacted; A solid-liquid separation device (d) for solid-liquid separation of the reaction liquid obtained in the reaction tank (c), and the measuring device for measuring the amount of hydrogen peroxide added to the water to be treated in the reaction tank (a) A cyanogen-containing water treatment facility, comprising: a controller for controlling the amount of hydrogen peroxide concentration measured in (b1) to be 10 mg-H ₂ O ₂ /L or less.
[15] Hydrogen peroxide is added to the water to be treated containing cyanide ions and iron cyano complexes in a reaction tank (a), and residual hydrogen peroxide remains in the reaction solution obtained in the reaction tank (a). A removal tank (b2) in which a hydrogen peroxide removing agent for reducing the concentration of hydrogen peroxide is added and reacted, and a copper (I) compound is added to the reaction solution obtained in the removal tank (b2). A treatment facility for cyanide-containing water, comprising: a reaction tank (c) for reacting; and a solid-liquid separation device (d) for solid-liquid separation of the reaction liquid obtained in the reaction tank (c).

Hereinafter, the effects of the method for treating cyanide-containing water according to one embodiment of the present invention will be described in more detail with reference to test examples, but the present invention is not limited to the following test examples.

<Test Example 1>
(Water to be treated)
Water to be treated containing 2.0 mg-CN/L of cyanide ion (soluble F-CN) and 11.6 mg-CN/L of soluble cyano complex (soluble complex CN) (soluble total cyanide ( T-CN) concentration of 13.6 mg-CN/L) was prepared. Specifically, it is obtained by sedimentation and separation of wastewater containing suspended solids such as unburned carbon, iron, and zinc discharged from exhaust gas treatment equipment that cleans exhaust gas in a predetermined factory. Supernatant water (concentration of suspended solids = 48 mg/L) was prepared as water to be treated. The water to be treated was analyzed using the apparatus (liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) apparatus) and conditions described in JP-A-2018-69227. contains 0.9 mg-CN/L ferrocyanide ion ([Fe(CN) ₆ ] ^4- ), 0.3 mg-CN/L ferricyanide ion ([Fe(CN) ₆ ] ^3- ) , 9.1 mg-CN/L of the iron carbonyl cyano complex (5.8 mg-CN/L of [Fe(CN) ₅ (CO)] ³⁻ and 3.3 mg-CN/L of [Fe(CN) ₄ ( CO) ₂ ] ^2- ), and 1.3 mg-CN/L of [Cu(CN) ₃ ] ^3- were found to be present. Furthermore, the water to be treated has a pH of 7.7, suspended solids (SS) of 36 mg/L, COD of 11 mg/L, TN (total nitrogen) of 130 mg/L, and TP (total phosphorus). was 0.1 mg/L, and inorganic carbon was 310 mg/L. These and the soluble F-CN and soluble T-CN were measured by the method described in JIS K0102:2013.

(Test Examples 1.1 to 1.3)
500 mL of the water to be treated adjusted to pH 6.8 and temperature of 50° C. was taken in a beaker, 35 mass % hydrogen peroxide solution was added, and the mixture was reacted for 15 minutes while stirring to obtain a reaction solution (step (A)). . The amount of hydrogen peroxide solution added is controlled so that the concentration of hydrogen peroxide remaining in the reaction solution is 10 mg-H ₂ O ₂ /L or less, and the added amount shown in Table 1 as H ₂ O ₂ (hereinafter , “H ₂ O ₂ addition amount”). In Test Example 1.3, 20 mg/L of sodium thiosulfate was added together with hydrogen peroxide. Also, the concentration of hydrogen peroxide remaining in the reaction solution (hereinafter referred to as "residual H ₂ O ₂ concentration") was measured (step (B1)). For this measurement, trade names "RQ Flex" and "Reflectquant Peroxide Test" (manufactured by Kanto Kagaku Co., Ltd.) were used.

Next, a cuprous oxide solution was added to the reaction solution in the amount shown in Table 1 as copper (Cu), and the mixture was reacted for 15 minutes with stirring (step (C)). As the cuprous oxide solution, a solution prepared by dissolving cuprous oxide in 35% by mass hydrochloric acid and adjusting the copper (Cu) concentration to 5% by mass was used. In Test Examples 1.2 and 1.3, 30 mg/L of didecyldimethylammonium chloride, which is a quaternary ammonium compound, was added to the reaction solution together with cuprous oxide.

1 mg/L of an anionic polymer flocculant (trade name “KEA-730”, manufactured by Nippon Steel Kankyo Co., Ltd.) was added to the reaction solution obtained after reacting by adding cuprous oxide, etc., under stirring. . The reaction solution to which the flocculant was added was allowed to stand, and the sparingly soluble (poorly soluble in water) cyanide compound generated in the reaction solution was precipitated for solid-liquid separation, and the resulting supernatant water was used as treated water ( Step (D)). For this treated water, the total cyanide concentration of the treated water (denoted as “treated water T-CN” in Table 1) was measured based on the total cyanide analysis method specified in JIS K0102:2013. A magnetic stirrer was used to stir the above reactions.

(Test Examples 1.4 to 1.6)
In Test Example 1.4, the procedure and method were the same as in Test Example 1.1, except that the amount of H ₂ O ₂ added was changed to the amount shown in Table 1 and cuprous oxide was not used. did In Test Example 1.5, hydrogen peroxide water was added without controlling the residual H ₂ O ₂ concentration to be 10 mg / L or less, and the amount of H ₂ O ₂ added and the amount of cuprous oxide added were shown. The treatment was performed in the same procedure and method as in Test Example 1.1, except that the procedure and method were changed as shown in 1.1. In Test Example 1.6, hydrogen peroxide solution was added without controlling the residual H ₂ O ₂ concentration to be 10 mg/L or less, and the amount of H ₂ O ₂ added was changed as shown in Table 1. Except for this, the same procedure and method as in Test Example 1.3 were used for treatment. The T-CN of the treated water obtained in Test Examples 1.4 to 1.6 was also measured according to the analysis method described above.

Table 1 shows the test conditions and treated water T-CN of Test Examples 1.1 to 1.6.

As shown in Table 1, in Test Examples 1.1 to 1.3, hydrogen peroxide and a copper(I) compound were added, and the amount of H ₂ O ₂ added was obtained after reaction with hydrogen peroxide. By controlling the residual H ₂ O ₂ concentration in the reaction liquid to be 10 mg-H ₂ O ₂ /L (further 5 mg-H ₂ O ₂ /L) or less, T-CN in the treated water is sufficiently reduced It was confirmed that the cyanide component could be removed from the water to be treated to a high degree.

On the other hand, since no copper (I) compound was used in Test Example 1.4, almost no ability to remove cyanide components from the water to be treated was observed. In Test Example 1.5, hydrogen peroxide and a copper (I) compound were used, and in Test Example 1.6, sodium thiosulfate was used together with hydrogen peroxide, and a fourth Although an ammonium salt was used, the residual H ₂ O ₂ concentration in the reaction solution when adding the copper (I) compound etc. was 30 mg-H ₂ O ₂ /L or more, so the treated water T-CN was sufficiently treated. , and the cyan component could not be removed from the water to be treated to a high degree.

<Test Example 2>
In Test Example 2, as shown in the "Water to be treated" column of Table 2, four types of water to be treated having different cyan component concentrations were prepared. These waters to be treated _were also analyzed in the same manner as the water ^to be treated used in Test Example 1 described above. It was confirmed that [Fe(CN) ₆ ] ³⁻ , [Fe(CN) ₅ (CO)] ³⁻ , and [Fe(CN) ₄ (CO) ₂ ] ²⁻ were included.

(Test Examples 2.1 to 2.6)
The amounts of H ₂ O ₂ , sodium thiosulfate, cuprous oxide, and didecyldimethylammonium chloride (quaternary ammonium compound) added to the water to be treated shown in Table 2 were set as shown in Table 2. Except for this, treatment was performed in the same procedure and method as in Test Examples 1.1 to 1.3 to obtain treated water.

(Test Examples 2.7 to 2.11)
In Test Examples 2.7 to 2.11, hydrogen peroxide water was added without controlling the residual H ₂ O ₂ concentration to be 10 mg / L or less, and H ₂ O ₂ , sodium thiosulfate, cuprous oxide , and didecyldimethylammonium chloride (quaternary ammonium compound) were added in the same amounts as shown in Table 2. , to obtain treated water.

For each treated water obtained in Test Examples 2.1 to 2.11, the total cyanide concentration of the treated water ("treated water T-CN" in Table 2) was measured in the same manner as described in Test Example 1. ) was measured. The results are also shown in Table 2.

As shown in Table 2, not only the water to be treated with low concentrations of soluble F-CN and soluble complex CN, but also the water to be treated with a higher concentration of soluble complex CN than the concentration of soluble F-CN Also, by controlling the amount of H ₂ O ₂ added so that the residual H ₂ O ₂ concentration is 10 mg/L or less, the T-CN in the treated water can be sufficiently reduced, and the cyan component is removed from the water to be treated. was confirmed to be highly removed.

<Test Example 3>
Waste water discharged from exhaust gas cleaning equipment, containing 2.0 mg-CN/L of cyanide ion (soluble F-CN) and 5.2 mg-CN/L of iron cyano complex (soluble complex CN) Containing waste water was sampled. When this wastewater was also analyzed in the same manner as the water to be treated used in Test Example 1, [Fe(CN) ₆ ] ⁴⁻ , [Fe(CN) ₆ ] ³⁻ , [Fe(CN) ₅ ( CO)] ^3- and [Fe(CN) ₄ (CO) ₂ ] ^2- were found to be contained. KCN was added to this wastewater to adjust the F-CN concentration shown in Table 3, and simulated wastewater was used.

In Test Example 3, the above-described simulated wastewater was used as the water to be treated, and _{hydrogen peroxide} was added to the water to be treated for reaction. From the measurement results of , a test was conducted to examine the optimum amount of H ₂ O ₂ to be added according to the water to be treated.

H ₂ O ₂ was added in an amount of 15 mg/L, 30 mg/L, or 70 mg/L, and 20 mg/L of sodium thiosulfate was added to the water to be treated having the soluble F—CN concentration shown in Table 3. After reacting for 15 minutes while stirring with a magnetic stirrer to obtain a reaction liquid, the concentration of residual H ₂ O ₂ in the reaction liquid was measured. The results are shown in Table 3-1.

20 mg-Cu/L of cuprous oxide and 30 mg/L of didecyldimethylammonium chloride were added to the reaction solution obtained after the reaction by adding hydrogen peroxide and sodium thiosulfate to the water to be treated, and the mixture was stirred with a magnetic stirrer. While stirring at , the reaction was allowed to proceed for 15 minutes to obtain a reaction solution. For this reaction liquid, treated water was obtained by the same method as described in Test Examples 1.1 to 1.3, and T-CN of the treated water was measured. The results are shown in Table 3-2.

From the results of Test Example 3, in the case of water to be treated containing about 5 mg-CN/L of soluble complex CN, a suitable amount of hydrogen peroxide to be added is determined according to the concentration of soluble F-CN in the water to be treated. It is possible to guess. An example is shown in Table 3-3.

<Test Example 4>
(Test Examples 4.1 and 4.2)
To the same water to be treated as used in Test Example 1, at pH 6.8 and a water temperature of 50°C, 35 mass% hydrogen peroxide water in an amount corresponding to the amount of H ₂ O ₂ added shown in Table 4, and 20 mg of sodium thiosulfate /L was added and reacted for 5 minutes while stirring with a magnetic stirrer to obtain a reaction solution (step (A)). Further, the residual H ₂ O ₂ concentration in the reaction solution was measured in the same manner as in Test Example 1 (step (B1)).

Then, sodium sulfite was added as a hydrogen peroxide (H ₂ O ₂ ) removing agent to the reaction solution obtained after the addition and reaction of H ₂ O ₂ and sodium thiosulfate (Na ₂ (addition amount as SO ₃ ), and reacted for 5 minutes while stirring with a magnetic stirrer (step (B2)). Then, the residual H ₂ O ₂ concentration in the resulting reaction solution was measured in the same manner as above (step (B3)). A 30% by mass sodium sulfite aqueous solution was used for the addition of sodium sulfite.

20 mg-Cu/L of cuprous oxide was added to the reaction solution obtained after the addition and reaction of Na ₂ SO ₃ and reacted for 15 minutes (step (C)). Thereafter, in the same manner as in Test Example 1, after obtaining treated water (step (D)), T-CN of treated water was measured.

(Test Example 4.3)
In Test Example 4.3, cuprous oxide was added to the reaction solution obtained after the addition and reaction of H ₂ O ₂ without using an H ₂ O ₂ removing agent such as sodium sulfite in step (B2). Except for this, the treatment was performed in the same procedure and method as in Test Example 4.2, and the treated water T-CN was measured.

(Test Examples 4.4 to 4.17)
In Test Examples 4.4 to 4.17, sodium thiosulfate was not used in step (A), the amount of H ₂ O ₂ added in step (A), and the H ₂ O ₂ remover in step (B2) The type and amount of addition, and the amount of cuprous oxide added in step (C) were treated in the same procedure and method as in Test Example 4.1, except that the conditions shown in Table 4 were used to treat the treated water. T-CN was measured. As the H ₂ O ₂ remover, in Test Examples 4.4 to 4.10, a solution prepared by adjusting "catalase (derived from bovine liver)" (manufactured by Tokyo Chemical Industry Co., Ltd.) to 0.1% by mass with pure water was used. bottom. Powdered manganese dioxide (MnO ₂ ) was used as it was in Test Examples 4.11 to 4.13. In Test Examples 4.14 to 4.17, powdered activated carbon was mixed with pure water to adjust the concentration to 1% by mass, and a stirred slurry was used.

Table 4 shows the test conditions of Test Examples 4.1 to 4.17 and the results of the treated water T-CN.

From the results of Test Example 4, although hydrogen peroxide remained in the reaction solution obtained after the addition and reaction of hydrogen peroxide to the water to be treated, hydrogen peroxide removers (sodium sulfite, catalase, dioxide Manganese and activated carbon) was confirmed to reduce the concentration of residual H ₂ O ₂ in the reaction solution. In addition, as a result, the total cyanide concentration in the treated water from the reaction solution obtained after the addition and reaction of the copper (I) compound could be sufficiently reduced, and the cyanide component could be highly removed from the treated water. was confirmed.

REFERENCE SIGNS LIST 10 cyanogen-containing water treatment facility 11 first reaction tank 12 second reaction tank 13 hydrogen peroxide concentration measuring device 16 solid-liquid separator 17 control unit 20 cyanide-containing water treatment facility 21 first reaction tank 22 second 2 reaction tank 23, 25, 27 hydrogen peroxide concentration measuring device 24 removal tank 26 solid-liquid separation device

Claims (14)

A step (A) of adding hydrogen peroxide to the water to be treated containing cyanide ions and an iron cyano complex to cause a reaction;
A step (B2) of bringing the reaction solution obtained in the step (A) into contact with a hydrogen peroxide removing agent that reduces the concentration of the hydrogen peroxide remaining in the reaction solution and reacting them;
A step (C) of adding a copper (I) compound to the reaction solution obtained in the step (B2) and reacting it;
A method for treating cyanogen-containing water, comprising a step (D) of subjecting the reaction liquid obtained in the step (C) to a solid-liquid separation treatment. 2. The method for treating cyanide-containing water according to claim 1, further comprising a step (B1) of measuring the concentration of said hydrogen peroxide remaining in said reaction solution obtained in said step (A). 3. The method for treating cyanide-containing water according to claim 1, further comprising a step (B3) of measuring the concentration of said hydrogen peroxide remaining in said reaction solution obtained in said step (B2). While monitoring the value of the hydrogen peroxide concentration measured in the step (B3), in the step (B2), the reaction solution obtained in the step (A) is brought into contact with the hydrogen peroxide removing agent. The method for treating cyanide-containing water according to claim 3, wherein Monitoring the value of the hydrogen peroxide concentration measured in the step (B3) is performed by monitoring the concentration of the hydrogen peroxide remaining in the reaction solution obtained in the step (A) in the step (B3). 5. The method for treating cyanide-containing water according to claim 4, wherein the measurement is carried out in a continuous manner, or intermittently in a batch manner. The method for treating cyanide-containing water according to any one of claims 1 to 5, wherein the water to be treated has a higher iron cyano complex concentration than the cyanide ion concentration. The method for treating cyanide-containing water according to any one of claims 1 to 6, wherein the hydrogen peroxide remover contains one or both of a hydrogen peroxide reducing agent and a hydrogen peroxide decomposition catalyst. In the step (A), the cyanide ions in the water to be treated are decomposed by the hydrogen peroxide,
In the step (C), the copper (I) compound produces a poorly soluble iron cyano complex in the reaction solution obtained in the step (C),
The method for treating cyanide-containing water according to any one of claims 1 to 7, wherein in the step (D), the poorly soluble substances are separated and removed. The water to be treated is exhaust gas scrubbing wastewater that has been subjected to a solid-liquid separation treatment to remove the suspended solids from dust collected by wet dust collection of the exhaust gas containing suspended solids. can be,
A step (E) of performing either one or both of a concentration treatment and a dehydration treatment for the slurry containing the solid content separated from the liquid content in the step (D);
9. The method according to any one of claims 1 to 8, further comprising a step (F) of sending the separated water obtained in step (E) to the solid-liquid separation process for obtaining the scrubbing wastewater of the exhaust gas. A method for treating cyanide-containing water as described. To either or both of the water to be treated to which the hydrogen peroxide is added in the step (A) and the reaction solution to which the copper (I) compound is added in the step (C) The method for treating cyanide-containing water according to any one of claims 1 to 9, further comprising adding a reducing agent. The treatment of cyanide-containing water according to any one of claims 1 to 10, wherein a quaternary ammonium compound is further added to the reaction solution to which the copper (I) compound is added in the step (C). Method. The method for treating cyanide-containing water according to any one of claims 1 to 11, wherein the step (A) and the step (C) are performed in separate reaction tanks. The iron cyano complex contains either one or both of ferrocyanide ions and ferricyanide ions, and [Fe(CN) ₅ (CO)] ³⁻ and [Fe(CN) ₄ (CO) ₂ ] ² The method for treating cyanide-containing water according to any one of claims 1 ^to 12, including either one or both of -. a reaction vessel (a) in which hydrogen peroxide is added to water to be treated containing cyanide ions and an iron cyano complex to cause a reaction;
a removing tank (b2) in which a hydrogen peroxide removing agent for reducing the concentration of the hydrogen peroxide remaining in the reaction solution obtained in the reaction tank (a) is added and reacted;
a reaction tank (c) in which a copper (I) compound is added to the reaction solution obtained in the removal tank (b2) and reacted;
a solid-liquid separator (d) for solid-liquid separation of the reaction liquid obtained in the reaction tank (c);
A treatment facility for cyanide-containing water.

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