Treatment method for cyanide-containing wastewater

Abstract

To provide a technique capable of decreasing the amount of an oxidizer to be used in treating cyan-containing wastewater.SOLUTION: In the method of treating cyan-containing wastewater, an oxidizer, a reaction accelerator, and a copper salt are mixed into cyan-containing wastewater. The amount of the oxidizer to be added to the wastewater is not less than the theoretical equivalent needed to decompose the whole cyan into nitrogen and carbonic acid, and the oxidizer may be added thereto in an amount so as to be not more than three times of the theoretical equivalent (mg / L). The copper salt may be added to the wastewater in an amount of not more than the theoretical equivalent of the oxidizer. The copper salt may be added to the wastewater in an amount of not more than the theoretical equivalent that reacts with the whole cyan.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating cyanide-containing wastewater, a method for improving cyanide treatment in wastewater, and chemicals for treating cyanide-containing wastewater. [Background technology]

[0002] The alkaline chlorination method is a known treatment method for cyanide-containing wastewater discharged from industrial facilities such as plating plants, steel mills, smelters, power plants, and coke manufacturing plants. This alkaline chlorination method involves adding a chlorine source (e.g., sodium hypochlorite (NaOCl)) to cyanide-containing wastewater under alkaline conditions to oxidize the cyanide in the wastewater. The required amount of chlorine source such as NaOCl can be easily controlled based on the ORP (oxidation-reduction potential) value. For this reason, the alkaline chlorination method is widely used as the most practical treatment method for cyanide-containing wastewater.

[0003] For example, Patent Document 1 discloses an alkaline chlorination method for oxidative decomposition of cyanide compounds in a two-step reaction at the following pH and ORP control values.

[0004] One-stage reaction: pH 10 or higher, ORP control value 300-350mV NaCN + NaOCl → NaCNO + NaCl ... (1) Two-stage reaction: pH 7-8, ORP control value 600-650mV 2NaCNO+3NaClO+H2O→N2+3NaCl+2NaHCO3…(2)

[0005] Furthermore, for example, Patent Document 2 describes a method for treating cyanide-containing wastewater containing ammonia by a two-step reaction using the alkaline chlorination method.

[0006] Furthermore, for example, Patent Document 3 describes a method for treating cyanide and ammonia-containing wastewater, which includes a step of adding a chemical solution containing hypobromous acid and / or hypobromous salt to cyanide and ammonia-containing wastewater to oxidize and decompose the cyanide at a pH of 9 to 11. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2001-269674 [Patent Document 2] Japanese Patent Publication No. 2006-334508 [Patent Document 3] Japanese Patent Publication No. 2015-202482 [Overview of the project] [Problems that the invention aims to solve]

[0008] Furthermore, the main objective of the present invention is to provide a technology that can reduce the amount of oxidizing agent used in the treatment of cyanide-containing wastewater. [Means for solving the problem]

[0009] As a result of diligent research into the above-mentioned problems, the inventors have found that, as shown in the examples below, by using an oxidizing agent, a reaction accelerator, and a copper salt in combination, it is possible to effectively treat all cyanide in wastewater with approximately the theoretical equivalent amount required to decompose it into cyanic acid (CNO), nitrogen, or carbonic acid, and to eliminate the need to add an oxidizing agent necessary for the decomposition of ammonia. In this way, the inventors have found that the amount of oxidizing agent used can be significantly reduced, and have completed the present invention. Furthermore, compared to conventional treatment technologies, the present invention can treat cyanide-containing wastewater in a shorter time and in a smaller space. In other words, the present invention is as follows.

[0010] The present invention provides a method for treating cyanide-containing wastewater, which involves mixing an oxidizing agent, a reaction accelerator, and a copper salt with the cyanide-containing wastewater. The present invention can provide a cyanide treatment agent which is an agent for treating cyanide in cyanide-containing wastewater and contains an oxidizing agent, a reaction accelerator, and a copper salt. The present invention can provide a chemical kit for treating cyanide-containing wastewater, which is composed of (a) an oxidizing agent, (b) a reaction accelerator, and (c) a copper salt. The present invention can provide a reduction method, which is a method for reducing the usage amounts of an oxidizing agent and a reaction accelerator when treating cyanide in wastewater, and is characterized by using a copper salt as an active ingredient in combination with the oxidizing agent and the reaction accelerator. The oxidizing agent may be a hypochlorite. The reaction accelerator may be bromine and / or a bromine compound. The mixing may reduce all cyanide in the wastewater. The cyanide may contain free cyanide and / or a cyanide compound. The addition amount of the oxidizing agent to the wastewater is not less than the theoretical equivalent required to decompose all cyanide to nitrogen and carbon dioxide, and may be added in an amount (mg / L) not exceeding 3 times the theoretical equivalent. The addition amount of the copper salt to the wastewater may be added not exceeding the theoretical equivalent of the oxidizing agent. The addition amount of the copper salt to the wastewater may be added not exceeding the theoretical equivalent of copper that reacts with all cyanide.

Advantages of the Invention

[0011] According to the present invention, a technique for reducing the usage amount of an oxidizing agent in the treatment of cyanide-containing wastewater can be provided. Note that the effects described here are not necessarily limited thereto, and any of the effects described in this specification may be applicable.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing an apparatus or system for treating cyanide-containing wastewater of the present invention.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention will be described. The embodiments described below show an example of typical embodiments of the present invention, and the scope of the present invention is not limited or interpreted thereby. The upper limit value (or more) and the lower limit value (or less) of each numerical range (~) can be arbitrarily combined as desired.

[0014] <1. Treatment method for cyanide-containing wastewater of the present invention> The present invention can provide a treatment method for cyanide-containing wastewater in which an oxidizing agent, a reaction accelerator, and a copper salt are mixed into cyanide-containing wastewater (hereinafter also referred to as treated water).

[0015] In the treatment method of the present invention, the "cyanide-containing wastewater" to be treated is exemplified by wastewater containing cyanide discharged from industrial facilities such as plating factories, power plants, steel mills, smelters, and coke manufacturing factories, but the present invention is not limited to these wastewaters. The total cyanide concentration of the cyanide-containing wastewater is usually about 0.1 to 100 mg / L, preferably 0.1 to 50 mg / L, more preferably 0.1 to 20 mg / L, and even more preferably 0.1 to 10 mg / L. Also, the pH (20 °C) of the cyanide-containing wastewater is usually about 6 to 10, preferably about 7.5 to 10.

[0016] In the present invention, cyanide-containing wastewater containing ammonium ions and / or organic substances can also be a treatment target. The concentration of ammonium ions in the cyanide-containing wastewater is not particularly limited, and the preferred upper limit value is preferably 250 mg or less. The preferred lower limit value is not particularly limited, but examples include 3 mg / L or more and 5 mg / L or more, and the preferred numerical range can be, for example, about 0 to 250 mg / L. Examples of organic matter include, but are not limited to, organic matter derived from coal and coke generated from steel industry facilities such as steel mills, smelters, and coke manufacturing plants. The preferred upper limit of the concentration of organic matter in cyanide-containing wastewater is preferably 30 mg / L or less, and the preferred lower limit is not particularly limited, but for example, 1 mg / L or more, and the preferred numerical range may be, for example, around 0 to 30 mg / L.

[0017] In this invention, the water to be treated is preferably wastewater containing total cyanide. In this invention, "total cyanide" includes both free cyanide and cyanide compounds. In this invention, the cyanide compound includes a cyano complex. Examples of this cyano complex include metallic cyano complexes (e.g., one or more metals selected from Ni, Ag, Cu, Zn, Cd, etc.). In this invention, examples of this cyano complex include a persistent cyano complex (e.g., an iron cyano complex ([Fe(CN)6]) 4- , ([Fe(CN)6] 3- ) can include

[0018] The treatment method of the present invention has the advantage of being able to treat cyanide in cyanide-containing wastewater containing one or more selected from the group consisting of free cyanide, persistent Ni,Ag cyano complexes (e.g., Na2Ni(CN)4,NaAg(CN)), iron cyano complexes, and potassium salts thereof.

[0019] 1-1. Outline of the Invention Conventional methods for treating cyanide-containing wastewater require adding more than the theoretical equivalent amount of oxidizing agent (specifically sodium hypochlorite) necessary for the decomposition of both total cyanide and ammonia in order to control the ORP value to 400mV or higher. Therefore, when the total cyanide and ammonia concentrations are high, the amount of oxidizing agent used becomes extremely large. In particular, even when the amount of cyanide wastewater in steel mills is small, it can reach tens of m³. 3 / h~several hundred meters 3 The rate was / h, and to compensate for this, the amount of oxidizing agent used was enormous.

[0020] Furthermore, conventional methods for treating cyanide-containing wastewater (especially the alkaline chlorination method) involved sequentially adding alkali to maintain the treated water in an alkaline state.

[0021] Furthermore, conventional methods for treating cyanide-containing wastewater require long reaction times (e.g., more than one hour) to adjust the pH of the treated water and decompose persistent iron cyano complexes, necessitating tanks and wastewater treatment facilities to ensure this reaction time. Additionally, conventional alkaline chlorination methods have poor treatment capabilities for persistent cyanide compounds complexed with metal ions, making it difficult to adequately decompose and remove cyanide from the treated water.

[0022] Furthermore, the Prussian Blue process, which involves adding iron(II) salts to react with iron cyano complexes such as ferrocyanine ions and ferricyanine ions, has been conventionally known as a method for treating water containing iron cyano complexes. In this method, insoluble iron cyano complexes are precipitated at weakly acidic (pH 4-6), and then excess iron(II) salts and coexisting heavy metals are precipitated as hydroxides at highly alkaline (pH 9-12). However, in the Prussian Blue process, since the region in which insoluble iron cyano complexes are formed is weakly acidic, a two-stage treatment is required: a first step to precipitate the iron cyano complexes at pH 4-6, and a second step to precipitate excess iron(II) salts and coexisting heavy metals at pH 9-12. This necessitates adjusting the pH using large amounts of pH adjusters to bring the water to be treated into the acidic or alkaline range. In addition, in the Prussian Blue process, insoluble iron cyano complexes can redissolve with pH changes, making the treatment of cyanide-containing water prone to instability.

[0023] As shown in the examples below, in the present invention, the amount of oxidizing agent used is sufficient in amounts equivalent to the theoretical amount required to decompose the total cyanide to be treated into CNO (cyanic acid), nitrogen, or carbonic acid, eliminating the need to add an oxidizing agent necessary for ammonia decomposition. Therefore, with the treatment method of the present invention, the amount of oxidizing agent used in the treatment of cyanide-containing wastewater can be reduced. In the treatment method of the present invention, for example, if the total cyanide concentration is reduced from 10 mg / L to 5 mg / L, it is possible with the theoretical equivalent amount required to decompose 5 mg / L of total cyanide (10 mg / L to 5 mg / L). Furthermore, since the residual chlorine concentration in the treated water can be kept low with the treatment method of the present invention, the risk of corrosion to equipment such as steel can be reduced.

[0024] Furthermore, as shown in the [Examples] below, cyanide treatment can be performed in a single step of adding and mixing three chemicals to cyanide-containing wastewater in one container. Therefore, the treatment method of the present invention can also utilize existing treatment facilities. Furthermore, as shown in the [Examples] below, cyanide treatment can be performed in a single step of adding and mixing the three chemicals, even with a short reaction time of about 10 minutes. Therefore, the treatment method of the present invention can be carried out in a space-saving reaction area (for example, a small reaction tank, reaction piping, reaction channel, etc.). For this reason, it is easy to make treatment facilities for cyanide-containing wastewater more compact, or to install the reaction area of ​​the present invention in existing treatment facilities.

[0025] Furthermore, as shown in the examples below, copper salt alone cannot treat all cyanide in the water to be treated, but by using copper salt in combination with an oxidizing agent and a reaction accelerator, the immobilization of all cyanide in the water to be treated is promoted. Also, as shown in the examples below, all cyanide can be treated without pH adjustment.

[0026] Therefore, the treatment method of the present invention has the advantage that all cyanide can be treated without performing pH adjustment. The treatment method of the present invention can reduce the amount of pH adjusting agent used in the aqueous system, and can also reduce the treatment time and labor required for pH adjustment, thus being superior from the viewpoint of improving treatment efficiency and reducing costs.

[0027] The mechanism of action of the present invention's treatment method on total cyanide is currently under investigation. The chemical reactions currently suspected are as follows, and it is presumed that these reactions are accelerated by the use of an oxidizing agent. Regardless of the suspected chemical reactions, the present invention can insolubilize persistent cyanide. 2Cu 2+ +[Fe(CN)6] 4- →Cu2[Fe(CN)6] 3Cu 2+ +2[Fe(CN)6] 3- →Cu3[Fe(CN)6]2

[0028] Therefore, the treatment method of the present invention has the advantage of being able to oxidize and decompose cyanide compounds such as free cyanide and Zn cyano complexes, and to insolubilize and treat persistent cyanide such as iron cyano complexes.

[0029] The treatment method of the present invention can be applied to water systems that treat cyanide-containing wastewater, and can also be easily applied to conventional water systems. The treatment method of the present invention is preferably applied to water systems that perform processes such as the inflow of cyanide-containing raw water, cyanide treatment, coagulation treatment, sedimentation treatment, filtration treatment, and discharge, and it is even more preferable to circulate the treated water that does not meet the discharge standards for total cyanide concentration back to the cyanide treatment or upstream thereto.

[0030] In the treatment method of the present invention, the cyanide treatment reaction is preferably carried out after the cyanide-containing wastewater (raw water) flows into the water system and before the coagulation treatment. In the treatment method of the present invention, the three chemicals used in the present invention can be added simultaneously or at different times. It is preferable to add these three chemicals in close proximity to each other, as this facilitates mixing of the three chemicals. In the treatment method of the present invention, it is preferable to mix and bring into contact the three chemicals with the cyanide-containing wastewater in a location where sufficient retention time for cyanide treatment can be ensured. This location is preferably after the inflow of raw water and before coagulation (more preferably near the piping or outlet of the blowdown water for raw water or circulating water), and more specifically, it is the reaction site for cyanide treatment. This reaction site for cyanide treatment is preferably a water tank or reaction channel with a retention time of about 10 minutes. Furthermore, it is preferable to have a stirrer in the reaction site, as stirring brings the three chemicals into closer contact with the water to be treated, thereby facilitating the oxidative decomposition of cyanide and the insolubilization of refractory cyanide. Furthermore, it is preferable to leave the three agents of the present invention in the treated water for at least 5 minutes, more preferably 8 minutes, and even more preferably 10 minutes, after mixing them with the water to be treated. As a preferred upper limit, it is preferable to leave them in the water for at least 20 minutes, and more preferably 15 minutes.

[0031] The timing for mixing the three chemicals of the present invention with the water to be treated is not particularly limited, but it is preferable to do so at least 5 minutes before reaching the coagulation site (e.g., coagulation tank), preferably at least 8 minutes before, more preferably at least 10 minutes before, even more preferably at least 20 minutes before, and even more preferably at least 30 minutes before. The longer the time, the easier it is to perform stable cyanide treatment. The preferred upper limit is not particularly limited, but for example, it could be within 2 hours, 3 hours, or 4 hours. Also, from the viewpoint of space saving described later, "before" may be changed to "within," for example, "before 1.5 hours" may be changed to "within 1.5 hours" as the preferred upper limit. Furthermore, from the viewpoint of space saving by reducing the residence time, a shorter time is preferable for mixing the three chemicals with the water to be treated. Preferably, it is before 2 hours before reaching the coagulation site, more preferably before 1.5 hours before, even more preferably before 1 hour before, even more preferably before 30 minutes before, and even more preferably before 20 minutes before. Thus, while a longer time makes cyanide treatment easier, a shorter time saves space, so it is desirable to consider both aspects and arbitrarily combine these to apply the optimal time.

[0032] Furthermore, the treatment method of the present invention is suitable when the cyanide is water-soluble cyanide (for example, free cyanide or water-soluble cyano complex) because it can oxidize and decompose this water-soluble cyanide. Also, the treatment method of the present invention is suitable when the cyanide is recalcitrant cyanide (for example, iron cyano complex) because it can insolubilize this recalcitrant cyanide.

[0033] In the treatment method of the present invention, it is preferable to measure the ORP value of cyanide-containing wastewater (water to be treated) and carry out the reaction while controlling the amount of oxidizing agent, which is a chlorine source, added based on this ORP value, thereby preventing the ORP value from becoming too high. In the treatment method of the present invention, it is preferable to add an amount of oxidizing agent to cyanide-containing wastewater that is equal to or greater than the "theoretical equivalent amount required to decompose all cyanide into nitrogen and carbonic acid."

[0034] In the treatment method of the present invention, the reaction with cyanide mainly involves the formation of a product (e.g., hypobromous acid) from the oxidizing agent and reaction accelerator. Furthermore, in the treatment method of the present invention, the theoretical equivalent of the reaction between the oxidizing agent and cyanide can be calculated based on the chlorine source of the added oxidizing agent (e.g., hypochlorous acid). The amount of this chlorine source can be easily monitored and controlled using the ORP (oxidation-reduction potential) value. This calculation method can be performed based on the reaction equation between hypochlorous acid and cyanide, as shown below. Note that hypobromous acid has the effect of increasing the decomposition rate of cyanide (reaction rate for treatment with cyanide) compared to hypochlorous acid.

[0035] <Theoretical equivalents in this invention> The theoretical equivalent required to oxidize all cyanide to cyanic acid (CNO) can be calculated based on the following formula (1). ·NaCN + NaOCl→NaCNO+NaCl···Formula (1)

[0036] The theoretical equivalent required to decompose cyanate (CNO) into nitrogen and carbonic acid can be calculated based on the following equation (2). ·2NaCNO+3NaOCl+H2O→N2+3NaCl+2NaHCO3···Formula (2)

[0037] The theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid can be calculated based on the sum of equations (1) and (2) above. ·2NaCN+5NaOCl+H2O→N2+3NaCl+2NaHCO3···Formula (3) The theoretical equivalent of NaBr is defined as the amount at which the reaction yields a NaBr / NaOCl (molar ratio) of 0.1:1. This theoretical equivalent of NaBr was determined based on Example 5 of Patent Document 3 (Japanese Patent Publication No. 2015-202482).

[0038] The "theoretical equivalent of copper (hereinafter also referred to as 'theoretical equivalent of copper')" can be calculated based on the following formula (4). When calculating the "theoretical equivalent of copper", unless otherwise specified, it is assumed that all cyanides are ferricyanides. Ferricyanide ([Fe(CN)6] 4- ) is assumed to be all converted to ferricyanide ([Fe(CN)6] 3- ) by an oxidizing agent, and the reaction formula for the theoretical equivalent of copper is as follows. ·3Cu 2+ +[Fe(CN)6] 3- →Cu3[Fe(CN)6]2 ··· Formula (4)

[0039] 1-2. Each chemical used in the present invention In the treatment method of the present invention, it is preferable to use an oxidizing agent, a reaction accelerator, and a copper salt. Also, in the treatment method of the present invention, it is preferable to add these chemicals to the water to be treated simultaneously or at different times, and they may be mixed in the water to be treated by adding them. Further, it is not necessary to adjust the pH of the water to be treated, and it is not necessary to use a pH adjuster. Also, in the treatment method of the present invention, a one-component composition containing an oxidizing agent, a reaction accelerator, and a copper salt may be used. Also, in the treatment method of the present invention, a chemical kit composed of (a) an oxidizing agent, (b) a reaction accelerator, and (c) a copper salt may be used, for example, a chemical kit of two-component type or three-component type may be used. The chemicals used in the present invention will be described below.

[0040] 1-2-1. Oxidizing agent The oxidizing agent used in the present invention is not particularly limited, but a halogen-based oxidizing agent is preferable. As the halogen-based oxidizing agent (for example, chlorine-based, bromine-based, etc.), it is not particularly limited, but a chlorine-based oxidizing agent is preferable. The form of the oxidizing agent is not particularly limited and may be either powdery or liquid, but an aqueous solution form is preferable.

[0041] The chlorine-based oxidizing agent used in the present invention is not particularly limited, but examples include chlorine gas, chlorine dioxide, hypochlorous acid or its salt, chlorous acid or its salt, chloric acid or its salt, perchloric acid or its salt, chlorinated isocyanuric acid or its salt, and one or more selected from the group consisting of these can be used.

[0042] Specific examples of salt-type chlorine-based oxidizing agents include, but are not limited to, alkali metal hypochlorite salts such as sodium hypochlorite and potassium hypochlorite; alkaline earth metal hypochlorite salts such as calcium hypochlorite and barium hypochlorite; alkali metal hypochlorite salts such as sodium chlorite and potassium chlorite; alkaline earth metal hypochlorite salts such as barium chlorite; other metal hypochlorite salts such as nickel chlorite; alkali metal chlorite salts such as ammonium chlorate, sodium chlorate, and potassium chlorate; and alkaline earth metal chlorite salts such as calcium chlorate and barium chlorate. One or more selected from this group can be used.

[0043] Of the chlorine-based oxidizing agents mentioned above, one or more selected from the group consisting of hypochlorite, chlorine dioxide, and chlorine gas are preferred, and of these, hypochlorite is more preferred from the viewpoint of ease of handling, and sodium hypochlorite is even more preferred.

[0044] 1-2-2. Reaction Accelerators The reaction accelerator used in the present invention is not particularly limited, but halogen compounds are preferred, and preferably compounds that can accelerate the cyanide treatment reaction. The form of the reaction accelerator is not particularly limited and may be in powder or liquid form, but an aqueous solution is preferred.

[0045] 1-2-2-1. Brominated compounds (bromine and / or brominated compounds) Among halogenated compounds, bromine compounds are preferred, and of the bromine compounds, bromine and / or bromine compounds are more preferred, and of these, bromine compounds are even more preferred from the viewpoint of handling. The bromine compounds used in the present invention are not particularly limited, and examples include alkali metal bromides, ammonium bromides, hydrobromic acids, and amine bromides. One or more compounds selected from this group can be used.

[0046] Examples of the alkali metal bromide salt include, but are not limited to, sodium bromide, potassium bromide, and lithium bromide. Examples of the aforementioned bromide amine salts (such as linear, branched, or cyclic alkyl or alkenyl groups having 1 to 6 carbon atoms) include, but are not limited to, diethylamine hydrogen bromide, allylamine hydrogen bromide, cyclohexylamine hydrogen bromide, monomethylamine hydrogen bromide, dimethylamine hydrogen bromide, trimethylamine hydrogen bromide, n-butylamine hydrogen bromide, or ethylamine hydrogen bromide. The bromine or bromine compound can be one or more selected from the group consisting of these. The form of bromine or the bromine compound is not particularly limited and may be in powder or liquid form, but an aqueous solution form is preferred.

[0047] 1-2-3. Copper Salts The copper salt used in this invention is not particularly limited. Either copper(I) salt (cuprite) or copper(II) salt (cuprite) may be used as the copper salt, and one or more selected from the group consisting of these can be used. Examples of copper(I) salts include copper(I) chloride, copper(I) oxide (cuprous oxide), and copper(I) sulfate. Examples of copper(II) salts include copper(II) chloride and copper(II) sulfate. Of the copper salts mentioned above, copper(II) salts are preferred, and among these copper(II) salts, copper sulfate (Cu(II)SO4) is preferred. The form of the copper salt is not particularly limited and may be in powder or liquid form, but an aqueous solution form is preferred.

[0048] 1-2-4. How to use each drug 1-2-4-1. Amount of oxidizing agent used (amount added) In the treatment method of the present invention, it is preferable to add an amount of oxidizing agent to cyanide-containing wastewater in an amount equal to or greater than the theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid. The "theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid" for the oxidizing agent can be calculated by measuring the cyanide content in the water to be treated. That is, based on the above formula (3), it is 2.5 times the cyanide content (moles) in the water to be treated. The upper limit for the amount of oxidizing agent used is preferably 3 times or less the theoretical equivalent required to decompose total cyanide into nitrogen and carbonic acid, more preferably 2.2 times or less, even more preferably 1.8 times or less, more preferably 1.5 times or less, more preferably 1.2 times or less, and more preferably 1.1 times or less. The processing method of the present invention eliminates the need to add an oxidizing agent necessary for ammonia decomposition, allowing for more accurate calculation of the amount of oxidizing agent used (amount added), and enabling control of the total cyanide concentration with a smaller amount of oxidizing agent used (amount added). When the total cyanide concentration of treated water is to be 0.1 to 2 mg / L, it is preferable to use an amount of oxidizing agent that is at least 1 and no more than 1.5 times the theoretical equivalent required to decompose the total cyanide into nitrogen and carbonic acid. Furthermore, when reducing the total cyanide concentration of the treated water to less than 0.1 mg / L, it is preferable to use an amount of oxidizing agent that is 1.5 times or more and 2.5 times or less the theoretical equivalent required to decompose the total cyanide into nitrogen and carbonic acid, and more preferably 1.8 times or more and 2.3 times or less.

[0049] The amount of oxidizing agent used (amount added) per 1 mg / L of total cyanide concentration in the water to be treated is not particularly limited, but in terms of active ingredients, the preferred lower limit is preferably 6 mg / L or more, more preferably 7 mg / L or more, the preferred upper limit is preferably 20 mg / L or less, more preferably 16 mg / L or less, and further, when the total cyanide concentration is 0.1 mg / L or more and 2 mg / L or less, the preferred amount of oxidizing agent used is 12 mg / L or less.

[0050] 1-1-4-2. Amount of reaction accelerator used (amount added) In the treatment method of the present invention, the amount of reaction accelerator used (amount added) to cyanide-containing wastewater is not particularly limited, but it is preferable to add it in an amount equal to or greater than the theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid. The "theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid" for the reaction accelerator can be calculated by measuring the cyanide content in the water to be treated. That is, based on the above formula (3), it is 0.25 times the cyanide content (moles) in the water to be treated. Furthermore, a suitable upper limit for the amount of reaction accelerator used is preferably 3 times or less the theoretical equivalent of the reaction with all cyanide, more preferably 2.7 times or less, and even more preferably 1.8 times or less. When the total cyanide concentration of the treated water is to be 0.1 to 2 mg / L, it is preferable to use a reaction accelerator in an amount that is between 1 and 1.8 times the theoretical equivalent required to decompose the total cyanide into nitrogen and carbonic acid. Furthermore, when reducing the total cyanide concentration of the treated water to less than 0.1, it is preferable to use a reaction accelerator that is at least 2 times and no more than 3 times the theoretical equivalent required to decompose the total cyanide into nitrogen and carbonic acid, and more preferably at least 2.5 times and no more than 2.8 times.

[0051] The amount of reaction accelerator used (amount added) per 1 mg / L of total cyanide concentration in the water to be treated is not particularly limited, but in terms of active ingredients, the preferred lower limit is preferably 1.0 mg / L or more, more preferably 1.2 mg / L or more, the preferred upper limit is preferably 3.0 mg / L or less, more preferably 2.7 mg / L or less, and further, when the total cyanide concentration is 0.1 mg / L or more and 2 mg / L or less, the preferred amount of reaction accelerator used is 2.0 mg / L or less.

[0052] 1-2-4-3. Amount of copper salt used (amount added) In the treatment method of the present invention, it is preferable to add copper salt to the cyanide-containing wastewater in an amount less than or equal to the theoretical equivalent of copper. Furthermore, in the treatment method of the present invention, the amount of copper salt added to the cyanide-containing wastewater is preferably less than or equal to the theoretical equivalent that reacts with all the cyanide, as described in the "Theoretical Equivalent of Copper" above. This is because the "Theoretical Equivalent of Copper" can be calculated based on the assumption that all the cyanide is ferricyanine. In the present invention, since the proportion of ferricyanine differs at each treatment site, the "maximum" amount of copper salt used is set. However, by continuously monitoring and analyzing water quality data such as the proportion of iron cyano complexes at each treatment site, it is possible to derive factors that can estimate the proportion of iron cyano complexes, ferrocyanine, and ferricyanine, and thus incorporate the factors obtained at each site into the "Theoretical Equivalent of Copper."

[0053] In the treatment method of the present invention, the amount of copper salt added to the cyanide-containing wastewater is preferably less than or equal to the theoretical equivalent amount that reacts with the total cyanide. However, based on the total cyanide that cannot be treated by the oxidizing agent and reaction accelerator alone, it is desirable to add an amount of about 0.8 to 1.2 times (more preferably 0.9 to 1.1 times) the theoretical equivalent amount that copper reacts with the total cyanide. The "theoretical equivalent amount that reacts with the total cyanide" for the copper salt can be calculated by measuring the cyanide content in the water to be treated. Furthermore, a preferred upper limit for this is preferably 1 time or less, more preferably 0.8 times or less, and a preferred lower limit is preferably 0.1 times or more, more preferably 0.2 times or more, the theoretical equivalent amount that reacts with the total cyanide. When the total cyanide concentration of the treated water is to be 0.1 to 2 mg / L, the amount of copper salt used should preferably be less than or equal to the theoretical equivalent of the reaction with the total cyanide, and more preferably 0.8 times or less. Furthermore, when reducing the total cyanide concentration of the treated water to less than 0.1 mg / L, it is preferable to use a copper salt amount that is 0.7 times or less the theoretical equivalent of the reaction with the total cyanide.

[0054] The amount of copper salt used (amount added) per 1 mg / L of total cyanide concentration in the water to be treated is not particularly limited, but in terms of solid copper equivalent, the preferred lower limit is preferably 1 mg / L or more, more preferably 2 mg / L or more, and the preferred upper limit is preferably 10 mg / L or less, more preferably 8 mg / L or less, even more preferably 7 mg / L or less, and even more preferably 2 mg / L or more and 7.0 mg / L or less.

[0055] 1-2-4-4. Oxidizing agent: Reaction accelerator: Copper salt usage ratio (addition ratio) In the processing method of the present invention, the ratio of oxidizing agent:reaction accelerator:copper salt used (addition ratio), when the oxidizing agent is considered to be 1 in molar ratio (mmol / L), preferably the lower limit is 0.01 or more for reaction accelerator and 0.05 or more for copper salt, more preferably 0.03 or more for reaction accelerator and 0.08 or more for copper salt, and preferably the upper limit is 0.1 or less for reaction accelerator and 0.2 or less for copper salt, more preferably 0.08 or less for reaction accelerator and 0.15 or less for copper salt.

[0056] 1-2-4-5. Processing conditions In the treatment method of the present invention, it is preferable to set the water temperature of the cyanide-containing wastewater (preferably the water temperature during the cyanide treatment reaction) to preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher, thereby increasing the rate of the cyanide treatment reaction. Increasing the rate of cyanide decomposition shortens the contact time between the treated water containing free residual chlorine and the wetted material made of steel or the like, thereby suppressing corrosion of the wetted material. To reduce heating costs, the water temperature of the cyanide-containing wastewater is preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower. In the treatment method of the present invention, the pH of the cyanide-containing wastewater is not particularly limited, and it is not necessary to adjust the pH in particular. However, it is preferable that the pH of the water to be treated (at 20°C) be in the alkaline range (pH 8 or higher).

[0057] The treatment method of the present invention can reduce the total cyanide concentration in the treated water to 2.0 mg / L or less, and more preferably to less than 0.1 mg / L.

[0058] 1-2-5.Optional ingredients In the processing method of the present invention, any drug can be appropriately mixed in, as long as it does not impair the effects of the present invention. Examples of optional chemicals include, but are not limited to, pH adjusters (acids and alkalis), corrosion inhibitors (corrosion inhibitors), scale inhibitors, slime control agents, flocculants, surfactants, solvents or dispersion media such as water, dispersing enzymes, disinfectants, and defoamers. Various chemicals that can be used for cyanide treatment may also be used. One or more of these can be appropriately selected.

[0059] 1-3. Processing method according to the present invention The processing method of the present invention will be described below with reference to Figure 1, but the present invention is not limited thereto. The method for treating cyanide-containing wastewater of the present invention can be applied to water systems that treat cyanide-containing wastewater. The aqueous system of the present invention is not particularly limited as long as it can treat cyanide-containing wastewater. The aqueous system preferably comprises, for example, a cyanide treatment reaction tank (or reaction channel), a coagulation tank, a sedimentation tank, and a filtration tank, and these tanks may be apparatus or systems (e.g., reaction apparatus or reaction system). A neutralization tank may further be included. Furthermore, the treatment method of the present invention can shorten the reaction time for cyanide treatment, allowing for a smaller reaction vessel, and also making it possible to use a flow channel (such as piping) as a reaction vessel. Preferably, this reaction channel is configured such that the chemical and cyanide-containing wastewater can be mixed by the flow.

[0060] Furthermore, it is preferable that the aqueous system of the present invention be equipped with each chemical addition device so that it can be added to the appropriate and necessary locations (such as tanks and flow paths). It is also preferable to attach a stirring device to each location for stirring the water to be treated. The aqueous system of the present invention may be equipped with a separate chemical addition device for each chemical. If a separate chemical addition device is provided for each chemical, the three chemicals may be directly added to the water to be treated and mixed, or a mixing tank for mixing two or three liquids before adding them to the water to be treated may be provided between each chemical device and the reaction tank. Furthermore, the number of drug dispensing devices may be set to 1, 2, or 3, depending on whether the composition is one-component, two-component, or three-component. Furthermore, in the present invention, when controlling the amount of oxidizing agent used by ORP measurement, it is preferable to provide at least one drug addition device for adding the oxidizing agent in the aqueous system.

[0061] Furthermore, it is preferable to provide the aqueous system of the present invention with a measuring device for measuring the pH and / or ORP of the treated water. Furthermore, the aqueous system of the present invention may be provided with a storage tank for storing raw water in front of the reaction tank. Since the treatment method of the present invention can shorten the reaction time, each chemical can be added directly to the raw water being introduced, so a storage tank does not need to be used, thereby improving the treatment efficiency. Furthermore, the aqueous system of the present invention may include an intermediate water tank between the filtration tank and the neutralization tank.

[0062] The aqueous system using the treatment method of the present invention will be explained with reference to Figure 1, but is not limited thereto. The water system 100 of the present invention preferably comprises the devices in the order shown in Figure 1. Specifically, the total amount of cyanide can be removed or reduced in the following order: raw water (water to be treated (L1)) → cyanide treatment reaction device 1 → coagulation device 2 → sedimentation device 3 → filtration device 4 → discharge (treated water) (L5). Furthermore, the water system of the present invention is preferably a circulating system L6 that allows the treated water to be combined with raw water as needed. The circulating system preferably includes piping and flow paths for supplying the treated water to the raw water from necessary locations (devices, piping, flow paths, etc.) and for circulation. This allows for cyanide treatment by circulating the treated water, preventing the discharge of water with a cyanide concentration exceeding the standard value to the outside. Furthermore, it is preferable that each of the reaction apparatus 1, coagulation apparatus 2, sedimentation apparatus 3, and filtration apparatus 4 be equipped with a stirring device.

[0063] Furthermore, it is preferable that the reaction apparatus 1 be equipped with an additive device 5 for adding the agent of the present invention. Furthermore, in the present invention, it is preferable to add the oxidizing agent, reaction accelerator, and copper salt simultaneously or at different times by utilizing the drug addition device 5 or by newly equipping the device with a drug addition device. The chemical addition device 5 may have separate addition devices 5a, 5b, and 5c for each chemical, and it is preferable that the three chemicals of the present invention and the cyanide-containing wastewater are mixed in the reaction tank 1 and treated with cyanide. For example, it is preferable that the aqueous system of the present invention be equipped with an oxidizing agent addition device 5a, a reaction accelerator addition device 5b, a copper salt addition device 5c, etc. Alternatively, the chemical addition device may be one that adds a mixture of two or three of the oxidizing agent, reaction accelerator, and copper salt to the water to be treated. Furthermore, because the cyanide treatment performance of the present invention is good in the aqueous system of the present invention, the reaction vessel 1 can be made smaller, and the reaction channel 1 may be a pipe or similar.

[0064] Furthermore, it is preferable that the coagulation device 2 and the sedimentation device 3 also be equipped with an additive device 6 for adding a coagulant and an additive device 7 for adding a precipitant, respectively. The water system of the present invention allows treated water that meets the standard value to be discharged. Furthermore, even if the standard value is not met, cyanide treatment can be performed again by the circulation system (L6). In Figure 1, the water is shown to be circulated after passing through the filtration device 4, but the circulation can occur at one or more locations, and from any location, including one, two or three or more of the reaction device 2, coagulation device 2, and sedimentation device 3.

[0065] Incidentally, the processing method of the present invention can also be realized by a control unit including a CPU or the like in a device (for example, a computer, a PLC, etc.) for managing cyanide treatment of cyanide-containing wastewater. Further, the processing method of the present invention can be stored as a program in hardware resources provided with a recording medium (non-volatile memory (such as a USB memory), SSD, HDD, CD, etc.), and realized by the control unit. It is also possible to provide a cyanide treatment system for cyanide-containing wastewater that controls the addition of a chemical to the water to be treated by the control unit, or a device including the control unit or the system. Further, the management device may be provided with an input unit such as a keyboard, a communication unit such as a network, a display unit such as a display, and the like.

[0066] 1-4. Each measurement method used in the present invention <Bromine compound measurement method> The bromine compound (Br - ) in the present technology can be analyzed based on the method of JIS-K0101 (1998) 28.4 to measure the concentration.

[0067] <pH measurement method and ORP measurement method> pH and ORP can be measured using a general pH meter or ORP meter.

[0068] <Total cyanide measurement method> The total cyanide concentration in the sample can be measured in accordance with JIS K0102.

[0069] <2. Cyanide-containing wastewater treatment agent of the present invention, chemical kit for treating cyanide-containing wastewater> The present invention can provide a cyanide treatment agent that is an agent for treating cyanide in cyanide-containing wastewater and contains an oxidizing agent, a reaction accelerator, and a copper salt. Further, the present invention can provide a chemical kit for treating cyanide-containing wastewater composed of (a) an oxidizing agent, (b) a reaction accelerator, and (c) a copper salt.

[0070] In the agent or chemical kit of the present invention, explanations of technical features, components, etc., that are common with the above-described <1. Method for treating cyanide-containing wastewater of the present invention> will be omitted as appropriate. The amount of copper salt used, the amount of oxidizing agent and reaction accelerator used, and their ratios in this technology will be omitted as appropriate if they are the same as the content and mass content ratio of each component in the above-described <1. Method for treating cyanide-containing wastewater of the present invention>. The oxidizing agent is preferably a hypochlorite, and more preferably an alkali metal hypochlorite. The reaction accelerator is preferably bromine or a bromine compound, and more preferably an alkali metal bromide salt. In the agent or drug kit of the present invention, the content and molar ratio of the oxidizing agent, the reaction accelerator, and the copper salt are preferably such that they are used in the amounts described in <1.> above relative to the aqueous system. Furthermore, the agent or drug kit of the present invention does not need to contain a pH adjuster.

[0071] <3. Uses of copper salts (improvement of cyanide treatment)> The present invention can provide a method for improving the treatment of cyanide in wastewater using an oxidizing agent and a reaction accelerator by mixing in copper salts. The present invention provides an agent for improving the treatment of cyanide in wastewater using an oxidizing agent and a reaction accelerator, with a copper salt as the active ingredient. The present invention provides a method for reducing the amount of oxidizing agents and reaction accelerators used when treating cyanide in wastewater, characterized by using a copper salt as an active ingredient in combination with the oxidizing agent and reaction accelerator. The present invention provides an agent that reduces the amount of oxidizing agent and reaction accelerator used when treating cyanide in wastewater, and is characterized by using a copper salt as an active ingredient in combination with an oxidizing agent and a decomposition accelerator.

[0072] In this invention, explanations of technical features, configurations, etc., that are common to the above-mentioned <1. Method for treating cyanide-containing wastewater according to the present invention> and <2. Cyanide-containing wastewater treatment agent and chemical kit for treating cyanide-containing wastewater according to the present invention> will be omitted as appropriate. The amount of copper salt used, the amount of oxidizing agent and reaction accelerator used, and their ratios, etc., in this technology will be omitted as appropriate if they are the same as the content and mass content ratios of each component in the above-mentioned <1. Method for treating cyanide-containing wastewater according to the present invention> and <2. Cyanide-containing wastewater treatment agent and chemical kit for treating cyanide-containing wastewater according to the present invention>.

[0073] The copper salt used in the present invention has the following effects when treating cyanide-containing wastewater: (1) When mixed with the copper salt, it improves the treatment of cyanide in the wastewater by the oxidizing agent and reaction accelerator; and (2) When used in combination with the oxidizing agent and reaction accelerator as an active ingredient, it reduces the amount of oxidizing agent and / or reaction accelerator used. Furthermore, preferably, the copper salt used in the present invention can reduce the amount of oxidizing agent used.

[0074] Furthermore, the copper salt-containing composition of the present invention can contain various components expected to have different effects as active ingredients, and can be used as an agent containing these various components. The copper salt-containing composition of the present invention can be used as is, with each component being used individually, or it can be used in combination with acceptable ordinary individual components or diluents.

[0075] Furthermore, the copper salt used in the present invention can provide a composition or use thereof for purposes such as the manufacture of cyanide treatment agents for cyanide-containing wastewater as described above. Furthermore, the copper salt of the present invention can be used as an active ingredient in the composition used in the above-described manufacturing method, use, and usage method, as an agent that reduces the amount of cyanide treatment enhancer used in cyanide-containing wastewater, or an oxidizing agent and / or reaction accelerator used in cyanide-containing wastewater. Furthermore, the cyanide treatment enhancer or the cyanide usage reducer in this technology can be used to manufacture various formulations or compositions having the effects described above or for the purposes described above. The present invention may also provide a cyanide treatment enhancer or a cyanide usage reducer, which contains a copper salt as an active ingredient. The present invention can also provide a method for improving cyanide treatment or reducing the amount of cyanide used, using copper salts. The present invention may also provide a copper salt or the use thereof for improving the cyanide treatment or for reducing the amount used.

[0076] The present invention can also employ the following configuration. [1] A method for treating cyanide-containing wastewater, comprising mixing an oxidizing agent, a reaction accelerator, and a copper salt with the cyanide-containing wastewater. [2] The wastewater treatment method according to [1], wherein the oxidizing agent is a hypochlorite. [3] The wastewater treatment method according to [1] or [2], wherein the reaction accelerator is bromine and / or a bromine compound. [4] A wastewater treatment method according to any one of [1] to [3] above, wherein the mixing reduces the total cyanide in the wastewater. [5] The wastewater treatment method according to any one of [1] to [4] above, wherein the cyanide contains free cyanide and / or cyanide compounds. [6] The wastewater treatment method according to any one of [1] to [5] above, wherein the amount of oxidizing agent added to the wastewater is equal to or greater than the theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid, and is added in an amount no more than three times that theoretical equivalent. [7] The wastewater treatment method according to any one of [1] to [6] above, wherein the amount of copper salt added to the wastewater is less than or equal to the theoretical equivalent amount of copper that reacts with the total cyanide.

[0077] [8] A cyanide treatment agent that treats cyanide in cyanide-containing wastewater, comprising an oxidizing agent, a reaction accelerator, and a copper salt, and the use thereof. Also, the use of an oxidizing agent, a reaction accelerator, and a copper salt for manufacturing a cyanide treatment agent, or an oxidizing agent, a reaction accelerator, and a copper salt for use in cyanide treatment. [9] A chemical kit for treating cyanide-containing wastewater, comprising (a) an oxidizing agent, (b) a reaction accelerator, and (c) a copper salt.

[10] A method for reducing the amount of oxidizing agent and reaction accelerator used when treating cyanide in wastewater, characterized in that a copper salt is used in combination with the oxidizing agent and reaction accelerator as an active ingredient.

[11] In any of the cyanide treatment agents described in [8] above, their use or use for manufacturing cyanide treatment agents, the chemical kit described in [9] above, or the method for reducing the amount used described in

[10] above, the oxidizing agent is preferably a hypochlorite.

[12] In any one of the above [8] to

[11] , it is preferable that the reaction accelerator is bromine and / or a bromine compound.

[13] In any one of the above [8] to

[12] , it is preferable to reduce the total cyanide in the wastewater by the mixing.

[14] In any one of the above [8] to

[13] , it is preferable that the cyanide contains free cyanide and / or cyanide compounds.

[15] In any one of the above [8] to

[14] , it is preferable that the amount of oxidizing agent added to the wastewater be 1 to 3 times the theoretical equivalent amount required to decompose the total cyanide into nitrogen and carbonic acid.

[16] In any one of the above [8] to

[15] , it is preferable that the amount of copper salt added to the wastewater is less than or equal to the theoretical equivalent of copper that reacts with the total cyanide. [Examples]

[0078] Embodiments of the present invention will be described with reference to the following examples and comparative examples. However, the scope of the present invention is not limited to these examples.

[0079] [Test 1 (Examples 1 and 2)] In Experiment 1, the precipitate in the test water was not specifically separated, and water quality analysis was performed on the supernatant portion. 100 mL of test water was placed in a 1000 mL beaker, the water temperature was maintained at 70°C, and each chemical was added to achieve the concentrations shown in Table 1. The mixture was then stirred with a stirrer for 10 minutes. No pH adjustment was performed at this time. Each measurement value was determined based on the measurement methods used in the present invention described in <1-4. Measurement Methods Used in the Invention> above.

[0080] <Experimental conditions> • Test water: Steelworks wastewater • Chemicals: (a) Sodium hypochlorite (12%), (b) NaBr (40%), (c) Copper(II) sulfate (5.7%) Water quality: pH 8.8 (20℃), total cyanide: 6.1 mg / L, ammonium ions: 60 mg / L ·Water temperature: 70℃ • Reaction time: 10 minutes

[0081] <Example 1 (No. 1)> Drug usage: (a) Sodium hypochlorite: 400 mg / L, (b) NaBr: 20 mg / L, (c) Copper(II) sulfate: 100 mg / L Treated water after cyanide treatment: Total cyanide: 0.1 mg / L, ORP: 135 mV

[0082] <Example 2 (No. 2)> Drug usage: (a) Sodium hypochlorite: 800 mg / L, (b) NaBr: 40 mg / L, (c) Copper(II) sulfate: 200 mg / L Treated water after cyanide treatment: Total cyanide: less than 0.1 mg / L, ORP: 141 mV

[0083] Table 1 shows the respective additive amounts, treated water measurement results, and theoretical equivalents for Test 1 (Examples 1 and 2). As shown in Table 1, in wastewater containing ammonium ions, the total cyanide concentration in the treated water was reduced to 0.1 mg / L by using 1.1 times (No. 1) and 1.2 times (No. 2) the theoretical equivalent of sodium hypochlorite required to decompose the total cyanide into CO2 and N2.

[0084] [Table 1]

[0085] [Test 2 (Examples 3, 4, Comparative Example 1, and Comparative Example 2)] <Experimental conditions> In Experiment 2, the precipitate in the test water was not specifically separated, and water quality analysis was performed on the supernatant portion. 100 mL of test water was placed in a 1000 mL beaker, the water temperature was maintained at 70°C, and each chemical was added to achieve the concentrations shown in Table 2. The mixture was then stirred with a stirrer for 10 minutes. No pH adjustment was performed at this time. Each measurement value was determined based on the measurement methods used in the present invention described in <1-4. Measurement Methods Used in the Invention> above.

[0086] • Test water: Steelworks wastewater • Chemicals: (a) Sodium hypochlorite (12%), (b) NaBr (40%), (c) Copper(II) sulfate (5.7%) Water quality: pH 8.2 (20℃), Total cyanide: 7.1 mg / L ·Water temperature: 70℃ • Reaction time: 10 minutes

[0087] <Example 3 (No. 1)> Drug usage: (a) Sodium hypochlorite: 600 mg / L, (b) NaBr: 30 mg / L, (c) Copper(II) sulfate: 100 mg / L Treated water after cyanide treatment: Total cyanide: 2.0 mg / L, ORP: 284 mV <Example 4 (No. 2)> Drug usage: (a) Sodium hypochlorite: 600 mg / L, (b) NaBr: 30 mg / L, c) Copper(II) sulfate: 300 mg / L Treated water after cyanide treatment: Total cyanide: 1.5 mg / L, ORP: 290 mV

[0088] [Comparative Example 1 (No. 3)] Drug usage: (a) Sodium hypochlorite: 600 mg / L, (b) NaBr: 30 mg / L, (c) Copper(II) sulfate: 0 mg / L Treated water after cyanide treatment: Total cyanide: 3.4 mg / L, ORP: 264 mV [Comparative Example 2 (No. 2)] Drug usage: (a) Sodium hypochlorite: 0 mg / L, (b) NaBr: 0 mg / L, (c) Copper(II) sulfate: 100 mg / L Treated water after cyanide treatment: Total cyanide: 7.3 mg / L, ORP: 125 mV

[0089] Table 2 shows the respective additive amounts, treated water measurement results, and theoretical equivalents for Test 2 (Examples 3 and 4, Comparative Examples 1 and 2). It was confirmed that the three-part treatment method in Examples 3 and 4, which further includes a copper salt, was more effective in treating total cyanide in cyanide-containing wastewater than the two-part treatment method in Comparative Examples 1 and 2, which consisted of sodium hypochlorite and NaBr. Furthermore, since the copper sulfate aqueous solution alone was not able to treat all cyanide, it is presumed that the combined use of copper sulfate, sodium hypochlorite, and NaBr promotes the binding or decomposition of total cyanide.

[0090] [Table 2]

[0091] The results above show that by using an oxidizing agent, a reaction accelerator, and a copper salt in combination, all cyanide in wastewater could be efficiently treated. Furthermore, by using a copper salt, the amount of oxidizing agent and reaction accelerator used could be significantly reduced. In this case, cyanide treatment was possible even with an amount of oxidizing agent equivalent to the theoretical equivalent required to decompose all cyanide into nitrogen and carbonic acid. Moreover, by using a copper salt in combination, the cyanide treatment reaction could be carried out in a short time of about 10 minutes. Therefore, cyanide treatment is possible even with a reaction time of 10 minutes or less. In addition, good cyanide treatment was possible with a copper salt used in amounts less than the theoretical equivalent of the oxidizing agent. Furthermore, efficient cyanide treatment was possible with a copper salt used in amounts less than the theoretical equivalent required to react with all cyanide.

[0092] For example, when performing total cyanide treatment on wastewater with a total cyanide concentration of 2 mg / L and an ammonium ion concentration of 200 mg / L, the amount of sodium hypochlorite (12%) to be added will be as follows in the conventional technology and in the present invention. In conventional technology, sodium hypochlorite (12%) = 2 × 60 + 200 × 52 = 10520 mg / L. In this invention, sodium hypochlorite (12%) = 120 mg / L. Thus, compared to conventional technology, only 1% sodium hypochlorite (12%) needs to be added. Another advantage is that the amount of reaction accelerator (brominated compound) added can be reduced accordingly. There are no particular restrictions on the amount of bromine compounds added, as long as it is less than or equal to the theoretical equivalent amount of bromine that reacts with hypochlorous acid. Furthermore, while there are no particular restrictions on the amount of copper salt added, based on the total cyanide (specifically ferricyanide) that cannot be treated by the oxidizing agent and decomposition accelerator alone, it is sufficient to add about 10 times the theoretical equivalent amount of copper that reacts with the total cyanide. [Explanation of Symbols]

[0093] 1: Reaction tank (reaction channel), 2: Coagulation tank, 3: Sedimentation separation tank, 4: Filtration separation tank, 5, 6, 7: Chemical addition device, 100 water system, L1: Raw water (water to be treated) introduction channel, L2: Channel, L3: Channel, L4: Channel, L5: Treated water channel (discharge), L6: Circulation channel (circulation system)

Claims

1. An oxidizing agent, a reaction accelerator, and a copper salt are mixed into the cyanide-containing wastewater before coagulation treatment. The ratio of the oxidizing agent, the reaction accelerator, and the copper salt used is such that, when the oxidizing agent is considered to be 1, the ratio is 0.01 or more and 0.1 or less for the reaction accelerator and 0.05 or more and 0.2 or less for the copper salt. The oxidizing agent is hypochlorous acid or a salt thereof. The reaction accelerator is one or more selected from alkali metal bromides, ammonium bromides, hydrobromic acids, and amine bromides. A method for treating cyanide-containing wastewater.

2. The wastewater treatment method according to claim 1, wherein the total cyanide in the wastewater is reduced by the aforementioned mixing.

3. The wastewater treatment method according to claim 1 or 2, wherein the cyanide comprises free cyanide and / or cyanide compounds.

4. The wastewater treatment method according to claim 1 or 2, wherein the amount of oxidizing agent added to the wastewater is such that it is 1 to 3 times the theoretical equivalent amount required to decompose all cyanide into nitrogen and carbonic acid.

5. The wastewater treatment method according to claim 1 or 2, wherein the amount of copper salt added to the wastewater is less than or equal to the theoretical equivalent amount of the oxidizing agent.

6. The wastewater treatment method according to claim 1 or 2, wherein the amount of copper salt added to the wastewater is less than or equal to the theoretical equivalent amount of copper that reacts with the total cyanide.

7. An agent for treating cyanide in cyanide-containing wastewater before coagulation treatment, It contains an oxidizing agent, a reaction accelerator, and a copper salt. The ratio of the oxidizing agent, the reaction accelerator, and the copper salt used is such that, when the oxidizing agent is considered to be 1, the ratio is 0.01 or more and 0.1 or less for the reaction accelerator and 0.05 or more and 0.2 or less for the copper salt. The oxidizing agent is hypochlorous acid or a salt thereof. The reaction accelerator is one or more selected from alkali metal bromides, ammonium bromides, hydrobromic acids, and amine bromides. A one-component cyanide treatment agent.

8. (a) an oxidizing agent, (b) a reaction accelerator, and (c) a copper salt, The ratio of the oxidizing agent, the reaction accelerator, and the copper salt used is such that, when the oxidizing agent is considered to be 1, the ratio is 0.01 or more and 0.1 or less for the reaction accelerator and 0.05 or more and 0.2 or less for the copper salt. The oxidizing agent is hypochlorous acid or a salt thereof. The reaction accelerator is one or more selected from alkali metal bromides, ammonium bromides, hydrobromic acids, and amine bromides. A chemical kit for treating cyanide-containing wastewater before coagulation treatment.

9. A method for reducing the amount of oxidizing agent and reaction accelerator used when treating cyanide in wastewater before coagulation treatment, using a copper salt. The ratio of the oxidizing agent, reaction accelerator, and copper salt used is such that, when the oxidizing agent is considered to be 1, the ratio is 0.01 or more and 0.1 or less for the reaction accelerator and 0.05 or more and 0.2 or less for the copper salt. The oxidizing agent is hypochlorous acid or a salt thereof. The reaction accelerator is one or more selected from alkali metal bromides, ammonium bromides, hydrobromic acids, and amine bromides. The aforementioned reduction method.

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