JP6061024B2 - Method and apparatus for treating wastewater containing heavy metals - Google Patents

Description

The present invention relates to a method and apparatus for treating wastewater, particularly heavy metal-containing wastewater.
This application claims priority based on Japanese Patent Application No. 2014-036853 for which it applied to Japan on February 27, 2014, and uses the content here.

Many heavy metals used in various industrial fields have harmful effects on the human body and the environment. Therefore, when wastewater containing these materials is discharged into sewers or public water bodies, wastewater standards, that is, wastewater standards such as the Sewerage Law or Water Pollution Control Law, etc. are applied, and some treatment Necessary.
Furthermore, in some regions, there are cases where regulations are tightened due to concerns about environmental pollution, and regulations are imposed with strict standards exceeding the above effluent standards.
Thus, the discharge of waste water containing heavy metals is in a situation where it is more strictly regulated. In particular, in Japan, in the sewerage law, zinc and its compound are 2 mg / L or less for zinc, copper and its compound are 3 mg / L or less for copper, and in China, 2 mg / L or less for zinc and 0. Strict water quality standards of 5 mg / L or less are established, and effective treatment techniques are required.

In response to these problems, an efficient method for treating zinc and copper from heavy metal-containing wastewater has been proposed.
For example, as a method for treating zinc and copper from heavy metal-containing wastewater, it is a method for treating metal mine wastewater. While supplying metal mine wastewater containing acid and heavy metals into the first container, After the treatment to oxidize part of the divalent iron ions to trivalent iron ions, the waste water is put into the second container, and the pH of the waste water is controlled to 3 to 5 to control arsenic and trivalent. After the precipitation of the iron ion compound, the precipitate is subjected to a solid-liquid separation process, the liquid is put into a third container, the pH of the waste water is controlled to 3 to 5, and the iron-oxidizing bacteria are removed. And after blowing air and oxidizing the divalent iron ion to the trivalent iron ion and precipitating the iron hydroxide at the same time, the precipitate is subjected to a solid-liquid separation process. Put into a container, control the pH of the waste water to 6-10, at least one of copper and zinc Zinc and processing method of the copper to precipitate the elemental metal hydroxides (Patent Document 1).

  However, in the above method, the treatment apparatus is complicated because it is necessary to carry out the reaction in multiple stages, and in the wastewater, there are impurities in the wastewater, particularly when a compound forming a metal complex such as a chelating agent called a builder exists. It was difficult to treat zinc and copper. In particular, zinc and copper were extremely difficult to treat in the presence of impurities because the pH at the time of insolubilization did not become the theoretical value.

JP 2004-202488 A

Various methods have been studied for removing zinc and copper in wastewater, but these methods are easily affected by contaminants in the wastewater. There is a problem of incurring complexity and cost increase.
An object of the present invention is to solve such a conventional problem.

  The present invention provides a wastewater treatment method capable of removing heavy metals, particularly zinc and copper, from wastewater, particularly heavy metal-containing wastewater, particularly wastewater containing zinc and copper, with high treatment efficiency.

That is, this invention has the following aspect.
[1] A wastewater treatment method for removing zinc and copper from wastewater containing zinc and copper, including the following steps (i) and (ii):
(I) an insolubilization step in which an oxidizing agent and a coprecipitation agent that is magnesium and / or a salt thereof are allowed to act on the wastewater to insolubilize zinc and copper in the wastewater; and (ii) the step (i) A separation step of removing the insolubilized zinc and copper from the waste water attached to the membrane by membrane filtration .
[2] The wastewater treatment method according to [1], wherein the insolubilization step includes a pH adjustment step.
[ 3 ] The wastewater treatment method according to [1] or [2] , wherein the wastewater contains a chelating agent.
[ 4 ] The wastewater treatment method according to any one of [1] to [ 3 ], wherein the wastewater is plating wastewater.
[ 5 ] The waste water treatment according to any one of [1] to [ 4 ], wherein the oxidizing agent is selected from the group consisting of chlorine oxides, chloric acids and salts thereof, and hydrogen peroxide. Method.
[ 6 ] The wastewater treatment method according to any one of [1] to [ 5 ], wherein the pH of the wastewater is adjusted to be greater than 10 and 13 or less in the insolubilization step.
[ 7 ] In any one of [1] to [ 6 ], in the insolubilization step, the amount of action of the oxidizing agent is 0.5 to 20 times in terms of molar equivalent ratio with respect to the copper concentration in the waste water. The waste water treatment method according to claim 1.
[ 8 ] In the insolubilization step, any one of [1] to [ 7 ], wherein the amount of action of the coprecipitation agent is 20 to 1000 times in terms of molar equivalent ratio with respect to the zinc concentration in the waste water. The wastewater treatment method according to one item.
[ 9 ] 95% by weight or more of zinc contained in the waste water and 80% by weight or more of copper contained in the waste water are simultaneously removed, [1] to [ 8 ] Wastewater treatment method.
[ 10 ] Oxidation tank in which oxidant is allowed to act, coprecipitation tank in which coprecipitate is made of magnesium and / or salts thereof, insolubilization tank in which zinc and copper are insolubilized, and insolubilized zinc and copper by membrane filtration A wastewater treatment device for removing zinc and copper from wastewater containing zinc and copper, having a separation device for removal.
[ 11 ] Oxidation tank in which an oxidizing agent is applied, coprecipitation tank in which a coprecipitation agent that is magnesium and / or a salt thereof is applied, an insolubilization tank in which zinc and copper are insolubilized, and insolubilized zinc and copper by membrane filtration The waste water treatment apparatus according to [ 10 ], in which two or more tanks or apparatuses are integrated in the separation apparatus to be removed.
[ 12 ] The waste water treatment apparatus according to [ 10 ] or [ 11 ], having pH adjusting means for adjusting pH in the tank by adding acid or alkali to an insolubilizing tank for insolubilizing zinc and copper.

  According to the wastewater treatment method of the present invention, heavy metals can be removed from wastewater easily and with high efficiency. In particular, according to the wastewater treatment method of the present invention, zinc and copper in the wastewater are 95% by weight or more and 80% by weight or more, 97% by weight or more, 82.5% by weight or more, 97.3% by weight or more, respectively. 85.0 wt% or more, 98 wt% or more and 88 wt% or more, or 98.7 wt% or more and 88.5 wt% or more can be removed.

Hereinafter, the waste water treatment method of the present invention will be described.
The wastewater treatment method of the present invention is a method for removing heavy metals, particularly zinc and copper, from wastewater, particularly heavy metal-containing wastewater, especially wastewater containing zinc and copper, and includes the following steps (i) and (ii): It is a waste.
(I) an oxidant and a coprecipitation agent are allowed to act on the wastewater to insolubilize heavy metals in the wastewater; and (ii) the insolubilized heavy metals are removed from the wastewater subjected to the step (i). Separation process.
In the wastewater treatment method of the present invention, the pretreatment heavy metal concentration measurement step for determining the amount of action of the oxidizing agent and the coprecipitation agent to act on the wastewater to be treated in the insolubilization step, and / or A post-treatment heavy metal concentration measurement step for determining the removal rate of heavy metals in the waste water after the separation step may be included. The method for measuring the concentration of heavy metals in the waste water in these concentration measurement steps can be performed according to JIS K 0102 or according to JIS K 0102-53.3, particularly for zinc, and JIS K 0102-52 for copper. The concentration can be determined according to .4. These measurements can also be performed through monitoring using a computer.

  The wastewater to be treated by the wastewater treatment method of the present invention is preferably heavy metal-containing wastewater, and in particular, wastewater containing at least zinc and copper is preferred. Here, the heavy metal is a metal having a specific gravity of 4 or more, and includes chromium, copper, zinc, cadmium, nickel, mercury, lead, iron and the like. These heavy metals may be contained alone, but are usually contained in a state where a plurality of heavy metals are mixed. Moreover, zinc and copper can be mentioned as a heavy metal removed from waste water by the waste water treatment method of this invention. Moreover, the waste water treated by the waste water treatment method of the present invention may contain a chelating agent described later. Further, the wastewater treated by the wastewater treatment method of the present invention may be plating wastewater described later.

<Insolubilization process>
In step (i) in the wastewater treatment method of the present invention, an oxidizing agent and a coprecipitation agent are allowed to act on wastewater, particularly heavy metal-containing wastewater, particularly wastewater containing zinc and copper, and heavy metals in the wastewater, particularly zinc and copper. It is an insolubilization process which insolubilizes.

(Oxidant)
The oxidizing agent used in the present invention is a compound capable of transferring an oxygen atom or a substance that obtains electrons in an oxidation-reduction reaction, and chlorine oxide such as chlorine dioxide; hypochlorous acid, chlorous acid, chloric acid, Chloric acids including perchloric acid and salts thereof; hydrogen peroxide; Fenton; ozone; selected from the group consisting of radicals generated by UV or photocatalyst. Moreover, these oxidizing agents may be used alone or in combination with a plurality of oxidizing agents. Thereby, the metal chelate is destroyed, and it is considered that insolubilization of heavy metals can be promoted by causing the coprecipitation agent to act on the metal chelate.
Of these, chloric acids or salts thereof are preferable from the viewpoints of handleability and availability. Examples of chloric acid salts include sodium salts, potassium salts, calcium salts, magnesium salts, ammonium salts, and the like, with sodium hypochlorite being more preferred.
These oxidizing agents can also be used as a solution dissolved in a solvent. In that case, it is preferable to use an aqueous solution from the viewpoints of handleability and availability. In particular, an aqueous sodium hypochlorite solution is preferably used as the oxidizing agent.
The concentration when the oxidant is used as the solution may be a concentration that can be adjusted to a desired concentration in the wastewater when the oxidant solution acts on the wastewater.
If these oxidizing agents are used, the oxidation reaction easily proceeds quickly, and the overall processing speed can be increased.
Moreover, since these have high decomposition efficiency of complex-forming compounds having a chelating action such as EDTA and tartaric acid, they can prevent the inhibition of aggregation of insolubilized substances by the complex-forming compounds in the heavy metal insolubilization step. For this reason, the insolubilization process for a separation process can be performed more efficiently.
In particular, when sodium hypochlorite or a solution thereof is used as the oxidizing agent, the particle size of the heavy metal insolubilized product generated in the heavy metal insolubilization step tends to increase. When the particle size of the insolubilized material is larger, it is possible to suppress clogging of the pores of the filtration membrane in the membrane separation step described later, and the membrane flux can be maintained high.

The order of action of the oxidizing agent and the coprecipitation agent in the wastewater is not particularly specified, but it is preferable to act the coprecipitation agent after the action of the oxidizing agent from the viewpoint of insolubilization efficiency. The timing at which the coprecipitate is allowed to act depends on the amount of wastewater to be treated, but usually at room temperature or outside temperature, the oxidant is allowed to act on the wastewater and mixed by stirring, etc., for 0.1 to 50 hours, preferably The coprecipitation agent may be allowed to act after standing for about 0.2 to 30 hours, more preferably about 0.5 to 10 hours.
The order of the pH adjustment step for insolubilizing heavy metals in the present invention is not particularly specified, but it is desirable to carry out after the action step of the oxidizing agent and the coprecipitate from the viewpoint of ease of adjustment. The timing for performing the pH adjustment step depends on the amount of wastewater to be treated, but usually a coprecipitation agent is allowed to act on wastewater treated with an oxidant at room temperature or outside temperature, and mixed by stirring or the like. The pH adjustment step may be performed after leaving for about 50 hours, preferably 0.2 to 30 hours, more preferably about 0.5 to 10 hours.
The “action” means addition and / or mixing.

The amount of action of the oxidizing agent is preferably 0.5 to 20 times the molar equivalent ratio, more preferably 1.0 to 15 times, and 1.2 to 14 with respect to the copper concentration in the waste water. Double is more preferable, and 3.3 to 7.0 is particularly preferable.
If the amount of action of the oxidizing agent is equal to or greater than the lower limit, it is easy to increase the removal efficiency of zinc and copper from the wastewater as a whole, but it is particularly easy to increase the removal rate of copper from the wastewater. In addition, if the amount of action of the oxidant is not more than the upper limit value, it is easy to increase the removal efficiency of zinc and copper from the waste water as a whole, but it is particularly easy to increase the removal rate of zinc and the supply amount of the oxidant is small. Economical.
An oxidizing agent can be made to act in the oxidation tank which makes an oxidizing agent act. The oxidation tank is not particularly limited as long as it can store wastewater, but is preferably one that is not easily deteriorated by wastewater and an oxidizing agent. The means for adding the oxidizing agent to the oxidation tank is not particularly limited as long as the oxidizing agent can be added as a solid or as a liquid mixture such as a solution.

(Coprecipitant)
The coprecipitation agent in the present invention is for precipitating heavy metals that do not precipitate if separated alone in the wastewater when they are precipitated by their presence.
The coprecipitant used in the present invention is an alkaline earth metal and / or a salt thereof. That is, these coprecipitates may be used alone or in combination with a plurality of coprecipitates.
Especially, as an alkaline-earth metal, calcium or magnesium is preferable from a viewpoint of handleability and availability, and magnesium is more preferable. Examples of alkaline earth metal salts include halides such as chlorides and bromides, sulfates, carbonates, nitrates, phosphates, and the like. In particular, halides, especially chlorides are preferably used, and magnesium chloride is more preferably used.
Moreover, these coprecipitation agents can also be used as a solution dissolved in a solvent. In that case, it is preferable to use an aqueous solution from the viewpoints of handleability and availability. In particular, it is preferable to use magnesium chloride and / or magnesium chloride aqueous solution as a coprecipitation agent.
The concentration when the coprecipitate is used as a solution may be a concentration that can be adjusted to a desired concentration in wastewater when the coprecipitate solution is allowed to act on the wastewater.
When a magnesium salt solution containing magnesium and / or a salt thereof is used as a coprecipitation agent, clogging of pores of the filtration membrane by inorganic salts called scales can be suppressed when removing insolubles of heavy metals by membrane separation. High flux can be maintained.

The amount of action of the coprecipitation agent is preferably 20 to 1000 times the molar equivalent ratio with respect to the zinc concentration in the waste water, more preferably 40 to 400 times, still more preferably 50 to 200 times, 80 -170 times is particularly preferable.
If the amount of action of the coprecipitation agent is equal to or greater than the lower limit value, it is easy to increase the efficiency of removing zinc and copper from the waste water. Moreover, if the amount of action of the coprecipitation agent is not more than the upper limit value, the supply amount of the coprecipitation agent is small and economical.
The coprecipitation agent can be made to act in a coprecipitation tank in which the coprecipitation agent acts. The coprecipitation tank is not particularly limited as long as it can store wastewater, but a coprecipitation tank that is not easily deteriorated by wastewater, an oxidizing agent, and a coprecipitation agent is preferable. The means for adding the coprecipitation agent to the coprecipitation tank is not particularly limited as long as the coprecipitation agent can be added as a solid or as a liquid mixture such as a solution.

Insolubilization of heavy metals (for example, zinc and copper) is performed by insolubilizing heavy metals (especially zinc and copper) in the wastewater by causing the insolubilizer to act on the wastewater treated with the oxidizing agent and coprecipitation agent. This means that separation by such means is possible.
As the insolubilization method, there are a hydroxide method using a hydroxylating agent and a sulfide method using a sulfiding agent. In the case of the sulfide method, hydrogen sulfide may be generated, and therefore the hydroxide method is preferable from the viewpoint of safety.

The hydroxide method is a method in which a hydroxylating agent (hydroxide ion) and a target metal are reacted and precipitated as a metal hydroxide having low solubility. As the hydroxylating agent as the insolubilizing agent, sodium hydroxide, sodium carbonate, calcium hydroxide, magnesium hydroxide or the like is used. Since the amount of sludge generation is reduced, the hydroxide method using sodium hydroxide is more preferable.
On the other hand, the sulfide method is a method in which a sulfiding agent (sulfide ion) and a target metal are reacted and precipitated as a metal sulfide having low solubility. As the sulfurizing agent as the insolubilizing agent, sodium sulfide, hydrogen sulfide and the like are used.

These insolubilizers can also be used as a solution dissolved in a solvent. In that case, it is preferable to use an aqueous solution from the viewpoints of handleability and availability. In particular, sodium hydroxide and / or sodium hydroxide aqueous solution is preferably used as the insolubilizing agent.
The concentration when the insolubilizing agent is used as a solution may be a concentration that can be adjusted to a desired concentration in wastewater when the insolubilizing agent solution is allowed to act on the wastewater.
The timing at which the insolubilizing agent is allowed to act depends on the amount of wastewater to be treated, but usually the coprecipitation agent is allowed to act on wastewater that has been treated with an oxidizing agent at room temperature or outside temperature, and is mixed by stirring or the like. After leaving for about 50 hours, preferably 0.2 to 30 hours, more preferably about 0.5 to 10 hours, an insolubilizing agent may be allowed to act.

The insolubilizing agent can be allowed to act in an insolubilizing tank in which the insolubilizing agent acts. The insolubilization tank for insolubilizing heavy metals (for example, zinc and copper) in the wastewater is not particularly limited as long as the wastewater can be stored, but is preferably one that is not easily deteriorated by the wastewater, the oxidizing agent, the coprecipitation agent, and the insolubilizing agent. The means for adding the insolubilizing agent to the insolubilizing tank is not particularly limited as long as the insolubilizing agent can be added as a solid or as a liquid mixture such as a solution.
The insolubilization tank may include a pH adjusting means for performing the pH adjusting step of the waste water. The pH adjusting means is not limited as long as it can adjust the pH of the waste water in the insolubilization tank to a desired pH by adding acid or alkali as a solid or a liquid mixture such as a solution. Means equipped with a device and an alkali addition device, and the like. When the pH in the tank is adjusted by the pH adjusting means, heavy metals may be insolubilized. Although an acid addition apparatus and an alkali addition apparatus will not be specifically limited if an acid or an alkali can be added to an insolubilization tank, What is hard to degrade with an acid or an alkali is preferable. Moreover, when the pH adjustment means provided with the acid addition apparatus and the alkali addition apparatus is contained in an insolubilization tank, what is hard to degrade with an acid or an alkali is further preferable. Examples of the acid used in the pH adjustment step include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, organic acids such as oxalic acid, citric acid, formic acid and acetic acid, or mixtures thereof. Of these, hydrochloric acid or sulfuric acid, or a mixed solution thereof is preferable from the viewpoint of being an acid that does not affect the quality of the wastewater treatment water, and sulfuric acid or dilute sulfuric acid is particularly preferable from the viewpoint of handleability. Examples of the alkali used in the pH adjustment step include sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium carbonate and the like. Are preferably used. In addition, before performing a pH adjustment process, if the pH of the waste_water | drain to process is desired pH, a pH adjustment process can also be abbreviate | omitted.

In addition, it is also possible to perform the insolubilization operation and the pH adjustment step by the hydroxide method. As conditions for adjusting the pH by the hydroxide method, the pH in the wastewater is preferably from 10 to 13, and more preferably from 11 to 12.
If pH adjustment conditions are more than a lower limit, it will be easy to make the removal efficiency of heavy metals (for example, zinc and copper) from waste water high. Further, if the pH adjustment condition is equal to or lower than the upper limit value, it is possible to prevent the heavy metal from re-dissolving in the waste water, and the amount of the drug used for pH adjustment is small and economical.

<Separation process>
Examples of the separation method for removing insolubilized heavy metals (for example, zinc and copper) include membrane filtration, centrifugation, belt press, precipitation by a sedimentation basin, and the like. Among these, as a separation method, considering the continuity of treatment and the precipitation and particle size of insolubilized zinc and copper, membrane filtration using a separation membrane such as a batch type, filter press, cross flow type, immersion type, etc. is preferable. More preferred is cross-flow or immersion filtration.
(Filtration membrane)
The filtration membrane as a separation membrane used in the separation step of the step (ii) of the present invention is not particularly limited as long as it has filtration ability, but a hollow fiber membrane, a flat membrane, a tubular membrane, a monolith type membrane, etc. Can be mentioned. Among these, a hollow fiber membrane is preferable because of its high volume filling rate.
When a hollow fiber membrane is used as the filtration membrane, examples of the material include cellulose, polyolefin, polysulfone, polyvinylidene fluoride difluoride (PVDF), polytetrafluoroethylene (PTFE), and the like. Among these, as the material for the hollow fiber membrane, polyvinylidene difluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferable from the viewpoint of chemical resistance and resistance to pH change.
When a monolithic membrane is used as the filtration membrane, a ceramic membrane can be used.

As a form of membrane filtration, when the cross flow method is used, a membrane module containing a membrane for membrane filtration is, for example, a primary side that is in contact with the drainage of the filtration membrane in a housing and a filtrate water permeation side. The filtration membrane is fixed so that the secondary side is isolated, and the primary side of the filtration membrane in the housing is communicated with a reaction tank for insolubilizing heavy metals (for example, zinc and copper) in the wastewater by a circulation line. Good. Moreover, in the filtration by the cross flow method, the flow rate adjustment mechanism is provided on the circulation line connecting the outlet side of the membrane module and the reaction tank, or the secondary side is suctioned and filtered by a filtration pump or the like. By controlling the pressure, a pressure difference may be generated between the primary side and the secondary side, and filtration may be used.
In the case of performing the immersion type, a device that can perform membrane filtration in a state where the membrane module containing the membrane for membrane filtration is directly immersed in the insolubilization tank may be used.
Further, as the membrane module, a membrane module provided with aeration means for cleaning the membrane surface below the filtration membrane may be used. A well-known thing can be employ | adopted as said aeration means.

The average pore diameter of the micropores formed in the filtration membrane is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.5 μm. If the average pore diameter of the micropores is equal to or greater than the lower limit, the pressure required for membrane filtration can be easily reduced, and the concentration efficiency of metal aggregates can be easily increased. If the average pore diameter of the micropores is not more than the upper limit value, it is easy to suppress leakage of the metal aggregate into the filtrate.
The separation step of removing heavy metals from the waste water can be performed in a separation apparatus that removes insolubilized heavy metals. As the separation device, it is preferable to have a separation membrane such as a filtration membrane for separating insoluble heavy metals from the waste water. Therefore, the method for removing heavy metals in the separation device is preferably membrane separation.

  The treated water filtered by membrane filtration may be further subjected to removal of water pollutants such as organic matter and nitrogen as necessary. Further, the pH may be adjusted and discharged into a river or the like.

<Processing device>
The waste water treatment apparatus of the present invention includes (1) the oxidation tank in which an oxidizing agent is applied, (2) the coprecipitation tank in which a coprecipitation agent is applied, (3) the insolubilization tank in which heavy metals are insolubilized, and (4) The separation device for removing insoluble heavy metals is included. These tanks and devices may be separate tanks and devices, respectively, but two or more tanks or devices may be integrated. “Two or more tanks or devices are integrated” means, for example, that an oxidant is allowed to act on wastewater in an oxidation tank, and then the wastewater is transferred to a separately prepared coprecipitation tank and then the coprecipitate is added. Instead of acting, it means an embodiment in which an oxidizing agent is allowed to act on waste water in an oxidizing tank, and then a coprecipitation agent is further allowed to act in the tank. That is, after the operation performed in each tank and apparatus for the drainage, the next operation is performed in the same tank or without separately transferring the drainage to the tank or apparatus in which the next operation is performed. Means to be done in the device. That is, it means that the same tank has a plurality of functions such as the function of an oxidizing agent and a coprecipitation agent. As a specific aspect, an operation in the oxidation tank and the coprecipitation tank is performed in a single tank; an aspect in which the operation in the oxidation tank, the coprecipitation tank, and the insolubilization tank is performed in a single tank; The mode in which operation in a settling tank, an insolubilization tank, and a separation apparatus is performed in a single tank can be mentioned. Among them, since the processing equipment can be made compact and economical, an aspect in which operations other than the operation in the separation apparatus are performed in a single tank and the separation step is performed in the separation apparatus; or an oxidation tank, a coprecipitation tank, an insolubilization tank, An embodiment in which all operations in the separation apparatus are performed in a single tank is preferred.

  The present invention described above is a wastewater treatment method and a wastewater treatment apparatus for removing heavy metals (particularly zinc and copper) from wastewater, particularly heavy metal-containing wastewater, particularly wastewater containing zinc and copper. By these, the said heavy metal can be processed simultaneously from the said waste_water | drain. Also, if heavy metals in the waste water are simultaneously insolubilized and removed in a single reaction tank, the treatment equipment can be made compact and economical.

Examples of the wastewater to be treated according to the present invention include plating wastewater generated from a metal surface treatment plant such as a plating plant, etc., and a heavy metal and a compound that forms a metal complex by coordination with a heavy metal (hereinafter referred to as a metal complex). , "Complex forming compound").
On the other hand, a complex-forming compound is a compound that forms a metal complex centered on a heavy metal atom by coordination with any of heavy metals. Examples of complex-forming compounds include acidic cleaning components such as citric acid, gluconic acid, oxalic acid, tartaric acid, succinic acid, cyanide and salts thereof; EDTA, ethylenediamine, triethanolamine, ammonia (including ammonium salts), etc. Examples include amines. In addition, since a chelate complex is also contained in a metal complex, chelating agents, such as tartaric acid and EDTA, naturally correspond to a complex formation compound.
In addition to the heavy metal and the complex-forming compound, the waste water may contain a surfactant, a Lewis acid other than the complex-forming compound, as a cleaning component, and a pH adjusting component.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Measurement of zinc concentration]
The zinc concentration was measured by ICP emission spectroscopic analysis according to JIS K 0102-53.3.
[Measurement of copper concentration]
The copper concentration was measured by ICP emission spectroscopic analysis according to JIS K 0102-52.4.

[Example 1]
Wastewater treatment was performed on factory wastewater having zinc concentration, copper concentration, and pH in the wastewater of 160 mg / L, 4.7 mg / L, and 3.4, respectively.
A 12% sodium hypochlorite aqueous solution was added to the factory effluent while stirring at 1000 mg / L and left at room temperature for 1 hour. Next, magnesium chloride was added to the waste water with stirring so that the magnesium concentration was 250 mg / L, and the mixture was allowed to stand at room temperature for 1 hour.
Thereafter, an aqueous sodium hydroxide solution was added to the waste water while stirring so that the pH was 11, and ultrapure water was added so that the volume of the waste water was 1.2 times. At this time, the zinc and copper concentrations in the wastewater were 133 mg / L and 3.9 mg / L, respectively.
Next, the pH-adjusted waste water was filtered through a nylon disc filter (manufactured by Membrane Solution) having a pore diameter of 0.45 μm, and the zinc and copper concentrations of the filtrate were measured.

[Example 2]
Except for adjusting the pH to 12, the zinc and copper concentrations of the filtrate were measured in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
The zinc and copper concentrations of the filtrate were measured in the same manner as in Example 1 except that magnesium chloride was added so that the magnesium concentration was 125 mg / L, and the pH was adjusted to 12. The results are shown in Table 1.

[Example 4]
The zinc and copper concentrations of the filtrate were measured in the same manner as in Example 1 except that sodium hypochlorite was added to 500 mg / L. The results are shown in Table 1.

[Example 5]
The zinc and copper concentrations of the filtrate were measured in the same manner as in Example 1 except that sodium hypochlorite was added to 500 mg / L and the pH was adjusted to 12. The results are shown in Table 1.

[Example 6]
Same as Example 1 except that sodium hypochlorite was added to 500 mg / L, magnesium chloride was added to a magnesium concentration of 125 mg / L, and the pH was adjusted to 12. Then, the concentration of zinc and copper in the filtrate was measured. The results are shown in Table 1.

[Comparative Examples 1-5]
As shown in Table 1, Examples were obtained except that sodium hypochlorite was added to a range of 0 to 2000 mg / L, magnesium chloride was not added, and pH was adjusted to 10. As in 1, the zinc and copper concentrations of the filtrate were measured. The results are shown in Table 1.

[Comparative Examples 6-9]
Examples except that sodium hypochlorite was not added, magnesium chloride was added so that the magnesium concentration was 500 mg / L, and the pH was adjusted to 10 to 13 as shown in Table 1. As in 1, the zinc and copper concentrations of the filtrate were measured. The results are shown in Table 1.

[Comparative Examples 10-14]
Example 1 except that sodium hypochlorite was not added, as shown in Table 1, magnesium chloride was added so that the magnesium concentration was 25 to 750 mg / L, and the pH was adjusted to 12. As in 1, the zinc and copper concentrations of the filtrate were measured. The results are shown in Table 1.

  The treated water zinc concentration and treated water copper concentration in Table 1 are the standards stipulated in the Japan Water Pollution Control Law and the Sewerage Law (hereinafter referred to as “Japan Standards”), the sewage comprehensive discharge standards of the People's Republic of China ( According to the first-class standard value (hereinafter referred to as “Chinese standard”) defined in GB 8978-1996), those satisfying the standard value were determined to be OK, and those not satisfying the standard value were determined to be NG. In addition, the overall judgment was OK when all of the reference values were satisfied, and NG when none of the reference values was satisfied.

In Examples 1 to 6 in which an oxidizing agent (in this example, sodium hypochlorite) and a coprecipitation agent (in this example, magnesium chloride) were allowed to act, both Japanese and Chinese standards were simultaneously applied to zinc and copper. I was satisfied. Furthermore, the removal rate of zinc and copper was generally 90% or more, indicating a high removal rate. In all the examples, the zinc removal rate was 98.7% by weight or more, and except for Example 5, the copper removal rate was 90.5% by weight or more. The copper removal rate in Example 5 was 88.5% by weight. The removal rate is [{(Zinc or copper concentration in factory effluent before filtration) − (Zinc or copper concentration in filtrate)} / Zinc or copper concentration in factory effluent before filtration)] × 100 (weight %).
In contrast, Comparative Example 1 in which no oxidizing agent was allowed to act and no coprecipitate was allowed to act was extremely low in copper removal rate of 10.3% by weight. And could not meet the Chinese standards.
In addition, Comparative Examples 2 to 5 in which the coprecipitation agent did not act satisfied the Japanese standard and the Chinese standard for copper by increasing the action amount of the oxidizing agent, but both the Japanese standard and the Chinese standard for zinc. I could not meet.
Moreover, although Comparative Examples 6-14 which did not make an oxidizing agent act also had the aspect which satisfy | filled the Japanese standard about zinc and copper simultaneously, it satisfies the Chinese standard about copper with a severer drainage standard. However, the removal rate of copper contained in industrial wastewater was extremely low, 23.1 wt% to 53.8 wt%.
Therefore, according to the present invention, it has been shown that zinc and copper, which are heavy metals, can be simultaneously and easily removed with high efficiency.

Claims (12)

Waste water treatment method for removing zinc and copper from waste water containing zinc and copper, including the following steps (i) and (ii):
(I) an insolubilization step in which an oxidizing agent and a coprecipitation agent that is magnesium and / or a salt thereof are allowed to act on the wastewater to insolubilize zinc and copper in the wastewater; and (ii) the step (i) A separation step of removing the insolubilized zinc and copper from the waste water attached to the membrane by membrane filtration .   The wastewater treatment method according to claim 1, wherein the insolubilization step includes a pH adjustment step. The wastewater treatment method according to claim 1 or 2 , wherein the wastewater contains a chelating agent. The wastewater treatment method according to any one of claims 1 to 3 , wherein the wastewater is plating wastewater. The waste water treatment method according to any one of claims 1 to 4 , wherein the oxidant is selected from the group consisting of chlorine oxides, chloric acids and salts thereof, and hydrogen peroxide. The wastewater treatment method according to any one of claims 1 to 5 , wherein in the insolubilization step, the pH of the wastewater is adjusted to be greater than 10 and 13 or less. The said insolubilization process WHEREIN: The action amount of the said oxidizing agent is 0.5 times or more and 20 times or less by molar equivalent ratio with respect to the copper concentration in the said waste_water | drain, It is any one of Claims 1-6. Wastewater treatment method. In the insolubilization step, the amount of action of the coprecipitation agent is 20 times or more and 1000 times or less in terms of molar equivalent ratio with respect to the zinc concentration in the wastewater, according to any one of claims 1 to 7 . Wastewater treatment method. The wastewater treatment method according to any one of claims 1 to 8 , wherein 95% by weight or more of zinc contained in the wastewater and 80% by weight or more of copper contained in the wastewater are simultaneously removed. Oxidation tank that acts with an oxidizing agent, coprecipitation tank that works with a coprecipitation agent that is magnesium and / or a salt thereof, an insolubilization tank that insolubilizes zinc and copper, and a separation that removes insolubilized zinc and copper by membrane filtration A waste water treatment apparatus for removing zinc and copper from waste water containing zinc and copper having an apparatus. Oxidation tank that acts with an oxidizing agent, coprecipitation tank that works with a coprecipitation agent that is magnesium and / or a salt thereof, an insolubilization tank that insolubilizes zinc and copper, and a separation that removes insolubilized zinc and copper by membrane filtration The waste water treatment apparatus according to claim 10 , wherein two or more tanks or apparatuses are integrated. The wastewater treatment apparatus according to claim 10 or 11 , further comprising pH adjusting means for adjusting pH in the tank by adding acid or alkali to an insolubilizing tank for insolubilizing zinc and copper.