JP7008456B2 - Treatment method and treatment equipment for the liquid to be treated - Google Patents

Description

The present invention relates to a method for treating a liquid to be treated and a treatment device.

Conventionally, as a method for treating wastewater containing heavy metals such as copper and silver, a hydroxide (alkaline agent) or a sulfide agent is added to precipitate the heavy metals in the form of hydroxides or sulfides, and the heavy metals are aggregated and solidified. A method of liquid separation is known. At that time, an iron salt such as an aqueous solution of iron chloride or an aluminum salt such as an aqueous solution of polyaluminum chloride is also added to enhance the cohesiveness and perform the treatment ([Background Art] of Patent Document 1).

In Patent Document 1, a sulfurizing agent such as sodium hydrosulfide is added to heavy metal-containing wastewater, and an oxidizing agent is added while controlling ORP while precipitating heavy metals to enhance sludge aggregation (Patent Document 1). [0014] [0025]).

In Patent Document 2, while recovering copper and the like from ore using sulfuric acid, in view of the fact that precious metals such as silver remain in the separated residue, silver is leached from the residue using sulfuric acid. After that, silver is recovered by adding copper sulfide or the like (Claim 1 of Patent Document 2).

Japanese Unexamined Patent Publication No. 2007-69068 U.S. Pat. No. 4,579,589

In the conventional method, an iron salt such as an aqueous solution of iron chloride or an aluminum salt such as an aqueous solution of polyaluminum chloride is added, so that a large amount of substances other than the metal (for example, silver) to be recovered are contained in the aggregate. .. In that case, the metal to be recovered cannot be efficiently recovered, and a large amount of residue is generated after the metal to be recovered is recovered, which increases the cost for processing the residue.

Since the technique described in Patent Document 1 uses an oxidizing agent or a polymer flocculant, a substance other than the metal to be recovered is contained in the agglomerate, which causes the same problems as the conventional method. Further, since the technique described in Patent Document 1 requires ORP control, the operation becomes very complicated. This is a particularly big problem in the actual operation of wastewater treatment.

In the technique described in Patent Document 2, silver is leached from the residue using sulfuric acid, and then when copper sulfide or the like is added, the precipitation reaction of silver sulfide under acidic conditions due to the use of sulfuric acid. Proceeds. Therefore, there is a possibility that hydrogen sulfide having an offensive odor and corrosiveness may be generated, which poses a problem in terms of work safety.

Further, in any of the above techniques, when the agglomerates (residues, precipitates) are solid-liquid separated by filtration using a filter (for example, microfilter membrane: MF membrane), the filter is likely to be clogged. Findings have been obtained by the present inventor. Due to clogging, it is necessary to replace the filter, and it is necessary to stop the wastewater treatment equipment every time it is replaced. That is, in any of the above techniques, there is room for improvement in terms of ease of maintenance of the processing device when performing filter filtration.

INDUSTRIAL APPLICABILITY The present invention secures work safety while avoiding cost increase and complicated operation in a method for treating a liquid to be treated such as wastewater containing various metals, and is a treatment device when performing filter filtration. The purpose is to ensure the ease of maintenance.

As a result of diligent studies to solve the above problems, the present inventors have added copper sulfide to the liquid to be treated under neutral to alkaline conditions, and then separate the precipitate of sulfide by solid-liquid separation. It has been found that the above-mentioned problems can be solved by adopting the method.

That is, one aspect of the present invention that solves the above problems is as follows.
The first aspect is
A method for treating a liquid to be treated containing a metal whose solubility product of the sulfide of the target metal is smaller than the solubility product of copper sulfide under neutral or alkaline conditions.
A copper sulfide addition step of adding copper sulfide to the liquid to be treated under neutral or alkaline conditions,
It is a method for treating a liquid to be treated, which comprises a solid-liquid separation step for separating a solid component containing a precipitate of sulfide of the metal and a liquid component in the liquid to be treated to which copper sulfide is added.

The second aspect is the first aspect.
The liquid to be treated is treated at pH 7-14.

The third aspect is the first or second aspect.
The solid-liquid separation step is carried out by passing the liquid to be treated through a cross-flow type or dead-end type filtration filter, and the maximum width of the opening of the filtration filter is 0.2 to 50 μm.

The fourth aspect is any one of the first to third aspects.
The cumulative 50% particle size on a volume basis measured by the laser diffraction type particle size distribution measuring device for copper sulfide is 20 to 35 μm.

The fifth aspect is any one of the first to fourth aspects.
The amount of copper sulfide dissolved in the copper sulfide is 5.8% by mass or less when 45 g of the copper sulfide is stirred in 1 Lg of water having a pH of 7 at 25 ° C. at 300 rpm for 24 hours.

The sixth aspect is any one of the first to fifth aspects.
In the copper sulfide addition step, 0.9 to 50 equivalents of copper sulfide is added to the metal in the liquid to be treated.

The seventh aspect is any one of the first to sixth aspects.
The metal is at least one selected from the group consisting of silver, mercury and gold.

The eighth aspect is any one of the first to seventh aspects.
The content of the metal in the liquid to be treated in the copper sulfide addition step is 10,000 ppm or less.

The ninth aspect is any one of the first to eighth aspects.
Prior to the copper sulfide addition step, there is further an alkaline substance addition step of adding an alkaline substance to the liquid to be treated to change the liquid to be treated to neutral or alkaline.

The tenth aspect is any one of the first to ninth aspects.
A slurry composed of a part of the liquid component and the solid component is obtained in the solid-liquid separation step, and at least a part of the slurry is returned to the liquid to be treated to which copper sulfide is added in the copper sulfide addition step. It also has a circulation step.

The eleventh aspect is any one of the first to tenth aspects.
In the copper sulfide addition step, copper sulfide is added in a plurality of times.

The twelfth aspect is any one of the first to eleventh aspects.
The metal is silver
The total content of silver, copper and sulfur in the solid component separated by the solid-liquid separation step is 95% by mass or more, and the silver content in the solid component is 30% by mass or more.

The thirteenth aspect is
A device that treats a liquid to be treated containing a metal having a solubility product of sulfide smaller than the solubility product of copper sulfide under neutral or alkaline conditions.
A copper sulfide supply mechanism that adds copper sulfide to the liquid to be treated under neutral or alkaline conditions,
A solid-liquid separation mechanism that separates a solid component containing a precipitate of sulfide of the metal and a liquid component in the liquid to be treated to which copper sulfide is added, and a solid-liquid separation mechanism.
It is a processing apparatus for a liquid to be treated.

The fourteenth aspect is the thirteenth aspect.
The solid-liquid separation mechanism includes a cross-flow type or dead-end type filtration filter, and the maximum width of the opening of the filtration filter is 0.2 to 50 μm.

The fifteenth aspect is the thirteenth or fourteenth aspect.
Further having an alkaline substance supply mechanism for adding an alkaline substance to the liquid to be treated,
The copper sulfide supply mechanism is configured to add copper sulfide to the liquid to be treated which has become neutral to alkaline by adding an alkaline substance by the alkaline substance supply mechanism.

The sixteenth aspect is any one of the thirteenth to fifteenth aspects.
The solid-liquid separation mechanism is configured so that a slurry composed of a part of the liquid component and the solid component can be obtained by the mechanism, and at least a part of the slurry is made of copper sulfide by the copper sulfide supply mechanism. It further has a slurry circulation mechanism for returning to the liquid to be added.

According to the present invention, a method for treating a liquid to be treated ensures work safety while avoiding cost increase and complicated operation, and also secures ease of maintenance of the treatment device when performing filter filtration. And a processing device for that purpose is provided.

FIG. 1 is a flowchart showing a treatment method of the liquid to be treated according to the present embodiment. FIG. 2 is a flowchart showing a method of treating the liquid to be treated according to the second embodiment.

An embodiment of the present invention will be described in the following order with reference to FIG. 1, which is a flowchart of the embodiment.
1. 1. Treatment method of liquid to be treated 1-1. Preparation process (dilution process, alkaline substance addition process)
1-2. Copper sulfide addition process 1-3. Solid-liquid separation process (metal recovery method)
1-4. Neutralization step 1-5. Evaporation concentration step 1-6. Condensed water treatment process 2. Effect of embodiment 3. Treatment device for the liquid to be treated 4. Others In addition, "-" in this specification means a predetermined value or more and a predetermined value or less.

<1. Treatment method of liquid to be treated>
(1-1. Preparation step (dilution step, alkaline substance addition step) ((1) in FIG. 1))
The liquid to be treated used in this embodiment is not particularly limited as long as it contains a predetermined metal, and may be a waste liquid. The predetermined metal is a metal in which the solubility product of sulfide is smaller than the solubility product of copper (II) sulfide (hereinafter, simply referred to as "copper sulfide"). The solubility product is at 25 ° C. In the present embodiment, copper sulfide is added to the liquid to be treated, and a metal having a smaller solubility product of sulfide is fixed as a precipitate of sulfide and separated from the liquid to be treated (solid-liquid separation). Hereinafter, the metal is also referred to as "target metal"). The fixed target metal can be recovered by a known method. Examples of target metals include silver, mercury and gold. In the present embodiment, it is preferable to use a liquid to be treated containing at least one of these.

The concentration of the target metal in the liquid to be treated (the total concentration when two or more kinds are contained) is not particularly limited, but is preferably 10,000 ppm or less, and more preferably 2 to 8,000 ppm from the viewpoint of economy. It is more preferably 5 to 6000 ppm. Further, in this step, if the concentration of the target metal in the liquid to be treated is too high, a dilution step of diluting the liquid to be treated so as to have a concentration of 10,000 ppm or less may be carried out.

Further, the liquid to be treated may be neutral or alkaline as long as it is neutral or alkaline when the copper sulfide addition step described later is performed, and an originally neutral or alkaline treatment liquid may be used, or initially acidic or medium. An alkaline substance addition step of adding an alkaline substance to the liquid to be treated to change the liquid to be treated to neutral or alkaline may be carried out to prepare a neutral to alkaline treatment liquid. .. The alkaline substance at that time is not particularly limited, and for example, ammonia, an alkali metal, or a hydroxide of an alkaline earth metal (caustic soda, etc.) may be used. After the start of the copper sulfide addition step described later, the liquid to be treated is treated under neutral or alkaline conditions.

In the present specification, "neutral to alkaline" means that the pH is 7 or more (preferably 7 to 14, more preferably 8 to 13) at a liquid temperature of 25 ° C. That is, "treatment under neutral or alkaline" means that the treatment is performed while maintaining the pH state of pH 7 or higher when measured at a liquid temperature of 25 ° C.

(1-2. Copper sulfide addition step ((2) in FIG. 1))
In this step, a neutral to alkaline treatment liquid is introduced into, for example, a reaction vessel, and copper sulfide is added thereto. By adding copper sulfide, the target metal in the liquid to be treated is precipitated and precipitated as sulfide (immobilization). The solid component containing the sulfide precipitate of the target metal (details thereof will be described later) is extremely unlikely to cause clogging when the filter is used in the solid-liquid separation step.

The cumulative 50% particle size ( _D50 ) on a volume basis measured by the laser diffraction type particle size distribution measuring device for copper sulfide is preferably 10 to 50 μm, preferably 20 to 35 μm from the viewpoint of reactivity with the target metal. It is more preferable to have.

Further, when 45 g of the copper sulfide is stirred in 1 L of water having a pH of 7 at 25 ° C. at 300 rpm for 24 hours, the dissolved amount is preferably 5.8% by mass or less (that is, 2.61 g or less). There are various commercially available copper sulfides, but when copper sulfide with such a small amount of dissolution is used, the target metal can be efficiently immobilized. From the viewpoint of efficiently immobilizing the target metal, the dissolved amount of the copper sulfide is preferably 3.0% by mass or less, more preferably 1.5% by mass or less (the dissolved amount is usually 0). 0.05% by mass or more). Examples of such copper sulfide include those manufactured by Nihon Kagaku Sangyo Co., Ltd.

The amount of copper sulfide added should be set so that the equivalent ratio (copper sulfide / target metal) of copper sulfide to the target metal in the liquid to be treated is 0.9 or more (particularly 1.0 or more). preferable. Here, regarding the "equivalent ratio", 1 equivalent refers to the amount of copper sulfide required to make the target metal into a sulfide, and the equivalent ratio (copper sulfide / target metal) of 1.0 is theoretically the target metal. It is shown that an amount of copper sulfide that can be completely converted to sulfide is added. From the viewpoint of economy, it is preferable to set the equivalent ratio (copper sulfide / target metal) of copper sulfide to the target metal in the liquid to be treated to be 50 or less. The equivalent ratio (copper sulfide / metal) is more preferably 1.0 to 24.0, and particularly preferably 1.0 to 12.0. By setting the amount of copper sulfide added within the above range, the target metal can be immobilized extremely well, and the cost of copper sulfide can be suppressed.

Although this embodiment may be performed in a batch system or a continuous system, the amount of copper sulfide added in the continuous system is the average value of the concentration of the target metal in the liquid to be treated for a certain period. It is good to ask for it and determine it based on it.

Further, the addition of copper sulfide may be performed in a plurality of times (twice or more). When this method is adopted, the addition may be performed intermittently, and the addition amount at that time may be larger or smaller than the first addition amount.

In the copper sulfide addition step, it is preferable to stir the liquid to be treated to which copper sulfide has been added in order to increase the efficiency of fixing the target metal as a sulfide.

Further, the reaction time of the reaction in which the target metal in the liquid to be treated is fixed as sulfide (in the case of a continuous type, the residence time of the liquid to be treated in the reaction tank) is not particularly limited, and the slurry described later is not particularly limited. It may vary depending on the embodiment of the treatment method, such as when the circulation step is carried out or not.

(1-3. Solid-liquid separation step (metal recovery method) ((3) in FIG. 1))
In this step, the solid component containing the precipitate of the sulfide of the target metal generated by the copper sulfide addition step and the liquid component are solid-liquid separated. It is not necessary to completely separate the solid component and the liquid component, and a part of the liquid component may be contained in the solid component to form a slurry (in this way, the slurry circulation step described later can be easily carried out, and the actual operation can be performed. It is advantageous). The solid component contains the sulfide of the target metal, and in some cases, contains copper sulfide and other impurities that remain unreacted. From the viewpoint of separation efficiency, solid-liquid separation is preferably performed by filtration, and the specific method and device configuration for filtering are not particularly limited, but for example, a method using a cross-flow type or dead-end type filtration filter. May be adopted. Solid-liquid separation is carried out by passing the liquid to be treated through this. The dead-end type is a so-called total amount filtration method, which is a method in which the total amount of the liquid to be treated is filtered through a filter, and in principle, the solid component and the liquid component are completely separated. On the other hand, the cross-flow type is a method in which a filter is provided around the flow of the liquid to be treated, and a solid component is obtained as a slurry together with a part of the liquid component. Compared to the dead-end type, there is also the feature that solid components do not accumulate excessively on the filter.

The maximum width of the opening of the filter used for the filtration is preferably 0.2 to 50 μm, more preferably 0.2 to 30 μm. If a filter with a mesh opening under this condition is adopted, clogging of the filter is less likely to occur while reliably collecting solid components. The opening in the present embodiment refers to the gap between the lines of the fibers constituting the filter or the maximum width of the gap.

As shown in FIG. 1, it is preferable to carry out a circulation step of returning a part or all of the solid component after the solid-liquid separation step to the target liquid to be subjected to the copper sulfide addition step. From the viewpoint of ease of transfer of the solid component, it is preferable to return it as a slurry dispersed in a part of the liquid component separated in the solid-liquid separation step (slurry circulation step). At that time, a copper sulfide re-addition step of newly adding copper sulfide (to fix the target metal existing in the returned slurry) may be carried out. The concentration of the target metal in the liquid to be treated usually fluctuates with time, but the fluctuation can be dealt with by carrying out the (slurry) circulation step, and the amount corresponding to the maximum value of the target metal concentration can be adjusted. By adding a small amount (for example, an amount corresponding to the average value of the concentration of the target metal), the target metal can be immobilized at a sufficient ratio (the recovery rate of the target metal can be increased).

As described above, the solid component separated in this step is mainly composed of the sulfide of the target metal, and it is preferable to recover the solid component, separate the target metal from the solid component, and finally recover the target metal. .. As the specific method, a known method may be used. From the above, the series of steps including the copper sulfide addition step and the solid-liquid separation step can be regarded as a "method for recovering the target metal".

Further, since most of the substances constituting the solid component after solid-liquid separation are the sulfide of the target metal and copper sulfide, the solid component is suitable as a raw material for recycling, and the solid component is used as described above. If only copper sulfide can be removed, the target metal can be easily recovered. That is, the present embodiment has technical significance as a "method for producing a metal raw material" capable of easily recovering the target metal later.
Further, the liquid component separated in the solid-liquid separation step described above is further treated through known steps such as a neutralization step, an evaporation concentration step, and a condensed water treatment step.

(1-4. Neutralization step ((4) in FIG. 1))
In the neutralization step, an acid is added to the liquid component (filter solution) generated in the solid-liquid separation step to neutralize. The acid added here may be any known acid, and for example, sulfuric acid may be used. By changing ammonia to ammonium sulfate (ammonium sulfate) (when ammonia is used as alkali), the content of ammonia, which is a wastewater control substance, in the condensed water to be treated in the following condensed water treatment step. Can be significantly reduced.

(1-5. Evaporation concentration step ((5) in FIG. 1))
In this step, the liquid component (filter solution) neutralized in the neutralization step is evaporated and concentrated. The concentrate remaining after evaporation and concentration may be treated by a known method depending on the substance, and may be treated as industrial waste, for example.

(1-6. Condensed water treatment step ((6) in FIG. 1))
In this step, the condensed water obtained in the obtained evaporation concentration step is appropriately treated. As a treatment method, a known method may be used depending on the substance contained in the condensed water. Examples of the above-mentioned method include aerobic treatment, anaerobic treatment, and RO membrane treatment.

<2. Effect of embodiment>
In the present embodiment, the following effects are obtained by going through each of the above steps.

Unlike the conventional method, it is not necessary to add a flocculant such as an iron salt such as an aqueous iron chloride solution or an aluminum salt such as an aqueous solution of polyaluminum chloride, so that the target metal can be efficiently recovered and the target metal can be recovered. It is possible to suppress the generation of a large amount of residue after recovery of aluminum chloride, and it is possible to suppress an increase in residue treatment cost.

Unlike the technique described in Patent Document 1, it is not necessary to use an oxidizing agent or a polymer flocculant, and it is possible to suppress the generation of a large amount of residue after recovering the target metal, resulting in an increase in residue treatment cost. Can be suppressed. In addition, it is not necessary to perform ORP control, and complicated operations can be avoided.

Unlike the technique described in Patent Document 2, in the present embodiment, the liquid to be treated containing the target metal is treated under neutral or alkaline conditions, so that there is no possibility of generating offensive odor and corrosive hydrogen sulfide. It becomes possible to ensure the safety of work.

Further, when the solid component containing the precipitate of the sulfide of the target metal precipitated after the copper sulfide addition step is solid-liquid separated by using the filter, the filter is less likely to be clogged. As a result, ease of maintenance can be ensured.

In this embodiment, in the treatment of the liquid to be treated containing the target metal, while avoiding an increase in cost and complicated operations, the safety of work is ensured, and the ease of maintenance is also ensured when performing filter filtration. can.

<3. Processing device for liquid to be treated>
The following configuration reflects the technical idea of the above-mentioned method for treating the liquid to be treated in the apparatus. It should be noted that even in the processing apparatus having the following configuration, the effect of the embodiment of the above processing method is obtained.
"A device that treats a liquid to be treated containing a metal whose solubility product of sulfide is smaller than the solubility product of copper sulfide under neutral or alkaline conditions.
A copper sulfide supply mechanism that adds copper sulfide to a neutral or alkaline treatment liquid,
A solid-liquid separation mechanism that separates a solid component containing a precipitate of sulfide of the metal and a liquid component in the liquid to be treated to which copper sulfide is added, and a solid-liquid separation mechanism.
A device for treating a liquid to be treated. 』\

Since the device is treated under neutral or alkaline conditions, each of the above mechanisms (particularly the portion in contact with the liquid to be treated) constituting the device for treating the liquid to be treated in the present embodiment is formed of a material having alkali resistance. It is preferable to have it. The preferred example of the device for treating the liquid to be treated is the same as the content and reason described in the method for treating the liquid to be treated, and some of them will be omitted.

As one embodiment of the treatment apparatus, the liquid to be treated is introduced into the reaction tank via a transfer means such as a pipe, where copper sulfide is added by the copper sulfide supply mechanism to fix the target metal. From the viewpoint of the treatment efficiency of the target metal, it is preferable that the transfer means is configured so that the liquid to be treated can be continuously introduced into the reaction vessel.

The copper sulfide supply mechanism has a known configuration as long as copper sulfide can be added to a reaction vessel in which a neutral or alkaline treatment liquid is present (for example, a container for storing copper sulfide and a pipe for transferring the container (for example). The number of pipes may be one or multiple))). Further, from the viewpoint of the efficiency of fixing the target metal, it is preferable to provide a stirring mechanism in the reaction vessel in which the neutral or alkaline treatment liquid is present.

At least a part of the target metal in the liquid to be treated is fixed as sulfide in the reaction vessel. This liquid to be treated is taken out from the reaction tank and transferred to the next solid-liquid separation mechanism by a transfer means such as a pipe. The treatment apparatus may be configured to perform fixing as a sulfide in a batch manner and extract all the liquid to be treated from the reaction vessel, or the fixing may be carried out in a continuous manner to continuously treat. It may be configured to drain the liquid.

The solid-liquid separation mechanism has a known configuration (for example, cross-flow type or dead-end type filtration) as long as the solid component containing the sulfide of the target metal precipitated by the addition of the copper sulfide can be separated from the liquid component. It may be a filtration device equipped with a filter). If a simple solid-liquid separation means such as a filtration device is adopted, the volume of the solid-liquid separation mechanism can be reduced, and eventually the volume of the entire device can be reduced. At that time, from the viewpoint of reliably collecting solid components and making it difficult for the filter to be clogged, the maximum width of the opening of the filter used for the filtration is preferably 0.2 to 50 μm.

In addition, the device to be treated of the present embodiment is an alkaline substance that adds an alkaline substance to a reaction vessel in which an acidic or neutral liquid to be treated exists, or to a liquid to be treated that has been transferred to the reaction vessel. Further may have a supply mechanism (eg, a container for storing alkaline substances and a pipe for transferring them). In this case, copper sulfide is added by the copper sulfide supply mechanism to the liquid to be treated which has become neutral to alkaline by adding the alkaline substance by the alkaline substance supply mechanism.

Further, the solid-liquid separation mechanism is configured so that a slurry composed of a part of the liquid component and the solid component can be obtained by the solid-liquid separation mechanism, and at least a part of the slurry is supplied to the copper sulfide. Slurry circulation mechanism to return to the liquid to be treated to which copper sulfide is added by the mechanism (for example, a slurry composed of a part of the liquid component and the solid component is placed in a reaction tank in which the liquid to be treated to which copper sulfide is added exists. It is preferable to have more pipes to transfer). An example of the solid-liquid separation mechanism configured as described above is a filtration device provided with a cross-flow type filtration filter.

<4. Others>
The technical scope of the present invention is not limited to the above-described embodiment, and includes various modifications and improvements within the range in which a specific effect obtained by the configuration of the invention or a combination thereof can be derived. .. For example, the combination of each of the above modifications and the combination with the contents exemplified in the above embodiment is also the scope of application of the technical idea of the present invention.

For example, he stated that the above-mentioned method for treating the liquid to be treated (the solid-liquid separation step in the above) has technical significance as a "method for producing a metal raw material" capable of easily recovering the target metal later. When this metal raw material is defined as a thing, it becomes as follows, and it has an effect that the target metal can be easily recovered.
"It is a solid target metal-containing material, and the total content of the target metal, copper, and sulfur in the target metal-containing material is 95% by mass or more, and the content of the target metal in the target metal-containing material is 30% by mass. % Or more of the target metal-containing material. 』\
Of the target metals, silver is widely used in industry due to its excellent conductivity and oxidation resistance, and there are many waste liquids containing it. It is preferable to carry out the treatment method of the present invention using such a waste liquid as a liquid to be treated to obtain the target metal (silver) -containing material, and recover silver from the target metal (silver)-containing material.

Further, the fact that the metal-containing material is suitable as a raw material for recycling is also an advantageous effect of the method for treating the liquid to be treated according to the embodiment of the present invention.

Further, although the focus has been on recovering the target metal from the liquid to be treated up to this point, for example, attention may be paid to removing the target metal from the liquid to be treated. For example, when the target metal is inorganic mercury (Hg (II)), a copper sulfide addition step is carried out to cause a precipitate of mercury sulfide, and by removing this precipitate, the inorganic mercury (Hg) is removed from the liquid to be treated. (II)) can be removed. In this case, the "method for treating the liquid to be treated" is, in other words, the "method for removing the target metal from the liquid to be treated".

Next, an example will be shown and the present invention will be specifically described. In the following examples, silver is mainly targeted for recovery. The present invention is not limited to the following examples.

<Example 1>
A copper sulfide slurry was prepared by dispersing 3 g of copper (II) sulfide manufactured by Nihon Kagaku Sangyo in 7 mL of pure water. The copper sulfide slurry was dispersed by ultrasonic waves at 29 ° C. for 2 minutes. The dispersed slurry was stirred with a magnetic stirrer at 700 rpm to prevent sedimentation. The average particle size of the copper sulfide used was measured with MT3300EX II manufactured by Microtrac Bell, and the specific surface area was measured with HM model-1210 manufactured by Mountech. As a result, the volume average particle size (cumulative 50% particle size based on the volume) of copper sulfide in this example was 25 μm, and the specific surface area by the BET method was 1.3 m ² / g. Table 1 summarizes this.

As the liquid to be treated (hereinafter, also referred to as raw water), the liquid having the composition shown in Table 2 below was used.

The mass ratio of copper sulfide and silver to 0.5 L of raw water (referred to as CuS / Ag ratio) is 0.5 (the equivalent ratio of CuS to Ag (CuS / Ag) is about 1.13), 1, 2 Alternatively, a copper sulfide slurry was added so as to be 3. These solutions were stirred with a magnetic stirrer at 500 rpm for 30 minutes. After stirring, cross-flow type filtration was performed with a filter having an opening of 0.45 μm (MF membrane: microfilter; the same applies hereinafter). As a filter, Asahi Kasei Microza MF (hole diameter 0.45 μm) was used. The pressure at the inlet of the filter was adjusted to 0.1 MPa or less, and the outlet pressure was adjusted to 0.01 MPa.

In order to investigate whether silver is fixed by copper sulfide, the concentration of silver contained in the permeate of the microfilter was analyzed. We also analyzed the copper concentration to investigate that silver is sulfurized while copper sulfide is ionized. An inductively coupled plasma atomic emission spectrometer (ICP-AES; HITACHI SPS-5100) was used to analyze the concentrations of silver and copper contained in the permeate.

As a result, the silver concentration in the raw water was 23.3 mg / L, whereas when copper sulfide was added so that the CuS / Ag ratio was 0.5, the silver concentration in the permeate was 9.9 mg / L. , The silver concentration was greatly reduced. This indicates that silver was fixed by copper sulfide.

Further, while the copper concentration in raw water was 38 mg / L, when copper sulfide was added so that the CuS / Ag ratio was 0.5, the copper concentration in the permeate was 45 mg / L, and the copper concentration increased. Was. It is presumed that this is because the copper of copper sulfide is ionized (and transferred to the permeate) while the silver is sulfurized.

When copper sulfide was added so that the CuS / Ag ratio was 1, the silver concentration in the permeate was 0.2 mg / L, and the silver concentration was further significantly reduced. Further, the copper concentration was 46 mg / L, and the copper concentration increased as in the case where the CuS / Ag ratio was 0.5. Similar results were obtained when copper sulfide was added so that the CuS / Ag ratio was 2 or 3. Table 3 summarizes these results.

It was confirmed that silver in the raw water was removed by 99% or more when the mass ratio (CuS / Ag ratio) of copper sulfide to silver was 1 or more. It was also confirmed that the elution copper concentration (difference between the copper concentration of the permeate and the raw water) was in harmony with the case where the exchange reaction between copper sulfide and silver occurred.

Moreover, as a result of calculating the adsorption capacity of silver per unit mass of copper sulfide, it was 1.03 mg (Ag) / mg (CuS).

溶解量０．５質量％の硫化銅（日本化学産業製）の方が、少ない使用量で高い銀除去率を達成できることがわかる。以降の実施例では、この硫化銅を使用した。 When 45 g of copper sulfide used in the above test was stirred in 1 L of water at pH 7 at room temperature (25 ° C.) at 300 rpm for 24 hours, the dissolved amount was 0.5% by mass (0.225 g). On the other hand, using copper sulfide having a dissolution amount of 10.6% by mass obtained under the same conditions, a silver removal test from raw water was carried out in the same manner as above. At this time, the tests were conducted in five ways with CuS / Ag ratios of 1.3, 1.6, 2.1, 2.5 and 2.9. The results (removal rate of silver from raw water) are shown in Table 4 below together with the above test results.

It can be seen that copper sulfide (manufactured by Nihon Kagaku Sangyo Co., Ltd.) with a dissolved amount of 0.5% by mass can achieve a high silver removal rate with a small amount of use. In subsequent examples, this copper sulfide was used.

<Example 2>
Example 2 was tested based on the flowchart shown in FIG.

A copper sulfide slurry was prepared by dispersing 1.56 g of copper sulfide (II) manufactured by Nihon Kagaku Sangyo in 100 mL of pure water. The copper sulfide slurry was dispersed by ultrasonic waves at 29 ° C. for 5 minutes. The dispersed slurry was stirred with a magnetic stirrer at 400 rpm to prevent sedimentation. Items not otherwise specified are as described in Example 1.

As the liquid to be treated (raw water), the one having the composition shown in Table 5 below was used. The raw water used in Example 2 differs only in the concentration of silver and copper from the raw water used in Example 1.

Then, a copper sulfide slurry (total amount of copper sulfide 1.56 g) was supplied to a 13 L reaction tank equipped with two-stage turbine blades. Next, raw water was continuously supplied to the apparatus at 0.4 L / min. The hydraulic residence time of raw water in the apparatus is about 30 minutes (= 13 L / (0.4 L / min)). The total amount of raw water provided was 21.6 L. At this time, the amount of silver was 663 mg and the CuS / Ag ratio was 2.4. The rotation speed of the reaction tank stirrer was set to 480 rpm and the stirring intensity was set to 1.3 W / L.

The reaction solution was withdrawn from the reaction tank so that the flow rate of the pipe was 1 m / sec or more, and the reaction solution was subjected to the same microfilter as in Example 1 under the same pressure conditions. In the microfilter unit, the permeate is extracted at 0.4 L / min, while the filtered slurry (suspended solid containing silver sulfide precipitate + circulating fluid) is all concentrated slurry as shown in FIG. It was returned to the reaction tank.

The permeate of the microfilter obtained 30 minutes after the start of the supply of raw water was collected, and the concentrations of silver and copper in the permeate were measured. If the silver concentration of this permeate is small, it can be determined that the silver in the raw water is well fixed by copper sulfide. ICP-AES was used for the analysis of the silver and copper concentrations contained in the permeate.

As a result of the above test conducted with a hydraulic residence time of 30 minutes, the silver removal rate was 99% or more. The same experiment was performed separately by setting the raw water supply flow rate to 0.8 L / min (hydraulic residence time 15 minutes) and 2.4 L / min (hydraulic residence time 5 minutes). In addition, the removal rate of silver was 99% or more. That is, it was confirmed that if the hydraulic residence time is set to 5 minutes, silver can be effectively removed and continuous operation is possible. Table 6 below summarizes the silver concentration, the copper concentration, and the silver removal rate in the above-mentioned permeate at the time when each water flow amount is reached when the hydraulic residence time is 5 minutes.

残渣（懸濁物質）における銀の含有量は７０質量％、銅の含有量は２０質量％、硫黄の含有量は１０質量％であった。つまり、本実施例で得られた懸濁物質には、銀が非常に高濃度で濃縮されており、しかもこの銀とそれの固定に用いた硫化銅由来の元素だけで実質的に懸濁物質が構成されており、これは銀のリサイクル原料として十分に価値があることが確認できた。 In the above test conducted with a hydraulic residence time of 30 minutes, a part of the liquid to be treated in the reaction vessel was withdrawn 30 minutes after the supply of raw water was started, and the liquid to be treated was filtered under pressure. By doing so, it was separated into suspended solids and liquid components. In this pressure filtration, the filtration pressure was adjusted to 0.2 MPa, and 5C filter paper (ADVANTEC) was used. The residue (suspended solids) on the filter paper was dried at 70 ° C. for 6 hours, and then pressure-decomposed with concentrated nitrate and concentrated sulfuric acid mixed at a volume ratio of 3: 1 to determine the concentration of silver and copper contained in the decomposition solution. It was measured by ICP-AES and the sulfur concentration was measured by XRD. Table 7 shows the results.

The silver content in the residue (suspended solids) was 70% by mass, the copper content was 20% by mass, and the sulfur content was 10% by mass. That is, in the suspension substance obtained in this example, silver is concentrated at a very high concentration, and moreover, only the silver and the element derived from copper sulfide used for fixing the silver are substantially suspended substances. It was confirmed that this is sufficiently valuable as a raw material for recycling silver.

<Example 3>
The test was carried out in the same manner as in Example 2 except that the supply amount of the copper sulfide slurry was changed so that the CuS / Ag ratio was 48/108 (equivalent ratio 1/1) (hydraulic residence time was 30). Minutes). The permeate of the microfilter obtained 30 minutes after the start of the supply of raw water was collected, the silver concentration in the permeate was measured, and the removal rate of silver from the raw water was determined. As a result, the silver concentration in the permeate was 0.1 mg / L, and the removal rate of silver from the raw water was 99% or more.

<Example 4>
A copper sulfide slurry was prepared by dispersing 1 g of copper (II) sulfide manufactured by Nihon Kagaku Sangyo in 10 mL of pure water. The copper sulfide slurry was dispersed by ultrasonic waves at 29 ° C. for 5 minutes. The dispersed slurry was stirred with a magnetic stirrer at 400 rpm to prevent sedimentation.

The raw water was prepared by adding a standard solution for 1000 ppm atomic absorption of gold (manufactured by Kanto Chemical Co., Inc.) to a solution having the same composition as that of Example 1. The concentration of gold in the obtained gold-containing raw water was 5 ppm. Items not otherwise specified are as described in Example 1. For example, the gold recovery test in Example 4 was performed by a batch test.

表８に示すように、硫化銅濃度が１００、２００ｐｐｍ（すなわち１００ｐｐｍ以上）のときには、透過液における金の濃度は４．８ｐｐｍから３．１～３．３ｐｐｍへと減少しており、すなわち原水中の金の３０％程度が硫化物の沈殿として回収可能であることがわかった。 A predetermined amount of the above copper sulfide slurry was added to 200 mL of gold-containing raw water prepared in advance as described above. Copper sulfide slurries were added so that the copper sulfide concentrations as solids in the gold-containing raw water were 50, 100, and 200 ppm, respectively, and each gold-containing raw water was prepared. The gold-containing raw water to which the copper sulfide slurry was added was stirred at room temperature for 45 minutes. Then, the permeate of the microfilter was collected in the same manner as in Example 1, and the gold concentration was analyzed. The results are shown in Table 8.

As shown in Table 8, when the copper sulfide concentration is 100, 200 ppm (that is, 100 ppm or more), the gold concentration in the permeate decreases from 4.8 ppm to 3.1 to 3.3 ppm, that is, in raw water. It was found that about 30% of the gold in gold can be recovered as a precipitate of sulfide.

<Example 5>
A copper sulfide slurry was prepared by dispersing 2.5 g of copper sulfide (II) manufactured by Nihon Kagaku Sangyo in 50 mL of pure water. The copper sulfide slurry was dispersed by ultrasonic waves at 29 ° C. for 5 minutes. The dispersed slurry was stirred with a magnetic stirrer at 400 rpm to prevent sedimentation.

As raw water, 1000 ppm of inorganic mercury (Hg (II)) atomic absorption standard solution (manufactured by Kanto Chemical Co., Inc.) was added to a solution having the same composition as in Example 1 diluted 50-fold with pure water. Prepared. The concentration of mercury in the obtained mercury-containing raw water was 7.5 ppm. Items not otherwise specified are as described in Example 1.

原水中の水銀は、硫化銅の添加により０．００５ｐｐｍ未満へと減少させられることを確認した。つまり本発明は、原水からの水銀の除去にも適用可能であることがわかった。 The above copper sulfide slurry was added to 250 mL of mercury-containing raw water prepared in advance as described above. Each mercury-containing raw water was prepared by adding the above-mentioned slurry so that the copper sulfide concentration as a solid content in the mercury-containing raw water to which the slurry was added was 100 and 200 ppm, respectively. The mercury-containing raw water to which the copper sulfide slurry was added was stirred at room temperature for 45 minutes. Then, the mercury-containing raw water was filtered through a syringe filter having a pore size of 0.45 μm. The filtrate was diluted 10-fold with 5% nitric acid (manufactured by Kanto Chemical Co., Inc.) and used for measuring the amount of mercury. The Mercury MA-2000 mercury analyzer manufactured by Nippon Instruments was used as the analyzer. The results are shown in Table 9.

It was confirmed that mercury in raw water was reduced to less than 0.005 ppm by the addition of copper sulfide. That is, it was found that the present invention can also be applied to the removal of mercury from raw water.

<Example 6>
As the copper sulfide slurry, the same raw water as in Example 1 was used, and as the raw water, raw water having the same composition as in Example 1 was used except that the silver concentration was 44 ppm. Nitric acid (for measuring harmful metals manufactured by Kanto Chemical Co., Inc.) or sodium hydroxide was added to the raw water to adjust the pH. The adjusted pH was set to 7, 11 and 13, respectively.

The above copper sulfide slurry was added to 500 mL of raw water whose pH was adjusted in advance. The copper sulfide concentration as a solid content was set so that the CuS / Ag ratio was 2, and the copper sulfide slurry was added. The solution was stirred at room temperature for 30 minutes using a magnetic stirrer. After stirring, the mixture was filtered through a syringe filter having a pore size of 0.45 μm, and the filtrate was used for measuring the silver concentration. Items not otherwise specified are as described in Example 1. For example, the test in Example 6 was performed by a batch test. The above results are shown in Table 10 below. It was confirmed that silver was recovered in raw water at any pH.

<Comparative Example 1>
A zinc sulfide (II) slurry was prepared using zinc sulfide (II) instead of copper (II) sulfide. 2.0 g of zinc sulfide (II) manufactured by Wako Pure Chemical Industries, Ltd. was dispersed in 10 mL of pure water to prepare a zinc sulfide slurry. The zinc sulfide slurry was dispersed by ultrasonic waves at 29 ° C. for 5 minutes. The dispersed slurry was stirred with a magnetic stirrer at 400 rpm to prevent sedimentation.

As the raw water, water having the same composition as that of Example 1 except that the silver concentration was 1020 ppm was used. Items not otherwise specified are as described in Example 1.

硫化亜鉛の添加によっては原水から銀が除去できないことがわかった。

1.8 mL of the zinc sulfide slurry was added to 300 mL of the raw water, and the mixture was stirred for 30 minutes. The concentration of zinc sulfide as a solid content in the mixture was 1080 ppm. The raw water after stirring was filtered through a syringe filter having a pore size of 0.45 μm. The silver concentration in the filtrate was measured. The silver concentration in the filtrate was 987 ppm. The above results are summarized in Table 11 below.

It was found that silver could not be removed from the raw water by adding zinc sulfide.

Claims (11)

A method for treating a liquid to be treated containing a metal having a solubility product of sulfide smaller than the solubility product of copper sulfide under neutral or alkaline conditions.
A copper sulfide addition step of adding copper sulfide to the neutral to alkaline treatment liquid, and
A solid-liquid separation step for separating a solid component and a liquid component containing a precipitate of the sulfide of the metal in the liquid to be treated to which copper sulfide is added, and a solid-liquid separation step.
Have,
The solid-liquid separation step is carried out by passing the liquid to be treated through a cross-flow type filtration filter, and the maximum width of the opening of the filtration filter is 0.2 to 50 μm.
The cumulative 50% particle size based on the volume measured by the laser diffraction type particle size distribution measuring device for copper sulfide is 20 to 35 μm.
In the copper sulfide addition step, 0.9 to 50 equivalents of copper sulfide was added to the metal in the liquid to be treated.
A slurry composed of a part of the liquid component and the solid component is obtained in the solid-liquid separation step, and at least a part of the slurry is returned to the liquid to be treated to which copper sulfide is added in the copper sulfide addition step. A method for treating a liquid to be treated , further comprising a circulation step . The method for treating a liquid to be treated according to claim 1, wherein the liquid to be treated is treated at pH 7 to 14. The method for treating a liquid to be treated according to claim 1 or 2, which is carried out continuously. The copper sulfide has a dissolved amount of 5.8% by mass or less when 45 g of the copper sulfide is stirred in 1 L of water having a pH of 7 at 25 ° C. at 300 rpm for 24 hours . 3. The method for treating a liquid to be treated according to any one of 3. The method for treating a liquid to be treated according to any one of claims 1 to 4 , wherein the metal is at least one selected from the group consisting of silver, mercury and gold. The method for treating a liquid to be treated according to any one of claims 1 to 5 , wherein the content of the metal in the liquid to be treated to be subjected to the copper sulfide addition step is 10,000 ppm or less. Any of claims 1 to 6 , further comprising an alkaline substance addition step of adding an alkaline substance to the liquid to be treated to change the liquid to be treated to neutral or alkaline before the copper sulfide addition step. The method for treating the liquid to be treated according to. The method for treating a liquid to be treated according to any one of claims 1 to 7 , wherein copper sulfide is added in a plurality of times in the copper sulfide addition step. The metal is silver
Claimed that the total content of silver, copper and sulfur in the solid component separated by the solid-liquid separation step is 95% by mass or more, and the silver content in the solid component is 30% by mass or more. Item 8. The method for treating a liquid to be treated according to any one of Items 1 to 8 . A device that treats a liquid to be treated containing a metal having a solubility product of sulfide smaller than the solubility product of copper sulfide under neutral or alkaline conditions.
A copper sulfide supply mechanism that adds copper sulfide to a neutral or alkaline treatment liquid,
A solid-liquid separation mechanism that separates a solid component containing a precipitate of sulfide of the metal and a liquid component in the liquid to be treated to which copper sulfide is added, and a solid-liquid separation mechanism.
Have,
The solid-liquid separation mechanism is provided with a cross-flow type filtration filter, and the maximum width of the opening of the filtration filter is 0.2 to 50 μm.
The solid-liquid separation mechanism is configured so that a slurry composed of a part of the liquid component and the solid component can be obtained by the mechanism, and at least a part of the slurry is made of copper sulfide by the copper sulfide supply mechanism. A device for processing a liquid to be treated, which further has a slurry circulation mechanism for returning to the liquid to be treated. Further having an alkaline substance supply mechanism for adding an alkaline substance to the liquid to be treated,
The tenth aspect of the present invention is configured such that copper sulfide is added by the copper sulfide supply mechanism to a liquid to be treated which has become neutral to alkaline by adding an alkaline substance by the alkaline substance supply mechanism. The above-mentioned device for treating a liquid to be treated.

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