JP2019063710A - Treatment method and treatment apparatus of liquid to be treated - Google Patents

Abstract

To ensure safety of work while avoiding cost increase and complicated operation, and also ensure ease of maintenance of a treatment apparatus when filter filtration is performed.SOLUTION: A method for treating a liquid to be treated containing a metal whose sulfide has a solubility product smaller than a copper sulfide in neutrality or alkalinity has: a copper sulfide addition step of adding the copper sulfide to the liquid to be treated in neutrality or alkalinity; and a solid-liquid separation step of separating a solid component including precipitation of the sulfide of the metal and a liquid component in the liquid to be treated to which the copper sulfide is added.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, as a method of treating waste water containing heavy metals such as copper and silver, a heavy metal is precipitated in the form of hydroxide or sulfide by adding a hydroxide agent (alkaline agent) or a sulfiding agent and coagulated to solidify it. Methods of liquid separation are 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 cohesion and carry out treatment ([Background Art] of Patent Document 1).

  In Patent Document 1, a sulfiding agent such as sodium hydrogen sulfide is added to a heavy metal-containing wastewater to precipitate heavy metals, and an oxidizing agent is added while ORP control is performed to enhance the flocculating property of sludge (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 a noble metal such as silver remains in the separated residue, sulfuric acid is used to leach silver from the residue. Then, copper sulfide or the like is added to recover silver (claim 1 of Patent Document 2).

JP 2007-69068 A U.S. Pat. No. 4,579,589

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

  In the technique described in Patent Document 1, since an oxidant and a polymer flocculant are used, a substance other than the metal to be recovered is contained in the aggregate, and the same problem as the conventional method occurs. Moreover, in the technique described in Patent Document 1, since ORP control is required, the operation becomes very complicated. This is a particularly serious 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 adding copper sulfide and the like, precipitation reaction of silver sulfide under acidity because of the use of sulfuric acid. Go forward. Therefore, there is a possibility that hydrogen sulfide having an offensive odor and corrosiveness may be generated, and there is a problem with the safety of operation.

  Furthermore, in any of the above-mentioned techniques, when the solid matter is separated by filtration using a filter (for example, micro filter membrane: MF membrane), aggregates (residues, precipitates) are easily clogged. Findings have been obtained by the inventor. It is necessary to replace the filter because of clogging, and it is necessary to shut down the waste water treatment equipment after each replacement. That is, in any of the above-described techniques, there is room for improvement in terms of the ease of maintenance of the processing apparatus when filter filtration is performed.

  The present invention is a method of treating a liquid to be treated such as wastewater containing various metals, in which the safety of the operation is secured while avoiding the cost increase and the complicated operation, and the treatment apparatus for carrying out the filter filtration. The purpose is to ensure the ease of maintenance of the

  As a result of intensive studies to solve the above problems, the present inventors say that after adding copper sulfide to a liquid to be treated under neutral to alkaline conditions, precipitation of sulfide is separated by solid-liquid separation. It has been found that adopting the method can solve the above-mentioned problems.

That is, one aspect of the present invention which solves the above-mentioned subject is the following.
The first aspect is
A method of treating a liquid to be treated containing a metal whose solubility product of the target metal sulfide is smaller than the solubility product of copper sulfide under neutral to alkaline conditions,
A copper sulfide addition step of adding copper sulfide to the to-be-treated liquid under neutral to alkaline conditions;
It is a processing method of the processed fluid which has a solid-liquid separation process which separates a solid ingredient and a liquid ingredient containing precipitation of a sulfide of the metal in a processed fluid to which copper sulfide was added.

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

The third aspect is the first or second aspect, wherein
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 openings of the filtration filter is 0.2 to 50 μm.

A fourth aspect is any one of the first to third aspects, wherein
The volume-based 50% cumulative particle diameter of the copper sulfide measured by the laser diffraction type particle size distribution measuring device is 20 to 35 μm.

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

A sixth aspect is any one of the first to fifth aspects, wherein
In the copper sulfide addition step, copper sulfide is added in an amount of 0.9 to 50 equivalents with respect to the metal in the liquid to be treated.

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

An eighth aspect is any one of the first to seventh aspects, wherein
Content of the said metal in the to-be-processed liquid provided to the said copper sulfide addition process is 10000 ppm or less.

A ninth aspect is any one of the first to eighth aspects, wherein
Before the copper sulfide addition step, the method further includes an alkaline substance addition step of adding an alkaline substance to the liquid to be treated to change the liquid to be neutral or alkaline.

A tenth aspect is any one of the first to ninth aspects, wherein
A slurry comprising a portion of the liquid component and the solid component in the solid-liquid separation step, and returning at least a portion of the slurry back into the liquid to be treated to which copper sulfide is added in the copper sulfide addition step It further has a circulation process.

An eleventh aspect is any one of the first to tenth aspects, wherein
Copper sulfide is divided and added in multiple times in the copper sulfide addition step.

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

The thirteenth aspect is
An apparatus for treating a liquid to be treated containing a metal having a solubility product of sulfide smaller than that of copper sulfide under neutral to alkaline conditions,
A copper sulfide supply mechanism which adds copper sulfide to a liquid to be treated under neutral to alkaline conditions;
A solid-liquid separation mechanism for separating a solid component and a liquid component including precipitation of a sulfide of the metal in the liquid to which the copper sulfide is added;
It is a processing apparatus of the to-be-processed liquid which has these.

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

A fifteenth aspect is the thirteenth or fourteenth aspect, wherein
It further has an alkaline substance supply mechanism for adding an alkaline substance to the liquid to be treated,
An alkaline substance is added by the alkaline substance supply mechanism, and copper sulfide is added by the copper sulfide supply mechanism to a liquid to be treated which has become neutral or alkaline.

A sixteenth aspect is any one of the thirteenth to fifteenth aspects, wherein
The solid-liquid separation mechanism is configured to obtain a slurry consisting of a part of the liquid component and the solid component by the mechanism, and at least a part of the slurry is copper sulfide by the copper sulfide supply mechanism. It further has a slurry circulation mechanism for returning to the liquid to be treated to be added.

  According to the present invention, a method for treating a liquid to be treated which secures the safety of operation while avoiding the increase in cost and complicated operation, and also secures the ease of maintenance of the treatment apparatus when carrying out filter filtration. And a processing device therefor.

FIG. 1 is a flowchart showing a method of treating a liquid to be treated according to this embodiment. FIG. 2 is a flowchart showing a method of treating a liquid to be treated in Example 2.

An embodiment of the present invention will be described in the following order using FIG. 1 which is a flowchart of the embodiment.
1. Method of treating 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. Evaporative concentration step 1-6. Condensed water treatment process Effects of Embodiment 3. Apparatus for treating the liquid to be treated 4. Others In addition, "-" in the present specification indicates a predetermined value or more and a predetermined value or less.

<1. Treatment method of liquid to be treated>
(1-1. Preparation process (dilution process, alkaline substance addition process) ((1) in FIG. 1))
The liquid to be treated used in the present embodiment is not particularly limited as long as it contains a predetermined metal, and may be waste liquid. The predetermined metal is a metal whose solubility product of sulfide is smaller than the solubility product of copper sulfide (II) (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 than this is fixed as a precipitate of sulfide and is removed from the liquid to be treated by 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 them.

  The concentration of the target metal in the liquid to be treated (the total concentration when two or more are contained) is not particularly limited, but is preferably 10000 ppm or less, and more preferably 2 to 8000 ppm from the economical point of view More preferably, it is 5 to 6000 ppm. Further, in this step, when 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 to a concentration of 10000 ppm or less may be performed.

  In addition, the liquid to be treated may be neutral to alkaline when the copper sulfide addition step described later is performed, and a neutral to alkaline liquid to be treated may be used, or it may be initially acidic or neutral. An alkaline substance may be added to the to-be-treated liquid to perform an alkaline substance addition step of changing the to-be-treated liquid from neutral to alkaline to prepare a neutral to alkaline to-be-treated liquid. . There is no particular limitation on the alkaline substance at that time, and, for example, ammonia, hydroxides of alkali metals or alkaline earth metals (such as caustic soda), etc. may be used. In addition, after the start of the below-mentioned copper sulfide addition process, to-be-processed liquid is processed under neutral or alkaline.

  In the present specification, "neutral to alkaline" refers to pH 7 or more (preferably 7 to 14, more preferably 8 to 13) at a liquid temperature of 25 ° C. That is, "processing under neutral to alkaline" refers to processing while maintaining a pH state of 7 or more 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 liquid to be treated is introduced, for example, into a reaction vessel, to which copper sulfide is added. By addition of copper sulfide, the target metal in the liquid to be treated is precipitated and precipitated as sulfide (immobilization). This solid component containing precipitates of sulfides of the target metal (the details of which will be described later) is extremely unlikely to cause clogging when a filter is used in the solid-liquid separation step.

The volume-based 50% cumulative particle diameter (D ₅₀ ) measured by the laser diffraction particle size distribution analyzer of the copper sulfide is preferably 10 to 50 μm from the viewpoint of reactivity with the target metal, and is preferably 20 to 35 μm. It is more preferable that

  In addition, it is preferable that the dissolution amount is 5.8 mass% or less (that is, 2.61 g or less) when 45 g of the copper sulfide is stirred at 300 rpm for 24 hours at 25 ° C. in 1 L of water of pH 7. Although various commercially available copper sulfides exist, use of copper sulfide with such a small amount of dissolution can efficiently fix the target metal. From the viewpoint of efficiently immobilizing the target metal, the dissolution amount of the copper sulfide is preferably 3.0% by mass or less, more preferably 1.5% by mass or less (note that the dissolution amount is usually 0). .05 mass% or more). As such copper sulfide, those manufactured by Nippon Chemical Industrial Co., Ltd. can be mentioned.

  The addition amount of copper sulfide is 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, with respect to the "equivalent ratio", one equivalent refers to the amount of copper sulfide required to sulfide the target metal, and that the equivalent ratio (copper sulfide / target metal) is 1.0 means that the target metal is theoretical. It shows that copper sulfide is added in an amount that can be completely converted to sulfide. 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 making the addition amount of copper sulfide into the said range, it becomes possible to fix an object metal very favorably, and it becomes possible to hold down the expense of copper sulfide.

  Although the present embodiment may be performed batchwise or continuously, the amount of copper sulfide added in the case of continuous operation is the average value of the concentration of the target metal in the liquid to be treated over a predetermined period. It is good to ask and determine based on it.

  It is also preferable to divide the addition of copper sulfide several times (two times or more). When this method is adopted, addition may be performed intermittently, and as the addition amount at that time, the addition amount after the second time may be larger or smaller than the addition amount of the first time.

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

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

(1-3. Solid-liquid separation process (metal recovery method) ((3) in FIG. 1))
In this step, the solid component including the precipitate of the sulfide of the target metal generated in the copper sulfide adding step is separated from the liquid component. In addition, it is not necessary to completely separate the solid component and the liquid component, and a part of the liquid component may be included in the solid component to form a slurry (in this way, implementation of the later-described slurry circulation step is easy Is advantageous). The solid components include sulfides of the target metal, and in some cases, residual copper sulfide and other contaminants that can not be reacted. In terms of separation efficiency, solid-liquid separation is preferably performed by filtration, and there is no particular limitation on a specific method or apparatus configuration for performing filtration. 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 quantity filtration system, which is a system in which the whole liquid to be treated is filtered to a filter, and in principle the solid component and the liquid component are completely separated. On the other hand, in the cross flow type, 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. There is also a feature that solid components do not excessively deposit on the filter as compared with the dead end type.

  The maximum width of the openings of the filter used for the filtration is preferably 0.2 to 50 μm, and more preferably 0.2 to 30 μm. If a filter with an opening of this condition is employed, clogging of the filter will be less likely to occur more reliably while solid components are reliably collected. In addition, the opening in this embodiment refers to the line | wire of the fiber which comprises a filter, and the thing of the largest width | variety of a line | wire gap.

  In addition, as shown in FIG. 1, it is preferable to carry out a circulation step of returning the solid component after the solid-liquid separation step back to the liquid to be treated which is a target to be subjected to the copper sulfide addition step. From the 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 may be performed in which copper sulfide is newly added (to fix the target metal present in the returned slurry). The concentration of the target metal in the liquid to be treated usually fluctuates with time, but by carrying out the (slurry) circulation step, the fluctuation corresponds to the amount corresponding to the maximum value of the concentration of the target metal. The addition of a small amount (for example, an amount corresponding to the average value of the concentration of the target metal) of copper sulfide can fix the target metal at a sufficient rate (the recovery rate of the target metal can be increased).

  The solid component separated in this step is mainly composed of the sulfide of the target metal as described above, and the solid component is recovered, the target metal is separated therefrom, and the target metal is finally recovered. . The specific method may be a known one. From the above, a series of steps including the above-described copper sulfide addition step and the solid-liquid separation step can be regarded as the “target metal recovery method”.

Moreover, since most of the substances constituting the solid component after solid-liquid separation are the sulfides and copper sulfides of the target metals, the solid component is suitable as a recycling material, and If even copper sulfide can be removed, it is possible to easily recover the target metal. That is, the present embodiment also has technical significance as a “manufacturing method of 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 processed through known steps such as a neutralization step, an evaporation and 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 (filtrate) produced in the solid-liquid separation step for neutralization. The acid to be added here may be any known one, for example, sulfuric acid may be adopted. The content of ammonia, which is a waste water control substance, in condensed water to be treated in the following condensed water treatment process by converting ammonia to ammonium sulfate (ammonium sulfate) (when ammonia is used as alkali) Can be significantly reduced.

(1-5. Evaporative concentration step ((5) in FIG. 1))
In this step, the liquid component (filtrate) neutralized in the neutralization step is evaporated and concentrated. In addition, what is necessary is just to process the concentrate which remained by evaporation concentration with a well-known method according to a substance, for example, you may process it as industrial waste.

(1-6. Condensed water treatment process ((6) in FIG. 1))
In this step, the condensed water obtained in the evaporation and concentration step obtained is appropriately treated. The treatment may be carried out by a known method in accordance with the substance contained in the condensed water. Examples of the above-mentioned method include aerobic treatment, anaerobic treatment, and RO membrane treatment.

<2. Effects of the embodiment>
In the present embodiment, the following effects are achieved through the above-described respective steps.

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

  Unlike the technology described in Patent Document 1, it is possible to dispense with the use of an oxidizing agent or a polymer flocculant, to suppress the generation of a large amount of residues after the target metal is recovered, and to increase the cost of residue treatment. It can be suppressed. In addition, it is possible to avoid complicated operations without the need to perform ORP control.

  Unlike the technique described in Patent Document 2, in the present embodiment, since the liquid to be treated containing the target metal is treated under neutral or alkaline conditions, the possibility of the generation of offensive odor and corrosive hydrogen sulfide is eliminated. It becomes possible to secure the safety of work.

  Furthermore, the solid component containing the precipitate of the sulfide of the target metal deposited after the copper sulfide addition step is less likely to cause clogging in the filter when solid-liquid separation is performed using the filter. 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, the safety of the operation is secured while avoiding the cost increase and the complicated operation, and the ease of maintenance is also secured when the filter filtration is performed. it can.

<3. Treatment device for liquid to be treated>
The following configuration is the one in which the technical idea of the method of treating a liquid to be treated is reflected in the device. Also in the processing apparatus having the following configuration, the effects of the embodiment of the processing method described above can be obtained.
[A device for treating a liquid to be treated containing a metal having a solubility product of sulfide smaller than that of copper sulfide under neutral to alkaline conditions,
A copper sulfide supply mechanism which adds copper sulfide to a neutral to alkaline liquid to be treated;
A solid-liquid separation mechanism for separating a solid component and a liquid component including precipitation of a sulfide of the metal in the liquid to which the copper sulfide is added;
An apparatus for treating a liquid to be treated. "

  Since the apparatus for processing under neutral or alkaline conditions, each of the above-mentioned mechanisms (in particular, the part in contact with the liquid to be treated) constituting the apparatus for treating liquid to be treated in this embodiment is formed of a material having alkali resistance. Is preferred. In addition, about the suitable example regarding the processing apparatus of a to-be-processed liquid, it is the same as that of the content and the reason described by the processing method of a to-be-processed liquid, and it abbreviate | omits a part.

  As one embodiment of the treatment apparatus, the liquid to be treated is introduced into the reaction vessel through a transfer means such as piping, where copper sulfide is added by the copper sulfide supply mechanism to fix the target metal. From the viewpoint of processing efficiency of the target metal, the transfer means is preferably configured to be able to continuously introduce the liquid to be treated to the reaction tank.

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

  At least a portion of the target metal in the liquid to be treated is fixed as a sulfide in the reaction tank. The liquid to be treated is withdrawn from the reaction tank and transferred to the next solid-liquid separation mechanism by transfer means such as piping. The processing apparatus may be configured to batch-fix the sulfide as sulfide and remove all the liquid to be treated from the reaction tank, or continuously perform the above-mentioned fixation continuously. It may be configured to withdraw 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 deposited by the addition of the copper sulfide can be separated from the liquid component. It may be a filtration device provided with a filter. If simple solid-liquid separation means such as a filtration device is adopted, the volume reduction of the solid-liquid separation mechanism can be achieved, and hence the volume reduction of the entire device can be achieved. At this time, it is preferable that the maximum width of the opening of the filter used for the filtration is 0.2 to 50 μm from the viewpoint of preventing clogging of the filter while reliably collecting the solid component.

  Moreover, the to-be-processed apparatus of this embodiment is an alkaline substance which adds an alkaline substance with respect to the to-be-processed liquid transferred with respect to the reaction tank in which an acidic or neutral to-be-processed liquid exists, or to the reaction tank. It may further have a supply mechanism (for example, a container for storing an alkaline substance and a pipe for transferring the same). In this case, copper sulfide is added by the above-mentioned copper sulfide supply mechanism to the to-be-processed liquid which becomes alkaline by addition of the alkaline material by the above-mentioned alkaline material supply mechanism.

  Further, the solid-liquid separation mechanism is configured to obtain a slurry consisting of a part of the liquid component and the solid component by the solid-liquid separation mechanism, and at least a part of the slurry is supplied to the copper sulfide A slurry circulation mechanism (for example, a slurry consisting of a part of the liquid component and the solid component in a reaction tank in which the liquid to be treated to which copper sulfide is to be added is returned) It is preferable to further have a pipe for transferring. As an example of the solid-liquid separation mechanism configured as described above, a filtration apparatus provided with a crossflow-type filtration filter can be mentioned.

<4. Other>
The technical scope of the present invention is not limited to the above-described embodiment, and includes various modifications and improvements as long as specific effects obtained by the configuration of the invention and the combination thereof can be derived. . For example, the combination of each of the above-described modifications and the combination with the contents exemplified in the above embodiment are also within the scope of the technical idea of the present invention.

For example, it has been stated that the above-mentioned method of treating the liquid to be treated (in the solid-liquid separation step) also has technical significance as a "method of producing a metal raw material" capable of easily recovering the target metal later. When this metal raw material is defined as a substance, it becomes as follows, and it is possible to easily recover the target metal.
“A solid target metal-containing substance, the total content of the target metal, copper and sulfur in the target metal-containing substance is 95% by mass or more, and the content of the target metal in the target metal-containing substance is 30 mass Target metal inclusions that are% or more. "
Among the target metals, silver is widely used in the industry because of its excellent conductivity and oxidation resistance, and there are many waste liquids containing this. It is preferable to carry out the treatment method of the present invention using such waste liquid as the liquid to be treated to obtain the above-mentioned target metal (silver) -containing substance, and to collect silver therefrom.

  Moreover, the point that the said metal containing material is suitable as a recycling raw material is also the advantageous effect of the processing method of the to-be-processed liquid of embodiment of this invention.

  In addition, although attention has been focused on recovering the target metal from the liquid to be treated, it may be focused on, for example, removing the target metal from the liquid to be treated. For example, when the target metal is inorganic mercury (Hg (II)), by performing a copper sulfide addition step, precipitation of mercury sulfide is generated, and the precipitation is removed to obtain inorganic mercury (Hg) from the liquid to be treated. (II)) can be removed. In this case, "the method of treating the liquid to be treated" is, in other words, "a method of removing the target metal from the liquid to be treated".

  Next, the present invention will be specifically described by way of examples. 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 sulfide (II) manufactured by Nippon Chemical Industrial Co., Ltd. in 7 mL of pure water. The copper sulfide slurry was ultrasonically dispersed at 29 ° C. for 2 minutes. The dispersed slurry was stirred at 700 rpm with a magnetic stirrer to prevent settling. The average particle diameter of the used copper sulfide was measured by Microtrack Bell MT3300EX II, and the specific surface area was measured by Mountech HM model-1210. As a result, the volume average particle diameter (cumulative 50% particle diameter on a volume basis) of copper sulfide in this example was 25 μm, and the specific surface area by BET method was 1.3 m ² / g. Table 1 summarizes this.

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

  The mass ratio of copper sulfide to silver (referred to as CuS / Ag ratio) relative to 0.5 L of raw water is 0.5 (equivalent ratio of CuS to Ag (CuS / Ag) is about 1.13), 1, 2 Or copper sulfide slurry was added so that it might become 3. These solutions were stirred with a magnetic stirrer for 30 minutes at 500 rpm. After stirring, filtration in a crossflow type was performed using a 0.45 μm filter (MF membrane: microfilter, hereinafter the same). As a filter, MICROSA MF (pore diameter: 0.45 μm) manufactured by Asahi Kasei Corp. was used. The pressure at the filter inlet was adjusted to 0.1 MPa or less, and the outlet pressure was adjusted to 0.01 MPa.

  In order to determine whether silver was fixed by copper sulfide, analysis of the silver concentration contained in the microfilter permeate was performed. In addition, analysis of copper concentration was also conducted in order to investigate that silver is sulfided while copper of copper sulfide is ionized. In addition, inductively coupled plasma atomic emission spectrometry (ICP-AES; HITACHI SPS-5100) was used for the analysis of the silver and copper concentration contained in the permeate.

  As a result, while silver concentration was 23.3 mg / L in raw water, 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. And the silver concentration was greatly reduced. This indicates that silver was fixed by copper sulfide.

  In addition, while the copper concentration was 38 mg / L in raw water, 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 (to move into the permeate) while the silver is sulfided.

When copper sulfide was added such that the CuS / Ag ratio was 1, the silver concentration in the permeate was 0.2 mg / L, and the silver concentration further decreased. Further, the copper concentration was 46 mg / L, and the copper concentration was 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 of copper sulfide to silver (CuS / Ag ratio) was 1 or more. In addition, it was confirmed that the concentration of eluted copper (difference between the concentration of copper in the permeate and the raw water) was consistent with that in the case where the exchange reaction between copper sulfide and silver occurred.

  Moreover, as a result of calculating the adsorption capacity of silver per copper sulfide unit mass, 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。 The amount of dissolution when 45 g of copper sulfide used in the above test was stirred at 300 rpm for 24 hours at room temperature (25 ° C.) in 1 L of water of pH 7 was 0.5 mass% (0.225 g). On the other hand, the removal test of silver from raw water was conducted in the same manner as described above using copper sulfide having a dissolution amount of 10.6% by mass determined under the same conditions. At this time, the CuS / Ag ratio was tested in five ways of 1.3, 1.6, 2.1, 2.5 and 2.9. The results (the removal rate of silver from the raw water) are shown in Table 4 below together with the above test results.

It can be seen that copper sulfide (manufactured by Nippon Kagaku Sangyo Co., Ltd.) having a dissolved amount of 0.5% by mass can achieve a high silver removal rate with a small amount used. This copper sulfide was used in the following examples.

Example 2
Example 2 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 Nippon Kagaku Sangyo Co., Ltd. in 100 mL of pure water. The copper sulfide slurry was ultrasonically dispersed at 29 ° C. for 5 minutes. The dispersed slurry was stirred by a magnetic stirrer at 400 rpm to prevent settling. In addition, the matter which is not specified was as described in Example 1.

As a to-be-processed liquid (raw water), the thing of the composition of the following Table 5 was used. The raw water used in Example 2 differs from the raw water used in Example 1 only in the concentrations of silver and copper.

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

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

  The permeate of the microfilter obtained 30 minutes after the start of the raw water supply was collected, and the concentrations of silver and copper in the permeate were measured. If the silver concentration of this permeate is low, it can be judged 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 concentration contained in the permeate.

As a result of the above test conducted at a hydraulic retention time of 30 minutes, the removal rate of silver was 99% or more. The same experiment was conducted 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. In other words, it was confirmed that silver can be effectively removed if the hydraulic residence time is set to 5 minutes, and continuous operation is possible. In addition, it is Table 6 below which summarized the silver concentration, copper concentration, and silver removal rate in said permeated fluid at the time of becoming each water flow volume in the case of 5 minutes of hydraulic residence time.

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 at a hydraulic retention time of 30 minutes, a portion of the liquid to be treated in the reaction tank was extracted 30 minutes after the supply of the raw water was started, and this liquid to be treated was subjected to pressure filtration. The mixture was separated into suspended matter and liquid components. In this pressure filtration, the filtration pressure was adjusted to 0.2 MPa, and 5 C filter paper (ADVANTEC) was used. The residue (suspended substance) on the filter paper is dried at 70 ° C. for 6 hours and pressure-decomposed with concentrated nitric acid and concentrated sulfuric acid mixed in a volume ratio of 3: 1 to obtain silver and copper concentrations contained in the decomposition solution It measured by ICP-AES and the sulfur concentration was measured by XRD. Table 7 shows the results.

The content of silver in the residue (suspended substance) was 70% by mass, the content of copper was 20% by mass, and the content of sulfur was 10% by mass. That is, in the suspended matter obtained in this example, silver is concentrated at a very high concentration, and the suspended matter substantially consists only of this silver and an element derived from copper sulfide used for fixing it. It has been confirmed that it is sufficiently valuable as a silver recycling material.

Example 3
A test was carried out in the same manner as in Example 2 except that the feed amount of the copper sulfide slurry was changed such that the CuS / Ag ratio was 48/108 (equivalent ratio 1/1) (the hydraulic retention time was 30). Minutes). The permeate of the microfilter obtained 30 minutes after starting supply of the 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 sulfide (II) manufactured by Nippon Chemical Industrial Co., Ltd. in 10 mL of pure water. The copper sulfide slurry was ultrasonically dispersed at 29 ° C. for 5 minutes. The dispersed slurry was stirred by a magnetic stirrer at 400 rpm to prevent settling.

  Raw water was prepared by adding a gold standard solution for 1000 ppm atomic absorption (manufactured by Kanto Chemical Co., Ltd.) to one having the same composition as in Example 1. The concentration of gold in the obtained gold-containing raw water was 5 ppm. In addition, the matter which is not specified was as described in Example 1. For example, the gold recovery test in Example 4 was performed in 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-mentioned copper sulfide slurry was added to 200 mL of gold-containing raw water previously prepared as described above. A copper sulfide slurry was added so that the concentration of copper sulfide as solid content in this gold-containing raw water would be 50, 100 and 200 ppm, respectively, to prepare each gold-containing raw water. The gold-containing raw water to which the copper sulfide slurry was added was stirred at room temperature for 45 minutes. Thereafter, the permeate of the microfilter was collected in the same manner as in Example 1 to analyze the gold concentration. The results are shown in Table 8.

As shown in Table 8, when the copper sulfide concentration is 100 or 200 ppm (ie, 100 ppm or more), the concentration of gold in the permeate is reduced from 4.8 ppm to 3.1 to 3.3 ppm, ie, the raw water It has been found that about 30% of the gold of the present invention can be recovered as sulfide precipitates.

Example 5
A copper sulfide slurry was prepared by dispersing 2.5 g of copper sulfide (II) manufactured by Nippon Chemical Industrial Co., Ltd. in 50 mL of pure water. The copper sulfide slurry was ultrasonically dispersed at 29 ° C. for 5 minutes. The dispersed slurry was stirred by a magnetic stirrer at 400 rpm to prevent settling.

  As a raw water, 1000 ppm of a standard solution for inorganic mercury (Hg (II)) atomic absorption (manufactured by Kanto Chemical Co., Ltd.) was added to one having a composition similar to that of Example 1 diluted 50 times with pure water. Prepared. The concentration of mercury in the obtained mercury-containing raw water was 7.5 ppm. In addition, the matter which is not specified was 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-mentioned copper sulfide slurry was added to 250 mL of the mercury-containing raw water previously prepared as described above. The above-mentioned slurries were respectively added so that the concentration of copper sulfide as solid content in the slurry-containing raw water containing the slurry was 100 and 200 ppm, to prepare respective raw water containing mercury. The mercury-containing raw water to which the copper sulfide slurry was added was stirred at room temperature for 45 minutes. Thereafter, the mercury-containing raw water was filtered with a syringe filter with a pore size of 0.45 μm. The filtrate was diluted 10 times with 5% nitric acid (manufactured by Kanto Chemical Co., Ltd.) and used for measurement of the amount of mercury. As an analyzer, Mercury MA-2000 mercury analyzer manufactured by Nippon Instruments was used. The results are shown in Table 9.

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

Example 6
As the copper sulfide slurry, the same one as in Example 1 was used, and as the raw water, raw water having the same composition as in Example 1 except that the silver concentration was 44 ppm was used. The pH was adjusted by adding nitric acid (for Kanto Chemical's harmful metals measurement) or sodium hydroxide to the raw water. The adjusted pH was set to 7, 11 and 13 respectively.

The above-mentioned copper sulfide slurry was added to 500 mL of raw water which had been pH-adjusted in advance. The copper sulfide concentration as solid content was set so that the CuS / Ag ratio was 2, and a copper sulfide slurry was added. The solution was stirred at room temperature for 30 minutes using a magnetic stirrer. After stirring, the solution was filtered with a syringe filter with a pore size of 0.45 μm, and the filtrate was subjected to measurement of silver concentration. In addition, the matter which is not specified was as described in Example 1. For example, the test in Example 6 was performed in a batch test. The above results are shown in Table 10 below. Silver was confirmed to be recovered from raw water of any pH.

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

  As raw water, one having the same composition as Example 1 except that the silver concentration was 1020 ppm was used. In addition, the matter which is not specified was 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。

To 300 mL of the raw water, 1.8 mL of the above-mentioned zinc sulfide slurry was added and stirred for 30 minutes. The zinc sulfide concentration as solid content in the mixed solution was 1080 ppm. The raw water after stirring was filtered with a syringe filter with a pore size of 0.45 μm. The silver concentration contained 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 the addition of zinc sulfide.

Claims (16)

A method of treating a liquid to be treated containing a metal having a solubility product of sulfide smaller than that of copper sulfide under neutral to alkaline conditions,
A copper sulfide addition step of adding copper sulfide to the neutral to alkaline liquid to be treated;
A solid-liquid separation step of separating a solid component and a liquid component including precipitation of a sulfide of the metal in the liquid to which the copper sulfide is added;
And a method of treating a liquid to be treated.   The method for treating a liquid to be treated according to claim 1, wherein the liquid to be treated is treated at pH 7-14.   The solid-liquid separation step is carried out by passing the liquid to be treated through a crossflow-type or dead-end type filtration filter, and the maximum width of the openings of the filtration filter is 0.2 to 50 μm. Or 2. The processing method of the to-be-processed liquid as described in 2.   The method for treating a liquid to be treated according to any one of claims 1 to 3, wherein the cumulative 50% particle diameter on a volume basis measured by the laser diffraction type particle size distribution measuring device of the copper sulfide is 20 to 35 μm.   The copper sulfide according to any one of claims 1 to 5, wherein the amount of copper sulfide dissolved in 45 g of the copper sulfide is stirred at 300 rpm for 24 hours at 25 ° C for 24 hours in 1 L of water at pH 7 The processing method of the to-be-processed liquid in any one of 4.   The processing method of the to-be-processed liquid in any one of Claims 1-5 which adds 0.9 to 50 equivalent copper sulfide with respect to the metal in the said to-be-processed liquid in the said copper sulfide addition process.   The method of treating a liquid to be treated according to any one of claims 1 to 6, wherein the metal is at least one selected from the group consisting of silver, mercury and gold.   The processing method of the to-be-processed liquid in any one of Claims 1-7 whose content of the said metal in the to-be-processed liquid provided to the said copper sulfide addition process is 10000 ppm or less.   The alkaline substance adding step according to any one of claims 1 to 8, further comprising adding an alkaline substance to the liquid to be treated to change the liquid to be neutral or alkaline before the copper sulfide adding step. The method of treating a liquid to be treated according to claim 1.   A slurry comprising a portion of the liquid component and the solid component in the solid-liquid separation step, and returning at least a portion of the slurry back into the liquid to be treated to which copper sulfide is added in the copper sulfide addition step The method for treating a liquid to be treated according to any one of claims 1 to 9, further comprising a circulating step.   The method for treating a liquid to be treated according to any one of claims 1 to 10, wherein copper sulfide is added in plural times in the copper sulfide addition step. The metal is silver,
The total content of silver, copper and sulfur in the solid component separated in the solid-liquid separation step is 95% by mass or more, and the content of silver in the solid component is 30% by mass or more. Item 12. A method of treating a liquid to be treated according to any one of items 1 to 11. An apparatus for treating a liquid to be treated containing a metal having a solubility product of sulfide smaller than that of copper sulfide under neutral to alkaline conditions,
A copper sulfide supply mechanism which adds copper sulfide to a neutral to alkaline liquid to be treated;
A solid-liquid separation mechanism for separating a solid component and a liquid component including precipitation of a sulfide of the metal in the liquid to which the copper sulfide is added;
An apparatus for treating a liquid to be treated.   The apparatus for treating a liquid to be treated according to claim 13, wherein the solid-liquid separation mechanism comprises a cross flow type or dead end type filtration filter, and the maximum width of the openings of the filtration filter is 0.2 to 50 μm. It further has an alkaline substance supply mechanism for adding an alkaline substance to the liquid to be treated,
14. The method according to claim 13, wherein copper sulfide is added by the copper sulfide supply mechanism to the liquid to be treated which is made alkaline or neutral by the addition of the alkaline material by the alkaline material supply mechanism. The processing apparatus of the to-be-processed liquid of 14th.   The solid-liquid separation mechanism is configured to obtain a slurry consisting of a part of the liquid component and the solid component by the mechanism, and at least a part of the slurry is copper sulfide by the copper sulfide supply mechanism. The apparatus for treating a liquid to be treated according to any one of claims 13 to 15, further comprising a slurry circulating mechanism for returning the liquid to be treated to be added.

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