KR101151950B1 - Producing method for crystalline scorodite - Google Patents

Abstract

An object of the present invention is to provide a method for producing scorodite having a low As elution value while suppressing the amount of washing water.

Step 1 of heating an acidic aqueous solution containing at least 19 g / L of pentavalent As and at least one equivalent of trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite, and then reacting the synthesized scorodite with a solution. BET specific surface area comprising the step 2 of separating the solid by a liquid-liquid separation therefrom and the step 3 in which the scorodite is separated by a solid-liquid separation from the water washing liquid after the scorodite is water washed. It is a manufacturing method of crystalline scorodite which is 10 m <2> / g or more.

Skorodite, Cake, Funnel, BET Specific Surface Area, Jet Agitter

Description

Production Method of Crystalline Skorodite {PRODUCING METHOD FOR CRYSTALLINE SCORODITE}

The present invention relates to a method for producing scorodite. In particular, it is related with the manufacturing method of scorodite from the electrolytic precipitation copper computed by a copper smelting process.

Various impurities are mixed in copper ore, and such impurities include arsenic (As). Arsenic (As) is volatilized and separated by high heat in the dry process of copper smelting, but a part is mixed in crude copper and brought into the electrolytic refining process of copper.

As contained in the crude copper (copper anode) is partially eluted in the electrolyte, and the cosmetic fraction is mixed in the anode slime that precipitates at the bottom of the electrolytic cell. In addition, since the amount of copper eluted from the positive electrode is generally larger than the amount of copper deposited on the negative electrode, the copper concentration in the electrolytic solution gradually increases. For this reason, part of the electrolyte is leaked into a separate electrolytic cell to control the quality of the electrolyte. The leaked electrolytic solution is decopperized to precipitate impurities such as Cu and As on the cathode, and to precipitate them on the bottom of the electrolytic cell to separate and recover impurities such as Cu and As. In this field, both the precipitate at the bottom of these electrolyzers and the precipitate at the cathode are called electrolytic precipitated copper. Electrolytic precipitated copper typically contains 20 to 50 wt.% Arsenic, 0.1 to 6 wt.% Bismuth and 30 to 60 wt.% Copper. In addition, it contains 0.5-8 wt.% Of antimony and 0.5-10 wt.% Of lead.

The electrolytic precipitated copper is usually repeated in a copper smelting process, but for that purpose, it is preferable to separate impurities such as As from the electrolytic precipitated copper. In addition, the method of using As as valuables also remains. Therefore, there is a need for a technique for separating and recovering As from an electrolytic precipitated copper at high quality. Arsenic separated and recovered is preferably immobilized as a stable compound so as not to cause environmental pollution.

In order to fix arsenic, it is known that it is effective to produce crystals of scorodite (FeAsO ₄ .2H ₂ O) which is an iron arsenic compound. Crystalline scorodite is chemically stable and suitable for long term storage. On the other hand, the scorodite is also amorphous, which lacks stability and is not suitable for long-term storage.

Patent Document 1 discloses a method for producing crystalline scorodite, and according to this, after optionally treating the electrolytic precipitated copper with water, the As component is penetrated by introducing an oxygen-containing gas into the electrolytic precipitated copper in sulfuric acid. Sulfuric acid leaching to oxidize and elute is performed, and trivalent iron is added to the sulfuric acid leaching solution to produce crystalline scorodite (FeAsO ₄ .2H ₂ O).

[Patent Document 1] Japanese Patent Application Publication No. 2008-81784

According to the method of patent document 1, the stable crystalline scorodite can be manufactured reliably. Furthermore, after the synthesis of scorodite it is described to wash it with water. However, the relationship between the As elution value and the cleaning method is not known, and it is not clear how the As elution value from scorodite is related to the amount of washing water. If the amount of washing water of scorodite can be reduced, advantages, such as reducing the burden on a drainage facility and reducing the quantity of use, are considered industrially advantageous.

Then, in this invention, it is a main subject to provide the manufacturing method of the scorodite which can achieve the low As elution value even if the amount of washing water is suppressed.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve the said subject, as the As concentration in the solution before the reaction of scorodite rises, the scorodite obtained is improved, and it is possible to perform scoro It has been found that the As elution value from the die can be reduced below the environmental standard. Commonly, increasing the As concentration in the solution before the reaction increases the As concentration in the solution after the reaction and increases the As concentration attached to the scorodite, which increases the amount of washing water to wash it out. It was.

The present invention completed based on the above knowledge in one aspect,

Step 1 of heating an acidic aqueous solution containing at least 19 g / L of pentavalent As and at least one equivalent of trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite;

Step 2 in which the synthesized scorodite is separated from the solution after the reaction by solid-liquid separation;

Crystalline scorodie with a BET specific surface area of 10 m 2 / g or more, after which the step 3 of separating the scorodite from the water rinse by solid-liquid separation after the scorodite is water washed It is a manufacturing method of tart. Also,

Step 1 of heating an acidic aqueous solution containing 19 to 75 g / L of pentavalent As and 1 to 1.5 equivalents of trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite;

Step 2 in which the synthesized scorodite is separated from the solution after the reaction by solid-liquid separation;

Crystalline scouring having a BET specific surface area of 10 to 20 m 2 / g, after which the step 3 of separating the scorodite from the water rinse by solid-liquid separation after the scorodite is water washed It is a manufacturing method of rodite.

In another embodiment of the method for producing scorodite according to the present invention, the scorodite of step 3 is washed with water using 10 L or less water per kg of dry weight of scorodite.

In still another embodiment of the method for producing scorodite according to the present invention, step 3 is performed by arranging scorodite in the filter press, and then supplying the washing water and then pressing it.

In yet another embodiment of the method for producing scorodite according to the present invention, the washing and pressing of step 3 are repeated one or more times, and the washing water supplied to the filter press every time is performed. It is 1-10 L per 1 kg of dry weight of rodite.

In yet another embodiment of the method for producing scorodite according to the present invention, the concentration of pentavalent As used in Step 1 is set to 60 to 75 g / L, and water washing of scorodite in Step 3 is performed. It is performed using 10 L or less water per 1 kg of dry weights of silver scorodite.

In another embodiment of the method for producing scorodite according to the present invention, the scorodite obtained is in the form of secondary particles.

In another embodiment of the method for producing scorodite according to the present invention, the acidic aqueous solution of Step 1 is prepared by adding trivalent Fe to a sulfuric acid leaching solution of electrolytic precipitated copper.

According to the present invention, scorodite having low As elution property can be produced only by washing with a small amount of washing water.

One of the main problems of the present invention,

Step 1 of heating an acidic aqueous solution containing at least 19 g / L of pentavalent As and at least one equivalent of trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite;

Step 2 in which the synthesized scorodite is separated from the solution after the reaction by solid-liquid separation;

Crystalline scorodie with a BET specific surface area of 10 m 2 / g or more, after which the step 3 of separating the scorodite from the water rinse by solid-liquid separation after the scorodite is water washed It is a manufacturing method of tart.

Process 1

In step 1, scorodite is synthesized. Synthesis of scorodite can be performed by heating an acidic aqueous solution containing pentavalent As and trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite. Regarding the synthesis conditions of scorodite, any conditions known to those skilled in the art to be advantageous for the synthesis of crystalline scorodite may be adopted, but suitable conditions are exemplified below.

For example, pentavalent As can be given in the form of scattering (H ₃ AsO ₄ ) or the like. Typically, pentavalent As is present in the form of fly ash (H ₃ AsO ₄ ) in the sulfuric acid leaching solution after leaching sulfuric acid from the electrolytic precipitated copper.

Trivalent Fe can be provided in the form of iron oxide, iron sulfate, iron chloride, iron hydroxide etc., for example. The trivalent Fe is preferably provided in the form of an acidic aqueous solution from the viewpoint of the reaction in the aqueous solution, and the ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) from the viewpoint that it is most effective to return the iron removal solution to the preceding electrolyte. Preferably in the form of an aqueous solution. Moreover, the polyferric sulfate aqueous solution used for wastewater treatment etc. can also be used.

An acidic aqueous solution can be given as aqueous solution, such as hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, for example. Typically, a sulfuric acid leaching solution after leaching sulfuric acid from electrolytic precipitated copper is used. The method of leaching sulfuric acid is mentioned later.

In order to increase the reaction rate of As contained in the acidic aqueous solution, it is preferable to make the trivalent Fe be 1.0 equivalent or more to the amount of the pentavalent As, and from the economic point of view, preferably 1.0 to 1.5 equivalent, and typically 1.0 to 1.1 equivalents. If it is less than 1.0 equivalent, As will easily elute from the obtained scorodite.

It is advantageous from the viewpoint of scorodite synthesis that the pH of the acidic aqueous solution is 0.3 to 2.2, preferably 0.4 to 1.2.

When the pentavalent As concentration contained in the acidic aqueous solution before the reaction decreases, the amount of water required for washing the obtained scorodite increases, so that the pentavalent As concentration is as high as possible. However, if the solubility of As is exceeded, As is precipitated and the yield of scorodite falls, It is preferable to make it so that the solubility of As is below. Further, when the acidic aqueous solution is concentrated to increase the As concentration, a metal component (eg, copper) having a lower solubility than the As coexisting in the acidic aqueous solution is precipitated first, and thus an operation for removing the acidic aqueous solution is required. Therefore, what is necessary is just to make it contain 19 g / L or more, Preferably 19-75 g / L pentavalent As is contained in the acidic aqueous solution before reaction. In the case where the reduction of the amount of washing water is important, the concentration of As in the acidic aqueous solution before the reaction is preferably 60 to 75 g / L, and when it is important to prevent the precipitation of coexistent metals, the concentration of As is preferably 19 to 40 g / L. Do. What is necessary is just to adjust As concentration in acidic aqueous solution according to the increase and decrease of the water which is a solvent.

Crystalline scorodite can be produced by heating the acidic solution to, for example, 60-95 ° C., typically 80-95 ° C., under atmospheric pressure, for example a sufficient amount of crystalline scotch by reacting for 8-72 hours. Rodite is produced. As is oxidized to pentavalent, crystalline scorodite is produced by trivalent iron and high reaction efficiency.

Step 2

In step 2, the synthesized scorodite is separated from the solution after the reaction by solid-liquid separation. After the reaction, the solution contains arsenic, copper, and other metal ions, and if they are attached to scorodite, they are eluted at the time of storage, so they need to be sufficiently removed. The method of solid-liquid separation may be performed by any known method, and there is no particular limitation, but filtration is common. Examples of the filtration include gravity (natural) filtration, suction filtration, pressure filtration and centrifugal filtration. In general, gravity filtration has the worst separation efficiency, and pressure filtration and centrifugal filtration have the best efficiency. Suction filtration is in between.

However, in order to obtain the separation efficiency aimed at by the present invention, even if the solid-liquid separation is performed by any method, water washing is necessary after that. Therefore, in consideration of later water washing efficiency, it is important to prevent cracks in the cake of scorodite obtained by filtration in the step of separating the scorodite into a solution after the reaction. This is because if the cake is cracked, the resistance of the water in the cracked portion is reduced in subsequent water washing, so that the water flows intensively in the portion, resulting in uneven cleaning.

In order to avoid cracks, suction filtration is preferably not performed, gravity filtration (natural filtration) is preferable, and pressure filtration by a filter press is more preferable. The filter press has a vertical type (the pressing direction of the cake is a vertical direction) and a horizontal type (the pressing direction of the cake is a horizontal direction), but in the case of using a vertical filter press, the effect of suppressing the occurrence of cracks is particularly high. This is because the vertical mold can be a cake having a uniform thickness regardless of the amount of the horizontal mold. In the horizontal filter press, the slurry is filled from the lower part of the chamber, and it is difficult to make a cake having a uniform thickness like a vertical filter press, and gravity tends to cause cracks in the cake. Therefore, when the cake is water-washed, there is a possibility that water flows intensively in thin portions or cracks of the cake, and it is difficult to uniformly wash the whole as much as the vertical type.

Process 3

In Step 2, most of the solution after the reaction attached to the scorodite is removed. However, in the scorodite in this step, the elution of arsenic does not often fall below the standard value of the domestic disposal site in Japan. The variation of the elution value for each product is also large. Therefore, in order to stably obtain low-elasticity scorodite, it is important to perform water washing again to separate the solution after the reaction from the scorodite.

In step 3, the scorodite is washed with water, and then the scorodite is separated from the water wash by solid-liquid separation. The water-soluble component is washed away by water washing, and the arsenic dissolution property of scorodite gradually decreases each time the number of times is overlapped. This is because most of the elution of arsenic from scorodite is due to the adhesion of the solution after the reaction, not from the scorodite itself.

In addition, the amorphous scorodite which can be produced as a by-product during the synthesis of scorodite has high water solubility, and thus it is considered that it is removed together with the solution after the reaction by this washing operation. Thus, the cleaning operation not only removes the solution from the scorodite after the reaction, but also serves to remove the by-produced amorphous scorodite.

What is necessary is just to perform the method of water washing by a well-known arbitrary method, Although there is no restriction | limiting in particular, The following methods are mentioned as an efficient washing method.

In the case where washing and filtration are continuously performed using a funnel, a washing method in which cracks do not occur in the cake of scorodite is preferable. This is because cracking adversely affects the cleaning efficiency. In filtration with funnels, no cracking occurs during the presence of water on the cake, i.e. while the cake is completely immersed in water, but if the water breaks along and the cake is exposed to the surface, the volume of the cake shrinks and cracks. This happens. Therefore, it is preferable to supply water so that it does not break in the middle, and to carry out filtration so that the whole cake may be covered with wash water (for example, the state fully immersed).

Moreover, the method of solid-liquid separation after adding scorodite to a washing tank, stirring, repulping, etc. is also effective. What is necessary is just to measure the density | concentration of the solution component after reaction contained in a water wash liquid with respect to the water wash liquid after solid-liquid separation. The method of solid-liquid separation at this time may use what kind of method mentioned above at the process 2, and does not have to worry about generation | occurrence | production of a crack.

Another preferred method is to produce a cake of scorodite with a filter press, and to supply the washing water in the filter press and then pressurize it to immediately wash and filter the cake (for example, a vertical filter press manufactured by Larox) Using). According to this method, washing filtration operation can be performed more easily than repulp. In the case of a vertical filter press, cracks are less likely to occur.

When performing process 3 using a filter press, even if the quantity of washing | cleaning of the whole is the same, washing | cleaning and crimping | dividing into several times and cleaning efficiency will become high. For example, the washing water supplied to the filter press every time washing and pressing is performed at 1 to 10 L per 1 kg of dry weight of scorodite, preferably at 1 to 5 L. Typically 2-3 L. When the amount of washing water is to be reduced, the second half of the washing water supplied to the filter press can be recovered at any time and used for the first half of the next time.

The amount of water required for water washing is correlated with the concentration of As contained in the acidic aqueous solution (pre-reaction solution) before the reaction. The amount of washing water required to satisfy the condition is reduced. Specifically, even if any of the above washing methods are employed, the amount of washing water required for the As elution value from scorodite to be less than the environmental reference value is scorodite when the As concentration contained in the solution before the reaction is 19 g / L or more. It can be 15 L or less per kg of dry weight of, preferably 10 L or less, typically 8 to 10 L, and when the As concentration contained in the solution before the reaction is 30 g / L or more, It can be 10 L or less per kg of dry weight of a die, Preferably it can be 8 L or less, and can be 5-8 L typically.

Sulfuric Acid Leaching Solution of Electrolytic Precipitated Copper

A sulfuric acid leaching solution of electrolytic precipitated copper suitable as a raw material for scorodite can be obtained, for example, as follows.

First, water washing treatment is optionally performed on electrolytic precipitated copper. In the water washing treatment, electrolytic precipitated copper is repulsed with water and stirred for 0.5 to 6 hours, and the amount of electrolyte contained in the production of electrolytic precipitated copper (including copper sulfate, Ni, Fe, etc.) and the amount of electrolytic precipitated copper. After dissolving Ni, Fe, and the like, the slurry can be filtered and subjected to solid-liquid separation. In this process, most of Fe and Ni can be separated from the electrolytic precipitated copper.

However, this operation clarifies the amount of copper (not dissolved in water) excluding copper sulfate in the amount of copper in the electrolytic precipitated copper, so as to more accurately determine the amount of sulfuric acid required for sulfuric acid leaching of the electrolytic precipitated copper performed in the next step. This operation is primarily intended to be performed. If the trace elements such as Ni and Fe are not particularly concerned, or if the content of copper sulfate is known in advance or if the amount of electrolyte solution to the electrolytic precipitated copper is small, this step is not necessary.

After optionally performing a water washing treatment, the solution was stirred at a solution temperature and time sufficient to oxidize the As component contained in the electrolytic precipitated copper to pentavalent, while introducing an oxygen-containing gas into the electrolytic precipitated copper in sulfuric acid, and leaching sulfuric acid. Subsequently, the solid-liquid separation is carried out with a leaching residue containing Sb and Bi components and a sulfuric acid leaching liquid containing a pentavalent As component.

The leaching reaction occurring at this time is generally oxidized to Cu up to Cu ²⁺ and As up to As ^{5+ according} to the following equation.

The amount of sulfuric acid used is preferably 1.0 to 1.2 equivalents based on the amount of Cu. In the case of less than 1.0 equivalent, the leaching liquid is weakly acidic, and precipitates such as Cu ₃ AsO ₄ are formed to lower the leaching rates of Cu and As. When it exceeds 1.2 equivalent, although it is not influenced by the leaching rate of Cu and As, the amount of sulfuric acid used increases. The concentration of Cu and As in the sulfuric acid solution is not particularly limited. However, when the solubility is exceeded, the leaching rates of Cu and As are lowered, so that the solubility of Cu ²⁺ and As ⁵⁺ is preferably lower than that.

In addition, a suitable pH for the production of crystalline scorodite to be synthesized thereafter is 0.3 to 2.2, preferably 0.4 to 1.2. However, when the sulfuric acid concentration is low, the efficiency of sulfuric acid leaching, that is, the recovery efficiency of copper or arsenic decreases. Since there exists a tendency, it is preferable that the density | concentration of the sulfuric acid used at the time of sulfuric acid leaching is a density | concentration which pH becomes less than one. In addition, even if the pH of the sulfuric acid leaching solution is 1 or more, the trivalent iron added when synthesizing scorodite is preferably provided in the form of an acidic aqueous solution. For example, the ferric sulfate aqueous solution or the second polysulfate solution The pH of the aqueous solution of iron is about 0.6.

In sulfuric acid leaching, in order to oxidize As to pentavalent, it is good to stir for 4.5 to 11 hours at 70-95 degreeC, Preferably it is 7 to 11 hours at 80-95 degreeC. Since sulfuric acid leaching is an exothermic reaction, it can also be performed, especially without heating from the exterior. Stirring time may be performed longer, and what is necessary is just to determine suitably by the balance of an economy and an effect.

In order to increase the oxidation efficiency of As, it is better to supply a small amount of bubbles of the oxygen-containing gas to be introduced and supply a sufficient amount (for example, 10 equivalents of oxygen / 7 hours to copper). Therefore, it is preferable to perform stirring vigorously, for example, it is suitable to introduce | transduce and / or agitate an oxygen containing gas by jet injection. This value is a case of jet injection (the "jet agitator" brand name), and in the case of a stirrer using a normal turbine blade, the reaction efficiency is lowered, and even if the amount of oxygen-containing gas is introduced 3.5 times or more, the reaction time is twice or more. It becomes necessary. By performing the mantissa control of As in this step, the subsequent scorodite generation becomes easy. Cu ²⁺ also has the effect of promoting the oxidation of As.

The oxygen-containing gas is not particularly limited as long as it does not have a significant adverse effect on the reaction. For example, a mixture of pure oxygen, oxygen, and an inert gas can be used. It is preferable to set it as air from a viewpoint of handleability and cost.

By adding trivalent iron to the sulfuric acid leaching liquid of the electrolytic precipitated copper thus obtained, an acidic aqueous solution containing pentavalent As and trivalent Fe can be obtained. In this case, examples of the trivalent iron include iron oxide, iron sulfate, iron chloride, iron hydroxide, and the like. However, the trivalent iron is preferably provided in the form of an acidic aqueous solution from the viewpoint of reacting in an aqueous solution. It is preferable to provide in the form of an aqueous solution of ferric sulfate [Fe ₂ (SO ₄ ) ₃ ] from the viewpoint that it is most effective to return the electrolytic solution to the electrolytic solution. Moreover, the ferric polysulfate aqueous solution used for wastewater treatment etc. can also be used.

The amount of the trivalent iron used is preferably 1.0 equivalent or more relative to the amount of As from the viewpoint of removing As, and preferably from 1.0 to 1.5 equivalents from an economic point of view.

The scorodite produced by the method according to the present invention generally has a BET specific surface area of 10 m 2 / g or more, and in a typical embodiment, 10 to 20 m 2 / g. The scorodite produced by the method concerning this invention becomes a form of the secondary particle which the primary particle aggregated in one Embodiment. Conventionally, in order to suppress As elution, it has been desirable to reduce the BET specific surface area of scorodite. However, the scorodite obtained by the production method of the present invention has a large BET specific surface area. The castle is low enough.

Hereinafter, examples will be described to better understand the present invention and its advantages, but the present invention is not limited thereto.

Example 1

1.Water washing treatment of electrolytic precipitated copper

The following preliminary test was done using a part of electrolytic precipitation copper of a raw material. 2000 g (wet weight) of electrolytic precipitated copper was repulped with 5000 mL of water and stirred for 4 hours to dissolve the electrolyte solution (copper sulfate, nickel, iron, etc.) attached during the preparation of electrolytic precipitated copper, and then the slurry was filtered to solid-liquid separation. It was. The obtained debris was dried and used as a sample for analysis. The weight of the residue after drying was 1636.9 g. The analysis values are shown in Table 1. In addition, this operation clarifies the amount of zero-valent (not dissolved in water) copper excluding copper sulfate in the amount of copper in the electrolytic precipitated copper, and more accurately calculates the amount of sulfuric acid required for leaching the next electrolytic precipitated copper into sulfuric acid. It is operation to perform. If the content of copper sulfate is known or there is little carry-in of electrolyte solution to electrolytic precipitation copper, it is not necessary to perform this process.

2. Sulfuric Acid Leaching of Electrolytic Precipitated Copper

50 kg (wet weight, 9.2% moisture) of 75% sulfuric acid in 48 kg (electrolytic precipitated copper contained in electrolytic precipitated copper prepared in the same batch as the above-mentioned electrolytic precipitated copper, and 1 for copper insoluble in water) Equivalent weight), and water was added to make the slurry amount 175L. The mixture was leached for 12 hours while introducing air at 250 L / min to make As valent. In order to increase the reaction efficiency, it is effective to reduce the bubble of the air to be introduced. Therefore, a jet agitator (JET AJITER manufactured by SHIMAZAKI Co., Ltd.) was used for introducing and stirring the air. In addition, liquid temperature was controlled at 88 degreeC. After diluting about 3 times after sulfuric acid leaching, the leaching was filtered to solid-liquid separation. The residue was washed with water, and the washing water was added to the sulfuric acid leaching solution. Table 2 shows the amounts of the obtained sulfuric acid leaching liquid and sulfuric acid leaching residue.

3. Synthesis of Skorodite

To 530 L of the sulfuric acid leaching solution described above, 64 L of ferric sulfate (hereinafter referred to as polyiron) manufactured by Nitetsu Kogyo Co., Ltd. as trivalent iron was added (1.1 equivalents of ferric iron to arsenic contained in the sulfuric acid leaching solution). As a result of analyzing the concentration of arsenic, the mixture was 20.2 g / L and had a pH of 0.55 (room temperature). Then, it heated to 95 degreeC and synthesize | combined scorodite for 24 hours. Immediately after mixing the sulfuric acid leaching liquid and polyiron at room temperature, the reaction did not proceed, but precipitation of scorodite was observed around 87 ° C with heating. After the synthesis of scorodite, the scorodite crystals were filtered to solid-liquid separation. The quantity of the obtained scorodite crystal and the crystal filtration after liquid is shown in Table 3.

4. Water washing method of scorodite crystal

A part of the scorodite synthesized in Example 1 was filtered by a Larox company vertical filter press (Model: Filtration test apparatus PF 0.1H2 type), and then compressed to separate the solid-liquid into a cake of scorodite. It was. Subsequently, 10L of water was flowed into the cake in the chamber of the filter press, and it wash | cleaned, crimped, and air blowed. This operation was repeated seven times. After the above washing, the elution value of arsenic was 0.09 mg / L (test according to Japanese Environmental Notification 13), and it was confirmed that arsenic was stable. The scorodite obtained from this can also be said to be crystalline. The scorodite after filtration was 6.02 kg (wet amount, 4.86 kg of dry weight conversion). As a result, the amount of the water washing water per 1 kg of the dry amount of scorodite was 14 liters.

An example of the SEM image of the obtained scorodite is shown in FIG. It can be seen that it is in the form of secondary particles. Moreover, it was 17.5 m <2> / g when the BET specific surface area (BET 1-point method) was measured using the canthasorb (QS-17) by Yuasa Ionics.

Example 2

1.Sulfate Leaching of Electrolytic Precipitated Copper

50 kg (wet weight, 9.2% of moisture) of 48 kg of sulfuric acid was contained in 50 kg (wet weight, 9.2% of moisture) of electrolytic precipitated copper manufactured by the same batch as the electrolytic precipitated copper of Example 1, and 1 equivalent with respect to copper insoluble in water ), And further added water to make the slurry amount 175L. The mixture was leached for 13 hours while introducing air at 230 L / min to make As valent. In order to increase the reaction efficiency, it is effective to reduce the bubble of the air to be introduced. Therefore, a jet agitator (JET AJITER manufactured by SHIMAZAKI Co., Ltd.) was used for introducing and stirring the air. In addition, liquid temperature was controlled at 88 degreeC. After diluting about 2.4-fold after sulfuric acid leaching, the leaching was filtered to solid-liquid separation. The residue was washed with water, and the washing water was added to the sulfuric acid leaching solution. Table 4 shows the amounts of the obtained sulfuric acid leaching liquid and sulfuric acid leaching residue.

2. Synthesis of Skorodite

To 420 L of the sulfuric acid leaching solution, 67 L of ferric sulfate (hereinafter referred to as polyiron) manufactured by Nitetsu Kogyo Co., Ltd. as trivalent iron (1.1 equivalents of ferric iron relative to arsenic contained in the sulfuric acid leaching solution) was added. As a result of analyzing the concentration of arsenic, the mixture was 26.1 g / L and pH 0.63 (room temperature). Then, it heated to 95 degreeC and synthesize | combined scorodite for 24 hours. Immediately after mixing the sulfuric acid leaching solution and polyiron at room temperature, the reaction did not proceed, but precipitation of scorodite was observed at around 79 ° C with heating. After the synthesis of scorodite, the scorodite crystals were filtered to solid-liquid separation. The quantity of the obtained scorodite crystal and the crystal filtration after liquid is shown in Table 5.

3.water washing method of scorodite crystal

A part of the scorodite synthesized in Example 2 was filtered with a Larox company vertical filter press (Model: Filtration test apparatus PF 0.1H2 type), and then compressed to separate the solid-liquid into a cake of scorodite. It was. Subsequently, 10 L of water was flowed into the cake in the chamber of the filter press, and washing | cleaning, compression, and air blow were performed. This operation was repeated twice. At the end of the second operation, it was confirmed that the arsenic elution value of scorodite was 0.10 mg / L (test according to Japanese Environmental Notification No. 13), and arsenic was stable. The scorodite obtained from this can also be said to be crystalline. The scorodite after filtration was 4.54 kg (wet amount, 3.25 kg of dry weight conversion). As a result, the amount of water washing water per 1 kg of dry weight of scorodite was 6L. Scorrodite was observed by SEM to confirm that it was in the form of secondary particles. Moreover, it was 14.8 m <2> / g when the BET specific surface area (BET 1-point method) was measured using the canthasorb (QS-17) by Yuasa Ionics.

Example 3

1.Sulfate Leaching of Electrolytic Precipitated Copper

To 858 g (dry weight) of electrolytic precipitated copper, 638 g (1.0 equivalent of copper relative to copper contained in electrolytic precipitated copper) of 98% concentrated sulfuric acid was added, and water was added to make the slurry amount 2.5L (slurry concentration 340 g / L). The mixture was leached for 9 hours while introducing air at 5.1 L / min. In order to increase the reaction efficiency, it is effective to reduce the bubble of the air to be introduced. Therefore, a jet agitator (JET AJITER manufactured by SHIMAZAKI Co., Ltd.) was used for introducing and stirring the air. In addition, liquid temperature was controlled at 80 degreeC by the water bath. ORP gradually increased with leaching, and 148 mV at the start of leaching was 270 mV at the end of leaching. The behavior of the ORP is characterized by a sharp rise near the end of the leaching, and the end point can be easily confirmed. The copper concentration at the end of the leaching is about 160 g / L, far exceeding about 50 g / L of solubility at room temperature. Without diluting the leach solution, it was left overnight at room temperature to precipitate copper sulfate pentahydrate (liquid). Thereafter, the leach residue and the tablet were filtered, and the mixture was divided into a sulfuric acid leaching filtration liquor and a sulfuric acid leaching residue and scavenger mixture. The sulfuric acid leaching residue and the supporting mixture were washed with about 1 L of water to remove the adhered sulfuric acid leaching liquid, and the washing water was filtered to make the filtrate the washing liquid. The filter residue was added to the sulfuric acid leaching residue / cold mixture. Since the plate wash liquid had a high arsenic concentration of about 30 g / L, it was later used as a raw material for scorodite together with sulfuric acid leaching filtration. After washing with water, the sulfuric acid leachate and dilution mixture was dissolved in 2.5 L of water, and then separated by filtration into sulfuric acid leach residue and the liquid solution. Table 6 shows the amounts of the sulfuric acid leaching filtered liquid obtained and the sulfuric acid leaching residue.

The above operation (all operations described in Table 6) was repeated four times, and the first two times were mixed with the sulfuric acid leaching filtration after liquid, and the four times with the plate wash liquid, to prepare a raw material solution of scorodite.

2. Synthesis of Skorodite

2,600 mL of ferric sulfate (hereinafter referred to as polyiron) manufactured by Nittsu Kogyo Co., Ltd. as trivalent iron (7 equivalents of ferric iron relative to arsenic contained in sulphate leaching solution) to 7347 mL of the mixed solution of the sulfuric acid leaching filtration after-washing solution and the plate wash liquid. Was added. As a result of analyzing the concentration of arsenic in the mixed solution, the concentration was 47 g / L, which was in good agreement with the calculated value from the raw materials. Moreover, it was pH 0.32 (room temperature). Finally, 450 g (dry weight) of crystalline scorodite was added as seed crystals. Then, it heated to 95 degreeC and synthesize | combined scorodite for 54 hours. Immediately after mixing the sulfuric acid leaching liquid and polyiron at room temperature, the reaction did not proceed, but precipitation of scorodite was observed about 3 hours after reaching 95 ° C with heating. After completion of the synthesis of scorodite, the scorodite crystals were suction filtered with a Buchner funnel to give solid-liquid separation. The quantity of the obtained scorodite crystal and the crystal filtration after liquid is shown in Table 7.

3. Water washing method of scorodite crystal

In Example 3, 4060 mL of water was added to 1995.9 g of scorodite (1813 g in terms of wet and dry weight) containing the seed crystals, which were synthesized and solid-liquid separated, and the resultant was pulp and stirred for 10 minutes, followed by suction filtration with a Buchner funnel. Separated with rodite and washing solution. This operation was repeated three times. At the end of the third operation, the arsenic elution value of scorodite was 0.05 mg / L (test according to Japanese Environmental Notice 13), and it was confirmed that arsenic was stable. The scorodite obtained from this can also be made crystalline. As a result, the amount of water washing water per 1 kg of dry weight of scorodite was 6.7 L. The obtained scorodite was observed by SEM and it confirmed that it was in the form of a secondary particle. Moreover, it was 18.7 m <2> / g when the BET specific surface area (BET 1-point method) was measured using the canthasorb (QS-17) by Yuasa Ionics.

Example 4

1.Sulfate Leaching of Electrolytic Precipitated Copper

To 858 g (dry weight) of electrolytic precipitated copper, 638 g (1.0 equivalent of copper relative to copper contained in electrolytic precipitated copper) of 98% concentrated sulfuric acid was added, and water was added to make the slurry amount 2.5L (slurry concentration 340 g / L). The mixture was allowed to stir for 9 hours while introducing air at 4.6 L / min. In order to raise reaction efficiency, since it is effective to make the bubble of the air to introduce | transduce fine, the jet agitator (JET AJITER made from SHIMAZAKI) was used for air introduction and stirring. In addition, liquid temperature was controlled at 80 degreeC by the water bath. ORP gradually increased with leaching, and 145 mV at the start of leaching was 270 mV at the end of leaching. The behavior of the ORP is characterized by a sharp rise near the end of the leaching, and the end point can be easily confirmed. The copper concentration at the end of the leaching is about 160 g / L, far exceeding about 50 g / L of solubility at room temperature. The leachate was left overnight at 40 ° C. without diluting the leaching solution, to precipitate a copper sulfate pentahydrate (dab). Thereafter, the leach residue and the tablet were filtered, and the mixture was divided into a sulfuric acid leaching filtration liquor and a sulfuric acid leaching residue and scavenger mixture. The sulfuric acid leaching residue and the supporting mixture were washed with about 1 L of water to remove the adhered sulfuric acid leaching liquid, and the washing water was filtered to make the filtrate the washing liquid. The filter residue was added to the sulfuric acid leaching residue / cold mixture. After washing with water, the sulfuric acid leachate and dilution mixture was dissolved in 2.5 L of water, and then separated by filtration into sulfuric acid leach residue and the liquid solution. Table 8 shows the amounts of the obtained sulfuric acid leaching filtration after liquid and sulfuric acid leaching residue.

The above operation (all operations shown in Table 8) was repeated three times, and 3 times was mixed with the sulfuric acid leaching filtration after liquid, and it was set as the raw material liquid of scorodite.

2. Synthesis of Skorodite

To 4911 mL of the above-mentioned mixture of sulfuric acid leaching filtration liquid and the plate washing liquid, 1500 mL of water and trivalent iron, 3540 mL of ferric polysulfate (hereinafter referred to as polyiron) manufactured by Nitetsu Kogyo Co., Ltd. Equivalent weight) was added. As a result of analyzing the concentration of arsenic in this mixed solution, it was in good agreement with the calculated value from the raw material at 65 g / L. Moreover, it was pH 0.21 (room temperature). Finally, 450 g (dry weight) of crystalline scorodite was added as seed crystals. Then, it heated to 95 degreeC and synthesize | combined scorodite for 48 hours. Immediately after mixing the sulfuric acid leaching solution and polyiron at room temperature, the reaction did not proceed, but precipitation of scorodite was observed about 1 hour after reaching 95 ° C with heating. After completion of the synthesis of scorodite, the scorodite crystals were suction-filtered in a Buchner funnel to separate solid-liquid. The quantity of the obtained scorodite crystal and the crystal filtration after liquid is shown in Table 9.

3. Water washing method of scorodite crystal

In Example 4, 4070 mL of water was added to 2735.1 g of scorodite (2393 g in terms of wet and dry weight) containing the seed crystals synthesized and solid-liquid separated, and the resultant was pulp and stirred for 10 minutes, followed by suction filtration with a Buchner funnel. Separated with rodite and washing solution. This operation was repeated four times. At the end of the fourth operation, it was confirmed that the arsenic of the arsenic of scorodite was 0.10 mg / L (test according to Japanese Environmental Notification No. 13), and the arsenic was stable. The scorodite obtained from this can also be said to be crystalline. The amount of water washing water per 1 kg of dry weight of scorodite was 6.8 L. The obtained scorodite was observed by SEM and it confirmed that it was in the form of a secondary particle. Moreover, the BET specific surface area (BET 1-point method) was measured using the canthasorb (QS-17) made from Yuasa Ionics, and was 11.0 m <2> / g.

Example 5

Except for changing the concentration of arsenic in the sulfuric acid leaching solution and the ferric polysulfate mixed solution (hereinafter, the solution before the reaction) during the synthesis of scorodite, the scorodite synthesized under the same conditions as in Example 1 The relationship between the amount of water washed per kg of dry weight of scorodite required to satisfy 0.3 mg / L, which is an environmental standard value, and the arsenic concentration of the solution before the reaction were investigated. Arsenic concentration of the solution before the reaction was adjusted by changing the dilution ratio after sulfuric acid leaching. The results are shown in Table 10 and FIG. 2. Moreover, as a result of observing the obtained scorodite by SEM, it confirmed that it existed in the form of a secondary particle, respectively. Moreover, as a result of measuring BET specific surface area (BET 1 point method) similarly to the above, it was all in the range of 10-20 m <2> / g.

1 is an SEM image of scorodite obtained in Example 1. FIG.

Fig. 2 is a diagram showing the relationship between the As concentration of the solution before the reaction and the amount of washing water of the obtained scorodite (Example 5).

Claims (8)

A first step of heating an acidic aqueous solution containing 19 g / L or more of pentavalent As and at least one equivalent of trivalent Fe to a temperature and time effective for synthesizing crystalline scorodite, A second step of separating the synthesized scorodite by solid-liquid separation from the solution after the reaction, Thereafter, the crystalline scoro has a BET specific surface area of at least 10 m 2 / g, which includes performing a third step of water washing the scorodite and then separating the scorodite from the water washing liquid by solid-liquid separation. Method of making a die. A first step of heating an acidic aqueous solution containing 19 to 75 g / L of pentavalent As and 1 to 1.5 equivalents of trivalent Fe to a temperature and time effective for the synthesis of crystalline scorodite, A second step of separating the synthesized scorodite by solid-liquid separation from the solution after the reaction, Thereafter, the crystallinity of the BET specific surface area of 10 to 20 m 2 / g including water washing the scorodite and then performing a third step of separating the scorodite from the water washing liquid by solid-liquid separation. Method of producing scorodite The method for producing crystalline scorodite according to claim 1 or 2, wherein the water washing of the scorodite in the third step is performed using 10 L or less water per kg of dry weight of the scorodite. The method for producing crystalline scorodite according to claim 1 or 2, wherein the third step is performed by disposing the scorodite in the filter press, supplying the washing water, and then compressing the scorodite. The washing and pressing of the third step are repeated one or more times, and the washing water supplied to the filter press every time is 1 to 10 L per kg of dry weight of scorodite. Method of producing crystalline scorodite. The concentration of pentavalent As used in the first step is 60 to 75 g / L, and the water washing of the scorodite in the third step is carried out by the dry weight 1 of the scorodite. The manufacturing method of crystalline scorodite performed using 10 L or less water per kg. The process for producing crystalline scorodite according to claim 1 or 2, wherein the resulting scorodite is in the form of secondary particles. The method for producing crystalline scorodite according to claim 1 or 2, wherein the acidic aqueous solution of the first step is prepared by adding trivalent Fe to a sulfuric acid leaching solution of electrolytic precipitated copper.

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