JP6241661B2 - Arsenic separation and immobilization method - Google Patents

Description

The present invention relates to a treatment method for separating and immobilizing arsenic contained in copper arsenic-containing materials such as a copper arsenide-containing slime, and more particularly, arsenic is selectively oxidized and leached to form FeAs precipitates, thereby removing arsenic. The present invention relates to a method for separating and immobilizing arsenic, which can be easily separated and concentrated, and facilitates the treatment of an FeAs precipitate.

During electrolytic refining of copper, some of the impurities such as arsenic contained in the copper anode accumulate in the electrolytic solution. Therefore, it is common to electrolyze these impurities together with copper using a part of the electrolytic solution as a cleaning treatment. It is. Copper arsenide (such as Cu ₃ As) is known as a smelting intermediate product recovered in this manner. The copper arsenide-containing slime contains, for example, 40 to 60% by mass of copper, 20 to 40% by mass of arsenic, lead, tin, antimony, bismuth and the like (each 0.5 to 5% by mass). It has been common so far to return to the copper smelting process and repeat the treatment. Alternatively, after separating arsenic and copper in a copper arsenide-containing slime, the arsenic is fixed to a stable compound and removed from the copper smelting system.

As a method for separating copper and arsenic, a treatment method is known in which arsenic is leached in the presence of sulfur and copper is precipitated as copper sulfide. For example, the following processing methods are known.
(Ii) Two or more kinds of intermediate products containing copper arsenide and intermediate products containing arsenic sulfide are made into a water-soluble slurry, an alkali agent and an oxidizing agent are added, and copper is converted into copper sulfide while selectively leaching A method of precipitation and separation from arsenic (JP 2011-212588 A).
(B) A method in which a substance containing a copper arsenic compound is made into a water slurry, and arsenic is selectively leached in the presence of an oxidizing agent and elemental sulfur (Japanese Patent Laid-Open No. 2008-150659).
(C) Slurry mixed with a substance containing a copper arsenic compound and elemental sulfur is leached in two stages, the first stage is oxidatively leached by blowing an oxidizing agent, and the second stage is boiled by SO ₂ gas and leached by leaching. Is a method of selectively leaching (JP 2012-67361 A).
(D) For a slurry in which a substance containing a copper arsenic compound and simple sulfur are mixed, arsenic is leached in an acidic region at pH 3 or lower, and further, the slurry is held at pH 2 to 4 to oxidize arsenic (III) ions, A method of precipitation and separation as acid copper (JP 2012-214839 A).

Further, a processing method is known in which arsenic and copper are separated from each other by alkaline oxidation leaching of a copper arsenic compound. For example, (e) A substance containing arsenic sulfide or copper arsenide is placed in an NaOH solution having a pH of 10 or more and an OH concentration of 100 g / L or more, heated to 90 ° C. or more, air is blown out, and alkali leaching is performed to elute arsenic. , Precipitate copper oxide. This is subjected to solid-liquid separation, and a Ca compound is added to the filtrate containing Na and arsenic to precipitate the Ca arsenic compound, and the NaOH solution is regenerated and recovered. Next, a method (Patent No. 4149488) is known in which a Ca arsenic compound is dissolved in sulfuric acid and the Ca content is precipitated into gypsum and separated.

Furthermore, a processing method is known in which arsenic and copper are separated from a copper arsenic compound by oxidative leaching of sulfuric acid. For example, (f) an intermediate containing copper arsenide as a main component is made into a sulfuric slurry, and arsenic and copper are oxidized and leached while blowing an oxygen-containing gas, and the second leaching solution containing arsenic (V) ions and copper ions is added. A method in which iron ions (Fe ⁺³ ) are added to precipitate arsenic as iron arsenate (scorodite: FeAsO ₄ .2H ₂ O) and separated from the filtrate in which copper ions remain (Patent No. 4543881, Patent No. 5050881) No.) is known.

JP 2011-212588 A JP 2008-150659 A JP 2012-67361 A JP 2012-214839 A Japanese Patent No. 4149488 (Japanese Patent Laid-Open No. 2007-314405) Japanese Patent No. 4538481 (Japanese Patent Laid-Open No. 2009-79237) Japanese Patent No. 5059081 (Japanese Patent Laid-Open No. 2010-43359)

The methods (i) to (d) above are methods for precipitation separation by converting the copper content of the copper arsenic-containing material into copper sulfide, and an arsenic (III) ion oxidation treatment (valence adjustment) is required as a post-treatment. is there. In the method (e), the copper content of the copper arsenic-containing material becomes a copper oxide residue, but the Ca arsenic compound produced by the regeneration of the NaOH solution by addition of the Ca compound is dissolved in sulfuric acid to separate Ca into gypsum. Since the process is included, the processing process is complicated. The above method (f) is an oxidative leaching with sulfuric acid, so that copper is eluted together with arsenic, but there is a problem that a part of copper ions is precipitated during the synthesis of scorodite.

The present invention provides a processing method that eliminates the above disadvantages of the conventional processing method. In the treatment method of the present invention, the copper arsenic-containing material is subjected to alkaline oxidation leaching to convert the copper content into a copper oxide residue, and ferric ions (Fe ³⁺ ) are added to the leaching solution containing arsenic to contain arsenic and iron. This is a method for producing FeAs starch. According to this method, arsenic is selectively oxidized and leached, and arsenic can be easily separated by the formation of FeAs starch, and the capacity of FeAs starch is much smaller than the original solution, so that There is little burden. Further, there is an advantage that scorodite (iron arsenate: FeAsO ₄ .2H ₂ O) can be easily produced by heat-treating this FeAs deposit into a sulfuric slurry.

According to the present invention, there is provided a method for separating and fixing arsenic having the following configuration.
[1] After leaching arsenic by adding an alkali and an oxidizing agent so that the leaching pH of the copper arsenic-containing material is 7.5 or higher, the pH of the solution is adjusted to 7.5 to 10 The FeAs starch in which arsenic was adsorbed on iron hydroxide by adding a ferric compound at a pH of 10 or lower to the arsenic leachate obtained by adjusting the copper content to a leaching residue after adjustment and solid-liquid separation. A method for separating and immobilizing arsenic, characterized by comprising:
[2] After adding sodium hydroxide solution to the copper arsenide-containing slime so that the pH is 7.5 or more at the time of leaching, and further blowing air, heating to 70 ° C. to 90 ° C. to leach arsenic, The alkaline oxidation leaching step of adjusting the pH of the liquid to 7.5 to 10 to make the copper content a residue, solid-liquid separation of the residue containing the copper content, and a solution having a pH of 10 or less containing arsenic at 50 ° C. or higher, The above-mentioned [1] including a starch production step of adding a ferric compound so that the Fe / As molar ratio is 0.9 to 1.1 and producing FeAs starch in which arsenic is adsorbed on iron hydroxide . The separation and immobilization method of arsenic described in 1.
[3] Ferric chloride, ferric sulfate, or polyferric sulfate is used as the ferric compound, and the ferric compound is added to the arsenic leachate having a pH of 7.5 to 10 at a liquid temperature of 50 ° C to 70 ° C. The method for separating and immobilizing arsenic according to [1] or [2] above, wherein an FeAs starch in which arsenic is adsorbed on iron hydroxide is added to form an FeAs starch.

[Specific description]
Processing method of the present invention, after performing oxidation leaching by adding an oxidizing agent alkali leached arsenic as pH at leach Dohiso inclusions is 7.5 or more, the pH of the liquid 7. The arsenic was adsorbed to iron hydroxide by adding a ferric compound at a pH of 10 or less to the arsenic leachate obtained by adjusting the content to 5 to 10 to separate the copper content into a leaching residue and solid-liquid separation . This is a method for separating and immobilizing arsenic, characterized in that FeAs starch is produced. A process diagram of the treatment method of the present invention is shown in FIG.

In the treatment method of the present invention, the copper arsenic-containing material to be treated is, for example, slime containing copper arsenide (Cu ₃ As, Cu ₅ As ₂ ), which is an intermetallic compound of copper and arsenic. The slime adheres to the electrode and is collected from the bottom of the electrolytic cell in the step of electrolytic collection of impurities in the copper electrolyte, and contains 20 to 40% by mass of arsenic and 40 to 60% by mass of copper as copper arsenide. An example of the XRD spectrum and peak analysis result of the copper arsenide-containing slime is shown in FIG. 2 (lower spectrum in the figure). The treatment method of the present invention is optimal as a method for separating and fixing arsenic of such copper arsenide-containing slime.

In addition, although the processing method of carrying out the alkaline oxidation leaching of arsenic sulfide (As ₂ S ₃ ) and FeAsS sulfide is known (Japanese Patent No. 4074343, Japanese Patent No. 4615661), these arsenic-containing materials are sulfur together with arsenic. And is different from the object of treatment of the present invention.

[Alkaline oxidation leaching process]
In the treatment method of the present invention, an oxidative leaching is performed by adding an alkaline solution to a copper arsenic-containing material so as to have a pH of 7.5 or higher. For example, a sodium hydroxide solution is added to a copper arsenide-containing slime to a pH of 7.5 or higher, air is further blown, and the mixture is heated to 70 ° C. to 90 ° C. to leach arsenic, and then the pH of the solution is set to 7. Adjust to 5-10 to reduce the copper concentration in the liquid as much as possible to make the copper content a residue. In addition to air, oxygen, chlorine, sodium chlorate, sodium chlorite, and sodium hypochlorite can be used as the oxidizing agent.

By this oxidative leaching, for example, as shown in the following formula, copper arsenide is oxidized in a sodium hydroxide solution, copper becomes a solid residue as copper oxide or copper hydroxide, and arsenic forms sodium arsenate. And leached into the liquid.
2Cu ₃ As + 4NaOH + 4O ₂ = 3Cu ₂ O ↓ + 2Na ₂ HAsO ₄ + H ₂ O

FIG. 3 shows the pH of oxidative leaching and the leaching state of arsenic, and FIG. 4 shows the leaching state of pH, Pb and Cu. Further, the leaching time and As concentration are shown in FIG. As shown in FIG. 3, in a region where the pH of oxidative leaching is lower than 7.5, for example, a small amount of copper ions and arsenic (V) ions react to precipitate copper arsenate (Cu ₃ (AsO ₄ ) ₂ ). As a result, the arsenic concentration in the liquid decreases (left side of FIG. 3). If sodium hydroxide is added to adjust the pH to 7.5 or more, arsenic leaching proceeds (right side of FIG. 3). Therefore, it is preferable to perform oxidative leaching by adjusting the pH to 7.5 or higher during leaching.

Further, as can be seen from the above reaction formula of oxidative leaching, 2 mol of sodium hydroxide is consumed for oxidative leaching of 1 mol of arsenic, so the amount of NaOH added is NaOH / As molar ratio = 2 times (1 equivalent) It may be adjusted based on the above. Further, when the concentration of arsenic in the raw material is clear, the required amount of sodium hydroxide may be added at the start of leaching. In this case, as shown in FIG. 4, the liquid property at the initial stage of leaching may become strong alkali (about pH 14), and heavy metal ions such as Cu and Pb are once eluted, but as the leaching reaction proceeds, Is consumed, the pH of the leachate is lowered, and the elution concentration of Cu, Pb and the like is also lowered. If the pH at the end of the leaching is in the range of 7.5 to 10, the Cu concentration and the Pb concentration are only a few ppm, so the pH at the beginning of the leaching is about 14, so that the pH is 7.5 to 10 at the end of the leaching. If it is made, the density | concentration of Cu and Pb can be suppressed, and the arsenic leaching liquid containing comparatively high purity arsenic (V) can be obtained (FIG. 4, FIG. 5).

When the pH at the end of leaching exceeds 10 due to the excessive addition of alkali at the start of oxidative leaching, the concentration of heavy metal ions such as Cu and Pb is high, and arsenic is recovered in the next FeAs starch production step. Since the rate decreases, it is preferable to adjust the pH to 10 or less by adding a neutralizing agent such as sulfuric acid or a sulfuric acid solution.
The leaching temperature is preferably 70 ° C. to 90 ° C. If the temperature is lower than the above temperature range, the leaching time becomes long. On the other hand, if it is higher than the above temperature range, the amount of steam generated is large and the heating cost is wasted.

According to the alkaline oxidation leaching, arsenic is selectively leached and the separability from coexisting metals such as Cu and Pb is good. Furthermore, the filterability of the slurry after leaching is good, and the slurry can be filtered in a short time. Moreover, the quality of copper contained in the leaching residue is as high as 80 to 85%, and the copper smelting treatment is easy.

The XRD spectrum of the leaching residue is shown in FIG. 2 (upper spectrum in the figure). As shown in the figure, the main components of the leaching residue are Cu ₂ O (Cuprite) and undissolved Cu ₃ As (Domeykite).

[FeAs precipitation generation process]
As shown in FIG. 2, copper forms copper oxide by the oxidative leaching and is contained in the residue as a solid content, and the leaching residue is subjected to solid-liquid separation. A ferric compound is added to the arsenic leachate from which the leaching residue has been separated at a pH of 10 or less to produce a FeAs starch. Specifically, as shown in the following formula, when ferric ion (Fe ³⁺ ) is added to a leachate containing arsenate ions obtained by solid-liquid separation of the leach residue, arsenic (arsenic) is added to iron (iron hydroxide). Precipitates with adsorbed acid ions are formed. Also, iron ions and arsenic ions may react to produce amorphous iron arsenate. These precipitates containing iron and arsenic are called FeAs starches.
HAsO ₄ ^2- + Fe ³⁺ + 2OH ⁻ = FeOOH (HAsO ₄ ²⁻ ) ↓ + H ⁺
HAsO ₄ ^2- + Fe ³⁺ + OH ⁻ = FeAsO ₄ ↓ + H ₂ O

When the pH of the arsenic leachate is higher than 10, it is difficult to proceed the above reaction between arsenic and iron, and arsenic remains in the liquid, which is not preferable. If the pH of the arsenic leachate is 10 or less, a FeAs starch in which arsenic is sufficiently taken in is produced. Since the pH of the arsenic leachate obtained by the alkaline oxidation leaching is 7.5 to 10, the arsenic leachate may be used in this pH range.

As the ferric compound, ferric chloride, ferric sulfate, or polyferric sulfate may be used. Of these, iron iron sulfate is desirable because of its corrosiveness and economy. As shown in the above reaction formula, since 1 mol of arsenate ion reacts with 1 mol of ferric ion, the addition amount of ferric compound is 0.9 to 1.1 mol in Fe / As molar ratio. 1 mole is preferred. If the amount of iron is less than 0.9 mol relative to arsenic, a part of the arsenic in the liquid remains unreacted in the liquid, which is not preferable. On the other hand, if the number of moles of iron relative to arsenic is greater than 1.1, the ferric compound remains unreacted and is wasted.

FIG. 6 shows changes in the amount of polyiron sulfate added to the arsenic leachate and the arsenic concentration in the liquid. Further, FIG. 7 shows changes in the amounts of precipitation of As and Fe and the pH with respect to the amount of ferric ion added. As shown in the figure, as the amount of ferric ion added increases, the pH and As concentration decrease, and the amount of FeAs starch increases.

The liquid temperature when adding the ferric compound is preferably 50 ° C or higher, and more preferably 50 ° C to 70 ° C. If the liquid temperature is lower than this, the filterability of the FeAs starch decreases. Above 70 ° C., there is no problem with arsenic sedimentation and starch filterability, but heating costs increase, which is not preferable. Since the reaction time for producing the FeAs starch is as short as 10 to 30 minutes, if the arsenic leaching solution after the oxidative leaching is quickly processed in this step, the labor of heating can be saved.

The FeAs starch is suitable as a raw material for crystalline scorodite. For example, as shown in FIG. 8, the solid-liquid separated FeAs starch is mixed with a sulfuric acid solution having a liquid temperature of 50 ° C. or higher to form a slurry or solution having a pH of 0.7 to 1.2. Crystalline scorodite (FeAsO ₄ .2H ₂ O) can be produced by heating to 90 ° C. or higher.

In the treatment method of the present invention, copper and arsenic are oxidatively leached without using sulfur in the oxidative leaching step, so that copper sulfide is not generated, and the leaching solution containing arsenic (V) ions and the residue containing copper are separated. Easy. Further, leaching of arsenic proceeds by adding an alkali and oxidizing and leaching at pH 7.5 or higher. Since alkali is consumed as the oxidation leaching reaction proceeds, the slurry pH decreases. When the initial leaching pH is 10 or more, when the oxidative leaching reaction proceeds and the pH is lowered to 10 or less, heavy metals such as Pb and Cu are converted into hydroxides and contained in the leaching residue. Can be separated.

Moreover, the treatment method of the present invention becomes a precipitate in which arsenic ions are selectively adsorbed on iron hydroxide generated by adding a ferric compound in the precipitation generation step, or an FeAs starch that forms iron arsenate. On the other hand, alkali metal ions and counter ions (for example, hydrochloric acid ions and sulfate ions) of iron ions (Fe ³⁺ ) contained in the leachate remain in the liquid, so that arsenic can be easily separated.

Arsenic is concentrated in the FeAs starch, and the capacity of the starch is 1/4 or less that of the arsenic leachate, and the capacity is much smaller, so that the processing equipment in the subsequent process can be made compact. Further, the FeAs starch is formed in a short time, the starch has good filterability, and can be easily solidified by a filter press or the like. Therefore, it is suitable for concentrating and collecting arsenic as a solid and storing it.

Furthermore, since the FeAs starch can be easily converted into scorodite by heat treatment, the treatment method of the present invention is useful as a pre-treatment step for producing scorodite. Further, since the Fe / As molar ratio in the FeAs starch is about 1, it is suitable as a raw material for scorodite. Most of the Na ions and the like in the leachate remain in the liquid and are hardly contained in the starch, so that a high-quality scorodite can be produced.

Process drawing which shows an example of the processing method of this invention. XRD spectra of copper arsenide-containing slime (lower side in the figure) and leaching residue (upper side in the figure). The graph which shows the alkali oxidation leaching time and leaching pH of a copper arsenide containing slime, and As ion concentration change. The graph which shows the relationship between alkali oxidation leaching time, Pb density | concentration, Cu density | concentration, and pH change. The graph which shows the relationship between alkali oxidation leaching time, As concentration, and NaOH concentration change. The graph which shows the relationship between the addition amount of poly ferric sulfate, an arsenic density | concentration, and pH change. The graph which shows the relationship between the addition amount of a ferric ion, the precipitation amount (upper side) of Fe and As, and pH change (lower side). Scorodite manufacturing process.

Examples of the present invention will be described below. % Is mass% unless otherwise specified.
[Example 1: Alkaline oxidation leaching]
Slurry 100 g-dry (As 20%) of copper arsenide as main component and 600 cc of water are added to a slurry, and about 15 cc of sodium hydroxide solution with a concentration of 48% by mass is added with stirring to a pH of 12 (NaOH / As molar ratio of about Adjusted to 0.5). This slurry was heated to 75 to 80 ° C., and air was introduced at a flow rate of 1 L / min for 1 hour to perform oxidative leaching. After 1 hour of leaching time, As was leached to about 7 g / L, while most of the sodium hydroxide was consumed and the slurry pH was 7.2. When the behavior of As was observed in this state, it was confirmed that the leaching reaction of As did not proceed and As ions settled (FIG. 3). Next, when sodium hydroxide was added until the slurry pH became 7.5 or more, it was confirmed that As was leached again. The color of the slurry changed from black to brown (Cu ₂ O color) as leaching progressed. At pH 7.5 or higher, stirring was stopped after 3 hours of leaching, and the slurry was filtered to recover the leachate and residue. Comparing XRD spectra of copper arsenide slime (raw material) and leaching residue, the main components of the raw material are Cu ₃ As (Domeykite) and Cu ₅ As ₂ (Koutekite), while the leaching residue contains undissolved Domeykite. And Cu ₂ O (Cuprite) were confirmed (FIG. 2). Further, as a result of analyzing the filtrate (600 cc) after leaching, pH was 8.5, As15 g / L, Cu was 2 ppm or less, and about 50% of As was leached. About 2.5 mol of sodium hydroxide was consumed per 1 mol of As.

[Example 2: Alkaline oxidation leaching]
Mix 75g-dry of slime mainly composed of copper arsenide (As about 40%) and 700cc of water, add about 45cc of sodium hydroxide solution with a concentration of 48% by mass with stirring, and adjust the molar ratio of NaOH / As to about To a pH of 14 slurry. This slurry was heated to 85 ° C., and air was introduced at a flow rate of 2 L / min for 12 hours to perform oxidative leaching. As the leaching progressed, the pH of the slurry decreased, or a decrease in the concentration of Pb and Cu leached to several hundred ppm was confirmed (FIG. 4). From the time course of the free NaOH and As concentrations shown in FIG. 5, it can be seen that the decrease in pH follows the decrease in caustic soda concentration. After 12 hours from the start of leaching, the slurry color changed from black to brown (Cu ₂ O color), where stirring was stopped and the slurry was filtered to recover the leachate and residue. As a result of analyzing the filtrate (700 cc) after leaching, pH was 9.5, As was 30 g / L, Cu was 2 ppm, Pb was 5 ppm, and about 80% of As was leached. About 2.4 mol of sodium hydroxide was consumed per 1 mol of As.

[Comparative Example 1]
Copper arsenide-containing slime 500 g-dry (content ratio: As 29%, Cu 55%, Pb 1.4%) was mixed with 2.3 L of sodium hydroxide solution (NaOH concentration 220 g / L) (solid-liquid ratio 1: 4.6). , NaOH / As molar ratio 6.5), pH 14 slurry. This slurry was heated to 52 ° C. and stirred for 150 minutes while allowing air to pass through to perform oxidative leaching. After leaching, the slurry was filtered to recover 2 L of filtrate (pH 14, As concentration 12 g / L, Cu 16 ppm, Pb 2300 ppm) and 416 g (dry) of leaching residue. As leaching rate was 17%, Cu leaching rate was 0.1% or less, and Pb leaching rate was 66%. As leaching rate was low, while leaching rate of lead was high.

[Comparative Example 2]
500 g-dry of copper arsenide-containing slime (content: As 29%, Cu 55%, Pb 1.4%) was mixed with 2.7 L of sodium hydroxide solution (NaOH concentration 180 g / L) (solid-liquid ratio 1: 5.4). , NaOH / As molar ratio 6.5), pH 14 slurry. The slurry was heated to 60 ° C. and stirred for 150 minutes while allowing air to pass through to perform oxidative leaching. After leaching, the slurry was filtered to recover 2.5 L of filtrate (pH 14, As concentration 16 g / L, Cu 10 ppm, Pb 500 ppm) and 390 g (dry) of leaching residue. The As leaching rate was 28%, the Cu leaching rate was 0.1% or less, and the Pb leaching rate was 18%. Although the As leaching rate was slightly improved as compared with Comparative Example 1, it was lower than 30%. Although the amount of Pb leaching was reduced, it was relatively high at 500 ppm.

Example 3
132 g-dry of copper arsenide-containing slime (content: As 37%, Cu 41%) was mixed with 0.9 L of sodium hydroxide solution (NaOH concentration 56 g / L) (solid-liquid ratio 1: 6.8, NaOH / As mole). A slurry with a ratio of 1.9) and pH of 14. This slurry was heated to 88 ° C. and stirred for 180 minutes while allowing air to pass through to perform oxidative leaching. A small amount of dilute sulfuric acid was added to the slurry after leaching so that the pH was 10, and 0.8 L of the filtrate (pH 10, As concentration 42 g / L, Cu 5 ppm) and 82 g (dry) of the leaching residue were collected by filtration. The As leaching rate was 69%, the Cu leaching rate was 0.1% or less, and the As leaching rate was higher than those of Comparative Examples 1 and 2.

[Example 4: FeAs precipitate formation]
The leachate prepared in Example 1 and Example 2 was mixed, 600 cc was taken from the liquid having an As concentration of 24 g / L, and heated to 60 ° C. While stirring this liquid, 58 cc of polyferric sulfate (polytetsu) manufactured by Nippon Steel & Mining Co., Ltd. was added and stirred for 10 minutes, and then about 160 g of wet starch (water content of about 70%) was suction filtered and passed through water. Washing was performed. The As residual concentration in the filtrate was 0.2 g / L, and about 99% of As was precipitated. Further, as shown in FIG. 6, the arsenic concentration and pH decrease with the addition of polytetsu. As shown in FIG. 7, the amount of iron and arsenic precipitation (number of moles) relative to the number of moles of Fe ion in the added polytetsu solution, As is about 1 mole per mole of Fe in a wide range from pH 9.2 to pH 2.3. Can be adsorbed and co-precipitated.

Claims (3)

After leaching arsenic by adding an alkali and an oxidizing agent so that the leaching pH of the copper arsenic-containing material is 7.5 or higher, the pH of the solution is adjusted to 7.5-10. Solid-liquid separation using copper as a leaching residue, and addition of a ferric compound at a pH of 10 or less to the arsenic leachate obtained by solid-liquid separation to produce FeAs starch in which arsenic is adsorbed on iron hydroxide Arsenic separation and immobilization method characterized by the above. Sodium hydroxide solution was added to the copper arsenide-containing slime so that the pH was 7.5 or more at the time of leaching, air was further blown into the lime, and the arsenic content was leached by heating to 70 ° C to 90 ° C. The alkaline oxidation leaching step for adjusting the copper content to 7.5 to 10 and making the copper content a residue, solid-liquid separation of the copper content residue, and the solution containing arsenic at a pH of 10 or less at 50 ° C. or higher and ferric iron The arsenic according to claim 1, further comprising: adding a compound such that the Fe / As molar ratio is 0.9 to 1.1 to form a FeAs starch in which arsenic is adsorbed on iron hydroxide. Separation and immobilization method. Using ferric chloride, ferric sulfate, or polyferric sulfate as the ferric compound, adding the ferric compound to the arsenic leachate with a pH of 7.5 to 10 at a liquid temperature of 50 ° C to 70 ° C, The method for separating and immobilizing arsenic according to claim 1 or 2, wherein an FeAs starch in which arsenic is adsorbed on iron hydroxide is produced.

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