JP6055606B2 - Arsenic adsorbent and arsenic immobilization method using the same - Google Patents

Description

  The present invention relates to an adsorbent for harmful substances such as arsenic synthesized from a leachate of copper heap leaching or bacterial leaching and a method for producing the same.

  In the field of copper refining, various methods for recovering copper from a processing object (hereinafter referred to as a copper-containing material) such as copper ore containing copper and copper concentrate have been implemented. For example, as a general method for recovering copper from copper sulfide ore which is one form of a copper-containing material, there is a dry processing method including the following steps.

(1) Mining process In the beneficiation process, after the copper ore mined in the mine is crushed, water is added to form a slurry, which is subjected to flotation. In this flotation, a flotation agent composed of an inhibitor, a foaming agent, a collection agent, etc. is added to the slurry, and air is blown to settle and separate the gangue while floating the minerals containing copper. I do. As a result, a copper concentrate with a copper grade of around 30% is obtained. The obtained copper concentrate is sent to the next dry smelting process.

(2) Dry smelting process In the dry smelting process, the copper concentrate obtained in the above beneficiation process is melted using a furnace such as a flash smelting furnace, and then passed through a converter and a refining furnace, and the crude copper having a copper grade of about 99%. Purify to. The obtained crude copper is cast on the anode before being sent to the next electrolysis step. In this dry smelting process, arsenic contained in the copper concentrate is distributed to slag, dust and crude copper. Slag is granulated and used as landfill, and dust is repeated in the furnace. Further, sulfur contained in the copper concentrate is separated as sulfurous acid gas and becomes a raw material of sulfuric acid.

(3) Electrolytic process In the electrolytic process, the anode is placed in an electrolytic tank filled with a sulfuric acid acid solution (electrolytic solution), and an electric current is passed between the anode and the cathode to perform electrolytic purification. By this electrolytic purification, the copper of the anode is dissolved, and then deposited on the cathode as electrolytic copper having a purity of 99.99%, resulting in a product. At this time, arsenic distributed to the anode is eluted into the electrolyte. The eluted arsenic is recovered as a copper removal slime by copper removal electrolysis. This copper removal slime is used as an intermediate raw material or is repeated in a furnace.

  In the above-mentioned dry smelting process, arsenic distributed in the slag is fixed in a stable form. However, arsenic distributed to dust and decopperized slime is in an unstable form, and it is not desirable to dispose of arsenic out of the system as it is. Therefore, these dust and copper removal slime are repeated in the furnace or processed separately. In this way, most of the arsenic content in the copper concentrate is finally distributed to the slag and fixed in a stable form.

  In addition, as another method for recovering copper from copper ore, there is a wet processing method in which copper is leached with sulfuric acid or the like, and the leached copper is concentrated by solvent extraction and recovered as a copper cathode by electrowinning. . This wet processing method is generally called a heap leaching / SX-EW method. When the copper contained in the copper ore is in the form of an oxide or carbonate, 40 to 90% of the contained copper can be easily obtained. Can be leached. That is, this method can recover copper with high yield by simple acid leaching.

Furthermore, when the copper mineral in the copper ore is a secondary sulfide mineral such as chalcocite (Cu ₂ S) or molybdenite (Cu ₅ FeS ₄ ), copper can be recovered using a bacterial leaching method. In this method, copper is efficiently leached by using a leaching solution containing iron sulfate as an oxidizing agent under the conditions in which microorganisms such as iron-oxidizing bacteria coexist.

  As described above, there are various methods for recovering copper from copper-containing materials, all of which can be recovered economically and efficiently, and are widely used in large-scale copper mines in North and South America. ing.

  By the way, in recent years, the raw material situation has changed, and the quality of impurities, particularly arsenic, in copper ore has been increasing year by year, and the quality of arsenic in the obtained copper concentrate has gradually increased. Specifically, the arsenic grade in the previous copper concentrate was about 0.1 to 0.2%, but it is not uncommon for the arsenic grade to exceed 1% in recent years. Therefore, even if the processing amount of copper concentrate is the same as before, the content of arsenic is increasing, and thus the processing to fix to the slag may not catch up. In order to solve this problem, it is conceivable to newly install or reinforce slag treatment equipment, but a great investment is required and the cost is increased.

  Therefore, as a method for fixing and stabilizing a large amount of arsenic generated in the smelting process, Patent Document 1 proposes a method of distributing air or oxygen into the residue by blowing air or oxygen into the slurry. Patent Documents 2 to 3 disclose techniques for fixing arsenic as a crystalline stable iron arsenic compound (scorodite). Furthermore, Patent Document 4 discloses a technique that uses a mineral called Schwertmannite as an arsenic adsorbent. Schwertmannite is characterized by incorporating arsenic into the crystal lattice and stabilizing, and once stabilized, it is known to exhibit anti-elution properties comparable to the scorodite.

Japanese Patent Laid-Open No. 10-140258 JP 2000-219920 A Japanese Patent Laid-Open No. 11-277075 JP 2005-058955 A

  However, in the above method, it is necessary to produce an arsenic-containing substance by chemical synthesis at a smelting site. It was a problem that it had to be disposed of by the method. In addition, since a chemical for arsenic fixation must be procured and a complicated processing process must be operated, the processing cost is also problematic.

  The object of the present invention has been made in view of the above-mentioned problems of the prior art, and is an arsenic adsorbent that efficiently adsorbs and immobilizes arsenic from a leachate of copper heap leaching or bacterial leaching or a solvent extraction residue. Another object of the present invention is to provide an arsenic immobilization method using the same.

In order to solve the above-mentioned problems, a method for producing an arsenic adsorbent provided by the present invention includes adding a solution containing Cu (II) to a solution containing Fe (II) and Fe (III), and adjusting the pH to 3-4. It is characterized by being obtained by reacting at 60 to 70 ° C., the molar concentration of Cu (II) after molarity and the added Ri der 2/3 or less of the total Fe molar concentration of the Fe (II) the Ru der least 1/10 of the molar concentration of Fe (II).

  ADVANTAGE OF THE INVENTION According to this invention, the arsenic adsorption agent which uses the process liquid of heap leaching and bacteria leaching as a raw material is provided. In addition, a method for efficiently producing the arsenic adsorbent is provided. By using the arsenic adsorbent of the present invention, it is possible to suppress the environmental impact caused by arsenic generated in the smelting process and the like, and it is possible to reduce the investment and operating cost associated with an increase in the processing load of arsenic byproducts.

It is the graph which compared the arsenic adsorption capability of the adsorption agent of Reference Examples 1-2 and Comparative Examples 1-2. It is a graph which shows the X-ray-diffraction analysis result of the adsorption agent of Reference Examples 1-2 and Comparative Examples 1-2. It is the graph which compared the arsenic adsorption ability of the adsorbent of Examples 1-2, the reference example 1, and the comparative example 2. FIG. It is a graph which shows the X-ray-diffraction analysis result of the adsorbent of Examples 1-2, the reference example 1, and the comparative example 2. FIG.

  The arsenic adsorbent of the present invention is a solution obtained from a leaching / SX (solvent extraction) process, specifically, a leachable noble liquid repeatedly used in copper heap leaching or bacterial leaching or its solvent extraction residual liquid, It is manufactured by the method. That is, the temperature of the leachate of leaching as a raw material solution or the temperature of the extraction residual liquid after the solvent extraction step is set to 60 to 70 ° C. To adjust the pH to 3 to 4 for reaction.

  At this time, it is preferable to use a solution in which the ratio of the molar concentration of Fe (II) to the total Fe molar concentration is 0 to 2/3, more preferably 1/100 to 1/10. Furthermore, it is preferable that Cu (II) is contained in the raw material solution at a molar concentration of 1/10 or more of the molar concentration of Fe (II). And the deposit produced | generated by this reaction is collect | recovered by solid-liquid separation methods, such as filtration, and it is set as an arsenic adsorption agent. By bringing a solution containing arsenic into contact with the obtained arsenic adsorbent, arsenic in the solution can be immobilized as an iron arsenic compound.

  The raw material solution used as the starting material for the arsenic adsorbent is not particularly limited to the copper mine or leaching method from which it is derived. The leaching noble liquid and the solvent extraction residual liquid contain iron (Fe) eluted from the ore, and this becomes a raw material for the arsenic adsorbent, so that the concentration is preferably higher. Usually, the iron concentration of the raw material solution is 0.1 to 5 g / L and the pH is 1 to 3. This raw material solution is heated to 60 to 70 ° C. in a reaction vessel, and a sodium carbonate solution having a predetermined concentration is dropped to carry out the reaction by gradually raising the pH.

  According to the study by the inventors, the concentration of the sodium carbonate solution was 1 M, and the dropping rate was optimally 1 to 2 ml / min with respect to 1 L of the raw material solution. By this operation, a precipitate mainly composed of Schwertmannite is generated from the raw material solution. Therefore, the precipitate is collected by a general solid-liquid separation device such as a filtration method or a centrifugal separation method, dried, and dried with an arsenic adsorbent. To do.

  According to the study by the inventors, in order to efficiently produce an arsenic adsorbent, the iron in the raw material solution is desirably in the form of Fe (III), and the ratio of Fe (II) to the total Fe is 0 to 2% is suitable. This is because when the ratio of Fe (II) exceeds this upper limit, goethite having a low arsenic adsorption ability is precipitated and mixed into the product. The inventors have further researched on this, and when the concentration of Fe (II) exceeds the above upper limit, specifically, even if the concentration of Fe (II) is 2/3 of the total Fe concentration, The coexistence of Cu (II) so that the molar concentration of Cu (II) is 1/10 or more of the molar concentration of Fe (II) is not clear, but the formation of goethite is suppressed and the purity is high. It has been found that Schwertmannite can be produced.

  Normally, heap leaching and bacterial leaching in copper mines produce leaching noble liquids with various Fe and Cu concentrations depending on the location. Therefore, leaching noble liquids that meet the above conditions can be collected or leaching with different compositions. What is necessary is just to mix a noble liquid suitably and match said conditions, and let this be a starting material. In addition, the remaining extraction residual liquid which collect | recovered copper by solvent extraction from the leaching noble liquid can also be used similarly for the raw material solution of the said arsenic adsorbent.

  The form of the reaction tank used in the above method is not particularly limited. For example, a general stirring tank equipped with a stirrer having an appropriate shape so that the dropped sodium carbonate solution is uniformly mixed should be used. Can do. The dropping method and the apparatus are not particularly limited. What is necessary is just to use a commercially available vacuum filtration apparatus and a centrifuge for said solid-liquid separation apparatus. The drying method of solid content obtained by solid-liquid separation is not particularly limited, and a commercially available vacuum dryer or constant temperature dryer may be used. In addition, when the arsenic adsorbent is used in a manufacturer's mine, etc., if it is not necessary to transport over a long distance, it can be used in the form of a dehydrated cake without being dried.

  The method for immobilizing arsenic in the arsenic-containing solution using the obtained arsenic adsorbent is not particularly limited. For example, the solution containing arsenic is passed through a tank or packed tower filled with the arsenic adsorbent. Thus, the arsenic-containing solution and the arsenic adsorbent may be brought into contact with each other, thereby fixing the arsenic in the solution as an iron arsenic compound.

  As explained above, an arsenic adsorbent can be easily prepared by adjusting the Fe concentration and Cu concentration of the leaching noble liquid and solvent extraction residual liquid and reacting at a predetermined pH and temperature, and further obtained. Arsenic can be easily removed from an arsenic-containing solution using an arsenic adsorbent. Therefore, the environmental impact of arsenic can be suppressed at a very low cost.

  Moreover, in general heap leaching and bacterial leaching, a large amount of iron sulfate is contained in the leachate due to dissolution of pyrite and pyrite containing iron. The iron content in the leachate remains in the extraction residual liquid when copper is recovered in the solvent extraction process, and is repeated in the leaching process as a component of the leachate. If the number of repetitions increases, excess iron sulfate precipitates in the heap in the form of jarosite or the like, so that it has conventionally been discarded as useless. On the other hand, the present invention can effectively use the iron content in the leachate as an arsenic adsorbent.

  The present invention will be described in more detail with reference to the following examples, reference examples and comparative examples, but the present invention is not limited to these examples. In the following examples, for simplification and reproducibility of experiments, a simulated solution in which the composition of a solution extracted from general heap leaching or bacterial leaching was reproduced with a reagent was used. In the following examples, the chemical analysis values were determined using ICP emission spectrometry and atomic absorption spectroscopy.

[Reference Example 1]
In Reference Example 1, a solution containing 50 mM Fe ₂ (SO ₄ ) ₃ and 10 mM H ₂ SO ₄ was used as a pseudo solution. This simulated liquid 1 dm ³ was placed in a beaker and heated to 65.5 ° C. while stirring with a hot stirrer. While maintaining the liquid temperature, a 1M Na ₂ CO ₃ solution was dropped into the simulated liquid in the beaker at a rate of 1.5 mL / min, and the dropping was terminated when the pH of the simulated liquid reached 3.5. The produced precipitate was filtered using 5A filter paper, dried overnight in a vacuum dryer, and then crushed in an agate mortar to obtain an adsorbent.

In order to confirm the arsenic adsorption ability of the adsorbent, an adsorption test was carried out by adjusting a 1 mM H ₂ SO ₄ solution containing Na ₂ HAsO ₄ .7H ₂ O at a predetermined concentration. As a result, the adsorbent synthesized as shown in FIG. 1 had an arsenic adsorption capacity of 1.5 mmol / g.

[Reference Example 2]
An adsorbent was synthesized in the same manner as in Reference Example 1 except that a simulated solution containing 50 mM Fe ₂ (SO ₄ ) ₃ , 1 mM Fe (SO ₄ ), and 10 mM H ₂ SO ₄ was used. The adsorption experiment was conducted using an arsenic solution in the same manner as described above. As a result, as shown in FIG. 1, the arsenic adsorption ability was the same as in Reference Example 1.

[Example 1]
Adsorption in the same manner as in Reference Example 1 except that a simulated solution containing 50 mM Fe ₂ (SO ₄ ) ₃ , 100 mM Fe (SO ₄ ), 10 mM Cu (SO ₄ ), and 10 mM H ₂ SO ₄ was used. The agent was synthesized, and an adsorption experiment was performed using an arsenic solution in the same manner as in Reference Example 1. As a result, as shown in FIG. 3, the arsenic adsorption ability was the same as in Reference Example 1.

[Example 2]
Adsorption in the same manner as Reference Example 1 except that a simulated solution containing 50 mM Fe ₂ (SO ₄ ) ₃ , 100 mM Fe (SO ₄ ), 100 mM Cu (SO ₄ ), and 10 mM H ₂ SO ₄ was used. The agent was synthesized, and an adsorption experiment was performed using an arsenic solution in the same manner as in Reference Example 1. As a result, as shown in FIG. 3, the arsenic adsorption ability was the same as in Reference Example 1.

[Comparative Examples 1-2]
In Comparative Example 1, a simulated solution containing 50 mM Fe ₂ (SO ₄ ) ₃ , 10 mM Fe (SO ₄ ) and 10 mM H ₂ SO ₄ , and in Comparative Example 2, 50 mM Fe ₂ (SO ₄ ) ₃ and 100 mM Adsorbents were synthesized in the same manner as in Reference Example 1 except that a pseudo solution containing Fe (SO ₄ ) and 10 mM H ₂ SO ₄ was used, and adsorbed using an arsenic solution as in Reference Example 1. The experiment was conducted. As a result, as shown in FIG. 1, in the case of Comparative Example 1, the arsenic adsorption ability decreased in the region where the arsenic concentration was 1.0 mM or less compared to Reference Examples 1 and 2. In Comparative Example 2, the saturated adsorption amount was significantly reduced as compared with Reference Examples 1 and 2.

  FIG. 2 shows the results of X-ray diffraction analysis of the adsorbents synthesized in Reference Examples 1-2 and Comparative Examples 1-2. In the comparative example, a goethite peak appears in addition to the peak of Schwertmannite, and it is clear that the formation of goethite is the cause of the arsenic adsorption ability.

  In FIG. 4, the X-ray-diffraction analysis result of the adsorption agent synthesize | combined in Examples 1-2, the reference example 1, and the comparative example 2 is shown. In Examples 1 and 2, the peak of goethite is small despite the fact that Fe (II) is 100 mM as in Comparative Example 2, and the formation of goethite is suppressed by the coexistence of Cu (II). It can be seen that is preferentially generated.

Claims (3)

Production of an arsenic adsorbent characterized by being obtained by adding a solution containing Cu (II) to a solution containing Fe (II) and Fe (III) and reacting at a pH of 3 to 4 and a temperature of 60 to 70 ° C. The molar concentration of Fe (II) is 2/3 or less of the total Fe molar concentration, and the molar concentration of Cu (II) after the addition is 1/10 or more of the molar concentration of Fe (II). A method for producing an arsenic adsorbent, characterized in that The method for producing an arsenic adsorbent according to claim 1, wherein the solution containing Fe (II) and Fe (III) is a solution obtained from a leaching / SX process. A solution containing Cu (II) is added to a solution containing Fe (II) and Fe (III) and reacted at a pH of 3 to 4 and a temperature of 60 to 70 ° C., and a solution containing arsenic in the resulting precipitate is obtained. A method for immobilizing arsenic, wherein arsenic in the solution is immobilized as an iron arsenic compound by contacting, wherein the molar concentration of Fe (II) is 2/3 or less of the total Fe molar concentration and after the addition A method for immobilizing arsenic, wherein the molar concentration of Cu (II) is 1/10 or more of the molar concentration of Fe (II).

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