JP6048567B2 - Method for suppressing manganese elution - Google Patents

Description

  The present invention relates to a method for suppressing elution of manganese that suppresses elution of manganese from manganese precipitates in a slurry containing manganese precipitates.

  In recent years, high pressure acid leaching using sulfuric acid has attracted attention as a hydrometallurgical method for nickel oxide ore. Unlike the conventional dry smelting method, which is a conventional nickel oxide ore smelting method, this method does not include dry processes such as reduction and drying processes, and is a consistent wet process. Is advantageous. Further, this method has an advantage that a sulfide containing nickel and cobalt whose nickel quality is increased to about 50% by mass (hereinafter also referred to as “nickel / cobalt mixed sulfide”) can be obtained. .

  The hydrometallurgical method of nickel oxide ore using this high-pressure acid leaching method is an ore treatment step in which nickel oxide ore is pulverized to a predetermined size to form a slurry, and sulfuric acid is added to the ore slurry under high temperature and high pressure. A leaching process (high pressure acid), a pre-neutralization process for performing a neutralization (hereinafter also referred to as “pre-neutralization”) treatment before the leaching slurry is washed in multiple stages, and a pre-neutralization process. A solid-liquid separation process (hereinafter also referred to as “CCD process”) in which the leaching slurry thus obtained is subjected to solid-liquid separation into a leaching residue and a leachate containing an impurity element together with nickel and cobalt while being washed in multiple stages. A neutralization step of adjusting the pH of the leachate to separate neutralized starch containing impurity elements and obtaining a neutralized final solution containing zinc together with nickel and cobalt, and zinc by adding a sulfurizing agent to the neutralized final solution To form and separate sulfides A zinc removal step for obtaining a nickel recovery mother liquor, a nickel recovery step for forming a mixed sulfide containing nickel and cobalt by adding a sulfiding agent to the nickel recovery mother liquor, and a drain (filtrate) in the nickel recovery step And a final neutralization step in which the residue of the CCD step is mixed and neutralized (see, for example, Patent Document 1).

  The high-pressure acid leaching method has been put into practical use as a method for recovering metals from low-grade nickel oxide ores. At the time of leaching, impurity components such as manganese and magnesium are leached in the leaching slurry, in addition to elements for recovery purposes such as nickel and cobalt. The leached manganese and the like are neutralized by adding an alkali after recovering nickel and cobalt.

  In such a neutralization treatment, removal of manganese becomes a problem in many cases. This is because the content of manganese contained in the nickel oxide ore is large and difficult to precipitate. For such a problem, for example, Patent Document 2 describes a method for selectively and efficiently precipitating manganese.

  However, after neutralization treatment, that is, after precipitation of manganese, there is no useful knowledge about changes in manganese concentration during solid-liquid separation. Patent Document 3 describes a method of promoting aggregation and precipitation by adding a heavy metal inorganic compound during the neutralization treatment. However, Patent Document 3 does not mention the behavior of heavy metal concentration during solid-liquid separation after precipitation.

  Usually, the manganese concentration is controlled to a concentration that does not affect the environment. However, the manganese concentration may fluctuate rapidly, especially the concentration may increase, and the cause is unknown. This makes it difficult to control the manganese concentration. Therefore, it is required to control the manganese concentration based on knowledge about the change in manganese concentration during solid-liquid separation.

JP-A-2005-350766 JP-A-9-248576 JP 2012-250226 A

  This invention is proposed in view of such a situation, and it aims at providing the elution suppression method of manganese which suppresses that manganese elutes from a manganese deposit.

  The manganese elution suppression method according to the present invention is a manganese elution suppression method for suppressing manganese elution from manganese and aluminum precipitates and the manganese precipitate in a slurry containing nickel and cobalt. The slurry has a pH of 8.0 to 9.0, and the slurry is wastewater generated by a high-pressure acid leaching method in which nickel and cobalt are leached from nickel oxide ore. The wastewater is generated by limestone and slaked lime as a precipitant. Further, the manganese and aluminum precipitates are included, and the manganese concentration in the obtained slurry is less than 1 mg / L.

  In the present invention, the pH of the slurry containing manganese precipitates is adjusted to 8.0 to 9.0, so that elution of manganese from the manganese precipitates can be suppressed, and the supernatant obtained by precipitating the manganese precipitates The manganese concentration can be lowered.

It is a figure which shows the relationship between the manganese density | concentration and pH of the slurry stored in the sedimentation basin. It is a figure which shows the relationship of the manganese density | concentration of the slurry which removed solid content from the sedimentation tank, and the change of pH.

  Hereinafter, the method for suppressing elution of manganese according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

  The manganese elution suppression method is a method for suppressing elution of manganese from the manganese precipitate by setting the pH of the slurry containing the manganese precipitate to 8.0 to 9.0.

  As slurry, for example, the leaching residue produced when high pressure acid leaching of nickel and cobalt from nickel oxide ore and the filtrate after recovering nickel and cobalt from the leachate are neutralized with limestone powder and slaked lime powder using neutralization equipment. It is a slurry containing a precipitate produced by the sum treatment. That is, the manganese elution suppression method, for example, neutralizes leaching residue or filtrate generated by wet smelting of nickel oxide ore, and then prevents manganese elution from increasing the concentration of manganese in the effluent. Can be applied to suppress.

  Nickel oxide ore contains manganese, aluminum, and the like as impurities in addition to nickel and cobalt. For this reason, when leaching residue and filtrate are neutralized with limestone powder or slaked lime powder, precipitates such as manganese and aluminum are generated.

  When carrying out the neutralization treatment, it is preferable that the pH of the waste water containing the leach residue and the filtrate is 8.0 to 10.0. If the pH of the wastewater is too low, poor manganese precipitation occurs. If the pH is too high, the amount of neutralizing agent used is increased, which is not preferable.

  A slurry containing precipitates such as manganese and aluminum is stored for a while and precipitates such as manganese precipitates are settled. Then, after the sediment is settled, the detoxified supernatant is pumped up and discharged to the outside such as the sea or river.

  When the detoxified supernatant is released to the sea, rivers, etc. in order to control the environmental load, it is preferable that, for example, manganese precipitates as a precipitate and does not dissolve in the supernatant, but the manganese concentration in the supernatant increases. doing.

  The increase in manganese concentration is related to the pH of the slurry. The manganese concentration increases as the pH of the slurry decreases. The pH of the slurry is considered to decrease as carbon dioxide in the air dissolves and generates protons.

  Manganese elutes from the precipitate as the pH of the slurry decreases. The relationship between the pH of the slurry and the manganese concentration can also be seen from the measurement results of the pH and manganese concentration of the slurry shown in FIG.

  FIG. 1 shows the results of measuring the pH and manganese concentration of the slurry in the settling basin for about 70 days. The ultimate pH due to the dissolution of carbon dioxide is about 7.7. As shown in FIG. 1, manganese elution starts when the pH of the slurry falls below 8.5, and the manganese concentration exceeds 1 mg / L when the pH falls below 8.0. This 1 mg / L is a specified value defined by, for example, the National Pollution Control Commission (NPCC) in the Philippines. Therefore, it is necessary to suppress the manganese concentration in the slurry to less than 1 mg / L.

  Further, from the results shown in FIG. 1, the time for the slurry pH to reach 8.5 is about 20 days, and after 20 days, elution of manganese due to the decrease in pH starts abruptly, and on the 30th day, manganese elution It can be seen that the concentration of 1 mg / L.

  Therefore, the discharge is performed before the pH of the stored slurry falls below 8.0, preferably 8.25. That is, if the slurry pH is maintained within the range of 8.0 to 9.0, preferably within the range of 8.25 to 8.75, elution of manganese is suppressed, and the manganese concentration is 1 mg / L. It can be discharged in a state where the specified value of NPCC is satisfied.

  As a method for making the pH of the slurry less than 8.0, preferably less than 8.25, the slurry storage time is 30 days or less, preferably 20 days or less. When the storage time is 30 days or less, the elution of manganese is suppressed, and the manganese concentration can satisfy less than 1 mg / L.

  Here, the relationship between the decrease in pH of the slurry and carbon dioxide was separately investigated by measuring the pH of the slurry in the absence of solids (precipitate). The result is shown in FIG. Although the precipitate was removed from the slurry, not all could be removed, and a trace amount of manganese was detected.

  From the results shown in FIG. 2, even when the solid content (precipitate) is removed from the slurry and then kept in the atmosphere, the pH of the slurry may be reduced to 7.7 as in the case of containing the solid content described above. Recognize. That is, it can be seen that the pH of the slurry drops to about 7.7 when the slurry is kept in the air regardless of the presence or absence of solids. The decrease in the pH of the slurry is accelerated because there is nothing to elute if there is no solid content. Therefore, it can be seen that the decrease in the pH of the slurry is caused by the dissolution of the acidic gas contained in the air into the slurry as described above.

  In the manganese elution suppression method, the pH of the slurry is preferably 8.0 to 10.0 when the slurry is dispensed. In the manganese elution suppression method, by setting the pH of the slurry to 8.0 to 10.0, manganese is not eluted and the slurry can be released in a state where the manganese concentration is very low.

  From the above, the manganese elution suppression method can suppress an increase in manganese concentration even if the slurry before being discharged into the sea or river is stored so as to come into contact with the outside air. Thereby, the elution suppression method of manganese can suppress the influence on an environment, and the effect is very big.

  Embodiments to which the present invention is applied will be described. In addition, this invention is not limited to the following Example at all.

<Example>
In the examples, first, limestone powder and slaked lime powder are added to wastewater containing manganese produced by high pressure acid leaching for leaching nickel and cobalt from nickel oxide ore to perform neutralization treatment, and slurry containing manganese precipitates is obtained. Obtained.

  Next, in the examples, the slurry was discharged into a settling basin. The pH of the slurry when the slurry was discharged into the sedimentation basin was 9.10, and the manganese concentration was 0.3 mg / L.

  Next, in the examples, the slurry was allowed to stand for 15 days in a sedimentation basin under an air atmosphere. Thereafter, the supernatant was pumped up to the sea. The pH of the slurry at this time was 8.5, and the manganese concentration was 0.1 mg / L.

  Therefore, in the examples, the elution of manganese is suppressed.

<Comparative example>
In the comparative example, the waste water containing manganese produced by the high pressure acid leaching method was neutralized as in the example. Next, in the comparative example, the slurry was discharged into the settling basin with the slurry having a pH of 9.15.

  Next, in the comparative example, the slurry was allowed to stand for 40 days in a sedimentation basin under an air atmosphere. The manganese concentration of the slurry was 2.5 mg / L.

Claims (1)

A manganese elution suppression method for suppressing manganese elution from a manganese and aluminum precipitate, and the manganese precipitate in a slurry containing nickel and cobalt,
The pH of the slurry is 8.0 to 9.0,
The slurry is wastewater generated by a high pressure acid leaching method in which nickel and cobalt are leached from nickel oxide ore,
The drainage water contains the manganese and aluminum precipitates produced by the precipitant limestone and slaked lime,
The manganese concentration in the obtained slurry is less than 1 mg / L, The manganese elution suppression method characterized by the above-mentioned.

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