JP7147362B2 - Method for reducing odor in hydrometallurgy of nickel oxide ore - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for reducing odors generated in the final neutralization step of hydrometallurgy of nickel oxide ore, and more particularly to a method for reducing odors caused by dissolved sulfiding agents.

As a hydrometallurgical method for nickel oxide ores, a hydrometallurgical process including a high-pressure acid leaching treatment using sulfuric acid is known. This process is different from the conventional pyrometallurgical method, which is a conventional method of smelting nickel oxide ore, and is a mixed sulfide containing nickel and cobalt with nickel grade increased from low-grade nickel oxide ore to 50 to 60% by mass. (hereinafter also referred to as nickel-cobalt mixed sulfide) can be efficiently produced, and the treatment is performed in a consistent wet process without including a reduction process or a drying process, so it is an energy- and cost-effective process. be.

The hydrometallurgical process including the high-pressure acid leaching treatment includes a step of adding sulfuric acid to nickel oxide ore slurry and leaching under high temperature and high pressure, and washing the leached slurry obtained in the leaching step in multiple stages. A solid-liquid separation step of separating the leachate containing impurity elements together with nickel and cobalt from the leach residue, and adjusting the pH of the leach solution and adding a part of the leach residue and a coagulant to remove the impurity elements. a neutralization step of separating and removing precipitates after the precipitation to obtain a final neutralization solution containing nickel and cobalt; and mixing containing zinc and copper by adding hydrogen sulfide gas to the final neutralization solution. After producing sulfide, a dezincing step of separating and removing it to obtain a dezincing final solution, and adding hydrogen sulfide gas to the dezincing final solution to produce a nickel-cobalt mixed sulfide, A process consisting of a nickel recovery step in which nickel is recovered by solid-liquid separation is known.

In the nickel recovery step, it is preferable to add a large amount of hydrogen sulfide gas in order to increase the nickel recovery rate. can be reduced. However, in this case, the amount of dissolved hydrogen sulfide gas remaining in the nickel recovery final solution increases, and in the final neutralization step of processing the nickel recovery final solution, for example, the gas in the gas phase part of the neutralization reaction tank is sucked. It has been a problem that a large amount of odorous gas is generated from the washing tower that is used for washing.

In the above hydrometallurgical process of nickel oxide ore, various techniques have been proposed for removing hydrogen sulfide dissolved in the solution, which causes odor. For example, in Patent Document 1, a trivalent iron compound is added to a solution containing hydrogen sulfide, and hydrogen sulfide and 3 A method is disclosed for fixing hydrogen sulfide dissolved in a solution in the form of sulfur by reacting valence iron.

JP 2004-089915 A

However, the technique of Patent Document 1 is shown to use iron hydroxide, which is a waste product discharged from the hydrometallurgical process, as the trivalent iron compound, which is discharged from the high pressure acid leaching process. An alkali such as limestone or slaked lime is added to the leaching residue in the final neutralization step, and the resulting neutralized precipitate containing trivalent iron hydroxide is used to fix hydrogen sulfide. Therefore, this neutralized sediment contains many impurities such as aluminum and magnesium.

When the neutralized precipitate containing a large amount of such impurities is used as it is, the aluminum and magnesium precipitates in the neutralized precipitate are also dissolved, requiring a correspondingly large amount of sulfuric acid. Furthermore, it is necessary to send the solution from which the dissolved hydrogen sulfide has been removed again to the final neutralization step to precipitate aluminum and magnesium with a neutralizing agent. As described above, in the technique of Patent Document 1, the neutralization and dissolution of impurities are repeated as a result, so the consumption of sulfuric acid and the neutralizing agent rather increases, which may pose a problem of high processing costs. rice field.

The present invention has been made in view of the above-described problems of the conventional nickel oxide ore hydrometallurgical process, and sulfuric acid or neutralization To provide an odor reduction method capable of efficiently removing a sulfiding agent dissolved in the nickel recovery final solution without increasing the consumption of chemicals such as agents, thereby reducing the odor generated in the final neutralization step. It is intended to

In order to achieve the above object, the method for reducing odor according to the present invention is a hydrometallurgical method for producing a nickel-cobalt mixed sulfide by adding a sulfiding agent to a leachate obtained by high-pressure acid leaching of nickel oxide ore containing cobalt. A method for reducing the odor generated when neutralizing the nickel recovery final solution discharged during solid-liquid separation of the mixed sulfide in the process, wherein air is blown into the nickel recovery final solution and the The pH is adjusted to 2.0 or less, and an oxidizing slurry containing 1 to 30% by mass of trivalent iron residue is added to the nickel recovery final solution at a flow rate of 0.025 or more to reduce sulfur. It is characterized in that the oxidizing slurry is obtained by neutralizing the poor liquid obtained after the oxidation treatment of the nickel recovery final solution .

According to the present invention, the nickel recovery final solution discharged during solid-liquid separation of nickel-cobalt mixed sulfide can be recovered without increasing the consumption of chemicals such as sulfuric acid and neutralizing agents. The sulfurizing agent dissolved in the final solution can be removed efficiently.

1 is a process flow diagram of a nickel oxide ore hydrometallurgical process including an embodiment of the odor reduction method of the present invention; FIG. It is a graph which shows the relationship between the flow rate ratio of waste water slurry with respect to nickel recovery final liquid, and the odor index in the final neutralization process.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for reducing odors generated in the final neutralization step of a nickel oxide ore hydrometallurgical process according to the present invention will be described below in detail with reference to the drawings. In this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less" unless otherwise specified. An odor reduction method according to an embodiment of the present invention includes a leaching step of obtaining a leachate by subjecting nickel oxide ore containing cobalt to a sulfuric acid leaching treatment at high temperature and high pressure, and adding a sulfiding agent to the leachate. In a hydrometallurgy process having a nickel recovery step of recovering a mixed sulfide of nickel-cobalt mixed sulfide by solid-liquid separation, when neutralizing the final nickel recovery liquid discharged during solid-liquid separation of the mixed sulfide wherein air is blown into the nickel recovery final solution, the pH is adjusted to 2.0 or less, and the trivalent iron residue is 1 to 30% by mass. Slurry is added to the nickel recovery final solution at a flow rate ratio of 0.025 or more to oxidize reducing sulfur compounds.

Hereinafter, the nickel oxide ore hydrometallurgical process (hereinafter also simply referred to as the “hydrometallurgical process”) including the odor reduction method of the embodiment of the present invention will be described with reference to the high pressure acid leaching process (HPAL: High Pressure) shown in FIG. The hydrometallurgical process including the Acid Leach process will be described in detail as an example. The hydrometallurgical process shown in FIG. 1 includes a leaching step S1 in which sulfuric acid is added to slurry of nickel oxide ore as a raw material and subjected to leaching treatment under high temperature and high pressure, and the leaching slurry obtained in the leaching step S1 is neutralized. A preliminary neutralization step S2 in which an agent is added to adjust the pH to within a predetermined range, and the leaching slurry whose pH has been adjusted in the preliminary neutralization step S2 is washed in multiple stages to remove the leaching solution containing impurity elements together with nickel and cobalt and remove the leaching residue. A solid-liquid separation step S3 in which a pH adjuster is added to the leachate to generate a neutralized sediment containing impurity elements, which is separated and removed to obtain a final neutralization solution containing zinc together with nickel and cobalt. and a dezincing step S5 in which zinc sulfide is produced by adding a sulfiding agent to the final neutralization solution and separated and removed to obtain a nickel recovery mother liquor containing nickel and cobalt. a nickel recovery step S6 in which a mixed sulfide containing nickel and cobalt is generated by adding a sulfiding agent to the nickel recovery mother liquor, and then the mixed sulfide is solid-liquid separated from the nickel recovery final solution; Air is blown into the nickel recovery final solution discharged from step S6, the pH is adjusted to 2.0 or less, and a predetermined amount of oxidizing slurry containing a predetermined amount of trivalent iron residue is added to decompose the sulfiding agent. and a final neutralization step S8 for detoxifying the poor liquid discharged by the treatment in the sulfurizing agent removal step S7 together with the leaching residue discharged from the solid-liquid separation step S3. ing. Each of these steps will be described below.

(1) Leaching Step In the leaching step S1, nickel oxide ore as a raw material is pulverized to a predetermined particle size, and water is added to adjust the ore slurry to a predetermined slurry concentration. The ore slurry is subjected to a high pressure acid leaching treatment under high temperature and high pressure conditions of 3 to 4.5 MPaG and 220 to 280° C. with stirring to produce a leaching slurry consisting of a leaching solution and a leaching residue.

The nickel oxide ore processed in this leaching step S1 is mainly so-called laterite ore such as limonite ore and saprolite ore. The nickel content of laterite ores is generally 0.8 to 2.5% by weight and is present as hydroxide or magnesium silicate (magnesium silicate) minerals. This nickel oxide ore has an iron content of 10 to 50% by mass, which is mainly in the form of trivalent hydroxide (goethite), and partly divalent iron is contained in minerals. In addition to the laterite ore described above, oxide ores such as manganese nodules present in the deep sea floor containing valuable metals such as nickel, cobalt, manganese, and copper may be used as raw materials for the leaching step S1.

In the high-pressure acid leaching treatment in the leaching step S1, leaching reactions represented by the following formulas 1 to 3 and high-temperature thermal hydrolysis reactions represented by the following formulas 4 and 5 occur, and nickel, cobalt, etc. are leached as sulfates. Then, the leached iron sulfate is fixed as hematite. However, since iron ions do not completely immobilize, the liquid portion of the obtained leaching slurry usually contains divalent and trivalent iron ions in addition to nickel, cobalt, and the like.

[Formula 1]
MO+ _H2SO4 → _{MSO4 + H2O}
(M in the formula represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn, etc.)
[Formula 2]
2Fe(OH) ₃ + _3H2SO4 →Fe2 _{( SO4} ) _{3 + 6H2O}
[Formula 3]
_FeO +H2SO4→ _{FeSO4 + H2O}
[Formula 4]
_2FeSO4 +H2SO4+ ₁ / _2O2 →Fe2 _{( SO4} ) _{3 + H2O}
[Formula 5]
Fe2 _{( SO4} ) _{3 + 3H2O} → _{Fe2O3 + 3H2SO4}

The amount of sulfuric acid to be added to the autoclave in the leaching step S1 is not particularly limited, but it is preferable to add an excess amount of sulfuric acid so that the iron in the ore of the raw material is leached. In the leaching step S1, the pH of the leaching solution should be adjusted to 0.1 to 1.0 so that the produced leaching residue containing hematite does not reduce filterability in the subsequent solid-liquid separation step S3. is preferred.

(2) Preliminary Neutralization Step In the preliminary neutralization step S2, the pH of the leached slurry obtained in the leaching step S1 is adjusted to a predetermined range. That is, in the high-pressure acid leaching treatment in the leaching step S1, excess sulfuric acid is added from the viewpoint of improving the leaching rate. Sulfuric acid (hereinafter also referred to as free sulfuric acid) is included, and its pH is very low. Therefore, in the preliminary neutralization step S2, the pH of the leaching slurry is preferably adjusted within a range of about 2 to 6 so that washing can be efficiently performed in the multistage washing in the subsequent solid-liquid separation step S3.

If the pH of the leaching slurry is lower than 2, it is not preferable because the cost of countermeasures against corrosion of the wetted parts of the equipment in the subsequent process will be considerable. Conversely, if the pH of the leaching slurry is higher than 6, the nickel leached into the leaching solution (slurry) precipitates during the cleaning process and precipitates as a residue, which is not preferable because there is a risk of lowering the cleaning efficiency. Although the method for adjusting the pH is not particularly limited, it can be preferably adjusted by adding a neutralizing agent such as calcium carbonate in the form of slurry.

(3) Solid-Liquid Separation Step In the solid-liquid separation step S3, the leached slurry pH-adjusted in the preliminary neutralization step S2 is mixed with a washing liquid, and a flocculating agent is supplied while washing with sedimentation separation equipment such as a thickener. The leaching residue is separated using a preferably anionic flocculant supplied from equipment or the like. As a result, a leachate (crude nickel sulfate aqueous solution) containing impurity elements such as zinc in addition to nickel and cobalt is obtained. When the thickener is used as described above, the leaching residue in the leaching slurry is concentrated as sediment, and at this time, the amount of nickel adhering to the leaching residue can be reduced depending on the degree of dilution of the leaching slurry with the cleaning liquid. . The leaching residue extracted from the thickener is neutralized in the final neutralization step S8 to be described later to remove heavy metals, and then transferred to the tailing dam.

In this solid-liquid separation step S3, a plurality of thickeners are connected in series. It is preferable to wash the leached slurry in multiple stages by a continuous countercurrent washing method (CCD method: Counter Current Decantation) in which the washing liquid is introduced into the adjacent thickeners and the supernatant liquid is transferred to the adjacent thickeners in the previous stage by overflow. As a result, it becomes possible to ensure a nickel and cobalt recovery rate of 95% or more while suppressing the amount of the cleaning liquid newly introduced into the system to a small amount.

Although the type of the cleaning liquid is not particularly limited, it is preferable to use one that does not contain nickel and does not adversely affect the leaching slurry during the solid-liquid separation step. In particular, it is preferable to use an aqueous solution having a pH of 1 to 3 as the cleaning liquid. This is because if the pH of the cleaning solution is higher than 3, aluminum hydroxide with high bulk will be produced if the leach solution contains aluminum, which may deteriorate the sedimentation property of the leach residue. Such a cleaning liquid having a pH of about 1 to 3 may be a low pH nickel recovery end liquid discharged as a liquid phase during recovery by solid-liquid separation of the mixed sulfide in the subsequent nickel recovery step S6, or a sulfiding agent. Since the poor liquid after being treated in the removing step S7 is suitable, it is preferable to use it repeatedly.

(4) Neutralization step In the neutralization step S4, a neutralizing agent such as calcium carbonate is added to the leachate, which is the crude nickel sulfate aqueous solution separated from the leach residue in the solid-liquid separation step S3, to adjust the pH. It produces neutralized sediment containing impurity elements while suppressing oxidation of the leachate. By removing this neutralized sediment by solid-liquid separation, a final neutralization solution, which is the source of a mother liquor for recovering nickel, containing impurity elements mainly composed of zinc together with nickel and cobalt, is obtained. In the neutralization step S4, the pH is preferably adjusted so that the final neutralization solution has a pH of 4 or less, preferably 3.0 to 3.5, more preferably 3.1 to 3.2. As a result, mainly trivalent iron ions and aluminum ions remaining in the leachate can be removed as neutralized precipitates.

(5) Dezincification step In the dezincification step S5, for example, the final neutralization solution obtained in the neutralization step S4 is introduced into a pressurized container, and hydrogen sulfide gas is blown into the gas phase of the container. A sulfidation treatment is provided by the addition of a sulfiding agent, which selectively sulfides zinc relative to nickel and cobalt to form zinc sulfide. By separating and removing this zinc sulfide, a nickel recovery mother liquor (final dezincing liquor) composed of a sulfuric acid solution containing nickel and cobalt is obtained. Incidentally, this mother liquor for recovering nickel usually contains iron, magnesium, manganese and the like as impurity components in the order of several g/L each.

(6) Nickel recovery step In the nickel recovery step S6, a sulfiding agent such as hydrogen sulfide gas is blown into the nickel recovery mother liquor, thereby causing a sulfurization reaction to produce a sulfide containing nickel and cobalt (nickel-cobalt mixed sulfide things). This nickel-cobalt mixed sulfide is recovered by solid-liquid separation such as filtration, and at that time, the end of nickel recovery is discharged to the liquid phase side. As described above, the nickel recovery mother liquor treated in the nickel recovery step S6 may contain impurities such as Fe, Mg, and Mn. is low in stability, so it is hardly contained in the nickel-cobalt mixed sulfide.

(7) Sulfurizing agent removal step Since the sulfiding agent such as hydrogen sulfide added in the dezincing step S5 and the nickel recovery step S6 is dissolved in the nickel recovery final solution, the sulfiding agent removal step S7 is the end of nickel recovery. Air is blown into the liquid, and an oxidizing slurry containing trivalent iron residue produced in the final neutralization step S8 described later is added to remove sulfide contained in the nickel recovery final liquid under the condition of pH 2.0 or less. Reducing sulfur compounds such as dissolved hydrogen sulfide resulting from the agent are fixed as sulfur and removed. It is preferable that the blowing amount of the air is 1.8 Nm ³ or more per 1 m ³ of the nickel recovery final solution. This can promote the oxidation of dissolved sulfur compounds such as hydrogen sulfide.

Note that "immobilization" means converting a compound into a stable form, and by using the oxidizing slurry in the sulfurizing agent removing step S7, sulfur compounds such as hydrogen sulfide dissolved in the final nickel recovery solution However, by the reactions shown in Reaction Formulas 6 and 7 below, sulfur (S) changes into a stable form of elemental sulfur (S) and precipitates. This elemental sulfur is removed in the form of a solid content by solid-liquid separation, and a poor liquid is discharged from the liquid phase side of the solid-liquid separation. Reaction formulas 6 and 7 below are examples when hydrogen sulfide gas is used as the sulfurizing agent.
[Formula 6]
2Fe(OH) ₃ + _3H2SO4 →Fe2 _{( SO4} ) _{3 + 6H2O}
[Formula 7]
Fe2 _{( SO4} ) _{3 + H2S} → _FeSO4 + _{S0 +} H2SO4

The poor liquid discharged from the sulfiding agent removing step S7 is neutralized in the final neutralization step S8 as described later, thereby precipitating iron contained in the poor liquid as iron hydroxide. A portion of the residual slurry containing the neutralized sediment composed of iron hydroxide and the hematite produced in the leaching step S1 is extracted and treated as an oxidizing slurry having a source of trivalent iron ions in the sulfiding agent removing step as described above. Used in S7. Since free sulfuric acid is contained in the nickel recovery final solution, there is no need to add the sulfuric acid shown in the above equation 6 separately or only a small amount can be added, so the consumption of sulfuric acid can be reduced. The residual slurry after the partial extraction is discharged to the tailing dam.

Although the above trivalent iron hydroxide (Fe(OH) ₃ ) is a compound that is difficult to dissolve, if the pH of the nickel recovery final solution is 2.0 or less, the reaction of the above formula 6 with free sulfuric acid proceeds. The redox reaction of Equation 7 is promoted. On the other hand, if the pH of the nickel recovery final solution exceeds 2.0, the amount of trivalent iron hydroxide (Fe(OH) ₃ ) dissolved decreases, so the supply of trivalent iron is insufficient and dissolved. Immobilization of a sulfurizing agent comprising a sulfur compound such as hydrogen sulfide becomes insufficient. In addition, this pH adjustment can be adjusted by adding sulfuric acid or adding calcium carbonate, for example.

The oxidizing slurry should contain 1 to 30% by mass of trivalent iron residue. If this content is less than 1% by mass, the supply of trivalent iron is insufficient and the immobilization of dissolved sulfur compounds such as hydrogen sulfide becomes insufficient. Conversely, if the content exceeds 30% by mass, the concentration of solids in the oxidizing slurry becomes too high, and there is a risk that the piping system will be clogged or damage due to friction will occur during liquid transfer. The content of this iron residue can be measured, for example, with a hydrometer, and the slurry specific gravity of the oxidizing slurry is continuously monitored with this hydrometer, and when it exceeds 30% by mass, water is added to dilute the oxidizing slurry. Just do it. On the other hand, if it is less than 1% by mass, solid-liquid separation may be performed for concentration. The trivalent iron residue mainly consists of trivalent iron hydroxide and also contains iron sulfate and hematite.

The oxidizing slurry in which the trivalent iron residue content is adjusted as described above is added to the nickel recovery final solution at a flow rate of 0.025 or more on a volume basis. If the flow rate ratio is less than 0.025, the reaction for fixing the sulfur compounds caused by the sulfurizing agent is insufficient, and a large amount of dissolved sulfur compounds such as hydrogen sulfide remain in the poor liquid. put away. The upper limit of the flow rate ratio is not particularly limited, but is preferably 0.055, more preferably 0.045. This is because even if the flow rate ratio exceeds 0.055, the immobilization reaction will not improve any more, and the operating cost will rather increase, which is not preferable.

As described above, the oxidizing slurry containing 1 to 30% by mass of trivalent iron residue is mixed with the nickel recovery final solution at a flow rate ratio of 0.025 or more and reacted, so that the final neutralization described later The odor generated in step S8 can be reduced. That is, in addition to sulfur compounds such as hydrogen sulfide gas dissolved in the nickel recovery final solution, the odors generated in the final neutralization step S8 are caused by the solid-liquid separation step S3, the neutralization step S4, and the nickel recovery step S6. Organic substances such as coagulants to be added, metabolites of microorganisms present in the system, and the like can be mentioned.

Since all of these odor factors can be decomposed by adding an oxidizing agent, the odor can be eliminated by using an oxidizing slurry containing 1 to 30% by mass of trivalent iron residue as an oxidizing agent as described above. can be effectively reduced. Although iron (III) sulfate can be used as the oxidizing agent, it is disadvantageous in terms of costs such as investment in equipment for it and purchase of raw materials for its production. On the other hand, in the odor reduction method of the embodiment of the present invention, the iron compound generated in the system can be used, so the odor can be reduced at a relatively low cost.

(8) Final neutralization step Since the poor liquid obtained by the treatment in the sulfiding agent removal step S7 may contain impurity components such as magnesium, manganese, and aluminum in addition to iron, the poor liquid is used in the final neutralization step S8. Then, the leach residue slurry discharged from the solid-liquid separation step S3 is subjected to a neutralization treatment (detoxification treatment) in which a neutralizing agent such as limestone is added to adjust the pH to a predetermined range. As a result, iron hydroxide is precipitated from the trivalent iron contained in the poor liquid and the leaching residue slurry. The obtained slurry containing trivalent iron hydroxide is subjected to solid-liquid separation or the like as necessary to adjust the slurry concentration, so that the trivalent iron residue used in the sulfiding agent removal step S7 is reduced to 1 Oxidizing slurries containing up to 30% by mass can be prepared. In this final neutralization step S8, impurity components such as magnesium, manganese, and aluminum are also removed by the above-described detoxification treatment until the emission standards are met, and a final wastewater solution that can be discharged outside the system is obtained.

The method of detoxification by the neutralization treatment is not particularly limited, but for example, a first final neutralization treatment step of adding a first neutralizing agent such as limestone and performing neutralization treatment at pH 5 to 6; A two-stage treatment comprising a second final neutralization treatment step in which a second neutralizing agent such as slaked lime is added and neutralization treatment is performed at pH 8.5 to 9.5 is preferred. By carrying out the neutralization treatment step by step in this way, the concentration of the impurity component can be efficiently removed to a level at which it can be released to the outside of the system.

The odor reduction method of the present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications and alternative examples can be made without departing from the scope of the present invention. can be included. That is, the scope of rights of the present invention covers the claims and their equivalents. EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

A nickel-cobalt mixed sulfide was produced by processing a nickel oxide ore along the process flow of the hydrometallurgical process shown in FIG. At that time, 1.8 Nm ³ of air per 1 m ³ of the final solution of nickel recovery discharged from the nickel recovery step S 6 was blown in the sulfiding agent removal step S 7 . Further, in the waste water treatment step S8, various oxidizing slurries containing trivalent iron residue at various values within the range of 1 to 30% by mass are prepared, and in the sulfiding agent removal step S7, the oxidizing slurry is treated with the nickel It was added while variously changing the flow rate ratio within the range of 0.020 to 0.057 with respect to the final collected liquid. In this way, the oxidation treatment was carried out under various conditions. In the nickel recovery final solution, the dissolved amount of hydrogen sulfide, which is a sulfiding agent, was 49 mg/L.

Each of the poor liquid sample groups obtained by oxidation treatment under various conditions as described above is introduced into the final neutralization step S8, and limestone is added in the first neutralization tank to neutralize at pH 5.5. and a second final neutralization step in which slaked lime is added in a second neutralization tank and neutralized at pH 9.0. At that time, the H ₂ S concentration in the gas phase part of the second neutralization tank is measured, and this measured value is divided by the voluntary control standard value of odor of 20 ppm to obtain the relative ratio of odor to the voluntary control standard value. An odor index, which is an index representing the That is, if the measured H ₂ S concentration is 20 ppm, the odor index will be 1.0. FIG. 2 shows the relationship between the odor index of the poor liquid of each of the above samples and the flow rate ratio of the oxidizing slurry to the nickel recovery final liquid at the time of its production.

Of the various samples shown in FIG. 2 above, samples 1 to 10 are extracted as typical samples, and the pH of the nickel recovery final solution at the time of their production, the flow rate ratio of the oxidizing slurry to the nickel recovery final solution at the time of production , the concentration of trivalent iron hydroxide in the oxidizing slurry, and the odor index are shown in Table 1 below.

From the results shown in Table 1 above, Samples 1 to 5 satisfying the requirements of the present invention had an odor index lower than 1.0, which is below the voluntary control standard value for odor. On the other hand, Samples 6 to 10, which do not satisfy the requirements of the present invention, all had an odor index exceeding 1.0. This is presumably because the flow rate ratio of the oxidizing slurry to the final solution of nickel recovery was less than 0.025 in each case, so that the decomposition reaction was insufficient and a large amount of hydrogen sulfide remained in the poor solution. .

S1 Leaching step S2 Preliminary neutralization step S3 Solid-liquid separation step S4 Neutralization step S5 Dezincification step S6 Nickel recovery step S7 Sulfurizing agent removal step S8 Final neutralization step

Claims (3)

Nickel discharged during solid-liquid separation of a nickel-cobalt mixed sulfide in a hydrometallurgical process in which a sulfiding agent is added to a leachate obtained by high-pressure acid leaching of nickel oxide ore containing cobalt to produce a mixed sulfide of nickel-cobalt. A method for reducing the odor generated when the final recovery solution is neutralized, comprising blowing air into the final recovery solution for nickel, adjusting its pH to 2.0 or less, and removing trivalent iron residue. oxidizing slurry containing 1 to 30% by mass of the nickel recovery final solution at a flow rate ratio of 0.025 or more to oxidize the reducing sulfur compound , wherein the oxidizing slurry is the above A method for reducing odor, characterized in that the final nickel recovery solution is obtained by neutralizing the poor solution obtained after the oxidation treatment . 2. The odor reduction method according to claim 1, wherein the sulfur compound is dissolved hydrogen sulfide added as the sulfurizing agent. Before adding the sulfurizing agent to the leachate, the pH of the leachate is adjusted to produce neutralized sediment containing impurity elements, which is then removed to obtain a final neutralization solution containing nickel and cobalt. and a dezincing step of adding hydrogen sulfide gas to the final neutralization solution to form a mixed sulfide containing zinc and copper, which is then removed to obtain a final dezincing solution. 3. The odor reduction method according to claim 1 or 2, characterized by treating.

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