JP7247729B2 - Neutralization treatment method for poor liquid generated in hydrometallurgy of nickel oxide ore - Google Patents

Description

The present invention relates to a method for neutralizing poor liquid generated in the hydrometallurgical process of nickel oxide ore, and more particularly to a leachate containing valuable metals such as nickel obtained by leaching nickel oxide ore as a raw material. , a neutralization treatment method for removing residual metal ions by neutralization in a poor liquid discharged when recovering the valuable metal in the form of sulfide by applying a sulfurization treatment.

A hydrometallurgical method is known that includes a high pressure acid leaching process (HPAL: High Pressure Acid Leaching process) in which nickel oxide ore as a raw material is subjected to leaching treatment using sulfuric acid at high temperature and high pressure. This hydrometallurgical process differs from the conventional pyrometallurgical process for smelting nickel oxide ore, and does not require a reduction process or a drying process. And in addition to being advantageous in terms of cost, it has the advantage of being able to produce a sulfide containing nickel with a nickel grade of about 50% by mass (hereinafter also referred to as nickel sulfide) from a low-grade nickel oxide ore. .

In the above hydrometallurgical method, after purifying a leachate consisting of an aqueous sulfuric acid solution containing valuable metals such as nickel and impurity metal elements obtained by leaching nickel oxide ore as a raw material, the leaching solution is subjected to a sulfidation treatment. Nickel sulfide is produced as a precipitate. In this sulfurization treatment, a sulfurizing agent such as hydrogen sulfide gas is blown into the leachate consisting of an aqueous sulfuric acid solution containing nickel as a main component. By generating sulfides containing metals and recovering them by solid-liquid separation, a poor liquid in which the nickel concentration is stabilized at a low level is discharged to the liquid phase side of the solid-liquid separation.

In the poor liquid consisting of an acidic solution with a low pH value discharged during the recovery of sulfides by the above-mentioned solid-liquid separation, residual metal ions such as iron, magnesium, manganese, etc. that remain without being sulfided in the above-mentioned sulfidation treatment are impurities. include. Therefore, in order to discharge this poor liquid out of the system, it is necessary to neutralize the pH value and to perform a neutralization treatment to remove the residual metal ions.

Conventionally, as a method for neutralizing the poor liquid, neutralization using one type of neutralizing agent has been mainly performed. In this method, it was necessary to use a strongly alkaline neutralizer to neutralize to the target pH value. As such a strong alkaline neutralizing agent, caustic soda, sodium carbonate and the like can generally be mentioned, but industrially, a slaked lime slurry is used which is more advantageous in terms of cost than these neutralizing agents. There are many.

In recent years, the amount of poor liquid produced by the sulfurization treatment tends to increase, and as a result, the retention time in the reaction tank where the neutralization treatment is performed by adding a neutralizing agent decreases, and the reaction efficiency decreases. was there. In order to compensate for this decrease in reaction efficiency, a large amount of neutralizing agent is added, and even if the slaked lime slurry, which is relatively advantageous in terms of cost, is used, the increase in product cost may become a problem. rice field.

Therefore, for example, in Patent Document 1, a sodium carbonate solution or the like used as a neutralizing agent in the neutralization treatment of poor liquid containing impurities of metal ions discharged in the wet treatment of nickel oxide ore as described above. A technique is disclosed to replace the part with an inexpensive calcium carbonate slurry. Specifically, the poor liquid is first neutralized to a predetermined pH using a calcium carbonate slurry as a first neutralizing agent, and then neutralized using a sodium carbonate solution as a second neutralizing agent. are processing. It is described that the consumption cost of the neutralizing agent can be reduced by performing the neutralizing treatment in stages using two types of neutralizing agents.

JP 2015-105396 A

As described in Patent Document 1 above, although it is possible to reduce the consumption cost of the neutralizing agent to some extent by using two types of neutralizing agents, it is not possible to cope with the case where a further large cost reduction is required. something happened. The present invention has been made in view of the problems of the conventional neutralization treatment method described above, and even if the amount of poor liquid generated in the hydrometallurgy of nickel oxide ore increases, the consumption of the neutralizer It is an object of the present invention to provide a method for efficiently neutralizing the poor liquid while suppressing the

In order to achieve the above object, the neutralization treatment method according to the present invention provides a weakly alkaline first neutralization treatment method for an aqueous sulfuric acid solution containing impurity metal ions of one or more of iron, magnesium, and manganese. a first neutralization treatment step of adding a solubilizing agent and neutralizing the pH within the range of 5.0 or more and 6.0 or less as an end point; A second neutralization in which the mixture is charged into a vertical cylindrical reaction vessel having a baffle plate and neutralized by adding a second neutralizing agent having a higher basicity than the first neutralizing agent. wherein the addition position of the second neutralizing agent in the reaction vessel is 2 to 6 degrees upstream of the baffle in the direction of stirring relative to the circumferential direction of the reaction vessel. and introducing the second neutralizing agent downward into the reaction vessel so as to be separated from the inner wall surface of the reaction vessel in the radial direction of the reaction vessel by the distance of the width of the baffle plate. It is characterized by

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to neutralize a poor liquid efficiently, suppressing the consumption of a neutralizing agent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow diagram of a hydrometallurgical method for nickel oxide ore by high-temperature pressure acid leaching, to which the neutralization treatment method of the embodiment of the present invention is suitably applied. It is a process flow figure of the neutralization treatment method concerning the embodiment of the present invention. It is a schematic plan view of a reaction vessel used in the neutralization treatment method according to the embodiment of the present invention. FIG. 2 is a flow diagram of a reaction tank used in Examples and Comparative Examples of the present invention; It is a graph plotting the relationship between the pH of the neutralization final solution obtained by the neutralization treatment methods of the examples and comparative examples of the present invention and the reaction efficiency of the neutralizing agent.

First, the method for hydrometallurgical refining of nickel oxide ore by the HPAL process, to which the poor liquid neutralization method according to the embodiment of the present invention is suitably applied, will be described with reference to FIG. The hydrometallurgy method shown in FIG. 1 includes a leaching step S1 in which sulfuric acid is added to an ore slurry containing nickel oxide ore having a predetermined particle size and leaching is performed under high temperature and high pressure, and the leaching step S1 obtains The leaching slurry comprising the leaching solution and the leaching residue is preferably solid-liquid separated by a plurality of thickeners connected in series to remove the leaching solution containing iron, magnesium, manganese, etc. as impurity ions in addition to nickel and cobalt from the leaching residue. A solid-liquid separation step S2 for separation, and deironization to obtain a mother liquor for recovering nickel by adding a pH adjuster to the leachate to generate sediment containing iron, which is separated and removed in the form of sediment slurry. Step S3, a sulfurization step S4 in which a mixed sulfide containing nickel and cobalt is produced by adding a sulfiding agent to the mother liquor, and then the mixed sulfide is recovered by solid-liquid separation, and a solid-liquid of the mixed sulfide and a neutralization treatment step S5 for neutralizing the poor liquid discharged to the liquid phase side at the time of separation. Each of these steps will be described below.

(1) Leaching step S1
In the leaching step S1, first, nickel oxide ore as a raw material is charged into a crusher and a screen to be powdered, and then water is added to wet classify the ore containing nickel oxide ore having a predetermined particle size. Collect the slurry on the underside of the sieve. This ore slurry is put into a pressure vessel called an autoclave together with sulfuric acid, and subjected to leaching treatment under high temperature and high pressure conditions of about 3 to 4.5 MPaG and about 220 to 280° C. while stirring. As a result, a leaching reaction and a high-temperature thermal hydrolysis reaction occur, and nickel, cobalt, etc. are leached as sulfate salts, and the leached iron sulfate is fixed as hematite, resulting in a leaching slurry consisting of a leaching solution and a leaching residue. is generated.

The nickel oxide ore used as the raw material is mainly so-called laterite ore such as limonite ore and saprolite ore. Laterite ores generally have a nickel content of 0.8 to 2.5% by weight and are contained 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.

The amount of sulfuric acid to be charged into the autoclave is not particularly limited, but it is preferable to add an excess amount so that the iron in the nickel oxide ore is leached well. 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 deteriorate the separation performance in the subsequent solid-liquid separation step S2. is preferred. In addition, the leaching slurry obtained in the leaching step S1 is pre-neutralized before solid-liquid separation in the solid-liquid separation step S2 to obtain free sulfuric acid (surplus sulfuric acid that did not participate in the leaching reaction, Also called free sulfuric acid) may be neutralized.

(2) Solid-liquid separation step S2
The leaching slurry obtained in the leaching step S1 is then subjected to a solid-liquid separation step S2 in which the leaching residue is removed by a countercurrent cleaning method also called a CCD method (Counter Current Decantation), and in addition to nickel and cobalt, iron and magnesium are removed as impurity ions. , manganese and the like is obtained. Specifically, in this countercurrent washing method, the leached slurry and the washing liquid are continuously introduced into a plurality of serially connected thickeners so as to flow countercurrently to each other. As a result, the leaching slurry introduced together with the coagulant into the most upstream thickener is transported to the most downstream thickener in sequence, where it is washed in multiple stages and solid-liquid separated by gravity sedimentation, and the leaching residue is removed. A separated exudate is obtained.

By performing solid-liquid separation by the CCD method in this manner, it is possible to efficiently recover the leachate with a smaller amount of cleaning liquid. It is preferable to use an aqueous solution having a pH of about 1.0 to 3.0 as the cleaning liquid, and the final neutralization liquid discharged from the neutralization treatment step S5 described later satisfies this condition. It is preferably used as the washing liquid.

(3) Deironization step S3
The leachate obtained in the solid-liquid separation step S2 is then added with a pH adjuster such as calcium carbonate in the iron removal step S3 to adjust the pH. A ferruginous precipitate is produced. In this iron removal step S3, the above pH adjustment is performed so that the pH of the treatment liquid is 2.0 or more and 4.0 or less, preferably 3.0 to 3.5, more preferably 3.1 to 3.2. is preferable, whereby ferrous precipitates can be efficiently produced mainly from trivalent iron ions and aluminum ions contained in the leachate.

The slurry containing the ferrous precipitates is preferably solid-liquid separated in a thickener so that the ferrous precipitates are removed from the bottom of the thickener in the form of a concentrated slurry, while the top end of the thickener overflows to form valuable metals. of nickel and cobalt is discharged. Part of the iron-containing sediment slurry extracted from the bottom of the thickener is extracted as necessary, and the solid-liquid separation step S2 is repeated.

(4) Sulfurization step S4
In the sulfurization step S4, the mother liquor for recovering nickel obtained in the iron removal step S3 is then charged into a sulfurization reaction tank under pressure, and a sulfurization reaction is initiated by adding a sulfurization agent such as hydrogen sulfide gas. to form a mixed sulfide containing nickel and cobalt. This mixed sulfide is recovered by a solid-liquid separator such as a filter press, and at that time, a poor liquid is discharged to the liquid phase side.

The mother liquor for nickel recovery may contain several g/L of metal ions such as Fe, Mg, and Mn as impurities. has a low stability and thus hardly partitions to the mixed sulfide side. Further, when zinc is contained in the above mother liquor, it is introduced into a slightly pressurized dezincification reactor before being charged into the pressurized sulfurization reactor, and hydrogen sulfide gas is introduced into the gas phase. is preferably blown in to selectively sulfide zinc relative to nickel and cobalt and separate and remove the zinc sulfide produced thereby.

(5) Neutralization treatment step S5
The poor liquid consisting of the sulfuric acid aqueous solution obtained in the sulfurization treatment S4 is then neutralized in two steps in the neutralization treatment step S5, whereby the iron, magnesium, and manganese contained as impurity metal ions in the poor liquid are neutralized. A neutralized precipitate is produced from residual metal ions composed of any one or more of them, and the neutralized final solution is obtained by removing the neutralized precipitate by solid-liquid separation.

Specifically, as shown in the process flow diagram of FIG. 2, first, as a first neutralization treatment step S51, the poor liquid charged into the first reaction tank is treated with carbonic acid having a relatively low basicity. A weakly alkaline first neutralizing agent such as calcium slurry is added, and the neutralization treatment is performed with the end point within the pH range of 5.0 or more and 6.0 or less. Next, as a second neutralization treatment step S52, the solution treated in the first neutralization treatment step S51 is transferred from the first reaction tank to the second reaction tank, and the solution in the second reaction tank is On the other hand, a second neutralizing agent such as slaked lime having higher basicity than the first neutralizing agent is added for neutralization. As a result, neutralized precipitates are generated from the residual metal ions contained in the poor solution. By removing this neutralization sediment with a solid-liquid separation device such as a filter press, a final neutralization solution from which the residual metal ions have been substantially removed is obtained.

Thus, the neutralizing agent added in the first neutralizing step S51 of the two-stage neutralizing step is more basic than the strong alkaline neutralizing agent added in the second neutralizing step S52. By using a neutralizing agent such as a calcium carbonate slurry with a low degree, the amount of the strongly alkaline neutralizing agent used can be reduced. Therefore, even if the amount of the poor liquid discharged from the sulfurization step S4 increases, the neutralization treatment can be efficiently performed while suppressing the consumption cost of the highly alkaline neutralizing agent.

If the pH at the end point in the first neutralization treatment step S51 is less than 5.0, the neutralization treatment in the first neutralization treatment step S51 is insufficient, and the second neutralization treatment described later is performed. The load of the neutralization process in step S52 increases, and as a result, the usage amount of the second neutralizing agent increases. Conversely, when the pH at the end point in the first neutralization treatment step S51 exceeds 6.0, the load of the neutralization treatment in this first neutralization treatment step S51 increases, and the use of the first neutralizing agent quantity will increase. Further, even when the load of the neutralization treatment in the first neutralization treatment step S51 is increased by adjusting the end point pH to exceed 6.0, the neutralization in the second neutralization treatment step S52 Since the amount of the agent used is almost the same, the amount of the neutralizer used in the neutralization treatment step S5 as a whole increases, which is uneconomical.

Further, in the neutralization treatment in the second neutralization treatment step S52, it is preferable to adjust the pH at the end point within the range of 8.5 or more and 9.0 or less. If the pH at the end point is less than 8.5, the neutralization of residual metal ions composed of impurities such as iron, magnesium, manganese, etc. contained in the poor solution will not be sufficiently neutralized, and these residual metal ions will be neutralized. It may remain in the final solution. Conversely, if the endpoint pH exceeds 9.0, even if the amount of the second neutralizing agent added is increased, the formation of the residual metal ions is not promoted proportionally. Therefore, the consumption of the second neutralizing agent increases, which is uneconomical.

As described above, the neutralizing agent used in the second neutralizing step S52 is preferably slaked lime. This is because slaked lime has a higher basicity than sodium carbonate, and can be neutralized more effectively. It is desirable that the slaked lime used in the second neutralization step S52 be in the form of slurry having a solid content concentration of 15% by mass or more and 25% by mass or less. If the solid content concentration is less than 15% by mass, the volume of the slaked lime slurry required for the neutralization treatment becomes too large, and the residence time in the second reaction vessel having a predetermined effective volume decreases, resulting in insufficient neutralization treatment. may become Conversely, when the solid content concentration exceeds 25% by mass, the diffusibility of the slaked lime slurry in the second reaction tank decreases, and an excess neutralizing agent is required to neutralize to the above target pH. This may result in an increase in processing costs.

In the neutralization method of the embodiment of the present invention, a vertical columnar container with a stirrer is used as the second reaction vessel for neutralization in the second neutralization step S52. Furthermore, in order to improve the stirring effect by inhibiting the flow in the circumferential direction in the second reaction tank by the stirring blades of the stirrer, a protruding part protrudes from the cylindrical body toward the central axis in the second reaction tank. At least one baffle plate is installed so as to extend vertically from the upper end to the lower end of the cylindrical body.

Then, as shown in FIG. 3, when the rotation direction of the stirrer 2 in the second reaction vessel 1 is clockwise as indicated by the white arrow, the second neutralization added to the solution in the second reaction vessel 1 The second neutralizing agent addition position 4A is placed adjacent to the front side of the baffle plate 3 with respect to the flow direction in the second reaction vessel 1 so that the agent is more efficiently mixed with the solution. Specifically, the second neutralizing agent addition position 4A is positioned upstream of the baffle plate 3 in the circumferential direction of the second reaction vessel 1 by 2 to 6 degrees in the stirring direction, preferably 3 degrees in the stirring direction. Installed on the upstream side. The radial position of the second neutralizing agent addition position 4A in the second reaction vessel 1 is separated from the inner wall surface of the cylindrical body of the second reaction vessel 1 by a distance equal to or less than the width W of the baffle plate 3. Although there is no particular limitation as long as it does, the closer the baffle plate 3 is to the central axis side end 3a of the second reaction tank 1, the better.

When the second neutralizing agent addition position 4A is positioned upstream of the baffle plate 3 in the stirring direction with respect to the circumferential direction of the second reaction tank 1 and within an angular range of less than 2 degrees, Since the addition position 4A of the second neutralizing agent is too close to the baffle plate 3, the second neutralizing agent and the solution in the second reaction tank 1 are not efficiently mixed. Conversely, when the second neutralizing agent addition position 4A is positioned upstream of the baffle plate 3 in the stirring direction with respect to the circumferential direction of the second reaction tank 1 within an angle range exceeding 6 degrees , the ratio of the second neutralizing agent introduced from the addition position 4A to avoid the baffle plate 3 and mix with the solution rotating in the second reaction tank 1 increases. The admixture and the solution in the second reaction tank 1 are no longer efficiently mixed.

In addition, in the second reaction tank 1 shown in FIG. 3, three baffle plates 3 are arranged at equal intervals in the circumferential direction of the second reaction tank 1, that is, at intervals of 120 degrees. The baffle plate 3 is provided on the cylindrical body portion 1a of the second reaction vessel 1 so as to protrude toward the central axis, but the shape and number of baffle plates 3 are not limited to this. The number of sheets may be 1 or 2, or may be 4 or more. EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

[Example]
Along the process flow diagram of the hydrometallurgical method shown in FIG. 1, the poor liquid neutralization treatment method shown in FIG. Neutralization treatment was carried out according to the process flow diagram. Specifically, in the leaching step S1, sulfuric acid is added to an ore slurry containing nickel oxide ore having a predetermined particle size, and leaching treatment is performed under high temperature and high pressure. The leaching residue is sedimented and separated, and a pH adjuster is added to the obtained leaching solution in the iron removal step S3 to produce sediment, which is used as a sediment slurry to obtain a mother liquor (precious liquor) for recovering nickel consisting of an aqueous sulfuric acid solution containing nickel and cobalt as valuable metals and iron, magnesium and manganese as impurity metal ions.

Hydrogen sulfide gas was blown into the above mother liquor in the sulfurization step S4 to generate sulfides containing nickel and cobalt. This sulfide is recovered by solid-liquid separation with a filter press, and at that time, the poor liquid discharged as the liquid phase side is subjected to the first neutralization treatment step S51 and the second neutralization treatment step S52. The above-described impurity metal ions contained in the poor liquid were neutralized and removed by performing a two-step neutralization treatment to obtain a final neutralization liquid.

In these first neutralization treatment step S51 and second neutralization treatment step S52, as shown in FIG. 4, a total of four reaction tanks each consisting of two reaction tanks connected in series are continuously used. processed accordingly. The treated liquid treated in each reaction tank was discharged by overflow, and the treated liquid was transferred to the adjacent downstream reaction tank through a launder. Then, a pH meter is provided in each launder (trough) through which the treatment liquid flows in the latter reaction tank, and a neutralizing agent supply pipe is provided to the reaction tank in the previous stage based on the pH value measured by this pH meter. The opening of the flow control valve was adjusted.

That is, in the first neutralization treatment step S51, the supply amount of the first neutralizing agent to be supplied to the first pre-reaction tank 11 is adjusted based on the pH value of the treatment liquid overflowing from the first post-reaction tank 12. Then, in the second neutralization treatment step S52, the supply amount of the second neutralizing agent to be supplied to the second pre-reaction tank 21 is adjusted based on the pH value of the treatment liquid overflowing from the second post-reaction tank 22. bottom. The treated liquid extracted from the second rear-stage reaction tank 22 due to overflow was supplied to the rear-stage solid-liquid separation device via a pump.

A vertical cylindrical vessel with a diameter of φ8680 mm and a height of 13300 mm was used for each reaction vessel, and a stirrer was provided so that a rotating shaft was rotated at the central axis portion of the vessel. A stirring blade consisting of four propellers having a diameter of φ3251 mm and a paddle width of 1422 mm was provided at the tip of the rotary shaft of the stirrer. Three baffle plates 3 each having a width W of 1000 mm were provided on the inner wall surface of the cylinder of each reaction vessel at intervals of 120 degrees along the circumferential direction of the reaction vessel. Further, in the second pre-reaction tank 21, the second neutralizing agent addition position 4A is set further than the tip 3a of the baffle plate 3 in the circumferential direction of the second pre-reaction tank 21, as shown in FIG. It was provided on the upstream side in the 3-degree stirring direction. The addition position of the first neutralizing agent in the first pre-stage reaction tank 11 was the position 4B in FIG.

Then, the poor liquid having a pH of 1.7 was supplied to the first front-stage reaction tank 11 and transferred to the rear-stage reaction tanks sequentially. At that time, the overflow liquid level was adjusted so that the height from the bottom surface to the liquid surface in each reaction tank was 10100 mm, and the neutralization treatment was performed under the setting conditions of the rotational speed of the stirring blade of 1800 rpm. Furthermore, 3 mol/L of calcium carbonate slurry is added as a first neutralizing agent to the first pre-reaction tank 11 so that the end point pH in the first post-reaction tank 12 is 5.1 to 5.4. A first neutralization treatment was performed. In addition, slaked lime with a solid content concentration of 15 to 25% by mass is added to the second front reaction tank 21 as a second neutralizing agent so that the end point pH in the second rear reaction tank 22 is 8.5 to 9.0. A second neutralization treatment was performed by adding the slurry. At that time, the residence time in each reactor was in the range of 19 to 22 minutes.

In the above second neutralization treatment, the reaction efficiency of slaked lime defined by the following formula 1 was calculated. Here, the theoretical amount of slaked lime used is the impurity calculated from the stoichiometric amount required to neutralize the impurities remaining in the treated liquid after the first neutralization treatment discharged from the first post-reaction tank 12. Neutralization equivalent. Therefore, the value of the reaction efficiency of the following formula 1 obtained by dividing the theoretical amount of slaked lime used by the amount of the second neutralizing agent actually added in the second front-stage reaction tank 21 (actual amount of slaked lime used) is large. The more, the better the reaction efficiency is.
[Formula 1]
Reaction efficiency (%) = theoretical amount of slaked lime used (mol) / actual amount of slaked lime used (mol) x 100

[Comparative example]
The addition position 4A of the second neutralizing agent in the second pre-reaction tank 21 is, as shown in FIG. Neutralization treatment was carried out in the same manner as in the above example except that it was provided on the downstream side of the .

FIG. 4 shows a graph plotting the reaction efficiency of the neutralizing agent of Formula 1 above against the final pH value in the above Examples and Comparative Examples. From the results of FIG. 4, the reaction efficiency of slaked lime was improved by about 10% in the example compared to the comparative example. In this way, a calcium carbonate slurry is added as a first neutralizing agent to the poor solution, and the primary neutralization treatment is performed with the pH range of 5.0 to 6.0 as the end point. In addition, when performing secondary neutralization by adding slaked lime slurry as a second neutralizing agent, the adding position of the slaked lime slurry is 3 degrees downstream in the stirring direction from the tip of the baffle plate with respect to the circumferential direction of the reaction tank. It can be seen that the reaction efficiency of slaked lime is improved by providing it on the side.

S1 Leaching step S2 Solid-liquid separation step S3 Deironization step S4 Sulfurization step S5 Neutralization treatment step 1 Reaction tank 2 Stirrer rotating shaft 3 Baffle plate 4A Neutralizer addition device (Example)
4B Neutralizing agent addition device (comparative example)

Claims (4)

pH within the range of 5.0 or more and 6.0 or less by adding a weakly alkaline first neutralizing agent to an aqueous sulfuric acid solution containing impurity metal ions of at least one of iron, magnesium, and manganese and the solution obtained in the first neutralization step is charged into a vertical cylindrical reaction vessel equipped with a stirrer and baffles, and the and a second neutralization step of adding a second neutralizing agent having a higher basicity than the first neutralizing agent to perform neutralization, wherein The addition position of the second neutralizing agent is 2 to 6 degrees upstream of the baffle in the stirring direction with respect to the circumferential direction of the reaction vessel , and the inner wall surface of the reaction vessel in the radial direction of the reaction vessel. and introducing the second neutralizing agent from the top to the bottom of the reaction tank so as to be spaced apart by the width of the baffle plate. The aqueous sulfuric acid solution is obtained by adding sulfuric acid to a nickel oxide ore and subjecting it to high-temperature and high-pressure leaching, and then blowing hydrogen sulfide gas into the leachate containing nickel and cobalt to generate sulfide from the nickel and cobalt. 2. The method of neutralization treatment according to claim 1, wherein the sulfide is a poor liquid discharged to the liquid phase side when the sulfide is recovered by solid-liquid separation. 3. The neutralization method according to claim 1 or 2, wherein said second neutralization step performs neutralization with a pH range of 8.5 to 9.0 as an end point. The neutralization treatment method according to any one of claims 1 to 3, wherein the second neutralizing agent is a slaked lime slurry having a solid content concentration of 15% by mass or more and 25% by mass or less.

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