JP7238686B2 - Neutralization method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a neutralization method, and more particularly, to a neutralization method for neutralizing and removing impurity metals in a post-sulfidation liquid discharged through, for example, a hydrometallurgical process of nickel oxide ore. be.

A hydrometallurgical process including a high pressure acid leaching (HPAL) method in which nickel oxide ore as a raw material is leached using sulfuric acid at high temperature and high pressure is known (for example, Patent Document 1 reference). This hydrometallurgical process differs from the conventional pyrometallurgical process, which is the general smelting method of nickel oxide ore, because it is processed through a consistent wet process without going through the reduction process or drying process, so it is energy efficient. and cost effective. In addition, there is an advantage that a nickel-containing sulfide (hereinafter also referred to as “nickel sulfide”) with a nickel grade increased to about 50% by mass can be produced from a low-grade nickel oxide ore.

In the hydrometallurgical process using the HPAL method, first, several types of low-grade nickel oxide ores are mixed so as to have a predetermined nickel grade and impurity grade, and then mixed with water to form a slurry, which is sieved. , to prepare a predetermined undersized ore (ore blending process). Next, the slurried ore (ore slurry) is charged into a pressurized reaction vessel such as an autoclave, and nickel is leached using sulfuric acid under high temperature and high pressure conditions to produce a leaching slurry containing a leaching solution and a leaching residue. (leaching process).

Subsequently, since free acid that was not used in the leaching reaction remains in the leaching solution (sulfuric acid acid solution) obtained by the leaching treatment, the residual free acid is removed using a neutralizing agent such as limestone. Neutralize (preliminary neutralization step). After that, the leaching slurry that has undergone the preliminary neutralization process is transferred to the solid-liquid separation process and separated into the leaching liquid and the leaching residue (solid-liquid separation process). The separated leaching residue is sent to the tailing dam after removing heavy metals and the like to a predetermined concentration in the final neutralization step.

Next, a neutralizing agent is added to the leachate separated in the solid-liquid separation step to adjust the pH to a predetermined value, thereby removing impurities contained in the leachate (neutralization step).

Hydrogen sulfide gas as a sulfiding agent is added to the leachate from which impurities have been removed to cause a sulfurization reaction, fix nickel contained in the leachate as sulfide, and recover nickel sulfide. (sulfurization process).

On the other hand, part of the post-sulfidation solution (poor solution) after recovering nickel in the sulfurization step is sent to the solid-liquid separation step and reused, and the surplus is sent to the final neutralization step. Wastewater treatment (neutralization treatment) is performed.

Now, in the final neutralization step in the above-mentioned hydrometallurgical process, mainly the acidic slurry containing the leaching residue from the solid-liquid separation step and the post-sulfiding acid solution, which is the acidic solution remaining after recovery of the nickel sulfide from the sulfurizing step, is used. A portion of the liquid is treated as a target. Specifically, in the final neutralization step, a two-stage neutralization reaction is performed for the purpose of precipitating impurity metal components (metal ions) dissolved in the solution.

For example, in the neutralization treatment in the final neutralization step, a total of four reactors are used, and as the first stage, limestone (CaCO ₃ ) slurry is added to the first reactor to maximize the pH of the solution. By raising it to 6.0, mainly iron and aluminum are precipitated. Next, as the second step, slaked lime (Ca(OH) ₂ ) slurry is added to the third reaction tank to increase the pH of the solution to the range of 8.5 to 9.5, thereby mainly manganese , to precipitate nickel.

In the neutralization treatment for a solution containing heavy metals, the pH required to reduce the concentration of heavy metals to 1 mg/L or less is pH 9.0 for bivalent iron ions, pH 2.7 for trivalent iron ions, and pH 2.7 for trivalent iron ions. Manganese ions have a pH of 10.0, and trivalent manganese ions have a pH of 3.6. That is, the heavy metal ions in the solution form precipitates at pHs where the trivalent ions are lower than the divalent heavy metal ions. Since the process liquid charged in the final neutralization process is originally an acidic solution, the amount of the neutralizing agent used can be reduced when the pH is adjusted to a low level. Therefore, for the purpose of oxidizing the metal ions, for example, a blower is used to blow air into each reaction tank (see Patent Documents 2 and 3, for example).

Here, in the above example, in the third reaction tank, the pH is controlled within a predetermined range and the neutralization treatment is performed for the purpose of lowering the manganese concentration in the solution to 1 mg/L or less.

On the other hand, the post-sulfidation liquid to be neutralized also contains magnesium, which does not affect the environment and does not need to be removed from the waste water. However, when the pH is increased as manganese is removed, magnesium forms precipitates at the same time as manganese because the pH ranges for precipitation are close between manganese and magnesium (magnesium: about 9.0). That is, they coprecipitate. Therefore, the neutralizing agent is consumed by the amount of magnesium precipitates, resulting in the need for an excessive amount of the neutralizing agent. Such an increase in the amount of neutralizing agent used results in an increase in costs and an increase in the amount of precipitates that are generated, resulting in an increase in processing labor and costs, which is not preferable.

Attempts have also been made to carry out a so-called oxidation neutralization method in which a manganese-containing solution is actively oxidized to remove manganese in a lower pH range, thereby oxidizing while maintaining a constant pH. there is According to this method, the amount of neutralizing agent can be reduced.

For example, Patent Document 4 discloses a method of preferentially removing manganese from a magnesium-containing manganese acid solution by oxidation neutralization. Specifically, when removing manganese as a precipitate from a magnesium-containing manganese acid solution, the pH of the solution is adjusted to 8.2 to 8.8, and the oxidation-reduction potential (based on Ag/AgCl) of the solution is 10 mV. A method is disclosed for precipitating and removing manganese preferentially by conditioning with air, oxygen, ozone or peroxides to ˜500 mV.

However, when such an oxidation neutralization method is applied to the treatment of wastewater generated through the HPAL process, the post-sulfidation solution to be treated exhibits a strong reducing property, so treatment such as re-oxidation is required. is required, and there is a problem that the cost and labor are increased. Also in the method disclosed in Patent Document 4, when aluminum ions are contained in the solution, magnesium and aluminum precipitate at the same time, and the neutralizing agent neutralizes magnesium more than it removes manganese. Problems such as the need for a sufficient amount to be mixed and an increase in the amount of sediment cannot be fully resolved.

Therefore, in the method disclosed in Patent Document 5, prior to the oxidation-neutralization treatment of acidic wastewater, the pH of the wastewater is adjusted in advance to a range of 4 to 6 to separate aluminum, and then the wastewater after aluminum removal is added to A neutralizing agent is added to adjust the pH to 8.0 to 9.0, and oxygen gas is blown in. According to this method, coprecipitation of magnesium and aluminum can be suppressed, and aluminum can be effectively separated.

However, since the aluminum precipitate formed by the method disclosed in Patent Document 5 is very bulky, there is a problem of bulkiness during handling. In addition, since oxygen gas is used for oxidation in all steps, there is also a problem of increased cost.

Regarding these problems, Patent Document 6 proposes a wastewater treatment method for selectively removing manganese from sulfuric acid-acid wastewater containing aluminum, magnesium, and manganese. Specifically, this method includes a step of adding a first neutralizing agent to sulfuric acid acidic waste water to adjust the pH to 4.0 to 6.0 to separate the solution into a solution after dealumination and aluminum precipitates. adding a slurrying solution to the aluminum precipitate to form a slurry, then adding an alkali to form a pH-adjusted aluminum precipitate slurry having a pH adjusted to 9.0 to 9.5; adding a second neutralizing agent to adjust the pH to 8.0 to 9.0 and then adding an oxidizing agent to form an oxidation-neutralized post-oxidation-neutralized slurry; an aluminum precipitate slurry; After oxidation and neutralization, the slurry is subjected to solid-liquid separation to suppress the precipitation of magnesium from sulfuric acid acid wastewater containing aluminum, magnesium and manganese to obtain demanganized wastewater, which is then subjected to a third neutralization. It is to obtain wastewater sediment and discharged wastewater by adding the agent.

However, in the actual operation of industrially recovering nickel from nickel oxide ore, a large amount of neutralizing agent is still required. Furthermore, with calcium-based neutralizers such as slaked lime and limestone, which are readily available industrially and commonly used, the calcium sulfate (gypsum) refined by the neutralization treatment itself becomes a precipitate, and the gypsum becomes a precipitate. There is a problem that effective use of the leaching residue is restricted due to coexistence of calcium and sulfur, which are components.

Specifically, in the method disclosed in Patent Document 6 described above, calcium precipitates are mixed with manganese, making it difficult to reuse manganese as a resource, and it cannot be effectively used as a valuable resource. Moreover, since the manganese precipitates are accumulated and stored or discarded, environmental measures are required.

Further, in Patent Document 7, a first neutralizing agent is added to sulfuric acid acidic wastewater containing aluminum, magnesium, and manganese to separate aluminum hydroxide precipitates, and then a second neutralizing agent and oxidation one of the first to third neutralizing agents to be added in the wastewater treatment method for separating manganese sediment by adding a neutralizing agent and then adding a third neutralizing agent to obtain wastewater sediment and effluent wastewater A wastewater treatment method has been proposed in which recycled and manufactured magnesium oxide is used partially or entirely.

However, in the method disclosed in Patent Document 7, due to an increase in the number of steps such as a calcium separation step, a magnesium roasting step, and a crystallization step, and an increase in the number of facilities, the initial investment cost increases, the maintenance cost increases, and the process There is concern about an increase in the burden on operational management, such as an increase in the number of management personnel.

JP 2005-350766 A JP 2014-113566 A JP 2017-185457 A JP-A-9-248576 JP 2010-207674 A JP 2011-206757 A Japanese Patent Application Laid-Open No. 2015-367

The present invention has been proposed in view of such circumstances, and is capable of reducing the consumption of the neutralizing agent and reducing the cost of the oxidizing agent from an acidic solution containing at least iron, manganese, magnesium, and aluminum. Another object of the present invention is to provide a method for selectively precipitating and removing harmful metal elements.

The inventor of the present invention has made extensive studies. As a result, the neutralization treatment for the acidic solution to be treated is performed in two stages, and each neutralization treatment is performed by using a plurality of reaction tanks connected in series and supplying an oxidant to each reaction tank, In particular, by supplying pure oxygen as an oxidant only to the most upstream reaction tank where neutralization is performed in the second neutralization process (second stage), the amount of the neutralizer used can be reduced and oxidation can be reduced. The inventors have found that the cost of the agent can be effectively reduced and efficient neutralization treatment can be performed, and have completed the present invention.

(1) A first invention according to the present invention is a method for neutralizing an acidic solution containing at least iron, manganese, magnesium, and aluminum, wherein a first neutralizing agent is added to the acidic solution. a first step of performing a neutralization treatment with a pH range of 5.0 to 6.0 as an end point, and the solution after the neutralization treatment in the first step is more basic than the first neutralizing agent and a second step of adding a second neutralizing agent having a high degree of neutralization to perform a neutralization treatment, wherein the neutralization treatments of the first step and the second step are connected in series. Using a plurality of reaction tanks provided in the same manner, the oxidizing agent is supplied to each reaction tank, and only the most upstream reaction tank in which the neutralization treatment in the second step is performed is supplied with pure oxidizing agent as the oxidizing agent. It is a neutralization treatment method that supplies oxygen.

(2) A second invention according to the present invention is the first invention, wherein in the second step, the oxidation-reduction potential (based on Ag/AgCl) of the solution in the most upstream reaction vessel is -100 mV to +300 mV. It is a neutralization treatment method in which the pure oxygen is supplied so as to fall within the range.

(3) A third invention according to the present invention is the first or second invention, wherein in the second step, the pH range is adjusted to 8.5 to 9.0 by adding the second neutralizing agent. It is a neutralization treatment method in which neutralization treatment is performed as an end point.

(4) A fourth invention according to the present invention is any one of the first to third inventions, wherein the neutralization treatment in the first step is performed in two tanks, a first reaction tank and a second reaction tank. The neutralization treatment in the second step is continuously performed using two reaction tanks, the third reaction tank and the fourth reaction tank, and the In the neutralization treatment method, the pure oxygen is supplied as the oxidizing agent only to the third reaction tank, which is the most upstream reaction tank in the neutralization treatment in the second step.

(5) A fifth invention according to the present invention is the fourth invention, wherein the first reaction vessel and the second reaction vessel in the neutralization treatment in the first step, and the second step In the neutralization treatment method, air is supplied as the oxidizing agent to the fourth reaction tank in the neutralization treatment in the above.

(6) A sixth aspect of the present invention is the method according to any one of the first to fifth aspects, wherein the acidic solution is a leaching solution obtained through a leaching process of leaching nickel from nickel oxide ore using sulfuric acid. On the other hand, it is a neutralization treatment method, which is a post-sulfurization solution obtained by adding a sulfurizing agent and performing a sulfurization treatment.

(7) A seventh invention according to the present invention is the neutralization method according to the sixth invention, wherein the ratio of aluminum grade to magnesium grade in the nickel oxide ore (Al/Mg ratio) is less than 2.0. is.

According to the present invention, from an acidic solution containing at least iron, manganese, magnesium, and aluminum, the amount of the neutralizing agent used can be reduced, and the cost of using the oxidizing agent can be effectively reduced, thereby efficiently removing harmful metal elements. can be precipitated out.

BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows an example of the flow of a hydrometallurgy process of a nickel oxide ore. It is process drawing which shows an example of the flow of a neutralization process. It is a schematic diagram which shows the structural example of the neutralization processing equipment which consists of several reaction tanks which perform neutralization processing. 2 is a graph showing measurement results of manganese concentration in solution with respect to pH when the second-stage neutralization treatment is performed in Example 1 and Comparative Example 1. FIG. FIG. 10 is a graph showing measurement results of residual magnesium concentration in solution with respect to pH when post-sulfidation solutions obtained using ores having different Al/Mg ratios were subjected to the second-stage neutralization treatment in Example 2. .

Specific embodiments of the present invention will be described in detail below. In addition, the present invention is not limited to the following embodiments, and various modifications are possible without changing the gist of the present invention. In this specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

≪1. Overview≫
The neutralization treatment method according to the present invention is a neutralization treatment method for an acidic solution containing at least iron, manganese, magnesium, and aluminum. It is a method of separating and removing by forming a precipitate in a small amount.

Specifically, this neutralization treatment method includes a first step of adding a first neutralizing agent to an acidic solution to be treated and performing a neutralization treatment with a pH range of 5.0 to 6.0 as an end point; a second step of neutralizing the solution by adding a second neutralizing agent having a higher basicity than the first neutralizing agent to the solution after the neutralization treatment in the first step; . Then, the neutralization treatment of each of the first step and the second step is performed by using a plurality of reaction tanks connected in series and supplying an oxidizing agent to each reaction tank. It is characterized in that pure oxygen is supplied as an oxidizing agent only to the most upstream reaction vessel in the neutralization treatment in step 2.

More specifically, for example, the neutralization treatment in the first step is continuously performed using two reaction tanks, a first reaction tank and a second reaction tank, and The summation treatment is performed continuously using two reactors, a third reactor and a fourth reactor (see FIG. 3 described below). Then, the neutralization treatment is performed while supplying the oxidizing agent in each of the first reaction tank to the fourth reaction tank. Pure oxygen is supplied as an oxidizing agent only to the third reactor, which is a reactor.

At this time, an oxidizing agent such as supply air.

According to such a method, it is possible to selectively separate and remove harmful elements from an acidic solution containing iron, manganese, magnesium, and aluminum, reduce the consumption of the neutralizing agent, and effectively reduce the cost of the oxidizing agent. can be reduced and efficient processing can be performed.

Here, the neutralization treatment method according to the present invention can be applied to treatment in the final neutralization step in the hydrometallurgical process of nickel oxide ore. Then, the acidic solution to be treated in that case is obtained by adding a sulfiding agent to the leachate obtained through the leaching treatment of leaching nickel from the nickel oxide ore using sulfuric acid and subjecting it to sulfurization treatment. After sulfurization, it becomes a liquid (poor liquid). Note that iron, manganese, magnesium, and aluminum are metals that remain in the solution after sulfiding through the hydrometallurgical process of nickel oxide ore.

Thus, when the neutralization treatment method according to the present invention is applied to treatment in the final neutralization step in the nickel oxide ore hydrometallurgical process, the treatment cost of the process can be effectively reduced, and it is economically excellent. It becomes possible to carry out the process described above to produce nickel sulfide.

In the following, the post-sulfidation solution obtained through the hydrometallurgical process of nickel oxide ore is used as the acidic solution to be treated, and the neutralization treatment method is applied to the final neutralization process in the hydrometallurgical process. A more detailed description will be given by taking a case as an example.

≪2. Hydrometallurgical Process of Nickel Oxide Ore≫
An overview of the hydrometallurgical process of nickel oxide ore is given. Here, a hydrometallurgy process using high-pressure acid leaching, in which leaching is performed using sulfuric acid at high temperature and high pressure, will be described as a specific example.

FIG. 1 is a process diagram showing the flow of a hydrometallurgical process using a high-pressure acid leaching method for nickel oxide ore. The nickel oxide ore hydrometallurgical process includes a leaching step S1 of leaching nickel from a nickel oxide ore slurry, a solid-liquid separation step S2 of solid-liquid separation into a leachate and a leach residue from the obtained leach slurry, and separating the leachate. A neutralization step S3 in which the mother liquor for recovering nickel and the neutralized precipitate are separated by neutralization, and a sulfiding agent is added to the sulfuric acid solution, which is the mother liquor, to perform a sulfidation treatment, and a sulfide containing nickel and a post-sulfidation solution ( and a sulfurization step S4 of obtaining a poor liquid).

(Leaching process)
In the leaching step S1, sulfuric acid is added to slurry of nickel oxide ore (ore slurry), and the mixture is stirred under high temperature and high pressure to produce a leaching slurry composed of a leaching solution and a leaching residue. For the leaching treatment in the leaching step S1, for example, a high-temperature pressurized container (autoclave) is used.

Here, the nickel oxide ores used as raw materials mainly include so-called laterite ores such as limonite ores and saprolite ores. The content of nickel in laterite ore is about 0.8% by mass to 2.5% by mass, and is contained as a hydroxide or magnesium silicate (magnesium silicate) mineral. In addition, the content of iron is about 10% by mass to 50% by mass, and it is mainly in the form of trivalent hydroxide (goethite), but some divalent iron is contained in magnesium silicolite minerals. be.

In the leaching step S1, metal components such as nickel and cobalt are leached as sulfates, and 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.

The concentration of the ore slurry to be subjected to the leaching treatment is not particularly limited, but it is preferable to adjust the slurry concentration of the leaching slurry to about 15% by mass to 45% by mass. Also, the amount of sulfuric acid added in the leaching process is used in an excessive amount such that the iron in the ore is leached. For example, about 300 kg to 400 kg per ton of ore. If the amount of sulfuric acid added per ton of ore exceeds 400 kg, the cost of sulfuric acid increases, which is undesirable.

(Solid-liquid separation step)
In the solid-liquid separation step S2, the leaching slurry produced in the leaching step S1 is washed in multiple stages to separate into a leaching solution containing nickel and a leaching residue consisting of precipitates containing impurity metals such as iron.

As the multi-stage cleaning method in the solid-liquid separation step S2, it is preferable to use a continuous AC cleaning method in which a nickel-free cleaning liquid is brought into contact in a countercurrent flow. As a result, it is possible to reduce the amount of cleaning liquid newly introduced into the system, and to increase the recovery rate of nickel and cobalt to 95% or more.

(Neutralization process)
In the neutralization step S3, a neutralizing agent such as calcium carbonate is added so that the pH of the separated leachate becomes 4.0 or less, preferably 2.8 to 3.0, while suppressing oxidation of the separated leachate. to produce a mother liquor for nickel recovery and a slurry of neutralized sediment containing trivalent iron. By neutralizing the leaching solution in this manner, the excess acid used in the leaching treatment is neutralized, and trivalent iron ions, aluminum ions, etc. remaining in the solution are removed. Incidentally, when the pH of the leachate exceeds 4.0, the amount of nickel hydroxide generated increases.

The neutralized precipitate slurry obtained in the neutralization step S3 can be sent to the solid-liquid separation step S2 as required. As a result, nickel contained in the neutralized sediment slurry can be effectively recovered.

(Sulfurization process)
In the sulfurization step S4, a sulfurization agent such as hydrogen sulfide gas is added to the sulfuric acid solution, which is the mother liquor for recovering nickel obtained in the neutralization step S3, to cause a sulfurization reaction to produce a sulfide containing nickel (nickel sulfide ) and a post-sulfidation solution. In addition, when zinc is contained in the mother liquor, a treatment for selectively separating zinc as sulfide can be performed prior to generating nickel sulfide by the sulfurization reaction.

The mother liquor for recovering nickel to be subjected to the sulfurization treatment is, as described above, a nickel-containing sulfuric acid solution based on the leachate obtained by leaching the nickel oxide ore. Specifically, for example, the pH is 2.7 to 3.3, the nickel concentration is 2 g/L to 5 g/L, and the cobalt concentration is 0.1 g/L to 1.0 g/L. A sulfuric acid solution containing, for example, iron, magnesium, manganese, and aluminum as impurity metals.

The impurity metals vary greatly depending on the oxidation-reduction potential (ORP) in the leaching process, the operating conditions of the autoclave, and the grade of ore. It is contained at a rate of about several g/L.

Here, impurity metals such as iron, magnesium, manganese, and aluminum contained in the sulfuric acid solution of the mother liquor for recovering nickel are present in relatively large amounts relative to the nickel to be recovered, but are generated by the sulfurization treatment in the sulfurization step S4. Low stability as a sulfide. Therefore, these impurity metals are not included in the sulfide produced by the sulfurization reaction, but are included in the post-sulfidation liquid obtained by removing the produced sulfide. The post-sulfurization solution is an acidic solution having a pH of about 1.0 to 3.0.

In this way, in the sulfurization step S4, nickel sulfide with a low impurity content and a post-sulfurization solution in which the nickel concentration is stabilized at a low level are produced and recovered respectively. As a recovery method, the sulfide slurry obtained by the sulfurization treatment is sedimented and separated using a sedimentation separation device such as a thickener, so that the sulfide as a precipitate is separated and recovered from the bottom of the thickener, and the aqueous solution component overflows and is recovered as a post-sulfidation liquid.

≪3. Neutralization method≫
The post-sulfidation solution, which is an acidic solution obtained through the sulfurization step S4 in the nickel oxide ore hydrometallurgical process, contains ions of impurity metals including at least iron, magnesium, manganese, and aluminum, as described above. Therefore, when the post-sulfurization solution is discharged out of the system, it is necessary to carry out a neutralization treatment to remove residual metal ions in the post-sulfurization solution. Further, even when the post-sulfided liquid is repeatedly used in the hydrometallurgical process described above, it is preferable to carry out a neutralization treatment in order to reduce the impurity components as much as possible.

Therefore, in the nickel oxide ore hydrometallurgical process, the post-sulfidation liquid obtained through the sulfurization step S4 is subjected to neutralization treatment (final neutralization treatment) to remove impurity metals such as iron, magnesium, manganese, and aluminum. ) has a final neutralization step S5. In the final neutralization step S5, the acidic slurry containing the leaching residue from the solid-liquid separation step S2 is also treated.

FIG. 2 is a process diagram showing an example of the flow of neutralization processing in the final neutralization step S5. Specifically, in the neutralization treatment method in the final neutralization step S5, a first neutralizing agent is added to the post-sulfidation solution, which is a sulfuric acid solution, and the neutralization treatment is performed with a predetermined pH range as the end point. 1 neutralization treatment step S51, and neutralization treatment is performed by adding a second neutralizing agent to the solution after neutralization treatment in the first neutralization treatment step S51, and precipitates containing impurity metals are obtained. and a second neutralization step S52 for generating a post-neutralization liquid.

As described above, the neutralization treatment method in the final neutralization step S5 is characterized by performing a stepwise neutralization treatment consisting of two stages.

Then, in the neutralization treatment method comprising the first neutralization treatment step S51 and the second neutralization treatment step S52, each neutralization treatment is performed using a plurality of reaction vessels connected in series, and each reaction An oxidant is supplied to the tank, and pure oxygen is supplied as the oxidant only to the most upstream reaction tank where the neutralization treatment in the second neutralization treatment step S52 is performed. and

<3-1. Regarding the first neutralization treatment step>
In the first neutralization treatment step (also simply referred to as the “first step”) S51, a first neutralizing agent is added to the post-sulfurization solution, and the pH range is from 5.0 to 6.0. Apply sum processing. Note that in the neutralization treatment in the first step S51, mainly iron and aluminum are precipitated as hydroxides.

As the first neutralizing agent, for example, a weakly alkaline neutralizing agent such as calcium carbonate slurry is used. Calcium carbonate slurry is an inexpensive neutralizing agent. Therefore, by using this inexpensive calcium carbonate slurry as the first neutralizing agent and first performing the first-stage neutralization treatment, while effectively separating the impurity metals as precipitates, the second-stage It is possible to effectively reduce the amount of a more basic and expensive neutralizer such as slaked lime slurry used in the neutralization treatment (second neutralization treatment step S52).

Then, in the stepwise neutralization treatment in the first step S51, the pH at the end point is set in the range of 5.0 to 6.0. The end point is preferably in the range of 5.3 to 5.8, more preferably in the range of 5.5 to 5.7.

Thus, in the neutralization treatment in the first step S51, calcium carbonate slurry or the like is used as the first neutralizing agent, and the pH at the end point is set and adjusted to 5.0 to 6.0. By performing the neutralization treatment, it is possible to separate and remove impurity metals while effectively reducing the amount of an effective neutralizing agent such as slaked lime slurry used. In addition, by appropriately adjusting the pH at the end point to the range described above, the total amount of the neutralizing agent used in the entire neutralization treatment can be reduced, and efficient neutralization treatment with reduced treatment costs can be performed. .

Regarding the pH of the end point in the first neutralization treatment, if the pH is less than 5.0, the neutralization treatment in the first step S51 will be insufficient, and the neutralization treatment in the second neutralization treatment step S52 described later will The sum processing load increases, resulting in an increase in the usage of the second neutralizing agent (eg, slaked lime slurry). On the other hand, when the pH at the end point exceeds 6.0, the load of the neutralization treatment in the first step S51 increases, and the usage amount of the first neutralizing agent such as calcium carbonate slurry increases. In addition, even if the pH of the end point is adjusted to exceed 6.0 to intentionally increase the load of the neutralization treatment in the first step S51, the second medium in the second neutralization treatment step S52 Since the amount of admixture used remains almost the same, the amount of neutralizing agent used increases throughout the neutralization process, resulting in economic inefficiency.

The pH measurement of the solution can be performed using a well-known method, and the end point of the neutralization treatment can be determined based on the measured pH. Also, the amount of the neutralizing agent to be added can be adjusted based on the measured pH value. Specifically, for example, a pH measuring meter is installed inside a launder trough or the like that connects a plurality of reaction tanks connected in series to overflow the treatment liquid, and the pH of the solution can be measured at any time. and Then, the pH, which changes with the progress of the neutralization reaction accompanying the addition of the neutralizing agent, is observed to determine the end point of the neutralization treatment. Also, the amount of the neutralizing agent to be added is appropriately adjusted.

<3-2. Regarding the second neutralization treatment step>
In the second neutralization treatment step (also simply referred to as the “first step”) S52, the solution after the neutralization treatment in the first step S51 is treated with the first medium as the second neutralizer. Neutralization treatment is performed by adding a neutralizing agent having higher basicity than the admixture. A precipitate containing impurity metals and a post-neutralization liquid from which impurity metals have been removed are produced by the neutralization treatment in the second step S52. In addition, in the neutralization treatment in the second step S52, manganese is preferentially and selectively used as precipitates.

As described above, the second neutralizing agent is a neutralizing agent having a higher basicity than the first neutralizing agent such as calcium carbonate slurry, and for example, slaked lime slurry can be used. Slaked lime slurry is a strong alkaline neutralizing agent and is relatively expensive.

In this neutralization treatment method, a stepwise neutralization treatment is performed, and a neutralizing agent such as calcium carbonate slurry is used in the neutralization treatment in the first step S51, and a predetermined pH range is the end point. Since the neutralization treatment is performed, the amount of relatively expensive neutralizing agent such as slaked lime slurry used in the neutralizing treatment in the second step S52 can be effectively reduced.

In the neutralization treatment in the second step S52, it is preferable to adjust the end point pH range to pH 8.5 to 9.0. If the pH at the end point of this neutralization treatment is less than 8.5, the precipitates of the impurity metals contained in the post-sulfidation liquid are not sufficiently formed, and the impurity metal ions remain in the post-neutralization liquid. there is a possibility. In particular, manganese precipitate formation may be insufficient. On the other hand, when the end-point pH exceeds 9.0, the formation of precipitates of impurity metals does not proceed any further, and the load of the neutralization treatment increases, and the amount of the second neutralizing agent such as slaked lime slurry used increases. It will increase and economic efficiency will worsen. Also, magnesium tends to co-precipitate, which may also increase the amount of neutralizing agent used.

In particular, in this neutralization method, pure oxygen is supplied as an oxidizing agent only to the most upstream reaction vessel in the neutralization treatment in the second step S52. When the target is less than 1 mg/L, manganese can be effectively removed in the pH range of 8.5 to 9.0, and the upper limit of pH can be lowered more than the conventional method. As a result, magnesium contained in the solution can be effectively prevented from forming precipitates together with manganese, and as a result, the amount of the neutralizing agent used can be reduced. Details of the supply of the oxidizing agent will be described later.

The pH control of the neutralization treatment in the second step S52 can also be performed by the same method as the pH control in the first step S51.

Here, as described above, the neutralization treatment is performed in two stages of the first step S51 and the second step S52, and furthermore, by controlling the addition of the oxidizing agent, the neutralizing agent such as high-cost slaked lime slurry Although the amount of (second neutralizing agent) used can be reduced, it is desirable to further reduce the amount of the second neutralizing agent used. At this time, the second neutralizing agent such as slaked lime slurry used in the second step S52 has a solid concentration (% Solid) in the range of 10% to 18%. Thus, by adjusting the solid concentration to a specific range and using it as the second neutralizing agent, the amount of loss of the neutralizing agent used can be reduced. That is, since the second neutralizing agent such as slaked lime slurry can be effectively used while reducing loss, the amount used can be further reduced, and more efficient treatment can be performed.

<3-3. Neutralization equipment>
Here, FIG. 3 is a schematic diagram showing a configuration example of a neutralization treatment facility composed of a plurality of reaction tanks for performing neutralization treatment. The neutralization treatment facility 1 performs the neutralization treatment in the first step S51 in two reaction tanks (the first reaction tank 11 and the second reaction tank 12), and the neutralization treatment in the second step S52 in two reaction tanks. It is a facility configured to perform in reaction tanks (third reaction tank 13 and fourth reaction tank 14).

As shown in FIG. 3, the neutralization treatment in the first step S51 is performed using a plurality of reaction vessels (11, 12) connected in series. Likewise, the neutralization treatment in the second step S52 is performed using a plurality of reaction vessels (13, 14) connected in series. Further, the most downstream reaction tank (second reaction tank 12) for performing the neutralization treatment in the first step S51 and the most upstream reaction tank for performing the neutralization treatment in the second step S52 The tank (the third reaction tank 13) is connected to each other to maintain continuity. Thus, the first to fourth reaction vessels 11 to 14 are connected in a single line.

The number of reaction tanks to be installed is not limited to four tanks, two tanks in total, as in the example of FIG. are configured to be executed in a plurality of reactors, respectively.

(Neutralization treatment in the first step S51)
The first reaction tank 11 is the first neutralization reaction tank positioned most upstream in the single series, and is the reaction tank in which the neutralization treatment in the first step S51 is performed. In the first reaction tank 11, an acidic solution to be treated (a post-sulfidation solution) is charged, and a first neutralizing agent (for example, calcium carbonate slurry) is added to the acidic solution. of impurity metal hydroxides.

The first reaction tank 11 is provided, for example, at its upper portion with a charging port for charging the acidic solution to be neutralized into the tank, and an inside for adding the first neutralizing agent. A soothing agent addition port is provided. Furthermore, the first reaction tank 11 is provided with an oxidant supply port for supplying an oxidant for accelerating the neutralization reaction. Air, for example, is supplied from a blower to the first reaction tank 11 as an oxidant. The details of the supply of the oxidant will be described later.

The slurry to which the first neutralizing agent has been added in the first reaction tank 11 overflows and is fed into the second reaction tank 12, and the neutralization treatment in the first step S51 is continued. The second reaction tank 12 is provided with at least an oxidant supply port for supplying an oxidant, and air, for example, is supplied as the oxidant.

The first reaction vessel 11 and the second reaction vessel 12 are connected at the upper ends of each other, for example, by a launder gutter 21, and from the first reaction vessel 11 to the second reaction vessel 12, via the launder gutter 21, The slurry overflows and is transported.

Further, for example, a pH meter for measuring the pH of the transferred solution can be provided inside the launder gutter 21 (the position through which the solution passes). Then, the pH of the solution measured by the pH meter is monitored, the addition of the first neutralizing agent is adjusted, and the neutralization treatment is performed with the range of pH 5.0 to 6.0 as the end point. In addition, you may provide in the reaction tanks 11 and 12 about a pH meter.

(Neutralization treatment in the second step S52)
The third reaction tank 13 is a reaction tank in which the neutralization treatment in the second step S52 is performed. That is, it is the most upstream reaction vessel for the neutralization treatment in the second step S52. In the third reaction tank 13, the solution after the neutralization treatment in the first step S51 is supplied from the second reaction tank 12, and a second neutralizing agent (for example, slaked lime slurry) is added to the solution. , mainly manganese is preferentially precipitated as hydroxide.

A launder gutter 22 is connected between the third reaction vessel 13 and the second reaction vessel 12, and the flow rate from the second reaction vessel 12 to the third reaction vessel 13 in the first step S51 is The solution after the summing process overflows and is transferred. In addition, the third reaction tank 13 is provided, for example, at its upper portion with a neutralizing agent addition port for adding the second neutralizing agent.

Furthermore, the third reaction tank 13 is provided with an oxidant supply port for supplying an oxidant for accelerating the neutralization reaction. Here, pure oxygen is supplied to the third reaction tank 13 as an oxidant. Although details will be described later, in the neutralization treatment facility 1 composed of a plurality of reaction vessels 11 to 14, in the third reaction vessel 13, which is the most upstream reaction vessel for performing the neutralization treatment in the second step S52, Only pure oxygen is supplied as the oxidant. As a result, the oxidation-reduction potential of the solution can be more effectively controlled within an appropriate range, and manganese can be preferentially precipitated. This suppresses the coprecipitation of magnesium and contributes to the reduction of the amount of the neutralizing agent used. Furthermore, since pure oxygen is supplied only to the third reaction tank 13, the cost of the oxidizing agent can be effectively reduced, and the neutralization treatment can be carried out economically and with high efficiency.

The slurry added with the second neutralizing agent in the third reaction tank 13 overflows and is sent into the fourth reaction tank 14, and the neutralization treatment in the second step S52 is continued. The fourth reaction tank 14 is provided with at least an oxidant supply port for supplying an oxidant, and air, for example, is supplied as the oxidant.

The third reaction vessel 13 and the fourth reaction vessel 14 are connected at the upper ends of each other, for example, by a launder gutter 23, and from the third reaction vessel 13 to the fourth reaction vessel 14, via the launder gutter 23, The slurry overflows and is transported.

Further, for example, a pH meter for measuring the pH of the transferred solution can be provided inside the launder gutter 23 (the position through which the solution passes). Then, the pH of the solution measured by a pH meter is monitored, the addition of the second neutralizing agent is adjusted, and the neutralization treatment is preferably carried out with the pH range of 8.5 to 9.0 as the end point. In addition, the pH meter may be provided in the reaction tanks 13 and 14 .

<3-4. About Addition of Oxidizing Agent>
As described above, in the neutralization treatment method, each of the neutralization treatments in the first step S51 and the second step S52 is performed in a plurality of reaction tanks (first reaction tank 11 to the fourth reactor 14).

Further, the neutralization treatment in each reaction tank (11 to 14) is performed by supplying an oxidizing agent.

For example, the iron contained in the acidic solution (the post-sulfidation solution) to be neutralized becomes a precipitate of iron hydroxide by the addition of a neutralizing agent. The iron in the solution contains both divalent iron and trivalent iron, respectively divalent iron hydroxide (II) (Fe(OH) ₂ ), trivalent iron hydroxide (III) Precipitates as (Fe(OH) ₃ ). However, although trivalent iron(III) hydroxide (Fe(OH) ₃ ) precipitates at low pH, divalent iron(II) hydroxide (Fe(OH) ₂ ) precipitates at low pH. hard to do Therefore, trivalent iron is precipitated as Fe(OH) ₃ by the neutralization treatment in the first step S51 in which the pH of the solution is low, and divalent iron is in a second step in which the pH is high. Fe(OH) ₂ is precipitated by the neutralization treatment in step S52.

As described above, in the neutralization treatment in the second step S52, a second neutralizing agent (for example, slaked lime slurry, etc.) having a higher basicity than the first neutralizing agent is used in order to raise the pH. are using. However, when the amount of divalent iron to be treated in the second step S52 increases, the amount of the second neutralizing agent such as slaked lime slurry must be increased in order to maintain the pH at a high state. The slaked lime slurry is more expensive than the neutralizing agent such as limestone slurry used in the neutralization treatment in the first step S51. A smaller number is preferable. That is, it is desirable to treat iron contained in the acidic solution to be neutralized in the first step S51 as much as possible in the first step S51.

In order to increase the amount of iron to be treated in the first step S51, divalent iron contained in the acidic solution to be treated should be replaced with trivalent iron. Therefore, in this neutralization treatment method, bivalent iron is oxidized to trivalent iron by supplying an oxidizing agent to the solution to be treated. For example, by blowing air as an oxidizing agent into the reaction tank, the oxygen in the air is brought into contact with divalent iron to oxidize it into trivalent iron.

Here, the post-sulfidation solution (acidic solution) to be neutralized contains at least manganese, magnesium, and aluminum in addition to iron. Iron, which forms precipitates mainly in the neutralization treatment in the first step S51, can be sufficiently oxidized by an oxidizing agent such as air. It is preferable to supply an oxidizing agent having a high oxidizing power, and it is particularly preferable to supply pure oxygen. Manganese, which is an impurity element, becomes a precipitate in the neutralization treatment in the second step S52.

Therefore, in this neutralization treatment method, pure oxygen is supplied as an oxidizing agent only to the most upstream reaction tank (third reaction tank 13) in the neutralization treatment in the second step S52. . In the first reaction tank 11 and the second reaction tank 12 for the neutralization treatment in the first step S51, and also in the fourth reaction tank 14 for the neutralization treatment in the second step S52, oxidation Pure oxygen may be supplied as an agent, but the processing cost (oxidant cost) increases. For this reason, pure oxygen is used as an oxidizing agent only in the most upstream reaction tank (third reaction tank 13) where the neutralization treatment in the second step S52 is performed.

As a result, the cost of the oxidizing agent in the entire neutralization process can be effectively reduced, and the oxidation-reduction potential for oxidizing manganese can be adjusted appropriately and effectively, and impurity elements, especially manganese, can be preferentially selected. can be separated and removed as a precipitate.

In addition, by supplying pure oxygen as an oxidizing agent only to the most upstream reaction tank (third reaction tank 13) in the neutralization treatment in the second step S52, the manganese concentration in the solution is reduced to less than 1 mg/L. When aiming to achieve, manganese can be effectively removed in the range of pH 8.5 to 9.0, and the upper limit of pH is lower than the conventional method (upper limit of pH 9.5). can be done. As a result, precipitation of magnesium contained in the solution together with manganese can be effectively suppressed, and as a result, the amount of the neutralizing agent used can be reduced.

The method of supplying pure oxygen to the third reaction tank 13 is not particularly limited, but it is preferable to blow the oxygen gas supplied from a cylinder into the solution in the tank through sintered glass, a pipe, or the like. . This allows pure oxygen to dissolve efficiently into the solution.

The oxidizing agent supplied to the first reaction tank 11 and the second reaction tank 12 in which the neutralization treatment is performed in the first step S51 and the fourth reaction tank 14 in which the neutralization treatment is performed in the second step S52 Although not particularly limited, the above air, ozone, peroxide, sulfur dioxide, or the like can be used, for example. Among them, the use of air is preferable because it can further reduce the cost.

Specifically, in the neutralization treatment in the second step S52, the oxidation-reduction potential (based on Ag/AgCl) of the solution in the most upstream reaction tank (third reaction tank 13) is in the range of -100 mV to +300 mV. It is preferable to By supplying pure oxygen as an oxidizing agent, the redox potential can be efficiently controlled within such a range. Thus, by supplying pure oxygen as an oxidizing agent to the third reaction tank 13 for neutralization treatment, manganese in the solution can be effectively oxidized and preferentially formed into a precipitate. can be separated and removed. That is, manganese can be selectively precipitated while suppressing coprecipitation of magnesium. The ability to suppress the coprecipitation of magnesium in this way contributes to reducing the amount of the second neutralizing agent such as slaked lime slurry used.

If the redox potential is less than -100 mV, the oxidation of manganese may be insufficient and preferential precipitate formation may not be achieved. Increases the amount of neutralizer used. In addition, along with this, the amount of coprecipitation of magnesium may also increase. On the other hand, when the redox potential exceeds +300 mV, preferential precipitation of manganese is achieved, but a large amount of pure oxygen is required and the cost of the oxidant increases. Moreover, the effect of forming manganese precipitates is not increased further, and efficiency may be reduced. Furthermore, if the solution contains chromium, the chromium may be in the hexavalent form, which is not preferred.

The amount of pure oxygen supplied to the third reaction tank 13 may be any amount necessary to oxidize manganese ions in the solution from divalent to trivalent. In addition, regarding the supply amount of pure oxygen, since the above-mentioned redox potential range of -100 mV to +300 mV is the region where manganese ions change from divalent to trivalent, the redox potential is used as a guideline for adjustment. be able to. Alternatively, the solution may be sampled and the manganese ion valence may be controlled by chemical analysis.

As described above, in the neutralization treatment method, each of the neutralization treatments in the first step S51 and the second step S52 is performed in a plurality of reaction tanks (first reaction tank 11 to the fourth reaction vessel 14), and an oxidizing agent is supplied to each reaction vessel (11 to 14). Among them, pure oxygen is supplied as an oxidant only to the most upstream reaction tank (third reaction tank 13) in the neutralization treatment in the second step S52.

According to such a method, harmful elements can be selectively and effectively separated and removed from an acidic solution containing iron, manganese, magnesium, and aluminum, and the amount of consumption of the neutralizer can be reduced. Cost can be effectively reduced, and efficient processing can be performed.

≪4. Al/Mg ratio of nickel oxide ore>>
As described above, the neutralization treatment method according to the present invention can be applied to treatment in the final neutralization step (step S5 in the process diagram of FIG. 1) in the nickel oxide ore hydrometallurgical process. In that case, the acidic solution to be treated is a post-sulfurized solution obtained by adding a sulfiding agent to the leachate obtained through a leaching treatment of leaching nickel from nickel oxide ore using sulfuric acid and performing a sulfurizing treatment. becomes liquid. Note that iron, manganese, magnesium, and aluminum are metals that remain in the solution after sulfiding through the hydrometallurgical process of nickel oxide ore.

Here, as the post-sulfidation liquid to be neutralized, a slurry of nickel oxide ore having a ratio of aluminum grade to magnesium grade (Al/Mg ratio) of less than 2.0 is used as a raw material, and hydrometallurgy is used from the raw material. It is preferable to use those obtained through processes.

According to the research of the present inventor, regarding the ratio of aluminum grade to magnesium grade (Al/Mg ratio) in the nickel oxide ore that is the raw material of the hydrometallurgical process, if the Al/Mg ratio is less than 2.0, aluminum It was found that the coprecipitation effect of and magnesium is reduced. For this reason, the post-sulfidation liquid obtained by performing the hydrometallurgical process using such a nickel oxide ore having an Al / Mg ratio of less than 2.0 as a raw material is subjected to neutralization treatment (final neutralization treatment) , the amount of the neutralizing agent (especially the second neutralizing agent) used can be further reduced. On the other hand, when the Al/Mg ratio is high, coprecipitation of manganese and magnesium occurs as a result of oxidizing manganese with pure oxygen, which leads to an increase in the amount of neutralizing agent used.

In general, adjusting the pH of a solution containing aluminum ions to a range of 4.0 to 6.0 results in the formation of aluminum hydroxide and a precipitate. After that, when the pH is raised to the range of 7.0 to 8.0, the precipitate stably exists in the form of a simple aluminum hydroxide precipitate represented by [Al(OH) ₃ ]. Instead, it exists in a metastable state as a hydrotalcite-type compound (aluminum composite hydroxide) in which coexisting divalent metal ions such as magnesium ions are incorporated in the form of a basic double salt. Such a metastabilized state consumes an excess of the neutralizing agent.

From this, when the Al / Mg ratio in the nickel oxide ore is low (preferably less than 2.0), that is, the magnesium grade is high, the added in the leaching step (S1) in the hydrometallurgical process Sulfuric acid is used preferentially for magnesium to keep the aluminum leaching rate low. Furthermore, since the concentration of aluminum in the leachate is kept low, the concentration of aluminum in the post-sulfurization liquid produced in the sulfurization step (S4) also becomes low. From this, in the neutralization treatment for the post-sulfidation solution with a low aluminum concentration, the formation of precipitates in the hydrotalcite type compound (aluminum composite hydroxide) is suppressed, and as a result, the neutralizing agent is used. It is possible to reduce the amount used.

The aluminum grade and magnesium grade in the nickel oxide ore (ore slurry) refer to the respective grades (content ratios) of aluminum and magnesium in the solid content in the ore slurry. For example, the aluminum grade in the solid content in the ore slurry composed of nickel oxide ore such as laterite ore is usually in the range of about 2.0% by mass to 3.5% by mass, and the magnesium grade is usually in the range of 0.5% by mass. It is in the range of about 8% by mass to 1.8% by mass. Therefore, in general, the Al/Mg ratio of ore slurry is in the range of about 1.2 to 4.0.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<<Examples and Comparative Examples>>
<About processing operations>
[Example 1]
Along the process diagram of the hydrometallurgical process shown in FIG. 1, the post-sulfidation liquid (acidic solution) discharged when producing nickel sulfide from the nickel oxide ore as a raw material is separated in the solid-liquid separation step S2. In the final neutralization step S5, a neutralization treatment was performed on the mixed solution with the leached residue obtained.

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, and the obtained leaching slurry is subjected to a solid-liquid separation step S2. Solid-liquid separation separated into a leachate and a leach residue.

Next, in the neutralization step S3, a pH adjuster is added to the leachate to form precipitates of impurity elements, which are separated and removed in the form of a slurry of precipitates to remove nickel and cobalt, which are valuable metals, as well as impurities. A mother liquor (precious liquor) for recovering nickel was obtained from a sulfuric acid solution containing iron, magnesium and manganese as metal ions.

Next, in the sulfurization step S4, hydrogen sulfide gas was blown into the obtained mother liquor to produce sulfides containing nickel. The generated sulfide was recovered by solid-liquid separation using a filter press, and the liquid after sulfiding was discharged as the liquid phase side.

Then, the post-sulfurization liquid discharged in this way is recovered, the post-sulfurization liquid is mixed with the leaching residue separated in the solid-liquid separation step S2, and in the final neutralization step S5, the solution is subjected to , A two-stage neutralization treatment consisting of a first neutralization treatment step (first step) S51 and a second neutralization treatment step (second step) S52 was performed (see the process diagram in FIG. reference). As a result, impurity metal ions contained in the post-sulfurization liquid were neutralized and removed to obtain a post-neutralization liquid.

The post-sulfidation liquid to be neutralized in the final neutralization step S5 has a pH of 1 to 3, 1 to 4 g/L of iron, 1 to 3 g/L of aluminum, 1 to 3 g/L of manganese, and 1 to 3 g/L of nickel. It was a solution containing 0.05 to 0.2 g/L and magnesium at a concentration of 1 to 6 g/L.

In the final neutralization step S5, in the two-step neutralization treatment of the first step S51 and the second step S52, a total of four reactors each consisting of two reactors connected in series were used. It was carried out continuously using tanks (first reaction tank 11 to fourth reaction tank 14). The treated liquid (post-treated liquid) treated in each reaction tank (11 to 14) was transferred to the adjacent downstream reaction tank by overflow through launder troughs (21, 22, 23).

In the neutralization treatment in the first step S51, calcium carbonate slurry was used as the first neutralizing agent, and the neutralizing agent was added until the pH of the post-sulfidation solution to be treated reached 5.0 (end point pH). . Moreover, in the neutralization treatment in the second step S52, a slaked lime slurry (slaked lime slurry concentration: 22% by mass) was added as the second neutralizing agent.

In addition, a pH meter is provided in the launder gutter through which the post-treatment liquid flows, and based on the pH value measured by the pH meter, the opening of the flow control valve provided in the addition pipe of the neutralizing agent to be added to the reaction tank in the preceding stage is adjusted. controlled to adjust the amount of neutralizer added. That is, in the first step S51, the addition amount of the first neutralizing agent to be added to the first reaction tank 11 was adjusted based on the pH value of the processing liquid overflowing from the second reaction tank 12. Further, in the second step S52, the addition amount of the second neutralizing agent to be added to the third reaction tank 13 was adjusted based on the pH value of the treatment liquid overflowing from the fourth reaction tank 14. The treated liquid extracted from the fourth reaction vessel 14 due to overflow was supplied to the subsequent solid-liquid separation device via a pump.

In addition, neutralization treatment was performed by supplying an oxidizing agent to each reaction vessel. Specifically, the first reaction tank 11 and the second reaction tank 12 for the neutralization treatment in the first step S51, and the fourth reaction tank 14 for the neutralization treatment in the second step S52. was supplied with air as an oxidant. On the other hand, pure oxygen (100% oxygen) was supplied as an oxidizing agent to the third reaction tank 13 where the neutralization treatment in the second step S52 was performed. That is, pure oxygen was supplied as an oxidizing agent only to the third reaction tank 13, which is the most upstream reaction tank for the neutralization treatment in the second step S52.

Then, while supplying pure oxygen at a flow rate of 0.5 liters per minute to the solution after treatment in the second reaction tank 12 so that the oxidation-reduction potential (based on Ag/AgCl) is −50 mV to +50 mV, 15 The solution was stirred for 1 minute, and a second neutralizing agent, slaked lime slurry, was added to adjust the pH of the solution to a range of 8.0 to 9.5.

[Comparative Example 1]
In Comparative Example 1, air was supplied as an oxidizing agent to all of the four reaction tanks, ie, the first reaction tank 11 to the fourth reaction tank 14, and a two-stage neutralization treatment was performed. It was processed in the same manner as in Example 1.

<Results of neutralization treatment>
The solutions after the neutralization treatment in Example 1 and Comparative Example 1 described above were recovered, and the concentration of impurities in the solutions was analyzed. The analysis results are shown in Table 1 below.

As shown in Table 1, in both Example 1 and Comparative Example 1, impurity metals such as iron, manganese and aluminum could be precipitated and separated and removed. That is, the manganese concentration in the waste water after neutralization treatment was reduced to less than 1 mg/L, and the concentration of other heavy metals was also reduced to less than 1 mg/L.

However, in Comparative Example 1, the magnesium concentration was 400 mg/L, which was lower than in Example 1. This means that in the treatment of Comparative Example 1, the oxidation reaction of manganese was insufficient and preferential precipitate formation did not occur, and the amount of slaked lime slurry used as a neutralizing agent had to be increased. As a result, the coprecipitation amount of magnesium in the solution increased. This result is presumed to be due to the use of air as the oxidizing agent supplied to the third reaction vessel 13 for the neutralization treatment in the second step S52.

On the other hand, in Example 1, by supplying air as an oxidizing agent only to the third reaction tank 13, the amount of the neutralizing agent used can be effectively reduced while reducing the cost of using the oxidizing agent. Efficient neutralization treatment was able to be carried out by suppressing the amount of co-precipitation of magnesium.

FIG. 4 is a graph showing measurement results of the manganese concentration in the solution with respect to pH when the neutralization treatment in the second step S52 is performed.

As shown in the results of FIG. 4, in Example 1 in which pure oxygen was supplied as an oxidizing agent to the third reaction tank 13, which is the most upstream reaction tank for the neutralization treatment in the second step S52, low It can be seen that the concentration of manganese in the solution has already been reduced at the pH stage. In other words, manganese was preferentially precipitated and separated. This is probably because the supply of pure oxygen as an oxidizing agent enabled efficient and effective control of the redox potential in the solution.

As described above, since pure oxygen is supplied only to the third reaction vessel 13, it is possible to effectively suppress an increase in the cost of using the oxidizing agent.

≪Verification of the Al/Mg ratio of nickel oxide ore≫
[Example 2]
As raw material ore slurry in the nickel oxide ore hydrometallurgical process shown in the process diagram in FIG. , and the post-sulfidation liquid was recovered from the raw materials through the hydrometallurgical process.

After that, as the final neutralization step S5, in the same manner as in Example 1, the post-sulfurized liquid was subjected to a two-stage neutralization treatment.

The post-sulfidation liquid to be neutralized has a pH of 1 to 3, and contains 1 to 4 g/L of iron, 1 to 3 g/L of aluminum, 1 to 3 g/L of manganese, and 0.05 to 0.05 g/L of nickel. It was a solution containing 2 g/L and magnesium at a concentration of 1 to 6 g/L.

FIG. 5 is a graph showing measurement results of the concentration of residual magnesium in the solution with respect to pH when the neutralization treatment in the second step S52 was performed on the post-sulfidation solution obtained using ores having different Al/Mg ratios. is.

As shown in the results of FIG. 5, it can be clearly seen that the concentration of residual magnesium in the solution after the neutralization treatment differs depending on the Al/Mg ratio in the ore that is the raw material in the hydrometallurgical process. In particular, when the Al/Mg ratio is less than 2.0, the residual amount of magnesium is large in the range of pH 9.0 or lower, ie, coprecipitation with other impurity metals such as manganese can be suppressed.

Also, Table 2 below shows the results of the amount of magnesium and precipitation reduction when the manganese concentration in the solution was 1 mg/L, and the amount of reduction of the slaked lime slurry used as the second neutralizing agent.

As shown in Table 2, the post-sulfidation liquid obtained through the hydrometallurgical process using an ore having an Al/Mg ratio of less than 2.0 as a raw material can effectively reduce the amount of slaked lime slurry added. , was found to be able to suppress the formation of magnesium precipitates.

1 Neutralization treatment facility 11 First reaction tank 12 Second reaction tank 13 Third reaction tank 14 Fourth reaction tank 21, 22, 23 Launder gutter S1 Leaching process S2 Solid-liquid separation process S3 Neutralization process S4 Sulfurization Step S5 Final neutralization step S51 First neutralization treatment step (first step)
S52 Second neutralization treatment step (second step)

Claims (7)

A neutralization treatment method for an acidic solution containing at least iron, manganese, magnesium, and aluminum,
a first step of adding a first neutralizing agent to the acidic solution and performing a neutralization treatment with a pH range of 5.0 to 6.0 as an end point;
a second step of neutralizing the solution by adding a second neutralizing agent having a higher basicity than the first neutralizing agent to the solution after the neutralization treatment in the first step; has
The neutralization treatment of each of the first step and the second step is performed by using a plurality of reaction vessels connected in series and supplying an oxidant to each reaction vessel,
A neutralization treatment method, wherein pure oxygen is supplied as the oxidizing agent only to the most upstream reaction tank where the neutralization treatment in the second step is performed. Neutralization according to claim 1, wherein in the second step, the pure oxygen is supplied so that the oxidation-reduction potential (based on Ag/AgCl) of the solution in the most upstream reaction tank is in the range of -100 mV to +300 mV. Processing method. 3. The method of neutralization treatment according to claim 1, wherein in the second step, the second neutralizing agent is added and the neutralization treatment is performed with a pH range of 8.5 to 9.0 as an end point. The neutralization treatment in the first step is continuously performed using two reaction tanks, the first reaction tank and the second reaction tank, and the neutralization treatment in the second step is performed in the third reaction tank. Continuously using two reaction tanks, the reaction tank of and the fourth reaction tank,
Neutralization according to any one of claims 1 to 3, wherein the pure oxygen is supplied as the oxidant only to the third reaction tank, which is the most upstream reaction tank in the neutralization treatment in the second step. Processing method. As the oxidizing agent, in the first reaction tank and the second reaction tank in the neutralization treatment in the first step, and in the fourth reaction tank in the neutralization treatment in the second step, The neutralization treatment method according to claim 4, wherein air is supplied. 1. The acidic solution is a post-sulfidation solution obtained by adding a sulfiding agent to a leaching solution obtained through a leaching treatment of leaching nickel from nickel oxide ore using sulfuric acid and performing a sulfidation treatment. 6. The neutralization treatment method according to any one of 1 to 5. The neutralization treatment method according to claim 6, wherein the ratio of aluminum grade to magnesium grade (Al/Mg ratio) in the nickel oxide ore is less than 2.0.

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