Method for removing iron and aluminum from lateritic nickel ore leachate by means of goethite process

Abstract

A method for removing iron and aluminum from a lateritic nickel ore leachate by means of a goethite process, which method comprises the following steps: first-stage iron and aluminum removal, involving: adding a precipitant solution to a lateritic nickel ore leachate, reacting same for 45-90 minutes with the feeding speed controlled to be 5-80 mL / min, the pH controlled to be 3.0-3.2 and the reaction temperature controlled to be 60-70ºC, and performing solid-liquid separation, so as to obtain first-stage iron and aluminum residues and a filtrate; and second-stage iron and aluminum removal, involving: adding a precipitant solution to the filtrate, reacting same for 30-60 minutes with the pH controlled to be 4.3-4.4 and the reaction temperature controlled to be 60-70ºC, and performing solid-liquid separation, so as to obtain second-stage iron and aluminum residues and a purified liquid. Two-stage iron and aluminum removal is used; in the first stage, iron ions in the leachate are effectively separated at a relatively low pH value by controlling the feeding speed, generated residue particles are large, good filtering performance is achieved, and few valuable metals such as nickel, cobalt and manganese are entrained in the residues; in the second stage, the pH is adjusted to 4.3-4.4 to precipitate aluminum ions and the remaining iron ions; and the whole technological process is simple.

Description

A method for removing iron and aluminum from laterite nickel ore leachate using a goethite method Technical Field

[0001] The invention belongs to the field of solution purification in hydrometallurgy, and in particular relates to a method for removing iron and aluminum from laterite nickel ore leachate by a goethite method. Background Art

[0002] Since its introduction, pressure leaching technology has been industrially applied in the extraction of metals such as zinc, copper, manganese, and aluminum. Using pressure acid leaching to treat laterite nickel ore offers the advantages of high nickel and cobalt leaching rates and effective separation of iron, aluminum, and nickel and cobalt. Although most of the iron and aluminum are retained in the leaching residue during high-pressure leaching, high-pressure leaching is limited in its effectiveness in suppressing the leaching of iron and aluminum, and some iron and aluminum are inevitably leached into the leachate. Further impurity removal is required to obtain a low-impurity nickel-cobalt (MHP) intermediate.

[0003] Currently, the main methods used for iron removal in China include the ferric hydroxide method, the sodium ferroalloy method, and the goethite method. The sodium ferroalloy method has strict temperature requirements for iron removal, a long alum formation time, and a relatively large amount of sodium ferroalloy residue, and has certain requirements for the concentration of alkali metal ions in the solution. The ferric hydroxide method produces a Fe(OH)3 colloidal precipitate, which is difficult to filter and contains a high content of nickel, cobalt, and manganese metals in the residue, resulting in a certain amount of resource waste. The precipitation method is one of the important wet iron removal methods, and the goethite method is one of the effective iron removal methods.

[0004] Typically, when using the goethite method to remove iron, the ferrous ions in the solution are first oxidized. The temperature is then adjusted to 80-100°C, and a precipitant is added to adjust the pH to 4.0-6.0, allowing the iron ions to precipitate as goethite. The traditional goethite method only adjusts the pH and temperature during the iron and aluminum removal process, and both these high pH and temperature settings can generate ferric hydroxide colloids. This slag is difficult to filter and absorbs large amounts of nickel, cobalt, and manganese, resulting in significant waste of these metals while removing the iron and aluminum impurities.

[0005] In view of this, it is urgent to develop a method that can effectively remove iron and aluminum from laterite nickel ore leachate.

[0006] Summary of the Invention

[0007] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a method for removing iron and aluminum from laterite nickel ore leachate by a goethite method, which combines the goethite method with a neutralization hydrolysis method and is carried out in two stages. By rationally controlling parameters such as pH and feed rate, efficient removal of iron and aluminum impurities is achieved at a lower nickel, cobalt and manganese consumption.

[0008] Goethite-based iron removal typically requires strict control of the system's pH. A high pH easily produces ferric hydroxide colloids, resulting in high nickel losses. A too low pH prevents complete iron removal. The inventors of this application recognized that, in addition to pH, the feed rate also significantly affects the iron and aluminum content of the impurity removal solution. Excessive feed rates can lead to excessively high iron concentrations, generating ferric hydroxide colloids and increasing nickel precipitation losses. Therefore, considering the impact of feed rate, the present invention was developed.

[0009] To achieve the above object, the present invention is implemented through the following technical solutions:

[0010] The present invention provides a method for removing iron and aluminum from laterite nickel ore leachate by a goethite method, comprising the following steps:

[0011] One-stage iron and aluminum removal: add precipitant solution to the laterite nickel ore leachate, control the feed rate to 5-80 mL / min, pH to 3.0-3.2, reaction temperature to 60-70°C, react for 45-90 min, and obtain a first-stage iron and aluminum slag and filtrate after solid-liquid separation;

[0012] Second-stage iron and aluminum removal: add precipitant solution to the filtrate, control the pH to 4.3-4.4, the reaction temperature to 60-70℃, react for 30-60min, separate the solid and liquid, and obtain second-stage iron and aluminum slag and purified liquid.

[0013] Preferably, the laterite nickel ore leachate is an acidic leachate produced by high-pressure acid leaching of the laterite nickel ore, preferably a sulfuric acid leachate.

[0014] The laterite nickel ore leachate may contain a small amount of Fe 2+ In order to ensure the effect of removing iron and aluminum, preferably, before the first stage of removing iron and aluminum, an oxidant is added to the leaching solution to remove Fe 2+ Oxidized to Fe 3+ .

[0015] Preferably, the oxidizing agent is sodium chlorate or air.

[0016] Preferably, when the oxidant is air, a sufficient amount of catalyst Cu 2+ .

[0017] Because a relatively high concentration of sulfuric acid remains in the leachate, it is preferred that the laterite nickel ore leachate be pre-neutralized to a pH of 1.5-2.5 before the first stage of iron and aluminum removal, followed by CCD washing. Pre-neutralization reduces the acid content, resulting in a qualified solution suitable for goethite precipitation. The pre-neutralized solution is then washed with CCD to produce a supernatant and slag. This supernatant is used for goethite precipitation, reducing the amount of neutralizer used during precipitation and preventing excessive nickel, cobalt, and other contents in the slag.

[0018] The pH value of the one-stage iron and aluminum removal of the present invention is relatively low. Preferably, the process further comprises adding the one-stage iron and aluminum slag into the pre-neutralization liquid to adjust the pH value of the one-stage iron and aluminum removal system, thereby reducing the consumption of the precipitant.

[0019] The pH value used in the second-stage iron and aluminum removal is relatively high. Preferably, the second-stage iron and aluminum slag is added to the leachate to pre-neutralize and adjust the pH value of the leachate, which not only reduces the consumption of the precipitant, but also dissolves the nickel and cobalt contained in the residue back into the leachate, thereby improving the separation efficiency of nickel and cobalt.

[0020] Preferably, the precipitant solution is limestone slurry with a mass concentration of 20%.

[0021] Preferably, in the first stage of iron and aluminum removal, the feed rate is 10-50 mL / min, the reaction temperature is 70° C., the pH is 3.1, and the reaction time is 60-90 min.

[0022] Further preferably, in the first stage of iron and aluminum removal, the feed rate is 10 mL / min and the reaction time is 90 min.

[0023] Preferably, in the second stage of iron and aluminum removal, the reaction temperature is 60° C. and the reaction time is 60 min.

[0024] The beneficial effects of the present invention are:

[0025] 1) The goethite method of the present invention removes iron and aluminum by a continuous feeding method and is carried out in two stages. The first stage controls the feed rate to 5-80mL / min, the pH to 3.0-3.2, the reaction temperature to 60-70°C, and the reaction time to 45-90min, so that the iron element is retained in the filter residue as much as possible, thereby improving the iron removal rate; the second stage is a one-way feeding, in which a precipitant solution is added to adjust the pH value to 4.3-4.4, the reaction temperature to 60-70°C, and the reaction time to 30-60min to precipitate aluminum ions and the remaining iron ions. By controlling the feed rate, the present invention realizes the effective separation of iron and aluminum in the leachate at a relatively low pH and temperature. The overall iron and aluminum removal efficiency is high, the slag particles produced are large, the filtration performance is good, and the valuable metals such as nickel, cobalt, and manganese entrained in the slag are small, the iron and aluminum content in the slag is high, and the overall process flow is simple.

[0026] 2) The present invention adds the first-stage iron-aluminum slag to the pre-neutralization solution to adjust the pH value of the first-stage iron-aluminum removal system, thereby reducing the consumption of the precipitant; and by adding the second-stage iron-aluminum slag to the leachate to adjust the pH value of the leachate, not only the consumption of the precipitant is reduced, but also the nickel and cobalt contained in the residue are reversely dissolved into the leachate, thereby improving the separation efficiency of nickel and cobalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments.

[0028] Fig. 1 is a process flow chart of the present invention;

[0029] FIG2 is a graph showing the iron and aluminum content and nickel precipitation rate in the first stage of iron and aluminum removal filtrate at different feed rates;

[0030] FIG3 is a graph showing the iron and aluminum content and nickel precipitation rate in a first stage of iron and aluminum removal filtrate at different pH values;

[0031] FIG4 is a graph showing the iron and aluminum contents and nickel precipitation rate in a first stage of iron and aluminum removal filtrate under different time conditions;

[0032] FIG5 is a graph showing the iron and aluminum content in the purified solution of the second-stage iron and aluminum removal under different pH and time conditions;

[0033] FIG6 is a graph showing the aluminum content in the purified liquid after two-stage iron and aluminum removal under different temperature conditions. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1

[0036] Referring to FIG1 , a method for removing iron and aluminum from a laterite nickel ore leachate using a goethite method according to an embodiment of the present invention comprises the following steps:

[0037] (1) Take 200 mL of the laterite nickel ore leachate after high pressure acid leaching and measure Ni 2+ 4.877g / L, Co 2+ 0.359434g / L, Mn 2+ 2.379g / L, Fe 2+ 7.73g / L, Al 3+ 2.649g / L, Cr 3+ 0.418526 g / L. 20% limestone slurry was added to pre-neutralize the leachate to a pH of 1.5, and then the leachate was washed in the CCD countercurrent to obtain a slag phase and a pre-neutralized liquid. After the slag phase was neutralized, tailings treatment was performed.

[0038] (2) Sodium chlorate solution was added to the reactor to oxidize the divalent iron to trivalent iron, and then a stage of iron and aluminum removal was carried out: 20% limestone slurry was used as a precipitant, the reactor was heated to 70°C, and pre-neutralization liquid and precipitant were added to the reactor in parallel, the feed rate was controlled at 5 mL / min, the pH of the solution in the reactor was 3.1, and after the feed was completed, it was stabilized for 60 minutes, and a stage of iron and aluminum slag and filtrate were obtained after filtration.

[0039] (3) Second stage iron and aluminum removal: Continue to add precipitant solution to the reactor, control the pH of the solution in the reactor to 4.3, the temperature to 60°C, react for 60 minutes, and obtain the second stage iron and aluminum slag and purified liquid after filtration.

[0040] (4) The first stage iron filter residue in step (3) is recycled into the pre-neutralization solution to adjust the pH value of the first stage iron-aluminum removal system; the second stage iron-aluminum residue in step (4) is added into the acid leaching solution for pre-neutralization.

[0041] Examples 2 to 9

[0042] Iron and aluminum removal was performed using the same process as in Example 1, except that the feed rates in the first stage of iron and aluminum removal were 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, and 80 mL / min, respectively. The iron and aluminum contents and nickel precipitation rates in the filtrates from the first stage of iron and aluminum removal in Examples 1-9 are shown in Table 1 and Figure 2.

[0043] Table 1 Effect of different feed rates on the effect of one-stage iron and aluminum removal

[0044] From Table 1 and Figure 2, it can be seen that with the increase of feed rate, the concentration of iron and aluminum in the first stage impurity removal liquid will also increase. In the process of the experiment, it was found that too fast feed rate will lead to slow slurry filtration rate. This may be due to the excessive feed rate causing Fe 3+ Excessive concentrations generate ferric hydroxide colloids. Furthermore, as the feed rate increases, the nickel precipitation loss rate also increases. Comprehensive results show that the present invention achieves a high iron removal rate while retaining the nickel content in the filtrate by controlling the feed rate. In Example 2, when the feed rate is controlled to 10 mL / min, the pH is 3.1, the temperature is 70°C, and the stabilization time is 60 minutes, the highest iron and aluminum removal effect is achieved, while the nickel loss rate is low.

[0045] Examples 10-11

[0046] The iron and aluminum removal was carried out in the same process as in Example 1, except that the pH values ​​in the first stage of the iron and aluminum removal were controlled to be 3.0 and 3.2, respectively.

[0047] Examples 12-13

[0048] The iron and aluminum removal was carried out according to the same process as in Example 2, except that the stabilization time in the iron and aluminum removal stage was controlled to be 45 minutes and 90 minutes respectively.

[0049] Example 14

[0050] The iron and aluminum removal was carried out according to the same process as in Example 1, except that the reaction time in the second stage of iron and aluminum removal was controlled to be 30 min.

[0051] Example 15

[0052] The iron and aluminum removal was carried out in the same process as in Example 1, except that the pH of the system was controlled to be 4.4 in the second stage of iron and aluminum removal.

[0053] Example 16

[0054] The iron and aluminum removal was carried out in the same process as in Example 1, except that the reaction temperature in the second stage of iron and aluminum removal was controlled to be 70°C.

[0055] Comparative Example 1

[0056] Iron and aluminum removal was performed using the same process as in Example 1, except that the pH of the system was controlled at 2.7, 2.9, 3.3, 3.5, 3.7, and 3.9, respectively. The iron and aluminum contents and nickel precipitation rates in the filtrates from the first-stage iron and aluminum removal under different pH conditions are shown in Table 2 and Figure 3.

[0057] Table 2 Effect of different pH on the effect of one-stage iron and aluminum removal

[0058] As can be seen from Table 2 and Figure 3, increasing the pH can improve the removal rate of iron and aluminum. When the pH is 3.0-3.2, most of the iron can be removed, and the iron content in the solution is less than 20 mg / L, which meets production control standards. However, further increasing the pH will significantly increase the precipitation loss rate of nickel. Therefore, the present invention achieves efficient iron removal while reducing nickel loss by simultaneously controlling the feed rate and the pH condition of 3.0-3.2.

[0059] Comparative Example 2

[0060] Iron and aluminum were removed according to the same process as in Example 2, except that the stabilization time in the first stage of iron and aluminum removal was controlled to be 15 min and 30 min, respectively. The iron and aluminum contents and nickel precipitation rates in the filtrate of the first stage of iron and aluminum removal under different time conditions are shown in Table 3 and Figure 4.

[0061] Table 3 Effect of different stabilization times on the effect of one-stage iron and aluminum removal

[0062] As can be seen from Table 3 and Figure 4, as the stabilization time increases, the concentration of iron and aluminum in the impurity removal liquid decreases gradually, and iron reaches stability substantially after 45min. The precipitation rate of nickel also decreases as the stabilization time increases, indicating that nickel will dissolve again as the time increases after precipitation at the beginning. In Comparative Example 2, due to the shorter stabilization time, not only is the iron removal effect poor, but more nickel is also present in the precipitated slag, resulting in serious losses. On the whole, while the present invention controls the stabilization time to be 45-90min and can achieve a higher iron removal rate, a large amount of nickel losses are avoided, wherein the stabilization time is preferably 60-90min, and 90min is the best. Since the present invention also includes recycling a section of iron-aluminum slag for dissolving nickel in the pre-neutralization solution, the stabilization time is selected to be 60min in the actual production process.

[0063] Comparative Example 3

[0064] Iron and aluminum removal was performed using the same process as in Example 1, except that the pH of the system was controlled at 4.1, 4.5, 4.7, and 4.9, respectively, and the reaction time was 30 min and 60 min, respectively. The iron and aluminum contents in the purified solution from the second-stage iron and aluminum removal under different pH and reaction time conditions are shown in Table 4 and Figure 5.

[0065] Table 4 Effect of pH and time on the effect of secondary iron and aluminum removal

[0066] As can be seen from Table 4 and Figure 5, increasing pH and time promotes the precipitation and removal of iron and aluminum, but the loss of nickel and cobalt increases with increasing pH. Compared with Comparative Example 3, the present invention achieves higher iron and aluminum removal while reducing nickel and cobalt precipitation losses by simultaneously controlling the pH to 4.3-4.4 and the reaction time to 30-60 min.

[0067] Comparative Example 4

[0068] Iron and aluminum removal was performed using the same process as in Example 1, except that the system temperatures in the second-stage iron removal were controlled at 40°C and 50°C, respectively. Because the iron element was essentially completely removed in the first-stage impurity removal, this comparative example only tested the aluminum content in the purified solution from the second-stage iron removal at different temperatures, as shown in Table 5 and Figure 6.

[0069] Table 5 Effect of temperature on the effect of secondary aluminum removal

[0070] It can be seen from Table 5 and Figure 6 that as the temperature increases, the concentration of aluminum generally decreases first and then increases. The aluminum removal rate is highest when the temperature is 60-70°C. Therefore, the temperature of the second-stage iron and aluminum removal of the present invention is preferably 60-70°C, more preferably 60°C.

[0071] In summary, the present invention adopts a two-stage iron and aluminum removal process using the goethite method, which improves the efficiency of iron and aluminum removal while also taking into account the precipitation rate of nickel and cobalt. By exploring the feed rate, pH, temperature, and stabilization time in the first stage of iron and aluminum removal, it is found that by simultaneously controlling the feed rate and the appropriate pH, it is possible to achieve higher efficiency iron and aluminum removal while reducing the loss of nickel and cobalt.

[0072] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0073] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for removing iron and aluminum from laterite nickel ore leachate by a goethite method, characterized in that: The following steps are involved: One-stage iron and aluminum removal: add precipitant solution to the laterite nickel ore leaching solution, control the feed rate to 5-80mL / min, pH to 3.0-3.2, reaction temperature to 60-70°C, react for 45-90min, and obtain a first-stage iron and aluminum slag and filtrate after solid-liquid separation; Second stage iron and aluminum removal: add precipitant solution to the filtrate, control the pH value to 4.3-4.4, the reaction temperature to 60-70°C, react for 30-60 minutes, separate the solid and liquid, and obtain second stage iron and aluminum slag and purified liquid.

2. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 1, characterized in that: The laterite nickel ore leaching solution is an acidic leaching solution produced after high-pressure acid leaching of the laterite nickel ore.

3. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 1, characterized in that: Before the first stage of iron and aluminum removal, an oxidant is added to the leaching solution for oxidation.

4. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 3, characterized in that: The oxidant is sodium chlorate or air.

5. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 1, characterized in that: Before the first stage of iron and aluminum removal, the laterite nickel ore leaching solution is pre-neutralized to a pH of 1.5-2.5, and then CCD washing is performed.

6. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 5, characterized in that: The method also includes adding the first-stage iron-aluminum slag into the pre-neutralization liquid to adjust the pH value of the first-stage iron-aluminum removal system.

7. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 1, characterized in that: The method also includes adding the second-stage iron-aluminum slag into the leaching solution to adjust the pH value of the leaching solution.

8. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 1, characterized in that: In the first stage of iron and aluminum removal, the feed rate is 10-50 mL / min, the reaction temperature is 70° C., the pH is 3.1, and the reaction time is 60-90 min.

9. The method for removing iron and aluminum from laterite nickel ore leachate by the goethite method according to claim 8, characterized in that: In the first stage of iron and aluminum removal, the feed rate is 10 mL / min and the reaction time is 90 min.

10. The method for removing iron and aluminum from laterite nickel ore leachate by goethite method according to claim 1, characterized in that: In the second stage of iron and aluminum removal, the reaction temperature is 60°C and the reaction time is 60 minutes.

11. The method for removing iron and aluminum from laterite nickel ore leachate by goethite method according to claim 1, characterized in that: The precipitant solution is limestone slurry with a mass concentration of 20%.

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