A method for desiliconization and silicon recycling in nickel-cobalt hydroxide leaching process

Abstract

The present invention discloses a method for desilication and silicon reuse during the leaching of nickel cobalt hydroxide, belonging to the technical field of hydrometallurgy. The desilication method includes: subjecting nickel cobalt hydroxide to low-acid high-pressure leaching and filtering to obtain a first filter residue and a first filtrate. By converting silicic acid into silicon dioxide under high temperature and high pressure, the present invention transforms the difficult-to-filter silicic acid into easily filterable silicon dioxide, greatly improving the filtration performance of the precipitated impurity silicon, thus solving the problem of the bottleneck in the entire production process flow caused by this process; at the same time, the silicon concentration in the leaching solution can reach below 1 ppm, far exceeding the current situation where the residual silicon in the silicic acid filtration solution is above 50 ppm. In addition, the nickel cobalt hydroxide desilication residue obtained by further high-acid atmospheric pressure leaching has a high purity, and the entrained nickel and cobalt contents are both below 0.01%. Based on this, the present invention further synthesizes a CaO·Li4SiO4 trapping agent, realizing the high-value reuse of the silicon slag.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for desiliconization and silicon recycling in a nickel-cobalt hydroxide leaching process. Background Art

[0002] Nickel cobalt hydroxide (MHP) is an intermediate product of laterite nickel ore hydrometallurgy. Since laterite nickel ore contains a large amount of silicon, some silicon will inevitably be introduced into the nickel cobalt hydroxide product during the hydrometallurgical treatment process. In the subsequent acid leaching process, the silicon entrained in nickel cobalt hydroxide will be leached into the leachate, so effective means are needed to remove it.

[0003] The existing process for removing silicon from nickel-cobalt hydroxide leachate is mainly to remove it by forming silicic acid or silicate precipitation. Existing silicon removal technologies can effectively remove silicon from the solution, but there is also the problem that silicic acid or silicates are difficult to filter, resulting in a large amount of nickel and cobalt being entrained and lost, reducing the effective utilization rate of nickel and cobalt, and significantly prolonging the processing time of the entire process. In addition, the use of separate silicic acid or silicate precipitation to remove silicon, because silicic acid or silicates can be slightly soluble in water, leads to a high level of silicon residue in the liquid after silicon removal, and further deep silicon removal by resin or extraction is required, which increases the processing cost and control difficulty of the entire process. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and propose a method for desiliconization and silicon recycling in the process of nickel cobalt hydroxide leaching, so as to solve the technical problems in the prior art that the silicon removal technology of nickel cobalt hydroxide leaching is difficult to filter, easily leads to a large amount of nickel and cobalt loss, and has a high silicon residue in the liquid after silicon removal.

[0005] In a first aspect, the present invention provides a method for desiliconization during nickel cobalt hydroxide leaching, comprising the following steps: leaching nickel cobalt hydroxide with low acid and high pressure, filtering to obtain a first filter residue and a first filtrate; wherein, during the low acid and high pressure leaching, the pH value during the leaching process is controlled to be maintained at 0.8-2.2, and the leaching temperature is 150-350°C.

[0006] In a second aspect, the present invention provides a method for recycling silicon in the process of nickel cobalt hydroxide leaching, comprising the following steps: a first filter residue obtained by leaching nickel cobalt hydroxide with low acid and high pressure is further leached with high acid and normal pressure to obtain a second filter residue, which is evenly mixed with a lithium source and then calcined at high temperature to obtain a porous CaO·Li4SiO4 adsorbent.

[0007] Compared with the prior art, the beneficial effects of the present invention include:

[0008] The present invention converts the difficult-to-filter silica into easy-to-filter silica by converting silica into silica under high temperature and high pressure, and greatly improves the filtering performance of impure silicon precipitation, thereby solving the current situation that this process causes a bottleneck in the entire production process. The content of nickel and cobalt entrained in the filter residue is significantly reduced, and the silicon concentration in the leachate can reach below 1ppm, which is much better than the current situation where the residual silicon in the solution using silicate filtration is still more than 50ppm. In addition, the nickel-cobalt hydroxide desiliconized slag obtained by high-acid and normal-pressure leaching has a high purity, and the content of entrained nickel and cobalt is both below 0.01%, which can be used as one of the synthetic materials for CO2 capture agents. The present invention further synthesizes CaO·Li4SiO4 capture agents based on this, realizing the high-value utilization of silicon slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The present invention provides a process flow chart of a method for desiliconization and silicon recycling in a nickel-cobalt hydroxide leaching process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0011] See also Figure 1 In the first aspect, the present invention provides a method for desiliconization in the process of nickel cobalt hydroxide leaching, comprising the following steps: low-acid high-pressure leaching: nickel cobalt hydroxide is leached with low-acid high-pressure, and filtered to obtain a first filter residue and a first filtrate. The first filtrate is a nickel-cobalt solution. The low-acid high-pressure leaching process is carried out in a high-pressure reactor. In this step, the pH during the leaching process is controlled to be maintained at 0.8-2.2, including but not limited to 0.8, 1, 1.2, 1.3, 1.5, 1.7, 1.8, 2, 2.2, etc., preferably 1.3-2.2; the leaching temperature is 150-350°C, including but not limited to 150°C, 180°C, 200°C, 250°C, 300°C, 350°C, etc., preferably 180-350°C; the leaching time is 0.5-5h, including but not limited to 0.5h, 1h, 2h , 3h, 4h, 5h, etc. If the leaching time is too short, the leaching is incomplete and the silicon removal effect is poor; if the leaching time is too long, the energy consumption will increase; the leaching solid-liquid ratio is controlled at 50-200g / L, including but not limited to 50g / L, 100g / L, 150g / L, 200g / L, etc. If the solid-liquid ratio is too low, the processing volume will be affected; if the solid-liquid ratio is too high, the slurry viscosity will be too large to affect the leaching process; acid or alkali is used to adjust the pH, the acid used is a common inorganic acid, and the alkali used is calcium oxide or calcium carbonate slurry. After the leaching is completed, the first filtrate is subjected to the subsequent treatment process, and the first filter residue is subjected to the next step of high-acid atmospheric pressure leaching treatment.

[0012] The present invention converts silicic acid into silicon dioxide under high temperature and high pressure, so that the difficult-to-filter silicic acid is transformed into easy-to-filter silicon dioxide, thereby solving the problem that this process causes a bottleneck in the entire production process. After the improved process, the filtration performance of impure silicon precipitation is greatly improved, and the silicon concentration in the leachate can reach less than 1ppm, which is far better than the current situation where the residual silicon in the solution filtered by silicic acid is still more than 50ppm.

[0013] In this embodiment, the nickel cobalt hydroxide is obtained by sequentially subjecting laterite nickel ore to high pressure acid leaching, neutralization and impurity removal, and neutralization and precipitation of nickel and cobalt. This is prior art and will not be elaborated in detail in the present invention.

[0014] In some specific embodiments of the present invention, the composition of nickel cobalt hydroxide is: Ni: 35-40%, Co 3-5%, Mn 5-10%, Fe<0.1%, Al<0.1%, Zn 0.5-1%, Si 0.1-0.3%.

[0015] In this embodiment, the desiliconization method in the above nickel-cobalt hydroxide leaching process also includes: a high-acid normal pressure leaching step. In order to enhance the leaching of nickel and cobalt in the first filter residue, the first filter residue is further leached with high acid and normal pressure, and the leaching acidity is controlled to be 0.1-1 mol / L, including but not limited to 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 1 mol / L, etc., preferably 0.2-0.5 mol / L; the leaching temperature is room temperature, and the leaching time is 0.5-5h, including but not limited to 0.5h, 1h, 2h, 3h, 4h, 5h, etc. If the leaching If the time is too short, the leaching is incomplete and the nickel-cobalt leaching effect is poor; if the leaching time is too long, the energy consumption will increase; the leaching solid-liquid ratio is controlled at 50-200g / L. If the solid-liquid ratio is too low, the processing volume will be affected; if the solid-liquid ratio is too high, the slurry viscosity will be too high, affecting the leaching process; the acid used is a common inorganic acid, and the second filtrate can be returned to the low-acid high-pressure leaching process as a leaching agent for the next leaching, increasing the effective utilization rate of the acid. The main components of the second filter residue are SiO2 and a small amount of CaSO4, which can be used as a CO2 capture agent synthesis material for backup.

[0016] In the second aspect, the present invention provides a method for recycling silicon in the process of nickel-cobalt hydroxide leaching, comprising the following steps: after the second filter residue is evenly mixed with the lithium source, high-temperature roasting is performed to obtain a porous CaO·Li4SiO4 adsorbent. In this step, before the second filter residue is mixed with the lithium source, the second filter residue can be dried; the lithium source is lithium hydroxide or lithium carbonate; the mass ratio of the second filter residue to the lithium source is 1: (1-5), including but not limited to 1: 1, 1: 2, 1: 3, 1: 4, 1: 5, etc.; the temperature of high-temperature roasting is 800-1200°C, including but not limited to 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.; the time of high-temperature roasting is 1-5h, including but not limited to 1h, 2h, 3h, 4h, 5h, etc.; the roasting atmosphere is the atmospheric atmosphere, and after the roasting is completed, the roasting product is crushed and screened to obtain a CO2 capture agent with a particle size of less than 150 meshes. The roasting tail gas generated in this step is absorbed by an alkaline solution, and further evaporated and crystallized to prepare an alkali metal sulfate or ammonium sulfate salt. The present invention does not limit the type of base used, and those skilled in the art can select it according to actual conditions. For example, it can be alkali metal hydroxide, ammonia water, etc., with a concentration of 1-3 mol / L.

[0017] The present invention mixes and roasts the second filter residue with a lithium source to further increase the value of the SiO2 / CaSO4 residue and regenerate it to prepare a porous CO2 adsorbent (CaO·Li4SiO4 adsorbent), which can be used to adsorb CO2 in the air.

[0018] To avoid redundant description, some raw materials are summarized as follows in the following embodiments and comparative examples of the present invention:

[0019] The composition of nickel cobalt hydroxide is: Ni 38.53%, Co 3.42%, Mn 8.38%, Fe 0.03%, Al 0.06%, Zn 0.85%, Si 0.22%.

[0020] Example 1

[0021] (1) Low-acid high-pressure leaching: In a high-pressure reactor, nickel cobalt hydroxide is leached at a solid-liquid ratio of 100g / L, a temperature of 180°C, and a time of 1h. The rotation speed is uniformly set to 400rpm during the leaching process. Dilute sulfuric acid / second filtrate or liquid alkali is continuously pumped in by a peristaltic pump to maintain the pH of the solution in the leaching reactor at 1.5±0.2. After the reaction is completed, the first filtrate is filtered to obtain a subsequent treatment process.

[0022] (2) High-acid atmospheric pressure leaching: The first filter residue is further subjected to high-acid atmospheric pressure leaching under the following conditions: solid-liquid ratio of 100 g / L, room temperature, acidity of 0.2 mol / L H2SO4, leaching time of 1 h, stirring speed uniformly set at 400 rpm. After the leaching is completed, the second filtrate and the second filter residue are obtained by filtration, wherein the second filtrate is returned to the low-acid high-pressure leaching process section to realize further utilization of the residual acid in the second filtrate.

[0023] (3) Mixed lithium high-temperature roasting: The second filter residue is dried and uniformly mixed with lithium carbonate in a mass ratio of 1:3 and then roasted at a temperature of 1000°C for 2 h. After the roasting is completed, it is naturally cooled to room temperature and taken out, crushed and sieved to obtain a CaO·Li4SiO4 product with a particle size of less than 150 mesh. The roasting tail gas is absorbed by a 1 mol / L sodium hydroxide solution.

[0024] Embodiment 2-5

[0025] Example 2-5 verifies the effect of pH on the silicon content in the first filtrate and the nickel and cobalt content entrained in the second filter residue in the low-acid high-pressure leaching step. Compared with Example 1, the only difference is that the pH is different in the low-acid high-pressure leaching step. The test results are shown in Table 1.

[0026] Table 1

[0027]

[0028] It can be seen from Table 1 that in the low-acid high-pressure leaching step, as the pH increases, the silicon content in the first filtrate shows a downward trend, and the nickel and cobalt entrained in the second filter residue gradually increases; when the pH increases to above 1.5±0.2, the silicon content in the first filtrate shows a weak upward trend, but is less than 1ppm in the pH range of 1.3 to 3.2; when the pH decreases to below 2±0.2, the nickel and cobalt contents entrained in the second filter residue are all below 0.01%.

[0029] Embodiment 6-11

[0030] Examples 6-11 verify the effect of leaching temperature on the silicon content in the first filtrate and the nickel and cobalt content entrained in the second filter residue in the low-acid high-pressure leaching step. Compared with Example 1, the only difference is that the leaching temperature is different in the low-acid high-pressure leaching step. The test results are shown in Table 2.

[0031] Table 2

[0032]

[0033]

[0034] It can be seen from Table 2 that in the low-acid high-pressure leaching step, within the range of 100-350°C, the temperature has little effect on the content of nickel and cobalt entrained in the second filter residue, all of which are below 0.01%. However, as the temperature increases, the silicon content in the first filtrate shows a downward trend; when the temperature rises to above 180°C, the silicon content in the first filtrate tends to be flat, all less than 1ppm.

[0035] Examples 12-16

[0036] Examples 12-16 verify the effect of acidity on the content of nickel and cobalt entrained in the second filter residue in the high-acid and normal-pressure leaching step. Compared with Example 1, the only difference is that the acidity is different in the high-acid and normal-pressure leaching step. The test results are shown in Table 3.

[0037] Table 3

[0038]

[0039] It can be seen from Table 3 that in the high-acid atmospheric pressure leaching step, as the acidity increases, the nickel and cobalt content entrained in the second filter residue shows a downward trend. When the acidity is increased to 0.2 mol / L, the nickel and cobalt content entrained in the second filter residue tends to be flat, all below 0.01%.

[0040] Comparative Example 1

[0041] Step (1) of Comparative Example 1 is an existing low-acid atmospheric pressure leaching process, which is specifically as follows:

[0042] (1) Low-acid atmospheric pressure leaching: nickel cobalt hydroxide is subjected to low-acid atmospheric pressure leaching, and the first filter residue and the first filtrate are obtained by filtration. The rotation speed is uniformly set to 400 rpm during the leaching process, and the pH value during the leaching process is controlled to be 1.5±0.2 by continuously pumping dilute sulfuric acid / second filtrate or liquid alkali through a peristaltic pump, and the temperature during the leaching process is controlled at 50°C, the time is controlled at 2h, and the leaching solid-liquid ratio is controlled at 100g / L;

[0043] (2) High-acid atmospheric pressure leaching: The first filter residue is further subjected to high-acid atmospheric pressure leaching under the following conditions: solid-liquid ratio of 100 g / L, room temperature, acidity of 0.2 mol / L H2SO4, leaching time of 1 h, stirring speed uniformly set at 400 rpm. After the leaching is completed, the second filtrate and the second filter residue are obtained by filtration, wherein the second filtrate is returned to the low-acid high-pressure leaching process section to realize further utilization of the residual acid in the second filtrate.

[0044] During the silicon removal process of this method, filtration is extremely difficult, and the silicon content in the obtained first filtrate is 53 ppm, the nickel content entrained in the second filter residue is 0.58%, and the cobalt content entrained in the second filter residue is 0.33%.

[0045] In summary, the present invention reduces the silicon concentration in the nickel cobalt hydroxide leaching solution to below 1ppm through one-step deep silicon removal, and greatly improves the filtering performance of the silicon removal slag; at the same time, the acid utilization rate of the whole process exceeds 95%, and the nickel and cobalt leaching rates exceed 99%. In addition, the nickel cobalt hydroxide desiliconized slag has a high purity, and the entrained nickel and cobalt content is less than 0.01%, which can be used as one of the synthetic materials for CO2 capture agents. The present invention further synthesizes CaO·Li4SiO4 capture agents based on this, realizing the high-value utilization of silicon slag.

[0046] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for desiliconization in a nickel-cobalt hydroxide leaching process, characterized in that: The following steps are involved: Leaching nickel cobalt hydroxide with low acid and high pressure, filtering to obtain a first filter residue and a first filtrate; The first filter residue is leached with high acid and normal pressure, and filtered to obtain a second filter residue and a second filtrate; wherein, The nickel cobalt hydroxide is obtained by sequentially subjecting laterite nickel ore to high pressure acid leaching, neutralization and impurity removal, and neutralization and precipitation of nickel and cobalt; During the low-acid high-pressure leaching process, the pH value during the leaching process is controlled to be maintained at 0.8-2.2, the leaching temperature is 150-350° C., the leaching time is 0.5-5 h, and the leaching solid-liquid ratio is controlled to be 50-200 g / L; In the high-acid and normal-pressure leaching process, the leaching acidity is controlled to be 0.1-1 mol / L, the leaching temperature is room temperature, the leaching time is 0.5-5h, and the leaching solid-liquid ratio is controlled to be 50-200g / L.

2. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: During the low-acid high-pressure leaching process, the pH value during the leaching process is controlled to be maintained at 1.3-2.2, the leaching temperature is 180-350° C., and the leaching time is 0.5-5 h.

3. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: In the low-acid high-pressure leaching process, acid or alkali is used to adjust the pH, the acid used is a common inorganic acid, and the alkali used is calcium oxide or calcium carbonate slurry.

4. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: The low-acid high-pressure leaching process is carried out in a high-pressure reactor.

5. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: The composition of the nickel cobalt hydroxide is: Ni: 35-40%, Co 3-5%, Mn 5-10%, Fe<0.1%, Al<0.1%, Zn 0.5-1%, Si 0.1-0.3%.

6. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: During the high-acid and normal-pressure leaching process, the leaching acidity is controlled to be 0.2-0.5 mol / L, and the leaching time is 0.5-5h.

7. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: The second filtrate is returned to the low-acid high-pressure leaching process as a leaching agent for the next leaching.

8. A method for recycling silicon in the process of nickel-cobalt hydroxide leaching, characterized in that: The following steps are involved: Leaching nickel cobalt hydroxide with low acid and high pressure, filtering to obtain a first filter residue and a first filtrate; Leaching the first filter residue with high acid and normal pressure, filtering to obtain a second filter residue and a second filtrate; The second filter residue is mixed evenly with the lithium source and then calcined at high temperature to obtain a porous CaO·Li4SiO4 adsorbent; wherein, The nickel cobalt hydroxide is obtained by sequentially subjecting laterite nickel ore to high pressure acid leaching, neutralization and impurity removal, and neutralization and precipitation of nickel and cobalt; During the low-acid high-pressure leaching process, the pH value during the leaching process is controlled to be maintained at 0.8-2.2, the leaching temperature is 150-350° C., the leaching time is 0.5-5 h, and the leaching solid-liquid ratio is controlled to be 50-200 g / L; In the high-acid and normal-pressure leaching process, the leaching acidity is controlled to be 0.1-1 mol / L, the leaching temperature is room temperature, the leaching time is 0.5-5h, and the leaching solid-liquid ratio is controlled to be 50-200g / L.

9. The method for recycling silicon in the nickel-cobalt hydroxide leaching process according to claim 8, characterized in that: The lithium source is lithium hydroxide or lithium carbonate; the mass ratio of the second filter residue to the lithium source is 1:(1-5).

10. The method for recycling silicon in the nickel-cobalt hydroxide leaching process according to claim 8, characterized in that: The temperature of the high-temperature calcination is 800-1200° C., the time of the high-temperature calcination is 1-5 hours, and the calcination atmosphere is the air atmosphere.

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