WO2025000369A1 - Silicon removal method and silicon reutilization method in mixed hydroxide precipitate leaching process - Google Patents

Abstract

The present invention relates to the technical field of hydrometallurgy. Disclosed are a silicon removal method and silicon reutilization method in a mixed hydroxide precipitate leaching process. The silicon removal method comprises: performing low-acid high-pressure leaching on a mixed hydroxide precipitate, and performing filtration to obtain a first filter residue and a first filtrate. According to the present invention, by converting silicic acid into silicon dioxide at high temperature and high pressure, the silicic acid which is difficult to filter is transformed into the silicon dioxide which can be easily filtered, such that the filtering performance of impurity silicon precipitates is greatly improved, thereby solving the current situation that the whole production process is stuck in the step; and additionally, the concentration of silicon in a leaching solution can reach 1 ppm or below, and the effect is far superior to that in the current situation that the concentration of residual silicon in a silicic acid filtering solution is 50 ppm or above. In addition, the silicon-removed slag of the mixed hydroxide precipitate obtained further by means of high-acid normal-pressure leaching has relatively high purity, and the content of entrained nickel and the content of entrained cobalt are both 0.01% or below, and on this basis, a CaO·Li4SiO4 trapping agent is further synthesized in the present invention, thereby achieving high-value reutilization of silicon slag.

Description

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

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

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.

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

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.

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.

In a second aspect, the present invention provides a method for recycling silicon in a nickel-cobalt hydroxide leaching process. The method comprises the following steps: mixing the first filter residue obtained by leaching nickel cobalt hydroxide with low acid and high pressure, further leaching the second filter residue obtained by leaching with high acid and normal pressure with a lithium source, and then calcining at high temperature to obtain a porous CaO·Li ₄ SiO ₄ adsorbent.

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

The present invention converts silicic acid, which is difficult to filter, into silicon dioxide, which is easy to filter, by converting silicic acid into silicon dioxide 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 leaching solution can reach less than 1ppm, which is much better than the current situation that the residual silicon in the solution is still more than 50ppm when using silicic acid to filter. 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 less than 0.01%, which can be used as one of the synthetic materials for _CO2 capture agent. The present invention further synthesizes CaO· _Li4SiO4 capture _agent based on this, realizing the high-value utilization of silicon slag.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a process flow chart of an embodiment of a method for desiliconization and silicon recycling in a nickel-cobalt hydroxide leaching process provided by the present invention.

DETAILED DESCRIPTION

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.

Please refer to 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 by 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 value 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 is increased; 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 high 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 and normal-pressure leaching treatment.

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.

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.

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%.

In this embodiment, the method for desiliconization 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 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 large to affect 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 second filter residue is mainly composed of _SiO2 and a small amount of _CaSO4 , which can be used as a _CO2 capture agent synthesis material for backup.

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 uniformly mixing the second filter residue with the lithium source, high-temperature roasting is performed to obtain a porous CaO·Li ₄ SiO ₄ 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: 1: 2, 1: 3, 1: 4, 1: 5, etc. The calcination time is 1-5h, including but not limited to 1h, 2h, 3h, 4h, 5h, etc.; the calcination atmosphere is the atmospheric atmosphere, and the calcination product is crushed and sieved after the calcination is completed to obtain a _CO2 capture agent with a particle size of less than 150 mesh. The calcination 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 alkali used, and those skilled in the art can choose according to actual conditions. For example, it can be an alkali metal hydroxide, ammonia water, etc., with a concentration of 1-3 mol/L.

The present invention mixes and roasts the second filter residue with a lithium source to further increase the value of SiO ₂ /CaSO ₄ residue and recycle it to prepare a porous CO ₂ adsorbent (CaO·Li ₄ SiO ₄ adsorbent), which can be used to adsorb CO ₂ in the air.

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

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%.

Example 1

(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.

(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 H ₂ SO ₄ , 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.

(3) Mixed lithium high temperature roasting: The second filter residue is dried and then evenly mixed with lithium carbonate in a mass ratio of 1:3 and roasted at a temperature of 1000°C for 2 hours. After roasting, it is naturally cooled to room temperature and taken out, crushed and sieved to obtain a CaO·Li ₄ SiO ₄ product with a particle size of less than 150 mesh. The roasting tail gas is absorbed by a 1 mol/L sodium hydroxide solution.

Embodiment 2-5

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.

Table 1

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%.

Embodiment 6-11

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.

Table 2

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.

Examples 12-16

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.

Table 3

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%.

Comparative Example 1

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

(1) Low-acid atmospheric pressure leaching: nickel cobalt hydroxide is leached at low acid atmospheric pressure, and the first filter residue and the first filtrate are obtained by filtration. The rotation speed during the leaching process is uniformly set to 400 rpm, and the peristaltic pump is used to Continuously pump in dilute sulfuric acid/second filtrate or liquid alkali to control the pH value of the leaching process to 1.5±0.2, control the temperature of the leaching process to 50℃, the time to 2h, and the leaching solid-liquid ratio to 100g/L;

(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 H ₂ SO ₄ , 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.

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%.

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.

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 (14)

A method for desiliconization during nickel cobalt hydroxide leaching, characterized in that it comprises 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 process, 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. The method for desiliconization in the nickel cobalt hydroxide leaching process according to claim 1 is characterized in that, during the low-acid high-pressure leaching process, the pH 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 0.5-5h. The method for desiliconization in the nickel cobalt hydroxide leaching process according to claim 1 is characterized in that, during the low-acid high-pressure leaching process, the leaching solid-liquid ratio is controlled at 50-200 g/L. The method for desiliconization in the nickel cobalt hydroxide leaching process according to claim 1 is characterized in that, during the low-acid and high-pressure leaching process, an acid or a base is used to adjust the pH, the acid used is a common inorganic acid, and the base used is calcium oxide or calcium carbonate slurry. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1 is characterized in that the low-acid high-pressure leaching process is carried out in a high-pressure reactor. The method for desiliconization in the leaching process of nickel-cobalt hydroxide according to claim 1 is characterized in that 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-cobalt. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1 is 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%. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1 is characterized in that it also includes: leaching the first filter residue with high acid and normal pressure, filtering to obtain a second filter residue and a second filtrate; wherein, during the high acid and normal pressure leaching process, the leaching acidity is controlled to be 0.1-1 mol/L, and the leaching temperature is room temperature. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8 is characterized in that, during the high-acid 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. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8 is characterized in that In the high-acid and normal-pressure leaching process, the leaching solid-liquid ratio is controlled at 50-200 g/L. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8 is characterized in that the second filtrate is returned to the low-acid high-pressure leaching process as a leaching agent for the next leaching. A method for recycling silicon in the process of nickel-cobalt hydroxide leaching, characterized by comprising the following steps: uniformly mixing the second filter residue according to any one of claims 8 to 11 with a lithium source and then calcining at high temperature to obtain a porous CaO·Li ₄ SiO ₄ adsorbent. The method for recycling silicon in the nickel-cobalt hydroxide leaching process according to claim 12, characterized in that the lithium source is lithium hydroxide or lithium carbonate; and the mass ratio of the second filter residue to the lithium source is 1:(1-5). The method for recycling silicon in the nickel cobalt hydroxide leaching process according to claim 12 is characterized in that the temperature of the high-temperature roasting is 800-1200°C, the time of the high-temperature roasting is 1-5h, and the roasting atmosphere is the atmospheric atmosphere.