Silicon removal method and silicon reutilization method in mixed hydroxide precipitate leaching process

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

[0001] The present 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 in the hydrometallurgical smelting of laterite nickel ore. Because laterite nickel ore contains a large amount of silicon, some silicon is inevitably introduced into the nickel cobalt hydroxide product during the hydrometallurgical processing. During the subsequent acid leaching process, the silicon entrained in the nickel cobalt hydroxide is leached into the leachate, necessitating effective means 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 silicate is 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 extending 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 silicate can be slightly soluble in water, results in a high level of silicon residue in the liquid after silicon removal, requiring further deep silicon removal through resin or extraction, which increases the processing cost and control difficulty of the entire process.

[0004] Summary of the Invention

[0005] 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 nickel-cobalt hydroxide leaching process, so as to solve the technical problems in the prior art of nickel-cobalt hydroxide leaching desiliconization technology, such as difficulty in filtering, easy loss of a large amount of nickel and cobalt, and high silicon residue in the liquid after desiliconization.

[0006] 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 using 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 during the leaching process is controlled to be maintained at 0.8-2.2, and the leaching temperature is 150-350°C.

[0007] In a second aspect, the present invention provides a method for recycling silicon in a nickel-cobalt hydroxide leaching process, comprising the following steps: leaching nickel-cobalt hydroxide using low-acid high-pressure leaching to obtain a first filter residue, further leaching using high-acid normal-pressure leaching to obtain a second filter residue, and mixing them evenly with a lithium source, followed by high-temperature calcination to obtain a porous CaO·Li4SiO4 adsorbent.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The present invention converts silicic acid into silicon dioxide under high temperature and high pressure, transforming the difficult-to-filter silicic acid into easily filterable silicon dioxide. This significantly improves the filtration performance of the impure silicon precipitate, thereby resolving the current situation where this process causes bottlenecks 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 be reduced to below 1 ppm, far exceeding the current situation where residual silicon in the solution using silicic acid filtration still exceeds 50 ppm. Furthermore, the nickel-cobalt hydroxide desiliconized slag obtained through high-acid, normal-pressure leaching has a high purity, with the entrained nickel and cobalt contents both below 0.01%, making it suitable as a synthetic material for CO2 capture agents. Based on this, the present invention further synthesizes a CaO·Li4SiO4 capture agent, achieving high-value utilization of silicon slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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

[0011] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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.

[0012] Referring to Figure 1 , in a first aspect, the present invention provides a method for desiliconization during nickel-cobalt hydroxide leaching, comprising the following steps: low-acid, high-pressure leaching: nickel-cobalt hydroxide is leached using low-acid, high-pressure leaching, 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 performed in an autoclave. 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, The solid-liquid ratio range includes, but is not limited to, 50g / L, 100g / L, 150g / L, and 200g / L. A low solid-liquid ratio will affect the processing capacity; a high solid-liquid ratio will result in excessive slurry viscosity, which will affect leaching. The pH is adjusted using an acid or base, with common inorganic acids being the acid and calcium oxide or calcium carbonate slurry being the base. After leaching is complete, the first filtrate undergoes subsequent treatment, and the first filter residue undergoes the next high-acid, atmospheric-pressure leaching process.

[0013] This invention converts silicic acid into silicon dioxide under high temperature and pressure, transforming the difficult-to-filter silicic acid into easily filterable silicon dioxide. This process addresses the bottleneck that currently plagues the entire production process. This improved process significantly improves the filtration performance of impure silicon precipitates, and the silicon concentration in the leachate can be reduced to below 1 ppm. This significantly surpasses the current practice of using silicic acid to filter solutions, where residual silicon can still exceed 50 ppm.

[0014] 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 upon in this invention.

[0015] 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%.

[0016] In this embodiment, the desiliconization method in the above nickel cobalt hydroxide leaching process further 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 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 will be incomplete and the nickel and cobalt leaching effect will be 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 capacity 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 the 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.

[0017] In a second aspect, the present invention provides a method for recycling silicon during nickel-cobalt hydroxide leaching, comprising the following steps: uniformly mixing a second filter residue with a lithium source and then calcining it at high temperature to obtain a porous CaO·Li4SiO4 adsorbent. In this step, the second filter residue may be dried before mixing with the lithium source; 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 high-temperature calcination temperature is 800-1200°C, including but not limited to 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.; the high-temperature calcination time is 1-5 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc.; the calcination atmosphere is atmospheric; and after calcination, the calcined product is crushed and sieved to obtain a CO2 scavenger with a particle size of less than 150 mesh. The calcination exhaust gas generated in this step is absorbed by an alkaline solution and further evaporated and crystallized to produce 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.

[0018] 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.

[0019] To avoid redundancy, some of the raw materials in the following embodiments and comparative examples of the present invention are summarized as follows:

[0020] 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%.

[0021] Example 1

[0022] (1) Low-acid high-pressure leaching: In a high-pressure reactor, nickel and cobalt hydroxide were leached under low-acid high-pressure conditions at a solid-liquid ratio of 100 g / L, a temperature of 180°C, and a time of 1 hour. The rotation speed was uniformly set at 400 rpm during the leaching process. Dilute sulfuric acid / second filtrate or liquid alkali was 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 was completed, the first filtrate was filtered to obtain the first filtrate for subsequent processing steps.

[0023] (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, and stirring speed uniformly set at 400 rpm. After the leaching is completed, the second filtrate and the second filter residue are obtained by filtration. 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.

[0024] (3) Mixed lithium high-temperature roasting: The second filter residue is dried and evenly mixed with lithium carbonate in a mass ratio of 1:3, and then roasted at a temperature of 1000°C for 2 h. After roasting, it is naturally cooled to room temperature and taken out, crushed and sieved to obtain CaO·Li4SiO4 products with a particle size of less than 150 mesh. The roasting exhaust gas is absorbed by a 1 mol / L sodium hydroxide solution.

[0025] Examples 2-5

[0026] Examples 2-5 examined the effect of pH on the silicon content in the first filtrate and the nickel and cobalt content in the second residue during the low-acid, high-pressure leaching step. The only difference from Example 1 was the pH used during the low-acid, high-pressure leaching step. The test results are shown in Table 1.

[0027] Table 1

[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 1 ppm 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] Examples 6-11

[0030] Examples 6-11 examined the effects of leaching temperature on the silicon content in the first filtrate and the nickel and cobalt content in the second residue during the low-acid, high-pressure leaching step. The only difference from Example 1 was the different leaching temperatures used during the low-acid, high-pressure leaching step. The test results are shown in Table 2.

[0031] Table 2

[0032] Table 2 shows that during the low-acid, high-pressure leaching step, within the temperature range of 100-350°C, the nickel and cobalt content in the second filter residue was minimally affected, remaining below 0.01%. However, as the temperature increased, the silicon content in the first filtrate decreased. When the temperature rose above 180°C, the silicon content in the first filtrate leveled off, remaining below 1 ppm.

[0033] Examples 12-16

[0034] Examples 12-16 examined the effect of acidity on the nickel and cobalt content in the second filter residue during the high-acid, normal-pressure leaching step. The only difference from Example 1 was the different acidity levels during the high-acid, normal-pressure leaching step. The test results are shown in Table 3.

[0035] Table 3

[0036] 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 and is below 0.01%.

[0037] Comparative Example 1

[0038] Step (1) of Comparative Example 1 is an existing low-acid atmospheric pressure leaching process, which is as follows:

[0039] (1) Low-acid and normal-pressure leaching: nickel cobalt hydroxide is subjected to low-acid and normal-pressure leaching, 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 dilute sulfuric acid / second filtrate or liquid alkali is continuously pumped in by a peristaltic pump to control the pH value during the leaching process to be 1.5±0.2. The temperature during the leaching process is controlled at 50°C, the leaching time is controlled at 2 hours, and the leaching solid-liquid ratio is controlled at 100 g / L.

[0040] (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, and stirring speed uniformly set at 400 rpm. After the leaching is completed, the second filtrate and the second filter residue are obtained by filtration. 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.

[0041] 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%.

[0042] In summary, the present invention reduces the silicon concentration in the nickel-cobalt hydroxide leachate to below 1 ppm through a one-step deep silicon removal process, significantly improving the filtration performance of the desiliconized slag. Simultaneously, the acid utilization rate of the entire process exceeds 95%, and the nickel and cobalt leaching rates exceed 99%. Furthermore, the nickel-cobalt hydroxide desiliconized slag has a high purity, with the entrained nickel and cobalt contents both below 0.01%, making it suitable as a synthetic material for CO2 capture agents. The present invention further synthesizes a CaO·Li4SiO4 capture agent based on this, achieving high-value utilization of silicon slag.

[0043] The specific embodiments of the present invention described above do not limit the scope of protection 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 scope of protection 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: The nickel cobalt hydroxide is leached with low acid and high pressure, and filtered 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.

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: During the low-acid high-pressure leaching process, the leaching solid-liquid ratio is controlled at 50-200 g / L.

4. 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.

5. 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.

6. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, 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 and cobalt.

7. 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%.

8. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 1, characterized in that: Also includes: 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, 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.

9. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8, 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 0.5-5 h.

10. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8, characterized in that: During the high-acid and normal-pressure leaching process, the leaching solid-liquid ratio is controlled at 50-200 g / L.

11. The method for desiliconization in the nickel-cobalt hydroxide leaching process according to claim 8, characterized in that: The second filtrate is returned to the low-acid high-pressure leaching process as a leaching agent for the next leaching.

12. A method for recycling silicon in the process of nickel-cobalt hydroxide leaching, characterized in that: The method comprises 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·Li4SiO4 adsorbent.

13. 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; the mass ratio of the second filter residue to the lithium source is 1:(1-5).

14. The method for recycling silicon in the nickel-cobalt hydroxide leaching process according to claim 12, 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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