Silicon removal agent, preparation method and application thereof

Abstract

The application provides a silicon removal agent, a preparation method and application. The silicon removal agent is prepared from the following raw materials: zirconium sulfate, a sulfur-containing organic chelating agent and a polyhydroxy carboxylic acid. The silicon removal agent solves the problems of low silicon removal efficiency, great influence of the silicon content of a previous liquid on the silicon removal efficiency, and difficulty in stably removing silicon to a deep degree after the silicon removal in the existing nickel sulfate silicon removal process.

Description

Technical Field

[0001] This invention relates to the field of solution impurity removal technology, and in particular to a silicon remover, its preparation method, and its application. Background Technology

[0002] Nickel sulfate is a key raw material for preparing ternary cathode material precursors, and its purity directly affects the electrochemical performance and cycle life of the final battery product. With the rapid development of the new energy vehicle industry, the market demand for high-nickel, low-silicon, and even silicon-free ternary materials is increasing, which places more stringent requirements on the quality of nickel sulfate raw materials, especially the control of the silicon content, an impurity element. Currently, the industry generally requires the silicon content in refined nickel sulfate solutions to be below 0.002 g / L, and this standard is expected to be further improved with technological advancements.

[0003] However, existing silicon removal processes suffer from significant technical bottlenecks: their effectiveness heavily depends on fluctuations in the silicon content of the nickel sulfate solution in the preceding process. When the silicon content in the raw material solution increases slightly, existing processes struggle to consistently control the silicon content of the post-removal solution below 0.002 g / L. This leads to unstable product quality and large batch-to-batch variations, increasing the burden on subsequent processes and potentially affecting the consistency and yield of the final battery materials.

[0004] Therefore, developing a new deep silicon removal process with high silicon removal efficiency has become an urgent need to improve the quality of nickel sulfate products and ensure large-scale stable production. How to achieve efficient and deep silicon removal in complex nickel salt systems with high salt and high impurities, and ensure that the silicon content in the liquid solution remains stable and meets standards for a long period after silicon removal, is a core technical challenge that urgently needs to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a silicon removal agent, its preparation method, and its application, aiming to solve key technical problems in existing nickel sulfate silicon removal processes, such as low silicon removal efficiency, significant influence from fluctuations in the silicon content of the preceding liquid, and difficulty in achieving stable silicon content in the liquid after silicon removal.

[0006] To achieve the above objectives, the present invention provides a silicon remover, wherein the raw materials for preparing the silicon remover include: zirconium sulfate, sulfur-containing organic chelating agent and polyhydroxycarboxylic acid.

[0007] According to the first aspect of the present invention, at least the following beneficial effects are achieved: 1. The silicon remover of this invention uses zirconium sulfate, sulfur-containing organic chelating agents, and polyhydroxycarboxylic acids as raw materials. Through the synergistic effect of each component, it achieves efficient and deep removal of silicon impurities in nickel sulfate solution. Specifically, silicic acid polymerization is a dynamic equilibrium process. After nickel hydroxide removes most of the high-polysilicic acid, some monosilicic acid and oligosilicic acid remain in the solution, which are difficult to remove by conventional methods. The silicon remover of this invention, as a special composite agent for silicon removal in high-salt systems, has significant chelating properties for monosilicic acid and oligosilicic acid, and has a wide pH range (especially with good stability under acidic conditions). The mechanism of action is as follows: H4SiO4 + silicon remover → silicon remover • H4SiO4↓; n(H3SiO4) - +Silicone remover+nH + →[Silicone remover • H4SiO4] n ↓.

[0008] 2. The dithiocarbamate (such as sodium dithiocarbamate) introduced in this invention acts as a strong coordinating sulfur-containing organic chelating agent, capable of rapidly reacting with... A coordination reaction occurs, forming a stable zirconium dithiocarbamate complex, which will... Anchored to an organic anionic framework, it forms negatively charged or neutral soluble complexes, effectively inhibiting... The free hydrolysis significantly improves the dispersion stability of the zirconium source in solution, avoiding precipitation problems caused by excessively high local concentrations, and ensuring... It participates in the subsequent silicon removal reaction in a uniformly dispersed state, which provides a prerequisite for efficient silicon removal.

[0009] Dithiocarbamate molecules contain two sulfur atoms and one nitrogen atom, forming a polydentate ligand structure. When it interacts with... During the reaction, stable Zr-S / N coordination bonds are formed, constructing a three-dimensional network structure.

[0010] This in-situ generated network complex structure allows sulfur atoms in the network structure to form S–Si bridging or weak covalent interactions with Si atoms in monosilicic acid and oligosilicic acid anions, achieving efficient chelation of dissolved silicon. For already formed high-polymer silicate particles, this network structure can encapsulate and co-precipitate them through surface adsorption, bridging flocculation, etc., significantly enhancing the comprehensive removal capacity for silicon in different polymeric states.

[0011] 3. Zirconium sulfate provides zirconium ions, whose high charge density and multi-coordination ability can form stable complexes with silicate ions or their polymeric forms, promoting rapid coagulation and precipitation of silicic acid and enhancing the capture efficiency of the desiliconizing agent for oligomeric silicic acid. Sulfur-containing organic chelating agents introduce sulfur atoms as soft ligands, which can bind with zirconium and form S-Zr-Si complexes with silicon in solution, achieving deep removal of both monosilicic acid and oligomeric silicic acid. Polyhydroxycarboxylic acids provide multiple hydroxyl and carboxyl functional groups. On the one hand, they act as stabilizers, preventing zirconium ions from hydrolyzing or precipitating in strongly acidic environments, ensuring the long-term stability of the desiliconizing agent. On the other hand, their hydroxyl groups can form hydrogen bond networks with the silicic acid surface, promoting flocculation of silicic acid particles and solid-liquid separation, thereby improving the overall desiliconization efficiency. Through the above mechanisms, the synergistic effect of each component improves the silicon removal rate.

[0012] 4. The silicon-removing agent of this invention is suitable for nickel sulfate systems, thanks to its adaptability to high-salt and high-acid environments: nickel sulfate solutions typically contain high concentrations of Ni. 2+ Plasma and pH under acidic conditions make existing silicon removal methods susceptible to fluctuations in the pH of the preceding solution and the influence of impurity elements, leading to unstable silicon removal. The zirconium sulfate component of this invention's silicon remover has good compatibility with sulfate ions, avoiding the introduction of additional salts; the sulfur-containing organic chelating agent's sulfur groups have anti-interference capabilities in high-salt systems, forming a stable S-Zr-Si structure for deep silicon removal; and the polyhydroxycarboxylic acid enhances the pH buffering and stability of the silicon remover, adapting to dynamic pH changes in nickel sulfate solutions. Therefore, in nickel sulfate production (such as treating pressurized leaching solutions or MHP leaching solutions), this invention's silicon remover can significantly reduce the impact of fluctuations in the silicon content of the preceding solution, improving production efficiency.

[0013] 5. In the nickel salt desiliconization system, citric acid and tartaric acid are both multiprotic weak acids, which can release [resources] in solution. It possesses good pH buffering capacity, can resist external disturbances during the reaction process, and maintain the pH of the system within a suitable range (e.g., 4-6), thereby ensuring... It neither hydrolyzes nor precipitates, and can effectively participate in coordination reactions. Citric acid and tartaric acid molecules contain multiple hydroxyl and carboxyl groups, which enhance the solubility and colloidal stability of the intermediate in the aqueous phase, prevent its self-aggregation and precipitation, and enable it to maintain uniform dispersion and high reactivity in complex nickel sulfate systems.

[0014] According to some embodiments of the present invention, the sulfur-containing organic chelating agent includes: dithiocarbamate.

[0015] According to some embodiments of the present invention, the polyhydroxycarboxylic acid includes at least one of tartaric acid and citric acid.

[0016] The present invention also provides a method for preparing the aforementioned silicon remover, comprising the following steps: S1. The zirconium sulfate solution and the dithiocarbamate solution are mixed and reacted to obtain zirconium dithiocarbamate; S2. The polyhydroxycarboxylic acid and the zirconium dithiocarbamate are mixed and reacted to obtain the silicon remover.

[0017] According to some embodiments of the present invention, the method for preparing the silicon-removing agent includes the following steps: S1. A zirconium sulfate solution with a concentration of 1.8~2.2 mol / L and a dithiocarbamate solution with a concentration of 1.8~2.2 mol / L are mixed and reacted at a volume ratio of 1.0~2.0:1 to obtain zirconium dithiocarbamate; S2. A polyhydroxycarboxylic acid solution with a concentration of 1.8~2.2 mol / L is mixed with the zirconium dithiocarbamate at a mass ratio of 3~4:1 to obtain the silicon remover.

[0018] In step S1 of the method for preparing the silicon remover, the zirconium sulfate solution provides Zr. 4+ The ions are mixed with the dithiocarbamate solution to form a stable zirconium dithiocarbamate soft complex; in step S2, the polyhydroxycarboxylic acid reacts further with the complex to form hydrogen bonds and coordination networks, which improves the overall stability of the desiliconizing agent.

[0019] The present invention also provides a method for removing silicon from a nickel salt system, comprising the following steps: A1. Adding nickel hydroxide to a silicon-containing nickel salt solution and reacting, wherein the amount of crude nickel hydroxide added is 100~200 g / L; A2. Add a desiliconizing agent to the solution after the reaction in step A1, mix and react, then perform solid-liquid separation to obtain the desiliconized liquid; The amount of crude nickel hydroxide added is 2~10 g / L.

[0020] When nickel hydroxide is used in combination with the silicon removal agent of this invention, the advantages of both silicon removal methods can be fully utilized: nickel hydroxide promotes the polymerization of silicic acid and initially removes high-polymer silicic acid, while the silicon removal agent chelates and precipitates residual monosilicic acid and oligosilicic acid, thereby greatly reducing the amount of silicon removal agent used and improving the stability of the silicon removal process.

[0021] According to some embodiments of the present invention, in step A1, the temperature of the reaction is 50~70°C.

[0022] According to some embodiments of the present invention, in step A1, the reaction time is 2 to 5 hours.

[0023] According to some embodiments of the present invention, in step A2, the temperature of the reaction is 50~70°C.

[0024] According to some embodiments of the present invention, in step A2, the reaction time is 2 to 5 hours.

[0025] The described nickel salt system desiliconization method employs a two-step synergistic process. In step A1, 100-200 g / L of crude nickel hydroxide is added. Under conditions of 50-70℃ and 4-7 hours, the solution pH is significantly increased, promoting the rapid polymerization of monosilicic acid and oligosilicic acid into high-polysilicic acid macromolecules, achieving preliminary removal of most of the silicon. In step A2, 2-10 g / L of desiliconizing agent is added. Under the same temperature and time conditions, this agent efficiently chelates and precipitates residual monosilicic acid and oligosilicic acid anions, achieving deep desiliconization. This two-step method fully leverages the complementary mechanisms of nickel hydroxide's "polymerization induction" and the desiliconizing agent's "precise chelation," significantly reducing the amount of desiliconizing agent required and resulting in stable silicon content in the final solution.

[0026] Both A1 and A2 are controlled at 50~70℃ for 2~5h, which is within the optimal range of kinetics for the polymerization and chelation of silica. If the temperature is too low, the polymerization / chelation rate is slow, and if it is too high, the complex structure is easily destroyed. If the time is insufficient, the reaction is incomplete, and if it is too long, there is no gain. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] A silicon-removing agent, its preparation method, and its application, specifically: S1. A zirconium sulfate solution with a concentration of 1.8~2.2 mol / L and a dithiocarbamate solution with a concentration of 1.8~2.2 mol / L are mixed and reacted at a volume ratio of 1.0~2.0:1 to obtain zirconium dithiocarbamate; S2. A polyhydroxycarboxylic acid solution with a concentration of 1.8~2.2 mol / L is mixed with the zirconium dithiocarbamate at a mass ratio of 3~4:1 to obtain the silicon remover.

[0030] A method for removing silicon from a nickel salt system includes the following steps: A1. The Si content is 0.010 g / L~0.10 g / L, Ni... 2+The concentration is 90g / L~120g / L, pH=4.0~5.5. The pre-silicon removal liquid is placed in a reaction vessel. Under the condition of 60℃, the mixture is stirred at a speed of 100r / min. Then, crude nickel hydroxide is added to the reaction vessel at a rate of 100g / L~200g / L, and the mixture is stirred and reacted for 2h. A2. Add the desiliconizing agent described in S2 at a concentration of 2 g / L to 10 g / L, stir and react for 3 hours, then filter with 10 μm filter paper (filter cloth) to obtain the desiliconized liquid.

[0031] The pre-silicon removal solution refers to the MHP leaching solution, pressure leaching solution, and mixture of pressure leaching solution and MHP leaching solution provided by Jinchuan Group Nickel Salt Co., Ltd.

[0032] Crude nickel hydroxide refers to the raw material for the MHP leaching process provided by Jinchuan Group Nickel Salt Co., Ltd.

[0033] Example 1 This embodiment provides a silicon remover and its application, comprising the following steps: A1. Place 1000 mL of MHP leaching solution with silicon content of 0.076 g / L, nickel concentration of 112.3 g / L, and pH=4.62 in a reaction vessel. Stir at 100 r / min at 60℃, and then add 150 g (150 g / L) of crude nickel hydroxide to the reaction vessel at once. Stir and react for 2 h. The final pH is 5.32. A2. Add 5.0g (5.0g / L) of desiliconizing agent to the reactor at one time, stir and react for 3h. The final pH is 5.16. Vacuum filter the mixture in the reactor using 10μm pilot filter paper. The sample was taken and the silicon content of the desiliconized liquid was measured to be 0.0014g / L and the nickel content was 112.6g / L.

[0034] The silicon remover is a mixture of zirconium dithiocarbamate and tartaric acid in a mass ratio of 1:4 (preparation method: prepare 2 mol / L zirconium sulfate solution A, solvent is water; 2 mol / L sodium dithiocarbamate solution B, solvent is water; 2 mol / L tartaric acid solution C, solvent is water; after VB:VA = 1.05:1 react fully, solid-liquid separation is performed to obtain solid zirconium dithiocarbamate D; mix MC:MD = 4:1 and stir thoroughly to obtain silicon remover E).

[0035] Example 2 This embodiment provides a silicon remover and its application, comprising the following steps: A1. 20m 3MHP leaching solution with silicon content of 0.032 g / L, nickel concentration of 107.2 g / L, and pH of 4.80 was placed in a reactor and stirred at 100 r / min at 60°C. 3 t (150 g / L) of crude nickel hydroxide was added to the reactor at one time, and the reaction was stirred for 2 h. The final pH was 5.26. A2. Add 60 kg (3.0 g / L) of silica remover to the reactor at once, stir and react for 3 hours. The final pH is 5.08. Drain the mixture in the reactor through a 150 m... 2 Solid-liquid separation was performed using plate and frame filter press with a 5μm filter cloth. After sampling, the silicon content in the liquid after silicon removal was measured to be 0.0016 g / L and the nickel content was 106.6 g / L.

[0036] Example 3 This embodiment provides a silicon remover and its application, comprising the following steps: A1. 50m 3 A pressurized leachate with a silicon content of 0.10 g / L, a nickel concentration of 113.8 g / L, and a pH of 5.10 was placed in a reactor and stirred at 100 r / min at 70°C. 5 t (100 g / L) of crude nickel hydroxide was added to the reactor at one time, and the reaction was stirred for 2 h. The final pH was 5.33. A2. Using a metering pump, add 350 kg (7.0 g / L) of silica remover to the reactor, controlling the addition time to approximately 30 minutes. Stir the reaction for 3 hours, reaching a final pH of 5.15. Then, sift the mixture in the reactor through a 150 m... 2 Solid-liquid separation was performed using plate and frame filter press with a 5μm filter cloth. After sampling, the silicon content in the liquid after silicon removal was measured to be 0.0018 g / L and the nickel content was 112.7 g / L.

[0037] Example 4 This embodiment provides a silicon remover and its application, comprising the following steps: A1. A pressure leaching solution with a silicon content of 0.032 g / L, a nickel concentration of 90 g / L, and a pH of 4.50–5.20 is placed in a series of 5 reactors connected in a step-by-step overflow desiliconization line, with a single reactor volume of 50 m³. 3 The temperature was 70℃, and the stirring speed was 100 r / min. 5t (100g / L) of crude nickel hydroxide was added to each reactor at once, and the mixture was stirred for 2 hours. A2. Add pre-desiliconization liquid to the primary reactor, controlling the flow rate of the pre-desiliconization liquid to 20m. 3 At the same time, a diaphragm pump is used to add silicon remover to the secondary reactor at a flow rate of 0.1 m³ / h. 3 / h~0.125m 3 / h (5.0g / L), the mixture in reactor #5 is passed through a 150m stream.2 Solid-liquid separation was performed using plate and frame filter press with a 5μm filter cloth. The filtrate was sampled every 2 hours to monitor the silica content. This process was repeated for 500m³ of continuous treatment. 3 The silicon content in the liquid was 0.0016 g / L.

[0038] Example 5 This embodiment provides a silicon remover and its application, comprising the following steps: A1. MHP leaching solution with a silicon content of 0.018 g / L, a nickel concentration of 95.0 g / L, and a pH of 4.40–5.10 was placed in a series of 5 reactors connected in a step-by-step overflow desiliconization line, with a single reactor volume of 50 m³. 3 The temperature was 70℃, the stirring speed was 100r / min, and 5t (100g / L) of crude nickel hydroxide was added to each reactor at one time, and the reaction was stirred for 2h. A2. Add pre-desiliconization liquid to the primary reactor, controlling the flow rate of the pre-desiliconization liquid to 20m. 3 / h~25m 3 At the same time, crude nickel hydroxide slurry with a solid-liquid ratio of 60% is added to the primary reactor, and the slurry flow rate is controlled at 4.0 m³ / h. 3 / h(V 除硅前液 V 浆化液 (5:1 ratio), and simultaneously, a diaphragm pump is used to add desiliconizing agent to the secondary reactor, controlling the desiliconizing agent flow rate to 0.1 m³ / min. 3 / h(V 除硅前液 V 除硅剂 =1000:5), the mixture in reactor #5 was passed through a 150m... 2 A plate and frame filter press is used for solid-liquid separation. A 5μm filter cloth is used throughout the process. The filtrate is sampled every 2 hours to monitor the silica content. The process is continuous for 300m³. 3 The silicon content in the liquid was 0.0018 g / L.

[0039] Example 6 This embodiment provides a silicon remover and its application, comprising the following steps: A1. A pressure leaching solution with a silicon content of 0.010 g / L, a nickel concentration of 105.2 g / L, and a pH of 4.80–5.20 is placed in a series of 5 reactors connected in a step-by-step overflow desiliconization line, with a single reactor volume of 50 m³. 3 The temperature was 70℃, the stirring speed was 100r / min, and 5t (100g / L) of crude nickel hydroxide was added to each reactor at one time, and the reaction was stirred for 2h. A2. Add pre-desiliconization liquid to the primary reactor, controlling the flow rate of the pre-desiliconization liquid to 25 m / s. 3 / h~50m 3 At the same time, crude nickel hydroxide slurry with a solid-liquid ratio of 60% is added to the primary reactor, and the slurry flow rate is controlled at 5.0 m³ / h. 3 / h(V 除硅前液 V 浆化液 (5:1 ratio), and simultaneously, a diaphragm pump is used to add silicon remover to the secondary reactor, controlling the silicon remover flow rate to be 0.05 m³ / min. 3 / h~0.10m 3 / h(V 除硅前液 V 除硅剂 =1000:2), the mixture in reactor #5 was passed through a 150m... 2 A plate and frame filter press is used for solid-liquid separation. A 5μm filter cloth is used throughout the process. The filtrate is sampled every 2 hours to monitor the silica content. The process can be continuously performed on a scale of 500m³. 3 The silicon content in the liquid was 0.0015 g / L.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that sodium dithiocarbamate in the desilicone remover is replaced with sodium xanthate.

[0041] Sodium xanthate is less selective for silicate groups than for nitrogen groups. Its low efficiency in capturing silicic acid leads to incomplete removal of residual silicon.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that only the tartaric acid in the desilicifying agent is replaced with citric acid, while the other conditions are the same.

[0043] Citric acid may cause the system to have a low pH, inhibiting the polymerization of silicic acid, making the desilicification process unstable, and reducing the pass rate.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that the silicon remover and crude nickel hydroxide are added to the reaction solution simultaneously, while the other conditions are the same.

[0045] Test Example 1 The silicon content in the nickel sulfate solutions before and after silicon removal in the examples and comparative examples was tested using the molybdenum blue colorimetric method. The results are shown in Table 1. Table 1. Performance Testing Comparative Example 1 used sodium xanthate instead of sodium dithiocarbamate, which resulted in low silicic acid capture efficiency and incomplete removal of residual silica. Comparative Example 2 used citric acid instead of tartaric acid, which may have led to a low pH in the system. Comparative Example 3 added both the silica remover and crude nickel hydroxide simultaneously, disrupting the orderly mechanism of "polymerization followed by chelation": nickel hydroxide could not fully induce the formation of high-polymer silicic acid, and the silica remover could not accurately capture residual mono / oligomeric silicic acid, leading to pH imbalance and a decrease in silica removal rate.

[0046] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for removing silicon from a nickel salt system, comprising the following steps: A1. Adding nickel hydroxide to a silicon-containing nickel salt solution and reacting, wherein the amount of nickel hydroxide added is 100~200 g / L; A2. Add a desiliconizing agent to the solution after the reaction in step A1, mix and react, then perform solid-liquid separation to obtain the desiliconized liquid; The amount of silicon remover added is 2~10 g / L; The raw materials for preparing the silicon remover include: zirconium sulfate, dithiocarbamate, and polyhydroxycarboxylic acid; The polyhydroxycarboxylic acid includes at least one of tartaric acid and citric acid; The method for preparing the silicon remover includes the following steps: S1. A zirconium sulfate solution with a concentration of 1.8~2.2 mol / L and a dithiocarbamate solution with a concentration of 1.8~2.2 mol / L are mixed and reacted at a volume ratio of 1.0~2.0:1 to obtain zirconium dithiocarbamate; S2. A polyhydroxycarboxylic acid solution with a concentration of 1.8~2.2 mol / L is mixed with the zirconium dithiocarbamate at a mass ratio of 3~4:1 to obtain the silicon remover.

2. The method for removing silicon from a nickel salt system according to claim 1, characterized in that, In step A1, the reaction temperature is 50~70℃.

3. The method for removing silicon from a nickel salt system according to claim 1, characterized in that, In step A1, the reaction time is 2 to 5 hours.

4. The method for removing silicon from a nickel salt system according to claim 1, characterized in that, In step A2, the reaction temperature is 50~70℃.

5. The method for removing silicon from a nickel salt system according to claim 1, characterized in that, In step A2, the reaction time is 2 to 5 hours.

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