A deep desiliconization method in lithium hydroxide production process

Abstract

The present invention provides a deep desiliconization method in the production process of lithium hydroxide. For lithium hydroxide causticizing liquid, a desiliconizing agent is first added to carry out a first-stage desiliconization, and the obtained first-stage desiliconized liquid is further added with a desiliconizing agent for a second-stage desiliconization, and the obtained second-stage desiliconized liquid is used to prepare lithium hydroxide; the desiliconizing agent includes a precipitant, an inorganic flocculant and an organic flocculant. The deep desiliconization method of the present invention adopts a method of chemical precipitation-adsorption combined with flocculation and sedimentation, and the precipitant and the inorganic flocculant are used for synergistic desiliconization. The precipitant and the impurity silicon form colloidal silica particles with a surface charge, the inorganic flocculant produces adsorption and polymerization to enhance desiliconization, and the organic flocculant can improve the sedimentation effect and the filtering effect, so that the silicon in the lithium hydroxide causticizing liquid can be deeply removed, and the whole process does not introduce new impurities, does not cause lithium loss, and does not cause secondary environmental protection and safety problems.

Description

Technical Field

[0001] The present invention relates to the metallurgical chemical industry of lithium, specifically to the technical field of lithium hydroxide production, and in particular to a deep desiliconization method in the lithium hydroxide production process. Background Art

[0002] Lithium is an important metal element, widely used in energy, metallurgy, glass, ceramics, rubber and grease. There are two main sources of lithium at present: one is the lithium salt compound obtained by extracting lithium ions from salt lake brine by extraction, adsorption, salting out or co-precipitation; the other is the lithium salt compound obtained by roasting or acid production from lithium-containing ores such as lepidolite or spodumene.

[0003] With the rapid development of the new energy industry, especially the rapid development of lithium batteries, the production and demand of lithium battery positive electrode materials continue to increase. Lithium battery positive electrode materials are represented by lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. The demand for lithium continues to increase rapidly, resulting in a tight demand for lithium salts.

[0004] At present, the mainstream process for preparing lithium hydroxide is the lithium carbonate causticization method, which includes: mixing refined lime milk and lithium carbonate in a ratio of 1.08:1, adjusting a certain causticizing solution concentration, heating to boiling and vigorously stirring. The causticizing reaction is as follows: Ca(OH)2+Li2CO3+2H2O=CaCO3+2LiOH·H2O. The reaction can obtain a lithium hydroxide solution with a concentration of about 3.5%. The insoluble residue (mainly CaCO3) is removed. After separation, the mother liquor is reduced pressure and concentrated, crystallized to obtain lithium hydroxide monohydrate, and dried to obtain the lithium hydroxide product.

[0005] The raw materials for the lithium carbonate causticization method are lithium carbonate and calcium hydroxide. Since the solubility of both raw materials is very small, the reaction concentration is low and the reaction time is very long, the energy consumption is high and the single-pass conversion rate is low. After the causticization reaction, the product lithium hydroxide is mainly in the solution, but the residual lithium in the filter cake is still large, the lithium hydroxide yield is low, the cost is high, and the product lithium hydroxide cannot reach battery grade and can only be used in the lubricant industry. In addition, since the lithium carbonate and calcium hydroxide (quicklime or calcium oxide) used as raw materials are often of industrial grade purity, they mainly contain impurities such as silicon, resulting in a high silicon content in the final product lithium hydroxide, low economic value, and poor market competitiveness.

[0006] In summary, it is necessary to develop a deep desiliconization method in the lithium hydroxide production process, which can be beneficial to the preparation of lithium hydroxide products with low silicon content and improve economic value and market competitiveness. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a deep desiliconization method in the production process of lithium hydroxide. For lithium hydroxide causticizing liquid, a desiliconizing agent is first added to carry out a first-stage desiliconization, and the obtained first-stage desiliconizing liquid is continuously added with a desiliconizing agent for a second-stage desiliconization, and the obtained second-stage desiliconizing liquid is used to prepare lithium hydroxide; the desiliconizing agent includes a precipitant, an inorganic flocculant and an organic flocculant. The deep desiliconization method of the present invention adopts a method of chemical precipitation-adsorption combined with flocculation and sedimentation, and the precipitant and the inorganic flocculant are used for synergistic desiliconization. The precipitant and the impurity silicon form silica gel particles with surface charge, the inorganic flocculant produces adsorption and polymerization to strengthen desiliconization, and the organic flocculant can improve the sedimentation effect and the filtering effect, and the silicon in the lithium hydroxide causticizing liquid can be deeply removed. The whole process does not introduce new impurities, does not cause lithium loss, and does not cause secondary environmental protection and safety problems; the deep desiliconization method of the present invention has the advantages of low cost, high efficiency, simple operation, low energy consumption, wide range of main metal ion concentration treatment, economy and environmental protection, etc., and is suitable for further promotion and use.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The object of the present invention is to provide a deep desiliconization method in a lithium hydroxide production process, the deep desiliconization method comprising the following steps:

[0010] (1) preparing a lithium hydroxide caustic solution, adding a desiliconizing agent to carry out a first-stage desiliconization, and performing a first-stage solid-liquid separation to obtain a first-stage desiliconized slag and a first-stage desiliconized liquid;

[0011] (2) adding a desiliconizing agent to the first desiliconizing liquid to carry out second desiliconization, and performing second-stage solid-liquid separation to obtain second-stage desiliconization slag and second-stage desiliconization liquid, wherein the second-stage desiliconization liquid is used to prepare lithium hydroxide;

[0012] Wherein, the desiliconizing agent includes a precipitant, an inorganic flocculant and an organic flocculant.

[0013] The deep desiliconization method of the present invention adopts a method of chemical precipitation-adsorption combined with flocculation sedimentation. The precipitant and the inorganic flocculant are used to synergistically desiliconize. The precipitant combines with silicon to form colloidal silica particles, so that the surface of the colloidal particles is charged. The addition of inorganic flocculants produces adsorption and polymerization to enhance desiliconization, and the addition of a certain amount of organic flocculants can improve the sedimentation effect and the filtration effect. By controlling the desiliconization agent and the reaction conditions, the silicon in the lithium hydroxide solution can be deeply removed. The whole process does not introduce new impurities, does not cause lithium loss, and does not cause secondary environmental and safety problems. The deep desiliconization method of the present invention has the advantages of low cost, high efficiency, simple operation, low energy consumption, wide range of main metal ion concentration treatment, economy and environmental protection, etc., and is suitable for further promotion and use.

[0014] As a preferred technical solution of the present invention, in step (2), the second-stage desiliconization slag is returned to step (1) for recycling as a desiliconization agent, and the first-stage desiliconization is no longer added with fresh desiliconization agent.

[0015] It should be noted that the first-stage desiliconization described in the present invention is aimed at lithium hydroxide causticizing liquid with a high lithium content, and can remove most of the silicon. The small amount of silicon remaining in the first-stage desiliconization liquid will be removed by a fresh desiliconization agent in the second-stage desiliconization. The desiliconization slag obtained by the second-stage desiliconization still has a strong desiliconization performance and can be returned to step (1) for recycling as a desiliconization agent. The deep desiliconization method described in the present invention returns the second-stage desiliconization slag of the second-stage desiliconization to the first-stage desiliconization, which can realize cascade recycling, greatly save the use of desiliconization agents, achieve a reduction in the amount of desiliconization agents, save agent costs, and greatly reduce the amount of slag and lithium loss.

[0016] As a preferred technical solution of the present invention, the desiliconizing agent includes, by mass percentage, 60-90% of a precipitant, for example, 60%, 65%, 70%, 75%, 80%, 85% or 90%, etc., 9.9-39.5% of an inorganic flocculant, for example, 9.9%, 15.0%, 20.0%, 25.0%, 30.0%, 33.0%, 35.0% or 39.5%, etc., and 0.1-0.5% of an organic flocculant, for example, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc., and, by mass percentage, the sum of the mass of the precipitant, the inorganic flocculant and the organic flocculant is 100%.

[0017] As a preferred technical solution of the present invention, the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant to perform synergistic desiliconization, and then add the organic flocculant.

[0018] As a preferred technical solution of the present invention, the precipitant and the inorganic flocculant are first added, the reaction temperature is controlled to be 20-90°C, for example, 20°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 90°C, etc., preferably 30-80°C, the reaction time is 20-120min, for example, 20min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 80min, 100min or 120min, etc., preferably 30-60min, the stirring speed is 200-600r / min, for example, 200r / min, 300r / min, 350r / min, 400r / min, 450r / min, 500r / min or 600r / min, etc., preferably 300 ~500r / min, for synergistic desiliconization; then add the organic flocculant, control the stirring speed to 50~200r / min, for example, 50r / min, 60r / min, 70r / min, 80r / min, 90r / min, 100r / min, 120r / min, 150r / min, 180r / min or 200r / min, etc., preferably 50~100r / min, the reaction time is 2~20min, for example, 2min, 4min, 6min, 8min, 10min, 15min or 20min, etc., preferably 2~10min, the sedimentation time is 0~120min, for example, 0min, 10min, 20min, 30min, 40min, 50min, 60min, 90min or 120min, etc., preferably 20~60min.

[0019] It should be noted that the sedimentation time after adding the organic flocculant can be 0 min, that is, in actual situations, the colloidal silica particles may be aggregated and sedimented during the addition of the organic flocculant, and the filtration requirements can be met. In this case, after the organic flocculant is added, there is no need for sedimentation waiting time, and filtration can be performed directly.

[0020] As a preferred technical solution of the present invention, compared with the volume of the lithium hydroxide causticizing solution in step (1), the amount of the precipitant added is 0.5-20 g / L, for example, 0.5 g / L, 1 g / L, 5 g / L, 8 g / L, 10 g / L, 15 g / L or 20 g / L, the amount of the inorganic flocculant added is 0.05-13 g / L, for example, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 3 g / L, 5 g / L, 7 g / L, 10 g / L or 13 g / L, and the amount of the organic flocculant added is 0.02-0.10 g / L, for example, 0.02 g / L, 0.03 g / L, 0.05 g / L, 0.07 g / L or 0.10 g / L.

[0021] It should be noted that when the deep desiliconization method of the present invention reaches a normal and stable state, all the second-stage desiliconization slag is returned to step (1) for recycling as a desiliconization agent, and no fresh desiliconization agent is added to the first-stage desiliconization. The desiliconization agent added in the second-stage desiliconization is added according to the aforementioned addition amount; when the deep desiliconization method of the present invention is in the start-up stage before the normal and stable state, it is necessary to add fresh desiliconization agent to the first-stage desiliconization and the second-stage desiliconization respectively, then the total desiliconization agent used in the two-stage desiliconization is added according to the aforementioned addition amount. Preferably, the ratio of the addition amount of the desiliconization agent in the second-stage desiliconization to the addition amount of the desiliconization agent in the first-stage desiliconization is (1~4):1. The addition amount of the desiliconization agent in the second-stage desiliconization is relatively large, which can effectively ensure that the silicon content in the second-stage desiliconization liquid meets the standard, and can be used to prepare high-purity lithium hydroxide.

[0022] It should be noted that the amount of the organic flocculant added is 0.02-0.10 g / L, which refers to the pure amount of the organic flocculant added. However, in actual application, the organic flocculant needs to be diluted with water. For example, if the mass fraction of the dilution is 0.5%, the amount of the dilution added is 4-20 g / L.

[0023] As a preferred technical solution of the present invention, the precipitant includes any one of calcium agent, magnesium agent or iron agent or a combination of at least two of them; the inorganic flocculant includes any one of polyferric sulfate, polyferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric aluminum sulfate or polyferric aluminum chloride or a combination of at least two of them; the organic flocculant includes any one of polyacrylamide, polyquaternary ammonium salt or polyether or a combination of at least two of them.

[0024] Preferably, the calcium agent includes any one of calcium oxide, calcium hydroxide, calcium sulfate or calcium chloride, or a combination of at least two thereof;

[0025] Preferably, the magnesium agent includes any one of magnesium oxide, magnesium hydroxide, magnesium chloride or magnesium sulfate, or a combination of at least two thereof;

[0026] Preferably, the iron agent includes any one of ferric chloride, ferric hydroxide or ferric sulfate, or a combination of at least two thereof.

[0027] As a preferred technical solution of the present invention, the lithium hydroxide causticizing solution in step (1) is derived from a causticizing process of a lithium carbonate causticizing method; in the lithium hydroxide causticizing solution in step (1), the lithium content is 0.5-80 g / L, for example, 0.5 g / L, 1 g / L, 3 g / L, 5 g / L, 10 g / L, 20 g / L, 40 g / L, 50 g / L, 60 g / L or 80 g / L, etc., the silicon content is 15-180 mg / L, for example, 15 mg / L, 30 mg / L, 50 mg / L, 70 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 140 mg / L, 160 mg / L or 180 mg / L, etc., and the pH is 12-14, for example, 12, 12.5, 13, 13.5 or 14, etc.

[0028] As a preferred technical solution of the present invention, the first stage desiliconization slag in step (1) is used to prepare the alkaline emulsion required for the causticization process.

[0029] As a preferred technical solution of the present invention, the silicon content in the second-stage desiliconization liquid in step (2) is ≤5 mg / L and is used to prepare lithium hydroxide.

[0030] As a preferred technical solution of the present invention, after the deep desiliconization method reaches a normal stable state, it comprises the following steps:

[0031] (1) preparing a lithium hydroxide caustic solution, adding the second-stage desiliconization slag of step (2) as a desiliconization agent to perform a first-stage desiliconization, and performing a first-stage solid-liquid separation to obtain a first-stage desiliconization slag and a first-stage desiliconization liquid;

[0032] The lithium hydroxide causticizing solution is derived from the causticizing process of lithium carbonate causticizing method, and the lithium content of the lithium hydroxide causticizing solution is 0.5-80 g / L, the silicon content is 15-180 mg / L, and the pH is 12-14; the first-stage desiliconization slag is used to prepare the alkaline emulsion required for the causticizing process;

[0033] (2) adding a desiliconizing agent to the first desiliconizing liquid to carry out second desiliconization, and performing second-stage solid-liquid separation to obtain second-stage desiliconizing slag and second-stage desiliconizing liquid, wherein the second-stage desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second-stage desiliconizing liquid is used to prepare lithium hydroxide;

[0034] Wherein, the desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; in terms of mass percentage, the desiliconizing agent comprises 60-90% of the precipitant, 9.9-39.5% of the inorganic flocculant and 0.1-0.5% of the organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 0.5-20 g / L, the amount of the inorganic flocculant added is 0.05-13 g / L, and the amount of the organic flocculant added is 0.02-0.10 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, and control the reaction temperature to 20~90℃, preferably 30~80℃, reaction time is 20~120min, preferably 30~60min, stirring speed is 200~600r / min, preferably 300~500r / min, for synergistic desiliconization, then add the organic flocculant, control the stirring speed to 50~200r / min, preferably 50~100r / min, reaction time is 2~20min, preferably 2~10min, sedimentation time is 0~120min, preferably 20~60min; the silicon content in the second-stage desiliconization liquid is ≤5mg / L, which is used to prepare lithium hydroxide.

[0035] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0036] (1) The deep desiliconization method of the present invention adopts a method of chemical precipitation-adsorption combined with flocculation sedimentation. The precipitant and the inorganic flocculant are used to synergistically desiliconize. The precipitant combines with silicon to form colloidal silica particles, so that the surface of the colloidal particles is charged. The addition of inorganic flocculants produces adsorption and polymerization to enhance desiliconization, and the addition of a certain amount of organic flocculants can improve the sedimentation effect and the filtration effect. By controlling the desiliconization agent and the reaction conditions, the silicon in the lithium hydroxide solution can be deeply removed. The whole process does not introduce new impurities, does not cause lithium loss, and does not cause secondary environmental protection and safety problems;

[0037] (2) The deep desiliconization method of the present invention has the advantages of low cost, high efficiency, simple operation, low energy consumption, wide range of main metal ion concentration treatment, economy and environmental protection, etc., and is suitable for further promotion and use;

[0038] (3) The deep desiliconization method of the present invention returns the second-stage desiliconization slag of the second-stage desiliconization to the first-stage desiliconization, which can realize cascade recycling, greatly save the use of desiliconization agents, achieve a reduction in the amount of desiliconization agents, save agent costs, and greatly reduce the slag volume and lithium loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a process flow chart of the deep desiliconization method in the lithium hydroxide production process of the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0041] The present invention provides a deep desiliconization method in the lithium hydroxide production process, such as Figure 1 As shown, after the deep desiliconization method reaches a normal stable state, it includes the following steps:

[0042] (1) preparing a lithium hydroxide caustic solution, adding the second-stage desiliconization slag of step (2) as a desiliconization agent to perform a first-stage desiliconization, and performing a first-stage solid-liquid separation (e.g., filter pressing) to obtain a first-stage desiliconization slag and a first-stage desiliconization liquid;

[0043] The lithium hydroxide causticizing liquid is derived from the causticizing process of the lithium carbonate causticizing method; the causticizing process of the lithium carbonate causticizing method comprises: causticizing 1 reaction of water and an alkaline reagent (such as quicklime / calcium oxide), and then causticizing 2 reaction of the obtained alkaline emulsion (such as lime emulsion) with lithium carbonate, and filtering to obtain causticizing slag and lithium hydroxide causticizing liquid; the lithium content of the lithium hydroxide causticizing liquid is 0.5-80 g / L, the silicon content is 15-180 mg / L, and the pH is 12-14; under normal working conditions, the causticizing slag is all calcined and returned to the causticizing 1 reaction for recycling as an alkaline reagent, and when the impurity elements in the reaction system are enriched to a certain extent, a part of the causticizing slag is taken out, washed with water, and the lithium therein is recovered and returned to the causticizing 1 reaction in the form of washed liquid, and the washed causticizing slag is treated as solid waste / used for other purposes; and the first stage desiliconized slag is returned to the causticizing 1 reaction for preparing the alkaline emulsion required for the causticizing process;

[0044] (2) adding a desiliconizing agent to the first desiliconizing liquid to carry out second desiliconization, and performing second-stage solid-liquid separation to obtain second-stage desiliconizing slag and second-stage desiliconizing liquid, wherein the second-stage desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second-stage desiliconizing liquid is used to prepare lithium hydroxide;

[0045] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; in terms of mass percentage, the desiliconizing agent comprises 60-90% of the precipitant, 9.9-39.5% of the inorganic flocculant and 0.1-0.5% of the organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 0.5-20 g / L, the amount of the inorganic flocculant added is 0.05-13 g / L, and the amount of the organic flocculant added is 0.02-0.10 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to be 20-90° C., preferably 30-80° C., and the reaction time to be 20-120 min. Preferably, the reaction time is 30 to 60 minutes, the stirring speed is 200 to 600 r / min, preferably 300 to 500 r / min, and synergistic desiliconization is carried out. Then, the organic flocculant is added, and the stirring speed is controlled to be 50 to 200 r / min, preferably 50 to 100 r / min. The reaction time is 2 to 20 minutes, preferably 2 to 10 minutes, and the sedimentation time is 0 to 120 minutes, preferably 20 to 60 minutes. The silicon content in the second-stage desiliconization liquid is ≤5 mg / L, and it is used to prepare lithium hydroxide. It should be noted that when the impurity concentration in the second-stage desiliconization liquid is still high, for example, when the concentration of calcium, aluminum and other ions is high, the second-stage desiliconization liquid can be first subjected to resin decontamination and then used to prepare lithium hydroxide.

[0046] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0047] Example 1

[0048] This embodiment provides a deep desiliconization method in a lithium hydroxide production process. After the deep desiliconization method reaches a normal stable state, it comprises the following steps:

[0049] (1) preparing a lithium hydroxide caustic solution, adding the second-stage desiliconization slag of step (2) as a desiliconization agent to perform a first-stage desiliconization, and using filter press as a first-stage solid-liquid separation to obtain a first-stage desiliconization slag and a first-stage desiliconization liquid;

[0050] The lithium hydroxide causticizing solution is derived from the causticizing process of lithium carbonate causticizing method; the lithium hydroxide causticizing solution has a lithium content of 50 g / L, a silicon content of 120 mg / L, and a pH of 14; the first-stage desiliconization slag is used to prepare the alkaline emulsion required for the causticizing process;

[0051] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0052] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is magnesium oxide, the inorganic flocculant is polyferric chloride, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 70% precipitant, 29.7% inorganic flocculant and 0.3% organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 14 g / L, the amount of the inorganic flocculant added is 5.94 g / L, and the amount of the organic flocculant added is 0.06 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to 60°C, the reaction time to 50 min, and the stirring speed to 400 r / min for synergistic desiliconization, and then add the organic flocculant, control the stirring speed to 100 r / min, the reaction time to 10 min, and the sedimentation time to 50 min.

[0053] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid is 3.7 mg / L, which meets the requirement that the silicon content in the second-stage desiliconization liquid is ≤5 mg / L and is used for the preparation of lithium hydroxide.

[0054] Example 2

[0055] This embodiment provides a deep desiliconization method in a lithium hydroxide production process. After the deep desiliconization method reaches a normal stable state, it comprises the following steps:

[0056] (1) preparing a lithium hydroxide caustic solution, adding the second-stage desiliconization slag of step (2) as a desiliconization agent to perform a first-stage desiliconization, and using filter press as a first-stage solid-liquid separation to obtain a first-stage desiliconization slag and a first-stage desiliconization liquid;

[0057] The lithium hydroxide causticizing solution is derived from the causticizing process of lithium carbonate causticizing method; the lithium hydroxide causticizing solution has a lithium content of 80 g / L, a silicon content of 180 mg / L, and a pH of 14; the first-stage desiliconization slag is used to prepare the alkaline emulsion required for the causticizing process;

[0058] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0059] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is magnesium oxide, the inorganic flocculant is polyferric chloride, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 90% of the precipitant, 9.9% of the inorganic flocculant, and 0.1% of the organic flocculant; compared with the volume of the lithium hydroxide causticizing solution in step (1), the amount of the precipitant added is 18 g / L, the amount of the inorganic flocculant added is 1.98 g / L, and the amount of the organic flocculant added is 0.02 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to 30°C, the reaction time to 60 min, and the stirring speed to 300 r / min to perform synergistic desiliconization, and then add the organic flocculant, control the stirring speed to 50 r / min, the reaction time to 10 min, and the sedimentation time to 20 min.

[0060] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid is 4.1 mg / L, which meets the requirement that the silicon content in the second-stage desiliconization liquid is ≤5 mg / L and is used for preparing lithium hydroxide.

[0061] Example 3

[0062] This embodiment provides a deep desiliconization method in a lithium hydroxide production process. After the deep desiliconization method reaches a normal stable state, it comprises the following steps:

[0063] (1) preparing a lithium hydroxide caustic solution, adding the second-stage desiliconization slag of step (2) as a desiliconization agent to perform a first-stage desiliconization, and using filter press as a first-stage solid-liquid separation to obtain a first-stage desiliconization slag and a first-stage desiliconization liquid;

[0064] The lithium hydroxide causticizing solution is derived from the causticizing process of lithium carbonate causticizing method; the lithium content of the lithium hydroxide causticizing solution is 60 g / L, the silicon content is 160 mg / L, and the pH is 14; the first stage desiliconization slag is used to prepare the alkaline emulsion required for the causticizing process;

[0065] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0066] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is magnesium oxide, the inorganic flocculant is polyferric chloride, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 60% precipitant, 39.5% inorganic flocculant and 0.5% organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 12 g / L, the amount of the inorganic flocculant added is 7.9 g / L, and the amount of the organic flocculant added is 0.10 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to 80°C, the reaction time to 30 min, and the stirring speed to 500 r / min for synergistic desiliconization, and then add the organic flocculant, control the stirring speed to 100 r / min, the reaction time to 8 min, and the sedimentation time to 20 min.

[0067] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid is 4.3 mg / L, which meets the requirement that the silicon content in the second-stage desiliconization liquid is ≤5 mg / L and is used for the preparation of lithium hydroxide.

[0068] Example 4

[0069] This embodiment provides a deep desiliconization method in the lithium hydroxide production process. Compared with Embodiment 1, the only difference is that in step (2), the second-stage desiliconization slag is no longer returned to the first-stage desiliconization as a desiliconization agent. On the basis of the second-stage desiliconization, an additional desiliconization agent is provided to be added to the first-stage desiliconization.

[0070] The specific contents are as follows:

[0071] (1) preparing a lithium hydroxide caustic solution, adding a desiliconizing agent to perform a first stage of desiliconization, and using filter press as a first stage of solid-liquid separation to obtain a first stage of desiliconized slag and a first stage of desiliconized liquid;

[0072] The lithium hydroxide causticizing solution is derived from the causticizing process of lithium carbonate causticizing method; the lithium hydroxide causticizing solution has a lithium content of 50 g / L, a silicon content of 120 mg / L, and a pH of 14; the first-stage desiliconization slag is used to prepare the alkaline emulsion required for the causticizing process;

[0073] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is magnesium oxide, the inorganic flocculant is polyferric chloride, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 70% precipitant, 29.7% inorganic flocculant and 0.3% organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 7 g / L, the amount of the inorganic flocculant added is 2.97 g / L, and the amount of the organic flocculant added is 0.03 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to 60°C, the reaction time to 50 min, and the stirring speed to 400 r / min for synergistic desiliconization, and then add the organic flocculant, control the stirring speed to 100 r / min, the reaction time to 10 min, and the sedimentation time to 50 min;

[0074] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0075] The desiliconizing agent comprises a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is magnesium oxide, the inorganic flocculant is polyferric chloride, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 70% precipitant, 29.7% inorganic flocculant and 0.3% organic flocculant; compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 14 g / L, the amount of the inorganic flocculant added is 5.94 g / L, and the amount of the organic flocculant added is 0.06 g / L; the order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant, control the reaction temperature to 60°C, the reaction time to 50 min, and the stirring speed to 400 r / min for synergistic desiliconization, and then add the organic flocculant, control the stirring speed to 100 r / min, the reaction time to 10 min, and the sedimentation time to 50 min.

[0076] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid is 3.5 mg / L, which meets the requirement that the silicon content in the second-stage desiliconization liquid is ≤5 mg / L and is used to prepare lithium hydroxide; however, in this embodiment, since the second-stage desiliconization slag of the second-stage desiliconization is not returned to the first-stage desiliconization, no cascade recycling is carried out, the amount of desiliconization agent used is increased, and the agent cost is increased.

[0077] Comparative Example 1

[0078] This comparative example provides a desiliconization method in the lithium hydroxide production process. Compared with Example 1, the only difference is that the inorganic flocculant in the desiliconization agent is replaced by an organic flocculant, that is, the desiliconization agent only includes a precipitant and an organic flocculant.

[0079] The specific contents of step (2) are as follows:

[0080] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0081] The desiliconizing agent comprises a precipitant and an organic flocculant; the precipitant is magnesium oxide, and the organic flocculant is polyacrylamide; in terms of mass percentage, the desiliconizing agent comprises 70% of the precipitant and 30% of the organic flocculant; compared with the volume of the lithium hydroxide causticizing solution in step (1), the amount of the precipitant added is 14 g / L, and the amount of the organic flocculant added is 6 g / L; the order of adding the desiliconizing agent is to first add the precipitant, control the reaction temperature to 60°C, the reaction time to 50 min, and the stirring speed to 400 r / min, then add the organic flocculant, control the stirring speed to 100 r / min, the reaction time to 10 min, and the sedimentation time to 50 min.

[0082] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid was 40.2 mg / L, which did not meet the requirement that the silicon content in the second-stage desiliconization liquid was ≤5 mg / L, resulting in a higher content of impurity silicon in the prepared lithium hydroxide.

[0083] Comparative Example 2

[0084] This comparative example provides a desiliconization method in the lithium hydroxide production process. Compared with Example 1, the only difference is that the organic flocculant in the desiliconization agent is replaced by an inorganic flocculant, that is, the desiliconization agent only includes a precipitant and an inorganic flocculant.

[0085] The specific contents of step (2) are as follows:

[0086] (2) adding a desiliconizing agent to the first desiliconizing liquid to perform a second desiliconization, using filter press as the second solid-liquid separation to obtain a second desiliconizing slag and a second desiliconizing liquid, the second desiliconizing slag is returned to step (1) for recycling as a desiliconizing agent, and no fresh desiliconizing agent is added to the first desiliconization, and the second desiliconizing liquid is used to prepare lithium hydroxide;

[0087] The desiliconization agent comprises a precipitant and an inorganic flocculant; the precipitant is magnesium oxide, and the inorganic flocculant is polyferric chloride; in terms of mass percentage, the desiliconization agent comprises 70% of the precipitant and 30% of the inorganic flocculant; compared with the volume of the lithium hydroxide causticizing liquid in step (1), the amount of the precipitant added is 14 g / L, and the amount of the inorganic flocculant added is 6 g / L; the precipitant and the inorganic flocculant are added, the reaction temperature is controlled to be 60°C, the reaction time is 50 min, and the stirring speed is 400 r / min to carry out synergistic desiliconization.

[0088] After detection by ICP-AES spectrometer, the silicon content in the obtained second-stage desiliconization liquid was 15.9 mg / L, which did not meet the requirement that the silicon content in the second-stage desiliconization liquid was ≤5 mg / L, resulting in a higher content of impurity silicon in the prepared lithium hydroxide.

[0089] In summary, the present invention provides a deep desiliconization method in the production process of lithium hydroxide. For the lithium hydroxide causticized liquid, a desiliconizing agent is first added to carry out a first-stage desiliconization, and the first-stage desiliconized liquid is further added with a desiliconizing agent to carry out a second-stage desiliconization. The obtained second-stage desiliconized liquid is used to prepare lithium hydroxide; the desiliconizing agent includes a precipitant, an inorganic flocculant and an organic flocculant. The deep desiliconization method of the present invention adopts a method of chemical precipitation-adsorption combined with flocculation sedimentation. Through the synergistic desiliconization of a precipitant and an inorganic flocculant, the precipitant and impure silicon form colloidal silica particles with surface charge. The inorganic flocculant produces adsorption and polymerization to enhance desiliconization, while the organic flocculant can improve the sedimentation effect and the filtration effect. The silicon in the lithium hydroxide causticized liquid can be deeply removed. The whole process does not introduce new impurities, does not cause lithium loss, and does not cause secondary environmental and safety problems. The deep desiliconization method of the present invention has the advantages of low cost, high efficiency, simple operation, low energy consumption, wide range of main metal ion concentration treatment, economy and environmental protection, etc., and is suitable for further promotion and use. The silicon content in the two-stage desiliconization liquid of the present invention is ≤5mg / L, which is used to prepare lithium hydroxide.

[0090] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0091] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0092] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0093] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A deep desiliconization method in a lithium hydroxide production process, characterized in that: The deep desiliconization method comprises the following steps: (1) preparing a lithium hydroxide caustic solution, adding a desiliconizing agent to carry out a first-stage desiliconization, and performing a first-stage solid-liquid separation to obtain a first-stage desiliconized slag and a first-stage desiliconized liquid; (2) adding a desiliconizing agent to the first desiliconizing liquid to carry out second desiliconization, and performing second-stage solid-liquid separation to obtain second-stage desiliconization slag and second-stage desiliconization liquid, wherein the second-stage desiliconization liquid is used to prepare lithium hydroxide; Wherein, the desiliconizing agent includes a precipitant, an inorganic flocculant and an organic flocculant; the precipitant is any one of a calcium agent, a magnesium agent or an iron agent or a combination of at least two thereof; the inorganic flocculant includes any one of polyferric sulfate, polyferric chloride, polyaluminum chloride, polyaluminum sulfate, polyferric aluminum sulfate or polyferric aluminum chloride or a combination of at least two thereof; the organic flocculant includes any one of polyacrylamide, polyquaternary ammonium salt or polyether or a combination of at least two thereof; The lithium hydroxide causticizing solution of step (1) is derived from the causticizing process of lithium carbonate causticizing method; the lithium hydroxide causticizing solution of step (1) has a lithium content of 0.5-80 g / L, a silicon content of 15-180 mg / L, and a pH of 12-14; In step (2), the second-stage desiliconization slag is returned to step (1) for recycling as a desiliconization agent, while the first-stage desiliconization is no longer added with fresh desiliconization agent; The silicon content in the second-stage desiliconization liquid in step (2) is ≤5 mg / L and is used to prepare lithium hydroxide.

2. The deep desiliconization method in the lithium hydroxide production process according to claim 1, characterized in that: In terms of mass percentage, the desiliconizing agent includes 60-90% of a precipitant, 9.9-39.5% of an inorganic flocculant, and 0.1-0.5% of an organic flocculant.

3. The deep desiliconization method in the lithium hydroxide production process according to claim 1, characterized in that: The order of adding the desiliconizing agent is to first add the precipitant and the inorganic flocculant to perform synergistic desiliconization, and then add the organic flocculant.

4. The deep desiliconization method in the lithium hydroxide production process according to claim 3, characterized in that: First, the precipitant and the inorganic flocculant are added, the reaction temperature is controlled to be 20-90°C, the reaction time is 20-120min, and the stirring speed is 200-600r / min to carry out synergistic desiliconization; then the organic flocculant is added, the stirring speed is controlled to be 50-200r / min, the reaction time is 2-20min, and the sedimentation time is 0-120min.

5. The deep desiliconization method in the lithium hydroxide production process according to claim 1, characterized in that: Compared with the volume of the lithium hydroxide caustic solution in step (1), the amount of the precipitant added is 0.5-20 g / L, the amount of the inorganic flocculant added is 0.05-13 g / L, and the amount of the organic flocculant added is 0.02-0.10 g / L.

6. The deep desiliconization method in the lithium hydroxide production process according to claim 1, characterized in that: The first stage desiliconized slag in step (1) is used to prepare the alkaline emulsion required for the causticizing process.

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