Method for desiliconizing and efficiently separating lithium-containing solution

Abstract

The invention discloses a lithium-containing solution desiliconization and efficient separation method which comprises the following steps: step 1, dropwise adding alkali liquor into a lithium-containing solution under a stirring condition to adjust the pH value to a set value so as to form a precipitate, and then keeping the pH value unchanged for a set time so as to finally obtain a turbid liquid; step 2, adding a filter aid into the turbid liquid obtained in the step 1, uniformly stirring and mixing, and then carrying out solid-liquid separation; and step 3, crushing a filter cake obtained by solid-liquid separation in the step 2, dissolving with an acid solution, filtering to recover the filter aid, returning the filter aid to the step 2 for reuse, and returning the remaining waste liquid to a waste liquid pool. According to the method, the brine characteristic of the lithium-containing solution is utilized, magnesium salt, calcium salt, ferric salt or aluminum salt and other agents do not need to be added, and efficient desilicication is achieved. According to the invention, the coagulation-aiding settling performance of the filter aid is utilized to agglomerate the silicon precipitate so as to improve the filtration rate, and in addition, the filter cake after filtration is subjected to acid dissolution so as to separate and obtain the filter aid, so that the reuse of the filter aid is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from salt lakes, and in particular to a method for desiliconization and efficient separation of a lithium-containing solution. Background Art

[0002] Lithium possesses numerous excellent physical and chemical properties and boasts a wide range of functions and applications, earning it the reputation of "the energy metal that drives global progress." With the rapid development of new energy, metallurgy, aerospace, and glass manufacturing industries, demand for lithium is increasing year by year, and the technological development of lithium extraction processes is gaining increasing attention.

[0003] The main types of lithium resources include brine (salt lake brine, geothermal brine, etc.), hard rock (spodumene, lepidolite, lepidolite, etc.), and clay (lithium clay, etc.). Salt lake brine, spodumene, and lepidolite are the three main types of lithium resources, all of which have been industrially mined and smelted. However, due to the silicon impurities contained in these resources, whether lithium is extracted from salt lake brine or from ores (spodumene, lepidolite), silicon impurities are introduced into the system and enter the lithium-containing solution. However, during the concentration and purification of the lithium-containing solution to produce lithium carbonate, the silicon impurities will continue to accumulate through subsequent concentration steps, placing a serious burden on the back-end process. For example, they can cause scaling of the back-end membranes and scaling of the tubes in the MVR (Mechanical Steam Recompression Evaporation) evaporation heat exchanger, affecting heat transfer efficiency and reducing evaporation intensity. Furthermore, they can further affect the purity of the lithium product. Therefore, desiliconization of the lithium-containing solution is generally required during the subsequent preparation of lithium products.

[0004] Current desiliconization methods include coagulation desiliconization, reverse osmosis desiliconization, electrocoagulation desiliconization, and ion exchange desiliconization. Coagulation desiliconization is characterized by its simplicity, ease of operation, and low investment costs. However, the coagulation desiliconization process easily forms silica gel, which places significant strain on filtration. Furthermore, the high water content of silica gel leads to significant lithium loss. Reverse osmosis desiliconization cannot achieve the selective separation of lithium and silicon in lithium-containing solutions, limiting its scope of application. Electrocoagulation desiliconization significantly increases aluminum and electricity consumption and introduces foreign matter. Ion exchange desiliconization has high investment costs and requires large amounts of acid and alkali.

[0005] In summary, no matter which of the above-mentioned desiliconization processes is used for lithium-containing solutions, there will be many problems. Therefore, a new desiliconization and separation process needs to be developed based on the characteristics of lithium-containing solutions. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention aims to provide a method for desiliconization and efficient separation of lithium-containing solutions.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for desiliconization and efficient separation of a lithium-containing solution comprises the following steps:

[0009] Step 1: adding an alkali solution dropwise to the lithium-containing solution under stirring to adjust the pH to a set value to form a precipitate, and then maintaining the pH constant for a set time to finally obtain a suspension;

[0010] Step 2: adding a filter aid to the suspension obtained in step 1, mixing the mixture uniformly by stirring, and then performing solid-liquid separation;

[0011] Step 3: crush the filter cake obtained by solid-liquid separation in step 2, dissolve it with acid, then filter and recover the filter aid and return it to step 2 for reuse, and return the remaining waste liquid to the waste liquid pool.

[0012] Furthermore, in step 1, the lithium ion concentration in the lithium-containing solution is 1-5 g / L, the magnesium ion concentration is 200-600 mg / L, the calcium ion concentration is 50-200 mg / L, and the silicon ion concentration is 30-120 mg / L.

[0013] Furthermore, in step 1, the alkali solution is a solution of one or a combination of several of NaOH, KOH, and LiOH.

[0014] Furthermore, in step 1, the set pH value is 10.5-11, and the set time is 0.5-1h.

[0015] Furthermore, in step 2, the filter aid is one or a combination of diatomaceous earth and perlite.

[0016] Furthermore, in step 2, the amount of the filter aid added is 0.1-1% of the weight of the suspension, and the stirring time is 5-30 minutes.

[0017] Furthermore, in step 2, the solid-liquid separation method is one or a combination of plate and frame filtration, bag filtration, and candle filtration.

[0018] Furthermore, in step three, the acid solution is a solution of one or a combination of HCl, H2SO4, and HNO3.

[0019] Furthermore, in step three, the amount of the acid used is 1-1.5 times the molar amount of the base added in step one.

[0020] The beneficial effects of the present invention are:

[0021] 1. The method of the present invention utilizes alkaline earth metals (magnesium and calcium) in lithium-containing solutions and adjusts the pH to precipitate and desiliconize them to form silicon precipitates. Compared with traditional silicon removal processes, the method of the present invention utilizes the characteristics of brine containing lithium solutions and does not require the addition of magnesium salts, calcium salts, iron salts or aluminum salts, thereby achieving efficient desiliconization.

[0022] 2. The present invention utilizes the coagulation and sedimentation performance of the filter aid to agglomerate the silicon precipitate to increase the filtration rate. In addition, the present invention acid-dissolves the filter cake after filtration to separate the filter aid, thereby realizing the reuse of the filter aid.

[0023] Therefore, the present invention has the characteristics of simple operation, low running cost, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the method of Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0026] Example 1

[0027] This embodiment provides a method for desiliconization and efficient separation of a lithium-containing solution, wherein the lithium-containing solution contains Li 1.4g / L, Na 500mg / L, K 120mg / L, Mg 200mg / L, Ca 70mg / L, Si 45mg / L, and Cl 8g / L. Figure 1 The specific process is as follows:

[0028] Take 300mL of the above lithium-containing solution, add 80g / L NaOH solution dropwise to the lithium-containing solution under stirring conditions of 250rpm until the pH is 11, so that it precipitates to form silicon precipitates, and maintain the pH unchanged for 30min to finally obtain a suspension. Then add 0.2% of the weight of the suspension as a filter aid perlite to the suspension and stir and mix to make it uniform. After stirring for 5 minutes, vacuum filtration is performed, and the filter paper pore size is 20um and the filtration area is 12.56cm 2 The pressure during filtration was 0.065 MPa, the filtration time was 28 min, and the filtration speed was 510 LMH.

[0029] The silicon concentration in the filtered filtrate was determined to be 1.5 mg / L. The filter cake was crushed and dissolved in 2 mol / L hydrochloric acid solution, then filtered to obtain perlite as a filter aid, which was returned for reuse. The amount of 2 mol / L hydrochloric acid solution added was approximately 1.7 g, with the molar amount of HCl added being 1.5 times the molar amount of NaOH added.

[0030] Example 2

[0031] This embodiment provides a method for desiliconization and efficient separation of a lithium-containing solution, wherein the lithium-containing solution is the same as that in Example 1. Figure 1 The specific process is as follows:

[0032] Take 5L of lithium-containing solution and add 80g / L NaOH solution dropwise to the lithium-containing solution under stirring at 250rpm until the pH reaches 10.5, so that it precipitates to form silica gel and maintains the pH constant for 30min. Then, add diatomaceous earth as a filter aid at a weight ratio of 0.2% of the suspension to the resulting suspension and stir and mix to make it uniform. After 5 minutes, use plate and frame filter press with a filter cloth pore size of 12.5um and a filtration area of ​​52.78m 2 The filtration pressure was 0.65 MPa, the filtration time was 23 minutes, and the filtration rate was 2453 LMH. The silicon concentration in the filtrate was determined to be 5 mg / L. The filter cake was crushed and dissolved in 2 mol / L hydrochloric acid solution before filtration to obtain diatomaceous earth as a filter aid, which was then recycled. The amount of 2 mol / L hydrochloric acid solution added was approximately 28.3 g, with the molar amount of HCl added being 1.25 times the molar amount of NaOH added.

[0033] Example 3

[0034] This embodiment provides a method for desiliconization and efficient separation of a lithium-containing solution, wherein the lithium-containing solution contains Li 4g / L, Na 1500mg / L, K 360mg / L, Mg 600mg / L, Ca 200mg / L, Si 110mg / L, and Cl 24g / L. Figure 1 The specific process is as follows:

[0035] 5L of the lithium-containing solution was added dropwise to an 80g / L NaOH solution at 250rpm stirring until the pH reached 11, causing it to precipitate into silica gel. The pH was then maintained constant for 30 minutes. Perlite, a filter aid, was then added to the resulting suspension at a concentration of 1% by weight of the suspension and stirred to achieve uniformity. After 5 minutes, plate and frame filtration was performed using a filter cloth with a pore size of 18.75μm and a filtration area of ​​52.78m. 2 The pressure during filtration was 0.7 MPa, the filtration time was 40 min, and the filtration speed was 1409 LMH.

[0036] The silicon concentration in the filtered filtrate was measured to be 0.8 mg / L. The filter cake was crushed and dissolved in 2 mol / L hydrochloric acid solution, then filtered to obtain perlite as a filter aid, which was returned for reuse. The amount of 2 mol / L hydrochloric acid solution added was approximately 180 g, with the molar amount of HCl added being 1.5 times the molar amount of NaOH added.

[0037] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for desiliconization and efficient separation of lithium-containing solutions, characterized in that: The following steps are involved: Step 1: adding an alkali solution dropwise to the lithium-containing solution under stirring to adjust the pH to a set value to form a precipitate, and then maintaining the pH constant for a set time to finally obtain a suspension; Step 2: adding a filter aid to the suspension obtained in step 1, mixing the mixture uniformly by stirring, and then performing solid-liquid separation; Step 3: crush the filter cake obtained by solid-liquid separation in step 2, dissolve it with acid, then filter and recover the filter aid and return it to step 2 for reuse, and return the remaining waste liquid to the waste liquid pool.

2. The method according to claim 1, characterized in that In step 1, the lithium ion concentration in the lithium-containing solution is 1-5 g / L, the magnesium ion concentration is 200-600 mg / L, the calcium ion concentration is 50-200 mg / L, and the silicon ion concentration is 30-120 mg / L.

3. The method according to claim 1, characterized in that In step 1, the alkali solution is a solution of one or a combination of NaOH, KOH, and LiOH.

4. The method according to claim 1, wherein In step 1, the pH setting value is 10.5-11, and the setting time is 0.5-1h.

5. The method according to claim 1, wherein In step 2, the filter aid is one or a combination of diatomaceous earth and perlite.

6. The method according to claim 1, characterized in that In step 2, the amount of the filter aid added is 0.1-1% of the weight of the suspension, and the stirring time is 5-30 minutes.

7. The method according to claim 1, characterized in that In step 2, the solid-liquid separation method is one or a combination of plate and frame filter pressing, bag filtration, and candle filtration.

8. The method according to claim 1, characterized in that In step 3, the acid solution is a solution of one or a combination of HCl, H2SO4, and HNO3.

9. The method according to claim 1, characterized in that In step three, the amount of the acid used is 1-1.5 times the molar amount of the base added in step one.

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