A method for preparing silicon-doped titanium-based lithium ion sieves from spent titanium silicalite molecular sieves

Abstract

The application discloses a method for preparing silicon-doped titanium lithium ion sieve from waste titanium-silicon molecular sieve, and belongs to the technical field of titanium lithium ion sieve material preparation. The method realizes efficient recovery of titanium and silicon doping through the alkali treatment directional desiliconization-solid phase grinding lithium intercalation-acid washing activation process. The obtained silicon-doped titanium lithium ion sieve has the characteristics of high adsorption capacity, fast kinetics and low titanium solution loss, and is suitable for lithium extraction from high-sodium-lithium-ratio salt lake. The method is economical and environment-friendly, the resource utilization rate of waste materials is 100%, and the lithium extraction cost is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of titanium lithium ion sieve material preparation technology, specifically relating to a method for preparing silicon-doped titanium lithium ion sieves from waste titanium silicon molecular sieves. Background Technology

[0002] my country's salt lake lithium reserves account for approximately 80% of the country's total lithium reserves. To meet future lithium demand, the research and development of lithium extraction technologies from salt lakes has become crucial. In traditional brine lithium extraction processes, lithium extraction is at the very end of the process, prioritizing it after sodium and potassium extraction, which is disadvantageous from a lithium resource extraction perspective. Under the major trend of new energy transformation, the value of lithium resources is gradually increasing, urgently requiring new technologies that can achieve rapid and low-cost lithium extraction. Therefore, driven by market demand, advancing the lithium extraction process to achieve lithium extraction from raw brine is an inevitable trend in salt lake lithium extraction.

[0003] Currently, the most studied lithium adsorbents are inorganic adsorbent materials, which can be divided into two categories: aluminum salt adsorbents and ion sieve adsorbents. Ion sieve adsorbents can be further divided into manganese-based ion sieves and titanium-based ion sieves. Among them, manganese-based ion sieves have advantages such as fast adsorption rate, high adsorption capacity, and good ion selectivity. However, studies have found that during the lithium elution process, the Mn in the ion sieve framework... 3+ In H + Under certain conditions, disproportionation reactions and the John-Teller effect occur, leading to the dissolution of the ion sieve framework. This poor stability severely hinders the application of manganese-based ion sieves. Titanium-based ion sieves have gradually attracted attention in recent years, with the main types being the layered H₂TiO₃ type and the spinel-structured H₄TiSO₄ type. 12 There are two types of ion sieves. Among them, the H2TiO3 type ion sieve has a higher adsorption capacity and wider applicability than aluminum salt adsorbents, and better stability than manganese-based adsorbents. It was the second lithium adsorbent to be commercially applied after aluminum salt adsorbents. However, in practical applications, it has been found that the lithium adsorption capacity of the H2TiO3 type ion sieve is difficult to reach the theoretical value, and its performance declines with increasing cycle number during adsorption-desorption. In summary, manganese-based adsorbents show significant manganese loss during acid elution (affecting lifespan and product purity), while titanium-based adsorbents have lower loss but potentially slightly lower adsorption capacity. Therefore, how to prepare an ion sieve-type adsorbent with high adsorption capacity and low loss rate has become an urgent technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves includes the following steps:

[0007] (1) Raw material pretreatment: The waste titanium silicon molecular sieve TS-1 is calcined at high temperature to remove residual organic matter, and then treated with an inorganic acid solution with a concentration of 0.1-0.5 mol / L at 70-90℃ for 1-6 hours. After solid-liquid separation, purified TS-1 is obtained.

[0008] (2) Alkali treatment: The purified TS-1 obtained in step (1) is mixed with NaOH solution in a sealed container and reacted. The mixture is stirred at 100-200℃ for 4-24 hours, filtered, the solid is washed and kept for later use, and the filtrate is recovered.

[0009] (3) Preparation of ion sieve: The solid obtained in step (2), lithium source and ethanol are mixed and mechanically ground or ball milled thoroughly. The mixture is then transferred to a muffle furnace and calcined at 600-900℃ for 3-8 hours to obtain silicon-doped titanium lithium ion sieve.

[0010] (4) Acid washing and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in the acid washing solution for acid washing, solid-liquid separation, washing and drying to obtain the silicon-doped titanium lithium ion sieve.

[0011] Preferably, the inorganic acid in step (1) is at least one of nitric acid, hydrochloric acid or sulfuric acid, and the solid-liquid mass ratio is 1g:(15-30)ml.

[0012] Preferably, the Si / Ti molar ratio in the waste titanium-silicon molecular sieve in step (1) is 12-30:1.

[0013] Preferably, in step (1), the high-temperature roasting temperature is 600°C and the time is 6 hours.

[0014] Preferably, the concentration of the NaOH solution in step (2) is 2-10 mol / L.

[0015] Preferably, in step (2), the mass ratio of purified TS-1 to NaOH solution is 1:(10-30).

[0016] Preferably, the specific method for filtrate recovery in step (2) is as follows: the filtrate is evaporated and concentrated at 80-90℃, and the precipitate is the recovered industrial-grade sodium silicate by-product.

[0017] Preferably, in step (3), the lithium source is lithium hydroxide, lithium acetate or lithium carbonate; the atomic ratio of each material is Si:Li:Ti = 0.01-0.1:1-2:1; and the solid-liquid ratio of the solvent ethanol used in the mechanical grinding or ball milling is 5:(1-3).

[0018] Preferably, the pickling solution in step (4) is a 0.1-0.5 mol / L hydrochloric acid solution, and the pickling treatment is carried out at 40-60℃ for 4-12 hours.

[0019] The beneficial effects of this invention are as follows: This invention replaces titanium ore with waste titanium-silicon molecular sieve (TS-1), significantly reducing raw material costs. The silicon doping level is controlled through alkali treatment, and nano-SiO2 is recovered, achieving high-value utilization of waste materials. The prepared silicon-doped titanium-based lithium-ion sieve exhibits excellent selective lithium adsorption capacity in Na+. + / Li + In a 100:1 solution, the lithium-sodium selectivity coefficient α(Li / Na) is ≥280, the adsorption capacity is as high as 38.2 mg / g, the saturation time is only 30 min, the titanium loss rate during recycling is ≤0.05%, and it can be recycled for a long time. Attached Figure Description

[0020] Figure 1 This is an XRD test result diagram of Embodiment 1 of the present invention;

[0021] Figure 2 This is a TEM test result diagram of Embodiment 1 of the present invention;

[0022] Figure 3 Examples 1 and 1 of the present invention are for Li + The adsorption curve. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0024] Example 1

[0025] A method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves includes the following steps:

[0026] (1) Raw material pretreatment: 30 g of waste titanium silicon molecular sieve TS-1 (Si / Ti=20) was calcined at 600℃ for 6 hours to remove residual organic matter, and then treated with 450 mL hydrochloric acid solution (0.1 mol / L) at 70℃ for 6 hours. After solid-liquid separation, purified TS-1 was obtained.

[0027] (2) Alkali treatment: The purified TS-1 obtained in step (1) is mixed with 10 mol / L NaOH solution at a mass ratio of 1:20 in a closed container and reacted. The mixture is stirred at 150°C for 12 hours, filtered, the solid is washed and set aside, and the filtrate is concentrated by evaporation. The precipitate obtained is the industrial sodium silicate by-product.

[0028] (3) Preparation of ion sieve: The solid obtained in step (2), 0.8g of lithium carbonate and 2mL of ethanol are mixed and mechanically ground thoroughly. After drying the mixture, it is transferred to a muffle furnace and calcined at 600℃ for 8 hours to obtain silicon-doped titanium lithium ion sieve. The atomic ratio of each material is Si:Li:Ti = 0.01:1:1.

[0029] (4) Acid washing and activation: Immerse the silicon-doped titanium lithium ion sieve obtained in step (3) into 20 mL of 0.4 mol / L hydrochloric acid solution, stir at 40℃ for 12 hours, then separate the solid and liquid, wash and dry to obtain the silicon-doped titanium lithium ion sieve.

[0030] Example 2

[0031] A method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves includes the following steps:

[0032] (1) Raw material pretreatment: 30 g of waste titanium silicon molecular sieve TS-1 (Si / Ti=20) was calcined at 550℃ for 6 hours to remove residual organic matter, and then treated with 600 mL of 0.5 mol / L nitric acid solution at 90℃ for 1 hour. After solid-liquid separation, purified TS-1 was obtained.

[0033] (2) Alkali treatment: The purified TS-1 obtained in step (1) is mixed with 8 mol / L NaOH solution at a mass ratio of 1:20 in a closed container and reacted. The mixture is stirred at 180°C for 16 hours, filtered, the solid is washed and set aside, the filtrate is evaporated and concentrated, and the precipitate obtained is the industrial grade sodium silicate by-product.

[0034] (3) Preparation of ion sieve: The solid obtained in step (2), 1.5 g of lithium acetate and 3 mL of ethanol are mixed and mechanically ground thoroughly. After drying the mixture, it is transferred to a muffle furnace and calcined at 900°C for 5 hours to obtain silicon-doped titanium lithium ion sieve. The atomic ratio of each material is Si:Li:Ti = 0.1:2:1.

[0035] (4) Acid washing and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in 30 mL of 0.5 mol / L hydrochloric acid solution and acid washed at 60℃ for 4 hours. Then, solid-liquid separation, washing and drying are performed to obtain silicon-doped titanium lithium ion sieve.

[0036] Example 3

[0037] A method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves includes the following steps:

[0038] (1) Raw material pretreatment: 30 g of waste titanium silicon molecular sieve TS-1 (Si / Ti=15) was calcined at 600℃ for 6 hours to remove residual organic matter, and then treated with 900 mL of sulfuric acid solution with a concentration of 0.3 mol / L at 80℃ for 4 hours. After solid-liquid separation, purified TS-1 was obtained.

[0039] (2) Alkali treatment: The purified TS-1 obtained in step (1) is mixed with 6 mol / L NaOH solution at a mass ratio of 1:20 in a closed container and reacted. The mixture is stirred at 150°C for 20 hours, filtered, the solid is washed and set aside, and the filtrate is concentrated at high temperature. The precipitate obtained is the industrial sodium silicate by-product.

[0040] (3) Preparation of ion sieve: The solid obtained in step (2), 1.0 g of lithium carbonate and 3 mL of ethanol are mixed and mechanically ground thoroughly. After drying the mixture, it is transferred to a muffle furnace and calcined at 700°C for 6 hours to obtain silicon-doped titanium lithium ion sieve. The atomic ratio of each material is Si:Li:Ti = 0.05:1:1.

[0041] (4) Acid washing and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in 15 mL of 0.3 mol / L hydrochloric acid solution and acid washed at 50°C for 8 hours. Then, solid-liquid separation, washing and drying are performed to obtain the silicon-doped titanium lithium ion sieve.

[0042] Comparative Example 1

[0043] A method for preparing titanium-based lithium-ion sieves, comprising the following steps:

[0044] (1) Preparation of ion sieve: Weigh an appropriate amount of 1 g lithium carbonate, 3.13 g titanium hydroxide and 5 mL ethanol and mix them. Grind them thoroughly by mechanical grinding. After drying the sample, transfer it to a muffle furnace and calcine it at 600℃ for 8 hours to obtain an undoped titanium ion sieve. The atomic ratio of the material is Li:Ti = 1:1.

[0045] (2) Acid washing and activation: The titanium lithium ion sieve obtained in step (1) is immersed in 20 mL of 0.4 mol / L hydrochloric acid solution and acid washed at 40℃ for 12 hours. Then, solid-liquid separation, washing and drying are performed to obtain the titanium lithium ion sieve.

[0046] Performance testing

[0047] The samples obtained in Example 1 were subjected to XRD and TEM tests, as follows: Figure 1 and Figure 2 As shown.

[0048] Li + Adsorption performance test: The adsorption performance was tested using 1L of laboratory-prepared brine. The specific composition of the self-prepared brine is shown in Table 1 below.

[0049] Table 1 Main components of homemade brine

[0050]

[0051] Five g of the titanium lithium ion sieve samples prepared in Example 1 and Comparative Example 1 were soaked in 200 mL of laboratory-prepared brine with continuous stirring. Water samples were taken at set time points t = 0, 5, 10, 15, 20, 25, 30, 45, 60, 90, and 120 min, and the Li content was analyzed by ICP. + Content, when Li in water sample + The adsorption equilibrium is reached when the concentration no longer changes. The adsorption rate curve is shown below. Figure 3 As shown, the sample in Example 1 reached adsorption equilibrium after 30 min, with an equilibrium adsorption capacity of 38.2 mg / g; simultaneously, its lithium-sodium selectivity coefficient α(Li / Na) was measured to be ≥280, indicating that the silicon-doped titanium lithium-ion sieve obtained in this invention exhibits good lithium-sodium selectivity in salt lake brine. + It exhibits good selectivity and high adsorption capacity. In contrast, the adsorption equilibrium of Comparative Example 1 was around 90 min, and the maximum adsorption capacity was 21.9 mg / g, which is significantly lower than that of the sample obtained in Example 1 of this invention.

[0052] Titanium loss: The adsorbed sample was analyzed using 0.4 mol / L hydrochloric acid solution. The volume V (L) of the acid wash solution was collected during the elution process, and the titanium ion concentration C (mg / L) was measured. The titanium loss rate % was calculated as follows: CV / m * 100%, where m is the adsorbent mass (g). The results are shown in Table 2.

[0053] Table 2 Results of Titanium Dissolution Rate Test

[0054]

[0055] The present invention also studied the cyclic adsorption performance of the silicon-doped titanium lithium ion sieve and found that after 500 cycles of use, its maximum adsorption capacity did not show a sharp decline, which indicates that the product of the present invention has good cyclicity.

[0056] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves, characterized in that, It includes the following steps: (1) Raw material pretreatment: The waste titanium silicon molecular sieve TS-1 is calcined at high temperature to remove residual organic matter, and then treated with an inorganic acid solution with a concentration of 0.1-0.5 mol / L at 70-90℃ for 1-6 hours. After solid-liquid separation, purified TS-1 is obtained. (2) Alkali treatment: The purified TS-1 obtained in step (1) is mixed with a NaOH solution with a concentration of 2-10 mol / L in a closed container and reacted. The mixture is stirred at 100-200℃ for 4-24 hours, filtered, the solid is washed and kept for later use, and the filtrate is recovered. (3) Preparation of ion sieve: The solid obtained in step (2), lithium source and ethanol are mixed and mechanically ground thoroughly. The mixture is then transferred to a muffle furnace and calcined at 600-900℃ for 3-8 hours to obtain silicon-doped titanium lithium ion sieve. (4) Acid washing and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in the acid washing solution for acid washing, solid-liquid separation, washing and drying to obtain the silicon-doped titanium lithium ion sieve.

2. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, In step (1), the inorganic acid is at least one of nitric acid, hydrochloric acid or sulfuric acid, and the solid-liquid ratio is 1g:(15-30)ml.

3. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, In step (1), the Si / Ti molar ratio in the waste titanium-silicon molecular sieve is 12-30:

1.

4. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, In step (1), the high-temperature roasting temperature is 500-700℃ and the time is 4-8 hours.

5. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, In step (2), the mass ratio of purified TS-1 to NaOH solution is 1:(10-30).

6. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, The specific method for filtrate recovery in step (2) is as follows: the filtrate is evaporated and concentrated at 80-90℃, and the precipitate is the recovered industrial-grade sodium silicate by-product.

7. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, In step (3), the lithium source is lithium hydroxide, lithium acetate or lithium carbonate; the atomic ratio of each material is Si:Li:Ti = 0.01-0.1:1-2:1; during mechanical grinding, the solid-liquid ratio of the solvent ethanol is 5:(1-3).

8. The method for preparing silicon-doped titanium-based lithium-ion sieves from waste titanium-silicon molecular sieves according to claim 1, characterized in that, The pickling solution in step (4) is a 0.1-0.5 mol / L hydrochloric acid solution, which is pickled at 40-60℃ for 4-12 hours.

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