Method for preparing silicon-doped titanium lithium ion sieve from waste titanium silicalite molecular sieve

Abstract

The invention discloses a method for preparing a silicon-doped titanium lithium ion sieve from a waste titanium silicalite molecular sieve, and belongs to the technical field of titanium lithium ion sieve material preparation. According to the method, efficient recovery and silicon doping of titanium are realized through alkali treatment directional desilicication-solid phase grinding lithium intercalation-acid pickling activation processes. The obtained silicon-doped titanium lithium ion sieve has the characteristics of high adsorption capacity, fast dynamics and low titanium solution loss, and is suitable for extracting lithium from salt lakes with high sodium-lithium ratio. The method is economical and environment-friendly, the waste recycling rate is 100%, and the lithium extraction cost is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of lithium ion sieve materials, and particularly relates to a method for preparing silicon-doped titanium lithium ion sieve from waste titanium silicalite. BACKGROUND

[0002] The lithium resource reserves of salt lakes in China account for about 80% of the total lithium resource reserves in China. In order to meet the future demand for lithium, the research and development of lithium extraction technology from salt lakes become particularly important. In the traditional old brine lithium extraction process, lithium extraction is at the end of the whole process, and the priority of lithium extraction is after sodium extraction and potassium extraction, which is not conducive to lithium resource extraction from the perspective of lithium resource extraction. Under the trend of new energy transformation, the value of lithium resources is gradually increasing, and there is an urgent need for new technologies that can achieve fast and low-cost lithium extraction. Therefore, driven by market demand, front-end lithium extraction is the inevitable trend of lithium extraction from salt lakes.

[0003] The most studied lithium adsorbent is inorganic adsorbent material, which can be divided into two categories: aluminum salt adsorbent and ion sieve type adsorbent. Ion sieve type adsorbent can be further divided into manganese ion sieve type and titanium ion sieve type. Among them, manganese ion sieve has the advantages of fast adsorption rate, high adsorption capacity and good ion selectivity. However, studies have found that in the process of eluting lithium, Mn 3+ under the action of H + , disproportionation reaction and John-Teller effect occur, resulting in dissolution of the ion sieve framework, and the defect of poor stability seriously hinders the application of manganese ion sieve. Titanium ion sieve has gradually attracted attention in recent years, and the main titanium ion sieve of concern is H2TiO3 type with a layered structure and H4TiSO 12 type with a spinel structure. Among them, the adsorption capacity and application range of H2TiO3 type ion sieve are higher than those of aluminum salt adsorbent, and the stability is better than that of manganese type, which is the second lithium adsorbent after aluminum salt adsorbent to be put into commercial application. However, it is found in actual application that the lithium adsorption capacity of H2TiO3 type ion sieve is difficult to reach the theoretical value, and the performance decreases with the increase of the number of cycles in the adsorption and desorption process. In summary, manganese type has obvious manganese dissolution loss in acid elution process (affecting the service life and product purity), and titanium type has lower dissolution loss but slightly lower adsorption capacity. Therefore, how to prepare an ion sieve type adsorbent with high adsorption capacity and low dissolution rate has become a technical problem to be solved. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing silicon-doped titanium lithium ion sieve from waste titanium silicalite.

[0005] To achieve the above technical purposes, the technical scheme adopted by the present application is as follows: A method for preparing silicon-doped titanium lithium ion sieve from waste titanium silicalite, comprising the following steps: (1) Raw material pretreatment: The waste titanium silicate 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°C 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 NaOH solution in a sealed container for reaction, stirred at 100-200°C for 4-24 hours, filtered, the solid is washed and set aside, and the filtrate is recovered and treated; (3) Preparation of ion sieve: The solid obtained in step (2), lithium source, and ethanol are mixed, mechanically ground or ball-milled thoroughly, and the mixture is transferred to a muffle furnace and calcined at 600-900°C for 3-8 hours to obtain a silicon-doped titanium lithium ion sieve; (4) Pickling and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in a pickling solution for pickling, solid-liquid separation, washing, and drying to obtain a silicon-doped titanium lithium ion sieve.

[0006] 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.

[0007] Preferably, the Si / Ti molar ratio of the discarded titanium silicon molecular sieve in step (1) is 12-30:1.

[0008] Preferably, during the high temperature calcination in step (1), the temperature is 600° C. and the time is 6 hours.

[0009] Preferably, the concentration of the NaOH solution in step (2) is 2-10 mol / L.

[0010] Preferably, the mass ratio of the purified TS-1 to the NaOH solution in step (2) is 1:(10-30).

[0011] Preferably, the specific method for recovering the filtrate in step (2) is: the filtrate is evaporated and concentrated at 80-90° C., and the precipitate is the recovered industrial-grade sodium silicate by-product.

[0012] 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; during the mechanical grinding or ball milling, the solid-liquid ratio of the solvent ethanol used is 5:(1-3).

[0013] 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° C. for 4-12 hours.

[0014] The beneficial effects of the present invention are as follows: the present invention replaces titanium ore with waste titanium silicon molecular sieve (TS-1), significantly reducing the cost of raw materials. The silicon doping amount is regulated by alkali treatment, and nano-SiO2 is recovered, thus realizing high-value utilization of waste materials. The prepared silicon-doped titanium lithium ion sieve exhibits excellent lithium selective adsorption capacity and is + / Li + =100:1 solution, the lithium-sodium selectivity coefficient α(Li / Na)≥280, the adsorption capacity is as high as 38.2 mg / g, the saturation time is only 30 min, and the titanium dissolution rate during recycling is ≤0.05%, which can be recycled for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the XRD test result diagram of Example 1 of the present invention; Figure 2 TEM test result diagram of Example 1 of the present invention; Figure 3 The present invention embodiment 1 and comparative example 1 are Li + Adsorption curve diagram. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0017] Example 1 A method for preparing a silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve comprises the following steps: (1) Raw material pretreatment: 30 g of waste titanium silicate molecular sieve TS-1 (Si / Ti=20) was calcined at 600 °C for 6 hours to remove residual organic matter, and then treated with 450 mL of hydrochloric acid solution (0.1 mol / L) at 70 °C for 6 hours. After solid-liquid separation, purified TS-1 was obtained; (2) Alkali treatment: The purified TS-1 obtained in step (1) was mixed with 10 mol / L NaOH solution in a mass ratio of 1:20 in a sealed container for reaction, stirred at 150°C for 12 hours, filtered, and the solid was washed for later use. The filtrate was concentrated by evaporation, and the resulting precipitate was the industrial sodium silicate by-product; (3) Preparation of ion sieve: The solid obtained in step (2), 0.8 g of lithium carbonate, and 2 mL of ethanol were mixed and fully mechanically ground. The mixture was dried and transferred to a muffle furnace and calcined at 600°C for 8 hours to obtain a silicon-doped titanium lithium ion sieve; the atomic ratio of each material was Si:Li:Ti = 0.01:1:1.

[0018] (4) Acid washing activation: the silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in 20 mL of 0.4 mol / L hydrochloric acid solution, stirred at 40°C for 12 hours, then solid-liquid separation, washing, drying, to obtain the silicon-doped titanium lithium ion sieve.

[0019] Example 2 A method for preparing a silicon-doped titanium lithium ion sieve from waste titanium silicalite molecular sieve, comprising the following steps: (1) Raw material pretreatment: 30 g of waste titanium silicalite molecular sieve TS-1 (Si / Ti = 20) is calcined at 550°C for 6 hours to remove residual organic matter, then treated with 600 mL of 0.5 mol / L nitric acid solution at 90°C for 1 hour, and solid-liquid separation to obtain purified TS-1; (2) Alkali treatment: the purified TS-1 obtained in step (1) is mixed with 8 mol / L NaOH solution in a mass ratio of 1:20 in a sealed container, stirred and treated at 180°C for 16 hours, filtered, and the solid is washed and prepared for use. The filtrate is evaporated and concentrated, and the obtained precipitate is an industrial-grade sodium silicate byproduct; (3) Ion sieve preparation: the solid obtained in step (2), 1.5 g of lithium acetate, and 3 mL of ethanol are mixed and mechanically ground, and the mixture is dried and transferred to a muffle furnace, calcined at 900°C for 5 hours to obtain a silicon-doped titanium lithium ion sieve. The atomic ratio of each material is Si:Li:Ti = 0.1:2:1.

[0020] (4) Acid washing 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 washing treatment is carried out at 60°C for 4 hours, then solid-liquid separation, washing, drying, to obtain the silicon-doped titanium lithium ion sieve.

[0021] Example 3 A method for preparing a silicon-doped titanium lithium ion sieve from waste titanium silicalite molecular sieve, comprising the following steps: (1) Raw material pretreatment: 30 g of waste titanium silicalite molecular sieve TS-1 (Si / Ti = 15) is calcined at 600°C for 6 hours to remove residual organic matter, then treated with 900 mL of 0.3 mol / L sulfuric acid solution at 80°C for 4 hours, and solid-liquid separation to obtain purified TS-1; (2) Alkali treatment: the purified TS-1 obtained in step (1) is mixed with 6 mol / L NaOH solution in a mass ratio of 1:20 in a sealed container, stirred and treated at 150°C for 20 hours, filtered, and the solid is washed and prepared for use. The filtrate is concentrated at high temperature, and the obtained precipitate is an industrial sodium silicate byproduct; (3) Preparation of ion sieve: The solid obtained in step (2), 1.0 g of lithium carbonate, and 3 mL of ethanol were mixed and fully mechanically ground. The mixture was dried and transferred to a muffle furnace and calcined at 700°C for 6 hours to obtain a silicon-doped titanium lithium ion sieve; the atomic ratio of each material was Si:Li:Ti = 0.05:1:1.

[0022] (4) Acid washing and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) was immersed in 15 mL of 0.3 mol / L hydrochloric acid solution and acid washed at 50°C for 8 hours, followed by solid-liquid separation, washing, and drying to obtain the silicon-doped titanium lithium ion sieve.

[0023] Comparative Example 1 A method for preparing a titanium-based lithium ion sieve comprises the following steps: (1) Preparation of ion sieve: Weigh an appropriate amount of 1 g of lithium carbonate, 3.13 g of titanium hydroxide and 5 mL of ethanol, mix them, and grind them mechanically. After drying, transfer the obtained sample to a muffle furnace and calcine it at 600°C for 8 hours to obtain an undoped titanium ion sieve; the atomic ratio of the material is Li:Ti = 1:1.

[0024] (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°C for 12 hours, followed by solid-liquid separation, washing, and drying to obtain the titanium lithium ion sieve.

[0025] Performance Testing The samples obtained in Example 1 were taken for XRD and TEM tests, as shown in the following example: Figure 1 and Figure 2 shown.

[0026] Li + Adsorption performance test: 1L of laboratory-prepared brine was used to test the adsorption performance. The specific composition of the self-prepared brine is shown in Table 1 below.

[0027] Table 1 Main ingredients of homemade brine 5 g of titanium lithium ion sieve samples prepared in Example 1 and Comparative Example 1 were respectively immersed in 200 mL of laboratory prepared brine and stirred continuously. 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, when Li + When the content no longer changes, it is adsorption equilibrium. The adsorption rate curve is as follows Figure 3As shown, the sample in Example 1 reaches adsorption equilibrium when adsorbing for 30 min, and the equilibrium adsorption capacity is 38.2 mg / g; at the same time, the lithium-sodium selectivity coefficient α(Li / Na) is ≥280, which indicates that the silicon-doped titanium lithium ion sieve obtained by the present application has high lithium-sodium selectivity in salt lake brine. + The sample obtained by the present application has good selectivity and also has high adsorption capacity. The adsorption equilibrium of Comparative Example 1 is reached at about 90 min, and the maximum adsorption capacity is 21.9 mg / g, which is significantly lower than that of the sample obtained in Example 1.

[0028] Titanium dissolution loss: The sample after adsorption is desorbed, the desorption liquid is 0.4 mol / L hydrochloric acid solution, the volume V(L) of the acid washing liquid in the elution process is collected, the concentration C(mg / L) of titanium ions is tested, and then the titanium dissolution loss rate % = CV / m*100%, m is the mass of the adsorbent (g). The results are shown in Table 2.

[0029] Table 2: Test results of titanium dissolution loss rate The present application also studies the cyclic adsorption performance of the obtained silicon-doped titanium lithium ion sieve, and finds that the maximum adsorption capacity does not appear to be sharply attenuated after 500 cycles, which indicates that the product of the present application has good cycle performance.

[0030] It should be noted that the above examples are only part of the preferred modes of implementing the present application, but not all. Obviously, based on the above examples of the present application, all other examples obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

Claims

1. A method for preparing silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve, characterized in that: It includes the following steps: (1) Raw material pretreatment: The waste titanium silicate 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°C 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 concentrated NaOH solution in a sealed container for reaction, stirred at 100-200°C for 4-24 hours, filtered, the solid is washed and set aside, and the filtrate is recovered and treated; (3) Preparation of ion sieve: The solid obtained in step (2), lithium source, and ethanol are mixed, mechanically ground or ball-milled thoroughly, and the mixture is transferred to a muffle furnace and calcined at 600-900°C for 3-8 hours to obtain a silicon-doped titanium lithium ion sieve; (4) Pickling and activation: The silicon-doped titanium lithium ion sieve obtained in step (3) is immersed in a pickling solution for pickling, solid-liquid separation, washing, and drying to obtain a silicon-doped titanium lithium ion sieve.

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

1.

4. The method for preparing silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve according to claim 1, characterized in that: During the high temperature calcination in step (1), the temperature is 500-700°C and the time is 4-8 hours.

5. The method for preparing silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve according to claim 1, characterized in that: The concentration of the NaOH solution in step (2) is 2-10 mol / L.

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

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

8. The method for preparing silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve according to claim 1, characterized in that: In the 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 the mechanical grinding or ball milling, the solid-liquid ratio of the solvent ethanol used is 5:(1-3).

9. The method for preparing silicon-doped titanium-based lithium ion sieve from waste titanium silicon molecular sieve according to claim 1, characterized in that: 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° C. for 4-12 hours.

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