1. A process for continuously preparing an FAU-LTA eutectic molecular sieve comprises the following specific steps: mixing the pretreated lithium slag and the molecular sieve mother liquor prepared from the treated lithium slag in a solid-liquid ratio of 1 (1-20) g/ml; introducing the mixed material into an ultrasonic coil reactor in an ultrasonic water bath for continuous ultrasonic treatment at the ultrasonic frequency of 30-130 KHz and the ultrasonic water bath temperature of 20-80 ℃ by using a peristaltic pump at the flow rate of 1-20 mL/min, wherein the material stays in the ultrasonic coil reactor for 200-0.1 min; introducing the material subjected to ultrasonic treatment into a coil reactor arranged in a microwave reactor at a flow rate of 1-10 mL/min by using a peristaltic pump for crystallization synthesis, wherein the microwave output power is 0.1-1.5 KW, the microwave temperature is kept at 70-150 ℃, and the material stays in the microwave coil reactor for 200-0.1 min; and filtering, washing and drying the crystallized product to obtain the FAU-LTA eutectic molecular sieve.

2. The process of claim 1, wherein the lithium slag-prepared molecular sieve mother liquor comprises the following components: the concentration of the sodium-containing alkaline compound is 0.1-5 mol/L, the silicon content is 5-20 g/L, and the aluminum content is 0.1-2 g/L; wherein the sodium-containing alkaline compound is one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

3. The process of claim 1, wherein the preparation of the molecular sieve from the lithium slag comprises the steps of sieving the raw material lithium slag by a sieve of 60-200 meshes, removing large particles, washing the lithium slag with water until the pH of the washing filtrate is 5-7, and heating to 60-160 ℃ for 0.5-12 h for dehydration.

4. The process according to claim 3, wherein the raw material lithium slag comprises the following components in percentage by mass: SiO 2₂:30～80％、Al₂O₃:15～65％、Fe₂O₃0 to 1% and 0 to 5% of other impurities.

5. The process according to claim 1, wherein the treatment of the lithium slag to prepare the molecular sieve mother liquor is to adjust the concentration of the sodium-containing basic compound in the lithium slag to prepare the molecular sieve mother liquor with the sodium-containing basic compound; wherein the concentration of the sodium-containing alkaline compound in the molecular sieve mother liquor prepared from the adjusted lithium slag is 1-10 mol/L; the sodium-containing alkaline compound for adjustment is one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

6. The process of claim 1 wherein the ultrasonic coil means and the microwave coil means are each made of one of fusible Polytetrafluoroethylene (PFA) or Polytetrafluoroethylene (PTFE).

7. The process of claim 1, wherein the crystallized product is washed with water until the molecular sieve product has a pH of 8-10, and dried at 60-150 ℃ for 1-24 hours.

Background

The lithium slag is solid waste generated in the process of producing lithium carbonate by a spodumene sulfuric acid method, and the main components of the lithium slag are oxides such as silicon, aluminum and the like. At present, nearly ten tons of lithium slag are generated when one ton of lithium carbonate products are produced by taking spodumene as a raw material through a sulfuric acid method at home, and a large amount of lithium slag is usually treated by adopting a landfill or open-air stacking method, so that the method not only occupies a field, but also can run off along with wind and rain, and pollutes the environment. China has a huge amount of lithium slag which is in urgent need of treatment, development and utilization every year. How to effectively utilize the waste lithium slag and turn waste into wealth, economic and social benefits are created for enterprises, and the method becomes a major problem which is urgently needed to be solved by related production enterprises. At present, lithium slag is mainly applied to relevant fields of building materials at home and abroad, for example, the lithium slag is doped into a proper amount in a paper of 'test research on the bonding property of lithium slag-doped recycled concrete and reinforcing steel bars' published in 2020 by Qin & Chamber and the like, so that the bonding property between the concrete and the reinforcing steel bars can be improved.

The zeolite molecular sieve as the detergent auxiliary agent can effectively replace phosphorus-containing washing powder and effectively relieve the harm of the phosphorus-containing washing powder to the environment, and the zeolite molecular sieve as the detergent auxiliary agent is produced on a large scale in many countries. The zeolite molecular sieve still contains a certain amount of silicon and aluminum components and part of unreacted alkali in the mother liquor after the preparation, and because the mother liquor of the molecular sieve has the reasons of large scale, strong alkalinity of the solution, easy colloid formation and the like, how to effectively treat and prepare the mother liquor of the molecular sieve becomes a great problem which needs to be solved urgently.

Lin et al synthesized and synthesized FAU/LTA eutectic molecular sieve by hydrothermal Synthesis and adsorption property of zeolite FAU/LTA from lithium slag with digestion of heat liquid, which was published in "Chinese Journal of chemical Engineering" 2015, using lithium slag to prepare a mother solution of molecular sieve, and crystallizing the mother solution in a reaction kettle for 9 hours. Yoldi et al, in Zeolite synthesis from aluminum salt slurry wall published in Powder Technology 2020, used Zeolite synthesis mother liquor instead of fresh alkali liquor to perform Zeolite synthesis, and crystallized in a reaction kettle for 6 hours to obtain NaX Zeolite. CN103253681B authorizes a method for preparing Na-A/X or Na-A/X/P cocrystallized molecular sieve by hydrothermal synthesis of lithium slag, and adopts a hydrothermal method to synthesize the cocrystallized molecular sieve, which is an intermittent kettle type reaction and does not recycle the mother liquor after synthesis.

The traditional molecular sieve preparation process adopts an intermittent kettle type reaction, has the defects of long reaction time, discontinuous operation process and the like, and does not effectively recycle the mother liquor, thereby causing the waste of resources.

Disclosure of Invention

The invention provides a process for continuously preparing an FAU/LTA eutectic molecular sieve by using lithium slag to prepare a molecular sieve mother liquor and using ultrasonic-microwave to continuously prepare the FAU/LTA eutectic molecular sieve by using the mother liquor prepared from lithium slag as a raw material aiming at the defects that the mother liquor for preparing the molecular sieve is not effectively utilized and the conventional synthesis of the FAU/LTA eutectic molecular sieve has long reaction time, discontinuous reaction process and the like.

The technical scheme of the invention is as follows: a process for continuously preparing an FAU/LTA eutectic molecular sieve comprises the following specific steps: mixing the pretreated lithium slag and the treated lithium slag (after the concentration of the sodium-containing alkaline compound is adjusted) to prepare a molecular sieve mother solution, wherein the solid-to-liquid ratio of the molecular sieve mother solution to the lithium slag is 1 (1-20) g/ml; introducing the mixed material into an ultrasonic coil reactor in an ultrasonic water bath for continuous ultrasonic treatment at the ultrasonic frequency of 30-130 KHz and the ultrasonic water bath temperature of 20-80 ℃ by using a peristaltic pump at the flow rate of 1-20 mL/min, wherein the material stays in the ultrasonic coil reactor for 200-0.1 min; introducing the material subjected to ultrasonic treatment into a coil reactor arranged in a microwave reactor at a flow rate of 1-10 mL/min by using a peristaltic pump for crystallization synthesis, wherein the microwave output power is 0.1-1.5 KW, the microwave temperature is kept at 70-150 ℃ by adopting air cooling or liquid cooling, and the material stays in the microwave coil reactor for 200-0.1 min; filtering, washing and drying the crystallized product to obtain the FAU/LTA eutectic molecular sieve; collecting mother liquor, and continuously recycling the mother liquor according to the process to prepare the FAU/LTA eutectic molecular sieve.

Preferably, the mother liquor for preparing the molecular sieve from the lithium slag comprises the following components: the concentration of the sodium-containing alkaline compound is 0.1-5 mol/L, the silicon content is 5-20 g/L, and the aluminum content is 0.1-2 g/L; wherein the sodium-containing alkaline compound is one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

Preferably, the preparation of the molecular sieve from the lithium slag comprises the steps of sieving the raw material lithium slag by 60-200 meshes, removing large particles, washing the lithium slag by water until the pH value of a washing filtrate is 5-7, and then heating to 60-160 ℃ for 0.5-12 h for dehydration.

Preferably, the raw material lithium slag comprises the following components in percentage by mass: SiO 2₂:30～80％、Al₂O₃:15～65％、Fe₂O₃0 to 1% and 0 to 5% of other impurities.

The treatment of preparing the molecular sieve mother liquor from the lithium slag comprises the steps of adjusting the concentration of a sodium-containing alkaline compound in the molecular sieve mother liquor prepared from the lithium slag by using the sodium-containing alkaline compound; wherein the concentration of the sodium-containing alkaline compound in the molecular sieve mother liquor prepared from the adjusted lithium slag is 1-10 mol/L; the sodium-containing alkaline compound for adjustment is one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

Preferably, the ultrasonic coil device and the microwave coil device are both made of one of fusible Polytetrafluoroethylene (PFA) or Polytetrafluoroethylene (PTFE).

And washing the crystallized product with water until the pH value of the molecular sieve product is 8-10, and drying at 60-150 ℃ for 1-24 h.

The first mother liquor recycling is a process for preparing the eutectic molecular sieve after fresh mother liquor is treated, and the mother liquor used in the subsequent preparation process is the mother liquor filtered in the previous preparation process. And (4) treating the process mother liquor and then continuously recycling to prepare the FAU/LTA eutectic molecular sieve.

Has the advantages that:

the invention provides a process for continuously preparing an FAU/LTA eutectic molecular sieve by taking a molecular sieve mother solution prepared from lithium slag as a raw material and carrying out ultrasonic-microwave treatment. The process greatly shortens the production time, improves the production efficiency, effectively reduces the production cost by recycling the mother liquor, protects the environment, can be used as a detergent auxiliary agent, and has wide application prospect.

Drawings

FIG. 1 is a schematic flow chart of a device for continuously preparing an FAU/LTA eutectic molecular sieve by mother liquor recycling ultrasonic-microwave; wherein 1, a raw material storage tank; 2. a peristaltic pump; 3. carrying out ultrasonic water bath; 4. an ultrasonic coil reactor; 5. ultrasonic material storage tank; 6. a peristaltic pump; 7. a microwave reactor; 8. a microwave coil reactor; 9. a filtration device; 10. a mother liquor storage tank; 11. a pump;

FIG. 2 is an XRD contrast diagram of an FAU/LTA eutectic molecular sieve prepared continuously by using mother liquor from example 1 through ultrasound-microwave.

Detailed Description

The invention is further described below with reference to specific examples to facilitate the understanding of the invention, but the invention is not limited thereto. The flow diagram of the device for continuously preparing the FAU/LTA eutectic molecular sieve is shown in FIG. 1.

In each example, the phase of the synthesized FAU/LTA eutectic molecular sieve and the ratio of the FAU to LTA molecular sieves in the product were determined by X-ray diffraction. The calcium ion exchange capacity of the prepared FAU/LTA eutectic molecular sieve is measured by adopting a method for testing the calcium ion exchange capacity of the 4A molecular sieve for the detergent (QB/T1768) -2003), and the magnesium ion exchange capacity of the prepared FAU/LTA eutectic molecular sieve is measured by referring to the measurement method.

[ example 1 ]

Preparing a molecular sieve mother liquor (the concentration of NaOH in the mother liquor is 2.1mol/L, the silicon content is 14g/L, and the aluminum content is 1g/L) from the lithium slag, and adjusting the concentration of an alkaline compound containing sodium in the mother liquor to be 2.5mol/L by using NaOH. Mixing lithium slag (containing SiO)₂:69.32％，Al₂O₃26.45 percent, others: 4.23% with the main crystalline phase being leached spodumene), sieving with a 200 mesh sieve to remove a few large particles, pre-treating to pH 6, filtering, and drying at 120 ℃ for 2 h. Weighing 10g of pretreated lithium slag, adding 50mL of treated mother liquor according to the solid-to-liquid ratio of 1:5, and mixing. Will be provided withIntroducing the mixed material into an ultrasonic coil reactor at a flow rate of 2mL/min by a peristaltic pump, wherein the material of the ultrasonic coil reactor is PFA, the ultrasonic frequency is 100KHz, the ultrasonic water bath temperature is 50 ℃, and the material stays in the ultrasonic coil reactor for 50 min; and introducing the material subjected to ultrasonic treatment into a PFA coil reactor in the microwave reactor at the flow rate of 2mL/min through a peristaltic pump, outputting the microwave with the power of 1KW, keeping the microwave temperature at 95 ℃ by adopting air cooling, and keeping the material in the microwave coil reactor for 50 min. The collected material was filtered, washed with water to pH 9 and dried at 110 ℃ for 4 h. The product is obtained by continuous preparation for 100min by XRD (Smartlab of Japan science corporation)^TM9KW X-ray diffractometer), the specific XRD pattern is shown in figure 2.

As can be seen from FIG. 2, the main characteristic peak positions of FAU are 6.17 °, 10.04 °, 23.41 ° and 26.80 °, the main characteristic peak positions of LTA are 7.43 °, 16.62 ° 26.99 ° and 28.03 °, and the same as the main characteristic peak positions of the standard sample, it is shown that the FAU/LTA eutectic molecular sieve is prepared. The first mother liquor recycling sample contains 25 wt% of LTA type molecular sieve, 75 wt% of FAU type molecular sieve and Ca²⁺Exchange capacity reaches 308mg_CaCO3/g，Mg²⁺Exchange capacity reaches 181mg_MgCO3(ii)/g; continuously collecting mother liquor and recycling for the second time according to the process conditions, wherein the product is an FAU/LTA eutectic molecular sieve, the percentage of LTA type molecular sieve is 27 wt%, the percentage of FAU type molecular sieve is 73 wt%, and the percentage of Ca is²⁺Exchange capacity up to 312mg_CaCO3/g，Mg²⁺Exchange capacity reaches 180mg_MgCO3/g。

[ example 2 ]

Preparing molecular sieve mother liquor (Na in the mother liquor) from lithium slag₂CO₃Concentration 4.6mol/L, silicon content 19.8g/L, aluminum content 0.1g/L), Na was used₂CO₃The concentration of the sodium-containing alkaline compound in the mother liquor is adjusted to 10 mol/L. Mixing lithium slag (containing SiO)₂:67.69％，Al₂O₃:28.75％，Fe₂O₃0.47%, others: 3.09% with main crystalline phase being leached spodumene), sieving with a 60 mesh sieve to remove a few large particles, pretreating to pH 5, filtering, and drying at 160 deg.C for 0.5 h. Weighing 10g of pretreated lithium slag, and mixing10mL of the treated mother liquor was added at a solid-to-liquid ratio of 1:1 and mixed. Introducing the mixed material into an ultrasonic coil reactor at a flow rate of 20mL/min by a peristaltic pump, wherein the ultrasonic coil reactor is made of PTFE, the ultrasonic frequency is 130KHz, the ultrasonic water bath temperature is 80 ℃, and the retention time of the material in the ultrasonic coil reactor is 0.1 min; and introducing the material subjected to ultrasonic treatment into a PTFE coil reactor in a microwave reactor at a flow rate of 1mL/min by a peristaltic pump, wherein the microwave output power is 0.1KW, cooling by adopting liquid with a cooling medium of liquid paraffin, keeping the temperature of the microwave at 70 ℃, and keeping the material in the microwave coil reactor for 200 min. The collected material was filtered, washed with water to pH 8 and dried at 60 ℃ for 24 h. The product of the first mother liquor recycling can be obtained by adopting a continuous preparation process for 200.1min, and the product is analyzed by XRD to be FAU/LTA eutectic molecular sieve, wherein the percentage of LTA type molecular sieve is 8 wt%, the percentage of FAU type molecular sieve is 92 wt%, and the percentage of Ca is²⁺Exchange capacity reaches 295mg_CaCO3/g，Mg²⁺The exchange capacity reaches 198mg_MgCO3(ii)/g; continuously collecting mother liquor and recycling for the second time according to the process conditions, wherein the product is an FAU/LTA eutectic molecular sieve, the percentage of LTA type molecular sieve is 7 wt%, the percentage of FAU type molecular sieve is 93 wt%, and the percentage of Ca is²⁺Exchange capacity reaches 295mg_CaCO3/g，Mg²⁺Exchange capacity reaches 200mg_MgCO3/g。

[ example 3 ]

Preparing a molecular sieve mother liquor (NaHCO in the mother liquor) from lithium slag₃Concentration 0.1mol/L, silicon content 5.1g/L, aluminum content 2g/L), NaHCO is used₃The concentration of the sodium-containing alkaline compound in the mother liquor is adjusted to be 1 mol/L. Mixing lithium slag (containing SiO)₂:66.52％，Al₂O₃:32.83％，Fe₂O₃0.65% with the main crystalline phase being leached spodumene), sieving with a 200 mesh sieve to remove a few large particles, pretreating to pH 7, filtering, and drying at 60 deg.C for 12 h. Weighing 10g of pretreated lithium slag, adding 200mL of treated mother liquor according to the solid-to-liquid ratio of 1:20, and mixing. Introducing the mixed materials into an ultrasonic coil reactor at a flow rate of 1mL/min through a peristaltic pump, wherein the material of the ultrasonic coil reactor is PFA, the ultrasonic frequency is 30KHz, the ultrasonic water bath temperature is 20 ℃, and the materials stay in the ultrasonic coil reactor for 200 min; material creeping after ultrasonic treatmentThe pump is introduced into a PFA coil reactor in the microwave reactor at the flow rate of 10mL/min, the microwave output power is 1.5KW, the liquid cooling with the cooling medium as vegetable oil is adopted to keep the microwave temperature at 150 ℃, and the material stays in the microwave coil reactor for 0.1 min. The collected product was filtered, washed with water to pH 10 and dried at 150 ℃ for 1 h. The product of the first mother liquor recycling can be obtained by adopting a continuous preparation process for 200.1min, and the product is analyzed by XRD to be FAU/LTA eutectic molecular sieve, wherein the content of LTA type molecular sieve is 15 wt%, the content of FAU type molecular sieve is 85 wt%, and the content of Ca is²⁺Exchange capacity reaches 298mg_CaCO3/g，Mg²⁺The exchange capacity reaches 191mg_MgCO3(ii)/g; continuously collecting mother liquor and recycling for the second time according to the process conditions, wherein the product is an FAU/LTA eutectic molecular sieve, the percentage of LTA type molecular sieve is 17 wt%, the percentage of FAU type molecular sieve is 83 wt%, and the percentage of Ca is²⁺Exchange capacity up to 299mg_CaCO3/g，Mg²⁺The exchange capacity reaches 189mg_MgCO3/g。

[ example 4 ]

Preparing a molecular sieve mother liquor (the concentration of NaOH in the mother liquor is 1.9mol/L, the silicon content is 15.1g/L, and the aluminum content is 0.7g/L) from the lithium slag, and adjusting the concentration of an alkaline compound containing sodium in the mother liquor to be 2.5mol/L by using NaOH. Mixing lithium slag (containing SiO)₂:79.65％，Al₂O₃:15.87％，Fe₂O₃0.54%, others: 3.94% with the main crystalline phase being leached spodumene), sieving with a 200 mesh sieve to remove a few large particles, pre-treating to pH 6, filtering, and drying at 120 ℃ for 2 h. Weighing 10g of pretreated lithium slag, adding 60mL of treated mother liquor according to the solid-to-liquid ratio of 1:6, and mixing. Introducing the mixed material into an ultrasonic coil reactor at a flow rate of 2mL/min by a peristaltic pump, wherein the ultrasonic coil reactor is made of PTFE, the ultrasonic frequency is 100KHz, the ultrasonic water bath temperature is 55 ℃, and the material stays in the ultrasonic coil reactor for 50 min; and introducing the aged material into a PFA coil reactor in a microwave reactor at the flow rate of 2mL/min through a peristaltic pump, wherein the microwave output power is 1.1KW, the microwave temperature is kept at 95 ℃ by adopting air cooling, and the retention time of the material in the microwave coil reactor is 50 min. The collected product was filtered, washed with water to pH 9 and dried at 120 ℃ for 2 h. Adopting continuous preparation process for 100minThe product of the first mother liquor recycling can be obtained, and is analyzed by XRD to be FAU/LTA eutectic molecular sieve, wherein the percentage of LTA type molecular sieve is 37 wt%, the percentage of FAU type molecular sieve is 63 wt%, and the percentage of Ca is²⁺Exchange capacity up to 318mg_CaCO3/g，Mg²⁺The exchange capacity reaches 175mg_MgCO3(ii)/g; continuously collecting mother liquor and recycling for the second time according to the process conditions, wherein the product is an FAU/LTA eutectic molecular sieve, the percentage of LTA type molecular sieve is 35 wt%, the percentage of FAU type molecular sieve is 65 wt%, and the percentage of Ca is²⁺Exchange capacity up to 315mg_CaCO3/g，Mg²⁺The exchange capacity reaches 174mg_MgCO3/g。

[ example 5 ]

Preparing a molecular sieve mother liquor (the concentration of NaOH in the mother liquor is 2.1mol/L, the silicon content is 14.1g/L, and the aluminum content is 0.6g/L) from the lithium slag, and adjusting the concentration of an alkaline compound containing sodium in the mother liquor to be 2.5mol/L by using NaOH. Mixing lithium slag (containing SiO)₂:30.76％，Al₂O₃:64.15％，Fe₂O₃0.85 percent, and the others: 4.24% with the main crystalline phase being leached spodumene), sieving with a 200 mesh sieve to remove a few large particles, pre-treating to pH 6, filtering, and drying at 120 ℃ for 2 h. Weighing 10g of pretreated lithium slag, adding 50mL of treated mother liquor according to the solid-to-liquid ratio of 1:5, and mixing. Introducing the mixed materials into an ultrasonic coil reactor at a flow rate of 2mL/min through a peristaltic pump, wherein the material of the ultrasonic coil reactor is PFA, the ultrasonic frequency is 100KHz, the ultrasonic water bath temperature is 50 ℃, and the materials stay in the ultrasonic coil reactor for 50 min; and introducing the aged material into a PFA coil reactor in a microwave reactor at a flow rate of 2mL/min through a peristaltic pump, wherein the microwave output power is 0.9KW, the microwave temperature is kept at 95 ℃ by adopting air cooling, and the retention time of the material in the microwave coil reactor is 50 min. The collected product was filtered, washed with water to pH 9 and dried at 120 ℃ for 2 h. The product can be obtained by adopting a continuous preparation process for 100min, and is analyzed by XRD to be FAU/LTA eutectic molecular sieve, wherein the percentage of LTA type molecular sieve is 37 wt%, the percentage of FAU type molecular sieve is 63 wt%, and the percentage of Ca is²⁺Exchange capacity up to 318mg_CaCO3/g，Mg²⁺The exchange capacity reaches 175mg_MgCO3(ii)/g; continuously collecting mother liquor to carry out secondary recycling according to the process conditions, wherein the product is FAU/LTA eutectic crystal35 wt% of molecular sieve LTA type molecular sieve, 65 wt% of molecular sieve FAU type molecular sieve and Ca²⁺Exchange capacity up to 315mg_CaCO3/g，Mg²⁺The exchange capacity reaches 174mg_MgCO3/g。

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.