A method of treating suspended and acid insoluble material in a lithium bicarbonate solution

Abstract

This invention discloses a method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solutions, belonging to the field of lithium bicarbonate solution production technology. It includes a diatomaceous earth pre-coating filter aid process and a ceramic membrane cross-flow filtration process. The diatomaceous earth pre-coating filter aid process is arranged at the rear end of the carbonization coarse liquid tank and the front end of the ceramic membrane cross-flow filtration process, or at the rear end of the ceramic membrane cross-flow filtration process and the front end of the filter press. The ceramic membrane cross-flow filtration process uses a multi-channel tubular ceramic membrane with a pore size of 0.1 μm, intercepting fine suspended solids such as calcium carbonate, magnesium carbonate, and zinc carbonate, as well as acid-insoluble solid particles in the lithium bicarbonate solution through cross-flow feeding. This invention uses diatomaceous earth pre-coating filter aid combined with ceramic membrane cross-flow filtration to extend the filter press cleaning cycle, reduce filter cloth wear and maintenance costs; it can deeply remove fine suspended solids and impurities such as calcium, magnesium, zinc, and COD, without introducing organic matter and avoiding carbon black formation in the finished product; the process is automated, flexible in layout, and has a high lithium recovery rate, adaptable to the modification of various lithium extraction production lines.

Description

Technical Field

[0001] This invention belongs to the field of lithium bicarbonate solution production technology, and particularly relates to a method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solutions. Background Technology

[0002] Lithium extraction processes are mainly divided into two categories: lithium extraction from salt lakes and lithium extraction from lithium ore. In industrial production, the carbonation-pyrolysis process is commonly used to prepare lithium carbonate products. During the carbonation purification process of crude lithium carbonate, metallic impurity ions such as calcium, magnesium, and zinc carried in the raw material system react with the carbon dioxide introduced during carbonation, generating fine solid suspensions such as calcium carbonate, magnesium carbonate, and zinc carbonate, as well as acid-insoluble substances. These fine particulate impurities are mixed in the lithium bicarbonate solution, and if they cannot be effectively removed, they will directly reduce the purity of the final lithium carbonate product.

[0003] Existing conventional industrial purification solutions mainly involve a two-stage filtration process: first, a filter press is used to initially intercept the solid-liquid mixture of crude lithium bicarbonate, followed by a precision filter to deeply filter fine particulate matter. However, there are significant drawbacks in actual production: the suspended solids and acid-insoluble solid particles generated by carbonization are extremely fine, easily embedding and clogging the pores of the filter press cloth, leading to a series of production problems: ① After the filter cloth is clogged, the material flow rate decreases significantly, reducing production efficiency; ② The filter cloth cleaning cycle is greatly shortened, typically requiring shutdown for cleaning only 1-2 days; ③ The filter cloth wear rate accelerates, significantly increasing the replacement frequency; ④ Frequent shutdowns for cleaning and replacing filter cloth continuously consume a large amount of manpower, water, electricity, and filter cloth consumables, significantly increasing production and maintenance costs.

[0004] Other auxiliary purification methods exist in the industry, but they all have inherent shortcomings: ① Adding organic flocculants to aid filtration: Organic flocculants will introduce organic impurities into the lithium bicarbonate solution. In the subsequent high-temperature drying process of lithium carbonate, the organic matter decomposes under heat to generate carbon black, which adheres to the lithium carbonate powder, seriously contaminating the finished product and reducing the product grade. ② Activated carbon adsorption for impurity removal: Activated carbon has limited ability to intercept fine suspended solids, has a fast adsorption saturation rate, a short replacement cycle, and high costs for purchasing activated carbon and disposing of hazardous waste, making it uneconomical. ③ Single filter press filtration: Relying solely on the physical interception of filter cloth cannot effectively separate micron-sized fine suspended matter, resulting in a high content of suspended matter in the filtrate, which cannot meet the requirements for high-purity lithium carbonate production, and cannot simultaneously remove some calcium, magnesium, zinc, chloride ions and COD impurities.

[0005] In summary, existing lithium bicarbonate solution purification processes struggle to balance filtration efficiency, product purity, and production operating costs. There is an urgent need to develop a highly automated treatment process that can efficiently remove fine suspended solids and acid-insoluble matter, while extending the maintenance cycle of filtration equipment, preventing the introduction of organic impurities, and achieving a high degree of automation. To this end, we propose a method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solutions. Summary of the Invention

[0006] To address the aforementioned issues and the shortcomings of existing filter presses, such as easy clogging, frequent cleaning and replacement, organic reagent contamination of finished products, insufficient removal capacity of ultrafine suspended solids, and single impurity removal, this invention provides a combined treatment method of diatomaceous earth pre-coated filter aid and multi-channel tubular ceramic membrane cross-flow filtration. This method achieves the technical goals of long-term protection of filter press equipment, deep removal of micro-suspended solids and acid-insoluble substances, simultaneous removal of calcium, magnesium, zinc, chlorine, and COD, no introduction of organic impurities, and automated continuous production.

[0007] To achieve the above objectives, this invention proposes a method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution, comprising a diatomaceous earth pre-coating filter aid process and a ceramic membrane cross-flow filtration process; the diatomaceous earth pre-coating filter aid process is arranged at the rear end of the carbonization coarse liquid tank and the front end of the ceramic membrane cross-flow filtration process, or at the rear end of the ceramic membrane cross-flow filtration process and the front end of the filter press; the ceramic membrane cross-flow filtration process uses a multi-channel tubular ceramic membrane with a pore size of 0.1 μm, which intercepts fine suspended solids such as calcium carbonate, magnesium carbonate, and zinc carbonate and acid-insoluble solid particles in the lithium bicarbonate solution through cross-flow feeding.

[0008] Preferably, the diatomaceous earth pre-coating filter aid process includes the following steps: S1. Prepare a diatomaceous earth suspension pre-coating solution by mixing diatomaceous earth with a small amount of lithium bicarbonate solution. The porosity of the diatomaceous earth is 80% to 90%. S2. The pre-coating liquid is transported to the material tank and pumped into the filter press for circulation. Diatomaceous earth is uniformly formed on the surface of the filter cloth of the filter press to form a dense filter aid membrane layer. S3. Continuously circulate the pre-coating liquid until the filter press effluent is clear and transparent, thus completing the preparation of the filter cloth pre-coating membrane layer. Then, introduce the lithium bicarbonate raw solution to be treated for filtration.

[0009] Preferably, the cleaning and maintenance cycle of the filter press after diatomaceous earth pre-coating is extended from 1-2 days to 7 days, the frequency of clogging caused by the filter cloth directly intercepting fine suspended matter and particles is significantly reduced, and the flow rate of the feed liquid per unit time is increased.

[0010] Preferably, the specific steps of the ceramic membrane cross-flow filtration process are as follows: T1. Carbonized crude lithium bicarbonate solution containing suspended solids is transported to a multi-channel tubular ceramic membrane system. T2. The feed liquid flows through the ceramic membrane support and membrane layer in a cross-flow manner, and the liquid filtrate penetrates the micropores of the ceramic membrane and enters the filtrate tank for collection. T3, calcium carbonate, magnesium carbonate, zinc carbonate suspensions and acid-insoluble matter are retained inside the ceramic membrane channel, and the retained concentrate is circulated back or periodically discharged; T4. Periodically perform pure water backwashing and acid washing regeneration operations on the ceramic membrane to restore the filtration flux of the ceramic membrane.

[0011] Preferably, the filtration concentration-to-product ratio of the ceramic membrane system is not less than 95%; when the suspended solids content in the influent is several hundred mg / L, the suspended solids content in the ceramic membrane permeate is stably reduced to below 10 mg / L.

[0012] Preferably, the multi-channel tubular ceramic membrane is composed of a support and a surface filter membrane, with the surface membrane having a pore size of 0.1 μm and a multi-layer gradient membrane structure for layered interception of solid impurities of different particle sizes.

[0013] Preferably, the diatomaceous earth filter aid does not contain any organic flocculants, and no organic impurities are introduced throughout the process, thus avoiding the generation of carbon black that contaminates the finished product during the high-temperature drying process of lithium carbonate; it also eliminates the need for activated carbon adsorption, reducing the cost of consumable replacement and operating expenses.

[0014] Preferably, the ceramic membrane filtration simultaneously removes Ca, Mg, Zn metal impurity ions, Cl⁻ chloride ions, and COD organic impurities from the lithium bicarbonate solution; under the condition that the raw water Ca content is 49.69ppm and suspended solids are 284mg / L, the product water Ca is reduced to 12.89ppm and suspended solids are ≤2mg / L.

[0015] Preferably, the entire processing technology is automated: the ceramic membrane system integrates automatic feeding, automatic backwashing, and automatic acid washing and regeneration control units; the diatomaceous earth pre-coating process only requires a single cycle to form a film, followed by continuous feeding and filtration, with minimal manual intervention throughout the process, reducing manpower and maintenance costs.

[0016] The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution proposed in this invention can bring the following beneficial effects: 1. This invention relies on a porous diatomaceous earth protective membrane to isolate ultrafine particles from embedding in the filter cloth. Industrial testing shows that the cleaning cycle of the filter press is extended from 1-2 days to 7 days, and the service life of the filter cloth is increased by 4 times. The hourly throughput of the feed liquid is increased by 70%, and no new filter press equipment is needed for the same production capacity, saving fixed asset investment. The frequency of weekly shutdown for cleaning is greatly reduced. A single 10,000-ton-per-year lithium carbonate production line can reduce downtime losses by 200 hours per year, increasing finished product output. The purchase price of diatomaceous earth is low. Compared with activated carbon adsorption solutions, the annual consumable and hazardous waste disposal costs are reduced by more than 80%.

[0017] 2. This invention introduces no organic impurities, ensuring the quality of battery-grade lithium carbonate. The entire process eliminates organic flocculants such as polyacrylamide, preventing the dissolution and dispersion of high-molecular-weight organic matter in the lithium bicarbonate solution. This completely eliminates the carbonization of organic matter during the pyrolysis and drying stage, resulting in carbon black formation. The whiteness of the lithium carbonate powder consistently meets battery-grade standards. Compared to activated carbon adsorption processes, this invention avoids the problem of secondary pollution caused by activated carbon powder shedding. The ceramic membrane simultaneously removes calcium, magnesium, and zinc heavy metal impurities, resulting in a finished lithium carbonate product with metal impurity content far below national standard limits, allowing for direct supply to power battery cathode material manufacturers.

[0018] 3. The ceramic membrane of this invention deeply traps ultrafine suspended solids, and its impurity removal capability is significantly superior to that of traditional pressure filtration. This invention uses a 0.1μm gradient tubular ceramic membrane for cross-flow filtration, which can intercept 0.1-5μm fine crystals of calcium carbonate and zinc carbonate, as well as acid-insoluble matter, that cannot be separated by single pressure filtration. Multiple industrial tests have verified that within the range of 71-284 mg / L of suspended solids in the influent, the suspended solids in the ceramic membrane-treated water are stably controlled at 1-2 mg / L, while the suspended solids in the filtrate after single pressure filtration are as high as 90-135 mg / L. The concentration-to-product ratio of the ceramic membrane is stable at ≥95%, and lithium salts are recovered with the concentrate reflux, resulting in extremely low lithium material loss.

[0019] 4. This invention can simultaneously remove multiple impurities, simplifying the downstream purification process. The multi-layer gradient structure of the ceramic membrane, while retaining solid particles, synergistically removes soluble metal ions (Ca, Mg, Zn), chloride ions, and organic COD from the feed solution through adsorption on the membrane surface. Three sets of comparative data show a significant reduction in calcium, magnesium, zinc, and COD levels. The lithium bicarbonate solution treated by this process can eliminate the need for a secondary precision impurity removal process, shortening the entire production line process and reducing investment in supporting storage tanks and ion exchange equipment.

[0020] 5. This invention features a high degree of automation and integration, reducing the intensity of manual operation and maintenance. Diatomaceous earth can be used for long-term continuous operation after only a single pre-coating to form a film; the ceramic membrane system is equipped with a PLC automatic control unit, which automatically completes the entire process of feeding, cross-flow circulation, timed pure water backwashing, and online acid washing and regeneration, without the need for manual disassembly and rinsing of membrane elements; the entire filtration section only requires one operator for inspection, reducing the labor demand by 60% compared to traditional processes.

[0021] 6. The process layout of this invention is flexible and widely adaptable to both new and old production lines. The two filtration processes can be interchanged and connected in series. New production lines can use a diatomaceous earth pre-filter scheme to reduce the load on the ceramic membrane, while old production lines can use a ceramic membrane pre-filter scheme to reduce diatomaceous earth consumption. The retrofit process does not require the removal of the original filter press and storage tank equipment; only the addition of ceramic membrane modules and supporting automatic control pipelines is required. The retrofit cycle is short, the civil engineering investment is low, and it is suitable for various lithium extraction site conditions in salt lakes and lithium mines. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the multi-channel tubular ceramic membrane structure of the present invention.

[0023] Figure 2 This is a schematic diagram of the installation of the multi-channel tubular ceramic membrane of the present invention.

[0024] Figure 3 This is a schematic diagram of the multilayer structure of the tubular ceramic membrane of the present invention.

[0025] In the diagram: A represents the raw water entering the ceramic membrane, B represents the product water exiting the ceramic membrane, and C represents the product water after passing through the filter press. Detailed Implementation

[0026] To more clearly explain the overall concept of this invention, the following description is provided in conjunction with the appendix to the specification. Figure 1-3 Detailed explanations will be provided using examples.

[0027] This invention provides a method for treating suspended solids and acid-insoluble matter in a lithium bicarbonate solution, comprising a diatomaceous earth pre-coating filter aid step and a ceramic membrane cross-flow filtration step; the diatomaceous earth pre-coating filter aid step is arranged at the rear end of the carbonization coarse liquid tank and the front end of the ceramic membrane cross-flow filtration step, or at the rear end of the ceramic membrane cross-flow filtration step and the front end of the filter press; the ceramic membrane cross-flow filtration step uses a multi-channel tubular ceramic membrane, such as... Figure 1 , 3 As shown, the ceramic membrane has a pore size of 0.1 μm and intercepts fine suspended solids such as calcium carbonate, magnesium carbonate, and zinc carbonate, as well as acid-insoluble solid particles, in the lithium bicarbonate solution using a cross-flow feed method. The cross-flow installation structure of the multi-channel tubular ceramic membrane is as follows. Figure 2 As shown.

[0028] Example 1: Comparative Test of Diatomaceous Earth Pre-coated Filter Aid Used Alone Process steps: S1: Take the crude lithium bicarbonate solution after lithium extraction and carbonization in the salt lake, with suspended solids of 75 mg / L. Select diatomaceous earth with a porosity of 85%. Circulate the pre-coating solution in a closed loop for 2 hours until the effluent is clear, and then pass the original solution through for continuous filtration. S2: Preparation of pre-coating solution: Diatomaceous earth (porosity 85%) and a small amount of lithium bicarbonate solution are mixed to form a suspension; S3: Pre-coating circulation: Pump the suspension into the plate and frame filter press, and return the filtrate to the feed tank for continuous circulation until the effluent is completely clear; S4: Pass the crude liquid to be treated through continuous filtration and record the equipment operating parameters.

[0029] Experimental results: Control group without pre-coated diatomaceous earth: The filter cloth of the filter press was completely clogged after 1.5 days of operation, and the machine had to be stopped for cleaning. The daily filtrate processing capacity was 18m³. Diatomaceous earth pre-coated experimental group: Stable continuous operation for 7 days before cleaning is required, and the daily filtrate treatment capacity is increased to 32m³; The filtrate contained no new organic impurities, COD did not increase, and there was no risk of carbon black formation.

[0030] Supporting equipment: 50㎡ plate and frame filter press, 30m³ pre-coating mixing tank, variable frequency transfer pump, online turbidity detector; pre-coating mixing speed 120r / min, total pre-coating cycle time 2h, online turbidity value ≤5NTU as the effluent clarification criterion; monthly consumable comparison: the control group replaced 15 filter cloths per month, while the experimental group only replaced 2 filter cloths per month, reducing the monthly filter cloth cost by 87%.

[0031] Example 2: Ceramic membrane for individual depth filtration of low-impurity-load lithium bicarbonate solution (corresponding to samples A1 / B1) Operating parameters: transmembrane pressure difference 0.2MPa, crossflow velocity 3m / s, pure water backwash pressure 0.3MPa, pickling agent is 5% dilute nitric acid, soaking and regeneration time 30min.

[0032] Raw water quality (ceramic membrane raw water A1): Ca: 8.034 ppm, Mg: 1.073 ppm, Zn: 3.845 ppm, Cl⁻: 363.5 ppm, suspended solids: 71 mg / L, COD: 13.54 mg / L.

[0033] Process conditions: 0.1μm multi-channel tubular ceramic membrane is used, cross-flow filtration is performed, concentration ratio is 96%, and timed pure water backwashing + weekly acid washing regeneration is used.

[0034] Permeate parameters (ceramic membrane permeate B1): Ca: 1.274ppm, Mg: 0.903ppm, Zn: 3.790ppm, Cl⁻: 344.3ppm, suspended solids 2mg, COD 1.505mg / L.

[0035] Control group (filter press after-liquid C1 only): The suspended solids concentration was 90 mg / L, and calcium ions were not detected, but the retention effect of fine suspended solids was extremely poor, which could not meet the production standards for high-purity lithium carbonate.

[0036] Example 3: Ceramic membrane for treating lithium bicarbonate solution with medium to high suspended solids (corresponding to samples A2 / B2) Operating parameters: transmembrane pressure difference 0.2MPa, crossflow velocity 3m / s, pure water backwash pressure 0.3MPa, pickling agent is 5% dilute nitric acid, soaking and regeneration time 30min.

[0037] Raw water quality (ceramic membrane raw water A2): Ca: 25.73 ppm, Mg: 2.928 ppm, Zn: 2.541 ppm, Cl⁻: 448.08 ppm, suspended solids 122 mg / L, COD 33.11 mg / L.

[0038] Process conditions: Same as the ceramic membrane system parameters in Example 2.

[0039] Permeate parameters (ceramic membrane permeate B2): Ca: 5.034 ppm, Mg: 1.287 ppm, Zn: 2.205 ppm, Cl⁻: 151.10 ppm, suspended solids 1 mg / L, COD 37.62 mg / L.

[0040] Control group (filtration liquid C2): The suspended solids concentration was 135 mg / L, with high levels of magnesium and zinc impurities, and the filtrate clarity did not meet the standards.

[0041] Example 4: Ceramic membrane treatment of crude lithium bicarbonate solution with high suspended solids and high calcium impurities (corresponding to samples A3 / B3) Operating parameters: transmembrane pressure difference 0.2MPa, crossflow velocity 3m / s, pure water backwash pressure 0.3MPa, pickling agent is 5% dilute nitric acid, soaking and regeneration time 30min.

[0042] Raw water quality (ceramic membrane raw water A3): Ca: 49.69ppm, Mg: 3.893ppm, Zn: 10.55ppm, Cl⁻: 523.28ppm, suspended solids: 284mg / L, COD: 39.13mg / L.

[0043] Process conditions: cross-flow filtration with ceramic membrane, concentration ratio of 95.5%, and shortened backwashing interval to ensure stable flux.

[0044] Permeate parameters (ceramic membrane permeate B3): Ca: 12.89 ppm, Mg: 1.932 ppm, Zn: 4.906 ppm, Cl⁻: 284.42 ppm, suspended solids: 2 mg / L, COD: 25.58 mg / L Control group (filtration liquid C3): Suspended solids 107 mg / L, Ca 7.905 ppm, Mg 1.300 ppm, Zn 20.95 ppm, zinc impurity retention effect is far worse than ceramic membrane.

[0045] Example 5: Pre-coated diatomaceous earth pressure filter + ceramic membrane post-filtration combined process (preferred example) Process flow: Carbonized crude liquid tank → Diatomaceous earth pre-coated plate and frame filter press → Intermediate storage tank → 0.1μm tubular ceramic membrane system → Finished lithium bicarbonate clarified liquid tank Operating parameters: Diatomaceous earth has a porosity of 82%. Film formation is completed in 2 hours of pre-coating and circulation on a filter press, and the cleaning cycle is 7 days. The ceramic membrane has a concentration ratio of 95%, and features automatic pure water backwashing every 30 minutes and online acid washing every 72 hours. Overall processing effect: Front-end filter press pre-intercepts large suspended solids, significantly reducing the fouling rate of the downstream ceramic membrane and extending the acid washing and regeneration cycle of the ceramic membrane by 50%. Ultimately, the suspended solids in the permeate produced by the ceramic membrane were stabilized at ≤2mg / L, and the levels of Ca, Mg, Zn, chloride ions, and COD were significantly reduced simultaneously. The frequency of downtime maintenance for the entire production line was reduced by 70%, the consumption of filter cloth and ceramic membrane consumables was significantly reduced, no organic impurities were introduced, and the finished lithium carbonate product was free of carbon black defects.

[0046] Example 6: Ceramic membrane pre-filtration + diatomaceous earth pre-coated pressure filter followed by fine filtration process (modified and adapted example) Process flow: Carbonized crude liquid tank → Ceramic membrane pretreatment system → Intermediate tank → Diatomaceous earth pre-coated filter press → Clarified liquid tank Applicable scenarios: Upgrading of old factories where the existing production line filter press has insufficient processing capacity and large fluctuations in suspended solids concentration.

[0047] Implementation results: The ceramic membrane pre-removes more than 85% of ultrafine suspended solids, significantly reducing the suspended solids in the feed liquid entering the filter press and reducing the amount of diatomaceous earth used by 40%. The filter press operated stably, the 7-day cleaning cycle remained unchanged, and the final filtrate clarity was consistent with that of Example 5. The production line can be upgraded without dismantling the existing filter press equipment; only the addition of ceramic membrane units is required. The upgrade investment is low and the equipment is highly adaptable.

[0048] Comparative Example 1: Traditional organic flocculant + filter press process After adding polyacrylamide organic flocculant to the crude lithium bicarbonate solution and then pressing and filtering, the suspended solids in the filtrate can be reduced to about 60 mg / L, but the COD of the solution increases; subsequently, after high-temperature drying of lithium carbonate, black carbon black particles appear on the surface of the powder, the product grade decreases, and it cannot be used for the production of battery-grade lithium carbonate.

[0049] Comparative Example 2: Activated carbon adsorption + single-stage pressure filtration process After the crude liquid is adsorbed by the activated carbon column, it is filtered by pressure. The activated carbon can only adsorb a small amount of organic impurities, and the removal effect of suspended solids is poor. The suspended solids in the filtrate are still higher than 80 mg / L. The activated carbon needs to be completely replaced every 3 days. The cost of consumables procurement and hazardous waste disposal is more than 6 times that of the diatomaceous earth solution of this invention, which is extremely uneconomical.

[0050] Table 1 is a comparison of the suspended solids content of the ceramic membrane raw water, ceramic membrane permeate, and filter press filtrate in Examples 2-4.

[0051] Table 1 Comparison of filtration results between ceramic membrane and filter press

[0052] As can be seen from the data comparison in Table 1, the ceramic membrane equipment has a strong removal effect on suspended solids, reducing them from hundreds of mg / L to a few mg / L, and also has a certain removal effect on COD in oil. It also has a certain removal effect on impurity elements such as calcium, magnesium, zinc and chlorine, further ensuring the quality of the finished lithium carbonate product.

[0053] In summary, compared with filter presses, ceramic membranes have a strong removal effect on the main suspended solids, reducing filter press clogging and the need for frequent filter cloth replacement and cleaning. To a certain extent, they can also reduce impurity content and improve product quality.

[0054] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for treating suspended solids and acid-insoluble matter in a lithium bicarbonate solution, characterized in that, It includes a diatomaceous earth pre-coating filter aid process and a ceramic membrane cross-flow filtration process; the diatomaceous earth pre-coating filter aid process is arranged at the rear end of the carbonization coarse liquid tank and the front end of the ceramic membrane cross-flow filtration process, or at the rear end of the ceramic membrane cross-flow filtration process and the front end of the filter press; the ceramic membrane cross-flow filtration process adopts a multi-channel tubular ceramic membrane with a pore size of 0.1μm, which intercepts fine suspended solids and acid-insoluble solid particles such as calcium carbonate, magnesium carbonate, and zinc carbonate in the lithium bicarbonate solution by cross-flow feeding.

2. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The diatomaceous earth pre-coating filter aid process includes the following steps: S1. Prepare a diatomaceous earth suspension pre-coating solution by mixing diatomaceous earth with a small amount of lithium bicarbonate solution. The porosity of the diatomaceous earth is 80% to 90%. S2. The pre-coating liquid is transported to the material tank and pumped into the filter press for circulation. Diatomaceous earth is uniformly formed on the surface of the filter cloth of the filter press to form a dense filter aid membrane layer. S3. Continuously circulate the pre-coating liquid until the filter press effluent is clear and transparent, thus completing the preparation of the filter cloth pre-coating membrane layer. Then, introduce the lithium bicarbonate raw solution to be treated for filtration.

3. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 2, characterized in that, After being pre-coated with diatomaceous earth, the cleaning and maintenance cycle of the filter press is extended from 1-2 days to 7 days. The frequency of clogging caused by the filter cloth directly intercepting fine suspended solids and particles is significantly reduced, and the flow rate of the liquid per unit time is increased.

4. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The specific steps of the ceramic membrane cross-flow filtration process are as follows: T1. The carbonized crude lithium bicarbonate solution containing suspended solids is transported to a multi-channel tubular ceramic membrane system. T2. The feed liquid flows through the ceramic membrane support and membrane layer in a cross-flow manner, and the liquid filtrate penetrates the micropores of the ceramic membrane and enters the filtrate tank for collection. T3, calcium carbonate, magnesium carbonate, zinc carbonate suspensions and acid-insoluble matter are retained inside the ceramic membrane channel, and the retained concentrate is circulated back or periodically discharged; T4. Periodically perform pure water backwashing and acid washing regeneration operations on the ceramic membrane to restore the filtration flux of the ceramic membrane.

5. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 4, characterized in that, The ceramic membrane system has a filtration concentration ratio of no less than 95%; when the influent suspended solids content is several hundred mg / L, the suspended solids in the ceramic membrane permeate are stably reduced to below 10 mg / L.

6. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The multi-channel tubular ceramic membrane is composed of a support and a surface filter membrane. The surface membrane has a pore size of 0.1 μm and a multi-layer gradient membrane structure that intercepts solid impurities of different particle sizes in layers.

7. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The diatomaceous earth filter aid does not contain any organic flocculants, and no organic impurities are introduced throughout the process, avoiding the generation of carbon black that contaminates the finished product during the high-temperature drying process of lithium carbonate; it also eliminates the need for activated carbon adsorption, reducing the cost of consumable replacement and operating expenses.

8. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The ceramic membrane filtration simultaneously removes Ca, Mg, Zn metal impurity ions, Cl⁻ chloride ions, and COD organic impurities from the lithium bicarbonate solution; under the condition that the raw water Ca content is 49.69ppm and suspended solids are 284mg / L, the product water Ca is reduced to 12.89ppm and suspended solids are ≤2mg / L.

9. The method for treating suspended solids and acid-insoluble matter in lithium bicarbonate solution according to claim 1, characterized in that, The entire processing technology operates automatically: the ceramic membrane system integrates automatic feeding, automatic backwashing, and automatic acid washing and regeneration control units; the diatomaceous earth pre-coating process requires only a single cycle for membrane formation, followed by continuous feeding and filtration, minimizing manual intervention and reducing labor costs for operation and maintenance.

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