Method for continuous lithium separation by fractional ion exchange after potassium precipitation from old brine

Abstract

This invention relates to the field of comprehensive utilization technology of salt lake brine resources, and discloses a continuous ion exchange stage method for lithium extraction from old brine after potassium precipitation. The method includes: (1) pretreating the old brine raw material after potassium precipitation to remove solid impurities, and then subjecting the pretreated raw material to primary adsorption in a primary rotary disc continuous ion exchange device to obtain a primary adsorption tail liquid with a lithium ion concentration of 0.05-0.2 g / L; (2) subjecting the primary adsorption tail liquid to secondary adsorption in a secondary rotary disc continuous ion exchange device to obtain a secondary adsorption tail liquid with a lithium ion concentration of 0.8-3.0 mg / L; the volume ratio of the adsorption bed of the primary rotary disc continuous ion exchange device to the adsorption bed of the secondary rotary disc continuous ion exchange device is 5-20:1. This method achieves deep recovery of lithium ions from old brine after potassium precipitation while ensuring high throughput capacity, and simultaneously optimizes equipment investment and operating costs.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of salt lake brine resources, specifically to a method for continuous ion exchange and graded lithium extraction from old brine after potassium precipitation. Background Technology

[0002] Salt lake brine is an important source of lithium resources. Old brine, a byproduct of potassium extraction from salt lakes, contains a high concentration of lithium ions, but also exhibits extremely high magnesium-to-lithium ratios (typically >80:1), high salinity, and high chloride ion content. Currently, among lithium extraction technologies for old salt lake brine, ion exchange adsorption is widely used due to its advantages such as simple operation, good adsorption selectivity, and strong process adaptability. Continuous ion exchange (IEE) technology, compared to intermittent IEE, features high processing efficiency, continuous feedstock, and strong industrial adaptability, making it one of the mainstream processes for large-scale lithium extraction.

[0003] In existing technologies, lithium extraction from old salt lake brine is mostly carried out using single-stage continuous ion-exchange devices or multi-stage non-rotating disk conventional ion-exchange devices in series for adsorption, which has many technical drawbacks: (1) Single-stage continuous lithium extraction does not fully recover lithium ions. The lithium ion concentration in the tail liquid is usually still at a high level (generally ≥150mg / L), and the lithium yield is difficult to exceed 95%, resulting in a waste of lithium resources. (2) Some multi-stage adsorption processes use intermittent operation, which cannot achieve continuous processing of raw materials, resulting in low industrial production efficiency. Furthermore, they do not address the characteristics of the impurity ion composition of the old brine after potassium precipitation (high Mg content). 2+、 High Cl - Adapting process parameters (e.g., etc.) limits adsorption selectivity and recovery efficiency; (3) Existing multi-stage ion-exchange processes are mostly scaled up in two stages or use the same process parameters. They do not consider the asymmetric distribution of adsorption load and desorption load between the two stages, resulting in redundant equipment investment, excessive dilution of lithium-rich desorbent, and high operating costs. (4) Existing technologies lack dynamic synergistic control strategies for tail liquid concentration between two adsorption stages. When the raw material concentration fluctuates, the system stability is poor and the total yield is difficult to reach more than 99%.

[0004] Therefore, there is an urgent need to develop a method for extracting lithium from potassium-treated brine that can achieve deep recovery of lithium ions from the brine after potassium precipitation while ensuring high-throughput processing capacity and optimizing equipment investment and operating costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the limitations of existing methods for extracting lithium from potassium-treated brine, including limited lithium-ion adsorption selectivity and recovery efficiency, high operating costs, and poor stability. In particular, it addresses the difficulty in reconciling selective lithium-ion adsorption, high-yield extraction, and large-scale industrial production capacity. This invention provides a continuous ion-exchange staged lithium extraction method from potassium-treated brine. This method constructs an asymmetric two-stage synergistic control system of "first-stage capacity enhancement and second-stage yield assurance," achieving deep recovery of lithium ions from potassium-treated brine while ensuring high-throughput processing capacity and optimizing equipment investment and operating costs.

[0006] To achieve the above objectives, the present invention provides a method for continuous cross-linking and fractional lithium extraction from old brine after potassium precipitation, the method comprising the following steps: (1) The old brine raw material after potassium precipitation is pretreated to remove solid impurities. Then the pretreated raw material is subjected to primary adsorption in a primary rotary disc continuous ion exchange device to obtain a primary adsorption tail liquid with a lithium ion concentration of 0.05-0.2 g / L. The adsorption bed of the primary rotary disc continuous ion exchange device is the first lithium ion adsorbent. (2) The primary adsorption tail liquid is subjected to secondary adsorption in a secondary rotating disc continuous ion exchange device to obtain a secondary adsorption tail liquid with a lithium ion concentration of 0.8-3.0 mg / L, wherein the adsorption bed of the secondary rotating disc continuous ion exchange device is a second lithium ion adsorbent. The volume ratio of the adsorption bed of the first-stage rotary continuous ion exchange device to that of the second-stage rotary continuous ion exchange device is 5-20:1.

[0007] Preferably, the volume ratio of the adsorption bed of the first-stage rotary continuous ion exchange device to the adsorption bed of the second-stage rotary continuous ion exchange device is 8-16:1.

[0008] Preferably, in step (1), the concentration of lithium ions in the old brine raw material after potassium precipitation is 1.5-3.5 g / L, preferably 2.5-3.2 g / L.

[0009] Preferably, the pH value of the potassium-precipitated brine raw material is 5-7, and the density is 1.25-1.35 g / cm³. 3 .

[0010] Preferably, in step (1), the conditions for the primary adsorption include: the feed flow rate of the pretreated raw material is 5-20 m / s. 3 / h, operating temperature is 15-40℃.

[0011] Preferably, in step (2), the conditions for the secondary adsorption include: the feed flow rate of the tail liquid from the primary adsorption is 5-20 m / s. 3 / h, operating temperature is 15-40℃.

[0012] Preferably, the first lithium-ion adsorbent and the second lithium-ion adsorbent are each independently selected from at least one of aluminum-based lithium-ion absorbents, titanium-based lithium-ion absorbents, and manganese-based lithium-ion absorbents.

[0013] Preferably, the method further includes: in the first-stage rotary continuous ion exchange device, when the first lithium-ion adsorbent is saturated with adsorption, a desorbent is supplied to the first-stage rotary continuous ion exchange device for desorption.

[0014] Preferably, in the two-stage rotary continuous ion exchange device, when the second lithium-ion adsorbent is saturated with adsorption, a desorbent is supplied to the two-stage rotary continuous ion exchange device for desorption.

[0015] Preferably, both the first lithium-ion adsorbent and the second lithium-ion adsorbent are aluminum-based lithium-ion absorbents, and the desorbent is RO water.

[0016] Preferably, the method further includes: post-processing the lithium-rich desorption solution collected during the desorption process to obtain lithium products.

[0017] Preferably, in the primary rotary continuous ion exchanger, the desorption conditions include: a desorbent flow rate of 150-300 m / s. 3 / h, temperature 25-40℃, time 5-30min.

[0018] Preferably, in the two-stage rotary continuous ion exchanger, the desorption conditions include: a desorbent flow rate of 10-50 m / s. 3 / h, temperature 25-40℃, time 5-30min.

[0019] Compared with the prior art, the present invention has the following advantages: (1) Through the asymmetric two-stage synergistic control of increasing production capacity through primary adsorption and maintaining recovery rate through secondary adsorption, the Li+ concentration in the tail liquid of primary adsorption is controlled at 0.05-0.2 g / L, and the tail liquid of secondary adsorption is further reduced to 0.8-3.0 mg / L. The total lithium recovery rate can reach more than 99%, which is far higher than the existing single-stage continuous ion-exchange process (≤95%), and completely solves the problem of lithium resource waste in single-stage lithium extraction process.

[0020] (2) By adjusting the secondary adsorption parameters in real time, the system's operational stability is significantly better than that of single-stage or conventional two-stage processes.

[0021] (3) The asymmetric configuration of the volume of the primary adsorption large bed + the volume of the secondary adsorption small bed is adopted. Compared with the scheme of using large bed volume in both stages, the total amount of adsorbent is greatly reduced, and the investment and operating costs are optimized.

[0022] (4) A rotary continuous desorption / exsorption device is used in series. The raw material is continuously fed from the first-stage adsorption to the second-stage adsorption, without any interruption or downtime waiting steps. Both stages are equipped with independent desorption systems, and adsorption and desorption can be carried out simultaneously, which greatly improves the efficiency of industrial production.

[0023] (5) The process is simple to operate and has low cost. The desorbed lithium-ion adsorbent can be directly recycled without additional regeneration steps. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the apparatus used in Embodiment 1 of the present invention for implementing the method of extracting lithium from old brine after potassium precipitation.

[0025] Explanation of reference numerals in the attached figures 1. Primary adsorption raw material tank; 2. Primary adsorption feed pump; 3. Primary rotary continuous ion exchange device; 4. Desorbent storage tank; 51. Primary desorbent delivery pump; 52. Secondary desorbent delivery pump; 61. First heating component; 62. Secondary heating component; 7. Primary adsorption tail liquid flow meter; 8. Online lithium ion concentration detector; 9. Secondary adsorption raw material tank; 10. Secondary adsorption feed pump; 11. Secondary rotary continuous ion exchange device; 12. Lithium-rich desorbent collection tank; 13. Tail liquid discharge / reuse pipeline. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] The method for extracting lithium from old brine after potassium precipitation according to the present invention includes the following steps: (1) The old brine raw material after potassium precipitation is pretreated to remove solid impurities. Then the pretreated raw material is subjected to primary adsorption in a primary rotary disc continuous ion exchange device to obtain a primary adsorption tail liquid with a lithium ion concentration of 0.05-0.2 g / L. The adsorption bed of the primary rotary disc continuous ion exchange device is the first lithium ion adsorbent. (2) The primary adsorption tail liquid is subjected to secondary adsorption in a secondary rotating disc continuous ion exchange device to obtain a secondary adsorption tail liquid with a lithium ion concentration of 0.8-3.0 mg / L, wherein the adsorption bed of the secondary rotating disc continuous ion exchange device is a second lithium ion adsorbent. The volume ratio of the adsorption bed of the first-stage rotary continuous ion exchange device to that of the second-stage rotary continuous ion exchange device is 5-20:1.

[0029] In some embodiments, in step (1), the concentration of lithium ions in the old brine raw material after potassium precipitation is 1.5-3.5 g / L, preferably 2.5-3.2 g / L. As a specific example, the concentration of lithium ions in the old brine raw material after potassium precipitation can be 2.5 g / L, 2.6 g / L, 2.7 g / L, 2.8 g / L, 2.9 g / L, 3 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, or 3.5 g / L.

[0030] In the method described in this invention, no specific limitation is made on the source of the old brine raw material after potassium precipitation. Various types of old brine raw materials commonly used in the art can be directly applied, exhibiting good versatility and adaptability. In some preferred embodiments, the old brine raw material after potassium precipitation comes from Yiliping Salt Lake, and the concentrations of the main ions in the old brine raw material are in the following ranges: lithium ion concentration is 1.5-3.5 g / L, preferably 2.5-3.2 g / L; chloride ion concentration is 250-350 g / L; magnesium ion concentration is 100-150 g / L; sulfate ion concentration is 10-20 g / L; sodium ion concentration is 1-2 g / L; potassium ion concentration is 0.1-0.5 g / L; and calcium ion concentration is 0.01-0.1 g / L.

[0031] In some embodiments, in step (1), the pH value of the potassium-precipitated brine raw material is 5-7, preferably 5.5-6.5; and the density is 1.2-1.35 g / cm³. 3 .

[0032] In some embodiments, the present invention does not specifically limit the specific operational procedures for pretreating the old brine raw material after potassium precipitation in the salt lake to remove solid impurities as described in step (1). Conventional and commonly used impurity removal methods in the art are applicable here, including but not limited to filtration, centrifugation, sedimentation and other processes that can effectively remove suspended solid impurities in the system, and can be selected according to actual production needs.

[0033] In the method described in this invention, the primary rotary continuous ion exchange device comprises multiple adsorption columns. These multiple adsorption columns work synergistically to achieve efficient adsorption and separation of lithium ions in the brine, thereby improving adsorption efficiency and throughput. This invention does not impose a specific limit on the number of adsorption columns; an appropriate number can be flexibly selected based on the actual processing capacity, lithium extraction efficiency requirements, and overall equipment layout. Those skilled in the art can make reasonable adjustments based on actual production needs.

[0034] In the method described in this invention, the primary rotary continuous ion exchange device is equipped with an inlet for pretreated old brine raw material, an outlet for primary adsorption tail liquid, an inlet for desorbent, and an outlet for lithium-rich desorbent, so as to realize the continuous feeding of pretreated old brine raw material, the smooth discharge of primary adsorption tail liquid, the precise introduction of desorbent, and the collection and export of lithium-rich desorbent, thereby ensuring the continuous and stable operation of the primary ion exchange lithium extraction process.

[0035] In some embodiments, in step (1), the conditions for the primary adsorption include: the feed flow rate of the pretreated raw material is 5-20 m / s. 3 / h, preferably 8-12m 3 / h; the operating temperature is 15-40℃, preferably 20-30℃. As a specific example, the feed flow rate of the pretreated raw material can be 8m / h. 3 / h、9m 3 / h, 10m 3 / h、11m 3 / h or 12m 3 / h; the operating temperature of the primary adsorption is 20℃, 22℃, 25℃, 26℃, 28℃ or 30℃.

[0036] In some preferred embodiments, the bed volume ratio of the adsorption bed of the first-stage rotary continuous ion exchanger to that of the second-stage rotary continuous ion exchanger is 8-16:1, more preferably 10-15:1. As a specific example, the bed volume ratio of the adsorption bed of the first-stage rotary continuous ion exchanger to that of the second-stage rotary continuous ion exchanger can be 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1.

[0037] In the method described in this invention, the two-stage rotary continuous ion exchange device comprises multiple adsorption columns. These multiple adsorption columns work synergistically to achieve efficient adsorption and separation of lithium ions in the brine, thereby improving adsorption efficiency and throughput. This invention does not impose a specific limit on the number of adsorption columns; an appropriate number can be flexibly selected based on the actual processing capacity, lithium extraction efficiency requirements, and overall equipment layout. Those skilled in the art can make reasonable adjustments based on actual production needs.

[0038] In the method described in this invention, the two-stage rotary continuous ion exchange device is provided with a primary adsorption tail liquid inlet, a secondary adsorption tail liquid outlet, a desorbent inlet, and a lithium-rich desorbent outlet, so as to realize the continuous feeding of the primary adsorption tail liquid, the smooth discharge of the secondary adsorption tail liquid, the precise introduction of the desorbent, and the collection and export of the lithium-rich desorbent, thereby ensuring the continuous and stable operation of the secondary ion exchange lithium extraction process.

[0039] In some embodiments, in step (2), the conditions for the secondary adsorption include: the feed flow rate of the primary adsorption tail liquid is 5-20 m / s. 3 / h, preferably 8-12m 3 / h; the operating temperature is 15-40℃, preferably 20-30℃. As a specific example, the feed flow rate of the stage adsorption tail liquid can be 8m / h. 3 / h、9m 3 / h, 10m 3 / h、11m 3 / h or 12m 3 / h; the operating temperature of the secondary adsorption is 20℃, 22℃, 25℃, 26℃, 28℃, or 30℃. In this invention, the feed flow rate of the primary adsorption tail liquid can be adjusted according to the lithium ion concentration in the primary adsorption tail liquid.

[0040] In some embodiments, the first lithium-ion adsorbent and the second lithium-ion adsorbent are each independently selected from at least one of aluminum-based lithium-ion absorbents, titanium-based lithium-ion absorbents, and manganese-based lithium-ion absorbents. Preferably, the first lithium-ion adsorbent and the second lithium-ion adsorbent are aluminum-based lithium-ion absorbents.

[0041] In some embodiments, the method further includes: in the primary rotary continuous ion exchange device, when the first lithium-ion adsorbent is saturated with adsorption, supplying a desorbent to the primary rotary continuous ion exchange device for desorption.

[0042] In some embodiments, in the primary rotary continuous ion exchanger, the desorption conditions include: a desorbent flow rate of 150-300 m / s. 3 / h, preferably 200-260m3 / h; temperature is 25-40℃, preferably 30-35℃; time is 5-30min, preferably 10-15min.

[0043] In some embodiments, the method further includes: in the two-stage rotary continuous ion exchange device, when the second lithium-ion adsorbent is saturated with adsorption, supplying a desorbent to the two-stage rotary continuous ion exchange device for desorption.

[0044] In some embodiments, in the two-stage rotary continuous ion exchanger, the desorption conditions include: a desorbent flow rate of 10-50 m / s. 3 / h, preferably 20-30m 3 / h; temperature is 25-40℃, preferably 30-35℃; time is 5-30min, preferably 10-15min.

[0045] In some embodiments, the type of desorbent can be flexibly determined according to the specific types of the first and second lithium-ion adsorbents used in the lithium extraction process described above, to ensure that the characteristics of the desorbent and adsorbent are compatible and to guarantee the desorption effect.

[0046] In some preferred embodiments, both the first lithium-ion adsorbent and the second lithium-ion adsorbent are aluminum-based lithium-ion adsorbents, and RO water is used as the desorbent. This combination can not only effectively achieve efficient desorption of lithium ions from the adsorbent, but also the RO water is readily available and has a low cost, which can further optimize the economic efficiency of the process, while avoiding the introduction of additional impurities that affect the purity of subsequent lithium resource recovery.

[0047] In some embodiments, the method further includes post-processing the lithium-rich desorption solution collected during the desorption process to obtain a high-purity lithium product. The post-processing process includes, but is not limited to, unit operations such as nanofiltration, electrodialysis, deep impurity removal, and evaporation concentration, which can be flexibly selected and combined according to actual production needs, product purity indicators, and on-site conditions. The unit operations such as nanofiltration, electrodialysis, deep impurity removal, and evaporation concentration are conventional procedures in the art and will not be described in detail again.

[0048] In this invention, the lithium-rich desorbent obtained from the desorption of the primary adsorption process and the lithium-rich desorbent obtained from the desorption of the secondary adsorption process can be flexibly collected according to the actual production process requirements. They can be collected separately and then subjected to subsequent evaporation, concentration and purification treatment, or they can be collected together and then subjected to subsequent treatment.

[0049] The present invention further provides a system for implementing the method for extracting lithium from old brine after potassium precipitation as described above. The system includes a pretreatment unit, a primary rotary continuous ion exchange device, a primary desorption system, an interstage online detection unit, a central control system, a secondary adsorption raw material tank, a secondary rotary continuous ion exchange device, a secondary desorption system, and a lithium-rich desorption liquid collection tank.

[0050] The pretreatment unit includes a pretreatment device and a primary adsorption raw material tank, and the outlet of the primary adsorption raw material tank is connected to a primary adsorption feed pump.

[0051] The primary rotary continuous ion exchange device is equipped with an inlet for pretreated old brine raw material, an outlet for primary adsorption tail liquid, an inlet for desorbent, and an outlet for lithium-rich desorbent.

[0052] The primary desorption system includes a first desorbent storage tank, a first desorbent delivery pump, and a first heating component. The outlet of the first desorbent storage tank is connected to the desorbent inlet of the primary rotary continuous ion exchange device.

[0053] The interstage online detection unit is installed on the outlet pipeline of the first-stage adsorption tail liquid of the first-stage rotary continuous ion exchange device. It includes a first-stage adsorption tail liquid flow meter and an online lithium ion concentration detector, which is used to monitor the lithium concentration in the first-stage adsorption tail liquid in real time and transmit the signal to the central control system.

[0054] The central control system is used to receive signals from the lithium ion concentration online detector in the inter-stage online detection unit, and to control and adjust the speed of the secondary adsorption feed pump or the adsorption cycle of the secondary rotary continuous ion exchange device.

[0055] The secondary adsorption feed tank is used to store the primary adsorption tail liquid from the primary rotary continuous ion exchange device, which serves as the feed for the secondary adsorption.

[0056] The two-stage rotary continuous ion exchange device is equipped with a primary adsorption tail liquid inlet, a secondary adsorption tail liquid outlet, a desorbent inlet, and a lithium-rich desorbent outlet.

[0057] The secondary desorption system includes a second desorbent storage tank, a second desorbent delivery pump, and a second heating component. The outlet of the second desorbent storage tank is connected to the desorbent inlet of the secondary rotary continuous ion exchange device.

[0058] The inlet of the lithium-rich desorption liquid collection tank is connected to the lithium-rich desorption liquid outlet of the first-stage rotary continuous ion exchange device and the second-stage rotary continuous ion exchange device, respectively.

[0059] In some embodiments, the system further includes a tail liquid discharge / reuse pipeline connected to the secondary adsorption tail liquid outlet of the two-stage rotary continuous ion exchange device, for discharging the final tail liquid or transporting it to subsequent comprehensive utilization processes.

[0060] In some embodiments, when the desorbents used in the primary rotary continuous ion exchange device and the secondary rotary continuous ion exchange device are of the same type, in order to simplify the process flow, reduce equipment configuration, reduce equipment investment and floor space, and facilitate the unified storage, transportation and management of the desorbent, the first desorbent storage tank and the second desorbent storage tank can be combined into a single shared storage tank.

[0061] The following examples further illustrate the continuous cross-linking and fractional lithium extraction method for old brine after potassium precipitation according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0062] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0063] In the following examples and comparative examples, the raw material for the potassium-precipitated brine was from Yiliping Salt Lake; The aluminum-based lithium-ion adsorbent was purchased from Jiangsu Jiuwu High-Tech Co., Ltd. The titanium-based lithium-ion adsorbent was purchased from Jiangsu Haipu Functional Materials Co., Ltd. The manganese-based lithium-ion adsorbent was purchased from Xinjiang Tailixin Mining Co., Ltd.

[0064] Example 1 This embodiment is in Figure 1 The device shown in the schematic diagram is implemented in a system comprising: a pretreatment device, a primary adsorption raw material tank 1, a primary adsorption feed pump 2, a primary rotary continuous ion exchange device 3, a desorbent storage tank 4, a primary desorbent delivery pump 51, a secondary desorbent delivery pump 52, a first heating component 61, a second heating component 62, a primary adsorption tail liquid flow meter 7, an online lithium ion concentration detector 8, a central control system, a secondary adsorption raw material tank 9, a secondary adsorption feed pump 10, a secondary rotary continuous ion exchange device 11, a lithium-rich desorbent collection tank 12, and a tail liquid discharge / reuse pipeline 13; In both the primary rotary continuous ion exchange device 3 and the secondary rotary continuous ion exchange device 11, the lithium-ion adsorbent is aluminum-based lithium-ion adsorbent, and the desorbent is RO water. The primary rotary continuous ion exchange device 3 comprises 30 adsorption columns, each filled with 16m of aluminum-based lithium ion adsorbent. 3 ; The two-stage rotary continuous ion exchange device 11 comprises 30 adsorption columns, each filled with 1.2m of aluminum-based lithium-ion adsorbent. 3 .

[0065] In this embodiment, in the old brine raw material after potassium precipitation, Li + Initial concentration 3.0 g / L, impurity ion concentration Na + 1.460 g / L, K + 0.315 g / L, Mg 2+ 116g / L, Ca 2+ 0.022 g / L, SO4 2- 14.5g / L, Cl - 296.3 g / L, pH=5.5, density 1.3 g / cm³ 3 .

[0066] The specific method is as follows: (1) The potassium-precipitated old brine raw material is transported to the pretreatment device for pretreatment to remove solid impurities, and the pretreated raw material is transported to the primary adsorption raw material tank 1 for storage. (2) The pretreated raw material from the primary adsorption raw material tank 1 is fed through the primary adsorption feed pump 2 at a speed of 10.5 m. 3 The lithium ion solution is fed to the primary rotary continuous ion exchange unit 3 at a flow rate of / h for primary adsorption, resulting in a primary adsorption tail liquid with a lithium ion concentration of 0.11g / L, which is then transported to the secondary adsorption raw material tank 9 for storage; wherein, the operating temperature of the primary adsorption is 25℃. (3) The primary adsorption tail liquid from the secondary adsorption raw material tank 9 is fed through the secondary adsorption feed pump 10 at a speed of 10.5 m. 3 The lithium ion concentration is 1.5 mg / L and the lithium ion concentration is 1.5 mg / L. The secondary adsorption tail liquid is then discharged from the system through the tail liquid discharge / reuse pipeline 13. The operating temperature of the secondary adsorption is 25°C. (4) The RO water from the desorbent storage tank 4 is pumped through the primary desorbent transfer pump 51 at a speed of 240m³ / h. 3 The RO water is fed into the first-stage rotary continuous ion exchange device 3 at a flow rate of / h for desorption for 13.5min, and the resulting lithium-rich desorbed solution is fed into the desorbed solution collection tank 12 for collection; wherein, the RO water entering the first-stage rotary continuous ion exchange device 3 is heated by the first heating component 61 to make the desorption temperature 30℃. (5) The RO water from the desorbent storage tank 4 is pumped through the secondary desorbent transfer pump 52 at a speed of 25m. 3 / The RO water is fed into the secondary rotary continuous ion exchange unit 11 at a flow rate of h for desorption for 13 minutes. The resulting lithium-rich desorbate is then collected in the desorbate collection tank 12. The collected lithium-rich desorbate undergoes post-processing steps such as nanofiltration for magnesium removal, MVR concentration, and lithium precipitation to obtain lithium carbonate product. The RO water entering the secondary rotary continuous ion exchange unit 11 is heated by the second heating component 62 to maintain a desorption temperature of 30°C.

[0067] Example 2 The method described in Example 1 is implemented, except that in step (2), the flow rate of the pretreated raw material is 9 m / s. 3 / h, so that the concentration of lithium ions in the tail liquid of the first-stage adsorption is 0.08g / L; In step (2), the flow rate of the primary adsorption tail liquid is 9 m / s. 3 / h, so that the lithium ion concentration in the secondary adsorption tail liquid is 0.8mg / L.

[0068] Example 3 The method described in Example 1 is implemented, except that in the potassium-precipitated brine raw material, Li + The initial concentration was 3.2 g / L, resulting in a lithium ion concentration of 0.15 g / L in the first-stage adsorption tail liquid and a lithium ion concentration of 2.5 mg / L in the second-stage adsorption tail liquid.

[0069] Example 4 The method described in Example 1 is implemented, except that in the potassium-precipitated brine raw material, Li + The initial concentration was 2.8 g / L, and the operating temperature for both primary and secondary adsorption was 30℃, resulting in a lithium ion concentration of 0.12 g / L in the primary adsorption tail liquid and a lithium ion concentration of 1.8 mg / L in the secondary adsorption tail liquid.

[0070] Example 5 The method described in Example 1 is followed, except that the two-stage rotating disc continuous ion exchange device 11 includes 30 adsorption columns, each filled with 0.8 m of aluminum-based lithium-ion adsorbent. 3 .

[0071] Example 6 The method described in Example 1 is followed, except that the two-stage rotating disc continuous ion exchange device 11 includes 30 adsorption columns, each filled with 3.2 m of aluminum-based lithium-ion adsorbent. 3 .

[0072] Example 7 The method described in Example 1 is implemented, except that in the first-stage rotary continuous ion exchange device 3, a titanium-based lithium-ion adsorbent is used instead of an aluminum-based lithium-ion adsorbent, and elution is performed using 0.1 wt% hydrochloric acid.

[0073] Example 8 The method described in Example 1 is implemented, except that in the two-stage rotary continuous ion exchange device 11, a manganese-based lithium ion adsorbent is used instead of an aluminum-based lithium ion adsorbent, and elution is performed with 0.1 wt% hydrochloric acid.

[0074] Comparative Example 1 The method described in Example 1 is implemented, except that the two-stage rotary continuous ion exchange device 11 contains 30 adsorption columns, each filled with 16 m³ of aluminum-based lithium ion adsorbent.

[0075] Comparative Example 2 The method described in Example 1 was implemented, except that the feed flow rate of the primary adsorption stage was changed to 15 m³ / h, so that the lithium ion concentration in the tail liquid of the primary adsorption stage was 0.3 g / L.

[0076] Comparative Example 3 Lithium extraction was performed using the aforementioned single-stage rotary continuous electrochemical exchange unit, with a raw material and feed flow rate of 10.5 m / s. 3 / h, adsorption temperature 25℃; desorption parameters: first-stage desorption flow rate 240m / .... 3 / h, time 13.5min.

[0077] Test case (1) Li in the lithium-rich desorption solutions collected in the examples and comparative examples + The concentrations are shown in Table 1.

[0078] (2) The present invention converts the unit lithium-rich liquid concentration power consumption + equipment operation power consumption into standard coal consumption, and uses Example 1 as the benchmark to test the energy consumption of lithium ion recovery in the Example and Comparative Example 1.0 method. The results are shown in Table 1.

[0079] (3) The present invention tested the yield of lithium carbonate prepared from the recovered lithium-rich desorption solution in the method test examples and comparative examples. The results are shown in Table 1.

[0080] (4) The present invention conducted stability tests on the apparatus used in Examples 1, 5, 6, Comparative Example 1 and Comparative Example 3. The test process is as follows: continuous cyclic adsorption-desorption operation, with the lithium yield dropping below 99% as the system failure point, and the number of stable cycles recorded; the results are shown in Table 1.

[0081] Table 1

[0082] As can be seen from the results in Table 1, the present invention employs an asymmetric two-stage rotary continuous ion exchange synergistic lithium extraction process, achieving a total lithium recovery rate of over 99%, which is significantly higher than that of a single-stage continuous ion exchange process (Comparative Example 3) and an equal-volume two-stage adsorption process (Comparative Example 1). The lithium-rich desorption solution has a higher lithium-ion concentration, resulting in a significant reduction in energy consumption for subsequent evaporation and concentration. At the same time, the system has a longer continuous and stable operating cycle and better industrial adaptability.

[0083] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A continuous deionization fractional lithium extraction method for post-potassium old brine, characterized in that, The method includes the following steps: (1) The old brine raw material after potassium precipitation is pretreated to remove solid impurities. Then the pretreated raw material is subjected to primary adsorption in a primary rotary disc continuous ion exchange device to obtain a primary adsorption tail liquid with a lithium ion concentration of 0.05-0.2 g / L. The adsorption bed of the primary rotary disc continuous ion exchange device is the first lithium ion adsorbent. (2) The primary adsorption tail liquid is subjected to secondary adsorption in a secondary rotating disc continuous ion exchange device to obtain a secondary adsorption tail liquid with a lithium ion concentration of 0.8-3.0 mg / L, wherein the adsorption bed of the secondary rotating disc continuous ion exchange device is a second lithium ion adsorbent. The volume ratio of the adsorption bed of the first-stage rotary continuous ion exchange device to that of the second-stage rotary continuous ion exchange device is 5-20:

1.

2. The method of claim 1, wherein, The volume ratio of the adsorption bed of the first-stage rotary continuous ion exchange device to that of the adsorption bed of the second-stage rotary continuous ion exchange device is 8-16:

1.

3. The method according to claim 1 or 2, characterized in that, In step (1), the concentration of lithium ions in the old brine raw material after potassium precipitation is 1.5-3.5 g / L, preferably 2.5-3.2 g / L; Preferably, the pH of the post-potash-depleted raw brine is between 5 and 7 and the density is between 1.25 and 1.35 g / cm 3 .

4. The method according to any one of claims 1-3, characterized in that, In step (1), the conditions of the primary adsorption include that the feeding flow rate of the pretreated raw material is 5-20 m 3 / h, and the operating temperature is 15-40℃.

5. The method according to any one of claims 1-4, characterized in that, In step (2), the conditions of the secondary adsorption include that the feeding flow rate of the tail liquid of the primary adsorption is 5-20 m 3 / h, and the operating temperature is 15-40℃.

6. The method according to any one of claims 1-5, characterized in that, The first lithium-ion adsorbent and the second lithium-ion adsorbent are each independently selected from at least one of aluminum-based lithium-ion absorbents, titanium-based lithium-ion absorbents, and manganese-based lithium-ion absorbents.

7. The method according to claim 6, characterized in that, The method further includes: in the primary rotary disc continuous ion exchange device, when the first lithium-ion adsorbent is saturated with adsorption, supplying a desorbent to the primary rotary disc continuous ion exchange device for desorption; and / or In the two-stage rotary continuous ion exchange device, when the second lithium-ion adsorbent is saturated with adsorption, a desorbent is supplied to the two-stage rotary continuous ion exchange device for desorption.

8. The method according to claim 7, characterized in that, Both the first lithium-ion adsorbent and the second lithium-ion adsorbent are aluminum-based lithium-ion absorbents, and the desorbent is RO water.

9. The method according to claim 7 or 8, characterized in that, The method further includes: post-processing the lithium-rich desorption solution collected during the desorption process to obtain lithium products.

10. The method according to claim 7, characterized in that, In the primary rotating disc continuous ion exchange device, the desorption conditions include: the flow rate of the desorption agent is 150-300 m 3 / h, the temperature is 25-40℃, and the time is 5-30 min; and / or In the secondary rotating disc continuous ion exchange device, the desorption conditions include: desorption agent flow rate is 10-50 m 3 / h, temperature is 25-40℃, and time is 5-30 min.

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