Process method for synergistically extracting lithium, potassium and boron in salt lake

Abstract

The invention provides a process method for synergistically extracting lithium, potassium and boron in a salt lake. The method comprises the following steps: pretreating salt lake raw brine, mixing the pretreated salt lake raw brine with a first-stage extraction organic phase, and carrying out multi-stage counter-current extraction to obtain a raffinate water phase; adding a potassium precipitator into the raffinate water phase to enable potassium ions to form precipitates, and carrying out solid-liquid separation to generate boron-poor potassium-poor lithium-rich brine; enabling the boron-poor and potassium-poor lithium-rich brine to be in contact with the lithium ion sieve adsorbent, adsorbing lithium ions on the lithium ion sieve adsorbent, and eluting the lithium ions by using an eluent to obtain a lithium-rich solution. The invention provides a brand new lithium, potassium and boron integrated extraction process with high synergism, the process can be simplified, the cost can be reduced, the environment can be protected, and the process has great technical value and economic significance.

Description

Technical Field

[0001] This invention relates to the fields of salt lake chemical industry and inorganic salt separation technology, and in particular to a process for the synergistic extraction of lithium, potassium and boron from salt lakes. Background Technology

[0002] Salt lakes are important global strategic mineral resource reserves, rich in elements such as lithium, potassium, boron, and magnesium. With the rapid development of new energy vehicles, energy storage industries, and fine chemicals, the market demand for lithium, potassium, and boron continues to rise. The efficient and green extraction of these resources from salt lakes has become a global research hotspot and a focus of technological competition.

[0003] Currently, industrial development of salt lake resources mostly employs "separate extraction" or "tandem" processes. For example, potash fertilizer production primarily relies on large-scale salt pan drying and flotation crystallization, processes that are energy-intensive, require large land areas, and are highly dependent on climate. Lithium extraction methods are diverse, including precipitation, adsorption, solvent extraction, and membrane separation. Among these, adsorption is considered an effective means of treating high magnesium-to-lithium ratio salt lake brines due to its high selectivity, while solvent extraction, especially synergistic solvent extraction systems (SSX), has also attracted considerable attention due to its high efficiency and low energy consumption. Boron extraction typically employs extraction or precipitation methods.

[0004] Currently, existing methods for extracting lithium, potassium, and boron from salt lakes have the following drawbacks: 1. Lack of synergy and low resource utilization: Most existing processes are designed for single elements, such as "potassium first, then lithium" or "lithium first, then boron." In this series-processing approach, each unit operation is independent and may even interfere with each other. For example, in the lithium extraction process, boron and magnesium ions are impurities that need to be removed beforehand, which increases the complexity and cost of the process. Furthermore, the composition of the old brine after potassium extraction is even more complex, posing a greater challenge to subsequent lithium extraction.

[0005] 2. Long process flow and high energy and material consumption: The sequential extraction process for multiple elements is lengthy, involving multiple steps such as evaporation and concentration, precipitation, and filtration, resulting in huge energy consumption and material loss. For example, the traditional evaporation and precipitation method is not only inefficient, but also produces a large amount of tailings and waste liquid.

[0006] 3. High environmental burden: Large-scale salt field drying has altered the ecological landscape, and some precipitation and extraction methods use large amounts of chemical reagents, which can easily cause secondary pollution if not handled properly. Summary of the Invention

[0007] The embodiments of the present invention provide a process for the synergistic extraction of lithium, potassium and boron from salt lakes, so as to achieve synergistic and efficient comprehensive recovery of lithium, potassium and boron from salt lakes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A process for the synergistic extraction of lithium, potassium, and boron from salt lakes, comprising: After pretreatment, the raw brine from the salt lake is mixed with the primary extraction organic phase and subjected to multi-stage countercurrent extraction. Once the extraction is complete, the raffinate aqueous phase is obtained. A potassium precipitant is added to the raffinate aqueous phase to form potassium ions as precipitates, and then a boron- and potassium-poor lithium-rich brine is generated through solid-liquid separation. The boron- and potassium-poor lithium-rich brine is brought into contact with a lithium-ion sieve adsorbent, whereby lithium ions are adsorbed onto the adsorbent. The lithium ions are then eluted with an eluent to obtain a lithium-rich solution.

[0010] Preferably, after pretreatment of the raw brine from the salt lake, it is mixed with the primary extraction organic phase for multi-stage countercurrent extraction. Upon completion of the extraction, the raffinate aqueous phase is obtained, comprising: The raw brine of the salt lake is filtered to remove suspended impurities, resulting in clarified brine. The pH value of the clarified brine is adjusted to an acidic range of 1.0-3.0. The brine is then mixed with the primary extraction organic phase for multi-stage countercurrent extraction. After extraction, extract and raffinate are obtained. The primary extraction organic phase consists of an extractant, a co-extractant, and a diluent. The extractant is an alcohol or diol compound containing ortho-dihydroxyl groups, and the co-extractant B is a neutral phosphooxy compound. After extraction, a boron-loaded organic phase and a raffinate aqueous phase containing lithium and potassium are obtained. The boron-loaded organic phase is back-extracted with NaOH solution to obtain a sodium borate-enriched solution.

[0011] Preferably, the extractant is a higher fatty alcohol or polyol with a carbon chain length of C8-C12, the volume percentage of the extractant in the primary extraction organic phase is 10%-30%, the co-extractant is tributyl phosphate, the volume percentage of the co-extractant in the primary extraction organic phase is 5%-30%, and the diluent is sulfonated kerosene.

[0012] Preferably, the addition of a potassium precipitant to the raffinate aqueous phase to form a potassium precipitate, followed by solid-liquid separation to generate a boron- and potassium-poor lithium-rich brine, comprises: The raffinate phase is indirectly heated using a plate heat exchanger or a tubular heat exchanger with hot water or steam to adjust its temperature to 15-35°C. An organophosphate potassium precipitant is then added to the raffinate phase after temperature adjustment. This precipitant selectively reacts with potassium ions in the raffinate phase to form a chelate precipitate. After separating the precipitated potassium, a boron- and potassium-poor lithium-rich brine and a potassium salt precipitate are generated. The organophosphate potassium precipitant is dipropylene glycol phenyl ether phosphate (DPPP) or tetraphenyl borate. The amount of organophosphate potassium precipitant added is 1.05-1.2 times the theoretically calculated molar amount of potassium ions.

[0013] Preferably, the method further includes: treating the potassium salt precipitate with dilute sulfuric acid to decompose it into a potassium sulfate solution and a regenerated DPPP precipitant; the potassium sulfate solution is evaporated, concentrated, crystallized, and dried to obtain a potassium sulfate product; and the regenerated DPPP precipitant is treated and returned to the precipitation process for recycling.

[0014] Preferably, the process of contacting the boron- and potassium-poor lithium-rich brine with a lithium-ion sieve adsorbent to adsorb lithium ions onto the adsorbent, and then eluting the lithium ions with an eluent to obtain a lithium-rich solution includes: After adjusting the pH of the boron- and potassium-poor lithium-rich brine to 7.0-11.0, the brine is passed through an adsorption tower filled with a lithium-ion sieve adsorbent. The lithium-ion sieve adsorbent is a core-shell structured manganese-titanium composite lithium-ion sieve. This core-shell structured manganese-titanium composite lithium-ion sieve has a manganese-titanium lithium-ion sieve as the core and a high-molecular organic matter as the shell. The core layer is composed of manganese-titanium composite oxides and has a three-dimensional porous structure, providing lithium-ion intercalation sites to achieve selective adsorption of lithium. The shell layer is formed by in-situ cross-linking of hydrophilic polymers, and the thickness can be controlled between 10-100 nm. After the boron- and potassium-poor lithium-rich brine enters the adsorption tower, the lithium ions in the brine first pass through the hydrophilic polymer shell. The shell acts as a molecular sieve barrier, selectively allowing lithium ions to pass through. The lithium ions further diffuse to the manganese-titanium composite oxide core layer, where they are specifically adsorbed into the lattice channels of the core layer through ion exchange or intercalation mechanisms. The unadsorbed sodium, magnesium, and calcium ions flow out of the adsorption tower with the brine. After adsorption saturation, a 0.01-0.5 mol / L hydrochloric acid, sulfuric acid, or citric acid solution is used as the eluent to elute the lithium ions enriched on the core-shell structured manganese-titanium composite lithium ion sieve, resulting in a lithium-rich solution. The eluted core-shell structured manganese-titanium composite lithium ion sieve is washed with water until neutral and then used for the next round of lithium ion adsorption.

[0015] Preferably, the lithium ion sieve adsorbent is a manganese-based ion sieve, a titanium-based ion sieve, or a manganese-titanium composite ion sieve.

[0016] Preferably, the functionalized shell layer of the core-shell structured manganese-titanium composite lithium-ion sieve is a hydrophilic organic substrate, which includes one or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, cellulose acetate butyrate, and sodium carboxymethyl cellulose.

[0017] As can be seen from the technical solutions provided by the embodiments of the present invention above, the embodiments of the present invention provide a novel and highly synergistic integrated extraction process for lithium, potassium and boron, which can simplify the process, reduce costs and protect the environment, and has significant technical value and economic significance.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A process flow diagram for the synergistic extraction of lithium, potassium, and boron from salt lakes, provided in an embodiment of the present invention; Figure 2 A schematic diagram illustrating the cyclic stability of a core-shell structured manganese-titanium composite ion sieve provided in an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0023] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0024] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0025] The processing flow of a method for the synergistic extraction of lithium, potassium, and boron from salt lakes provided in this embodiment of the invention is as follows: Figure 1 As shown, the processing steps include the following: Step S1: After pretreatment of the raw brine from the salt lake, it is mixed with the primary extraction organic phase for multi-stage countercurrent extraction. After extraction, the raffinate aqueous phase is obtained.

[0026] The raw or aged brine from the salt lake is filtered to remove suspended impurities, yielding clarified brine. The pH of the brine is then adjusted to an acidic range of 1.0-3.0, preferably 1.5-2.5. Under these acidic conditions, the brine is mixed with the primary extraction organic phase and subjected to multi-stage countercurrent extraction. Upon completion of extraction, the extract and raffinate aqueous phase are obtained.

[0027] The primary extraction organic phase consists of an extractant, a co-extractant, and a diluent. The extractant is an alcohol or diol compound containing ortho-dihydroxyl groups, and the co-extractant B is a neutral phosphorothioate compound. The extractant is a higher fatty alcohol or polyol with a carbon chain length of C8-C12, such as 2-ethylhexanol, and its volume percentage in the primary extraction organic phase is 10%-30%. The co-extractant B is tributyl phosphate (TBP), and its volume percentage in the primary extraction organic phase is 5%-30%. The diluent is sulfonated kerosene. After extraction, a boron-loaded organic phase and a raffinate aqueous phase containing lithium and potassium are obtained. The boron-loaded organic phase is back-extracted with NaOH solution to obtain a sodium borate-enriched solution. This sodium borate-enriched solution is acidified, crystallized, and dried to obtain a high-purity boric acid product, which is then washed and recycled.

[0028] This step utilizes the fact that, in an acidic medium, higher alcohols can form stable ester compounds with boric acid, thereby selectively extracting boron into the organic phase. Meanwhile, metal ions such as lithium, potassium, sodium, and magnesium, which are difficult to form stable complexes with alcohol extractants under these pH conditions, are mostly retained in the raffinate aqueous phase. The extraction process can be carried out countercurrently in a multi-stage centrifugal extractor to improve extraction efficiency.

[0029] Step S2: Add potassium precipitant to the raffinate aqueous phase to form potassium ions into a precipitate, and generate boron-poor, potassium-poor, lithium-rich brine through solid-liquid separation.

[0030] The raffinate phase is indirectly heated by hot water or steam using a plate heat exchanger or tubular heat exchanger to adjust the temperature of the raffinate phase obtained in step S1 to 15-35℃. A novel organic potassium phosphate precipitant is added to the raffinate phase after temperature adjustment to selectively react with potassium ions. After separating and precipitating potassium, a boron-poor, potassium-poor, lithium-rich brine and insoluble potassium salt precipitate are generated.

[0031] The novel organophosphate potassium precipitant is di(propylene glycol) phenyl ether phosphate (DPPP) or tetraphenyl borate, which forms a stable chelate precipitate with potassium ions. The amount of organophosphate potassium precipitant added is 1.05-1.2 times the theoretically calculated molar amount of potassium ions. After solid-liquid separation, potassium salt precipitate and boron- and potassium-poor lithium-rich brine are obtained.

[0032] Potassium salt precipitation is treated with dilute sulfuric acid to decompose and obtain potassium sulfate solution and regenerated DPPP precipitant. The potassium sulfate solution is then concentrated by evaporation, crystallization, and drying to obtain potassium sulfate product. The regenerated DPPP is returned to the precipitation process for recycling after simple treatment.

[0033] Step S3: Contact the boron- and potassium-poor lithium-rich brine with the lithium-ion sieve adsorbent to adsorb lithium ions onto the lithium-ion sieve adsorbent, and then elute the lithium ions with an eluent to obtain a lithium-rich solution.

[0034] The boron- and potassium-poor lithium-rich brine obtained after potassium separation and precipitation in step S2 is subjected to deep lithium extraction. Since the main interfering element boron and most of the potassium in the brine have been removed at this time, the relative concentration of lithium is increased. After adjusting the pH of the boron- and potassium-poor lithium-rich brine to 7.0-11.0, the brine is passed through an adsorption tower filled with a novel lithium-ion sieve adsorbent to achieve selective adsorption of lithium.

[0035] The novel lithium-ion sieve adsorbent is a novel core-shell structured manganese-titanium composite lithium-ion sieve. This ion sieve uses a high-capacity manganese-titanium lithium-ion sieve as its core and a highly stable, strongly hydrophilic, and acid-resistant high-molecular-weight organic compound as its shell. The core-shell structured manganese-titanium composite lithium-ion sieve has the following unique structural features: Core layer: composed of manganese-titanium composite oxides (such as L...) M or L Ti The core-shell structure, with its three-dimensional porous structure, provides numerous lithium-ion intercalation sites, enabling high-capacity and highly selective adsorption of lithium. The shell, formed by in-situ cross-linking of hydrophilic polymers (such as polyvinyl alcohol and polyethylene glycol), has a controllable thickness of 10–100 nm and provides the following functions: enhanced mechanical strength to prevent breakage of the ion sieve in the fluidized bed; improved hydrophilicity to promote rapid lithium-ion transport at the solid-liquid interface; and inhibition of manganese and titanium ion dissolution, significantly improving cycle stability, especially during acidic elution. The core-shell interface is tightly bound through chemical bonding or physical embedding, ensuring the shell does not detach or break during repeated adsorption-elution cycles.

[0036] After entering the adsorption tower, the boron- and potassium-poor lithium-rich brine undergoes the following treatment processes on the core-shell structured manganese-titanium composite lithium ion sieve: 1) Shell pre-diffusion: Lithium ions in the brine first pass through the hydrophilic polymer shell. The shell acts as a molecular sieve barrier, selectively allowing lithium ions to pass through while blocking the entry of large-sized or high-charge-density ions such as magnesium and calcium; 2) Core adsorption: Lithium ions further diffuse to the manganese-titanium composite oxide core layer and are specifically adsorbed into its lattice channels through ion exchange or intercalation mechanisms; 3) Impurity rejection: Unadsorbed sodium, magnesium, calcium, and other ions flow out of the adsorption tower with the brine, achieving deep purification of lithium; 4) Elution and regeneration: After adsorption saturation, a dilute acid elution solution is used to penetrate the shell in reverse, displacing the lithium ions intercalated in the core layer. During this process, the shell layer protects the core layer structure from acid corrosion, ensuring the long-term stable operation of the adsorbent.

[0037] This core-shell structure combines the high adsorption capacity and high adsorption rate of manganese-titanium lithium ion sieves. The internal core provides numerous adsorption sites, while the high-molecular organic binder offers excellent structural stability, hydrophilicity, and acid resistance (the external functionalized shell protects the core, accelerating ion transport during adsorption and preventing excessive dissolution in acidic eluents). This ensures high adsorption capacity while addressing the slow mass transfer rate after granulation, significantly improving cycle life and production efficiency. After adsorption saturation, the adsorption tower is washed with pure water or dilute brine to remove brine entrained between ion sieve particles. Then, a 0.01-0.5 mol / L hydrochloric acid, sulfuric acid, or citric acid solution is used as the eluent to elute the lithium ions enriched on the ion sieve, yielding a high-concentration, high-purity lithium-rich solution. After elution, the ion sieve is washed with water until neutral and then used for the next adsorption cycle, demonstrating excellent cycle performance.

[0038] Example 1: This embodiment describes a process for the synergistic extraction of lithium, potassium, and boron from a salt lake. The raw material used in this embodiment is a chloride-type salt lake brine, and its main ion concentrations are as follows: Ion L N Mg C

[0039] Concentration (g / L): 0.21, 60.0, 12.5, 45.0, 2.8, 180.0

[0040] The specific steps are as follows: Step 1, Boron Extraction: Take 1000L of the above brine and adjust the pH to 2.5 with hydrochloric acid. An organic extractant consisting of 20% (v / v) 2-ethyl-1,3-hexanediol, 10% (v / v) tributyl phosphate, and 70% (v / v) sulfonated kerosene is used in a four-stage countercurrent centrifugal extractor with an organic phase to aqueous phase (O / A) volume ratio of 1:3. Approximately 998L of raffinate aqueous phase is obtained after extraction. The raffinate aqueous phase contains… When the concentration was reduced to 0.12 g / L, the boron extraction rate reached 95.7%. The boron-loaded organic phase was back-extracted with 1.0 mol / L NaOH solution, and the back-extract was further processed to obtain 2.55 kg of boric acid product with a purity of 99.5%.

[0041] Step 2, Potassium Precipitation: The raffinate obtained in Step 1 was heated to 25°C, and 1.1 times the theoretical amount of di(propylene glycol) phenyl ether phosphate (DPPP) precipitant was added. The mixture was stirred for 30 minutes. Filtration yielded potassium-DPPP precipitate and approximately 995 L of lithium-rich filtrate. Analysis showed that the filtrate contained... When the concentration was reduced to 0.8 g / L, the potassium precipitation rate reached 93.6%. The potassium-DPPP precipitate was treated with sulfuric acid to regenerate DPPP and obtain 22.3 kg of potassium sulfate product (purity 98%).

[0042] Step 3, Lithium Extraction by Adsorption: Adjust the pH of the lithium-rich filtrate obtained in Step 2 to 9.5 and pass it through an adsorption column packed with a 150L core-shell manganese-titanium composite ion sieve at a flow rate of 5 BV / h. After adsorption saturation, wash with water and then elute with 0.1 mol / L HCl solution at a flow rate of 2 BV / h, collecting approximately 450L of lithium chloride eluent, of which L... The concentration was 0.41 g / L. The lithium adsorption rate reached 96.5%, and the elution rate reached 98%. After concentrating the eluent, sodium carbonate solution was added to precipitate lithium, yielding 0.98 kg of battery-grade lithium carbonate (99.6% purity).

[0043] In this embodiment, the total recovery rate of boron was 95.1%, the total recovery rate of potassium was 92.8%, and the total recovery rate of lithium was 91.2%.

[0044] Example 2: The raw material used in this example is a chloride-type salt lake brine, and its main ion concentrations are as follows: Ion L N Mg C

[0045] Concentration (g / L): 0.15, 40.0, 8.2, 75.0, 1.9, 35.0

[0046] The specific steps are as follows: Step 1, Boron Extraction: Take 1000L of the above brine and adjust the pH to 2.0 with hydrochloric acid. An organic extractant consisting of 25% (v / v) 2-ethyl-1,3-hexanediol, 10% (v / v) tributyl phosphate, and 65% (v / v) sulfonated kerosene is used in a four-stage countercurrent centrifugal extractor. The organic phase to aqueous phase (O / A) volume ratio is 1:3. Approximately 998L of raffinate aqueous phase is obtained after extraction. The raffinate aqueous phase contains… When the concentration was reduced to 0.07 g / L, the boron extraction rate reached 96.2%.

[0047] Step 2, Potassium Precipitation: The raffinate obtained in Step 1 is heated to 20°C, and 1.2 times the theoretical amount of di(propylene glycol) phenyl ether phosphate (DPPP) precipitant is added. The mixture is stirred for 30 minutes. Filtration yields potassium-DPPP precipitate and approximately 995 L of lithium-rich filtrate. The filtrate contains... When the concentration was reduced to 0.62 g / L, the potassium precipitation rate reached 92.5%.

[0048] Step 3, Lithium Extraction by Adsorption: Adjust the pH of the lithium-rich filtrate obtained in Step 2 to 9.0 and pass it through an adsorption column packed with a 150L core-shell manganese-titanium composite ion sieve at a flow rate of 3 BV / h. After adsorption saturation, wash with water and then elute with 0.05 mol / L HCl solution at a flow rate of 2 BV / h, collecting approximately 450L of lithium chloride eluent, of which L... The concentration was 0.41 g / L. The lithium adsorption rate reached 95%, and the elution rate reached 98.6%. After concentrating the eluent, sodium carbonate solution was added to precipitate lithium, yielding industrial-grade lithium carbonate (99.3% purity).

[0049] Example 3: The raw material used in this example is a chloride-type salt lake brine, and its main ion concentrations are as follows: Ion L Mg

[0050] Concentration (g / L): 0.08, 5.5, 20.0, 1.2

[0051] A process for the synergistic extraction of lithium, potassium, and boron from salt lakes, comprising the following steps: The process steps are similar to those in Example 1, with the main difference being the adjustment of reagent dosage to accommodate low-concentration raw materials. 1. Boron extraction: The volume ratio of organic extractant phase to aqueous phase (O / A) was adjusted to 1:4, and the boron extraction rate was 97.1%.

[0052] 2. Precipitation and potassium extraction: The amount of DPPP precipitant added was 1.05 times the theoretical amount. The potassium precipitation rate was 94.0%.

[0053] 3. Lithium Extraction by Adsorption: The lithium concentration in the lithium-rich filtrate is low. Before adsorption, it is first concentrated using a nanofiltration membrane to increase the lithium concentration to 0.15 g / L before adsorption. The final product yields 0.37 kg of battery-grade lithium carbonate.

[0054] Example 4

[0055] Figure 2 This diagram illustrates the cyclic stability of a core-shell structured manganese-titanium composite ion sieve, as provided in an embodiment of the present invention. This embodiment aims to verify the cyclic stability of the core-shell structured manganese-titanium composite ion sieve.

[0056] The lithium-rich, potassium-poor filtrate obtained in step 2 of Example 1 was subjected to 50 consecutive adsorption-desorption cycles using the same batch of 10L core-shell structured manganese-titanium composite ion sieve. The experimental conditions were the same as in step 3 of Example 1. The adsorption capacity of the adsorbent for lithium was measured after each cycle. At the beginning of the first cycle, the saturated adsorption capacity of the adsorbent was 21.5 mg / g. After 50 cycles, the adsorption capacity remained at 20.8 mg / g, with a capacity retention rate of 96.7%.

[0057] In summary, this invention organically integrates boron extraction, potassium extraction, and lithium extraction into a continuous process flow, achieving the tiered separation and recovery of these three high-value elements. Through optimized process sequence and conditions, the total recovery rate of boron can reach over 95%, potassium over 92%, and lithium over 90%, achieving complete utilization of salt lake resources with extremely high comprehensive economic benefits. This invention's method can efficiently and systematically recover various valuable components from waste titanium-based adsorbents, realizing the recycling of titanium sources, reducing environmental pollution in environmentally fragile areas such as Tibet, and demonstrating feasibility and significant effectiveness.

[0058] The method of the present invention also has the following beneficial effects: 1. Synergistic and efficient, with high overall recovery rate: This invention organically integrates the three processes of boron extraction, potassium extraction, and lithium extraction into a continuous process flow, achieving the tiered separation and recovery of these three high-value elements. Through optimized process sequence and conditions, the total recovery rate of boron can reach over 95%, the total recovery rate of potassium can reach over 92%, and the total recovery rate of lithium can reach over 90%, realizing the full utilization of salt lake resources and achieving extremely high comprehensive economic benefits.

[0059] 2. Innovative Materials, Performance Breakthrough: This invention proposes the use of di(propylene glycol) phenyl ether phosphate (DPPP) as a potassium precipitant and a core-shell structured manganese-titanium composite ion sieve as a lithium ion sieve. The former achieves efficient, safe, and low-cost potassium precipitation and recycling; the latter overcomes the shortcomings of slow mass transfer rate of traditional titanium-based lithium ion sieves and high dissolution loss of manganese-based lithium ion sieves, achieving a balance between high adsorption rate and long cycle life, making it particularly suitable for complex alkaline salt lake brines with high magnesium-to-lithium ratios.

[0060] 3. Process integration and cost reduction: The integrated design reduces the number of separate pretreatment and post-treatment units, simplifying the process and lowering equipment investment and operating costs. The efficient recycling of precipitants and extractants significantly reduces material consumption.

[0061] 4. Green and environmentally friendly: The co-extraction process reduces the transfer and processing of intermediate products, and the raffinate and waste liquid are utilized in stages, significantly reducing the total discharge of "three wastes" (waste gas, wastewater, and solid waste). In particular, the adsorption lithium extraction step uses dilute acid elution and water washing regeneration, which has a smaller environmental impact compared to the traditional precipitation method.

[0062] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0063] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0064] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A process for the synergistic extraction of lithium, potassium, and boron from salt lakes, characterized in that, include: After pretreatment, the raw brine from the salt lake is mixed with the primary extraction organic phase and subjected to multi-stage countercurrent extraction. Once the extraction is complete, the raffinate aqueous phase is obtained. A potassium precipitant is added to the raffinate aqueous phase to form potassium ions as precipitates, and then a boron- and potassium-poor lithium-rich brine is generated through solid-liquid separation. The boron- and potassium-poor lithium-rich brine is brought into contact with a lithium-ion sieve adsorbent, whereby lithium ions are adsorbed onto the adsorbent. The lithium ions are then eluted with an eluent to obtain a lithium-rich solution.

2. The method according to claim 1, characterized in that, The pretreatment of the raw brine from the salt lake is followed by mixing with the primary extraction organic phase for multi-stage countercurrent extraction. Upon completion of the extraction, the raffinate aqueous phase is obtained, comprising: The raw brine of the salt lake is filtered to remove suspended impurities, resulting in clarified brine. The pH value of the clarified brine is adjusted to an acidic range of 1.0-3.

0. The brine is then mixed with the primary extraction organic phase for multi-stage countercurrent extraction. After extraction, extract and raffinate are obtained. The primary extraction organic phase consists of an extractant, a co-extractant, and a diluent. The extractant is an alcohol or diol compound containing ortho-dihydroxyl groups, and the co-extractant B is a neutral phosphooxy compound. After extraction, a boron-loaded organic phase and a raffinate aqueous phase containing lithium and potassium are obtained. The boron-loaded organic phase is back-extracted with NaOH solution to obtain a sodium borate-enriched solution.

3. The method according to claim 2, characterized in that, The extractant is a higher fatty alcohol or polyol with a carbon chain length of C8-C12, and the volume percentage of the extractant in the primary extraction organic phase is 10%-30%. The co-extractant is tributyl phosphate, and the volume percentage of the co-extractant in the primary extraction organic phase is 5%-30%. The diluent is sulfonated kerosene.

4. The method according to claim 2 or 3, characterized in that, The process of adding a potassium precipitant to the raffinate aqueous phase to form a precipitate of potassium ions, followed by solid-liquid separation to generate a boron- and potassium-poor, lithium-rich brine, includes: The raffinate phase is indirectly heated using a plate heat exchanger or a tubular heat exchanger with hot water or steam to adjust its temperature to 15-35°C. An organophosphate potassium precipitant is then added to the raffinate phase after temperature adjustment. This precipitant selectively reacts with potassium ions in the raffinate phase to form a chelate precipitate. After separating the precipitated potassium, a boron- and potassium-poor lithium-rich brine and a potassium salt precipitate are generated. The organophosphate potassium precipitant is dipropylene glycol phenyl ether phosphate (DPPP) or tetraphenyl borate. The amount of organophosphate potassium precipitant added is 1.05-1.2 times the theoretically calculated molar amount of potassium ions.

5. The method according to claim 4, characterized in that, The method further includes: treating the potassium salt precipitate with dilute sulfuric acid to decompose it into potassium sulfate solution and regenerated DPPP precipitant; the potassium sulfate solution is evaporated, concentrated, crystallized, and dried to obtain potassium sulfate product; and the regenerated DPPP precipitant is treated and returned to the precipitation process for recycling.

6. The method according to claim 4, characterized in that, The process of contacting the boron- and potassium-poor lithium-rich brine with a lithium-ion sieve adsorbent to adsorb lithium ions onto the adsorbent, and then eluting the lithium ions with an eluent to obtain a lithium-rich solution includes: After adjusting the pH of the boron- and potassium-poor lithium-rich brine to 7.0-11.0, the brine is passed through an adsorption tower filled with a lithium-ion sieve adsorbent. The lithium-ion sieve adsorbent is a core-shell structured manganese-titanium composite lithium-ion sieve. This core-shell structured manganese-titanium composite lithium-ion sieve has a manganese-titanium lithium-ion sieve as the core and a high-molecular organic matter as the shell. The core layer is composed of manganese-titanium composite oxides and has a three-dimensional porous structure, providing lithium-ion intercalation sites to achieve selective adsorption of lithium. The shell layer is formed by in-situ cross-linking of hydrophilic polymers, and the thickness can be controlled between 10-100 nm. After the boron- and potassium-poor lithium-rich brine enters the adsorption tower, the lithium ions in the brine first pass through the hydrophilic polymer shell. The shell acts as a molecular sieve barrier, selectively allowing lithium ions to pass through. The lithium ions further diffuse to the manganese-titanium composite oxide core layer, where they are specifically adsorbed into the lattice channels of the core layer through ion exchange or intercalation mechanisms. The unadsorbed sodium, magnesium, and calcium ions flow out of the adsorption tower with the brine. After adsorption saturation, a 0.01-0.5 mol / L hydrochloric acid, sulfuric acid, or citric acid solution is used as the eluent to elute the lithium ions enriched on the core-shell structured manganese-titanium composite lithium ion sieve, resulting in a lithium-rich solution. The eluted core-shell structured manganese-titanium composite lithium ion sieve is washed with water until neutral and then used for the next round of lithium ion adsorption.

7. The method according to claim 1, characterized in that, The lithium ion sieve adsorbent is a manganese-based ion sieve, a titanium-based ion sieve, or a manganese-titanium composite ion sieve.

8. The method according to claim 6, characterized in that, The functionalized shell of the core-shell structured manganese-titanium composite lithium-ion sieve is a hydrophilic organic substrate, which includes one or more of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, cellulose acetate butyrate, and sodium carboxymethyl cellulose.

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