Comprehensive recovery method of lithium extraction adsorbent washing liquid

Abstract

The invention discloses a comprehensive recovery method of lithium extraction adsorbent washing liquor, which belongs to the technical field of chemical waste liquor recovery, and comprises the following steps: carrying out primary reduced pressure distillation on the washing liquor in a distiller, separating a gas phase to be mixed steam of an organic solvent and water, and distilling a base solution to be mixed slurry of crystalline salt and a crude solvent, carrying out solid-liquid separation on the mixed slurry through a centrifugal machine to obtain crystalline salt and a crude solvent; separating the mixed steam through a supergravity bed, and condensing the separated steam to obtain condensed water; washing the crystallized salt to obtain salt washing liquid and washing salt; and carrying out secondary reduced pressure distillation on the crude solvent, and evaporating and condensing to obtain a refined solvent. The method can effectively recover the organic solvent, salt, water and other components of the washing liquid in the lithium extraction adsorbent, improves the resource utilization efficiency, reduces the production cost, and has good economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of chemical waste liquid recovery, and in particular to a comprehensive recovery method for lithium-extracting adsorbent washing liquid. Background Art

[0002] Lithium extraction adsorbent is a kind of composite material with lithium adsorbent powder as the matrix and high molecular polymer as the reinforcement. According to the type of powder, it can be divided into aluminum-based, manganese-based and titanium-based lithium adsorbents. Due to its excellent lithium adsorption, ion selectivity and cyclic stability, it can selectively separate lithium from complex lithium-containing brine systems. Therefore, it is widely used in the field of lithium extraction from salt lake brine.

[0003] In the process of preparing lithium-extraction adsorbents, organic solvents are usually used as co-solvents for polymers and water-soluble salts are used as porogens to increase the porosity of lithium-extraction adsorbents and improve adsorption performance. However, both organic solvents and porogens are regulating aids and do not enter the structure of the adsorbent. More than 95% of organic solvents and porogens need to be recycled.

[0004] Commonly used organic solvents include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), etc. These solvents have strong polarity and good compatibility with water. Commonly used salt porogens include lithium chloride, sodium chloride, potassium chloride, sodium sulfate, magnesium sulfate, etc. These salts have high solubility in water and can achieve the effect of water-soluble porogens. Usually, the organic solvents and salts in the lithium extraction adsorbent are washed and then comprehensively recovered. At present, there are many literatures on the preparation of lithium extraction adsorbents, and the methods are also more diverse, but very few involve the recovery method of the washing liquid. From the perspective of environmental protection and resource conservation, the recovery process is crucial.

[0005] For example, patent CN111215040B discloses a method for preparing a lithium extraction adsorbent using N,N-dimethylformamide as a solvent, wherein aluminum-based lithium adsorbent powder is kneaded evenly with a polymer and a solvent, extruded, crushed and screened to obtain a granular lithium adsorbent. In this method, only the crushed powder is subjected to secondary molding, and the solvent recovery is not considered. Patent CN116371384B discloses a method for preparing a hollow fiber titanium-based lithium ion sieve using DMAC as a solvent, which uses inner and outer layer synchronous spinning technology, sodium hydroxide as the core liquid, ammonium chloride and ammonium bicarbonate as salt pore-forming agents, which can significantly improve the porosity of the titanium-based lithium ion sieve and increase the adsorption capacity, but the method does not clearly describe how to handle the gel bath solution containing solvents and salts. Patent CN115487777B discloses a method for preparing a porous granular lithium adsorbent with high adsorption capacity. The method comprises the following steps: uniformly mixing lithium ion sieve powder with a polymer, a solvent, and a porogen in a certain mass ratio, and then subjecting the mixture to extrusion spinning, aqueous solidification and washing to wash out the residual solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone in the lithium extracting adsorbent, and porogens such as lithium chloride, sodium chloride, and potassium chloride, thereby preparing a porous lithium adsorbent with high adsorption capacity. However, the method does not disclose how to recover the components from the washing liquid.

[0006] Therefore, providing a comprehensive recovery method for lithium extraction adsorbent washing liquid with obvious effectiveness is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0007] In view of this, the present invention provides a comprehensive recovery method for lithium extraction adsorbent washing liquid, which adopts a recovery method mainly based on reduced pressure distillation to comprehensively recover the solvent, salt and water in the washing liquid. The recovered components can be returned to the lithium extraction adsorbent preparation process for reuse, which effectively improves the resource utilization efficiency, reduces the production cost, and realizes the long-term stable operation of the lithium extraction adsorbent manufacturing process.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] A comprehensive recovery method for lithium-extracting adsorbent washing liquid comprises the following steps:

[0010] (1) Primary vacuum distillation: The washing liquid is subjected to primary vacuum distillation in a distiller, the separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of a crystal salt and a crude solvent. The mixed slurry is separated into solid and liquid by a centrifuge to obtain a crystal salt and a crude solvent;

[0011] (2) Supergravity separation: The mixed steam is separated by a supergravity bed, and the separated liquid is refluxed into a primary vacuum distiller, where the separated steam is condensed to obtain condensed water;

[0012] (3) washing: washing the crystallized salt to obtain a washing solution and washing salt, the washing solution is returned to step (1) and combined with the washing solution, and the washing salt is dried and crushed to obtain refined salt;

[0013] (4) Secondary vacuum distillation: The crude solvent is subjected to secondary vacuum distillation to obtain a refined solvent by evaporation and condensation.

[0014] Furthermore, the composition of the washing liquid includes the following raw materials in mass percentage: 10% to 30% organic solvent, 5% to 20% salt, and 50% to 85% water.

[0015] Furthermore, the organic solvent contained in the washing liquid is any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0016] The crystalline salt contained in the washing solution is any one of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium chloride, sodium sulfate, potassium sulfate, magnesium sulfate, ammonium carbonate and ammonium bicarbonate.

[0017] Furthermore, the vacuum degree of the first-stage reduced pressure distillation in step (1) is 0.05-0.10 MPa, and the distillation temperature is 50-100°C.

[0018] Furthermore, the supergravity bed in step (2) is an enhanced gas-liquid separation device, and the supergravity bed is mainly composed of a rotor, a filler, a liquid distributor, a transmission shaft, etc.;

[0019] The rotor speed of ultra-gravity separation is 500-1000 rpm, the kettle top temperature is 50-100°C, and the reflux ratio is 0.1-3.0.

[0020] Furthermore, the washing in step (3) is a multi-stage countercurrent washing, the washing time is 5 to 60 minutes, the number of washings is 2 to 5 times, the washing solid-liquid ratio is 1:0.5 to 3, and the washing temperature is 5 to 80°C.

[0021] Furthermore, the washing liquid used in step (3) is any one of condensed water, ultrapure water, and RO water.

[0022] Furthermore, the vacuum degree of the secondary reduced pressure distillation process in step (4) is 0.05-0.10 MPa, and the distillation temperature is 100-200°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention directly separates the solvent, salt and water in the washing liquid by vacuum distillation. First, the water is converted into a gas phase by evaporation. As the water content decreases, the solubility of the salt in the washing liquid is greatly reduced and converted into a solid crystalline salt. The remaining liquid phase is the recovered solvent, thereby achieving gas-liquid-solid three-phase separation.

[0025] (2) The present invention forms a supergravity field by rotating the rotor with packing at high speed, thereby improving the gas-liquid separation efficiency and reducing the height of the mass transfer unit. Compared with the traditional packed tower, the equipment volume is reduced by more than 10 times, and the equipment investment is significantly reduced.

[0026] (3) The present invention adopts a multi-stage countercurrent washing process to wash the crystallized salt, which can recover most of the entrained solvent and improve the purity of the crystallized salt. Compared with the ordinary washing process, the water consumption is reduced by more than 50%, and the crystallized salt washing yield is increased from 50% to more than 80%.

[0027] (4) The method of the present invention realizes the complete recovery of the solvent, salt, water and other components in the washing liquid, with a recovery rate of more than 95%, and each component can be continuously reused in the preparation process of the lithium extraction adsorbent, thus realizing a closed-loop cycle of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The process flow chart of the comprehensive recovery method of lithium-extracting adsorbent washing liquid of the present invention is DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A comprehensive recovery method for lithium-extracting adsorbent washing liquid:

[0032] (1) Primary vacuum distillation: The aluminum-based lithium adsorbent is subjected to multi-stage countercurrent washing and filtration separation to obtain a clear washing liquid, the composition of which is determined to be: DMF solvent accounts for 15.70%, NaCl salt accounts for 12.14%, and water accounts for 72.16%;

[0033] 50 kg of washing liquid is subjected to primary reduced pressure distillation in a distiller at a vacuum degree of 0.07 MPa and a temperature of 70°C, the separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of crystalline salt and a crude solvent, and the mixed slurry is subjected to solid-liquid separation by a centrifuge to obtain crystalline salt and a crude solvent;

[0034] (2) Supergravity separation: The mixed steam is separated by a supergravity bed, the rotor speed is set to 800 rpm, the kettle top temperature is 55° C., the reflux ratio is 1.5, the separated liquid is refluxed to the primary vacuum distiller, and the separated steam is condensed to obtain condensed water;

[0035] (3) Washing: The crystallized salt is subjected to multi-stage countercurrent washing with condensed water to obtain a washing solution and washing salt, the washing time is set to 20 min, the number of washings is set to 4 times, the washing solid-liquid ratio is set to 1:0.5, and the washing temperature is set to 30° C. The washing solution is returned to step (1) and combined with the washing solution for treatment, and the washing salt is dried and crushed to obtain refined salt;

[0036] (4) Secondary vacuum distillation: The crude solvent was subjected to secondary vacuum distillation at a vacuum degree of 0.07 MPa and a temperature of 110°C to obtain a DMF refined solvent by evaporation and condensation.

[0037] By comprehensively recovering the washing liquid, 35.40 kg of condensed water, 5.88 kg of refined NaCl salt and 7.60 kg of refined DMF solvent were collected. After calculation, the recovery rates of water, refined NaCl salt and refined DMF solvent were 98.12%, 96.87% and 96.82% respectively.

[0038] Example 2

[0039] A comprehensive recovery method for lithium-extracting adsorbent washing liquid:

[0040] (1) Primary vacuum distillation: The aluminum-based lithium adsorbent is subjected to multi-stage countercurrent washing and filtration separation to obtain a clear washing liquid, and its components are determined as follows: DMAC solvent accounts for 18.90%, NaCl salt accounts for 16.25%, and water accounts for 64.85%;

[0041] 50 kg of washing liquid is subjected to primary reduced pressure distillation in a distiller at a vacuum degree of 0.07 MPa and a temperature of 70°C, the separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of crystalline salt and a crude solvent, and the mixed slurry is subjected to solid-liquid separation by a centrifuge to obtain crystalline salt and a crude solvent;

[0042] (2) Supergravity separation: The mixed steam is separated by a supergravity bed, the rotor speed is set to 800 rpm, the kettle top temperature is 58° C., the reflux ratio is 1.2, the separated liquid is refluxed to the primary vacuum distiller, and the separated steam is condensed to obtain condensed water;

[0043] (3) Washing: The crystallized salt is subjected to multi-stage countercurrent washing with condensed water to obtain a washing solution and washing salt, the washing time is set to 20 min, the number of washings is set to 4 times, the washing solid-liquid ratio is set to 1:0.5, and the washing temperature is set to 30° C. The washing solution is returned to step (1) and combined with the washing solution for treatment, and the washing salt is dried and crushed to obtain refined salt;

[0044] (4) Secondary vacuum distillation: The crude solvent is subjected to secondary vacuum distillation at a vacuum degree of 0.07 MPa and a temperature of 118°C to obtain a refined solvent by evaporation and condensation.

[0045] By comprehensively recovering the washing liquid, 31.60 kg of condensed water, 7.82 kg of refined NaCl salt and 9.12 kg of refined DMAC solvent were collected. After calculation, the recovery rates of water, refined NaCl salt and refined DMAC solvent were 97.46%, 96.25% and 96.51%, respectively.

[0046] Example 3

[0047] A comprehensive recovery method for lithium-extracting adsorbent washing liquid:

[0048] (1) Primary vacuum distillation: The manganese-based lithium adsorbent is subjected to multi-stage countercurrent washing and filtration separation to obtain a clear washing liquid, and its components are determined as follows: NMP solvent accounts for 21.50%, Na2SO4 salt accounts for 8.87%, and water accounts for 69.63%;

[0049] 30 kg of washing liquid is subjected to primary reduced pressure distillation in a distiller at a vacuum degree of 0.07 MPa and a temperature of 100° C., the separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of crystalline salt and a crude solvent. The mixed slurry is subjected to solid-liquid separation by a centrifuge to obtain crystalline salt and a crude solvent;

[0050] (2) Supergravity separation: The mixed steam is separated by a supergravity bed, the rotor speed is set to 1000 rpm, the kettle top temperature is 65° C., the reflux ratio is 1.0, the separated liquid is refluxed to the primary vacuum distiller, and the separated steam is condensed to obtain condensed water;

[0051] (3) Washing: The crystallized salt is subjected to multi-stage countercurrent washing with ultrapure water to obtain a washing solution and washing salt, the washing time is set to 10 min, the number of washings is set to 3 times, the washing solid-liquid ratio is set to 1:1, and the washing temperature is set to 20° C. The washing solution is returned to step (1) and combined with the washing solution for treatment, and the washing salt is dried and crushed to obtain refined salt;

[0052] (4) Secondary vacuum distillation: The crude solvent is subjected to secondary vacuum distillation at a vacuum degree of 0.07 MPa and a temperature of 140°C to obtain a refined solvent by evaporation and condensation.

[0053] By comprehensively recovering the washing liquid, 17.59 kg of condensed water, 2.57 kg of Na2SO4 crystal salt and 6.30 kg of refined NMP solvent were collected. After calculation, the recovery rates of water, Na2SO4 crystal salt and refined NMP solvent were 84.21%, 96.58% and 97.67%, respectively.

[0054] Example 4

[0055] A comprehensive recovery method for lithium-extracting adsorbent washing liquid:

[0056] (1) Primary vacuum distillation: The titanium-based lithium adsorbent is subjected to multi-stage countercurrent washing and filtration separation to obtain a clear washing liquid, the components of which are determined as follows: DMSO solvent accounts for 25.47%, MgSO4 salt accounts for 6.15%, and water accounts for 68.38%;

[0057] 80 kg of washing liquid is subjected to primary reduced pressure distillation in a distiller at a vacuum degree of 0.07 MPa and a temperature of 90° C. The separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of crystalline salt and a crude solvent. The mixed slurry is subjected to solid-liquid separation by a centrifuge to obtain crystalline salt and a crude solvent;

[0058] (2) Supergravity separation: The mixed steam is separated by a supergravity bed, the rotor speed is set to 900 rpm, the kettle top temperature is 65° C., the reflux ratio is 1.2, the separated liquid is refluxed to the primary vacuum distiller, and the separated steam is condensed to obtain condensed water;

[0059] (3) Washing: The crystallized salt is subjected to multi-stage countercurrent washing with RO water to obtain a washing solution and washing salt, the washing time is set to 15 min, the number of washings is set to 3 times, the washing solid-liquid ratio is set to 1:1, and the washing temperature is set to 20° C. The washing solution is returned to step (1) and combined with the washing solution for treatment, and the washing salt is dried and crushed to obtain refined salt;

[0060] (4) Secondary vacuum distillation: The crude solvent is subjected to secondary vacuum distillation at a vacuum degree of 0.07 MPa and a temperature of 130°C to obtain a refined solvent by evaporation and condensation.

[0061] By comprehensively recovering the washing liquid, 49.92 kg of condensed water, 4.75 kg of MgSO4 crystal salt, and 19.92 kg of refined NMP solvent were collected. After calculation, the recovery rates of water, MgSO4 crystal salt, and refined NMP solvent were 91.25%, 96.54%, and 97.76%, respectively.

[0062] Test Example 1

[0063] The recovered solvent, crystalline salt and condensed water involved in Examples 1-4 were analyzed and tested using a high performance gas chromatograph (Agilent 7890A-5975C), an inductively coupled plasma emission spectrometer (Agilent 5800ICP-OES), a trace moisture analyzer (WS-3000), and a total organic carbon analyzer (SHIMADZU TOC-4200). The test results are as follows:

[0064] By comprehensively recovering the washing liquid in the lithium extraction adsorbent, the purity of the recovered solvents DMF, DMAC, NMP and DMSO is greater than 99.50%, which can meet the use requirements of industrial solvents such as standards HG / T 2028-2009, HG / T4470-2012, GB / T 27563-2011, GB / T21395-2024, etc. The purity of NaCl, Na2SO4, and MgSO4 crystal salts is greater than 95%, and they can be returned to the lithium extraction adsorbent preparation system for reuse after drying and crushing. The total organic carbon (TOC) concentration in the condensed water is less than 200 mg / L, which can meet the inorganic chemical industry pollutant emission standards (GB 31573-2015), and the condensed water can also be returned to the washing section to improve resource utilization efficiency.

[0065] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A comprehensive recovery method for lithium-extracting adsorbent washing liquid, characterized in that: The following steps are involved: (1) Primary vacuum distillation: The washing liquid is subjected to primary vacuum distillation in a distiller, the separated gas phase is a mixed vapor of an organic solvent and water, and the distillation bottom liquid is a mixed slurry of a crystal salt and a crude solvent. The mixed slurry is separated into solid and liquid by a centrifuge to obtain a crystal salt and a crude solvent; (2) Supergravity separation: The mixed steam is separated by a supergravity bed, and the separated liquid is refluxed into a primary vacuum distiller, where the separated steam is condensed to obtain condensed water; (3) washing: washing the crystallized salt to obtain a washing solution and washing salt, the washing solution is returned to step (1) and combined with the washing solution, and the washing salt is dried and crushed to obtain refined salt; (4) Secondary vacuum distillation: The crude solvent is subjected to secondary vacuum distillation to obtain a refined solvent by evaporation and condensation.

2. A comprehensive recovery method for lithium-extracting adsorbent washing liquid according to claim 1, characterized in that: The vacuum degree of the first-stage reduced pressure distillation in step (1) is 0.05-0.10 MPa, and the distillation temperature is 50-100°C.

3. A comprehensive recovery method for lithium-extracting adsorbent washing liquid according to claim 1, characterized in that: The ultra-gravity bed in step (2) is an enhanced gas-liquid separation device, the rotor speed of the ultra-gravity separation is 500-1000 rpm, the kettle top temperature is 50-100° C., and the reflux ratio is 0.1-3.

0.

4. A comprehensive recovery method for lithium-extracting adsorbent washing liquid according to claim 1, characterized in that: The washing in step (3) is a multi-stage countercurrent washing, the washing time is 5 to 60 minutes, the washing times are 2 to 5 times, the washing solid-liquid ratio is 1:0.5 to 3, and the washing temperature is 5 to 80°C.

5. The comprehensive recovery method of a lithium-extracting adsorbent washing liquid according to claim 1, characterized in that: The washing liquid used in the washing in step (3) is any one of condensed water, ultrapure water, and RO water.

6. A comprehensive recovery method for lithium-extracting adsorbent washing liquid according to claim 1, characterized in that: The vacuum degree of the secondary reduced pressure distillation process in step (4) is 0.05-0.10 MPa, and the distillation temperature is 100-200°C.

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