Method for pretreating salt lake brine

Abstract

The application provides a method for pretreatment of salt lake brine, and relates to the technical field of salt lake resource utilization, which comprises the following steps: sequentially adding the salt lake brine into an oxidizing agent, a modifier and an adsorption filter, respectively performing a first reaction, a second reaction and a third reaction, sequentially modifying, improving and adsorbing the salt lake brine, sequentially performing primary filtration and secondary filtration, completing the pretreatment of the salt lake brine, and obtaining purified brine. The method for pretreatment of salt lake brine can remove more than 99% of silt and suspended impurities, 30%-60% of organic matter and colloid, and 20%-60% of colority in the salt lake brine, purifies the salt lake brine, and is more conducive to the subsequent lithium extraction process. Moreover, the method has the characteristics of short process, high lithium yield, low investment and low operation cost, and achieves good economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of salt lake resource utilization technology, and in particular to a method for pretreatment of salt lake brine. Background Technology

[0002] Lithium, the lightest metal in nature, is a crucial energy metal widely used in glass, ceramics, electrolytic capacitors, and the nuclear industry. China's salt lake brines are rich in lithium resources, offering significant resource and cost advantages for lithium extraction. Currently, various lithium extraction technologies are being developed for salt lake brines, including solvent extraction, electrodialysis, electro-deintercalation / deintercalation, adsorption, and membrane extraction. While these methods effectively recover lithium resources from salt lake brines, they all require specific brine quality. For example, extraction methods are prone to failure due to impurities in the brine; electrodialysis and electro-deintercalation / deintercalation methods suffer from narrow flow channels, leading to membrane blockage, increased resistance, and decreased efficiency; adsorption methods often fail due to suspended solids and other impurities clogging the adsorbent pores, causing adsorbent poisoning. Membrane extraction technology is currently a crucial technology for lithium extraction and resource recovery from domestic salt lake brines, offering advantages such as good separation efficiency, high recovery rate, and low environmental cost. However, membrane-based lithium extraction technology is limited by membrane materials and has high requirements for influent water quality. Suspended solids, colloids, and organic matter are particularly prone to causing membrane fouling, resulting in drawbacks such as short lifespan and high process costs. As explained above, if the brine is not properly pretreated, it will severely restrict the application of the aforementioned methods in lithium extraction from salt lake brine, and will also hinder the development of lithium extraction technology from salt lake brine. Salt lake brine, as one of the sources of lithium resources in salt lake lithium extraction, has a complex water quality and must undergo pretreatment before entering the lithium extraction process to remove suspended solids, colloids, silt impurities, organic matter, etc.

[0003] The main methods for removing suspended solids and sludge from wastewater are natural sedimentation, or adding flocculants or coagulants to assist sedimentation followed by filtration. Natural sedimentation requires a large equipment footprint and is less effective, while adding chemicals to assist sedimentation requires a large amount of chemicals and results in a large amount of sludge. Methods for removing colloids from wastewater mainly include coagulation and ultrafiltration. However, the colloidal composition in salt lake brine is complex and has high viscosity, making traditional methods often ineffective and extremely prone to ultrafiltration membrane fouling. The main methods for removing organic matter from wastewater include traditional biochemical methods, advanced oxidation, and adsorption. Due to the high salinity of salt lake brine, biochemical methods are not suitable. Advanced oxidation methods, such as Fenton oxidation, require excessive reagents and stringent control conditions, which can easily introduce iron ion pollution. Other advanced oxidation methods, such as ozone, have relatively low efficiency due to the high salt ion effect of salt lake brine, and their degradation efficiency for organic matter is also low, requiring significant investment. Adsorption has been proven to be an effective method for removing organic matter, but it often exhibits selectivity in adsorption, working well for some low-molecular-weight, open-chain organic matter. For some large-molecular-weight organic matter, pre-oxidation modification is often required to achieve good results.

[0004] Currently, commonly used methods for pretreatment of salt lake brine mainly include dilution, media filtration, ultrafiltration, filtration devices, or combined processes. While dilution can reduce viscosity and increase the flux of subsequent filtration, it increases the amount of brine to be treated and dilutes the lithium in the brine without fundamentally removing impurities. Media filtration is prone to breakthrough, leading to water quality exceeding standards and affecting downstream processes, and requires periodic backwashing, resulting in lithium loss. Ultrafiltration and direct filtration devices are prone to clogging of filter membranes and filter cloths during purification and filtration due to the large amount of sludge, suspended particles, and colloids in the brine, resulting in insufficient permeate flow. Combined processes, such as coagulation pretreatment + multi-media filtration + ultrafiltration or coagulation + ultrafiltration, can remove impurities in salt lake brine to a certain extent, but the investment and operating costs are relatively high, and they lack specificity and are not economical.

[0005] For the reasons mentioned above, given the challenges of high salinity, high viscosity, low temperature, complex composition, and difficult filtration of salt lake brine, and the numerous pain points encountered by conventional methods, it is urgent to develop a pretreatment method for salt lake brine that simplifies the process and purifies the water quality of salt lake brine in a more economical way. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for pretreatment of salt lake brine. An oxidant, a modifier, and an adsorbent / filtering agent are sequentially added to the salt lake brine, and a first reaction, a second reaction, and a third reaction are carried out respectively, thereby sequentially modifying, improving, and adsorbing the brine. Then, primary and secondary filtration are performed sequentially to complete the pretreatment of the salt lake brine, resulting in purified brine. The salt lake brine pretreatment method of the present invention can remove more than 99% of silt and suspended solids, 30%–60% of organic matter and colloids, and 20%–60% of color from the salt lake brine, purifying the brine and making it more conducive to subsequent lithium extraction processes. Moreover, it features a short process, high lithium yield, and low investment and operating costs, achieving good economic and social benefits.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The purpose of this invention is to provide a method for pretreatment of salt lake brine, the method comprising the following steps:

[0009] Oxidizing agent, modifier and adsorption filter are added to the salt lake brine in sequence, and the first reaction, second reaction and third reaction are carried out respectively. Then, the brine is filtered in sequence through primary and secondary filtration to complete the pretreatment of the salt lake brine and obtain purified brine.

[0010] The pretreatment method for salt lake brine of this invention first involves adding an oxidant as the first agent to carry out a first reaction, modifying the organic matter in the salt lake brine by breaking down some large molecules and long-chain organic compounds into small molecules and short-chain organic compounds. Then, a modifier is added as the second agent to carry out a second reaction, utilizing adsorption and bridging principles, through flocculation and complexation, to remove or modify suspended solids and organic colloids in the salt lake brine, especially water-soluble, uncharged, and difficult-to-degrade large-molecule organic compounds, as precipitates. Subsequently, an adsorption filter is added as the third agent to carry out a third reaction, utilizing the adsorption effect of its abundant surface area to further adsorb the organic colloids and color from the salt lake brine modified by the first and second reactions, and also serving as the adsorption filter for subsequent primary filtration. The primary filtration mainly removes suspended solids from the salt lake brine, as well as suspended solids generated by the first, second, and third reactions. The secondary filtration mainly performs a second filtration on the filtrate obtained from the primary filtration, further improving the quality of the salt lake brine and obtaining purified brine.

[0011] As a preferred technical solution of the present invention, the salt lake brine includes any one of the following: raw brine, brine from the salt field process, or old brine.

[0012] Preferably, the brine water quality includes: turbidity of 5-500 NTU, suspended solids of 1-300 mg / L, viscosity of 1-10 mPa·s, TOC of 0.1-1.0 g / L, and color of 50-500.

[0013] Preferably, the purified brine has the following water quality characteristics: turbidity <10 NTU, viscosity of 1-6 mPa·s, TOC of 0.05-0.5 g / L, and color of 20-200.

[0014] Preferably, the brine is heated before the oxidant is added.

[0015] It is worth noting that heating the brine first to raise its temperature can reduce its viscosity, which is more conducive to the subsequent first, second and third reactions.

[0016] Preferably, the temperature of the heated brine is 5 to 60°C, such as 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] As a preferred embodiment of the present invention, the oxidant includes any one or a combination of at least two of sodium hypochlorite, hydrogen peroxide, ozone, or liquid chlorine.

[0018] Preferably, the amount of oxidant added is 0.001% to 0.1% of the mass of the salt lake brine, such as 0.001%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] As a preferred technical solution of the present invention, the mechanical stirring speed of the first reaction is 200 to 300 rpm, such as 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] Preferably, the reaction time of the first reaction is 0.5 to 1 hour, such as 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0021] As a preferred embodiment of the present invention, the modifier is composed of a high-performance multi-chain liquid resin.

[0022] Preferably, the amount of the modifier added is 0.05% to 0.5% of the mass of the salt lake brine, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] As a preferred technical solution of the present invention, the mechanical stirring speed of the second reaction is 100 to 200 rpm, such as 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm or 200 rpm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] Preferably, the reaction time of the second reaction is 0.5 to 1 hour, such as 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours or 1 hour, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] As a preferred technical solution of the present invention, the adsorption filter includes any one or a combination of at least two of the following: cationic surfactant, anionic surfactant, polyacrylamide, diatomaceous earth, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon, or acidic clay.

[0026] Preferably, the amount of the adsorbent filter added is 0.1% to 1.0% of the mass of the salt lake brine, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0027] As a preferred technical solution of the present invention, the mechanical stirring speed of the third reaction is 20 to 100 rpm, such as 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm or 100 rpm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0028] Preferably, the reaction time of the third reaction is 0.5 to 1 hour, such as 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0029] As a preferred technical solution of the present invention, the filtration device used in the primary filtration includes any one of titanium rod filter, self-cleaning filter, ceramic membrane filter, microporous filter, candlestick filter, filter bag filter, fiber filter, plate and frame filter press, rotary filter or sintered filter rod filter.

[0030] Preferably, the primary filtration device is equipped with water-top material and / or air-top material.

[0031] It is worth noting that the filtration device used in the primary filtration stage is equipped with functions such as water-top material and air-top material recovery of brine, which can achieve a lithium recovery rate of over 99% and easy cleaning of filter residue.

[0032] Preferably, the filtration pressure of the primary filter is 0.1 to 1.2 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, or 1.2 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the filtration accuracy of the primary filter is 10 to 200 μm, such as 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm or 200 μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] As a preferred technical solution of the present invention, the filtration device used in the secondary filtration includes any one of titanium rod filter, self-cleaning filter, ceramic membrane filter, microporous filter, candlestick filter, filter bag filter, fiber filter, plate and frame filter press, rotary filter or sintered filter rod filter.

[0035] Preferably, the secondary filtration device is equipped with water-top material and / or air-top material.

[0036] It is worth noting that the filtration device used in the secondary filtration is equipped with functions such as water-top material and air-top material recovery of brine, which can achieve a lithium recovery rate of over 99% and easy cleaning of filter residue.

[0037] Preferably, the filtration pressure of the secondary filter is 0.1 to 1.2 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, or 1.2 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0038] Preferably, the filtration accuracy of the secondary filter is 1 to 200 μm, such as 1 μm, 5 μm, 10 μm, 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm or 200 μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] It is worth noting that in the method described in this invention, both the primary filtration and the secondary filtration are equipped with backup devices. After the sludge discharge conditions are met, the sludge is replaced and the filtered salt sludge is discharged externally to settle in the salt field.

[0040] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0041] (1) The method for pretreatment of salt lake brine described in this invention can remove more than 99% of silt and suspended impurities, 30% to 60% of organic matter and colloids, and 20% to 60% of color from salt lake brine, thus purifying the salt lake brine. The lithium yield is greater than 99%, which is more conducive to the subsequent lithium extraction process.

[0042] (2) The method for pretreatment of salt lake brine described in this invention involves adding an oxidant, a modifier, and an adsorbent filter to the salt lake brine in sequence, and carrying out a first reaction, a second reaction, and a third reaction, respectively, to modify, improve, and adsorb the salt lake brine in sequence. Then, it is subjected to primary filtration and secondary filtration in sequence. While adsorbing and removing impurities such as organic matter and silt, the filtration performance of the salt lake brine is improved. The processing scale of the subsequent filtration unit can be reduced by more than 30%, reducing the one-time investment of the subsequent filtration unit and improving the stability of the subsequent treatment system.

[0043] (3) The method for pretreatment of salt lake brine described in this invention first undergoes primary filtration to complete initial filtration, and the filtrate obtained from primary filtration undergoes secondary filtration to complete fine filtration, thereby further improving the quality of salt lake brine. The filtrate obtained from secondary filtration is then introduced into a fine filtration tank to obtain purified brine.

[0044] (4) The method for pretreatment of salt lake brine described in this invention has a wide range of requirements for the influent of salt lake brine, strong applicability, and low loss of lithium. Compared with traditional pretreatment methods, it simplifies the process flow and has the characteristics of short process, high lithium yield, and low investment and operating costs, thus achieving good economic and social benefits. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of the salt lake brine pretreatment method described in this invention. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] This invention provides a method for pretreatment of salt lake brine, the process flow diagram of which is shown below. Figure 1 As shown, the method for pretreatment of salt lake brine includes the following:

[0048] The brine from the salt lake is heated to increase its temperature and reduce its viscosity. An oxidant is added as the first agent to initiate the first reaction, followed by a modifier as the second agent to initiate the second reaction. Then, an adsorbent filter is added as the third agent to initiate the third reaction. Finally, primary and secondary filtration are performed sequentially to complete the pretreatment of the brine. The filtrate obtained from the secondary filtration is then fed into a fine filtration tank to obtain purified brine. Both the primary and secondary filtration systems are equipped with backup devices to replace the sludge discharge devices once the sludge discharge conditions are met. The filtered salt sludge is discharged externally to settle in the salt field.

[0049] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0050] The salt lake brine used in the embodiments and comparative examples of this invention all come from brine of different properties from a salt lake in Qinghai Province;

[0051] The high-performance multi-chain liquid resins used in the embodiments and comparative examples of this invention are all commercially available products, specifically the terpene resin of model T-35.

[0052] Example 1

[0053] This embodiment provides a method for pretreatment of salt lake brine. The salt lake brine used in this embodiment comes from the brine after potassium extraction from a salt lake in Qinghai Province. The concentration of lithium ions in the salt lake brine is 0.05-4.5 g / L, the mass ratio of magnesium ions to lithium ions is 2500:1-20:1, and the concentration of boron ions is 0.05-5 g / L. The water quality of the salt lake brine includes: turbidity of 10-200 NTU, viscosity of 6-10 mPa·s, TOC of 0.1-1.0 g / L, and color of 50-500.

[0054] The method for pretreatment of salt lake brine includes the following:

[0055] The brine from the salt lake was heated to above 5°C. First, sodium hypochlorite was added at a mass percentage of 0.005% as an oxidant to initiate the first reaction. The mechanical stirring speed for the first reaction was controlled at 200 rpm, and the reaction time was 0.5 h. Then, high-performance multi-chain liquid resin was added at a mass percentage of 0.1% as a modifier to initiate the second reaction. The mechanical stirring speed for the second reaction was controlled at 200 rpm, and the reaction time was 0.5 h. Finally, cellulose was added at a mass percentage of 1% as an adsorption filter to initiate the third reaction. The mechanical stirring speed for the third reaction was controlled at 100 rpm, and the reaction time was 0. 5 hours; The salt lake brine, which has successively undergone modification, improvement, and adsorption filtration, undergoes primary filtration using a plate and frame filter press equipped with an air-supported feedstock; the filtration pressure of the primary filtration is 0.8 MPa; the filtration accuracy of the primary filtration is 25 μm; The filtrate obtained from the primary filtration undergoes secondary filtration using a microporous filter equipped with a water-supported feedstock; the filtration pressure of the secondary filtration is 0.2 MPa; the filtration accuracy of the secondary filtration is 1 μm; The filtrate obtained from the secondary filtration is then fed into a fine filtration tank to obtain purified brine.

[0056] The purified brine obtained by the salt lake brine pretreatment method described in Example 1 can be directly introduced into the membrane lithium extraction and separation stage.

[0057] Comparative Example 1

[0058] This comparative example provides a method for pretreatment of salt lake brine. Compared with Example 1, the only difference is that the salt lake brine is heated to above 5°C and directly subjected to primary and secondary filtration, while the first, second, and third reactions are omitted.

[0059] Table 1 summarizes the relevant water quality parameters of the purified brine obtained in Example 1 and Comparative Example 1, as well as the brine from the same salt lake in both examples.

[0060] Table 1

[0061]

[0062] Note: " / " indicates that it was not detected.

[0063] Example 2

[0064] This embodiment provides a method for pretreatment of salt lake brine. The salt lake brine used in this embodiment comes from lithium-containing brine from a salt lake in Qinghai Province. The concentration of lithium ions in the brine is 0.05-1.5 g / L, the mass ratio of magnesium ions to lithium ions is 200:1-150:1, and the concentration of boron ions is 0.05-1.5 g / L. The water quality of the salt lake brine includes: turbidity of 10-150 NTU, viscosity of 2-5 mPa·s, TOC of 0.1-0.5 g / L, and color of 100-300.

[0065] The method for pretreatment of salt lake brine includes the following:

[0066] The brine from the salt lake was heated to above 5°C. First, hydrogen peroxide was added at a mass percentage of 0.001% as an oxidant to initiate the first reaction. The mechanical stirring speed for the first reaction was controlled at 100 rpm, and the reaction time was 0.5 h. Then, high-performance multi-chain liquid resin was added at a mass percentage of 0.05% as a modifier to initiate the second reaction. The mechanical stirring speed for the second reaction was controlled at 100 rpm, and the reaction time was 0.5 h. Finally, sawdust was added at a mass percentage of 0.05% as an adsorption filter to initiate the third reaction. The mechanical stirring speed for the third reaction was controlled at 50 rpm, and the reaction time was 0. 5 hours; The salt lake brine, having undergone modification, improvement, and adsorption filtration in sequence, undergoes primary filtration using a plate and frame filter press equipped with an air-supported feedstock; the filtration pressure of the primary filtration is 0.8 MPa; the filtration accuracy of the primary filtration is 15 μm; The filtrate obtained from the primary filtration undergoes secondary filtration using a rotary disc filter equipped with a water-supported feedstock; the filtration pressure of the secondary filtration is 0.2 MPa; the filtration accuracy of the secondary filtration is 5 μm; The filtrate obtained from the secondary filtration is then fed into a fine filtration tank to obtain purified brine.

[0067] The purified brine obtained by the salt lake brine pretreatment method described in Example 2 can be directly introduced into the membrane lithium extraction and separation stage.

[0068] Comparative Example 2

[0069] This comparative example provides a method for pretreatment of salt lake brine. Compared with Example 2, the only difference is that the salt lake brine is heated to above 5°C and directly subjected to primary and secondary filtration, while the first, second, and third reactions are omitted.

[0070] Table 2 summarizes the relevant water quality parameters of the purified brine obtained in Example 2 and Comparative Example 2, as well as the salt lake brine obtained in both examples.

[0071] Table 2

[0072]

[0073] Note: " / " indicates that it was not detected.

[0074] As can be seen from Tables 1 and 2, the pretreatment methods corresponding to Example 1, Comparative Example 1, Example 2, and Comparative Example 2 all have good removal effects on suspended solids (turbidity), organic matter (TOC), and color in salt lake brine, and the yield of Li is similar; however, the purified brine obtained in Example 1 and Example 2 has a better removal effect on suspended solids (turbidity) and organic matter (TOC) than the comparative example, and the water flow rate of primary filtration and secondary filtration is higher. Analysis revealed that the main reason lies in the fact that in Examples 1 and 2, the addition of an oxidant for the first reaction better modifies the organic matter in the salt lake brine, forming low molecular weight organic matter. The addition of a modifier for the second reaction effectively adsorbs the modified organic matter formed in the first reaction and captures and removes the organic matter and suspended solids in the salt lake brine that were not modified by the first reaction. The addition of an adsorption filter for the third reaction not only allows for further deep adsorption but also enables faster filtration during primary filtration without clogging, thus ensuring filtration throughput. Moreover, primary filtration improves filtration accuracy, enhances the quality of the initial filtrate obtained from primary filtration, reduces the load on secondary filtration, and also improves the quality of the fine filtrate obtained from secondary filtration.

[0075] Comparative Example 3

[0076] This comparative example provides a method for pretreatment of salt lake brine, which differs from Example 1 only in that secondary filtration is completely omitted; the details are as follows:

[0077] The salt lake brine, which has undergone modification, improvement, and adsorption filtration in sequence, is subjected to primary filtration using a plate and frame filter press equipped with an air-supported feedstock. The filtration pressure of the primary filtration is 0.8 MPa, and the filtration accuracy is 25 μm. The filtrate obtained from the primary filtration is then fed into a fine filtration tank to obtain purified brine.

[0078] Comparative Example 3, by completely omitting secondary filtration, resulted in unstable turbidity of the filtrate. For example, if the filter cloth was damaged, the turbidity of the filtrate would increase significantly, even exceeding 10 NTU.

[0079] In summary, the pretreatment method for salt lake brine described in this invention improves upon the original pretreatment process to the greatest extent, maximizes the recycling and reuse of resources in salt lake brine, saves production costs for enterprises, brings additional benefits, enables clean production, and is simple, green and environmentally friendly, with good prospects for industrial application.

[0080] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0081] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0082] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0083] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for pretreatment of salt lake brine, characterized in that, The method for pretreatment of salt lake brine includes the following: Oxidizing agent, modifier and adsorption filter are added to the salt lake brine in sequence, and the first reaction, second reaction and third reaction are carried out respectively. Then, the brine is filtered in sequence through primary and secondary filtration to complete the pretreatment of the salt lake brine and obtain purified brine. The purified brine is used to extract lithium. The oxidant includes any one or a combination of at least two of sodium hypochlorite, ozone, or liquid chlorine. The amount of oxidant added is 0.001% to 0.1% of the mass of the salt lake brine; The modifier includes a high-performance multi-chain liquid resin. In the second reaction, based on the adsorption and bridging principle of the modifier, the suspended solids and organic colloidal substances in the salt lake brine are modified through flocculation and complexation.

2. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The salt lake brine includes any one of the following: raw brine, brine from the salt field process, or aged brine.

3. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The brine from the salt lake has the following water quality characteristics: turbidity of 5-500 NTU, suspended solids of 1-300 mg / L, and viscosity of 1-10 mPa. s, TOC is 0.1~1.0g / L, and chroma is 50~500.

4. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The purified brine has the following water quality characteristics: turbidity <10 NTU, viscosity 1~6 mPa. s, TOC is 0.05~0.5g / L, and chroma is 20~200.

5. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The brine in the salt lake is heated before the oxidant is added.

6. The method for pretreatment of salt lake brine according to claim 5, characterized in that, The temperature of the salt lake brine is controlled by heating at 5~60℃.

7. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The oxidant includes any one or a combination of at least two of sodium hypochlorite, hydrogen peroxide, ozone, or liquid chlorine.

8. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The mechanical stirring speed for the first reaction is 200-300 rpm.

9. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The reaction time for the first reaction is 0.5 to 1 hour.

10. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The modifier is composed of a high-performance multi-chain liquid resin; The amount of the modifier added is 0.05% to 0.5% of the mass of the salt lake brine.

11. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The mechanical stirring speed for the second reaction is 100~200 rpm.

12. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The reaction time for the second reaction is 0.5 to 1 hour.

13. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The adsorption filter includes any one or a combination of at least two of the following: cationic surfactants, anionic surfactants, polyacrylamide, diatomaceous earth, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon, or acid clay.

14. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The amount of the adsorption filter added is 0.1% to 1.0% of the mass of the salt lake brine.

15. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The mechanical stirring speed for the third reaction is 20-100 rpm.

16. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The reaction time for the third reaction is 0.5 to 1 hour.

17. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The primary filtration system employs any one of the following: titanium rod filter, self-cleaning filter, ceramic membrane filter, microporous filter, candlestick filter, filter bag filter, fiber filter, plate and frame filter press, rotary filter, or sintered filter rod filter.

18. The method for pretreatment of salt lake brine according to claim 17, characterized in that, The primary filtration system uses a filtration device equipped with water-top material and / or air-top material.

19. The method for pretreatment of salt lake brine according to claim 17, characterized in that, The filtration pressure of the primary filter is 0.1~1.2MPa.

20. The method for pretreatment of salt lake brine according to claim 17, characterized in that, The filtration accuracy of the primary filter is 10~200μm.

21. The method for pretreatment of salt lake brine according to claim 1, characterized in that, The secondary filtration uses any one of the following: titanium rod filter, self-cleaning filter, ceramic membrane filter, microporous filter, candlestick filter, filter bag filter, fiber filter, plate and frame filter press, rotary filter, or sintered filter rod filter.

22. The method for pretreatment of salt lake brine according to claim 21, characterized in that, The secondary filtration system uses a filtration device equipped with water-top material and / or air-top material.

23. The method for pretreatment of salt lake brine according to claim 21, characterized in that, The filtration pressure of the secondary filter is 0.1~1.2MPa.

24. The method for pretreatment of salt lake brine according to claim 21, characterized in that, The filtration accuracy of the secondary filter is 1~200μm.

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