High-value recovery method for magnesium ions in salt lake and product prepared by high-value recovery method

Abstract

The invention discloses a high-value recovery method for magnesium ions in a salt lake and a product prepared through the high-value recovery method, and belongs to the technical field of hydrometallurgy. The method comprises the following steps: carrying out neutralization reaction on salt lake brine by using slurry subjected to CaO digestion treatment, and filtering and washing after the reaction to obtain Mg (OH) 2 and neutralized filtrate; carrying out dehydration treatment on Mg (OH) 2, and roasting after dehydration treatment to obtain an active MgO product; carrying out evaporative crystallization and dehydration treatment on the neutralized filtrate to obtain anhydrous calcium chloride; and pelletizing and activating the anhydrous calcium chloride to obtain the CaCl2 desiccant product. According to the method, the active MgO product is prepared, efficient and high-value recovery of magnesium ions is achieved, the byproduct CaCl2 drying agent is obtained, and salt lake resources are utilized to the maximum extent.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydrometallurgy, in particular to a high-value recovery method of magnesium ions in a salt lake and a product prepared by the method. BACKGROUND

[0002] Magnesium, as a key non-ferrous metal material, plays an irreplaceable role in many fields due to its excellent lightweight and high-strength characteristics. It can combine with other metal elements to form alloys with excellent performance, widely used in aviation, automobile, electronics and communication industries. In the aerospace field, magnesium alloys, with their low density and high specific strength, have become the preferred material for manufacturing aircraft structural parts and spacecraft components, and their consumption far exceeds other metals. The application of magnesium alloys in the automobile industry is continuously expanding, from engine parts to transmission housings, to vehicle body structural parts. The application of magnesium alloys not only improves the performance of automobiles, but also meets the needs of lightweight and energy saving and emission reduction. With the continuous development of the automobile industry, the demand for magnesium is expected to further increase, and its importance in modern industry is self-evident.

[0003] In the production of potassium fertilizer in Qinghai, about 8-10 tons of magnesium chloride will be produced as a byproduct for every ton of potassium chloride produced. With the continuous expansion of the production scale of potassium fertilizer, the amount of old magnesium chloride brine produced is also increasing. At present, the unused old magnesium chloride brine has reached hundreds of thousands of tons per year. If these large amounts of old magnesium chloride brine are directly discharged, not only will it cause a huge waste of resources, but also will have an adverse impact on the environment.

[0004] Therefore, developing magnesium resources in the old brine of Qinghai salt lake brine potassium extraction and producing magnesium products can not only bring significant economic benefits, but also effectively control the harm and pollution caused by magnesium chloride wastewater.

[0005] Magnesium chloride wastewater can be treated by evaporation crystallization, ion exchange technology, membrane separation technology, chemical precipitation method, etc. to realize the recovery of magnesium chloride and the discharge of wastewater up to standard. Among them, the evaporation crystallization technology treats magnesium-containing wastewater and obtains magnesium chloride hexahydrate. Due to the high evaporation concentration temperature and the strong corrosion of magnesium chloride, the equipment material needs to choose expensive titanium material and other materials, and the evaporation combined with cooling crystallization technology has high operation cost, high operation difficulty and small application range. Ion exchange technology can adsorb magnesium ions in wastewater through ion exchange resin. This technology can recover valuable metal magnesium, but the exchange resin needs to be regenerated and replaced regularly, the process is relatively complex, and the cost is high. Membrane separation technology can separate magnesium ions in wastewater through a semi-permeable membrane, but the membrane is easily contaminated, affecting the separation effect, and the cleaning and replacement of the membrane will increase the cost.

[0006] The current widely used magnesium chloride wastewater treatment method is chemical precipitation method. The chemical precipitation method is to add a precipitant to make ions in the wastewater form a precipitate, so as to realize separation. The method is simple to operate, does not need complex equipment, and has a wide application range. However, the present inventors find that the prior art can only prepare magnesium hydroxide by using the chemical precipitation method to recover magnesium resources from salt lake brine, and ions in the remaining solution are not recovered, so zero emission cannot be achieved. SUMMARY

[0007] According to one embodiment of the present application, the purpose is to provide a high-value recovery method of magnesium ions in salt lake and a product prepared by the method. The method includes neutralizing salt lake brine by using slurry after lime digestion, and then treating the neutralized residue and the neutralized filtrate respectively. After the treatment, active magnesium oxide is obtained, the high-value recovery of magnesium ions is realized, the added value of magnesium ions in salt lake brine is significantly improved, and in addition, a by-product CaCl2 drying agent is obtained, and the utilization value of salt lake brine is improved.

[0008] The above purpose can be achieved by the following technical solutions: According to one aspect of the present application, the present application provides a high-value recovery method of magnesium ions in salt lake, comprising: neutralizing the salt lake brine by using slurry after CaO digestion treatment, filtering and washing after the reaction to obtain Mg(OH)2 and a neutralized filtrate; dehydration treating the Mg(OH)2, and roasting after the dehydration treatment to obtain an active MgO product; evaporating and crystallizing the neutralized filtrate, and dehydration treating to obtain anhydrous calcium chloride; and activating the anhydrous calcium chloride to obtain a CaCl2 drying agent product.

[0009] Optionally, the salt lake brine is a chloride type, and the concentration of Mg ions is 15-30 g / L.

[0010] Optionally, the preparation method of the slurry after CaO digestion treatment is to add lime into a digestion medium solution for digestion treatment for 1-4 h to prepare the slurry. The concentration of the slurry is 5-30 wt%. Further, the digestion medium solution is tap water or water produced in the process of evaporative crystallization and dehydration treatment.

[0011] Optionally, the temperature of the neutralization reaction is 20-50℃, and the time is 2-4 h.

[0012] Optionally, in the step of dehydration treating the Mg(OH)2 and roasting after the dehydration treatment, the dehydration treatment temperature is 90-150℃, the dehydration treatment time is 1-3 h, the roasting temperature is 500-800℃, and the roasting time is 1-4 h.

[0013] Optionally, the active MgO is used as a precipitant in a nickel-cobalt precipitation reaction, wherein the concentration of nickel-cobalt in the precipitated nickel-cobalt filtrate is: Ni: 0.5-30 g / L, Co: 0.5-10 g / L.

[0014] Optionally, the neutralized filtrate is subjected to evaporation crystallization, and in the dehydration treatment step, the evaporation crystallization temperature is 50-70°C, the time is 2-4 h, and the pressure is normal pressure or negative pressure; the dehydration treatment temperature is 200-300°C, and the time is 2-4 h.

[0015] Optionally, in the step of activating the anhydrous calcium chloride pellets, the anhydrous calcium chloride is mixed with a binder at a mass ratio of 5-10:1 to form pellets, and the pellets are activated at 150-200°C for 1-3 h.

[0016] Optionally, the binder is one or more of hydroxypropyl methylcellulose, polyvinyl alcohol, and starch solution.

[0017] Optionally, the method further comprises: reusing the water produced after the evaporation crystallization and dehydration treatment of the neutralized filtrate in the neutralization reaction process.

[0018] According to one aspect of the present application, the present application provides an active MgO product prepared by a high-value recovery method of magnesium ions in salt lake.

[0019] Optionally, the active MgO product has a purity of >90 wt.% and an iodine absorption value of >130 mg / g.

[0020] According to one aspect of the present application, the present application provides a CaCl2 desiccant product prepared by a high-value recovery method of magnesium ions in salt lake.

[0021] Optionally, the CaCl2 desiccant product has a moisture absorption rate of >200%.

[0022] Beneficial effects: According to one embodiment of the present application, salt lake brine is used as raw material, and then the neutralized slag and the neutralized filtrate are treated respectively to obtain active magnesium oxide and CaCl2 desiccant. The present application maximizes the development of magnesium ions in salt lake brine, and no waste gas, waste liquid, and waste slag are generated during the preparation process. The product has high purity, high added value, and is accompanied by byproduct production. The production cycle is short, and the utilization value of salt lake brine is improved. Efficient preparation and recovery of magnesium hydroxide and calcium chloride are achieved, and zero discharge of magnesium chloride wastewater is achieved.

[0023] Compared with the prior art, the present application also has the following advantages: 1) Based on Mg(OH)2 obtained after neutralization reaction, using dehydration + calcination process, and optimizing the process conditions, active magnesium oxide is prepared. The active magnesium oxide produced by this process significantly improves the added value of magnesium ions in salt lake brine, is simple to operate and has low cost.

[0024] 2) Based on the filtrate obtained after neutralization treatment of the slaked lime, using evaporation crystallization + dehydration treatment + ball activation process, and optimizing the process conditions, a spherical calcium chloride desiccant with uniform filling, low dust generation and high moisture absorption capacity is prepared. This process converts low-cost lime into high-value spherical desiccant, significantly improving the added value of calcium chloride and improving the economic and social benefits of salt lake brine.

[0025] 3) The overall process flow is short, the production efficiency is high, the energy consumption is low, no waste liquid and waste residue are produced, and the environment is not polluted. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the process flow chart of the method for high-value recovery of magnesium ions in salt lake in an embodiment of the present application. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described in detail below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. The description of the at least one exemplary embodiment is actually only illustrative, not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0028] As mentioned earlier, the present inventors realize that the chemical precipitation method for recovering magnesium resources in salt lake brine in the prior art is limited to the preparation of magnesium hydroxide / alkali magnesium carbonate, and the ions in the remaining solution are not recovered, which cannot achieve zero emission. In addition, the present inventors have also noticed that the related technologies for recovering magnesium resources in salt lake brine at present mainly focus on improving and improving the purity of magnesium products, and no related reports on improving and improving the activity of magnesium products have been found.

[0029] Based on the above understanding and discovery, the inventors of the present application still take high-value recovery of magnesium ions as the main line, and ingeniously use the combination of chloride ions in salt lake and calcium ions in CaO to obtain CaCl2, and then obtain the by-product desiccant through dehydration crystallization and activation technology. In addition, by adopting a specific process and improving the process conditions, active magnesium oxide is obtained, the product activity is improved, and the high-activity magnesium product has a wider application scenario, such as being used as a nickel-cobalt precipitant, etc., so that the resources in salt lake brine are maximized, and the economic and social benefits are significantly improved.

[0030] The method for high-value recovery of magnesium ions in salt lake provided in an embodiment of the present application is to take salt lake brine as raw material, and then to treat the slurry after lime digestion through neutralization, and then to treat the neutralization residue and the neutralization filtrate respectively. In the method, the active magnesium oxide is prepared from the Mg(OH)2 in the neutralization residue through dehydration + calcination process, and the CaCl2 desiccant is prepared from the neutralization filtrate through evaporation crystallization + dehydration treatment + balling activation combined process. The method maximizes the development of magnesium ions in salt lake brine, and no waste gas, waste liquid or waste residue is generated in the preparation process. The product has high activity, high purity, high added value, and is accompanied by by-product output, and has a short production cycle, thereby improving the utilization value of salt lake brine.

[0031] In some embodiments of the present application, the method for high-value recovery of magnesium ions in salt lake specifically comprises the following steps: (1) neutralizing reaction of salt lake brine by using slurry after CaO digestion treatment, and then filtering and washing after reaction to obtain Mg(OH)2 and neutralization filtrate; (2) dehydration treatment of Mg(OH)2, and then calcination after dehydration treatment to obtain active MgO product; (3) evaporation crystallization and dehydration treatment of the neutralization filtrate to obtain anhydrous calcium chloride; (4) balling activation of the anhydrous calcium chloride to obtain CaCl2 desiccant product.

[0032] In the above embodiments of the present application, the salt lake brine to be treated is a chloride type, and the Mg ion concentration is 15-30 g / L. Through the above steps, the magnesium ions in the salt lake brine are maximally developed, and the active MgO product is prepared, thereby improving the utilization value of salt lake brine.

[0033] In the present application, the slurry after CaO digestion treatment is neutralized with salt lake brine. Further preferably, the concentration of the slurry after CaO digestion treatment is 5-30 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, etc. Based on the above slurry, the neutralization reaction of salt lake brine is carried out, and the obtained Mg(OH)2 has less impurities, which creates favorable conditions for the subsequent preparation of active magnesium oxide and reduces the influence on the activity of magnesium oxide.

[0034] In some preferred embodiments, in step (1), the temperature of the neutralization reaction is 20-50℃, such as 20℃, 30℃, 40℃, 50℃, etc., and the time is 2-4h. By controlling the temperature and time of the neutralization reaction, the reaction progress can be controlled, and the impurities in the neutralization residue Mg(OH)2 can be further reduced, and the purity is correspondingly improved; more importantly, by controlling the temperature and time of the neutralization reaction, the nucleation process of Mg(OH)2 can be controlled, and then the activity of MgO can be improved in the dehydration and calcination stage.

[0035] In some alternative embodiments, the CaO slurry after digestion treatment is prepared by the following method, which comprises: adding quicklime into a digestion medium solution for digestion treatment for 1-4h, such as 1h, 2h, 3h, 4h, 5h, etc., to prepare a slurry with a concentration of 5-30wt%, and based on the slurry, the salt lake brine is neutralized to obtain a neutralization residue with low impurity content. The digestion medium solution is tap water or water produced in the evaporation crystallization and dehydration treatment process.

[0036] In this application, after the neutralization reaction of the digestion CaO slurry and the salt lake brine, the obtained neutralization residue Mg(OH)2 and the neutralization filtrate are further treated respectively, not only active magnesium oxide is obtained, the high-value recovery of magnesium ions is realized, but also the low-cost quicklime is converted into high-value spherical dry agent, the various ions in the salt lake brine are fully recovered, the zero discharge of magnesium chloride wastewater is realized, and the economic and social benefits of the salt lake brine process are significantly improved. In addition, the active magnesium oxide obtained based on the specific treatment method has the characteristics of high activity, and based on this, the high-activity active magnesium oxide can be directly used as a precipitant in the nickel-cobalt precipitation reaction in the nickel-cobalt solution to improve the nickel-cobalt precipitation efficiency and the grade of Ni in the product.

[0037] In order to obtain active magnesium oxide products, the inventors of the present application have also further researched and improved the process and its conditions for preparing active magnesium oxide from the neutralization residue Mg(OH)2 obtained in step (1). The application innovatively uses a dehydration + calcination treatment process to convert Mg(OH)2 after neutralization reaction into high-value active MgO products, which significantly improves the added value of magnesium ions in salt lake brine, and the operation is simple and the cost is low.

[0038] In order to obtain a more active magnesium oxide product, in some preferred embodiments, when the neutralized residue Mg(OH)2 is treated by a dehydration and calcination process, the dehydration treatment temperature is controlled to be 90-150°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., the dehydration treatment time is controlled to be 1-3h, such as 1h, 2h, 3h, etc.; further, the calcination temperature is controlled to be 500-800°C, such as 500°C, 600°C, 700°C, 800°C, etc., and the calcination time is controlled to be 1-4h, such as 1h, 2h, 3h, 4h, etc. Based on the dehydration + calcination process, by further optimizing the dehydration and calcination temperature and time, the product activity and structure are controlled, the generation of side reactions and impurities is avoided, the MgO grain over-burning, local overheating densification and other phenomena are avoided, which is more conducive to the formation of fine MgO grains and rich pore structure, the activity of the MgO product is improved, and thus a high-activity product is obtained, in addition, the product also has high purity. The dehydration + calcination process and conditions of the "high-activity product" in the above preferred embodiments are completely different from the process and conditions of the "high-purity MgO product", the present inventors have also noticed that if the dehydration + calcination process is not used, or the process conditions are not within the above range, the activity of the MgO product will be affected, and thus the recovery value of the magnesium ions in the salt lake brine will be reduced.

[0039] Further, by using the dehydration + calcination process, the active MgO product obtained has a purity of >90wt.%, and an iodine absorption value of >130mg / g, i.e., a high-purity, high-activity active MgO product is obtained, and the added value of the magnesium ions in the salt lake brine is significantly improved.

[0040] In addition, the active MgO product obtained can also be used as a precipitating agent in the field of nickel-cobalt precipitation, such as in the nickel-cobalt precipitation reaction, which can improve the nickel-cobalt precipitation efficiency and the grade of Ni in the product. When the active MgO product is used for nickel-cobalt precipitation in the nickel-cobalt precipitated filtrate, the concentration of nickel-cobalt in the nickel-cobalt precipitated filtrate is Ni: 0.5-30g / L, Co: 0.5-10g / L. The present application innovatively converts Mg(OH)2 into an active MgO product with a wider application scenario and higher value, which significantly improves the added value of the magnesium ions in the salt lake brine.

[0041] The application, based on the neutralization filtrate after the neutralization reaction of lime slurry digestion slurry, uses evaporation crystallization + dewatering treatment + balling activation treatment process to prepare CaCl2 desiccant products with better moisture absorption. The process converts low-cost lime into high-value-added spherical desiccant, significantly improving the added value of calcium chloride by-products and the economic and social benefits of salt lake brine. The application ingeniously uses the combination of chloride ions in salt lake and calcium ions in CaO to obtain CaCl2, and uses the process of dewatering crystallization combined with balling activation to obtain by-product desiccant. In the case of high-value recovery of main magnesium ions, the application obtains by-product desiccant, maximizing the use of salt lake resources.

[0042] Further, in order to obtain high-performance desiccant, the inventors of the application have improved the conditions of the evaporation crystallization + dewatering treatment + balling activation process.

[0043] In some preferred embodiments, when the neutralization filtrate is subjected to evaporation crystallization and dewatering treatment, the control conditions are as follows: the evaporation crystallization temperature is 50-70℃, such as 50℃, 60℃, 70℃, etc., the time is 2-4h, such as 2h, 3h, 4h, etc., and the pressure is normal pressure or negative pressure; the dewatering treatment temperature is 200-300℃, such as 200℃, 250℃, 300℃, etc., and the time is 2-4h, such as 2h, 3h, 4h, etc. The above conditions are used to obtain the raw material for preparing desiccant, i.e. anhydrous calcium chloride, which creates favorable conditions for obtaining high-moisture absorption desiccant by subsequent balling activation.

[0044] In some preferred embodiments, in the step of balling activation of the anhydrous calcium chloride, the anhydrous calcium chloride is mixed with a binder to form balls, and the mass ratio of anhydrous calcium chloride to binder is 5-10:1, such as 5:1; 6:1; 7:1; 8:1; 9:1; 10:1, etc.; after balling, the balls are activated at a temperature of 150-200℃, such as 150℃, 180℃, 200℃, etc., for 1-3h. Alternatively, the binder is one or more of hydroxypropyl methylcellulose, polyvinyl alcohol and starch solution. Under the above conditions, high-moisture absorption CaCl2 desiccant products are prepared. Further, the moisture absorption rate of the CaCl2 desiccant products is >200%. The desiccant prepared by the above process is evenly filled, has high moisture absorption capacity, and is not easy to produce dust during preparation. The inventors of the application also noticed that if the activation temperature is too low, the moisture absorption capacity of the product will be reduced, and if the activation temperature is too high, decomposition or sintering may occur, and too long activation time, such as more than 4h, not only increases energy consumption, but also may change the product structure and affect the product performance.

[0045] In addition, the water produced after evaporation crystallization and dewatering treatment can be reused to the neutralization reaction process, which can not only reduce wastewater discharge, but also save water resources.

[0046] The technical solutions of the present application will be further described below in combination with the drawings and specific embodiments: Example 1 Firstly, CaO is digested for 2.0 h to obtain a slurry with a concentration of 20 wt.%, which is then added to a chlorinated type salt lake brine containing magnesium ions of 25 g / L. After neutralization reaction at a temperature of 30°C for 2.0 h, Mg(OH)2 and a neutralization filtrate are obtained through filtration and washing.

[0047] The obtained Mg(OH)2 is dehydrated at 120°C for 1.5 h, and then calcined at 600°C for 2.0 h, to obtain high-activity MgO with a purity of 96 wt.% and an iodine absorption value of 145 mg / g. The magnesium oxide can be used as a precipitant for nickel-cobalt precipitation reaction. For example, in the filtrate of the precipitated nickel-cobalt, the concentrations of nickel and cobalt are respectively: Ni: 10 g / L, Co: 3.0 g / L.

[0048] The obtained neutralization filtrate is evaporated and crystallized at a vacuum degree of -0.08 MPa and a temperature of 60°C for 2.0 h, and then dehydrated at 250°C for 3.0 h, to obtain anhydrous calcium chloride powder. The anhydrous calcium chloride powder is mixed with hydroxypropyl methyl cellulose at a mass ratio of 8:1 to prepare balls, which are activated at 180°C for 2.0 h, to obtain a desiccant with a moisture absorption rate of 250%.

[0049] Example 2 Firstly, CaO is digested for 4.0 h to obtain a slurry with a concentration of 30%, which is then added to a chlorinated type salt lake brine containing magnesium ions of 30 g / L. After neutralization reaction at a temperature of 50°C for 4.0 h, Mg(OH)2 and a neutralization filtrate are obtained through filtration and washing.

[0050] The obtained Mg(OH)2 is dehydrated at 150°C for 1.0 h, and then calcined at 800°C for 1.0 h, to obtain high-activity MgO with a purity of 92 wt.% and an iodine absorption value of 135 mg / g. The magnesium oxide can be used as a precipitant for nickel-cobalt precipitation reaction. For example, in the filtrate of the precipitated nickel-cobalt, the concentrations of nickel and cobalt are respectively: Ni: 30 g / L, Co: 0.5 g / L.

[0051] The obtained neutralization filtrate is evaporated and crystallized at normal pressure and a temperature of 70°C for 4.0 h, and then dehydrated at 300°C for 2.0 h, to obtain anhydrous calcium chloride powder. The anhydrous calcium chloride powder is mixed with polyvinyl alcohol at a mass ratio of 10:1 to prepare balls, which are activated at 200°C for 1.0 h, to obtain a desiccant with a moisture absorption rate of 230%.

[0052] Example 3 Firstly, CaO is digested for 1.0 h to obtain a slurry with a concentration of 5.0 wt.%, which is then added to a chlorinated type salt lake brine containing magnesium ions of 15 g / L. After neutralization reaction for 3.0 h at a temperature of 20℃, Mg(OH)2 and a neutralization filtrate are obtained through filtration and washing.

[0053] After dehydration treatment of the obtained Mg(OH)2 at 90℃ for 3.0 h, and calcination at 500℃ for 4.0 h, high-activity MgO with a purity of 98 wt.% and an iodine absorption value of 152 mg / g is obtained. The magnesium oxide can be used as a precipitant in a nickel-cobalt precipitation reaction. For example, in the filtrate of the precipitated nickel-cobalt, the concentrations of nickel and cobalt are 0.5 g / L and 10 g / L, respectively.

[0054] After evaporation crystallization of the obtained neutralization filtrate at a vacuum degree of -0.04 MPa and a temperature of 50℃ for 3.0 h, and dehydration treatment at 200℃ for 4.0 h, anhydrous calcium chloride powder is obtained. After mixing the anhydrous calcium chloride powder with starch at a mass ratio of 5:1 to form balls, and activating the balls at 150℃ for 3.0 h, a desiccant with a moisture absorption rate of 240% is obtained.

[0055] Comparative Example 1 Firstly, CaO is digested for 2.0 h to obtain a slurry with a concentration of 4.5 wt.%, which is then added to a chlorinated type salt lake brine containing magnesium ions of 25 g / L. After neutralization reaction for 5.0 h at a temperature of 15℃, Mg(OH)2 and a neutralization filtrate are obtained through filtration and washing.

[0056] After dehydration treatment of the obtained Mg(OH)2 at 80℃ for 0.5 h, and calcination at 300℃ for 2.0 h, the obtained MgO product has a significantly reduced purity (less than 90 wt.%).

[0057] After evaporation crystallization of the obtained neutralization filtrate at a vacuum degree of -0.08 MPa and a temperature of 60℃ for 2.0 h, and dehydration treatment at 250℃ for 3.0 h, anhydrous calcium chloride powder is obtained. After mixing the anhydrous calcium chloride powder with hydroxypropyl methyl cellulose at a mass ratio of 8:1 to form balls, and activating the balls at 140℃ for 3.5 h, the obtained desiccant has a moisture absorption rate of less than 200%.

[0058] Comparative Example 2 Firstly, CaO is digested for 4.0 h to obtain a slurry with a concentration of 30%, which is then added to a chlorinated type salt lake brine containing magnesium ions of 30 g / L. After neutralization reaction for 4.0 h at a temperature of 50℃, Mg(OH)2 and a neutralization filtrate are obtained through filtration and washing.

[0059] The obtained Mg(OH)2 is dehydrated at 100°C for 0.5h, and then calcined at 850°C for 1.5h to obtain MgO product, whose activity is greatly reduced, and is non-high-activity MgO.

[0060] The obtained neutralized filtrate is evaporated and crystallized at 70°C under normal pressure for 4.0h, and then dehydrated at 300°C for 2.0h to obtain anhydrous calcium chloride powder; the anhydrous calcium chloride powder is mixed with polyvinyl alcohol at a mass ratio of 10:1 to prepare balls, and then activated at 300°C for 2.0h to obtain a desiccant, whose moisture absorption rate is reduced to 200% or less.

[0061] Comparative Example 3 First, the CaO is digested for 1.0h to obtain a slurry with a concentration of 5.0wt.%, which is then added to magnesium ion-containing 15g / L chlorinated salt lake brine, and neutralized at 20°C for 3.0h to obtain Mg(OH)2 and a neutralized filtrate.

[0062] The obtained Mg(OH)2 is calcined at 850°C for 4.0h to obtain MgO product, whose activity is greatly reduced, and is non-high-activity MgO.

[0063] The obtained neutralized filtrate is evaporated and crystallized at 50°C under a vacuum of -0.04MPa for 3.0h, and then dehydrated at 200°C for 4.0h to obtain anhydrous calcium chloride powder; the anhydrous calcium chloride powder is mixed with starch at a mass ratio of 2:1 to prepare balls, and then activated at 350°C for 3.0h to obtain a desiccant, whose moisture absorption rate is reduced to 200% or less.

[0064] The description is given for the purpose of illustration and description, and is not intended to be exhaustive or to limit the application to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Embodiments were chosen and described in order to best explain the principles of the application and its practical application, and to enable others skilled in the art to understand the application for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

1. A method for high-value recovery of magnesium ions from salt lakes, characterized in that, include: The slurry treated with CaO was used to neutralize the brine in the salt lake. After the reaction, the slurry was filtered and washed to obtain Mg(OH)2 and neutralized filtrate. Mg(OH)2 was dehydrated and then calcined to obtain active MgO product. The neutralized filtrate was evaporated and crystallized, and then dehydrated to obtain anhydrous calcium chloride; the anhydrous calcium chloride was then pelletized and activated to obtain a CaCl2 desiccant product.

2. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, The brine in the salt lake is of the chloride type, with a Mg ion concentration of 15–30 g / L.

3. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, Preparation method of CaO digestion slurry: Quicklime is added to a digestion medium solution for 1-4 hours to prepare slurry; wherein the concentration of the slurry is 5-30 wt%; the digestion medium solution is tap water or product water from the evaporation crystallization and dehydration process.

4. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, The neutralization reaction is carried out at a temperature of 20–50°C for 2–4 hours.

5. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, In the step of dehydrating Mg(OH)2 and then calcining it, The dehydration temperature is 90–150℃, and the dehydration time is 1–3 hours. The roasting temperature is 500–800℃, and the roasting time is 1–4 hours.

6. The method for high-value recovery of magnesium ions from salt lakes according to claim 5, characterized in that, The active MgO is used as a precipitant for the nickel-cobalt precipitation reaction, wherein the concentrations of nickel and cobalt in the precipitated nickel-cobalt filtrate are: Ni: 0.5–30 g / L, Co: 0.5–10 g / L.

7. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, In the steps of evaporating, crystallizing, and dehydrating the neutralized filtrate, The evaporation crystallization temperature is 50-70℃, the time is 2-4 hours, and the pressure is atmospheric pressure or negative pressure. The dehydration treatment temperature is 200-300℃, and the time is 2-4 hours.

8. The method for high-value recovery of magnesium ions from salt lakes according to claim 1, characterized in that, The step of activating the anhydrous calcium chloride pellets includes: mixing anhydrous calcium chloride and a binder at a mass ratio of 5 to 10:1 to form pellets, and then activating the pellets at 150 to 200°C for 1 to 3 hours; wherein the binder is one or more of hydroxypropyl methylcellulose, polyvinyl alcohol, and starch solution.

9. An active MgO product prepared by the high-value recovery method of magnesium ions from salt lakes according to any one of claims 1-8.

10. The active MgO product according to claim 9, characterized in that, The active MgO product has a purity >90wt.% and an iodine uptake value >130mg / g.

11. A CaCl2 desiccant product prepared by the high-value recovery method of magnesium ions from salt lakes according to any one of claims 1-8.

12. The CaCl2 desiccant product according to claim 11, characterized in that, The moisture absorption rate of the CaCl2 desiccant product is >200%.

Images