CN114797768B - A kind of magnesium phosphate double salt-activated carbon composite material and its preparation method and application as potassium ion adsorption material - Google Patents

Abstract

The invention discloses a magnesium phosphate double salt-activated carbon composite material, a preparation method thereof and an application as a potassium ion adsorption material. Add phosphate, magnesium source, activated carbon and hydrogen peroxide into water, and carry out stirring reaction to obtain a reaction mixture solution; after ultrasonic treatment, the reaction mixture solution is subjected to sedimentation, solid-liquid separation and drying in sequence to obtain magnesium phosphate compound A composite material composed of salt loaded on activated carbon, the composite material has high selective adsorption and high adsorption capacity for potassium ions in the solution system, breaking through the deficiencies of the existing ion exchange method, precipitation method and other potassium removal technologies. The production and development of potassium extraction (such as seawater potassium extraction, etc.) and solution potassium removal (lithium and potassium separation, etc.) industries are of great significance.

Description

A kind of magnesium phosphate double salt-activated carbon composite material and its preparation method and as potassium ion Application of sub-adsorbent materials

technical field

The invention relates to a potassium ion adsorption material, in particular to a magnesium phosphate double salt-activated carbon composite material and a preparation method thereof, and also relates to the application of a magnesium phosphate double salt-activated carbon composite material in the adsorption of potassium ions in a solution system The invention belongs to the technical field of extraction and separation of potassium ions in a solution system.

Background technique

Potassium, as an indispensable nutrient element for crop growth, plays a very important role in my country's agricultural production, and is also widely used in industrial production such as paint pigments, glass, pharmaceuticals, and leather. my country is one of the more serious potassium deficiency areas in the world. Potassium, as a non-renewable resource, is short of reserves, its proportion is very low, and its mining volume is limited. Potassium used in the industry has long been dependent on imports, and the development of the industry has been greatly restricted. The minerals of natural silicate minerals are far from enough to provide potassium components. Compared with other material components, potassium ions are abundant in the ocean, which is an important way to effectively obtain potassium substances.

So far, efficient separation and extraction of potassium from solution systems based on the introduction of impurities is a major technical challenge. For example, extracting potassium from seawater with complex chemical resource components and variable environment is the focus and difficulty of research. Evaporation and crystallization is the most classic technological route in extracting potassium from seawater. However, due to the shortcomings of the evaporation crystallization method such as low purity of potassium salt, long production cycle, high energy consumption, and low efficiency, it is difficult to meet the requirements of industrialization. The chemical precipitation method is also an important method for enriching potassium in the solution system. According to the different characteristics of various potassium salts, the corresponding precipitant is added to the solution system to precipitate the potassium salt in the form of insoluble matter, and then purify the precipitate Potassium salt with higher purity can be obtained. For example, sodium tetraphenylborate is a precipitant with high selectivity to K ⁺ and a more thorough precipitation with potassium; although chemical precipitation can obtain potassium salts with higher purity, sodium tetraphenylborate is too expensive and economically It is not feasible, so finding a safe, cheap, environmentally friendly and recyclable precipitant is the key. The liquid membrane extraction method is to use the difference in the distribution of potassium in the extractant phase, the water phase, and the seawater phase to achieve the purpose of concentrating or separating specific substances. The more commonly used extractants are isoamyl alcohol, Mixtures of organic acids and phenols, polycyclic ethers, n-butanol, etc. Although this method has a high selectivity to potassium, the use of extractants is expensive and is not suitable for industrial use.

At present, the ion exchange adsorption method is a clean and efficient main measure for the selective separation of target elements. The principle is that the ion exchange method is carried out with an ion exchanger as a carrier. When the ion exchanger is in contact with a liquid, the available The ions that are suitable for exchange will be exchanged with the ions in the liquid, so as to achieve the enrichment of ions. The key to this method is to select cheap, environmentally friendly and efficient ion exchangers. The common ion exchange method is mainly divided into two aspects. Enrichment. Japanese scholars have carried out many research results on this. The synthesized zirconium tungstate phosphate has the advantages of good selectivity and high stability for potassium components. However, due to the high price of zirconium compounds, the economic requirements cannot be passed, and industrialization has not yet been realized. On the other hand, natural substances have high-efficiency selective enrichment adsorption for potassium components in solution. For example, it has been reported that ion sieves and natural zeolites have high selective adsorption performance for potassium ions in seawater, but for solution systems with high concentration of potassium ions, their adsorption and removal effects still need to be strengthened.

It can be said that how to efficiently and selectively extract potassium components has become a bottleneck problem in the development of solution potassium extraction technology. The development of a low-cost, high-efficiency and selective potassium extraction technology is an important way to enrich potassium in the solution system, and more importantly, , not only in the field of seawater potassium extraction, but also in the field of potassium removal and purification in lithium ore leaching liquid purification lithium and other systems. Separation will have far-reaching significance for the upgrading and innovation of lithium extraction technology, and will also lay an important foundation for the purification and smelting of back-end lithium products.

Contents of the invention

Aiming at existing solutions to extract potassium and liquid-phase potassium removal technology, there are problems such as low potassium removal efficiency and high cost. The first object of the present invention is to provide a magnesium phosphate double salt-activated carbon composite material, which has a strong impact on the solution. Potassium ions in the system have high selective adsorption and high adsorption capacity, which is of great significance to the production and development of solutions for potassium extraction (such as seawater potassium extraction, etc.) and solution potassium removal (such as lithium-potassium separation, etc.) .

The second object of the present invention is to provide a preparation method of magnesium phosphate double salt-activated carbon composite material, the preparation method has simple process, convenient operation, low energy consumption, and is conducive to large-scale production.

The third object of the present invention is to provide a kind of application of magnesium phosphate double salt-activated carbon composite material, it is applied to the potassium ion adsorption in the solution system as adsorption material, shows high selectivity and high enrichment capacity, Moreover, the recycling and regeneration of the adsorption material can be realized, and the use method is highly adaptable, efficient, and low-cost, and is especially suitable for industrial production such as seawater potassium extraction or lithium-potassium separation.

In order to achieve the above-mentioned technical purpose, the present invention provides a preparation method of magnesium phosphate double salt-activated carbon composite material. The preparation method is to add phosphate, magnesium source, activated carbon and hydrogen peroxide into water, carry out stirring reaction, and obtain the reaction Mixed solution; the reaction mixed solution is subjected to ultrasonic treatment, followed by settling, solid-liquid separation and drying to obtain the product.

The technical scheme of the present invention uses activated carbon as a carrier, and phosphate and magnesium salts are promoted by hydrogen peroxide to generate magnesium phosphate double salt and deposit on the surface of activated carbon in situ, forming a high specific surface area and porosity, and fully exposed active sites Magnesium phosphate double salt-activated carbon composite material with highly dispersed active ingredients of magnesium phosphate double salt, so that the adsorption capacity and adsorption selectivity of the composite material can be greatly improved. At the same time, the composite material uses magnesium phosphate double salt as the active center for the adsorption of potassium ions, which has a unique active affinity for potassium, and can achieve efficient and selective enrichment of potassium components in the solution without increasing the impurity elements in the solution. The goal of extracting or removing potassium from the solution is effectively realized.

As a preferred solution, the phosphate includes sodium phosphate and/or ammonium phosphate, more preferably at least one of sodium pyrophosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and ammonium phosphate. The main function of phosphate is to produce phosphate ions by hydrolysis and ionization in the solution system. Theoretically, all water-soluble phosphates meet the requirements of the technical solution of the present invention. From the comprehensive consideration of cost and water solubility, ammonium phosphate is the most preferred . The technical solution of the present invention fully reacts with sodium phosphate salt/ammonium phosphate salt and magnesium-containing salt, and a large amount of Na ⁺ or NH ₄ ⁺ can be adsorbed in the magnesium phosphate double salt lattice, which can be exchanged with K ⁺ in the solution to realize efficient ion exchange, Na ⁺ and NH ₄ ⁺ have the same number of electrons and similar properties, but the charge of NH ₄ ⁺ is more dispersed than that of Na ⁺ , and the ion radius of NH ₄ ⁺ is closer to the radius of K ⁺ 0.138nm, so ammonium phosphate is more preferred. Synthesis of magnesium phosphate double salt, this feature also provides an important basic condition for the adsorption material to replace K ⁺ from the solution system, more importantly, when K ⁺ enters the lattice of magnesium phosphate double salt, it will gradually form a new The dissolved complex anion will interact with K ⁺ to form a new phase mineral precipitation containing potassium.

As a preferred solution, the magnesium source includes at least one of magnesium sulfate, magnesium chloride, and magnesium oxide. Magnesium sources are mainly salts containing magnesium ions. In theory, magnesium salts that are easily soluble in water are suitable for the technical solution of the present invention. Considering economic cost and disposal efficiency, magnesium chloride is preferably used.

As a preferred scheme, the proportion of activated carbon, phosphate and magnesium source is measured according to the molar ratio of C, P and Mg of 0.5-1:0.5-1.2:1. If the phosphate concentration is too high, it will promote the combination of phosphate and other impurity metal ions, such as heavy metal ions such as iron and copper, and adhere to the surface of the adsorbent material, which will significantly reduce the adsorption of the adsorbent material to the potassium component in the solution. The use of a high amount of activated carbon will increase the preparation cost of the composite material, and will reduce the adsorption capacity of the adsorption material, and the use cost will also increase. More preferably, the proportion of activated carbon, phosphate and magnesium source is measured according to the molar ratio of C, P and Mg of 0.8-1:0.8-1:1. As a preferred solution, the concentration of the activated carbon in water is 1-3 mol/L. The concentration of activated carbon in water is most preferably 1.5-2.5 mol/L.

As a preferred solution, the hydrogen peroxide is added in the form of a solution with a concentration of 20-40 wt%. The added volume concentration of the hydrogen peroxide in water is 0.2%-5%. The addition of low-concentration hydrogen peroxide helps to promote the reaction combination of active components in the solution system and increase the reaction rate.

As a preferred solution, the stirring reaction conditions are as follows: the pH is controlled at 10-13, the temperature is 30-50° C., and the time is 60-90 minutes. Better reaction of reagents can be promoted under optimal reaction conditions.

As a preferred solution, the time for the ultrasonic treatment is 40-60 minutes.

As a preferred solution, the drying condition is: drying at 160° C. to 200° C. for 10 to 12 hours. Higher temperature can realize the active carbon and magnesium phosphate double salt payload and enhance the stability characteristics of the composite.

The invention also provides a magnesium phosphate double salt-activated carbon composite material, which is obtained by the preparation method.

The magnesium phosphate double salt-activated carbon composite material of the present invention uses activated carbon as the carrier material, has the characteristics of high specific surface area, high porosity, good plasticity, etc., and the magnesium phosphate double salt active component with special affinity to potassium ions is evenly loaded On the activated carbon carrier, it can increase its specific surface, expose more active adsorption sites, improve the adsorption capacity for potassium ions, and increase the adsorption selectivity, stability and service life of the composite material for potassium ions.

The invention also provides the application of a magnesium phosphate double salt-activated carbon composite material, which is used as an adsorption material for potassium ion adsorption in a solution system.

The magnesium phosphate double salt-activated carbon composite material of the present invention has a strong affinity for potassium ions in the solution, and has a strong adsorption capacity at the same time, which enables potassium ions to be efficiently enriched in a short period of time in the solution system. In the adsorption material, the removal and extraction of potassium components in the solution are realized.

As a preferred solution, the adsorption conditions are as follows: the temperature is 40-60° C., the time is 30-60 minutes; the stirring rate is 150-200 r/min. Under the optimal adsorption conditions, it can ensure that the surface sites of the adsorption material can be fully combined with the potassium component, and realize the efficient enrichment of the potassium component in the solution. At the same time, the adsorption reaction is affected by the external diffusion and internal diffusion rate, and an appropriate temperature is maintained. And rotation speed can promote the adsorption reaction.

As a preferred solution, the mass concentration ratio of the magnesium phosphate double salt-activated carbon composite material to the potassium ions in the solution system is 0.5-0.8:1. This dosage condition can effectively realize the high-efficiency enrichment of potassium components in the solution.

The magnesium phosphate double salt-activated carbon composite material of the present invention can be widely used in the separation and extraction of potassium components in solutions, not only for the extraction of low-concentration potassium components in seawater, but also for high-concentration potassium-containing solutions. The high-efficiency enrichment of potassium components, the composite adsorption material has the characteristics of large adsorption capacity, high activity, simple and easy preparation, economical cost, and has broad industrial application value in the market. It is used for the extraction of potassium components or the removal of potassium components. Provide important technical means.

The preparation method of the magnesium phosphate double salt-activated carbon composite material of the present invention provided by the invention comprises the following specific steps:

Step 1: Preparation of phosphate double salt-activated carbon adsorption material

Add magnesium salt, activated carbon and an appropriate amount of hydrogen peroxide to the sodium phosphate or ammonium phosphate inorganic salt solution in sequence. It is worth noting that the molar ratio of C, P and Mg in the solution system should be controlled to be 0.5-1:0.5-1.2 : 1. Excessively high phosphorus concentration will promote the combination of impurity ions in the solution. On the one hand, it will affect the formation of adsorption materials. The hydrogen peroxide can promote the reaction, and the hydrogen peroxide is added in the form of a solution with a concentration of 20-40 wt%, and its added volume concentration in water is 0.2%-5%. The pH of the reaction should be controlled between 10-13, the temperature is 30-50°C, and the time is 60-90 minutes. Use a magnetic stirring device to rotate evenly at a low speed. Under these reaction conditions, a better combination reaction of the two substances can be promoted. The synthesis rate of the adsorption material is about 85%. Based on the principle of solution chemistry, the lower the solubility product, the easier it is to generate. This lays a theoretical foundation for the simple and effective reaction preparation of the adsorption material. At the same time, the ultrasonic treatment control time is 40-60min. The components of the solution are uniformly dispersed, and then dried in a drying oven at a reaction condition of 160-200° C. for 10-12 hours to obtain the final product.

Step 2: Efficient extraction of potassium components in the solution system

Add the composite adsorption material obtained in step 1 to the solution system containing potassium components, and control the ratio of the amount of the adsorption material to the mass concentration of potassium ions in the solution to be 0.5-0.8:1. During the adsorption process, the temperature should be controlled at 40-60°C, and the time should be 30-60 minutes. A magnetic stirring device should be used to rotate evenly at a speed of 150-200 r/min, and the pH should be controlled to be weakly alkaline. Through the full combination reaction of sodium phosphate/ammonium phosphate and magnesium-containing salt, a large amount of Na ⁺ or NH ₄ ⁺ can be adsorbed in the lattice of magnesium phosphate double salt to achieve efficient ion exchange with K ⁺ in the solution. Na ⁺ and NH ₄ ⁺ have the same number of electrons and similar properties. But the charge of NH ₄ ⁺ is more dispersed than that of Na ⁺ , and the ion radius of NH ₄ ⁺ is closer to that of K ⁺ 0.138nm. This feature also provides an important basic condition for the adsorption material to replace K ⁺ from the solution system. More importantly, when K ⁺ enters the lattice of magnesium phosphate double salt, it will gradually form a new phase. The complex anions in the complex will communicate with K ⁺ to form a new phase mineral precipitation containing potassium. At the same time, because of the loading of activated carbon, on the one hand, the anion field in the framework of the adsorption material itself is weak, so the water and interaction between the ions and these fully exposed network anion active sites play an important role in the exchange behavior of K ⁺ On the other hand, the carrier function of activated carbon will further promote the removal efficiency of potassium components. And because proper heating can increase the activity of the site of the adsorption material, the probability and range of effective combination with the potassium component in the solution are increased.

Compared with the existing industrial potassium removal technology, the technical solution of the present invention brings beneficial technical effects:

At present, the efficient separation and extraction of potassium from the solution system is a major research challenge. The key to the present invention is to provide a phosphate double salt-activated carbon adsorption material that can efficiently and selectively remove potassium in the solution, so that it can be removed without introducing other impurities. , economically and cost-effectively realize the enrichment of potassium components in the solution. This method proposes a magnesium phosphate double salt-activated carbon adsorption material for the first time to adsorb and enrich the potassium component in the solution. The surface sites of the composite material have an efficient affinity adsorption effect for the potassium component in the solution. Compared with the current chemical precipitation method, extraction method, ion exchange adsorption method and other methods to remove potassium from the solution system, the invention of the adsorption material will realize the upgrading of the potassium removal process in industrial applications. The adsorption material has a large adsorption capacity and no secondary pollution It is highly efficient and clean in the overall potassium removal process, and the operation is simple, which meets the process and production of potassium removal under industrial conditions, and is of great significance to the removal and purification of potassium in the solution. More importantly, the adsorption material has the characteristics of renewable use, which can realize the recycling of industrial potassium removal materials.

The preparation method of the magnesium phosphate double salt-activated carbon composite material of the present invention has the advantages of simple process, convenient operation and low energy consumption, and is favorable for large-scale production.

Description of drawings

Fig. 1 is the XRD figure of the magnesium phosphate double salt-activated carbon composite material that embodiment 2 prepares.

Detailed ways

The following specific examples are intended to further illustrate the contents of the present invention, rather than limit the protection scope of the claims.

Example 1

For the experimental exploration of economical and cost-effective synthesis of phosphate double salt-activated carbon adsorption materials, in the chemical reaction system, under different conditions and dosages, it has a great impact on the synthesis rate and efficiency of the substance. In 500ml of water, according to the molar ratio of activated carbon, ammonium phosphate and magnesium sulfate: 0.5:0.5:1, 0.8:0.5:1, 0.8:0.8:1, 0.8:1.0:1, 0.8:1.2:1, add the corresponding reagent and 10ml respectively 30% hydrogen peroxide, the molar concentration of activated carbon in the solution is 2mol/L, the initial reaction pH is controlled to be 3, 7, 11, and 13, the reaction temperature is 50°C, the time is 60min, and the magnetic stirring is 200r/min. Rotate at a constant speed and disperse uniformly for 60 minutes by ultrasound, then separate the solid and liquid through a Buchner funnel and a vacuum filter, and dry in a drying oven at 160°C for 12 hours to obtain a magnesium phosphate double salt-activated carbon adsorption material. The mass of the product was weighed by a balance, and the synthesis rate of the adsorbent material was calculated. Table 1 below shows the synthesis rate of adsorption materials under different conditions. It can be seen from the experimental results that under the condition of pH=11, with the increase of PO ₄ ^3- :Mg ²⁺ , the synthesis rate of the adsorption material increases gradually, and at 0.8:1, the synthesis rate reaches an equilibrium state. Considering the cost and phosphoric acid Root characteristics, choose the dosage of 0.8:0.8:1 for subsequent experimental exploration. Compared with the alkaline environment, the synthesis rate is low under acidic and neutral conditions, which may be due to the fact that in acidic conditions, the combination of ions is greatly hindered, but the pH should not be too high, and magnesium ions are easily adsorbed by hydroxide ions The effect of the effect.

Table 1 Synthesis of adsorption materials under different conditions

C:PO ₄ ^3- :Mg ²⁺ The initial pH of the solution reaction Adsorption material synthesis rate (%) 0.5:0.5:1 10.97 53.25% 0.8:0.5:1 10.96 67.43 0.8:0.8:1 10.93 93.07 0.8:1.0:1 11.06 94.57 0.8:1.2:1 11.02 95.36 0.8:0.8:1 2.97 23.03 0.8:0.8:1 5.97 37.21 0.8:0.8:1 13.10 88.34

Example 2

Add activated carbon, ammonium phosphate, magnesium chloride and 10ml of 30% hydrogen peroxide in 500ml of water at a molar ratio of 0.8:0.8:1, the solubility of activated carbon is 2mol/L. Control the initial pH of the solution reaction to be 11, the reaction temperature to be 50°C, and the time to be 60 minutes. The magnetic stirring is performed at a constant speed of 200r/min. Dry in a drying oven at 160°C for 12 hours to obtain a phosphate double salt-activated carbon adsorption material. Taking the solution system with different potassium concentrations self-made in the laboratory as the research object (0.5g/L, 1g/L, 5g/L, 20g/L), in order to explore the removal effect of phosphate double salt-activated carbon adsorption material on different initial potassium concentrations .In the solution system with different initial potassium solubility, adjust the pH of the solution to 3, 7, 9, 11, 13 according to the dosage of the adsorbent material and the dosage of the potassium ion mass concentration of 0.8:1, and control the adsorption temperature to 50°C. The adsorption time is 30min, and it is uniformly rotated at a speed of 200r/min by a magnetic stirring device. After aging for half an hour, the supernatant in the solution was taken, and the potassium component in the solution was measured by ICP. Table 2 below shows the removal effect of potassium components in each solution system. It can be seen from the experimental results that in an alkaline environment, the adsorption material has a good removal effect on the solution systems with different initial concentrations. For a single low-solubility potassium solution system of 0.5g/L, the potassium removal rate is 98.43%; 20g/L high potassium component solution system, the potassium removal rate is 96.26%. This indicates that the adsorbent material has excellent potassium removal performance. In addition, during the test process, the adsorption and removal of potassium by the adsorption material is also affected by the pH conditions of the reaction. According to the experimental data, under acidic and neutral conditions, the removal of potassium by the adsorption material is not good, which may be due to the acidic conditions. The affinity between the surface sites of the adsorbed material and the potassium component is suppressed, resulting in a decrease in the potassium removal rate. In alkaline conditions, the activity of the surface sites of the adsorption material increases, which provides the possibility of more effective adsorption and removal for potassium removal.

Table 2 Potassium removal rate and lithium loss rate changes in the solution system

Potassium concentration Solution pH Potassium removal rate (%) 0.5g/L 10.96 98.43 1.0g/L 11.02 97.07 5g/L 10.98 96.57 20g/L 10.97 96.26 1.0g/L 2.93 27.03 1.0g/L 6.97 76.21 1.0g/L 9.00 97.15 1.0g/L 13.10 86.34

Example 3

Taking a lithium mother liquor rich in high concentration potassium components in an industry in Sichuan and a potassium solution in a certain seawater as the research object, this solution system has a high potassium concentration and a high content of lithium components, and because lithium and potassium are located in The same main family has very similar chemical properties. If the traditional precipitation method or evaporation crystallization method is used, it is undoubtedly impossible to effectively remove the potassium component in the solution. Add activated carbon, ammonium phosphate, magnesium chloride and 10ml of 30% hydrogen peroxide in 500ml of water at a molar ratio of 0.8:0.8:1, the solubility of activated carbon is 2mol/L. The initial pH of the reaction solution was controlled to be 11, the reaction temperature was 50°C, the reaction time was 60 minutes, and the magnetic stirring was performed at a constant speed of 200r/min. The solid-liquid separation was carried out through a Buchner funnel and a vacuum filter to obtain a phosphate double salt-activated carbon adsorption material. Add the adsorption material to the lithium mother liquor according to the dosage of the adsorption material and the dosage of the potassium ion mass concentration of 0.5:1, 0.8:1, and 1:1. The speed of 200r/min rotates evenly. After aging for half an hour, the supernatant in the solution was taken, and the potassium component in the solution was measured by ICP. Table 3 below shows the removal effects of potassium components in different solutions with different amounts of adsorbent materials. At the same time, in order to explore whether the adsorption material has the same adsorption effect on other ions with similar properties, the loss of lithium components under different solution conditions was also measured. It can be seen from the table below that in the seawater solution system, the adsorption material can effectively enrich the potassium component in the seawater, and the overall potassium removal rate is 98.75%. With the increase of the amount of the adsorption material, the potassium removal rate in the solution gradually increases . At 0.8:1, the overall removal rate reached the equilibrium maximum. More importantly, there is almost no significant loss of lithium during the removal of potassium components. When the ratio of adsorption material to K ⁺ is 1:1, the loss rate of lithium reaches 5.67%. This is due to the increase in the amount of adsorption material, which increases the probability of free phosphate radicals combining with lithium components to a certain extent, and increases the loss rate of lithium components. But in general, the composite adsorption material has a unique selective adsorption for potassium components and is not interfered by ions with similar properties. At the same time, this also provides a reference for the removal of potassium components in actual solution systems.

Table 3 The removal rate of potassium components and the change of lithium loss rate in the solution system

Claims (8)

1. a preparation method of magnesium phosphate double salt-activated carbon composite material, is characterized in that: phosphate, magnesium source, gac and hydrogen peroxide are added in water, carry out stirring reaction, obtain reaction mixed solution; After ultrasonic treatment, it is obtained through sedimentation, solid-liquid separation and drying in sequence; The ratio of activated carbon, phosphate and magnesium source is measured according to the molar ratio of C, P and Mg being 0.5～1:0.5～1.2:1, and the concentration of the activated carbon in water is 1～3mol/L; The stirring reaction conditions are as follows: the pH is controlled at 10-13, the temperature is 30-50° C., and the time is 60-90 minutes. 2. the preparation method of a kind of magnesium phosphate double salt-activated carbon composite material according to claim 1, is characterized in that: The phosphate comprises sodium phosphate and/or ammonium phosphate; The magnesium source includes at least one of magnesium sulfate, magnesium chloride, and magnesium oxide. 3. the preparation method of a kind of magnesium phosphate double salt-activated carbon composite material according to claim 1 is characterized in that: the addition volume concentration of described hydrogen peroxide in water is 0.2%～5%; It is added in the form of a solution with a mass percentage concentration of 20-40%. 4. The preparation method of a magnesium phosphate double salt-activated carbon composite material according to claim 1, characterized in that: the ultrasonic treatment time is 40 to 60 minutes. 5 . The preparation method of a magnesium phosphate double salt-activated carbon composite material according to claim 1 , wherein the drying condition is: drying at 160° C. to 200° C. for 10 to 12 hours. 6. A magnesium phosphate double salt-activated carbon composite material, characterized in that it is obtained by the preparation method described in any one of claims 1-5. 7. the application of a kind of magnesium phosphate double salt-activated carbon composite material described in claim 6 is characterized in that: it is applied to the potassium ion adsorption in the solution system as adsorption material. 8. the application of a kind of magnesium phosphate double salt-activated carbon composite material according to claim 7, is characterized in that: The solution system contains lithium ions and/or sodium ions, and the pH is alkaline; The adsorption conditions are as follows: the temperature is 40-60° C., the time is 30-60 minutes, and the stirring rate is 150-200 r/min.