Polyhalite leaching agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of mining of soluble sylvite in polyhalite, and particularly discloses a polyhalite leaching agent and a preparation method and application thereof.On a maleic anhydride-sodium allysulfonate copolymer molecular chain, carboxyl generated by hydrolysis of maleic anhydride is beneficial to dissolution of K < + > in polyhalite; the sulfonic acid group on the molecular chain of the copolymer provides electrostatic repulsive force, and the whole macromolecular chain provides a strong steric hindrance effect to effectively prevent gypsum from nucleation and growth and finally form thick crystals, and when the thick crystals are stacked, many gaps are left to form a loose and porous filter cake structure, so that the effect of blocking the gypsum is achieved. A porous filter cake structure allows a fresh leaching agent to continuously flow in to dissolve residual polyhalite; meanwhile, dissolved potassium ions can be easily diffused into a main body solution.

Description

Technical Field

[0001] This invention relates to the field of mining technology for soluble potassium salts in carnallite, specifically to a carnallite leaching agent, its preparation method, and its application. Background Technology

[0002] Carbohydrates are sulfate minerals rich in potassium, magnesium, and calcium, with the chemical formula K₂SO₄·MgSO₄·2CaSO₄·2H₂O. Therefore, they are considered a potential and highly valuable potassium resource. However, carbohydrates have a dense structure and high crystal stability, and they often occur in close association with other evaporite minerals such as gypsum and halite in nature. This makes it difficult to achieve economical and efficient separation and enrichment of the potassium content using conventional physical beneficiation methods. Therefore, the core technology for developing and utilizing carbohydrate resources lies in how to efficiently and selectively extract potassium from them into solution through chemical leaching.

[0003] While several existing technologies have attempted to extract potassium from carnallites through leaching, these methods generally suffer from significant limitations. Using strong inorganic acids such as hydrochloric acid or sulfuric acid as leaching agents can effectively disrupt the crystal structure due to the high concentration of hydrogen ions, resulting in a high potassium leaching rate. However, this method inevitably leads to the rapid dissolution of all associated calcium and magnesium components in the mineral sample, resulting in an exceptionally complex leachate composition with persistently high calcium and magnesium ion concentrations. This not only severely impacts the crystallization and purification efficiency of subsequent potassium salt products but also causes serious corrosion problems to the reaction equipment. Furthermore, the use of strong acids introduces risks related to waste acid treatment and environmental pollution. On the other hand, while leaching systems relying solely on brine offer some improvement in operational safety, their leaching efficiency still needs further enhancement.

[0004] Chinese patent document CN200510021637.X discloses a method for leaching potassium in carnallite ore. The method involves leaching crushed ore with a leaching agent and then recovering the leaching solution. The leaching solution used contains Ca. 2+ and / or Ba 2+ Aqueous solutions, and / or containing CO3 2- HCO3 - PO4 3- HPO4 2- SiO3 2- An aqueous solution of at least one of the following, preferably an aqueous solution of CaCl2; although this method can remove K from sparingly soluble potassium salt minerals... + Dissolution, for K in ore + The extraction rate can reach over 80%, but for K... + The extraction rate still needs to be further improved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a carnallite leaching agent, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polyhalite leaching agent, wherein the polyhalite leaching agent is an aqueous solution containing NaCl, CaCl2, and a maleic anhydride-sodium allyl sulfonate copolymer.

[0007] In the technical solution disclosed in this invention, the mass fraction of NaCl in the aqueous solution is 20-25%, for example, 20%, 21%, 22%, 23%, 24%, 25%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0008] In the technical solution disclosed in this invention, the mass fraction of CaCl2 in the aqueous solution is 3-5%, for example, 3%, 3.5%, 4%, 4.5%, 5%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0009] In the technical solution disclosed in this invention, the mass fraction of maleic anhydride-sodium allyl sulfonate copolymer in the aqueous solution is 0.05-0.1%, for example, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0010] In the technical solution disclosed in this invention, the preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: maleic anhydride and sodium allyl sulfonate are added to deionized water and stirred evenly. Then an initiator is added, and the mixture is heated and stirred to react. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

[0011] Specifically, the mass ratio of maleic anhydride, sodium allyl sulfonate, and initiator is 5-10:2-4:0.1-0.2. For example, ratios such as 5:2:0.1, 5:2:0.2, 5:4:0.1, 5:4:0.2, 8:2:0.1, 8:3:0.15, 8:4:0.2, 10:2:0.1, 10:3:0.15, and 10:4:0.1 can be selected, but are not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0012] More specifically, the initiator is selected from persulfates, such as potassium persulfate, sodium persulfate, or ammonium persulfate.

[0013] Specifically, the temperature for heating and stirring the reaction is 60-80℃, for example, 60℃, 65℃, 70℃, 75℃, or 80℃ can be selected; the time for heating and stirring the reaction is 3-5h, for example, 3h, 3.5h, 4h, 4.5h, or 5h can be selected, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] During the leaching process, without a control agent, calcium sulfate tends to form elongated needle-like crystals. These crystals intertwine to form a dense, impermeable filter cake, making filtration difficult and, more importantly, trapping unreacted potassium inside, preventing further dissolution. The maleic anhydride-sodium allyl sulfonate copolymer molecular chain provided by this invention contains carboxyl groups generated from the hydrolysis of maleic anhydride, which is beneficial for potassium in heterohalite. + The leaching of gypsum is facilitated by the sulfonic acid groups on the copolymer molecular chain, which provide electrostatic repulsion, while the entire polymer chain provides a strong steric hindrance effect, effectively preventing gypsum from forming nuclei and growing, eventually forming coarse crystals. When coarse crystals accumulate, they leave many gaps, forming a loose, porous filter cake structure. The porous filter cake structure allows fresh leaching agent to continuously flow in, dissolving residual carnallite; at the same time, it also allows the dissolved potassium ions to easily diffuse into the main solution.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned heterohalite leaching agent, comprising the following steps: adding NaCl, CaCl2 and maleic anhydride-sodium allyl sulfonate copolymer to deionized water and stirring evenly to obtain the heterohalite leaching agent.

[0016] Thirdly, the present invention also provides the application of the above-mentioned carnallite leaching agent in the carnallite mining process.

[0017] In the technical solution disclosed in this invention, the application steps are as follows: carnallite ore is mixed with a leaching agent and subjected to leaching treatment, followed by solid-liquid separation to obtain a product containing K. + The liquid phase.

[0018] In the technical solution disclosed in this invention, the solid-liquid ratio of carnallite ore and leaching agent is 1:8-15, for example, 1:8, 1:10, 1:12, 1:15 can be selected, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The leaching agent for heterohalite provided by the present invention is obtained by compounding sodium chloride, calcium chloride and maleic anhydride-sodium allyl sulfonate copolymer. The resulting leaching agent can significantly promote the dissociation of heterohalite crystal structure and make the by-product gypsum form coarse crystals that are easy to filter. This effectively improves the potassium dissolution rate and leaching rate, and also significantly improves the efficiency of subsequent solid-liquid separation.

[0020] (2) The carboxyl groups generated by the hydrolysis of maleic anhydride on the molecular chain of the maleic anhydride-sodium allyl sulfonate copolymer provided by the present invention are beneficial to the K in the carboxylic acid. + The leaching of gypsum is facilitated by the sulfonic acid groups on the copolymer molecular chain, which provide electrostatic repulsion, while the entire polymer chain provides a strong steric hindrance effect, effectively preventing gypsum from forming nuclei and growing, eventually forming coarse crystals. When coarse crystals accumulate, they leave many gaps, forming a loose, porous filter cake structure. The porous filter cake structure allows fresh leaching agent to continuously flow in, dissolving residual carnallite; at the same time, it also allows the dissolved potassium ions to easily diffuse into the main solution. Attached Figure Description

[0021] Figure 1 For different pairs of K + A comparison chart of dissolution rates. Detailed Implementation

[0022] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0023] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0024] Example 1 A method for preparing a polyhalite leaching agent includes the following steps: Add 20g NaCl, 5g CaCl2 and 0.05g maleic anhydride-sodium allyl sulfonate copolymer to 100mL deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0025] The preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: 8g of maleic anhydride and 3g of sodium allyl sulfonate are added to 100mL of deionized water and stirred evenly. Then, 0.15g of initiator ammonium persulfate is added, and the mixture is heated and stirred at 80℃ for 3h. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

[0026] Example 2 A method for preparing a polyhalite leaching agent includes the following steps: Add 25g NaCl, 3g CaCl2 and 0.1g maleic anhydride-sodium allyl sulfonate copolymer to 100mL deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0027] The preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: 5g of maleic anhydride and 2g of sodium allyl sulfonate are added to 100mL of deionized water and stirred evenly. Then, 0.1g of initiator ammonium persulfate is added, and the mixture is heated and stirred at 80℃ for 3h. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

[0028] Example 3 A method for preparing a polyhalite leaching agent includes the following steps: Add 22g NaCl, 4g CaCl2 and 0.08g maleic anhydride-sodium allyl sulfonate copolymer to 100mL deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0029] The preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: 10g of maleic anhydride and 4g of sodium allyl sulfonate are added to 100mL of deionized water and stirred evenly. Then, 0.2g of initiator ammonium persulfate is added, and the mixture is heated and stirred at 80℃ for 3h. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

[0030] Example 4 A method for preparing a polyhalite leaching agent includes the following steps: Add 24g NaCl, 4g CaCl2 and 0.06g maleic anhydride-sodium allyl sulfonate copolymer to 100mL deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0031] The preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: 5g of maleic anhydride and 4g of sodium allyl sulfonate are added to 100mL of deionized water and stirred evenly. Then, 0.2g of initiator ammonium persulfate is added, and the mixture is heated and stirred at 80℃ for 3h. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

[0032] Comparative Example 1 A method for preparing a polyhalite leaching agent includes the following steps: Add 20g NaCl and 5g CaCl2 to 100mL of deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0033] Compared to Comparative Example 1 and Example 1, no maleic anhydride-sodium allyl sulfonate copolymer was added.

[0034] Comparative Example 2 A method for preparing a polyhalite leaching agent includes the following steps: Add 20g NaCl, 5g CaCl2 and 0.05g sodium allyl sulfonate copolymer to 100mL deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0035] The preparation method of the sodium allyl sulfonate copolymer is as follows: 3g of sodium allyl sulfonate is added to 100mL of deionized water and stirred evenly. Then, 0.15g of initiator ammonium persulfate is added, and the mixture is heated and stirred at 80℃ for 3h. After the reaction is completed, the sodium allyl sulfonate copolymer is obtained by spray drying.

[0036] Compared to Example 1, maleic anhydride was not added to the copolymer in Comparative Example 2.

[0037] Comparative Example 3 A method for preparing a polyhalite leaching agent includes the following steps: Add 20g NaCl, 5g CaCl2 and 0.05g sodium dodecylbenzenesulfonate to 100mL of deionized water and stir until homogeneous to obtain the carnallite leaching agent.

[0038] Compared with Example 1, Comparative Example 3 uses sodium dodecylbenzenesulfonate instead of maleic anhydride-allyl sulfonate copolymer.

[0039] The solvents prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the specific steps are as follows: The carnallite ore used in the experiment came from a salt lake area in Qinghai Province. The carnallite ore contained K... + The mass content is 8.3%, Mg 2+ The mass content is 3.4%, Ca 2+ The mass content is 4.6%, Cl - The mass content is 19.5%, SO4 2- The mass content was 24.2%. No crushing treatment was performed on the carnallite ore sample in the experiment. The whole sample was used directly to ensure the authenticity of the experimental conditions. The main equipment used in the experiment included a high temperature and high pressure reactor to ensure that the actual temperature and pressure conditions of the ore layer could be simulated.

[0040] 100 mL of the leaching agents prepared in Examples 1-4 and Comparative Examples 1-3, and 10 g of carnallite ore were respectively placed into a high-temperature and high-pressure reactor. The reactor temperature was set to 85°C and the pressure to 48 MPa to ensure consistency with the actual formation temperature and pressure conditions of the carnallite ore layer. After opening the reactor, the samples were allowed to stand for 7 days to allow the leaching agent to fully contact the carnallite ore. During the experiment, the sealing of the reactor and the stability of the temperature and pressure conditions were checked regularly to ensure that the temperature and pressure conditions remained constant throughout the experiment. After the experiment, the leachate in the reactor was removed, and the resulting solution was filtered to remove impurities. K was measured. +The concentration was calculated and the dissolution rate was determined. The experimental results are as follows: Figure 1 As shown, from Figure 1 As can be seen from the above, compared with Comparative Examples 1-3, the solvent prepared in the embodiments of the present invention has a better effect on K. + The dissolution rate is significantly improved, reaching over 95%.

[0041] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A polyhalite leaching agent, characterized in that, The carnallite leaching agent is an aqueous solution containing NaCl, CaCl2, and a copolymer of maleic anhydride-sodium allyl sulfonate.

2. The carnallite leaching agent according to claim 1, characterized in that, The mass fraction of NaCl in the aqueous solution is 20-25%.

3. The carnallite leaching agent according to claim 1, characterized in that, The mass fraction of CaCl2 in the aqueous solution is 3-5%.

4. The carnallite leaching agent according to claim 1, characterized in that, The mass fraction of maleic anhydride-sodium allyl sulfonate copolymer in aqueous solution is 0.05-0.1%.

5. The carnallite leaching agent according to claim 1, characterized in that, The preparation method of the maleic anhydride-sodium allyl sulfonate copolymer is as follows: maleic anhydride and sodium allyl sulfonate are added to deionized water and stirred evenly. Then an initiator is added, and the mixture is heated and stirred to react. After the reaction is completed, the mixture is spray-dried to obtain the maleic anhydride-sodium allyl sulfonate copolymer.

6. The carnallite leaching agent according to claim 5, characterized in that, The mass ratio of maleic anhydride, sodium allyl sulfonate, and initiator is 5-10:2-4:0.1-0.

2.

7. The carnallite leaching agent according to claim 5, characterized in that, The initiator is selected from persulfate.

8. The carnallite leaching agent according to claim 5, characterized in that, The heating and stirring reaction is carried out at a temperature of 60-80℃ for 3-5 hours.

9. The method for preparing the carnallite leaching agent according to any one of claims 1-8, characterized in that, The process includes the following steps: adding NaCl, CaCl2, and maleic anhydride-sodium allyl sulfonate copolymer to deionized water and stirring until homogeneous to obtain the carnallite leaching agent.

10. The application of the carnallite leaching agent as described in any one of claims 1-8 in the carnallite mining process.

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