Method for purifying chloride ions in ammonium nitrate solution and application thereof

Abstract

The invention relates to the field of ammonium nitrate solution preparation, and particularly discloses a method for purifying chloride ions in an ammonium nitrate solution and application of the method. The invention discloses a method for purifying chloride ions in an ammonium nitrate solution. The method comprises the following steps: performing reverse osmosis impurity removal on source water, and adding a chloride ion adsorbent to obtain desalted water; ammonia gas and oxygen react to generate nitrogen oxide, and the nitrogen oxide and desalted water react to generate dilute nitric acid; gasifying the liquid ammonia to obtain ammonia gas, carrying out neutralization reaction on the ammonia gas and dilute nitric acid, and evaporating to obtain a high-concentration ammonium nitrate solution; the chloride ion adsorbent is sodium alginate coated activated carbon loaded silver ions. According to the method, the chloride ion adsorbent is added into the source water used during preparation of the ammonium nitrate solution, so that the concentration of chloride ions in the source water is reduced, and the chloride ions in the prepared ammonium nitrate solution are removed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ammonium nitrate solution preparation, and more particularly to a method for purifying chloride ions in an ammonium nitrate solution and application thereof. BACKGROUND

[0002] N2O has important medical uses, and its anesthetic and analgesic effects are significant, and it is widely used as an anesthetic for surgery and dentistry. N2O is generally prepared by thermal decomposition of an ammonium nitrate solution, which is stable at room temperature, but in the preparation process, because the source water contains chloride ions, the prepared ammonium nitrate solution contains residual chloride ions, the presence of chloride ions can reduce the decomposition temperature of the ammonium nitrate solution, and accelerate the decomposition of the ammonium nitrate solution, thereby causing safety hazards such as decomposition explosion. Therefore, it is particularly important to reduce the concentration of chloride ions in the ammonium nitrate solution for safe preparation of N2O. SUMMARY

[0003] In order to develop a method for removing chloride ions from water, thereby reducing the concentration of chloride ions in the ammonium nitrate solution, the present application provides a method for purifying chloride ions in an ammonium nitrate solution and application thereof.

[0004] In a first aspect, the present application provides a method for purifying chloride ions in an ammonium nitrate solution, which adopts the following technical solution: A method for purifying chloride ions in an ammonium nitrate solution, comprising the following steps: S1, after the source water is removed by reverse osmosis, a chloride ion adsorbent is added to obtain desalted water; ammonia gas is reacted with oxygen to generate nitrogen oxides, and the nitrogen oxides are reacted with the desalted water to generate dilute nitric acid; S2, liquid ammonia is gasified to generate ammonia gas, and the ammonia gas is subjected to a neutralization reaction with the dilute nitric acid, and after evaporation, a high-concentration ammonium nitrate solution is obtained; The chloride ion adsorbent is sodium alginate-coated activated carbon loaded with silver ions.

[0005] By adopting the above technical solution, the chloride ion adsorbent is added to the source water used in the preparation of the ammonium nitrate solution, thereby reducing the concentration of chloride ions in the source water, and further reducing the concentration of chloride ions in the prepared ammonium nitrate solution, effectively avoiding the decomposition temperature of the ammonium nitrate solution being reduced, the decomposition speed being accelerated, and even causing hazards such as decomposition explosion when the ammonium nitrate solution is prepared by thermal decomposition to prepare N2O.

[0006] The chloride ion adsorbent of the present application is sodium alginate-coated activated carbon loaded with silver ions, which adsorbs chloride ions in source water through the synergistic effect of chemical reaction between silver ions and chloride ions and physical adsorption of activated carbon. Specifically, activated carbon has abundant pore structure and large specific surface area, providing a good carrier platform for the loading of silver ions. After silver ions are loaded on the surface of activated carbon, chloride ions in water will undergo ion exchange and precipitation reaction with silver ions to generate silver chloride precipitate, thereby removing chloride ions from water; at the same time, the physical adsorption of activated carbon itself can also adsorb and retain part of the chloride ions and reaction products, and the two cooperate with each other to achieve efficient removal of chloride ions in water; in addition, sodium alginate is coated on the surface of activated carbon due to its excellent adhesion, and the good hydrophilicity of sodium alginate endows the activated carbon loaded with silver ions with excellent water dispersibility, thereby further improving the adsorption effect of the chloride ion adsorbent.

[0007] Preferably, the preparation method of the chloride ion adsorbent comprises the following steps: (1) treating activated carbon in a nitrogen-containing gas by plasma to obtain aminated activated carbon; adding the aminated activated carbon into water to obtain a suspension; adding silver nitrate solution into ammonia water to dissolve the initially generated precipitate to form a silver-ammonia solution; adding the suspension into the silver-ammonia solution and reacting at 40-60°C for 30-60 min, and then filtering, washing and drying to obtain an activated carbon loaded with silver ions adsorbent; (2) dispersing the activated carbon loaded with silver ions adsorbent in deionized water to form a suspension, then adding sodium alginate into the suspension, and stirring to obtain a mixture, adding the mixture into a calcium salt solution for cross-linking reaction, and then spray drying to obtain sodium alginate-coated activated carbon loaded with silver ions.

[0008] By adopting the above technical solution, the amino groups generated on the surface of activated carbon after plasma treatment form coordination bonds with silver ions, enhancing the stability and loading amount of silver; the porous structure of activated carbon provides physical retention space for silver, reducing agglomeration; the strong coordination effect (forming AgCl) between silver ions and chloride ions serves as the main driving force for adsorption, and the surface charge of aminated activated carbon can reduce the interference of other anions, improving the adsorption selectivity, and the electronic conjugation effect between silver and amino further enhances the binding energy of chloride ions; in addition, the improved surface polarity and hydrophilicity of plasma treatment promote the dispersion of the material in water and the contact efficiency with the silver-ammonia solution, ultimately realizing efficient and stable adsorption of chloride ions in water, with high removal rate, fast adsorption rate and cycle stability.

[0009] Preferably, in step (1), the pH of the suspension is adjusted to 8-10.

[0010] By adopting the above technical solution, by adjusting the pH of the suspension, the amino groups are partially protonated to form positively charged -NH3+ , combined with chloride ions through electrostatic adsorption, and the unprotonated amino group (-NH2) forms a coordination bond with the silver ions, which not only enhances the loading stability and loading amount of silver, but also the loaded silver ions can combine with chloride ions through coordination precipitation. The two significantly improve the adsorption effect of chloride ions through the synergistic mechanism of "electrostatic adsorption pre-enrichment + coordination effect deep fixation".

[0011] Preferably, in step (1), the power of the plasma treatment is 100-150 W, the time is 10-15 min, and the gas flow rate is 100-150 sccm.

[0012] By adopting the above technical solution, when the power is too low, the degree of amination is insufficient, and the number of electrostatic adsorption sites and coordination sites is small; when the power is too high, excessive etching of the activated carbon causes pore collapse, and high-energy particles may dehydrogenate the amino group to form imine, reducing the protonation ability.

[0013] When the treatment time is too short, the amination is insufficient, and the electrostatic adsorption and silver ion coordination sites are insufficient. When the treatment time is too long, the amino groups on the surface of the activated carbon are transitionally polymerized to form long chains, which block the micropores and reduce the adsorption effect of chloride ions. At the same time, the protonation efficiency of the long-chain amino groups is reduced due to steric hindrance.

[0014] When the gas flow rate is too low, the concentration of active particles is insufficient and the reaction rate is slow; when the gas flow rate is too high, the gas flows through the plasma zone quickly, and the active particles are taken out before they are fully reacted, resulting in amination efficiency reduction. In addition, the high-speed airflow may physically scour the surface of the activated carbon and destroy the pore structure.

[0015] In summary, this application can achieve the synergy of "highly active amino groups-ordered pore structure-appropriate charge density" on the surface of amino-activated carbon by regulating the above-mentioned parameters, and ultimately enhance the dual adsorption mechanism of "electrostatic pre-enrichment-deep coordination fixation" for chloride ions.

[0016] Preferably, in step (1), the mass volume ratio of the amino activated carbon to the silver nitrate solution is (1-10) g:1 L.

[0017] By adopting the above technical solution, the mass volume ratio of the amino activated carbon and the silver nitrate solution is optimized, and the silver ions can be evenly loaded in the form of single atoms or small molecular clusters by matching the silver ion loading amount with the amino active sites, so that the silver ions can be evenly loaded in the form of single atoms or small molecular clusters through the coordination of the amino groups with the silver ions. + -Cl - Coordination bond, which releases protons through coordination to promote the protonation of amino groups to generate -NH3 + , by electrostatic adsorption of Cl - Finally, the improvement of chloride ion adsorption effect is achieved through the synergistic mechanism of "coordination fixation-electrostatic pre-enrichment".

[0018] Preferably, in step (2), the mass ratio of the activated carbon-loaded silver ions to the sodium alginate is 1:(0.4-0.6).

[0019] By adopting the above technical solution, this ratio can not only enhance the mechanical strength of the composite material through the polysaccharide network of sodium alginate, but also utilize the coordination effect between the carboxyl groups in the sodium alginate molecules and the silver ions (similar to the coordination mechanism of the amino group) to further improve the loading stability and loading capacity of the silver ions; at the same time, the hydrophilic network of sodium alginate can promote the diffusion of chloride ions to the surface of the activated carbon, and the electrostatic field formed by its negatively charged carboxyl groups and protonated amino groups can coordinate the coordination and precipitation effect of silver ions and chloride ions. Under the multiple mechanisms of "network support-site coordination-diffusion enhancement", a balance between adsorption capacity and material practicality is achieved, and this ratio can avoid the problems of pore blockage or uneven dispersion of silver ions caused by excessive sodium alginate, taking into account both cost and performance optimization.

[0020] Preferably, in step (2), the mass ratio of sodium alginate to calcium salt is 1:(1-3).

[0021] By adopting the above technical solution to optimize the mass ratio of sodium alginate and calcium salt, the Ca 2+ The "egg-box structure" that forms moderate cross-linking with the carboxyl group of sodium alginate not only ensures the mechanical strength and pore diffusion performance of the material, but also uses the hydrophilic network of sodium alginate and the amino groups on the surface of activated carbon to synergistically form an electrostatic field to promote chloride ion enrichment. At the same time, the sodium alginate gel layer can protect the active sites of silver ions, improve adsorption stability and regeneration efficiency, and achieve a balance between mechanical properties and adsorption effects.

[0022] Preferably, the calcium salt is calcium chloride, calcium iodide, calcium dihydrogen phosphate or calcium nitrate, more preferably calcium chloride.

[0023] By adopting the above technical solution, calcium chloride is easily dissociated in aqueous solution to form Ca 2+ It can quickly form an "egg-box"-shaped cross-linked structure with the guluronic acid units on the sodium alginate chain, and the cross-linking reaction efficiency is high; the calcium chloride solution has a wide pH adaptability and can stably function in different acidic and alkaline systems; at the same time, it is inexpensive and easy to obtain, and as an essential electrolyte for organisms, it has extremely low toxicity and good biocompatibility; in addition, by adjusting the calcium chloride concentration, the hardness and network pore size of the gel can be precisely controlled, which makes the operation simple and the performance controllable.

[0024] Preferably, in step (2), the cross-linking reaction temperature is 20-50°C and the time is 30-90 minutes.

[0025] By adopting the above technical solution, the temperature and time during cross-linking affect the material properties by regulating the ion diffusion rate and the degree of cross-linking; specifically, increasing the temperature can accelerate the Ca 2+The cross-linking rate with the carboxyl group of sodium alginate can promote the uniform formation of the "egg-box structure" within an appropriate range, but if the temperature is too high, it will cause thermal degradation of sodium alginate and destroy the stability of the network; the cross-linking time needs to match the temperature conditions. A short time can easily lead to insufficient cross-linking and poor mechanical strength, while too long a time will cause local excessive cross-linking, resulting in a reduction in pore size and hindering ion diffusion.

[0026] In summary, optimizing the temperature and time during cross-linking can form an elastic network with appropriate porosity, taking into account both mass transfer efficiency and structural strength, and optimizing the chloride ion adsorption effect.

[0027] In a second aspect, the present application provides a method for preparing N2O, using the following technical solution: A method for preparing N2O is provided, which is obtained by thermally decomposing the above-mentioned ammonium nitrate solution.

[0028] By adopting the above technical solution, the present application reduces the chloride ion concentration in the ammonium nitrate solution, thereby enabling the ammonium nitrate to be dissolved under thermal decomposition conditions to safely produce N2O, thereby avoiding the occurrence of hazards such as explosion.

[0029] In summary, this application has at least one of the following beneficial technical effects: 1. This application uses sodium alginate-coated activated carbon loaded with silver ions as a chloride ion adsorbent. The chloride ions in the source water are adsorbed through the synergistic effect of the chemical reaction between silver ions and chloride ions and the physical adsorption of activated carbon, thereby improving the removal rate of chloride ions in the water and reducing the chloride ion concentration in the prepared ammonium nitrate solution. 2. In this application, silver ions are loaded on amino activated carbon, and the loaded silver ions can react with Cl - Generate precipitation; at the same time, by wrapping the activated carbon-loaded silver ion adsorbent in sodium alginate, not only the effective combination of the two is achieved, but also the dispersibility of the chloride ion adsorbent in water is improved, further improving the adsorption effect of chloride ions; 3. In this application, by adjusting the pH of the suspension, the amino group is partially protonated to form a positively charged -NH3 + , combined with chloride ions through electrostatic adsorption, and the unprotonated amino group (-NH2) forms a coordination bond with the silver ions, which not only enhances the loading stability and loading amount of silver, but also the loaded silver ions can combine with chloride ions through coordination precipitation. The two significantly improve the adsorption effect of chloride ions through the synergistic mechanism of "electrostatic adsorption pre-enrichment + coordination effect deep fixation". DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to the preparation examples and examples.

[0031] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are commonly available on the market.

[0032] Preparation Example 1 This preparation example discloses a preparation method of a chloride ion adsorbent, which is as follows: (1) Coconut shell activated carbon with a particle size of 20-60 mesh was placed in a radio frequency plasma device, the flow rate of ammonia was adjusted to 100 sccm, and plasma induction treatment was performed at a power of 150 W for 10 minutes to obtain amino activated carbon; 0.1 g of amino activated carbon was added to 20 ml of deionized water and the pH was adjusted to 8 by ammonia water and stirred evenly to obtain a suspension; ammonia water was added dropwise to 0.1 mol / L silver nitrate solution until the initial precipitate was dissolved to form a silver ammonia solution; the above suspension was added to 100 ml of silver ammonia solution, and the product was reacted at a temperature of 40 ° C for 60 minutes to obtain a filtered product, then washed with deionized water 3 times, and dried at 30 ° C to obtain an activated carbon-loaded silver ion adsorbent; (2) Add 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent into 100 ml of 4 wt% sodium alginate solution, stir and dissolve to obtain a mixed solution, add the mixed solution dropwise into 100 ml of 4 wt% calcium chloride solution and react at 20°C for 90 min. After spray drying, obtain sodium alginate-coated activated carbon loaded with silver ions.

[0033] Preparation Example 2 This preparation example is basically the same as Preparation Example 1, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 100 sccm, and performing plasma induction treatment at a power of 150 W for 10 min to obtain amino activated carbon; adding 0.1 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 9.5 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of silver ammonia solution, reacting at a temperature of 40°C for 60 min to obtain a product, filtering, washing with deionized water 3 times, and drying at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0034] Preparation Example 3 This preparation example is basically the same as Preparation Example 1, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 100 sccm, and performing plasma induction treatment at a power of 150 W for 10 min to obtain amino activated carbon; adding 0.1 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 10 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of silver ammonia solution, reacting at a temperature of 40°C for 60 min to obtain a product, filtering, washing with deionized water 3 times, and drying at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0035] Preparation Example 4 This preparation example is basically the same as Preparation Example 2, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 120 sccm, and performing plasma induction treatment at a power of 130 W for 12 minutes to obtain amino activated carbon; adding 0.1 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 9.5 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of silver ammonia solution, reacting at a temperature of 40°C for 60 minutes to obtain a product, filtering, washing with deionized water three times, and drying at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0036] Preparation Example 5 This preparation example is basically the same as Preparation Example 2, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 150 sccm, and performing plasma induction treatment at a power of 100 W for 15 min to obtain amino activated carbon; adding 0.1 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 9.5 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of silver ammonia solution, reacting at a temperature of 40°C for 60 min to obtain a product, filtering, washing with deionized water 3 times, and drying at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0037] Preparation Example 6 This preparation example is basically the same as Preparation Example 4, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 120 sccm, and performing plasma induction treatment at a power of 130 W for 12 minutes to obtain amino activated carbon; adding 0.5 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 9.5 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of silver ammonia solution, reacting at a temperature of 40°C for 60 minutes to obtain a product, filtering, washing with deionized water three times, and drying at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0038] Preparation Example 7 This preparation example is basically the same as Preparation Example 4, except that, step (1): placing coconut shell activated carbon with a particle size of 20-60 mesh in a radio frequency plasma device, adjusting the flow rate of ammonia to 120 sccm, and performing plasma induction treatment at a power of 130 W for 12 minutes to obtain amino activated carbon; adding 1 g of amino activated carbon to 20 ml of deionized water and adjusting the pH to 9.5 with ammonia water and stirring to obtain a suspension; adding ammonia water dropwise to a 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; adding the above suspension to 100 ml of the silver ammonia solution, reacting at a temperature of 40°C for 60 minutes to obtain a product, filtering it, washing it with deionized water three times, and drying it at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0039] Preparation Example 8 This preparation example is basically the same as Preparation Example 6, except that, in step (2), 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent is added to 100 ml of 5 wt % sodium alginate solution, stirred and dissolved to obtain a mixed solution, the mixed solution is added dropwise to 100 ml of 4 wt % calcium chloride solution and reacted at 20° C. for 90 min, and spray-dried to obtain sodium alginate-coated activated carbon loaded with silver ions.

[0040] Preparation Example 9 This preparation example is basically the same as Preparation Example 6, except that, in step (2), 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent is added to 100 ml of 6 wt % sodium alginate solution, stirred and dissolved to obtain a mixed solution, the mixed solution is added dropwise to 100 ml of 4 wt % calcium chloride solution and reacted at 20° C. for 90 min, and spray-dried to obtain sodium alginate-coated activated carbon loaded with silver ions.

[0041] Preparation Example 10 This preparation example is basically the same as Preparation Example 8, except that in step (2), 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent is added to 100 ml of 5 wt % sodium alginate solution, stirred and dissolved to obtain a mixed solution, and the mixed solution is added dropwise to 100 ml of 10 wt % calcium chloride solution to react at 20° C. for 90 min, and spray-dried to obtain sodium alginate-coated activated carbon loaded with silver ions.

[0042] Preparation Example 11 This preparation example is basically the same as Preparation Example 8, except that in step (2), 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent is added to 100 ml of 5 wt % sodium alginate solution, stirred and dissolved to obtain a mixed solution, and the mixed solution is added dropwise to 100 ml of 15 wt % calcium chloride solution to react at 20° C. for 90 min, and spray-dried to obtain sodium alginate-coated activated carbon loaded with silver ions.

[0043] Preparation Example 12 This preparation example discloses a method for preparing ammoniated activated carbon, which is as follows: Coconut shell activated carbon with a particle size of 20-60 mesh was placed in a radio frequency plasma device, the flow rate of ammonia was adjusted to 100 sccm, and plasma induction treatment was performed at a power of 150 W for 10 minutes to obtain amino activated carbon.

[0044] Preparation Example 13 This preparation example discloses a method for preparing activated carbon loaded with silver ions, which is as follows: 0.1 g of coconut shell activated carbon with a particle size of 20-60 mesh was added to 20 ml of deionized water to obtain a suspension; ammonia water was added dropwise to a 0.1 mol / L silver nitrate solution until the initially generated precipitate dissolved to form a silver ammonia solution; the above suspension was added to 100 ml of the silver ammonia solution, reacted at a temperature of 40° C. for 60 min, the obtained product was filtered, washed three times with deionized water, and dried at 30° C. to obtain an activated carbon-loaded silver ion adsorbent.

[0045] Preparation Example 14 This preparation example discloses a preparation method of a chloride ion adsorbent, which is as follows: (1) 0.1 g of coconut shell activated carbon with a particle size of 20-60 mesh was added to 20 ml of deionized water and the pH was adjusted to 8 by ammonia water and stirred to obtain a suspension; ammonia water was added dropwise to a 0.1 mol / L silver nitrate solution until the initially generated precipitate was dissolved to form a silver ammonia solution; the above suspension was added to 100 ml of the silver ammonia solution, reacted at 40 ° C for 60 min, the obtained product was filtered, washed with deionized water 3 times, and dried at 30 ° C to obtain an activated carbon-loaded silver ion adsorbent; (2) Add 10 g of the above-mentioned activated carbon-loaded silver ion adsorbent into 100 ml of 4 wt% sodium alginate solution, stir and dissolve to obtain a mixed solution, add the mixed solution dropwise into 100 ml of 4 wt% calcium chloride solution and react at 20°C for 90 min. After spray drying, obtain sodium alginate-coated activated carbon loaded with silver ions.

[0046] Preparation Example 15 This preparation example discloses a preparation method of a chloride ion adsorbent, which is as follows: Coconut shell activated carbon with a particle size of 20-60 mesh is placed in a radio frequency plasma device, the flow rate of ammonia is adjusted to 100 sccm, and plasma induction treatment is performed at a power of 150 W for 10 minutes to obtain amino activated carbon; 0.1 g of amino activated carbon is added to 20 ml of deionized water and the pH is adjusted to 8 by ammonia water and stirred evenly to obtain a suspension; ammonia water is added dropwise to a 0.1 mol / L silver nitrate solution until the initially generated precipitate is dissolved to form a silver ammonia solution; the above suspension is added to 100 ml of the silver ammonia solution, and the product obtained by reacting at a temperature of 40°C for 60 minutes is filtered, washed with deionized water three times, and dried at 30°C to obtain an activated carbon-loaded silver ion adsorbent.

[0047] Zeta potential test 0.01 g of each of the activated carbon loaded with silver ions obtained in Preparation Examples 1-3 and 12 and the amino activated carbon obtained in Preparation Example 13 was added to 0.1 L of deionized water and ultrasonically dispersed for 10 min to obtain a suspension. The pH of each suspension was adjusted to 2, 4, 6, 8, 10 and 12 using 0.1 M HCl or 0.1 M NaOH solution, and then allowed to stand for 10 min. The Zeta potential of each pH point was measured at 25°C using a Zeta potential meter. The measurement was repeated 3 times for each sample and the average value was taken. The test results are recorded in Table 1.

[0048] Table 1 Performance test data of preparation examples 1-3, 12 and 13

[0049] Referring to Table 1, combined with Preparation Examples 1, 12 and 13, it can be seen that the potential of Preparation Examples 1 and 12 decreases with the increase of pH, and Zeta=0 exists between pH 8-10, which is consistent with the pKa characteristics of amino groups, while Preparation Example 13 does not change much with the increase of pH, indicating that the activated carbon loaded with silver ions prepared in Preparation Example 1 has amino protonated NH3 + .

[0050] With reference to Table 1, it can be seen from the preparation examples 1-3 that the activated carbon-supported silver ions prepared by adjusting the pH of the suspension to 8-10 in the present application all contain protonated NH3+. In particular, as the pH of the suspension increases, the amino groups in the activated carbon-supported silver ions protonate NH3+.+ The less.

[0051] Example 1

[0052] This embodiment discloses a method for purifying chloride ions in an ammonium nitrate solution, which specifically comprises the following steps: S1, treating the source water with a reverse osmosis membrane to obtain a pre-treated liquid, adding the chloride ion adsorbent to the pre-treated liquid at a solid-liquid ratio of 1:1 (g:L), reacting and filtering to obtain desalted water; S2, reacting ammonia with oxygen to generate nitrogen oxides, which react with desalted water in a countercurrent collision reaction in an absorption tower to generate 58 wt% dilute nitric acid; the 58 wt% dilute nitric acid reacts with ammonia generated by vaporization of liquid ammonia to generate a neutralization reaction, which is then evaporated and concentrated to obtain an ammonium nitrate solution.

[0053] Among them, the chloride ion adsorbent comes from Preparation Example 1, and the source water comes from Lihe River.

[0054] This embodiment also discloses a method for preparing N2O, specifically, the method comprises: decomposing the above-mentioned ammonium nitrate solution at 250°C to produce N2O.

[0055] Example 2

[0056] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 2.

[0057] Example 3

[0058] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 3.

[0059] Example 4

[0060] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 4.

[0061] Example 5

[0062] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 5.

[0063] Example 6

[0064] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 6.

[0065] Example 7

[0066] This embodiment is basically the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 7.

[0067] Example 8

[0068] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 8.

[0069] Example 9

[0070] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 9.

[0071] Example 10

[0072] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 10.

[0073] Example 11

[0074] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 11.

[0075] Example 12

[0076] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 12.

[0077] Example 13

[0078] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 13.

[0079] Example 14

[0080] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 14.

[0081] Example 15

[0082] This example is essentially the same as Example 1, except that the chloride ion adsorbent is from Preparation Example 15.

[0083] Comparative Example 1 This example discloses a preparation method of an ammonium nitrate solution, specifically comprising the following steps: S1, desalted water is obtained by treating source water through a reverse osmosis membrane; S2, nitrogen oxides are generated by reacting ammonia gas with oxygen, and the nitrogen oxides are reacted with the desalted water in an absorption tower to generate 58wt% dilute nitric acid; the 58wt% dilute nitric acid is neutralized with ammonia gas generated by gasification of liquid ammonia, and is evaporated and concentrated to obtain an ammonium nitrate solution.

[0084] Performance detection test The same mass of the ammonium nitrate solutions and source water obtained in each embodiment and comparative example was weighed, and the chloride ion concentration thereof was determined according to the "Water Quality - Determination of Chloride - Silver Nitrate Titration Method" (GB11896). The results are shown in Table 2.

[0085] Table 2 Performance test data of Examples 1-15 and Comparative Example 1

[0086] Referring to Table 2, in combination with Example 1 and Comparative Example 1, it can be seen that the present application purifies the source water used in the preparation process of ammonium nitrate by using sodium alginate-coated activated carbon loaded with silver ions as a chloride ion adsorbent, and adsorbs the chloride ions in the source water through the synergistic effect of the chemical reaction between the silver ions and the chloride ions and the physical adsorption of the activated carbon; at the same time, the excellent adhesion properties of sodium alginate are utilized to adsorb it to the surface of the activated carbon loaded with silver ions. The good hydrophilicity of sodium alginate gives the activated carbon loaded with silver ions excellent water dispersibility, thereby improving its adsorption of chloride ions in water and reducing the chloride ion concentration in the source water, so that the chloride ion concentration in the prepared ammonium nitrate solution is purified.

[0087] Referring to Table 2, combined with Examples 1-3, it can be seen that by adjusting the pH of the suspension, the amino group is partially protonated to form a positively charged -NH3 + , combined with chloride ions through electrostatic adsorption, and the unprotonated amino group (-NH2) forms a coordination bond with the silver ions, which not only enhances the loading stability and loading amount of silver, but also the loaded silver ions can combine with chloride ions through coordination precipitation. The two significantly improve the adsorption effect of chloride ions through the synergistic mechanism of "electrostatic adsorption pre-enrichment + coordination effect deep fixation".

[0088] Referring to Table 2, in combination with Examples 1 and 14, it can be seen that after the activated carbon is treated with plasma, the amino groups generated on its surface form coordination bonds with silver ions, thereby enhancing the loading stability and loading capacity of silver. At the same time, the porous structure of the activated carbon provides a physical retention space for silver, reducing agglomeration; the strong coordination effect between silver ions and chloride ions (generating AgCl) is the main driving force for adsorption, and the surface charge of the amino-activated carbon can reduce the interference of other anions and improve the adsorption selectivity, and the electronic conjugation effect of silver and amino groups further enhances the binding energy of chloride ions; in addition, the surface polarity and hydrophilicity enhanced by the plasma treatment promote the dispersion of the material in water and the contact efficiency with the silver ammonia solution, ultimately synergistically achieving efficient and stable adsorption of chloride ions in water.

[0089] Referring to Table 2, combined with Examples 1 and 15, it can be seen that the present application utilizes the excellent adhesion properties of sodium alginate and coats it on the surface of activated carbon. The good hydrophilicity of sodium alginate gives the activated carbon-loaded silver ions excellent water dispersibility, thereby further improving the adsorption effect of the chloride ion adsorbent.

[0090] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for purifying chloride ions in ammonium nitrate solution, characterized in that: The following steps are involved: S1, after the source water is subjected to reverse osmosis to remove impurities, a chloride ion adsorbent is added to obtain desalted water; ammonia and oxygen are reacted to produce nitrogen oxides, and the nitrogen oxides react with the desalted water to produce dilute nitric acid; S2, liquid ammonia is vaporized to generate ammonia gas, which reacts with the dilute nitric acid to produce a high-concentration ammonium nitrate solution after evaporation; The chloride ion adsorbent is sodium alginate-coated activated carbon loaded with silver ions.

2. The method for purifying chloride ions in ammonium nitrate solution according to claim 1, wherein The preparation method of the chloride ion adsorbent comprises the following steps: (1) Plasma-treating activated carbon under nitrogen-containing gas to obtain amino-activated carbon; adding the amino-activated carbon to water and stirring to obtain a suspension; adding silver nitrate solution to ammonia water until the initially generated precipitate dissolves to form a silver-ammonia solution; adding the suspension to the silver-ammonia solution, reacting at 40-60° C. for 30-60 minutes, filtering, washing, and drying to obtain an activated carbon-loaded silver ion adsorbent; (2) The activated carbon loaded silver ion adsorbent is dispersed in deionized water to form a suspension, and then sodium alginate is added to the suspension and stirred to obtain a mixture. The mixture is added to a calcium salt solution for cross-linking reaction, and spray-dried to obtain sodium alginate-coated activated carbon loaded with silver ions.

3. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (1), the pH of the suspension is adjusted to 8-10.

4. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (1), the power of the plasma treatment is 100-150 W, the time is 10-15 min, and the gas flow rate is 100-150 sccm.

5. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (1), the mass volume ratio of the amino activated carbon to the silver nitrate solution is (1-10) g:1 L.

6. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (2), the mass ratio of the activated carbon-loaded silver ions to the sodium alginate is 1:(0.4-0.6).

7. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (2), the mass ratio of sodium alginate to calcium salt is 1:(1-3).

8. The method for purifying chloride ions in ammonium nitrate solution according to claim 7, wherein: The calcium salt is calcium chloride, calcium iodide, calcium dihydrogen phosphate or calcium nitrate.

9. The method for purifying chloride ions in ammonium nitrate solution according to claim 2, wherein: In step (2), the cross-linking reaction temperature is 20-50°C and the time is 30-90 minutes.

10. A method for preparing N2O, characterized in that: include: The ammonium nitrate solution is thermally decomposed to obtain the product.

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