Metal ion removal method based on ammonium bicarbonate

Abstract

The invention discloses a metal ion removal method based on ammonium bicarbonate. The method comprises the following steps: S1, pretreating raw material gas and stronger ammonia water after desulfurization of synthetic ammonia; s2, mixing the raw material gas pretreated in the step S1, stronger ammonia water and CO2 to obtain an ammonium bicarbonate suspension, and filtering; s3, adjusting the pH value, adding a masking agent and a precipitating agent into the solution under a stirring condition, mixing, and filtering to obtain an ammonium bicarbonate solution; and S4, adjusting the pH value of the ammonium bicarbonate solution in S3, decolorizing, and dehydrating to obtain an ammonium bicarbonate product. According to the method for removing the metal ions in the ammonium bicarbonate production process, through appropriate reaction conditions such as appropriate temperature, time and pressure control, and selection of an efficient adsorption material and combination of a masking agent and a precipitating agent, the metal ion removal effect can be ensured, and meanwhile the economical efficiency and feasibility of the whole technological process are also ensured.

Description

Technical Field

[0001] The present application relates to the technical field of ammonium bicarbonate purification, and in particular to a method for removing metal ions based on ammonium bicarbonate. Background Art

[0002] Ammonium bicarbonate (NH4HCO3), also known as ammonium carbonate, is an important chemical raw material, widely used in agriculture, medicine, food and other industries. It can be used not only as a fertilizer, but also as a fermentation agent, leavening agent, etc. However, in the production process of ammonium bicarbonate, due to various factors such as raw materials, equipment materials and reaction conditions, metal ions such as Fe 2+ Mg 3+ , Ca 2+ and Na + Etc., wastewater, these metal ions will not only pollute the environment, but also affect the purity and quality of the product.

[0003] At present, the main methods for removing metal ions from ammonium bicarbonate include physical separation, chemical precipitation, ion exchange, etc. Although physical separation methods such as filtration and distillation can remove some impurities to a certain extent, they have limited effect on metal ions dissolved in the solution; chemical precipitation is to convert metal ions into insoluble substances by adding specific precipitants, but this method often has problems such as long precipitation time, incomplete precipitation, and difficult separation of products; ion exchange utilizes the specific selectivity of ion exchange resins to exchange metal ions in the solution with ions on the resin, thereby achieving the purpose of removing metal ions. Although this method has the advantages of high selectivity, good removal effect, and easy operation, the resin selectivity is limited, the exchange capacity is insufficient, and the regeneration efficiency is also low.

[0004] Based on this, there is an urgent need to explore a method that can improve the removal efficiency and effect of metal ions in the production process of ammonium bicarbonate, which is low-cost and easy to operate, so as to achieve green and efficient production of ammonium bicarbonate. Summary of the invention

[0005] In order to solve at least one of the above technical problems, the present invention provides a method for removing metal ions based on ammonium bicarbonate, which fully utilizes the ability of ammonium bicarbonate to form stable compounds with metal ions under specific conditions, thereby achieving effective capture and removal of metal ions.

[0006] On the one hand, the present application provides a method for removing metal ions based on ammonium bicarbonate, the method comprising the following steps:

[0007] S1. Pre-treating the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia;

[0008] S2, mixing the raw gas pretreated in S1, concentrated ammonia water and CO2 to obtain an ammonium bicarbonate suspension, and filtering;

[0009] S3, adjusting the pH value, adding a masking agent and a precipitant to the solution under stirring, mixing, and filtering to obtain an ammonium bicarbonate solution;

[0010] S4, adjusting the pH value of the ammonium bicarbonate solution of S3, decolorizing and dehydrating to obtain an ammonium bicarbonate product.

[0011] Firstly, the method uses the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia as starting materials. These materials are usually by-products or wastes in the chemical production process. Through the method, they can be reused, reducing resource waste.

[0012] Secondly, by adding masking agents and precipitants to the product, this method can remove specific metal ions in a targeted manner and improve the removal efficiency. Compared with the traditional chemical precipitation method, the masking agents and precipitants used in this method are relatively mild, and no new harmful substances are introduced during the entire process, reducing the risk of secondary pollution and reducing safety hazards. At the same time, the formed precipitate is easy to separate and handle, reducing the difficulty and cost of handling.

[0013] By adopting the above technical solution, this method not only provides an effective means of removing metal ions, but also shows obvious advantages in resource recycling, environmental protection, economic benefits, etc., and has good application prospects.

[0014] Optionally, in S1, the pretreatment specifically includes: preliminary filtering of the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia; and adsorbing the filtered raw gas and concentrated ammonia water with an adsorption material.

[0015] Preliminary filtration can remove large particle impurities in the raw gas and concentrated ammonia, such as dust, rust, etc.; adsorption can further remove trace impurities in the raw gas and concentrated ammonia, such as organic matter, sulfide, etc. By adopting the above technical solution, removing impurities can not only reduce the unstable factors that may appear in the subsequent production process and improve the stability of the process; it can also improve the purity of the raw materials, thereby improving the quality of the final product. At the same time, preliminary filtration can prevent large particle impurities from entering subsequent equipment and avoid clogging pipelines and reactors. By removing impurities, the reaction efficiency of ammonia and carbon dioxide can be improved, the reaction speed can be accelerated, and impurity removal can reduce the occurrence of side reactions and increase the yield of the target product.

[0016] Optionally, the adsorbent material is selected from a material with a specific surface area of ​​300 to 680 m 2 / g, activated carbon with a pore size of 0.1 to 10 nm.

[0017] By adopting the above technical solution, the activated carbon has a larger specific surface area, which also means that it has more adsorption sites and can adsorb more impurities. Its pore size can selectively adsorb target impurities, including some organic matter and some metal ions. Activated carbon has good chemical stability and can be used in a wide pH range. It is not easy to react chemically with the adsorbate, and its cost is relatively low. It can be reused through regeneration treatment and has good economic efficiency.

[0018] Optionally, in S2, the mixing temperature is 30-50°C, the time is 30-45 min, and the pressure is 0.5-2 MPa.

[0019] By adopting the above technical solution, under the above temperature conditions, the reaction can be carried out efficiently and energy consumption can be reduced; too high temperature may affect the main reaction and increase energy consumption and cost; low temperature will reduce the reaction rate and prolong the reaction time. Controlling the reaction time to 30-45 minutes and the pressure to 0.5-2MPa can not only ensure that the raw gas, concentrated ammonia water and carbon dioxide are fully mixed and improve the uniformity of the reaction, but also ensure the solubility of ammonia and carbon dioxide, increase the reaction rate, ensure the safe operation of the equipment, and reduce the risks brought by high pressure.

[0020] Optionally, in S3, the pH value is adjusted in the range of 9 to 10.

[0021] By adopting the above technical solution, the precipitation of metal ions can be effectively promoted while ensuring the safety and economy of the process, thereby achieving a better metal ion removal effect.

[0022] Optionally, in S3, the masking agent is selected from one of sodium sulfite, sodium citrate, sodium thiosulfate or sodium oxalate; and the precipitant is EDTA.

[0023] By adopting the above technical solution and selecting the appropriate masking agent, the interference of certain metal ions can be effectively avoided, ensuring that the precipitant (such as EDTA) can specifically act on the target metal ions. This not only improves the efficiency of metal ion removal, but also ensures the purity of the final product. At the same time, choosing an environmentally friendly and easy-to-handle masking agent also helps reduce the impact on the environment.

[0024] Further preferably, the molar ratio of the masking agent to the precipitating agent is 1:(2-5).

[0025] By adopting the above technical solution, the masking agent can preferentially form a complex with those metal ions that may interfere with the precipitation reaction, thereby improving the selectivity of the precipitant for the target metal ions. In addition, precipitants (such as EDTA) are usually expensive reagents, and excessive use will increase costs. By controlling the molar ratio of the masking agent to the precipitant within the range of 1: (2 to 5), it can be ensured that the amount of precipitant is more reasonable and unnecessary waste can be avoided. This not only reduces costs, but also improves the economic benefits of the process.

[0026] Optionally, in S3, the mixing temperature is 30-50° C. and the mixing time is 30-60 min.

[0027] Further preferably, in S3, the filtration includes solid-liquid separation and membrane separation; and the membrane material is a polyamide reverse osmosis membrane.

[0028] By adopting the above technical solutions, the combined use of solid-liquid separation and membrane separation can significantly improve the separation efficiency. Solid-liquid separation can first remove most of the solid particles, while membrane separation can further remove fine particles and dissolved substances to ensure the purity of the final product. In addition, the polyamide reverse osmosis membrane has good selectivity and can effectively intercept substances of a specific molecular weight. This means that it can block most metal ions and other impurities, while allowing water and other small molecules to pass through, thereby improving the purity of the product. Compared with traditional filtration methods, membrane separation technology usually consumes less energy, especially when processing large amounts of solution, which can save a lot of energy consumption. The working pressure of the polyamide reverse osmosis membrane is relatively low, which further reduces energy demand.

[0029] Optionally, in S4, the pH value is adjusted in the range of 7 to 8.

[0030] By adopting the above technical solution, it is helpful to maintain the stability of ammonium bicarbonate. In this pH range, ammonium bicarbonate is not easy to decompose, which is conducive to subsequent storage and transportation. In a neutral or slightly alkaline environment, decolorization and dehydration are easier. Decolorizers such as activated carbon are more effective at a pH value close to neutral, and it is not easy to introduce new impurities during the dehydration process.

[0031] In summary, the present invention includes at least one of the following beneficial technical effects:

[0032] The method adopted by the present invention is to pre-treat the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia, and mix them with carbon dioxide (CO2) to generate an ammonium bicarbonate suspension. Then, by adjusting the pH value and adding appropriate masking agents and precipitants, the reaction between metal ions and ammonium bicarbonate is promoted to form a precipitate that is easy to separate. This method can not only effectively remove metal ions in wastewater, but also recycle the generated ammonium bicarbonate, thereby reducing the overall treatment cost.

[0033] The method for removing metal ions in the ammonium bicarbonate production process of the present invention can ensure the metal ion removal effect while ensuring the economy and feasibility of the entire process flow through appropriate reaction conditions, such as suitable temperature, time and pressure control, and selection of efficient adsorption materials and masking agents, precipitants combination.

[0034] The ammonium bicarbonate product prepared by the invention has high purity and is suitable for meeting the high quality requirements of industries such as rare earth refining, metal smelting, and new energy batteries. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The present application designs a method for removing metal ions based on ammonium bicarbonate, the method comprising the following steps:

[0037] S1. Pre-treating the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia;

[0038] In the embodiment of the present invention, the raw gas and concentrated ammonia water are both from the synthetic ammonia production process. The raw gas after desulfurization of synthetic ammonia mainly comes from the steps of cracking, conversion, desulfurization and purification, the purpose of which is to obtain high-purity hydrogen and nitrogen for synthetic ammonia; and concentrated ammonia water is obtained by dissolving ammonia in water or recovering ammonia gas, a by-product of the synthetic ammonia production process. Among them, synthetic ammonia can be obtained by cracking or gasifying raw materials such as natural gas, petroleum or coal, and then collected through the water-gas shift reaction; in order to avoid the impact of sulfides on subsequent processes or production environment, synthetic ammonia needs to be desulfurized, and the desulfurization treatment includes but is not limited to one or more of physical solvent (such as methanol) absorption, chemical absorption (such as alcohol amine solution), dry desulfurization or wet desulfurization; the present invention uses clean reaction raw materials as much as possible, and at least two or more methods are used for desulfurization.

[0039] S2, mixing the raw gas pretreated in S1, concentrated ammonia water and CO2 to obtain an ammonium bicarbonate suspension, and filtering;

[0040] In an embodiment of the present invention, in step S2, the raw gas pretreated in S1, concentrated ammonia water and carbon dioxide (CO2) are mixed in a certain ratio, and the specific ratio is determined according to the concentration of the ammonia water and the mass of the ammonium bicarbonate to be generated. Usually, in a reactor or a mixer, at a temperature of 30 to 50° C. and a pressure of 0.5 to 2 MPa, stirring is continued for 30 to 45 minutes to allow the ammonia water and carbon dioxide to fully react to generate an ammonium bicarbonate suspension; then, solid-liquid separation is performed through a filtering device (such as a filter or a filter) to separate the ammonium bicarbonate solid, thereby obtaining a pure ammonium bicarbonate suspension, which is prepared for the subsequent metal ion removal step.

[0041] S3, adjusting the pH value, adding a masking agent and a precipitant to the solution under stirring, mixing, and filtering to obtain an ammonium bicarbonate solution;

[0042] S4, adjusting the pH value of the ammonium bicarbonate solution of S3, decolorizing and dehydrating to obtain an ammonium bicarbonate product.

[0043] In an embodiment of the present invention, it is first necessary to adjust the pH value of the ammonium bicarbonate solution obtained in step S3 to within the range of 7 to 8 to improve the stability of the product and reduce the formation of by-products. The specific operation is to use a pH meter to monitor the pH value of the solution in real time, and gradually add dilute hydrochloric acid (HCl) until the target pH value is reached; Next, a decolorization treatment is performed, and the color and other organic impurities in the solution are removed by using an activated carbon filter column or other adsorbent materials, and the ammonium bicarbonate solution with a good pH value is passed through an activated carbon filter column to adsorb and remove the color and other organic impurities in the solution; Finally, a dehydration treatment is performed, and a dryer is used to remove moisture. The specific operation is to send the decolorized ammonium bicarbonate solution into a dryer and perform a dehydration treatment at a suitable temperature until a dry ammonium bicarbonate solid is obtained to ensure the purity and stability of the product. In the entire preparation process, in order to avoid the formation of by-products caused by excessive acid or alkali, the adsorption effect of activated carbon is regularly checked, and the activated carbon is replaced when necessary. At the same time, the temperature during the dehydration process is controlled to avoid excessive temperature causing the decomposition of ammonium bicarbonate, and quality inspection is performed after the final product is completed to ensure that the product meets the expected standards.

[0044] The present application further optimizes the processing of step S1, and the pretreatment specifically includes: preliminary filtering of the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia; and using adsorption materials to adsorb the filtered raw gas and concentrated ammonia water.

[0045] The present application further optimizes the processing in step S3, wherein the filtration includes solid-liquid separation and membrane separation; and the membrane material is a polyamide reverse osmosis membrane.

[0046] In an embodiment of the present invention, in order to further improve the purity of the ammonium bicarbonate solution, the filtration process includes two stages: solid-liquid separation and membrane separation; first, solid-liquid separation is performed, and solid particles in the solution are removed by a filtration device (such as a centrifuge or a filter press) to ensure that most of the solid impurities in the solution are effectively separated; then membrane separation is performed, and fine particles, dissolved impurities and metal impurities in the solution are further removed using a polyamide reverse osmosis membrane. The polyamide reverse osmosis membrane has good selectivity and stability, and can effectively intercept metal ions (including but not limited to monovalent or divalent metal ions, such as Na + , Fe 2+ , Fe 3+ , Ca 2+ Mg 2+ etc.) and other impurities, while allowing pure ammonium bicarbonate solution to pass through, thereby ensuring the high purity and stability of the final product; through these two steps of filtration treatment, the quality of the ammonium bicarbonate product can be significantly improved, the impurity content can be reduced, and the smooth progress of subsequent processing can be ensured.

[0047] Based on the above method, the inventors also proposed that the molar ratio of the masking agent to the precipitating agent is 1:(2-5).

[0048] In the embodiment of the present invention, in order to further optimize the removal effect of metal ions, the inventors proposed that the molar ratio of the masking agent to the precipitant (such as EDTA) is 1: (2-5). Specifically, when the pH value is adjusted and the masking agent (such as sodium sulfite, sodium citrate, sodium thiosulfate or sodium oxalate) and the precipitant (such as EDTA) are added to the solution under stirring conditions, the molar ratio of the masking agent to the precipitant is controlled within the range of 1: (2-5).

[0049] The invention provides an efficient method for removing metal ions, which can not only effectively remove metal ions in wastewater, but also recycle generated ammonium bicarbonate, thereby reducing the overall treatment cost; the method improves the removal efficiency of metal ions by selecting appropriate masking agents and precipitants, and no new harmful substances are introduced in the entire process, reducing the risk of secondary pollution, and also reduces energy consumption by optimizing reaction conditions (such as temperature, time, pressure, etc.); the raw gas and concentrated ammonia water after synthetic ammonia desulfurization are used as starting materials, thereby achieving maximum utilization of resources, and reducing the treatment cost by reasonably controlling the ratio of masking agents to precipitants and adopting economical adsorption materials; the process flow is simple and easy to implement, which ensures the metal ion removal effect while also ensuring the economy and feasibility of the entire process flow; in short, the invention provides an innovative method for removing metal ions, which not only overcomes the deficiencies in the prior art, but also realizes the recycling of resources, has significant economic and social benefits, and is of great significance for promoting the sustainable development of the chemical industry.

[0050] The present invention is further described below in conjunction with specific examples, and the protection scope of the present invention is not limited by the following examples. The sources of materials mainly involved in the examples are all conventional commercial products.

[0051] The product performance test of the ammonium bicarbonate prepared in the following example includes:

[0052] (1) Product purity determination

[0053] The final product was sampled and analyzed for purity using high performance liquid chromatography (HPLC).

[0054] (2) Determination of metal ion removal rate

[0055] Samples were taken from the solution before and after adding the masking agent and the precipitant, and the metal ion concentration was analyzed using an atomic absorption spectrometer (AAS) instrument.

[0056] Example 1

[0057] S1. Preprocessing

[0058] Preliminary filtration: Use filters to remove large particle impurities in the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia;

[0059] Adsorption treatment: using a specific surface area of ​​500m 2 / g, activated carbon with a pore size of 1.5nm adsorbs the filtered raw gas and concentrated ammonia water;

[0060] S2, mixing the pretreated raw gas, concentrated ammonia water and carbon dioxide (CO2) at a mixing temperature of 40° C. and a pressure of 1.5 MPa for 40 minutes to form an ammonium bicarbonate suspension, and performing solid-liquid separation through a filter to separate the solid;

[0061] S3, adjusting the pH value of the separated ammonium bicarbonate solution to 10, adding a masking agent (sodium sulfite) to a precipitant (EDTA) at a molar ratio of 1:3 under stirring, mixing for 45 minutes, and mixing at a temperature of 40°C; after primary filtration through a filter, membrane separation is performed using a polyamide reverse osmosis membrane to obtain an ammonium bicarbonate solution;

[0062] S4. The pH value of the ammonium bicarbonate solution is adjusted to 8. The solution is decolorized by an activated carbon filter column, and then the water is removed by a dryer to obtain a pure ammonium bicarbonate product.

[0063] In this example, before adding the masking agent and the precipitant, the initial concentration of the metal ions is: Fe 2+ :100mg / L;Fe 3+ :100mg / L;Mg 2+ :80mg / L;Ca 2+:120mg / L;Na + :150mg / L;

[0064] After decolorization and dehydration in this embodiment, the final concentration of metal ions is: Fe 2+ :1.5mg / L;Fe 3+ :1.3mg / L;Mg 2+ :2.0mg / L; Ca 2+ :2.4mg / L;Na + :5.0mg / L.

[0065] The ammonium bicarbonate product prepared in this embodiment was analyzed:

[0066] Purity: 99.5%

[0067] Metal ion removal rate: Fe 2+ :98.5%; Fe 3+ :98.7%;Mg 2+ :97.8%;Ca 2+ :98.2%;Na + :96.5%.

[0068] Example 2

[0069] S1. Preprocessing

[0070] Preliminary filtration: Same as Example 1.

[0071] Adsorption treatment: using a specific surface area of ​​600m 2 / g, activated carbon with a pore size of 2nm adsorbs the filtered raw gas and concentrated ammonia water.

[0072] Steps S2-S4 are the same as those in Example 1.

[0073] After decolorization and dehydration in this embodiment, the final concentration of metal ions is: Fe 2+ :1.0mg / L;Fe 3+ :0.8mg / L;Mg 2+ :1.2mg / L;Ca 2+ :1.4mg / L;Na + :4.2mg / L.

[0074] The ammonium bicarbonate product prepared in this embodiment was analyzed:

[0075] Purity: 99.7%

[0076] Metal ion removal rate: Fe 2+ :99.0%;Fe 3+ :99.2%;Mg 2+ :98.5%;Ca2+ :98.8%;Na + :97.2%.

[0077] Example 3

[0078] S1, pretreatment is the same as in Example 1;

[0079] S2, mixing the pretreated raw gas, concentrated ammonia water and carbon dioxide (CO2) at a mixing temperature of 35°C and a pressure of 1.0 MPa for 40 minutes to form an ammonium bicarbonate suspension, and performing solid-liquid separation by a filter to separate the solid;

[0080] Steps S3-S4 are the same as those in Example 1.

[0081] After decolorization and dehydration in this embodiment, the final concentration of metal ions is: Fe 2+ :0.4mg / L;Fe 3+ :1.0mg / L;Mg 2+ :0.6mg / L; Ca 2+ :0.6mg / L;Na + :4.5mg / L.

[0082] The ammonium bicarbonate product prepared in this embodiment was analyzed:

[0083] Purity: 99.6%

[0084] Metal ion removal rate: Fe 2+ :99.6%;Fe 3+ :99.0%;Mg 2+ :99.3%;Ca 2+ :99.5%;Na + :97.0%.

[0085] Example 4

[0086] Steps S1-S2 are the same as those in Example 1;

[0087] S3, adjusting the pH value of the separated ammonium bicarbonate solution to 9, adding a masking agent (sodium sulfite) to a precipitant (EDTA) at a molar ratio of 1:3 under stirring, mixing for 45 minutes, and mixing at a temperature of 40°C; after primary filtration through a filter, membrane separation is performed using a polyamide reverse osmosis membrane to obtain an ammonium bicarbonate solution;

[0088] S4. The pH value of the ammonium bicarbonate solution is adjusted to 7. The solution is decolorized by an activated carbon filter column and then dried to remove moisture to obtain a pure ammonium bicarbonate product.

[0089] After decolorization and dehydration in this embodiment, the final concentration of metal ions is: Fe2+ :1.0mg / L;Fe 3+ :0.8mg / L;Mg 2+ :1.2mg / L;Ca 2+ :1.4mg / L;Na + :4.0mg / L.

[0090] The ammonium bicarbonate product prepared in this embodiment was analyzed:

[0091] Purity: 99.4%

[0092] Metal ion removal rate: Fe 2+ :99.0%;Fe 3+ :99.2%;Mg 2+ :98.5%;Ca 2+ :98.8%;Na + :97.3%.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that no masking agent is used, and the other steps remain unchanged.

[0095] After decolorization and dehydration, the final concentration of metal ions is: Fe 2+ :8.0mg / L;Fe 3+ :8.8mg / L;Mg 2+ :7.5mg / L;Ca 2+ :7.2mg / L;Na + :18.4mg / L.

[0096] The ammonium bicarbonate product prepared in this comparative example was analyzed:

[0097] Purity: 96.2%

[0098] Metal ion removal rate: Fe 2+ :92.0%;Fe 3+ :91.2%;Mg 2+ :90.6%;Ca 2+ :94.0%;Na + :87.7%.

[0099] Comparative Example 2

[0100] The difference from Example 1 is that in S3, the solid-liquid separation is only performed by filtration, and membrane separation is not used; the other steps remain unchanged.

[0101] After decolorization and dehydration, the final concentration of metal ions is: Fe 2+ :9.2mg / L;Fe 3+:10.8mg / L;Mg 2+ :9.5mg / L;Ca 2+ :8.6mg / L;Na + :24.5mg / L.

[0102] The ammonium bicarbonate product prepared in this comparative example was analyzed:

[0103] Purity: 94.5%

[0104] Metal ion removal rate: Fe 2+ :90.8%;Fe 3+ :89.2%;Mg 2+ :88.1%;Ca 2+ :92.8%;Na + :83.7%.

[0105] By comparing the data of the embodiments and the comparative examples, it can be seen that the use of optimized adsorbent materials (Example 2), mixing conditions (Example 3) and pH adjustment range (Example 4) can significantly improve the purity and metal ion removal rate of the product. In particular, the use of masking agents (Examples 1-4) significantly improves the removal efficiency of metal ions compared to the case where no masking agent is used (Comparative Example 1), because: masking agents (such as sodium sulfite, sodium citrate, sodium thiosulfate or sodium oxalate) can form stable complexes with metal ions in solution, change the existence form of metal ions, reduce the number of interfering metal ions, and improve the selectivity of the precipitant and the completeness of the precipitation. These mechanisms of action jointly lead to the result that the masking agent significantly improves the removal efficiency of metal ions. In addition, membrane separation technology (Examples 1-4) also further improves the purity of the product compared to traditional filtration methods (Comparative Example 2).

[0106] In summary, the present invention can significantly improve the purity and metal ion removal rate of ammonium bicarbonate products by selecting appropriate adsorption materials, mixing conditions, the ratio of masking agent to precipitant and membrane separation technology, thereby ensuring the high quality of the final product.

[0107] Taking Example 1 as an example, the inventors further optimized the types of masking agent and precipitant in step 3, wherein the molar ratio of the masking agent to the precipitant is a fixed value of 1:3. The final test results are shown in Table 1 below.

[0108] Table 1 Performance test results

[0109] <![CDATA[Fe 2+ / %]]> <![CDATA[Fe3 + / %]]> <![CDATA[Mg 2+ / %]]> <![CDATA[Ca 2+ / %]]> <![CDATA[Na + / %]]> purity / % Example 1 98.5 98.7 97.8 98.2 96.5 99.5 Sodium sulfite + EDTA Example 5 98.0 982 98.2 97.8 97.4 98.7 Sodium citrate + EDTA Example 6 99.0 99.4 99.5 99.6 98.2 99.8 Sodium thiosulfate + EDTA Example 7 98.6 98.8 98.6 99.0 97.0 99.0 Sodium oxalate + EDTA

[0110] According to the above results, sodium thiosulfate + EDTA (Example 6) is the best combination of masking agent and precipitant, which can significantly improve the removal efficiency of metal ions, and the product purity is also very high. The inventor takes Example 6 as an example and designs Comparative Examples 3-4.

[0111] Comparative Example 3

[0112] Sodium phosphate + EDTA was selected, and the other steps remained unchanged.

[0113] The ammonium bicarbonate product prepared in this comparative example was analyzed:

[0114] Purity: 90.4%

[0115] Metal ion removal rate: Fe 2+ :85.0%;Fe 3+ :84.0%;Mg 2+ :80.0%;Ca 2+ :82.5%;Na + :81.0%.

[0116] Comparative Example 4

[0117] Sodium thiosulfate + sodium citrate was selected, and the other steps remained unchanged.

[0118] The ammonium bicarbonate product prepared in this comparative example was analyzed:

[0119] Purity: 85.0%

[0120] Metal ion removal rate: Fe 2+ :80.0%;Fe 3+ :79.0%;Mg 2+ :75.0%;Ca 2+ :77.5%;Na + :76.0%.

[0121] In combination with Example 6 and Comparative Example 3, sodium thiosulfate can effectively form a stable complex with metal ions when used in combination with EDTA as a masking agent, thereby reducing the interference between these metal ions and EDTA, allowing EDTA to better precipitate the target metal ions. Although sodium phosphate is also a masking agent, the complex stability it forms with metal ions is poor and cannot effectively reduce the impact of interfering metal ions. Therefore, when used in combination with EDTA, sodium phosphate is not as effective as sodium sulfite.

[0122] Combining Example 6 with Comparative Example 4, EDTA, as a powerful precipitant, has high selectivity and stability and can form stable complexes with a variety of metal ions. Although sodium citrate can also be used as a precipitant, its selectivity and stability are not as good as EDTA. Therefore, when used in combination with sodium thiosulfate, sodium citrate is not as effective as EDTA.

[0123] In summary, the masking agent and precipitant selected in the present invention have a synergistic effect and can effectively remove metal ions.

[0124] The inventors took Example 6 as an example, and determined the final purity and metal ion removal rate of the product by changing the molar ratio of the masking agent to the precipitant, and recorded them in Table 2 below.

[0125] Table 2 Performance test results

[0126]

[0127]

[0128] It can be seen from the performance test results of Table 2 that the combination of Example 6 shows the best synergistic effect, significantly improving the removal efficiency of metal ions and the purity of the product. In contrast, the metal ion removal rate of Comparative Example 5 is low and the purity is low. The possible reason is that when the molar ratio of the masking agent (sodium sulfite) to the precipitant (EDTA) is 1:1, the masking agent is excessive, resulting in the masking agent forming stable complexes with various metal ions. These complexes are difficult to completely remove during subsequent treatment, thereby affecting the removal rate of metal ions. At the same time, the amount of precipitant (EDTA) is insufficient and cannot effectively form a precipitate with all target metal ions. The metal ion removal rate of Comparative Example 6 is low and the purity is relatively low. The possible reason is that the excessive precipitant (EDTA) may further combine with the unmasked interfering ions, thereby affecting the removal rate of the target metal ions and the purity of the product.

[0129] In summary, when sodium thiosulfate is used as a masking agent in combination with EDTA, it can effectively form a stable complex with metal ions, reduce the interference of these metal ions on EDTA, and thus enable EDTA to better precipitate the target metal ions. At the same time, when the molar ratio of sodium thiosulfate to EDTA is further specified as 1:3, the combination exhibits the best synergistic effect, significantly improving the removal efficiency of metal ions and the purity of the product.

[0130] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for removing metal ions based on ammonium bicarbonate, characterized in that: The method comprises the following steps: S1. Pre-treating the raw gas and concentrated ammonia water after desulfurization of synthetic ammonia; S2, mixing the raw gas pretreated in S1, concentrated ammonia water and CO2 to obtain an ammonium bicarbonate suspension, and filtering; S3, adjusting the pH value, adding a masking agent and a precipitant to the solution under stirring, mixing, and filtering to obtain an ammonium bicarbonate solution; S4, adjusting the pH value of the ammonium bicarbonate solution of S3, decolorizing and dehydrating to obtain an ammonium bicarbonate product.

2. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S1, the preprocessing specifically includes: The raw gas and concentrated ammonia water after desulfurization of synthetic ammonia are initially filtered; the filtered raw gas and concentrated ammonia water are adsorbed by adsorption materials.

3. The method for removing metal ions based on ammonium bicarbonate according to claim 2, characterized in that: The adsorption material is selected from a material with a specific surface area of ​​300 to 680 m 2 / g, activated carbon with a pore size of 0.1 to 10 nm.

4. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S2, the mixing temperature is 30-50°C, the time is 30-45 minutes, and the pressure is 0.5-2 MPa.

5. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S3, the pH value is adjusted in the range of 9 to 10.

6. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S3, the masking agent is selected from one of sodium sulfite, sodium citrate, sodium thiosulfate or sodium oxalate; and the precipitating agent is EDTA.

7. The method for removing metal ions based on ammonium bicarbonate according to claim 6, characterized in that: The molar ratio of the masking agent to the precipitating agent is 1:(2-5).

8. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S3, the mixing temperature is 30-50°C and the mixing time is 30-60 minutes.

9. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S3, the filtration includes solid-liquid separation and membrane separation; and the membrane material is a polyamide reverse osmosis membrane.

10. The method for removing metal ions based on ammonium bicarbonate according to claim 1, characterized in that: In S4, the pH value is adjusted in the range of 7 to 8.

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