Method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide
Patent Information
- Application Number
- CN202610948158.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-29
- Publication Date
- 2026-08-28
AI Technical Summary
[0005]本发明提供了利用二氧化碳促进橄榄石还原硝酸盐生成碳酸氢铵的方法，克服了现有技术中“先制氨、再单独回收碳酸氢铵”的流程长、设备多、能耗高的问题
[0030] 1. Carbon dioxide is moved from the traditional downstream carbonization raw material to the upstream component of the entire process, thereby achieving the coupling of olivine activation, nitrate reduction, and in-situ fertilizer generation.
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Figure CN122646866A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of environmental governance, low-carbon chemical industry, mineral resource conversion and fertilizer technology, and in particular to a method for using carbon dioxide to promote the reduction of nitrates by olivine to produce ammonium bicarbonate. Background Technology
[0002] Nitrates are widely present in emission systems from chemical, metallurgical, explosives, fertilizer, electronics, and agricultural industries. Current technologies for nitrate resource recovery typically focus on electrochemical reduction to ammonia or denitrification to ammonia using metal reducing agents. On the other hand, olivine, a natural mineral rich in magnesium and ferrous iron, has been extensively studied for its use in carbon dioxide mineralization and the release of active components. Recent studies have further demonstrated that olivine can react with nitrate-containing systems to generate ammonia.
[0003] Meanwhile, the formation of ammonium bicarbonate from ammonia, carbon dioxide, and water is a mature chemical process. Most existing ammonium bicarbonate production technologies adopt a step-by-step process of "ammonia is first produced or recovered, and then enters the carbonization / heavy carbonization stage to produce ammonium bicarbonate." Because ammonium bicarbonate has poor thermal stability and is easily decomposed when heated, it usually requires low-temperature carbonization conditions.
[0004] However, the existing technology has not yet provided a one-step process that introduces carbon dioxide into the system from the start of the reaction, thereby simultaneously promoting olivine activation, nitrate reduction, and in-situ fixation of ammonia / ammonium, and directly obtaining ammonium bicarbonate fertilizer in the same reactor. Summary of the Invention
[0005] This invention provides a method for using carbon dioxide to promote the reduction of nitrates from olivine to produce ammonium bicarbonate, overcoming the problems of long processes, numerous equipment, and high energy consumption in the existing technology of "first producing ammonia and then separately recovering ammonium bicarbonate". Specifically, this is achieved through the following techniques.
[0006] The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide, provided by this invention, includes the following steps:
[0007] The olivine was crushed and pre-activated in sequence, and then added to an aqueous solution containing nitrates to form a reaction system.
[0008] Carbon dioxide or a gas containing carbon dioxide is introduced into the reaction system to carry out the reaction and form an ammonium bicarbonate system.
[0009] After the main reaction is completed, the ammonium bicarbonate system is treated by cooling and / or depressurization to form a solution, slurry or crystalline product of ammonium bicarbonate.
[0010] In the above-mentioned method provided by the present invention, the aqueous solution containing nitrate can be derived from any source such as industrial wastewater, groundwater, agricultural runoff concentrate, nitrate solution, nitric acid production tail liquid, etc.
[0011] Upon introduction of carbon dioxide or a gas containing carbon dioxide, the carbon dioxide promotes the release of the active components of olivine and the reduction of nitrates, while simultaneously coupling in situ with the ammonia or ammonium generated during the reaction to form an ammonium bicarbonate system. The generated ammonia / ammonium is not removed separately from the same system; instead, it couples in situ with the carbon dioxide / bicarbonate ions in the system to form ammonium bicarbonate. After the main reaction is completed, no separate ammonia recovery section or equipment (e.g., a separate ammonia stripping tower, ammonia absorption tower, ammonium bicarbonate synthesis tower, etc.) is required. The ammonium bicarbonate system can be directly processed in the same reaction vessel to form a solution, slurry, or crystalline product of ammonium bicarbonate, which can then be used in production in other fields.
[0012] This invention overcomes the problems of extremely low reactivity (slow denitrification rate) at room temperature and pressure, high nitrogen recovery rate, and large interfacial mass transfer resistance in the solid (mineral)-liquid (water / nitrate)-gas (carbon dioxide / ammonia) multiphase system by conducting in-depth research on the lattice dissociation kinetics of olivine, the in-situ release of iron / magnesium active components, and the coupling mechanism of nitrate reduction. These problems arise during the preparation of ammonium bicarbonate in solutions, slurries, or crystal products. By introducing specific pre-activation methods to break the passive state of the olivine lattice and utilizing the in-situ acidification of carbon dioxide to accelerate the dissolution of active Fe(II) and Mg(II), a synchronized resonance of "mineral dissociation-nitrate reduction-carbon-nitrogen coupling" is successfully achieved.
[0013] Furthermore, the pre-activation treatment is at least one of ball milling activation, heat treatment activation, and acid treatment activation.
[0014] Furthermore, the specific method of heat treatment activation is as follows: the olivine particles that have been preliminarily crushed are placed in a roasting furnace protected by an inert atmosphere (such as nitrogen or argon), heated to 400℃-800℃ at a heating rate of 5-15℃ / min, held at a constant temperature for 1-4 hours, and then cooled to room temperature in the furnace under an inert atmosphere.
[0015] The above-mentioned heat treatment activation process can induce lattice distortion and generate a large number of microcracks in olivine crystals through thermal stress, thereby increasing the exposure of internal reactive sites; at the same time, the use of an inert atmosphere can effectively prevent the highly reactive reducing component Fe(II) in olivine from being prematurely oxidized at high temperatures.
[0016] Furthermore, the specific method of acid treatment activation is as follows: the pre-crushed olivine particles are added to a weak acid or dilute acid solution with a concentration of 0.1 mol / L-1.5 mol / L (for example, one or more of dilute nitric acid, acetic acid, citric acid, and oxalic acid), and continuously stirred and soaked for 0.5-3 hours at a temperature of 25℃-60℃; after the reaction is completed, solid-liquid separation is performed, and the solid is washed with deionized water until neutral, and dried at 60℃-100℃ for later use.
[0017] The acid treatment activation process described above can preferentially etch some of the basic cations on the surface of olivine, forming a porous and rough surface layer rich in silanol groups, which significantly increases the specific surface area and porosity of the mineral, thereby greatly reducing the interfacial mass transfer barrier in the subsequent ammonium bicarbonate synthesis main reaction.
[0018] Furthermore, in aqueous solutions containing nitrates, NO3 - The concentration ranges from 0.1 mg / L to 10 mg / L.
[0019] Furthermore, the mass-to-volume ratio of the pre-activated olivine and the nitrate-containing aqueous solution is 200-400 g / L.
[0020] Furthermore, carbon dioxide or carbon dioxide-containing gas is introduced using any one or more of the following methods: continuous bubbling introduction, intermittent bubbling introduction, pressurized introduction, or pre-dissolving in water.
[0021] Furthermore, the reaction temperature is 20-250℃, the reaction pressure is 0.1-8.5 MPa, and the reaction time is 0.1-72 h.
[0022] Furthermore, the initial pH value at which the reaction system begins to react is 5.0-9.5.
[0023] Furthermore, the activator is Cu. 2+ Water-soluble salts, Ni 2+ Water-soluble salts, Fe 2+ Water-soluble salts, Fe 3+ Water-soluble salts, Mn 2+ It can be any one or more of the following: water-soluble salts, magnetite, ferrous hydroxide, and conductive carbon materials.
[0024] Furthermore, the amount of the activator added is 0.01%-1% of the mass of olivine.
[0025] Further, after the reaction is complete, the ammonium bicarbonate system is cooled to 0-35°C to form a solution, slurry, or crystalline product of ammonium bicarbonate.
[0026] Furthermore, the solution, slurry, or crystalline product of the ammonium bicarbonate also contains mineralization byproducts, which are any one or more of magnesium carbonate, basic magnesium carbonate, ferrous carbonate, and silica gel.
[0027] Furthermore, the olivine is natural olivine (such as iron-rich olivine, magnesium olivine, iron-magnesium olivine, and other types of olivine).
[0028] Furthermore, the average particle size of the pulverized olivine is 0.1-500 μm. Even further, it is 1-100 μm.
[0029] Compared with the prior art, the advantages of the present invention are:
[0030] 1. Carbon dioxide is moved from the traditional downstream carbonization raw material to the upstream component of the entire process, thereby achieving the coupling of olivine activation, nitrate reduction, and in-situ fertilizer generation.
[0031] 2. No separate ammonia recovery tower, absorption tower, and separate ammonium bicarbonate synthesis tower are required, resulting in a shorter process.
[0032] 3. The product is directly ammonium bicarbonate fertilizer or its slurry system, which is convenient for agricultural use.
[0033] 4. The magnesium and iron components in olivine can simultaneously form mineralization byproducts, improving the efficiency of carbon resource utilization.
[0034] 5. Applicable to synergistic scenarios of nitrate wastewater treatment and low-carbon fertilizer preparation. Attached Figure Description
[0035] Figure 1 The diagram below illustrates the process flow of the method for promoting the reduction of nitrates by olivine to produce ammonium bicarbonate using carbon dioxide, according to the present invention.
[0036] Figure 2 The diagram shows the effect of olivine reducing nitrate to ammonia with and without the introduction of carbon dioxide.
[0037] Figure 3 The image shows the effect of reducing 10 mg / L nitrate to ammonia with olivine powder of different concentrations (100, 200 and 400 g / L).
[0038] Figure 4 For: Initial NO3 - The effect of -N concentration (i.e., the concentration of nitrate nitrogen, 4, 10, 25, 50 mg / L) on ammonia production is shown in the figure.
[0039] Figure 5 The product slurry of ammonium bicarbonate compound fertilizer prepared by the method of the present invention.
[0040] Figure 6 The purpose was to test the effect of adding different types of activating agents to enhance the reduction of nitrate ions by olivine. Detailed Implementation
[0041] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0042] In some embodiments of the present invention, a method for promoting the reduction of nitrates to ammonium bicarbonate using carbon dioxide is provided, such as... Figure 1 As shown, it includes the following steps:
[0043] (1) The olivine raw material is crushed to obtain olivine particles, and pre-activated by mechanical activation, thermal activation, acid activation, or a combination of multiple activation methods;
[0044] Olivine particles are added to an aqueous solution containing nitrates to form a reaction system;
[0045] (2) Carbon dioxide or a gas containing carbon dioxide is introduced into the reaction system from the beginning of the reaction to carry out the reaction, so that carbon dioxide promotes the release of the active components of olivine and promotes the reduction of nitrates, while coupling with ammonia or ammonium generated in the reaction process in situ to form an ammonium bicarbonate system.
[0046] (3) After the above main reaction is completed, without going through an independent ammonia recovery section, the ammonium bicarbonate system is processed in the same reactor by cooling and / or depressurizing to form a solution, slurry or crystal product of ammonium bicarbonate.
[0047] Optionally, in the above preparation method, mechanical activation can be selected from ball milling activation.
[0048] Optionally, in the above preparation method, the heat treatment activation can be carried out by placing the pre-crushed olivine particles in a calcining furnace protected by an inert atmosphere (such as nitrogen or argon), heating them to 400℃-800℃ at a heating rate of 5-15℃ / min, holding them at a constant temperature for 1-4 hours, and then cooling them to room temperature in the furnace under an inert atmosphere.
[0049] Optionally, in the above preparation method, the acid treatment activation can be performed by adding the pre-crushed olivine particles to a weak acid or dilute acid solution with a concentration of 0.1 mol / L-1.5 mol / L (e.g., one or more of dilute nitric acid, acetic acid, citric acid, and oxalic acid), and continuously stirring and leaching at a temperature of 25℃-60℃ for 0.5-3 hours; after the reaction is completed, solid-liquid separation is performed, and the solid is washed with deionized water until neutral, and dried at 60℃-100℃ for later use.
[0050] Optionally, in aqueous solutions containing nitrates, NO3 - The concentration ranges from 0.1 mg / L to 10 mg / L.
[0051] Optionally, carbon dioxide or carbon dioxide-containing gas can be introduced by one or more of the following methods: continuous bubbling, intermittent bubbling, pressurized introduction, or pre-dissolving in water.
[0052] Optionally, the reaction temperature is 20-250℃, the ambient pressure is 0.1-8.5 MPa, and the reaction time is 0.1-72h.
[0053] Optionally, an activator may be added during the reaction. The activator is Cu. 2+ Ni 2+ Fe 2+ Fe 3+ Any one or more of magnetite, ferrous hydroxide, and conductive carbon materials.
[0054] Specifically, the activator can be one or more of the following: water-soluble copper salts (e.g., copper sulfate, copper nitrate, or copper chloride), water-soluble nickel salts (e.g., nickel sulfate, nickel nitrate, or nickel chloride), water-soluble ferrous salts (e.g., ferrous sulfate or ferrous chloride), water-soluble iron salts (e.g., ferric sulfate, ferric nitrate, or ferric chloride), water-soluble manganese salts (e.g., manganese chloride, manganese sulfate), magnetite, ferrous hydroxide, and conductive carbon materials.
[0055] The amount of activator added can be further selected as 0.01%-1% of the mass of olivine.
[0056] Optionally, the ammonium bicarbonate system is cooled (naturally cooled in air) to 0-35°C to form a solution, slurry, or crystalline product of ammonium bicarbonate.
[0057] The final ammonium bicarbonate solution, slurry, or crystalline product generally also contains one or more of the following: residual olivine particles, magnesium salts, iron salts, and siliceous byproducts.
[0058] Example 1
[0059] The method used in this embodiment, which utilizes carbon dioxide to promote the reduction of nitrates by olivine to produce ammonium bicarbonate, has the following specific steps.
[0060] (1) The natural olivine ore was crushed and ball-milled to obtain olivine powder with an average particle size of 20 μm;
[0061] Weigh 400 g of olivine powder and add it to 2 L of an aqueous solution containing sodium nitrate (10 mg / L) to form a reaction system. The mass-to-volume ratio of olivine powder to the aqueous solution containing sodium nitrate is 200 g / L.
[0062] (2) Add the obtained reaction system slurry into a pressure-resistant reactor. Carbon dioxide is introduced from the beginning of the reaction to make the CO2 partial pressure in the reactor 0.8 MPa. Stir the reaction at 80-90℃ for 10 h to promote the conversion of nitrate to ammonia / ammonium by the active components in olivine, and at the same time form an ammonium bicarbonate system in the same system.
[0063] (3) After the reaction is complete, heating is stopped, and the temperature is lowered to below 25°C within the same reactor to obtain ammonium bicarbonate fertilizer slurry. Alternatively, the temperature can be further lowered to 0-10°C to allow some ammonium bicarbonate to crystallize, yielding ammonium bicarbonate crystalline products, such as... Figure 5 As shown.
[0064] Sampling and testing showed that the conversion efficiency of the nitrate to ammonia / ammonium in this batch reached 88.5%, and the total recovery rate of ammonium bicarbonate reached 85.2%.
[0065] Example 2: One-step method for atmospheric pressure bubbling
[0066] This embodiment uses a one-step atmospheric pressure bubbling method to generate ammonium bicarbonate, and the specific steps are as follows.
[0067] (1) The natural olivine ore was crushed and ball-milled to obtain olivine powder with an average particle size of 20 μm. Then, it was activated by acid treatment with a weak acid (0.5 mol / L acetic acid solution) (continuous stirring and leaching for 1 hour at a temperature of 40℃). Subsequently, the solid and liquid were separated and the solid was washed with water and dried for later use.
[0068] Weigh 100 g of pre-activated olivine powder and add it to 2 L of sodium nitrate-containing wastewater (this wastewater comes from a metal surface treatment plant and has undergone acid-base neutralization and heavy metal precipitation treatment, with an initial nitrate concentration of 0.2 mg / L) to form a reaction system.
[0069] (2) Add the obtained reaction system slurry into a pressure-resistant reactor, and continuously bubble carbon dioxide from the start of the reaction (the bubbling flow rate of carbon dioxide gas is 200 mL / min, and the reactor is kept at a normal pressure of 0.1 MPa). Stir the reaction at 75°C for 24 h, so that the active components in the olivine promote the conversion of nitrate to ammonia / ammonium, and at the same time form an ammonium bicarbonate system in the same system.
[0070] (3) After the reaction is complete, stop heating and cool down to below 20°C in the same reactor to directly obtain ammonium bicarbonate fertilizer slurry.
[0071] Sampling and analysis showed that under normal pressure bubbling conditions, the reaction efficiency of nitrate in wastewater to ammonia / ammonia was 82.3%, and the total yield of ammonium bicarbonate fertilizer products was 78.6%.
[0072] Example 3: One-step method containing activator
[0073] This embodiment uses a method that utilizes carbon dioxide to promote the reduction of nitrates by olivine to produce ammonium bicarbonate, and an activator is also added during the reaction. The specific steps are as follows.
[0074] (1) The natural olivine ore was crushed and ball-milled to obtain olivine powder with an average particle size of 20 μm;
[0075] Weigh 100 g of olivine powder and add it to 2 L of an aqueous solution containing sodium nitrate, wherein the concentration of sodium nitrate is 0.2 mg / L, to form a reaction system.
[0076] (2) Add the obtained reaction system slurry into a pressure-resistant reactor, and add copper sulfate or nickel sulfate as an activator. The amount added is 0.5 g of the olivine mass, that is, 0.5% of the olivine powder mass;
[0077] Carbon dioxide is introduced from the start of the reaction to make the CO2 partial pressure in the reactor 0.8 MPa. The reaction is stirred at 80-90℃ for 10 h to allow the active components in the olivine to promote the conversion of nitrate to ammonia / ammonium, while simultaneously forming an ammonium bicarbonate system in the same system.
[0078] (3) After the reaction is complete, stop heating and cool the system to below 25°C in the same reactor to obtain ammonium bicarbonate fertilizer slurry. Alternatively, the temperature can be further lowered to 0-10°C to allow some ammonium bicarbonate to crystallize and obtain ammonium bicarbonate crystal product.
[0079] Sampling and analysis showed that after adding the activator, the reaction efficiency of nitrate ions to ammonia / ammonia in the aqueous solution containing sodium nitrate was 93.2%, and the total yield of ammonium bicarbonate fertilizer products was 91.4%.
[0080] Example 4: Solution, slurry, or crystalline product of ammonium bicarbonate containing mineralization byproducts
[0081] The ammonium bicarbonate fertilizer slurry prepared in Example 1 was not subjected to complete solid-liquid separation. Instead, unreacted large olivine particles were removed by hydrocyclone or natural sedimentation. The mineralization byproducts such as magnesium carbonate, basic magnesium carbonate, ferrous carbonate, and silica gel generated in situ in the slurry were retained, and finally, an ammonium bicarbonate slurry containing mineralization byproducts was obtained.
[0082] The initial focus of the technical research for this invention was on purifying ammonium bicarbonate, but actual agricultural tests revealed that the purification process was extremely energy-intensive. Further research unexpectedly discovered that mineralization byproducts (especially silica gel and ferrous carbonate) retained without deep solid-liquid separation could form microscopic encapsulation structures with ammonium bicarbonate. Tests showed that when this composite slurry was directly applied to acidic soils, the volatilization loss rate of ammonium bicarbonate was reduced by 40%, and the overall effective utilization rate was increased by approximately 12% compared to pure aqueous solutions. Simultaneously, the associated magnesium and iron components played a good role in soil conditioning and micronutrient supplementation, transforming "impurities" into "slow-release synergists" and significantly shortening the process flow.
[0083] Experimental Example 1: The conversion efficiency of ammonium bicarbonate was tested when CO2 was not introduced at the beginning of the reaction.
[0084] The steps and parameters in this comparative example are exactly the same as in Example 1, except that nitrogen gas at the same pressure (0.8 MPa) is introduced instead of carbon dioxide.
[0085] like Figure 2 As shown, when CO2 was not introduced, the content of ammonium nitrogen did not change significantly over time; after CO2 was introduced, the content of ammonium nitrogen increased rapidly with the introduction time. After the reaction was completed, the reaction efficiency of nitrate to ammonia / ammonia in the system without CO2 was only 31.4% (while it was 88.5% in Example 1), and the yield of ammonium bicarbonate collected after cooling was almost 0 (the small amount of ammonia generated had already evaporated when the reactor was opened).
[0086] On the surface, reducing nitrate with olivine appears to be a simple redox reaction. However, in practice, the technical research encountered an extremely challenging problem: "mineral surface passivation." In the absence of CO2, once the Fe(II) on the surface of olivine reduces nitrate, it rapidly oxidizes into a dense layer of ferric hydroxide / ferric oxide "rust," which tightly encapsulates the mineral particles. This prevents the release of the abundant active substances inside, causing the reaction to stall in a very short time (with a denitrification rate of only 31.4%).
[0087] This invention introduces CO2 from the outset, not only for the subsequent synthesis of ammonium bicarbonate, but also to utilize the slightly acidic carbonate buffer solution formed by CO2 in the system to dynamically and in real time strip away the passivation layer on the surface of olivine, forcing Fe(II) and Mg(II) to continuously dissolve, thereby maintaining extremely high denitrification efficiency. The in-situ generated carbonic acid can immediately "capture" highly volatile ammonia and solidify it in situ into ammonium bicarbonate, solving the technical bottleneck of free ammonia escape in traditional processes.
[0088] Experimental Example 2: Study on the ammonia production effect of reducing sodium nitrate aqueous solution with different concentrations of olivine powder
[0089] This embodiment studies the ammonia production effect of reducing an aqueous solution containing sodium nitrate with a concentration of 10 mg / L with different amounts of olivine powder. The specific method is basically the same as in Example 1. The difference is that the amount of pre-activated olivine powder added is 200 g, 400 g, and 800 g, and the volume of the aqueous solution containing sodium nitrate is 2 L with a concentration of 10 mg / L; that is, the mass-to-volume ratio of the olivine powder to the aqueous solution containing sodium nitrate is 100 g / L, 200 g / L, and 400 g / L, respectively.
[0090] The results are as follows Figure 3 As shown, when the amount of olivine powder used is 100 g / L, the content of ammonium nitrogen does not change significantly over time. However, when the amount of olivine powder used reaches 200 g / L and 400 g / L, the content of ammonium nitrogen increases significantly over time.
[0091] Sampling and analysis showed that when the amount of olivine powder was 100 g / L, 200 g / L, and 400 g / L, the reaction efficiency of ammonia / ammonium in the aqueous solution containing sodium nitrate was 20%, 70%, and 90%, respectively. Figure 3 As shown.
[0092] Experimental Example 3: The effect of nitrate concentration in nitrate-containing aqueous solutions on the conversion efficiency of ammonium bicarbonate.
[0093] Except for adjusting the nitrate concentration in the aqueous solution containing sodium nitrate to 4 mg / L, 25 mg / L, and 50 mg / L (0.4, 2.5, and 5 times that of Example 1, respectively) in Example 1, the other steps and parameters are exactly the same as in Example 1.
[0094] like Figure 4 As shown, the concentration of nitrate in the sodium nitrate-containing aqueous solution increases significantly, as does the content of ammonium nitrogen. After the reaction, although the absolute amount of ammonia generated in the system increased slightly, the overall conversion efficiency of nitrate showed a precipitous drop, plummeting to 18.5%.
[0095] According to conventional understanding in the art, increasing the reactant concentration usually promotes the forward reaction. However, the inventors discovered a counterintuitive electron penetration barrier phenomenon in this heterogeneous reaction system: that is, when the nitrate concentration is too high, due to the transient oxidant (NO3) - The amount of reducing agent (Fe) exposed on the surface of olivine is far greater than that of olivine. 2+ The intense interfacial reaction causes an extremely thick, high-valence iron oxide crust to form instantly on the surface. Because the passivation rate is much greater than the rate of micro-acid stripping by CO2, the electron transport channels inside the mineral are completely cut off, resulting in a large amount of nitrate remaining in the wastewater.
[0096] The present invention limits the specific nitrate concentration (such as 10 mg / L in Example 1) precisely to achieve a delicate dynamic balance between the "oxidative passivation rate" and the "CO2 dissolution and stripping rate", which is also the key to this technology.
[0097] Experimental Example 4: Effect of the Amount of Activator Added on the Conversion Efficiency of Ammonium Bicarbonate
[0098] In this comparative example, 5% Cu by mass of olivine was added in step (2). 2+ Except for the use of copper sulfate as an activator (far exceeding 0.5% in Example 3), the other steps and parameters are the same as in Example 3.
[0099] Test data: After the reaction was completed, the reaction efficiency of nitrate to ammonia / ammonia was only 42.1% (far lower than the expected value in Example 3), and the product slurry was a dark blue-green precipitate. The test showed that the effective nitrogen content was extremely low.
[0100] In the conventional understanding of catalysis, appropriately increasing the catalyst usually improves efficiency. However, in this system, the inventors discovered that co-activators (such as Cu) 2+ There is an extremely narrow "golden window" for the addition of Cu. When the addition reaches 5%, under high-pressure CO2 and the slightly alkaline (ammonia) environment generated by the reaction, a large amount of Cu... 2+ It rapidly combines with carbonate ions in the system, causing a dense precipitation of basic copper carbonate (verdigris) to form on the olivine surface. This not only inefficiently consumes the carbon source used for fertilizer synthesis but also forms a physical blocking layer, leading to premature termination of the reaction. Simultaneously, excessive amounts of heavy metal copper are mixed into the product, rendering the slurry completely unsuitable for safe use as an agricultural fertilizer.
[0101] This invention has also been demonstrated through numerous experiments that by strictly controlling the addition of the activator in trace amounts of 0.01%-1%, it not only plays a catalytic role in establishing microscopic galvanic cells and accelerating electron transfer, but also perfectly avoids the pitfalls of precipitation blockage, demonstrating a high degree of ingenuity.
[0102] Experimental Example 5: Effect of different amounts of activator added on the conversion efficiency of ammonium bicarbonate
[0103] In this experimental example, following the method in Example 3, Cu with a concentration of 1 mM was used... 2+ (in the form of copper chloride), Ni 2+ (in the form of nickel chloride), Mn 2+ An ionic solution (in the form of manganese chloride) is added to the reaction system as an activator, and the amount of metal salt added is 0.01%-1% of the mass of olivine.
[0104] CO2 was introduced at the start of the reaction, and a control group, "olivine-CO2", was used without CO2 introduction.
[0105] The results are as follows Figure 6 The addition of 1 mM Cu 2+ Ni 2+ Mn 2+ After the solution was prepared, the yields of ammonium nitrogen in the system increased by 23%, 33%, and 53% compared to the control group, respectively. Trace amounts of Cu were observed. 2+ Ni 2+ Mn 2+ The addition of [a specific substance] significantly promotes the nitrate reduction reaction and increases the yield of ammonium nitrogen. The control group showed almost no denitrification effect in a system containing only olivine and metal ions. This indicates that only with the participation of CO2, after the active ferrous iron dissolves from the olivine, can the metal ions of the activator exert a catalytic promoting effect.
[0106] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
Claims
1. A method for promoting the reduction of nitrates to ammonium bicarbonate by olivine using carbon dioxide, characterized in that, Includes the following steps: The olivine was crushed and pre-activated in sequence, and then added to an aqueous solution containing nitrates to form a reaction system. Carbon dioxide or a gas containing carbon dioxide is introduced into the reaction system to carry out the reaction and form an ammonium bicarbonate system. After the main reaction is completed, the ammonium bicarbonate system is treated by cooling and / or depressurization to form a solution, slurry or crystalline product of ammonium bicarbonate.
2. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, The pre-activation treatment method is at least one of ball milling activation, heat treatment activation, and acid treatment activation.
3. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, In aqueous solutions containing nitrates, NO3 - The concentration ranges from 0.1 mg / L to 10 mg / L.
4. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, The mass-to-volume ratio of the pre-activated olivine and the nitrate-containing aqueous solution is 200-400 g / L.
5. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, Carbon dioxide or carbon dioxide-containing gas is introduced by one or more of the following methods: continuous bubbling, intermittent bubbling, pressurized introduction, or pre-dissolving in water.
6. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, The reaction temperature is 20-250℃, the reaction pressure is 0.1-8.5 MPa, and the reaction time is 0.1-72h.
7. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, The initial pH value for the reaction system to begin is 5.0-9.
5.
8. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, An activator is also added during the reaction; the activator is Cu. 2+ Water-soluble salts, Ni 2+ Water-soluble salts, Fe 2 + Water-soluble salts, Fe 3+ Water-soluble salts, Mn 2+ Any one or more of the following: water-soluble salts, magnetite, ferrous hydroxide, and conductive carbon materials; Furthermore, the amount of the activator added is 0.01%-1% of the mass of olivine.
9. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, After the reaction is complete, the ammonium bicarbonate system is cooled to 0-35°C to form a solution, slurry or crystalline product of ammonium bicarbonate. Furthermore, the solution, slurry, or crystalline product of the ammonium bicarbonate also contains mineralization byproducts, which are any one or more of magnesium carbonate, basic magnesium carbonate, ferrous carbonate, and silica gel.
10. The method for promoting the reduction of nitrate to ammonium bicarbonate by olivine using carbon dioxide according to claim 1, characterized in that, The olivine, after being crushed, has an average particle size of 0.1-500 μm.