1. Introduction to Ammonium Bicarbonate
Ammonium bicarbonate, with the chemical formula , is an inorganic compound also known by several names such as ammonium hydrogen carbonate, acid ammonium carbonate, and food stink powder. It presents as a white or colorless solid powder, characterized by a distinct odor of ammonia. This compound is highly soluble in water and glycerol but insoluble in organic solvents like benzene, ethanol, and acetone. It has a molecular weight of 79.06 and a density of 1.586 g/cm³.
One of the notable characteristics of ammonium bicarbonate is its instability when exposed to heat or water. It readily decomposes into ammonia ( ), carbon dioxide ( ), and water ( ) under such conditions. In an aqueous solution, it undergoes hydrolysis to form ammonia water and carbonic acid. Additionally, it can react with acids and salts, which is fundamental to understanding its diverse applications.
2. Physical and Chemical Properties
2.1 Physical Properties
Appearance: Ammonium bicarbonate is typically seen as a white, crystalline powder. This fine - grained texture makes it easy to handle in various industrial and domestic applications. For example, in the food industry, its white color is ideal as it does not impart any unwanted color to the products it is used in, such as baked goods.
Odor: It has a distinct, pungent odor of ammonia. This ammonia - like smell is a characteristic feature that can be easily detected even in small quantities. When stored in a confined space, the odor can become quite noticeable, which is an important factor to consider in storage and handling.
Solubility: It is highly soluble in water, with a solubility of about 220 g/L at 20 °C. This high solubility in water is crucial for its use in agricultural applications as a fertilizer, as it can quickly dissolve in soil moisture and be absorbed by plant roots. It is also soluble in glycerol but insoluble in organic solvents like benzene, ethanol, and acetone.
Density: The density of ammonium bicarbonate is 1.586 g/cm³. This relatively high density means that it is heavier than water, which can influence its handling and transportation in industrial settings. For instance, when it is transported in bulk, the density affects the volume - to - weight ratio, and appropriate containers and handling equipment need to be used.
Melting Point: It has a melting point of approximately 107.5 °C under rapid heating conditions. However, it starts to decompose well below this temperature, around 60 °C, into ammonia, carbon dioxide, and water. This decomposition behavior is more relevant than the melting point in most practical applications.
2.2 Chemical Properties
Thermal Decomposition: One of the most notable chemical properties of ammonium bicarbonate is its thermal instability. When heated, it decomposes according to the following chemical equation: . This decomposition is highly endothermic, meaning it absorbs heat. In the baking process, this property is exploited as the release of carbon dioxide gas causes dough to rise, creating a light and fluffy texture in bread, cakes, and pastries.
Hydrolysis in Aqueous Solution: In water, ammonium bicarbonate undergoes hydrolysis. The ammonium ion ( ) and the bicarbonate ion ( ) react with water molecules. The ammonium ion donates a proton to water, forming hydronium ions ( ) and ammonia ( ), while the bicarbonate ion can accept a proton from water to form carbonic acid ( ), which further decomposes into carbon dioxide and water. The overall hydrolysis reaction can be represented as: . This hydrolysis affects the pH of the solution, making it slightly alkaline due to the presence of ammonia.
Reaction with Acids: When ammonium bicarbonate reacts with acids, a typical acid - base reaction occurs. For example, with hydrochloric acid ( ), the reaction is as follows: . The bicarbonate ion in ammonium bicarbonate reacts with the hydrogen ions from the acid to form carbon dioxide gas, water, and an ammonium salt. This reaction is often used in chemical analysis and in some industrial processes where the generation of carbon dioxide is required.
Reaction with Bases: It also reacts with bases. When reacting with sodium hydroxide ( ), the ammonium ion in ammonium bicarbonate reacts with the hydroxide ion from the base. The chemical equation for a reaction with a sufficient amount of sodium hydroxide is: . Here, ammonia gas is released, and a carbonate salt is formed. This reaction is important in understanding the chemical behavior of ammonium bicarbonate in alkaline environments.
3. Production Method - Carbonization Process
The carbonization process is a commonly used method for the production of ammonium bicarbonate, especially in the context of ammonia - based chemical industries. This method is known for its relatively simple process and cost - effectiveness, making it a popular choice for large - scale production.
3.1 Principle
The fundamental principle of the carbonization process for ammonium bicarbonate production is based on the reaction between ammonia ( ), carbon dioxide ( ), and water ( ). The overall chemical reaction can be represented by the equation: . This reaction is an exothermic reaction, meaning it releases heat during the process. The reaction occurs in an aqueous medium, where ammonia is first dissolved in water to form an ammonium - rich solution. Then, carbon dioxide is introduced into this solution. The carbon dioxide reacts with the ammonia - water solution, leading to the formation of ammonium bicarbonate.
3.2 Process Flow
Ammonia Absorption: First, ammonia gas is absorbed in water. This is usually carried out in an absorption tower. The ammonia - water solution obtained has a certain concentration, which is carefully controlled as it affects the subsequent carbonization reaction. For example, a more concentrated ammonia - water solution can lead to a faster reaction rate, but it also requires more precise control to ensure the quality of the final product.
Carbon Dioxide Introduction: The next step is to introduce carbon dioxide into the ammonia - water solution. The carbon dioxide can be sourced from various industrial processes, such as the combustion of fossil fuels in power plants or the decomposition of limestone in lime - kilns. In a typical industrial setting, the carbon dioxide is purified to remove impurities like sulfur dioxide and particulate matter before being fed into the carbonization reactor.
Carbonization Reaction: The carbon dioxide reacts with the ammonia - water solution in a carbonization reactor. This reactor is designed to provide the optimal conditions for the reaction to occur efficiently. The reaction temperature and pressure are two crucial parameters. Generally, the reaction is carried out at a relatively low temperature, usually around 30 - 40 °C, to prevent excessive decomposition of the ammonium bicarbonate that may occur at higher temperatures. The pressure is also maintained at a moderate level, typically around 1 - 2 atmospheres, which helps in the solubility of carbon dioxide in the solution and promotes the reaction.
Crystallization and Separation: As the reaction progresses, ammonium bicarbonate crystallizes out of the solution. The crystallization process is carefully monitored to ensure the formation of high - quality crystals. After crystallization, the solid ammonium bicarbonate is separated from the liquid phase using methods such as filtration or centrifugation. For example, in a centrifugation process, the mixture is spun at high speeds, and the denser ammonium bicarbonate crystals are forced to the outer edge of the centrifuge, where they can be collected.
Drying: The separated ammonium bicarbonate crystals still contain some moisture. To obtain a dry product suitable for various applications, the crystals are dried. This can be done using hot air drying or other drying techniques. During the drying process, care must be taken not to over - heat the ammonium bicarbonate, as it can decompose if the temperature is too high.
One of the unique aspects of the carbonization process is its simplicity in terms of the raw materials and the reaction mechanism. It does not require highly complex chemical engineering processes compared to some other chemical production methods. Additionally, the raw materials, ammonia and carbon dioxide, are relatively abundant in the chemical industry, which makes the production cost - effective. This method is also highly adaptable, as it can be scaled up or down depending on the production requirements, making it suitable for both large - scale industrial production and smaller - scale operations in some regions.
4. Diverse Applications
4.1 In the Food Industry
In the food industry, ammonium bicarbonate plays crucial roles as an acidity regulator and leavening agent. As an acidity regulator, it helps maintain the proper pH level in food products, which is essential for flavor, texture, and preservation. For example, in some dairy products, it can adjust the acidity to prevent spoilage and enhance the taste.
As a leavening agent, ammonium bicarbonate is widely used in baking. When heated during the baking process, it decomposes into ammonia, carbon dioxide, and water. The carbon dioxide gas produced creates bubbles in the dough or batter, causing it to rise and giving the baked goods a light and fluffy texture. It is commonly used in the production of cookies, crackers, and some traditional Asian pastries. In the making of Chinese mooncakes, ammonium bicarbonate is added to the dough formula. The decomposition of ammonium bicarbonate during baking makes the mooncake crust crispy and the overall texture more palatable.
4.2 In Light Industry
In the leather manufacturing industry, ammonium bicarbonate is used in the tanning process. It helps in the removal of hair and fat from the raw hides, making the leather - making process more efficient. By reacting with the proteins in the hair and fat, it can break them down and facilitate their removal, resulting in a cleaner and more suitable raw material for further leather processing.
In the production of foam titanium, ammonium bicarbonate is employed as a foaming agent. When added to the titanium - containing precursor materials and then subjected to heat treatment, the decomposition of ammonium bicarbonate releases gases, which create pores in the titanium matrix, forming a porous foam - like structure. This porous structure of foam titanium has applications in various fields such as biomedical implants, where its lightweight and porous nature can promote tissue ingrowth, and in some filtration applications due to its high - porosity and corrosion - resistance properties.
4.3 In Agriculture
In agriculture, ammonium bicarbonate serves as a valuable nitrogen - containing fertilizer. Nitrogen is an essential nutrient for plant growth, as it is a key component of proteins, nucleic acids, and chlorophyll. When applied to the soil, ammonium bicarbonate provides plants with a readily available source of nitrogen. As it dissolves in soil moisture, the ammonium ions ( ) can be absorbed by plant roots. For example, in rice paddy fields, ammonium bicarbonate is often used as a fertilizer. The rice plants can efficiently take up the nitrogen from ammonium bicarbonate, which promotes their leaf growth, increases photosynthesis efficiency, and ultimately leads to higher grain yields.
It can also be used in some pesticide - related applications. In certain formulations, it may be added to enhance the effectiveness of pesticides. For instance, in some fungicide - ammonium bicarbonate mixtures, the ammonium bicarbonate can help adjust the pH of the spray solution, which may improve the adhesion and penetration of the fungicide on the plant surface, thus better protecting the plants from fungal diseases.
4.4 In Water Treatment
Ammonium bicarbonate can contribute to water treatment processes. In some cases, it can be used to adjust the pH of water. For example, in industrial water treatment, when the water is too acidic, adding ammonium bicarbonate can raise the pH value towards a more neutral range. This is important as many industrial processes require water with a specific pH range to ensure the proper functioning of equipment and to prevent corrosion.
In the field of desalination, ammonium bicarbonate can play a role in the pretreatment of seawater. It can react with some of the impurities in seawater, such as certain metal ions. For example, it can react with calcium and magnesium ions present in seawater to form insoluble precipitates. These precipitates can then be removed through filtration or sedimentation, reducing the concentration of scale - forming ions in the seawater and making the subsequent desalination process, such as reverse osmosis, more efficient and less prone to membrane fouling.
4.5 In Chemical Industry
As a chemical raw material, ammonium bicarbonate is used in the production of various chemicals. For example, it is a key ingredient in the production of some ammonium - based salts like ammonium carbonate. The reaction of ammonium bicarbonate with certain chemicals can lead to the formation of ammonium carbonate, which has applications in the pharmaceutical and chemical industries.
It can also function as a tail - gas absorbent. In some industrial processes that produce acidic tail - gases containing carbon dioxide, sulfur dioxide, etc., ammonium bicarbonate can be used to absorb these gases. For instance, in the flue - gas desulfurization process of some power plants, ammonium bicarbonate can react with sulfur dioxide in the flue - gas. The reaction forms ammonium sulfite or ammonium bisulfite, which can be further processed, and at the same time, it helps to reduce the emission of sulfur - containing pollutants into the atmosphere.
4.6 In Environmental Governance
Ammonium bicarbonate has shown potential in the remediation of heavy - metal - contaminated soil. Heavy metals such as lead, cadmium, and copper in soil can pose a serious threat to the environment and human health. Ammonium bicarbonate can be used in a process called chemical extraction. When added to the contaminated soil, the ammonium ions in ammonium bicarbonate can exchange with the heavy - metal ions adsorbed on soil particles. This exchange reaction helps to solubilize the heavy metals, making them easier to be removed from the soil through leaching or other separation methods. For example, in a laboratory - scale experiment on lead - contaminated soil, adding an appropriate amount of ammonium bicarbonate solution can significantly reduce the concentration of lead in the soil, demonstrating its effectiveness in soil remediation.
5. Safety Precautions
When handling ammonium bicarbonate, several safety precautions are necessary.
5.1 Inhalation Risk
Ammonium bicarbonate powder can be irritating to the respiratory system. When handling the powder, especially in large quantities or in a poorly - ventilated area, there is a risk of inhaling the fine particles. Inhalation may cause coughing, sneezing, and irritation of the nasal passages and throat. In high - concentration exposures, it can lead to more serious respiratory problems. For example, in a factory where ammonium bicarbonate is produced or used in large - scale industrial processes, workers may be at risk if proper ventilation systems are not in place. To prevent inhalation, it is essential to work in well - ventilated areas. When handling large amounts of ammonium bicarbonate, the use of respiratory protection such as N95 masks or other appropriate dust - filtering masks is recommended.
5.2 Skin and Eye Contact
Direct skin contact with ammonium bicarbonate can cause irritation. The powder may dry out the skin, leading to redness, itching, and in some cases, a burning sensation. If the skin is exposed to ammonium bicarbonate for an extended period or in high - concentration situations, it can cause more severe skin damage. For example, if a worker's hands are frequently in contact with the powder without proper protection, skin problems may develop over time. In case of skin contact, immediately remove contaminated clothing and wash the affected area with plenty of water for at least 15 minutes.
Contact with the eyes is even more dangerous. Ammonium bicarbonate can cause severe eye irritation, redness, pain, and in extreme cases, damage to the cornea. If ammonium bicarbonate gets into the eyes, it is crucial to immediately rinse the eyes with a large amount of clean water for at least 15 minutes, holding the eyelids open to ensure thorough rinsing. Seek medical attention promptly. Workers should always wear appropriate eye protection, such as safety goggles or chemical - resistant glasses, when handling ammonium bicarbonate.
5.3 Storage Conditions
Ammonium bicarbonate should be stored in a cool, dry, and well - ventilated area. Since it is thermally unstable, high temperatures can accelerate its decomposition. Storing it in a place where the temperature is above 36 °C (under normal atmospheric pressure with moisture present) can cause it to start decomposing into ammonia, carbon dioxide, and water. For example, storing it in a warehouse without proper temperature control during hot summer months can lead to product degradation. It should be kept away from direct sunlight, as sunlight can also contribute to an increase in temperature and potentially trigger decomposition.
The storage area should also be free from sources of ignition, although ammonium bicarbonate is not flammable itself. However, the decomposition products, especially ammonia, can be a hazard in the presence of an ignition source. Additionally, it should be stored separately from strong oxidants and acids. Contact with strong oxidants can lead to violent reactions, and with acids, it will react to produce carbon dioxide gas, which can cause pressure build - up in closed containers. For example, if ammonium bicarbonate is stored near concentrated sulfuric acid, a rapid and potentially dangerous reaction may occur.
6. ConclusionAmmonium bicarbonate, with its unique physical and chemical properties, is a compound of great significance in various industries. Its instability when exposed to heat and water, along with its solubility and reactivity with other substances, form the basis for its wide - range of applications.
In the food industry, it serves as a crucial leavening agent and acidity regulator, contributing to the texture and flavor of many baked goods. In light industry, it aids in leather manufacturing and the production of foam titanium. In agriculture, it is an important nitrogen - containing fertilizer, promoting plant growth and increasing crop yields. In water treatment, it helps adjust the pH and pre - treat seawater for desalination. In the chemical industry, it is a raw material for other chemicals and an effective tail - gas absorbent. Even in environmental governance, it shows potential in remediating heavy - metal - contaminated soil.
However, when handling ammonium bicarbonate, safety precautions must be strictly adhered to. Inhalation, skin, and eye contact risks exist, and proper storage conditions are essential to maintain its quality and prevent decomposition.
Overall, ammonium bicarbonate plays a vital role in multiple aspects of our lives, from the food we eat to the industrial processes that drive economic development and environmental protection. As industries continue to evolve, the applications and importance of ammonium bicarbonate are likely to expand further, making it a compound worthy of continuous study and exploration.
AMMONIUM BICARBONATE
Category: Food Additives
Formula: NH4HCO3
Standard: GB1888-2014
Type: 25kg net PP+PE bag
Phone: +86 18322469665
Email: alice@rmgchem.com
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