Aluminum Ammonium Sulfate: A Versatile Compound in Chemistry

As an inorganic complex salt, ammonium aluminum sulfate is not only widely used in water treatment, papermaking, food additives and other fields, but also contains rich chemical knowledge and practical application secrets.

Figure 1 Characteristics of Aluminum ammonium sulfate

Properties

Ammonium aluminum sulfate, chemical formula NH₄Al(SO₄)₂, is a white or light yellow crystalline powder, odorless or slightly ammonia smell. It is easily soluble in water, insoluble in alcohol, and the aqueous solution is acidic. The compound has good stability, but it will decompose to produce toxic sulfur dioxide and ammonia at high temperatures, and special attention should be paid when using and storing it. In addition, ammonium aluminum sulfate also has a certain degree of hygroscopicity and needs to be sealed to prevent deliquescence.

Diversity of preparation methods

There are many methods for preparing ammonium aluminum sulfate, among which the more common ones are double decomposition method and bauxite method. The double decomposition method is usually prepared by reacting ammonium sulfate with aluminum hydroxide or sodium aluminate, and then filtering, evaporating, crystallizing and other steps. This method is simple in process, the raw materials are easy to obtain, and it is suitable for large-scale production. The bauxite method uses bauxite as raw material and is produced through complex processes such as acid dissolution, impurity removal, and crystallization. Although the cost is high, the product purity is high and it is suitable for fields with strict quality requirements.

Application

Water purification

As a water purifier, ammonium aluminum sulfate mainly adsorbs suspended particles and impurities in water through hydrolysis to generate aluminum hydroxide colloid, thereby achieving the purpose of purifying water quality. The water purification effect is significant and the cost is low. It is widely used in water plants, industrial wastewater treatment and other fields.

Papermaking industry

In the papermaking industry, ammonium aluminum sulfate, as an important sizing agent and precipitant, can enhance the strength and water resistance of paper and improve the quality of paper. At the same time, it can also promote the uniform distribution of pigments and make the color of paper more vivid.

Food additives

Ammonium aluminum sulfate can also appear in our daily life as a food additive, especially in the production of puffed foods such as fried dough sticks and fried dough sticks, and is often used as a leavening agent. It can react with alkaline substances such as sodium bicarbonate to generate carbon dioxide gas, which makes the dough expand and soften. However, it is worth noting that long-term excessive intake of foods containing ammonium aluminum sulfate may have a certain impact on human health, so countries have strict regulations on its use in food.

Environmental and social impact

While ammonium aluminum sulfate brings convenience, its production and use also have a certain impact on the environment. If the wastewater and waste gas generated in the production process are directly discharged without treatment, they will pollute the water and the atmosphere. In addition, as a food additive, the safety of ammonium aluminum sulfate has always been the focus of social attention. Therefore, strengthening environmental protection supervision, promoting green production processes, and improving the public's awareness and ability to choose food additives are all urgent issues to be solved.

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