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Aluminum sulfate can be classified into various types according to different classification standards
Release time：
2025-05-22
Aluminum sulfate can be classified into various types based on different classification standards. The following are common classification methods and corresponding type introductions:
I. Classification by water of crystallization content
1. Anhydrous aluminum sulfate
Chemical formula: Al₂(SO₄)₃
Characteristics: It appears as a white powder, contains no water of crystallization, is highly hygroscopic, and is easily soluble in water.
Applications: It is mainly used as a laboratory reagent, catalyst preparation, or in industrial processes sensitive to moisture (such as certain special catalyst carriers, dehydrating agents, etc.). However, due to its high production cost and strong hygroscopicity, large-scale industrial applications are less common.
2. Hydrated aluminum sulfate
Common form: Aluminum sulfate containing 18 molecules of water of crystallization is the most common, with the chemical formula Al₂(SO₄)₃・18H₂O. It appears as colorless transparent crystals or white powder, is easily soluble in water, and its aqueous solution is acidic.
Applications: This is the most commonly used type in industry, widely used in water treatment, papermaking, dyeing, fermentation, etc. (such as flocculants, sizing agents), with low cost and ease of use.
II. Classification by purity and application
1. Industrial grade aluminum sulfate
Purity: The content of aluminum oxide (Al₂O₃) is usually around 15%~17%, containing a small amount of iron, calcium, magnesium and other impurities. It usually appears as grayish-white or slightly yellow powder/crystals.
Applications:
Water treatment: Used as a flocculant to remove suspended solids, organic matter, and heavy metals from water (such as industrial wastewater, domestic sewage, drinking water pretreatment).
Papermaking industry: Used as a sizing agent for paper to improve the water resistance and strength of paper.
Other industries: Dyeing and fixing, cement strengthening, fire-fighting foam extinguishing agents, mining and beneficiation, etc.
2. Food grade aluminum sulfate
Purity: Higher purity, with strictly controlled content of impurities (such as heavy metals, arsenic, etc.), meeting food safety standards. It appears as white crystals or powder.
Applications:
Food additive: Mainly used as a leavening agent (such as in fried bread sticks and cakes, reacting with baking soda to produce carbon dioxide gas to make food fluffy), or as a pickling agent and anti-discoloration agent (such as inhibiting enzyme activity in pickled vegetables).
Note: Since excessive intake of aluminum may be harmful to health, the use of food-grade aluminum sulfate must strictly follow national limit standards (such as China's GB 2760, which stipulates the maximum usage in various foods).
3. Pharmaceutical grade aluminum sulfate
Purity: Extremely high purity, extremely low impurity content, must meet pharmaceutical industry standards. It appears as a fine white powder.
Applications:
External medicine: Such as astringents (used in antiperspirants, oral ulcer patches, to astringent mucous membranes or inhibit sweat secretion), epistaxis agents (to stop bleeding by constricting blood vessels).
Pharmaceutical intermediates: Used as catalysts or reaction raw materials in the synthesis of certain drugs.
4. Reagent grade aluminum sulfate
Purity: Analytical reagent (AR grade) or chemically pure (CP grade), aluminum oxide content ≥15.6%, extremely low impurity content. It appears as white crystals or powder.
Applications: Mainly used in laboratory analysis, scientific research experiments (such as chemical reagents, standard solution preparation), university teaching demonstrations, etc.
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