1.Introduction

Polyaluminium Chloride (PAC for short) is an efficient inorganic high-molecular flocculant, widely used in water treatment, sewage treatment, industrial purification and other fields. According to the differences in production process, aluminum content, degree of alkalization (B value) and form, PAC can be classified into various types. This article will systematically introduce the classification criteria of PAC and its application characteristics.

2.Classification by production process

2.1 Drum Drying Method PAC

Production process: Liquid PAC is dried at high temperature in a drum to form solid particles.

Features:

The product is in flake or granular form and dissolves relatively quickly.

It has a relatively high aluminum content (usually ≥28%) and is suitable for the treatment of water with high turbidity.

The production cost is relatively low and it has wide market applications.

2.2 Spray Drying Method PAC

Production process: Liquid PAC is sprayed under high pressure and instantly dried in hot air to form microspherical particles.

Features:

The product is in fine powder form and dissolves extremely quickly.

High aluminum content (≥30%) leads to better flocculation effect.

It is suitable for high-standard drinking water and fine chemical water treatment.

The production cost is relatively high and it is usually used in the high-end market.

2.3 Acid-soluble aluminum ash method PAC

Production process: It is prepared by reacting waste materials such as aluminum dross and aluminum slag with hydrochloric acid.

Features:

Low cost and suitable for resource utilization.

The product contains a lot of impurities and requires further purification.

It is mainly used for industrial wastewater treatment and less for drinking water.

3. Classified by aluminum content (Al₂O₃%)

Aluminum content is an important indicator for measuring the quality of PAC and directly affects the flocculation effect.

Low-aluminum PAC 10-20% is used for the treatment of general industrial wastewater and water with low turbidity

Chinalco PAC 21-28% municipal sewage and ordinary drinking water treatment

High-alumina PAC ≥28% high turbidity water, high-standard drinking water, fine chemical wastewater

4. Classified by degree of alkalization (B value)

The degree of alkalization affects the electro-neutralization capacity and flocculation performance of PAC:

Low alkalization degree (30%-50%), strong positive charge, outstanding electro-neutralization ability, but small flocs. Treatment of water with high turbidity and wastewater containing a large amount of colloids

Medium alkalization degree (50%-70%) ensures balanced flocculation effect, fast sedimentation speed and is the most widely used. Municipal sewage, general industrial wastewater and drinking water treatment

High alkalization degree (70%-85%) molecules have a high degree of polymerization and strong adsorption bridging capacity, but their solubility is slightly poor. Low-turbidity water and wastewater with a high content of organic matter (such as printing and dyeing wastewater)

5. Classification by physical form

5.1 Liquid PAC

Features:

It does not require dissolution, is convenient to use and suitable for continuous dosing systems.

The transportation and storage costs are relatively high, making it suitable for short-distance applications.

The aluminium content is usually 10%-12%.

5.2 Solid PAC

Subdivision type:

Powdered PAC: Dissolves quickly and is suitable for small-scale water treatment.

Granular PAC: It is convenient for transportation, has a moderate dissolution rate, and is the most widely used.

Flaky PAC: Dissolves relatively slowly, but has good storage stability.

6. Conclusion

There are various classification methods for PAC. Different types of products vary in composition, form, and flocculation mechanism, and are suitable for different water qualities and treatment requirements. In practical applications, the appropriate PAC type should be selected based on the characteristics of water quality (such as turbidity, pH, and pollutant types) to achieve the best treatment effect. In the future, with the increasing environmental protection requirements, new products such as high-performance composite PAC and nano PAC will have greater development potential.