What is Poly Aluminium Chloride (PAC) and Its Role in Water Treatment?

Poly Aluminium Chloride (PAC) is a widely used chemical in the field of water treatment due to its ability to act as an effective coagulant. It is a pre-hydrolyzed aluminum-based coagulant with a general formula of [Al_n(OH)_mCl_3n−m], where the values of n and m vary depending on the formulation. PAC comes in several forms, including liquid, powder, and granules, and its efficiency in coagulating impurities is notably higher than traditional coagulants like alum (aluminum sulfate).

Chemical Characteristics and Forms of PAC 

1. Chemical Structure and Composition: PAC is a partially hydrolyzed aluminum chloride compound with varying amounts of hydroxyl ions. The hydrolyzed state means that some of the aluminum ions in the solution are already partially reacted with water, making the coagulant faster-acting when it comes into contact with contaminants.

2. Physical Forms: PAC is available in both solid and liquid forms. The liquid form tends to have concentrations between 10% to 18% aluminum oxide, while the powder form is generally more concentrated. The exact formulation used depends on the application, but PAC is typically available with a basicity of 40-85%, indicating how much of the coagulant has been pre-hydrolyzed.

PAC in Water Treatment

PAC plays a crucial role in both drinking water purification and industrial wastewater treatment. It offers several benefits over traditional coagulants like alum and ferric chloride, making it a preferred choice in many water treatment processes.

1. Mechanism of Action

PAC works by destabilizing and aggregating the suspended particles in water. When PAC is added to water, the hydroxyl ions in its structure interact with impurities, causing them to flocculate (or clump together) into larger aggregates. These larger particles can then be easily removed through sedimentation, filtration, or flotation.

The pre-hydrolyzed nature of PAC allows for rapid flocculation and efficient particle removal, making it more effective than alum, especially in cold water conditions or when dealing with low turbidity water. Its efficiency also reduces the amount of sludge produced, a key advantage in wastewater treatment systems.

2. Applications in Water Treatment

Drinking Water Purification:
PAC is widely used to treat surface water and groundwater to remove suspended solids, organic matter, and pathogens. The coagulant effectively removes impurities, ensuring that the treated water is safe for consumption. Additionally, PAC helps in the reduction of turbidity and the removal of natural organic matter (NOM), which can form harmful disinfection byproducts when exposed to chlorine.

Wastewater Treatment:
In industrial wastewater treatment, PAC is particularly effective for removing color, heavy metals, and organic pollutants from effluents. Industries such as textiles, pulp and paper, and food processing use PAC for its superior performance in reducing chemical oxygen demand (COD) and biological oxygen demand (BOD). It is also highly efficient in removing phosphates, which contribute to the eutrophication of water bodies.

3. PAC's Advantages over Traditional Coagulants

PAC offers several advantages compared to conventional coagulants like alum or ferric chloride:

Higher Coagulation Efficiency:
PAC operates over a broader pH range, typically between 5.0 to 9.0, allowing it to be effective in various water conditions. This makes PAC more versatile and efficient compared to alum, which tends to work best at more acidic pH levels.

Reduced Sludge Volume:
Because PAC forms more compact and denser flocs, the volume of sludge produced during coagulation is significantly lower. This results in reduced disposal costs and easier sludge handling.

Lower Dosages Required:
The pre-hydrolyzed nature of PAC means that smaller dosages are needed to achieve the same or better results compared to other coagulants. This lowers the overall operational costs of water treatment.

Environmental and Safety Considerations

While PAC is highly efficient and widely used, it is essential to handle the chemical with care. The coagulant's acidity and corrosiveness can pose safety risks if not managed properly, requiring the use of appropriate protective equipment during handling. Additionally, PAC's environmental impact in water bodies should be considered, particularly concerning aluminum residuals.

Future Trends in PAC Usage

As water treatment technologies advance, the use of PAC is expected to grow, particularly in regions facing water scarcity and where the demand for efficient water reuse systems is increasing. Its versatility in treating both potable water and industrial effluents makes it a sustainable choice for managing diverse water treatment challenges. Moreover, with growing concerns over environmental pollution, PAC's ability to handle high turbidity and complex organic loads will continue to be an asset in environmental protection.

In summary, Poly Aluminium Chloride is an advanced, efficient coagulant in the water treatment sector. Its superior performance, environmental benefits, and cost efficiency make it a valuable tool for both municipal and industrial water treatment applications. As the need for clean water increases, the role of PAC in ensuring safe, treated water will remain vital.

Company Introduction for TJCY :

TJCY Chemicals is a leading supplier of Poly Aluminium Chloride (PAC), offering high-quality, customized solutions for various water treatment applications. Committed to safety, sustainability, and innovation, TJCY continually invests in advanced technologies to provide efficient and eco-friendly water treatment products. For more detailed product information, visit the official TJCY website.