Polyaluminum Chloride (PAC) 1327-41-9

Polyaluminum Chloride (PAC) is an inorganic polymeric coagulant, an intermediate hydrolysis product between aluminium trichloride and aluminium hydroxide. It appears as a yellow powder or pale yellow liquid and is the most widely used coagulant after alum in drinking water and wastewater treatment due to its high efficiency and wide pH tolerance.

PAC is pre-hydrolyzed with polynuclear aluminium species already formed before dosing. Compared to alum, PAC works over a wider pH range, requires lower dosage for equivalent turbidity removal, produces denser flocs that settle faster, consumes less alkalinity, and performs better in cold water and low-turbidity conditions.

PAC is primarily used as a coagulant for drinking water purification and municipal wastewater treatment to remove turbidity, color, organic matter, and heavy metals. It is also widely used in industrial wastewater treatment (textile, paper making, food processing, mining, oil refining), as a sizing agent in paper production, for sludge dewatering, and in precision casting.

Basicity refers to the degree of hydroxylation of the aluminium in PAC, expressed as a percentage of OH⁻ to aluminium ions. Higher basicity PACs (70-90%) are more pre-hydrolyzed, more stable, and need less alkalinity from source water. Lower basicity PACs (40-60%) have higher charge density and may perform better on certain waters. XRD Chemical can recommend the optimal basicity based on jar testing with your specific water source.

PAC outperforms traditional coagulants in several ways. It achieves 20-50% lower dosage than alum for equivalent turbidity removal, produces larger and denser flocs with settling rates up to 3 times faster, works effectively over a wider pH range (5-9), maintains good performance in cold water where alum effectiveness drops, and requires less pH correction due to lower alkalinity consumption.