Poly aluminum chloride, abbreviated as PAC, is an inorganic polymer coagulant with the chemical formula [Aln(OH)mCl3n-m]x, typically exhibiting hues from light yellow to deep brown and a resin-like texture. It is synthesized through the interaction between aluminum compounds such as aluminum hydroxide and hydrochloric acid or other aluminum salts.
PAC boasts high molecular mass and powerful bridging adsorption capabilities that cause it to hydrolyze when introduced to water, generating aluminum hydroxide flocs. These flocs serve as a key agent for coagulation processes, attaching to impurities including suspended particles, colloids, and organics, thereby facilitating their sedimentation and removal in both potable water treatment and industrial wastewater management.
The substance's density commonly exceeds 1.19 g/cm³, its pH usually falls within the range of 3.5 to 5, and its basicity (alkaline content) can be as high as 85% or more. PAC readily dissolves in water and can also be dissolved by inorganic acids, displaying hygroscopic properties and potential crystalline transformations at elevated temperatures.
Notably, due to its adaptability across varying water conditions and temperatures, PAC proves highly effective and versatile compared to many organic flocculants, particularly in treating low-temperature, low-turbidity, and organically contaminated raw waters. Its usage often results in reduced dosing requirements, lowered treatment expenses, and compatibility with automated dosing systems. With a broad operational pH spectrum (5−9), PAC can effectively treat a wide array of water types without significantly altering the treated water’s inherent pH balance and alkalinity levels.
