polialuminium

Polialuminium, also spelled polyaluminium or polialuminum, is a family of inorganic polymeric aluminum compounds formed from aluminum-oxygen-hydrogen units. The term covers polialuminium chloride (PAC), polialuminium sulfate (PAS), and related salts, with PAC being the most widely used in industry.

These species are hydroxo-aluminum polymers. Aluminum centers are connected by hydroxide bridges, creating positively charged clusters that can neutralize negatively charged colloids in suspension. The precise size and charge vary with synthesis conditions and the accompanying counterions (chloride, sulfate, etc.).

Production typically involves controlled hydrolysis of aluminum salts. For PAC, aluminum chloride or aluminum salts are partially hydrolyzed in water under regulated pH and temperature to produce aluminum-oxide-hydroxide networks with chloride counterions.

Applications: In water treatment, polialuminium compounds function as coagulants, promoting aggregation and removal of turbidity, organic matter, and microbes. They are used in drinking-water and wastewater plants, and in papermaking as drainage and retention aids. They can offer performance advantages at lower sludge production and wider pH ranges than traditional alum.

Safety and regulation: Handling requires standard chemical hygiene practices. Residual aluminum in treated water is monitored to meet regulatory limits, and spent coagulant sludge is managed to prevent environmental release.