Polyaluminum

Polyaluminum refers to a family of polymeric aluminum compounds, most commonly polyaluminum chloride (PAC). These inorganic polymers consist of aluminum-oxo-hydroxo species with varying charge densities and are used primarily as coagulants and flocculants in water and wastewater treatment. PACs are produced by controlled hydrolysis or partial neutralization of aluminum salts, and their exact composition depends on preparation conditions, resulting in oligomeric and polymeric forms with chloride or sulfate counterions in some products.

In applications, PACs destabilize colloidal particles and natural organic matter, promoting floc formation that can be removed by sedimentation and filtration. Compared with traditional alum (aluminum sulfate), PACs often achieve higher removal efficiencies at lower dosages and can operate effectively over a wider pH range, reducing sludge volume in some cases. They are also used in decolorization of pulp and paper effluents, wine and juice clarification, and various industrial processes.

Characteristics of polyaluminum products vary in basicity and molecular weight, which influence performance. They are typically supplied as liquids or powders and are highly soluble in water. Handling requires caution due to alkali content and potential irritants; storage and dosing equipment should be corrosion-resistant.

Safety and regulation: Residual aluminum in treated water is monitored, with guidelines differing by country. As with other aluminum-based coagulants, proper dosing minimizes residuals while achieving coagulation.

See also: Alum, Coagulant, Water treatment.