Polyaluminium Chloride (PAC)

About This Product

Polyaluminium chloride, PAC (CAS 1327-41-9), is an inorganic polymer coagulant used in water and wastewater treatment. It is a partly neutralised aluminium chloride in which hydroxide groups bridge aluminium atoms into pre-formed polynuclear species, often described by the general formula [Al2(OH)nCl6−n]m. The degree of neutralisation is expressed as basicity, and together with the aluminium content, expressed as Al2O3, it defines the grade. PAC is supplied as a liquid, typically around 10–18% Al2O3, or as a powder of about 28–30% Al2O3 that dissolves to a solution on site. Spray-dried powders are white to light yellow with very low insoluble matter and are used for drinking water and demanding industrial uses. Drum-dried or roller-dried powders are yellow to brown, with more iron and insolubles, and suit wastewater, sludge conditioning and industrial effluent. Higher basicity grades, around 70–85%, consume less alkalinity and work well in cold or soft water. PAC outperforms traditional aluminium sulfate in many plants for three reasons. Its pre-formed polymeric species act quickly and over a wider pH range, typically about 5 to 9. It consumes less of the water's alkalinity, so less caustic soda or lime is needed to correct pH afterwards. And it usually produces less, denser sludge. It is used in drinking-water clarification, municipal and industrial wastewater treatment, paper-mill retention and white-water treatment, textile and dyehouse effluent, oily and food-processing wastewater, and swimming-pool clarification. Flocculants such as cationic polyacrylamide are often dosed after it to build larger flocs. The parameters buyers agree are Al2O3 content, basicity, water-insoluble matter, pH of a 1% solution, iron and heavy metals such as arsenic, lead, cadmium, mercury and chromium. For drinking-water treatment in the UK, products generally need approval under Regulation 31 of the water quality regulations and conformity with BS EN 883, so ask whether the offered grade holds that approval before specifying it for potable use. Always confirm the dose by jar testing on your own water. PAC solutions are acidic and corrosive to metals, and PAC powders can cause serious eye damage; liquid grades are commonly transported as Class 8 corrosive liquids, while powder classification varies by grade. Take the hazard and transport classification from sections 2 and 14 of the safety data sheet. Under EU REACH and UK REACH, an importer should confirm which registration covers the import and use. Store liquid PAC in HDPE, GRP or rubber-lined tanks, because it corrodes mild steel. Keep powder bags sealed and dry, as it is hygroscopic and cakes, and use dust control and respiratory protection when making up solutions. When you enquire, state liquid or powder, the Al2O3 and basicity you need, the application (drinking water, wastewater or paper), any approval required, the pack format, your volumes and the destination.