Polyaluminum Chlorides

AbstractAluminum chloride hydroxide, AlCl(OH)2, AlCl2(OH), products, commonly known as polyaluminum chlorides (PAC), are used for a wide variety of industrial applications. Other names for PAC are basic aluminum chloride, polybasic aluminum chloride, aluminum hydroxychloride, aluminum oxychloride, and aluminum chlorohydrate. The presence of polymeric, aluminum‐containing cations, the distribution of which can differ greatly, typifies PAC products. Commercially, PAC has been used in water and wastewater treatment in Japan, the former USSR, and Europe since about 1970, and in the United States since the early 1980s. Aluminum chlorohydrate, Al2Cl(OH)5, a specialty PAC product, has been utilized as an antiperspirant for over 50 years. Physical and chemical properties of the numerous PAC products can vary considerably. PAC products are usually aqueous solutions, although solid products are also sold. Solutions range from colorless to amber and from clear to hazy in appearance. A generic manufacturing process for PAC involves the addition of base to aluminum chloride solution. A common process for the manufacture of aluminum chlorohydrate involves the addition of metallic Al to aluminum chloride. Liquid polyaluminum chloride is acidic and corrosive to common metals. Suitable materials for construction of storage and handling facilities include synthetic rubber‐lined steel, corrosion‐resistant fiber glass‐reinforced plastics (FRP), ceramics, tetrafluoroethylene polymer (PTFE), and others. Polyaluminum chloride products used in the treatment of potable (drinking) water must be approved by the National Sanitation Foundation (NSF). Aluminum chlorohydrate for topical use as an antiperspirant is regulated by the FDA.