Polyaluminium Chloride (PAC) is an inorganic polymer coagulant. It is a yellow solid powder that is widely used in water treatments. PAC is better than other aluminum salts such as aluminium chloride, aluminium sulphate, and other various forms of Polyaluminium chlorisulfate and Polyaluminium chloride that they have lower charge than PAC.
These are 2 methods for polyalumunium chloride, the Gypsum process and Pressure process. The pressure process is widely used in Europe and Latin America. These are following steps:
1) Mixing the press cake with Hydrochloric acid
This process needs press cake as a raw material that containd aluminium metal, alumina chloride, alumina tryhidrate, and aluminium sulphate. The press cake mixes with concentrated hydrochloric acid that they are blended in agitated tank. The press cake contains about 9% (w/w) aluminium and 12% (w/w) sulphate. The cake is solute in hydrochloric acid solution. The temperature of this reactor reach about 150oC and the pressure is high.
2) Mixing the product with aluminium hydroxide
The first process is releasing hydrogen as side product. It is an explosive and hazardous substance. Industry usually adds the aluminium hydroxide in the second process. The combination of aluminium hydroxide and hydrochloric acid produces aluminium chlorohydrate (ACH). This reaction determines the value of m and n in the Polyalumunium chloride molecules. This reaction happens at 500 kPa and 170oC.
3) Precipitating the solution
Pressure and temperature of Polyalumunium chloride sink into standard level. Stable PAC need at least 9 weeks at 30o to precipitate. The presence of water during the process will be evaporated in reactor that produces steam. Finally, Polyalumunium chloride contains more than 50% Al2O3.
Artificial Coal Industry
Polyalumunium chloride is used for separating coal and water with excellent effect.
Polyalumunium chloride is used for oil and water separation.
Polyalumunium chloride is widely a raw material for deodorant manufacturing.
Polyaluminium chloride is used in the treatment of drinking potable water and wastewater treatment. PAC is well known to be used as flocculants for waste water treatment. It can remove impurities such as heavy metal, organic matter and colloidal particles. PAC has more advantages than other coagulant chemical. For example, PAC reacts faster due to its high charge, they form bigger flocs so it is easy to filtrate, PAC is efficient to be used over a wide pH range, decreased cleaning frequency of the filters, reducing health problem, and it uses lower dosage than the other chemical coagulant.
Polyaluminium chloride is widely used for setting dyes as a mordant, tanning the leather, fire retardant in textiles, coagulation agent for rubber latex and in pulp and paper manufacture.