Aluminium sulfate (Al2(SO4)3), commonly called alum, is produced as white crystals which are non-combustible and soluble in water. This dry hydrate (Al2(SO4)3.14H2O) is 17% Al2O3 and is also sold as a 47% w/w aluminium sulfate solution which is 8% Al2O3. It is also sold in solid form as kibbled, ground or dust.
Aluminium sulfate, Al2(SO4)3, is widely used by industry . Its most common applications are in the pulp and paper industry and in the purification of water.Aluminium sulfate has been used by man since 2000 BC, when the Egyptians used a mineral alum as a mordant in dyeing. It has long been used in paper sizing to improve durability and ink receptivity and in water treatment to clarify water. Other uses for alum include wastewater treatment, as a waterproofing agent and accelerator in concrete, as a clarifier for fats and oils and as a foaming agent in fire foams.
Alum (as aluminium sulfate is commonly called) is manufactured in a simple two-step process from aluminium trihydrate and sulfuric acid according to the following reaction:
2Al(OH)3 + 3H2SO4 + 8H2O → Al2(SO4)3 .14H2O ∆fH = -156 kJ mol-1
The first step involves mixing the ingredients in a reactor, and the second is the process of crushing the material to make the various grades of solid alum that are sold.
Aluminium trihydrate is purified from bauxite. Commercial bauxite (30-75% Al2O3) deposits occur in Australia, Jamaica, France, Guyana, Guinea, the USA and Brazil. Bauxite ore is dissolved in strong caustic soda to form sodium aluminate. The aluminium trihydrate is then precipitated by neutralisation (usually with carbon dioxide) or by autoprecipitation (the Bayer process). The other raw material, sulfuric acid, is manufactured for superphosphate production at Farmers Fertiliser Ltd. Acid arrives by road tanker and is pumped into storage tanks.
Post time: Feb-18-2022