Acid dissolution of alumina from waste aluminium dross

Abstract

Aluminium and its chemicals are generally produced from its oxidic ores, mainly bauxite through NaOH leaching by Bayer's process. There are other oxidic raw materials such as coal ash, clay etc. which are being explored with little success. Aluminium dross formed while melting of aluminium in presence of air is recycled back to the smelter to recover the residual aluminium after salt treatment. The remaining residue dross is usually considered as a waste. This contains a complex mixture of mostly aluminium oxide (50–75%), remaining metallic aluminium, nitride, carbide and sulphide of aluminium, some alloying elements and salts. On one hand, this residue is considered as hazardous waste, on the other hand as a rich source of alumina. In the present study the waste dross rich in alumina value was taken for acid dissolution studies to recover alumina value. The material responded favourably towards the acid dissolution. The washed material under stoichiometric condition of acid leached out ∼ 85% of alumina while under stringent condition more than 90% could be leached out. The results obtained therefore, shows that aluminium dross could be utilized to prepare alumina chemicals and thereby avoiding stockpiling.