Preparation and characterisation of ferrite grade zinc oxide from zinc ash

T. Subbaiah, S.C. Mallick, I.N. Bhattacharya, S. Anand* and R.P. Das


Hydro & Electro metallurgy Departments, Regional Research Laboratory,
Bhubaneswar 751 013, Orissa, India


Received 3 February 2003; accepted 22 July 2004



ABSTRACT

Ferrite grade zinc oxide was prepared through aqueous processing of zinc ash followed by calcination. Zinc was quantitatively dissolved in sulphuric acid medium. The ferrous iron present in the leach solution was oxidised with hydrogen peroxide followed by precipitation of total iron by pH adjustment to 4.5 with dilute sodium hydroxide solution. Copper was removed by cementation using zinc dust. Zinc hydroxide was precipitated from the purified zinc sulphate solution with precipitating agents such as ammonia, ammonium carbonate, sodium carbonate and urea. A typical hydroxide obtained with ammonia as the precipitating agent was characterized by IR, XRD and TG-DTA. It was found that during precipitation pure zinc hydroxide was not obtained but ammonium zinc sulphate [(NH₄)₂Zn(SO₄)₂] and hydrated hydroxy zinc sulphate [ZnSO₄. 3Zn(OH)₂.4H₂O] had precipitated. Calcination temperature of ~940^oC was required to prepare zinc oxide from the precipitate. In order to obtain the desired particle size and surface area, pulverisation was done. A complete flow-sheet has been developed.


Keywords: Zinc ash, Zinc oxide, Precipitation, Calcination



* Corresponding author
   E-mail : sanand@rrlbhu.res.in