How is Zinc produced?
The raw material used for the production of zinc is zinc concentrate, which is the result of a flotation process after the ore has been mined and milled. The zinc ore contains 1-15% zinc whereas the concentrate typically contains approx. 55% zinc, 6.5% iron and 32% sulphur together with other elements at much lower levels. The process begins with the roasting of the concentrate. At a temperature of around 950°C, oxidisation of the zinc, iron and sulphur occurs. The sulphur is collected as SO2 and is used to make sulphuric acid (H2SO4) – a commercial by-product. The iron and zinc oxides that, after the roasting process, have been reduced to powder form, are leached with dilute sulphuric acid. The solution is neutralised and the precipitates i.e. metallic co-products together with any unwanted contaminants, are removed by filtration. The refined solution is then electrolysed in a cell fitted with a lead anode and an aluminium cathode. The cathode is immersed in the solution for 48 hours
