Lead and Zinc
Zinc normally occurs in the sulphide form although occurs also as oxide and silicate where different processing techniques are required for ore processing.
In processing zinc sulphide the ore is calcined by roasting in furnaces and oxidising to zinc oxide. The oxide is then subjected to a leaching process using sulphuric acid as the leaching liquor. A neutral leach at around PH 5 and an acid leach at PH 2.5 are carried out to dissolve all the zinc values into the sulphuric acid. Some plants use an additional hot leach thickening stage to enhance recover even further. A counter current decantation system is normally used with the overflow liquor from the neutral thickening stage reporting to the purification stage.
During all these stages of leaching flocculants are used to promote rapid settlement and clarification of the liquor.
For neutral leach the recommended sedimentation reagents are:
For acid leach (and hot acid leach) then the recommended sedimentation