A contribution to integrated metal valorisation in zinc hydrometallurgy

Abstract

Zinc belongs to the group of non-ferrous, widely used, metals. After aluminium and copper, zinc is the third non-ferrous metal according to the world production of 12.7 million tons in 2012. Nowadays, it is almost exclusively produced by processing sulphide concentrates in hydrometallurgical procedure. Zinc concentrates contain a series of commercially important metals, such as cadmium, lead, silver, copper, cobalt, nickel, germanium, indium, gallium, etc. Zinc producers have an integrated approach to zinc minerals processing, simultaneously valorising, from raw materials, beside zinc, a large number of present metals. This procedure has a complete economical justification, being at the same time in accordance with sustainable development doctrine. This paper shows the method of effectively valorising this metal from waste sludge that is obtained in zinc hydrometallurgy and contains 0.6 to 1% of cobalt. Applying a developed procedure in which cobalt from sludge is firstly concentrated, and then treated, blue ceramic pigment cobalt-olivine is synthesized. Laboratory process of cobalt-olivine synthesis has pilot-plant confirmation and obtained pigment is successfully used on glaze test tiles baked in industrial furnace.