Copper
Copper is the world’s most important base metal by value and its price is a bellwether of world industrial production. Global mined copper production is around 18Mtpa, approximately a quarter of which is produced from oxide ores using hydrometallurgy.
The Company believes that its leaching technology has the potential to increase significantly the share of global copper produced using hydrometallurgical processes. Hydrometallurgically recovered copper is much more attractive to mine owners than the production of concentrates from sulphide ores as it results in the production of high value cathodes at the mine. When sold these realise almost 100% of the copper content, compared to concentrates where owners may receive up to 40% less.
Zinc
Global mined zinc production is around 12.7Mtpa. The vast majority (~95%) of world zinc metal production uses smelting to recover and refine zinc metal out of zinc-containing feed material such as zinc concentrates or zinc oxides.
Development of a new hydrometallurgical process route for zinc oxides has the potential to simplify zinc refining. MetaLeach has developed a novel (patents applied for) process for the solvent extraction of zinc from ammoniacal solutions. Test work has shown that zinc can be efficiently extracted using commercially available reagents in a single stage and stripped with acid solutions, with better efficiency and greater selectivity than has previously been reported.
The general flow sheet for the zinc process is straightforward and consists of leaching, purification and recovery stages. The nature of the leach stage depends upon a number of factors, notably the grade of ore and leaching kinetics. High grade, fast leaching ore would be readily accommodated by an agitated tank leach, whilst low grade, slow leaching ores would be better suited to heap leaching.
Depending upon the product desired, there may be no need for a solution purification stage, further simplifying the overall process flow sheet. A wide range of different oxide zinc mineralogies can be treated by AmmLeach® , including those with significant hemimorphite content which presently can only be treated using acid. The co-dissolution of silica and iron in the acid gives a very complex flow sheet. Although this AmmLeach® application is at an earlier stage of development than copper processing, the acid route requires ore containing >10% zinc to be economically viable, so for lower grade zinc oxide deposits of this type the benefits of the AmmLeach® process are absolute.