Hydrometallurgy—an environmentally sustainable technology?

Abstract

Hydrometallurgy has long been hailed as the environmentally friendly alternative to pyrometallurgy. There are, however, flaws in this argument, not least the difficulties, when hydrometallurgy is employed, of avoiding water pollution and the need to discharge solids which may be far from inert. A good example of this situation is that of jarosite, the main waste solid from the roast/leach/electrowin process commonly used for zinc recovery.

Pyrometallurgy, on the other hand, certainly has the potential to pollute the atmosphere, but the gaseous sulphur emissions can be positively dealt with (and in some circumstances can contribute to revenues) and the slag waste products can be of an inert nature.

Furthermore, apart from zinc, no major commercial plants for the hydrometallurgical treatment of primary copper or lead concentrates have yet been seriously considered, nor will be in the short-term future, despite claims for several new processes. Where hydrometallurgical operations are common, as mentioned previously for zinc, and also for aluminium and gold, environmental challenges still exist.

In this paper hydrometallurgy is examined from an environmental standpoint, in the light of Best Available Technigues (BAT) and Best Practical Environmental Options (BPEO). Conclusions with regard to the continuing development of hydrometallurgy for the extraction and purification of major metals are drawn.