Environmentally sound technologies for recycling secondary lead

Advances in hydrometallurgy are providing increasingly simple means for con trolling the entire lead chain from concentrate to recycled lead. Used in p arallel with pyrometallurgy, these processes allow furnace temperatures to be reduced to the minimum, which is essential for casting or alloying. Fume s and atmospheric pollution are minimized, furnace slags are digested, and most residues (other than purification cements) are non-toxic and convertib le into marketable products. These new processes provide the cleanest and h ealthiest practicable means for recycling lead from batteries. By substitut ing melting for smelting, the heat requirement and cycle time per charge ar e reduced by more than half. A new hydrometallurgical plant could be instal led alongside an existing pyrometallurgical plant without interference, dou bling its potential capacity when operational (and more, if electrowinning is used). Over 99.5% of the lead originally present is recovered in tests o f a combined PLACID-pyro plant. The average purity of electrowon PLACID lea d is 99.995%. Results from the FLINT process should be similar. The purity of the lead chain can thereby be sustained through recycling. Perfect solid /paste separation is not mandatory, and FLINT-type plant units can be of an y size. Such processes constitute a good basis for development of clean pro cesses, which are suitable for use in Asian societies. (C) 2000 Elsevier Sc ience S.A. All rights reserved.