Environmentally sound technologies for recycling secondary lead

Abstract

Advances in hydrometallurgy are providing increasingly simple means for controlling the entire lead chain from concentrate to recycled lead. Used in parallel with pyrometallurgy, these processes allow furnace temperatures to be reduced to the minimum, which is essential for casting or alloying. Fumes and atmospheric pollution are minimized, furnace slags are digested, and most residues (other than purification cements) are non-toxic and convertible into marketable products. These new processes provide the cleanest and healthiest practicable means for recycling lead from batteries. By substituting melting for smelting, the heat requirement and cycle time per charge are reduced by more than half. A new hydrometallurgical plant could be installed alongside an existing pyrometallurgical plant without interference, doubling its potential capacity when operational (and more, if electrowinning is used). Over 99.5% of the lead originally present is recovered in tests of a combined PLACID–pyro plant. The average purity of electrowon PLACID lead is 99.995%. Results from the PLINT process should be similar. The purity of the lead chain can thereby be sustained through recycling. Perfect solid/paste separation is not mandatory, and PLINT-type plant units can be of any size. Such processes constitute a good basis for development of clean processes, which are suitable for use in Asian societies.