The application of mineral processing techniques for the recovery of metal from post-consumer wastes

Abstract Mineral processing techniques are dominant, and have a very wide field of application, in the secondary metals industries — only the final stages of raw material production involve any chemical operations. There are many basic similarities between primary and secondary feeds — in general the values and gangue materials can be differentiated from each other by several differences in physical properties — however, there are many difficulties encountered in applying techniques developed for separation of minerals to post-consumer waste. Primary feeds to mills are homogeneous when compared to the feed treated by a secondary operation — the heterogeneous nature of scrap feeds causes a lot of problems to the processor. Other characteristics of waste tend to be higher metal content (and metal, rather than mineral, particles), high liberation sizes, and unusual particle shapes. Nearly all methods of concentration utilised in the recycling industries have been developed from mineral beneficiation technology — the major exception is eddy current separation which relies on the presence of large conducting particles (such as the fist sized chunks of aluminium produced in autoshredding). At present applications of eddy current separators are almost exclusively for material reclamation — as eddy current separators suitable for finer feeds are developed it seems likely that they will be applied to primary mineral feeds.