Separation of copper from plastic waste material by air classification and water flotation

The purpose of this research is to study air classification and water flotation as techniques to recover a large percentage of the copper currently being sent to landfills by metal recycling industries. These are appropriate techniques because they utilize internal plant streams which are the plant storm water and air from air conveyors used in material transport. The waste stream studied was a copper plastic waste stream that contains 3-13% copper with particle sizes between 0.5 and 5 mm. It is a crude chopped mixture that cannot be easily characterized. Air classification of the crude material could achieve an average of 60% copper recovery with 40% purity. Water flotation of the crude material could achieve an average of 60% copper recovery with 90% purity. A separation scheme is proposed that uses air classification columns that are followed by water flotation separators. The air classification operation removes the lighter fluff material. The water flotation operation purifies the recovered material. Based on the measurements made in this study, a minimum of 50% recovery of the input copper with a 90% purity can be obtained. For a 1000 tons/month feed of crude copper/plastic waste, this will result in approximately S2,000,000/year revenues (1994$) in copper and additional savings in landfill costs.