Recovery of Heavy Metals by Flotation from Incinerated Automobile Shredder Residues

Abstract

Every year in Japan, approximately 0.7-0.8 million tons of automobile shredder residue (ASR) are generated and most incinerated ASR is landfilled. Since the landfill capacity for industrial and domestic waste is limited, the recycling of ASR is becoming very important. The incinerated ASR contains relatively large amount of non ferrous metals. Neverthless, only a small amount of these metals is recycled, pointing out the need to increase the recycling rate of these metals in order to save resources and reduce the amount of materials to be discarded.
In this study, upgrading Cu and Zn from the incinerated ASR ash by means of flotation is described. In order to obtain the optimal condition, the effects of pH, grinding and the addition of reagents were investigated. As a result, it was found that grinding ash to c.a. 10 μm is necessary in order to obtain the optimum grade and recovery of Cu and Zn. Under the optimal conditions (i.e. pH 5; NaHS concentration of 21 kg/t; PAX concentration of 9 kg/t), Cu was upgraded from 3.2wt% to 8.7wt% recovering 49% of Cu. Moreover, Zn was upgraded from 1.4wt% to 2.8wt% recovering 36% of Zn. Cl content in both froth and tailings, on the other hand, was efficiently reduced from 3.3wt% to about 0.1wt%.