Separating Criterion of Pb, Cd, Bi and Zn from Metallic Particles of Crushed Electronic Wastes by Vacuum Evaporation

Abstract

The crushing process is usually adopted during the treatment of electronic wastes. Mixed metallic particles can be obtained after several kinds of separation methods. Most of the metals exist as elementary substances and their vapor pressure is quite different. For the metals with high vapor pressure, vacuum metallurgy separation is used to separate these metals. However, the vacuum evaporation rule of metallic particles is different from the traditional theory. Satisfactory parameters for separating these metallic particles could not be obtained merely according to the boiling point difference between metals. In this paper, the evaporation kinetics and mechanism of single metallic particles (Pb, Zn, Cd, and Bi) are investigated first. Then the criterion of separating these metals from each other is obtained. Under the instruction of separation criterion, different kinds of mixed metallic particles are successfully separated with the separation efficiency of the target metal more than 90 wt%. This study provides theoretical foundations for separating the heavy metals with high vapor pressure from e-wastes.

Keywords:

• evaporation kinetics
• electronic waste
• metallic particles
• separation criterion

ACKNOWLEDGEMENTS

This project was supported by the National High Technology Research and Development Program of China (863 program 2009AA06Z318), the National Natural Science Foundation of China (21077071), Shanghai Tongji Gao TingYao Environmental Science & Technology Development Foundation, and the Scholarship Award for Excellent Doctoral Student granted by the Ministry of Education.