E-scrap processing: Theory and practice

Abstract

The importance of recycling the waste electrical and electronic equipment (WEEE), in recent years, has been taken into increasing concern and consideration not only by the government, but also by their hazardous material contents. Electronic waste can be defined as a mixture of various metals, particularly copper, aluminum and steel, with various types of plastics and ceramics. Recycling of electronic waste is an important subject not only from the point of waste treatment, but also from the recovery aspect of valuable materials. Pyrometallurgical processing has been a traditional technology for recovery of the precious metals from waste electronic equipment. In the past two decades, the most active research area on recovery of metals from electronic scraps is recovering the precious metals using the hydrometallurgical techniques. Compared with the pyrometallurgical processing, the hydrometallurgical method is more exact, more predictable and more easily controlled. In the last decade, the recovery of metals by biotechnology has been one of the most promising technologies. Biometallurgy has the potential for a major technology breakthrough for the materials and minerals industry due to a great interest shown by the major international companies for this new technology. Understanding the biochemical processes, involved in treatments of metals, has been the subject to growing investigations for the last 20 years. At present, the research and development are in progress for a number of metals such as copper, nickel, cobalt, zinc, gold and silver. However, the activity of leaching bacteria is applied for recovery of gold and silver only to remove the interfering metal sulfides from ore bearing the precious metals prior to the cyanidation treatment. Recent research trend is to use the combined methods for optimal results.