Microbial technology for metal recovery from e-waste printed circuit boards

Abstract

End-of-Life Electrical and Electronic Equipments commonalty know as e-waste is an emerging problem with developed as well as developing nations. Our obsession on electrical and electronic equipments, the unquenchable desire for latest devices and rapid advances in technology has resulted in the world wide generation of huge amount of e-waste. Printed circuit boards (PCBs), the core processing unit of electronic devices contain complex mixture of ceramics, metals and polymers. PCBs are considered as secondary source of several metals. Only a small fraction of this being treated or recycled properly; lion share of e-waste is dumped as landfills or incinerated. Till date no standard eco-friendly technique is available for their safe disposal. In recent decades significant attempts have been done for developing pyromet allurgical and hydrometallurgical technology for recovery of metals from PCBs, but these processes are also non sustainable due to secondary pollution they create and they are cost intensive. Microbial biotechnology, based mainly on the potential of microorganisms to generate lixiviants which mobilized metals from PCBs. Iron and sulphur oxidizing bacteria generate ferric iron and protons which extract several metals in aqueous phase. Cynogenic microorganisms are effectively used for extraction of gold and silver from PCBs. Some fungi are also reported for metal solubilisation fro PCBs by generating organic acids. This technology is considered a novel approach to mobilized metals from various types of PCBs. The main advantage of microbial technology would it can work with dilute waste streams, work at ambient temperatures and pressures, it is cost effective, reduce environmental impacts and generate minimum secondary waste. Thus this chapter explores and furnished the detailed on microorganism based technology for extractions of base and precious metals from e-waste PCBs.