A Novel Recycling Approach for Transforming Waste Printed Circuit Boards into a Material Resource

Abstract

The recovery of materials from urban waste has become progressively more important with wastes providing a variety of resources. This study focuses on the recycling of electronic printed circuit boards (PCBs) from mobile phones, computers, TVs, white goods, and micro-processors etc. that contain significant amounts of hazardous/toxic components along with a variety of metals, ceramics and polymers. Both formal and informal sectors are engaged worldwide in recycling such e-waste to recover precious and other metals (upto 40-70% of value). However poor recycling techniques, especially in developing countries, generate high levels of environmental pollution that affects both the ecosystems and the people living within or near the main recycling areas. Various e-waste recycling methods used in the informal sector include manual dismantling, open burning of PCBs, plastic chipping and melting, burning wires to recover copper, acid & cyanide salt leaching, and inadequate metallurgical treatments. These activities release dust particles loaded with heavy metals and flame retardants into the atmosphere that may re-deposit near the emission site, or be transported over long distances depending on their size. Significant levels of environmental pollution are thus associated with recycling e-waste.This study presents an environmentally sustainable solution to e-waste management and reducing associated pollution during recycling. In this study, waste PCBs were heat treated in the temperature range 1150-1350oC for periods of up to 20minutes in an Argon atmosphere. Key metallic constituents namely Cu, Sn and Pb showed a tendency to segregate out in the form of copper rich and Sn rich metallic balls. Minor elements such as Al, Fe, Mg, Ni, Pd, Pt and Zn segregated along with metallic droplets. Such high temperatures led to the removal of hazardous lead and the recovery of highly concentrated copper alloys and precious metals. Pyrolysis of PCBs also generated a carbon rich residue containing traces of Sn and very low levels of copper. Various ceramic impurities present precipitated out as slag and did not interfere with metal recovery.