Study of the Transference Rules for Bromine in Waste Printed Circuit Boards during Microwave-Induced Pyrolysis

The production of waste printed circuit boards (WPCBs) has drawn increasing global concern, especially because the high bromine (Br) content (5–15%) places obstacles in the way of simple disposal techniques. Microwave-induced pyrolysis of WPCBs provides a promising way to dispose of these hazardous and resource-filled wastes. The transference rules for Br during microwave-induced pyrolysis have been investigated experimentally. It was found that the microwave energy could be used more efficiently to accelerate the heating rate and improve the final pyrolysis temperature by adding some activated carbon (AC) as microwave absorbents. The high temperature and rapid pyrolysis process promoted the yields of gaseous products and the decomposition of brominated compounds into hydrogen bromide and then benefited the capture of Br and the debromination of byproducts. The application of a calcium carbonate (CaCO3) layer overhead led to over 95% debromination of the liquid products and over 50% capture of the total Br. It can be concluded that the presented method is suitable for the control of Br transference in the recycling of WPCBs. This method can also be extended to the disposal of the electronic scraps. IMPLICATIONS Development of environmentally sound treatments for the comprehensive recycling of WPCBs and even waste electrical and electronic equipment (WEEE) is a hot issue all over the world. New ideas and technologies will be continuously developed. The idea of recycling WPCBs by microwave-induced pyrolysis coupled with the debrominating of pyrolysis products by a CaCO3 layer is just a novel one. It has great potential for industrial practice and its implementation will enrich the choices for WEEE recycling.