Elements in the Crystals Determine the Distribution of Bromine in Nonmetallic Particles of Crushed Waste Printed Circuit Boards

The recovery of waste printed circuit boards (WPCBs) has been a hot topic in the area of environmental science. WPCBs contain heavy metals (Cu, Zn, Pb, etc.) and nonmetals (fiberglass, plastics, and additives). Many technologies have been developed to recover the metals. However, little attention has been given to the disposal of nonmetals. Nonmetallic fractions originating from crushed WPCBs have become one of the largest hazardous waste streams during the recycling of e-wastes in China. Bromine is a major hazardous element in the plastic additives. In this study, we discovered an interesting phenomenon that bromine preferred to concentrate on the surface of fiberglass particles. The causes of this phenomenon were explained from the views of crystal structure of the nonmetallic particles and electron orbitals of the elements. We found that glass fibers have the ability to absorb bromine, because of chemical and physical adsorption. Na and Ca in the crystal structure of fiberglass captured bromine on the surface of fiberglass. Bromine in the nonmetals of crushed WPCBs can be removed by separating the fiberglass particles. This discovery contributes to the development of green technology for removing bromine from crushed WPCBs. Meanwhile, the toxicity of bromine should be a concern in regard to the reuse of fiberglass.