Recycle Technology for Recovering Resources and Products from Waste Printed Circuit Boards

TLDR

Printed circuit boards contain about 28 % metals, including high‑purity precious metals, making their recycling important for waste treatment and resource recovery, yet conventional chemical methods risk secondary pollution and mechanical methods such as shape separation and electrostatic separation are the main industry practices, though large‑scale recycling is still nascent. The study processed 400 kg of waste PCBs using an environmentally benign recycling technology. The recycling process involved mechanical two‑step crushing, corona electrostatic separation, and subsequent recovery of materials. The process effectively stripped metals from base plates, identified 0.6–1.2 mm particles as optimal for corona electrostatic separation, and recovered nonmetallic material at 80 % weight, broadening its industrial applicability.

Abstract

The printed circuit board (PCB) contains nearly 28% metals that are abundant non-ferrous metals such as Cu, Al, Sn, etc. The purity of precious metals in PCBs is more than 10 times higher than that of rich-content minerals. Therefore, recycling of PCBs is an important subject not only from the treatment of waste but also from the recovery of valuable materials. Chemical and mechanical methods are two traditional recycling processes for waste PCBs. However, the prospect of chemical methods will be limited since the emission of toxic liquid or gas brings secondary pollution to the environment during the process. Mechanical processes, such as shape separation, jigging, density-based separation, and electrostatic separation have been widely utilized in the recycling industry. But, recycling of waste PCBs is only beginning. In this study, a total of 400 kg of waste PCBs was processed by a recycle technology without negative impact to the environment. The technology contained mechanical two-step crushing, corona electrostatic separating, and recovery. The results indicated that (i) two-step crushing was an effect process to strip metals from base plates completely; (ii) the size of particles between 0.6 and 1.2 mm was suitable for corona electrostatic separating during industrial application; and (iii) the nonmetal of waste PCBs attained 80% weight of a kind of nonmetallic plate that expanded the applying prospect of waste nonmetallic materials.