Separation and Recovery of Copper Foil and Fabric from Waste Printed Circuit Boards by Decomposing Brominated Epoxy Resin Using Near Critical Water

Hongjun Kang 1

Qian Shao 2

Xingkui Guo 2

Alexandra Galaska 3

Yuyan Liu 1, Email

Zhanhu Guo 3, Email

1 School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 Xidazhi Street, Harbin 150001, China

2 College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China

3 Integrated Composites Laboratory (ICL), Department of Chemical & Bimolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA

Abstract

Waste printed circuit board (WPCB), a heterogeneous mixture of brominated epoxy resins (BERs), glass fibers and metals, has the challenge to separate and recover valuable materials. In this paper, an effective and benign near critical water (NCW) method was applied to decompose BERs to recover the glass fabric and metals. The effects of parameters including temperature, reaction time, feed ratio, acid-base catalyst, and size of WPCBs on the decomposition ratio of BERs were investigated. The results showed that the decomposition ratio of BERs reached a maximum value of 98.7% under the optimum conditions at 320 °C, reaction time of 150 min, feed ratio of 5 mL/g, HCl catalyst, and the size of 5×5 mm2. The gas chromatography–mass spectrometry (GC/MS) result showed that the main components of liquid decomposition product were phenol (69.8%) and its derivatives (17.8%). A probable mechanism of the decomposition reaction of BERs was proposed. After NCW treatment, the glass fabric and copper foils in the residue were easily recovered by a simple artificial screening separation. The surface of recovered fabric was very clean and no damages were observed. Meanwhile, the purity of copper foil reached 97.86%. This study provides a green technology to recover valuable materials from WPCBs.

Separation and Recovery of Copper Foil and Fabric from Waste Printed Circuit Boards by Decomposing Brominated Epoxy Resin Using Near Critical Water