New technology for recovering residual metals from nonmetallic fractions of waste printed circuit boards.
Recycling of waste printed circuit boards is important for environmental protection and sustainable resource utilization. Corona electrostatic separation has been widely used to recycle metals from waste printed circuit boards, but it has poor separation efficiency for finer sized fractions. In this study, a new process of vibrated gas-solid fluidized bed was used to recycle residual metals from nonmetallic fractions, which were treated using the corona electrostatic separation technology. The effects of three main parameters, i.e., vibration frequency, superficial air flow velocity, and fluidizing time on gravity segregation, were investigated using a vibrating gas-solid fluidized bed. Each size fraction had its own optimum parameters. Corresponding to their optimal segregation performance, the products from each experiment were analyzed using an X-ray fluorescence (XRF) and a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). From the results, it can be seen that the metal recoveries of -1+0.5mm, -0.5+0.25mm, and -0.25mm size fractions were 86.39%, 82.22% and 76.63%, respectively. After separation, each metal content in the -1+0.5 or -0.5+0.25mm size fraction reduced to 1% or less, while the Fe and Cu contents are up to 2.57% and 1.50%, respectively, in the -0.25mm size fraction. Images of the nonmetallic fractions with a size of -0.25mm indicated that a considerable amount of clavate glass fibers existed in these nonmetallic fractions, which may explain why fine particles had the poorest segregation performance.
School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China; Shanghai Cooperative Centre for WEEE Recycling, Shanghai Second Polytechnic University, Shanghai 201209, China.
Guangwen
G
Zhang
School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China; Advanced Analysis & Computation Center, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China; Shanghai Cooperative Centre for WEEE Recycling, Shanghai Second Polytechnic University, Shanghai 201209, China. Electronic address: yqhe@cumt.edu.cn.
Yaqun
Y
He
School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China.
Haifeng
H
Wang
Advanced Analysis & Computation Center, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China; Shanghai Cooperative Centre for WEEE Recycling, Shanghai Second Polytechnic University, Shanghai 201209, China.
Tao
T
Zhang
Advanced Analysis & Computation Center, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China.
Shuai
S
Wang
School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China.
Xing
X
Yang
School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China.
Wencheng
W
Xia
D059029:Electronic Waste; D008670:Metals; D059027:Recycling
D008670:Metals
Nonmetallic fractions; Residual metals; Vibrated gas-solid fluidized bed; Waste printed circuit boards