A new way to recycle electronic circuit boards
You've probably read that China is one of the world's largest producer of greenhouse gases and not really concerned by the environment. In fact, this is not really true. China is involved in many eco-friendly research projects. A recent American Chemical Society's Weekly PressPac briefly describes how Chinese scientists have developed a new recycling method that could transform old computers into useful objects, such as park benches and fences. (scroll to article #4 in the PressPac). The researchers have used fibers and resins of waste printed circuit boards (PCBs) which previously were considered as worthless. As said the lead researcher, 'there is no doubt that the technique has potential in the industry for recycling nonmetallic materials of PCBs.' But read more...
You can see above Cu particles (a) and nonmetallic materials (b) of pulverized waste PCBs. "The waste PCBs used in the study are a kind of woven glass fabric copper clad laminate without electronic elements, so the metallic portion only consists of Cu. The Cu particles and nonmetallic materials after two-step crushing and electrostatic separating were shown in this figure. (Credit: Shanghai Jiao Tong University).
This project is being led by Zhenming Xu and his colleagues Jie Guo, Bin Cao and Jiuyong Guo of the School of Environmental Science and Engineering at the Shanghai Jiao Tong University, China.
This research work has been published in the Environmental Science & Technology journal under the title "A Plate Produced by Nonmetallic Materials of Pulverized Waste Printed Circuit Boards" (Volume 42, Issue 14, Pages 5267–5271, June 17, 2008).
Here is an excerpt from the abstract. "Noble metals and Cu mainly are recycled in treating waste printed circuit boards (PCBs), and a large amount of nonmetallic materials in PCBs are disposed of by combustion or landfill, which may cause secondary pollution and resource-wasting. In this study, a kind of nonmetallic plate (NMP) has been produced by nonmetallic materials of pulverized waste PCBs. The NMP is produced by a self-made hot-press former through adding resin paste as a bonding agent. Furthermore, microshapes of nonmetallic materials and effects of the contents and particle sizes of nonmetallic materials on mechanical properties of the NMP are investigated. [...] This novel technique offers a possibility for recycling of nonmetallic materials of PCBs and resolving the environmental pollutions during recycling of PCBs."
Here is the beginning of the introduction of the full paper (PDF format, 5 pages, 9.48 MB). "Electronic waste is becoming a global topic as quantities of electrical and electronic equipment become obsolete. Printed circuit boards (PCBs) form about 3% by weight of the total amount of electronic waste. Recycling of PCBs is an important subject not only from the treatment of waste but also from the recovery of valuable materials. Mechanical-physical processes are attracting more attention than hydrometallurgy and pyrometallurgy. The mechanical-physical approach involves disassembling, crushing, and separating processes. The aim of crushing is to strip metal from the base plates of waste PCBs. Then separating processes, such as shape separation, jigging, and density-based separation are used to separate the metals and nonmetallic materials from pulverized PCBs. Metals such as Cu, Al, Sn, are sent to recovery operations. However, significant quantities of nonmetallic materials in PCBs (up to 70 wt %) present an especially difficult challenge for recycling.
And here is a description of what the researchers have achieved. "In order to take full advantage of nonmetallic materials of waste PCBs, a novel technique has been developed to recycle the nonmetallic materials of waste PCBs in this study. The nonmetallic materials were used to produce the nonmetallic plate (NMP) through adding resin paste as a bonding agent by a self-made hot-press former. Furthermore, effects of the contents and particle sizes of nonmetallic materials on mechanical properties of the NMP were investigated. The aim of this research is to develop a new technique for recycling nonmetallic materials of PCBs and resolving the environmental pollution during recycling of PCBs."
Sources: American Chemical Society's Weekly PressPac, July 30, 2008; and various websites
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