Guo Jiuyong, Guo Jie, Xu Zhenming
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, PR China.
J Hazard Mater. 2009 Sep 15;168(2-3):567-90. doi: 10.1016/j.jhazmat.2009.02.104. Epub 2009 Feb 26.
The major economic driving force for recycling of waste printed circuit boards (PCBs) is the value of the metallic fractions (MFs) of PCBs. The non-metallic fractions (NMFs), which take up almost 70wt% of waste PCBs, were treated by combustion or land filling in the past. However, combustion of the NMFs will cause the formation of highly toxic polybrominated dibenzodioxins and dibenzofurans (PBDD/Fs) while land filling of the NMFs will lead to secondary pollution caused by heavy metals and brominated flame retardants (BFRs) leaching to the groundwater. Therefore, recycling of the NMFs from waste PCBs is drawing more and more attention from the public and the governments. Currently, how to recycle the NMFs environmental soundly has become a significant topic in recycling of waste PCBs. In order to fulfill the better resource utilization of the NMFs, the compositions and characteristics of the NMFs, methods and outcomes of recycling the NMFs from waste PCBs and analysis and treatment for the hazardous substances contained in the NMFs were reviewed in this paper. Thermosetting resin matrix composites, thermoplastic matrix composites, concrete and viscoelastic materials are main applications for physical recycling of the NMFs. Chemical recycling methods consisting of pyrolysis, gasification, supercritical fluids depolymerization and hydrogenolytic degradation can be used to convert the NMFs to chemical feedstocks and fuels. The toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) can be used to determine the toxicity characteristic (TC) of the NMFs and to evaluate the environmental safety of products made from the recycled NMFs. It is believed that physical recycling of the NMFs has been a promising recycling method. Much more work should be done to develop comprehensive and industrialized usage of the NMFs recycled by physical methods. Chemical recycling methods have the advantages in eliminating hazardous substances in the NMFs. The trend in chemical recycling of the NMFs is to make the best of advantages over physical recycling of the NMFs to compensate its higher cost. Removing and treating the hazardous substances in the NMFs is an ultimate method to eliminate the pollution.
废旧印刷电路板（PCBs）回收利用的主要经济驱动力在于其金属成分（MFs）的价值。占废旧印刷电路板近70wt%的非金属成分（NMFs），过去是通过燃烧或填埋进行处理的。然而，非金属成分的燃烧会导致剧毒的多溴二苯并二恶英和二苯并呋喃（PBDD/Fs）的形成，而非金属成分的填埋会导致重金属和溴化阻燃剂（BFRs）渗入地下水造成二次污染。因此，从废旧印刷电路板中回收非金属成分越来越受到公众和政府的关注。目前，如何对非金属成分进行环境友好型回收已成为废旧印刷电路板回收领域的一个重要课题。为了更好地实现非金属成分的资源利用，本文综述了非金属成分的组成和特性、从废旧印刷电路板中回收非金属成分的方法和成果以及对非金属成分中所含有害物质的分析和处理。热固性树脂基复合材料、热塑性基体复合材料、混凝土和粘弹性材料是非金属成分物理回收的主要应用领域。由热解、气化、超临界流体解聚和氢解降解组成化学回收方法可用于将非金属成分转化为化学原料和燃料。毒性特性淋溶程序（TCLP）和合成沉淀淋溶程序（SPLP）可用于确定非金属成分的毒性特性（TC），并评估由回收的非金属成分制成的产品的环境安全性。人们认为，非金属成分的物理回收一直是一种很有前景的回收方法。在开发通过物理方法回收的非金属成分的综合和工业化用途方面，还需要做更多的工作。化学回收方法在消除非金属成分中的有害物质方面具有优势。非金属成分化学回收的趋势是充分利用其相对于物理回收的优势来弥补其较高的成本。去除和处理非金属成分中的有害物质是消除污染的最终方法。
