School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
J Hazard Mater. 2020 Feb 5;383:121234. doi: 10.1016/j.jhazmat.2019.121234. Epub 2019 Sep 16.
Pyrolysis is an important pre-treatment technology for pyrometallurgy, which could reduce pollution and recover materials from waste printed circuit boards (WPCBs). However, present studies on mechanism of pyrolysis were insufficient, which results in the unclear of controlling reaction rate and inhibiting side reaction. To further develop pyrolysis technology, the in-depth research on the pyrolysis mechanism is necessary. In this study, we investigated the thermal decomposition process and pyrolysis pathways from macromonomers to products of WPCBs. The results showed that HBr was produced at the initial stage of pyrolysis. Then, the resin body depolymerized into macromonomers, followed by random rupture and free radical reactions to form pyrolysis products. Besides, possible mechanism for bisphenol A thermal decomposing was analyzed by bond energy. The results suggested that methyl groups in bisphenol A would be preferentially removed because of low bond energy. The six possible pathways may occur simultaneously when energy sufficient. Moreover, the mechanism function was determined by Škvára-Šesták method as: G(α)=-ln 1-α, which indicated pyrolysis reaction agreed with the model of random nucleation followed by random growth. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis.
热解是火法冶金的重要预处理技术，可以减少污染并从废弃印刷电路板（WPCBs）中回收材料。然而，目前对热解机制的研究还不够充分，导致反应速率控制和抑制副反应的方法不明确。为了进一步发展热解技术，有必要对热解机制进行深入研究。在这项研究中，我们研究了从大分子单体到 WPCBs 产物的热分解过程和热解途径。结果表明，热解初期会产生 HBr。然后，树脂体解聚成大分子单体，随后发生随机断裂和自由基反应，形成热解产物。此外，还通过键能分析了双酚 A 热分解的可能机理。结果表明，由于键能较低，双酚 A 中的甲基基团会优先被去除。当能量足够时，这六个可能的途径可能会同时发生。此外，用 Škvára-Šesták 方法确定了机理函数为：G(α)=-ln(1-α)，这表明热解反应符合随机成核随后随机生长的模型。本研究为 WPCBs 热解的污染控制、工艺优化和反应器设计提供了理论基础。
