School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China; Engineering Research Centre for Clean Production of Textile Dyeing and Printing, Ministry of Education, Wuhan Textile University, Wuhan, 430073, China.
School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China.
Chemosphere. 2021 Oct;280:130804. doi: 10.1016/j.chemosphere.2021.130804. Epub 2021 May 5.
Pyrolysis is a promising method for the recovery of waste printed circuit boards (WPCBs), but few researches have noticed the influence of in-situ metals. This study conducted a series of comparisons between metal-free leftover pieces (LP) and intact boards (IB), including pyrolysis characteristics, volatile emission, kinetics, and thermodynamic parameters. The thermo-gravimetry (TG) analyses indicated that both the samples presented predominant mass loss in narrow temperature intervals, and characteristic pyrolysis temperatures of IB were approximately 15 °C lower than those of LP. Dominant constituents in evolved gases were detected by Fourier-transform infrared spectrometry as CO, phenol, bromophenol, ethers, ketones, and aldehydes, and metals accelerated the generation of light hydrocarbons and aromatic compounds. The activation energy and thermodynamic parameters were calculated and compared, and the results verified the presence of in-situ metals led to a lower energy barrier and higher reaction extent. Moreover, conversion behaviors of Cu, Fe, Sn, and Pb manifested the formation of metal bromides and implied the reduction of brominated volatiles. The obtained results confirmed the catalytic effect of in-situ metals on PCBs pyrolysis and their bromine fixation abilities. This study contributes to fundamental knowledge that can be used to guide the pyrolysis of WPCBs.
热解是一种有前途的回收废印刷电路板 (WPCBs) 的方法，但很少有研究注意到原位金属的影响。本研究对无金属剩余物 (LP) 和完整电路板 (IB) 进行了一系列比较，包括热解特性、挥发性排放、动力学和热力学参数。热重 (TG) 分析表明，两种样品在狭窄的温度间隔内呈现主要的质量损失，IB 的特征热解温度比 LP 低约 15°C。傅里叶变换红外光谱检测到挥发气体中的主要成分有 CO、苯酚、溴苯酚、醚、酮和醛，金属加速了低碳烃和芳烃的生成。计算并比较了活化能和热力学参数，结果证实了原位金属的存在导致了较低的能量势垒和更高的反应程度。此外，Cu、Fe、Sn 和 Pb 的转化行为表明金属溴化物的形成以及溴化挥发物的减少。研究结果证实了原位金属对 PCB 热解的催化作用及其溴固定能力。本研究有助于指导 WPCBs 热解的基础理论知识。
