Sahle-Demessie Endalkachew, Mezgebe Bineyam, Dietrich Joshua, Shan Yonggui, Harmon Stephen, Lee Chun C
US Environmental Protection Agency, Office of Research and Development, Center for Environmental Solutions and Emergency Response, Cincinnati, OH 45268, USA.
Oak Ridge Institute for Science and Education, Oak Ridge, TN 37831, USA.
J Environ Chem Eng. 2021 Feb 1;9(1). doi: 10.1016/j.jece.2020.104943.
Electronic waste (e-waste) generation has been growing in volume worldwide, and the diversity of its material composition is increasing. Sustainable management of this material is critical to achieving a circular-economy and minimizing environmental and public health risks. This study's objective was to investigate the use of pyrolysis as a possible technique to recover valuable materials and energy from different components of e-waste as an alternative approach for limiting their disposal to landfills. The study includes investigating the potential environmental impact of thermal processing of e-waste. The mass loss and change in e-waste chemicals during pyrolysis were also considered. The energy recovery from pyrolysis was made in a horizontal tube furnace under anoxic and isothermal conditions of selected temperatures of 300 °C, 400 °C, and 500 °C. Critical metals that include the rare earth elements and other metals (such as In, Co, Li) and valuable metals (Au, Ag, Pt group) were recovered from electronic components. Pyrolysis produced liquid and gas mixtures of organic compounds that can be used as fuels. Still, the process also emitted particulate matter and semi-volatile organic products, and the remaining ash contained leachable pollutants. Furthermore, toxicity characteristics leaching procedure (TCLP) of e-waste and partly oxidized products were conducted to measure the levels of pollutants leached before and after pyrolysis at selected temperatures. TCLP result revealed the presence of heavy metals like As, Cr, Cd, and Pd. Lead was found at 160 mg/L in PCBs leachate, which exceeded the toxicity characteristics (TC) limit of 5 mg/L. Liquid sample analysis from TCLP also showed the presence of C-C components, including benzene. This study's results contribute to the development of practical recycling alternative approaches that could help reduce health risks and environmental problems and recover materials from e-waste. These results will also help assess the hazard risks that workers are exposed to semi-formal recycling centers.
全球电子垃圾（电子废弃物）的产生量一直在增加，其物质组成的多样性也在不断提高。对这种材料进行可持续管理对于实现循环经济以及将环境和公共健康风险降至最低至关重要。本研究的目的是调查热解作为一种可能的技术，从电子垃圾的不同组件中回收有价值的材料和能源，作为限制其填埋处理的替代方法。该研究包括调查电子垃圾热处理的潜在环境影响。还考虑了热解过程中电子垃圾化学物质的质量损失和变化。热解的能量回收是在水平管式炉中，在300℃、400℃和500℃的选定温度下的缺氧和等温条件下进行的。从电子元件中回收了包括稀土元素和其他金属（如铟、钴、锂）以及贵金属（金、银、铂族）在内的关键金属。热解产生了可作为燃料的有机化合物液体和气体混合物。然而，该过程还排放了颗粒物和半挥发性有机产物，剩余的灰分含有可浸出污染物。此外，还对电子垃圾及其部分氧化产物进行了毒性特征浸出程序（TCLP），以测量在选定温度下热解前后浸出的污染物水平。TCLP结果显示存在砷、铬、镉和钯等重金属。在多氯联苯渗滤液中发现铅含量为160毫克/升，超过了5毫克/升的毒性特征（TC）限值。TCLP的液体样品分析还显示存在包括苯在内的碳 - 碳成分。本研究结果有助于开发实用的回收替代方法，这有助于降低健康风险和环境问题，并从电子垃圾中回收材料。这些结果还将有助于评估工人在半正规回收中心所面临的危害风险。
