College of Geology and Environment, Xi'an University of Science and Technology, Xi'an 710054, China; Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation, Xi'an 710054, China.
College of Geology and Environment, Xi'an University of Science and Technology, Xi'an 710054, China.
Waste Manag. 2019 Dec;100:191-198. doi: 10.1016/j.wasman.2019.09.022. Epub 2019 Sep 18.
Waste printed circuit boards (PCBs) contain a high level of brominated flame retardants (BFRs), among which polybrominated biphenyl ethers (PBDEs) are the most widely used additive BFRs. PBDEs are considered to be a type of persistent organic pollutants (POPs). The efficient removal/degradation of PBDEs in waste PCBs is an urgent problem in electronic waste treatment, but the degradation of PBDEs is a great challenge due to their extreme stability and persistence in nature. In this study, a novel management strategy was developed for removal and degradation of PBDEs in waste PCBs by using a simple subcritical methanol (SubCM) process. The results showed that reaction temperature, residence time, solid-to-liquid ratio, and additive NaOH are key factors influencing the removal of PBDEs from waste PCBs. Under optimal conditions (200 °C, 60 min, 1:20 g/mL), the removal efficiency of ∑PBDEs from waste PCBs could reach 91.3% and 98.8% for the proposed process of SubCM and SubCM + NaOH, respectively. When the temperature is below 200 °C, highly brominated PBDEs congeners in waste PCBs were degraded into 2,'3,4',6-Tetrabromodiphenyl ether (BDE71) and 2,4,4'-Tribromodiphenyl ether (BDE28) after SubCM treatment. 4-Bromophenyl ether (BDE4) and diphenyl ether were generated by the further debromination of BDE71 and BDE28 with the increase of treatment temperature. The debromination temperature of PBDEs congeners in SubCM could be markedly lowered by adding 4 g/L of NaOH. The complete debromination of PBDEs congeners in waste PCBs could be achieved at 300 °C and 250 °C for the developed process of SubCM and SubCM + NaOH, respectively.
废弃印刷电路板（PCBs）含有高水平的溴化阻燃剂（BFRs），其中多溴联苯醚（PBDEs）是最广泛使用的添加型 BFRs。PBDEs 被认为是一种持久性有机污染物（POPs）。有效去除/降解废 PCB 中的 PBDEs 是电子废物处理中的一个紧迫问题，但由于 PBDEs 在自然界中的极端稳定性和持久性，其降解具有很大的挑战性。在这项研究中，通过使用简单的亚临界甲醇（SubCM）工艺，开发了一种从废 PCB 中去除和降解 PBDEs 的新型管理策略。结果表明，反应温度、停留时间、固液比和添加剂 NaOH 是影响废 PCB 中 PBDEs 去除的关键因素。在最佳条件下（200°C，60min，1:20g/mL），废 PCB 中∑PBDEs 的去除效率可分别达到 91.3%和 98.8%，对于提出的 SubCM 和 SubCM+NaOH 工艺。当温度低于 200°C 时，废 PCB 中高溴化 PBDEs 同系物在 SubCM 处理后降解为 2'，3'，4'，6-四溴二苯醚（BDE71）和 2,4,4'-三溴二苯醚（BDE28）。随着处理温度的升高，BDE71 和 BDE28 进一步脱溴生成 4-溴苯醚（BDE4）和二苯醚。通过添加 4g/L 的 NaOH，可显著降低 SubCM 中 PBDEs 同系物的脱溴温度。开发的 SubCM 和 SubCM+NaOH 工艺分别可在 300°C 和 250°C 下实现废 PCB 中 PBDEs 同系物的完全脱溴。
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