Advanced degradation of brominated epoxy resin and simultaneous transformation of glass fiber from waste printed circuit boards by improved supercritical water oxidation processes.
Advanced degradation of brominated epoxy resin and simultaneous transformation of glass fiber from waste printed circuit boards by improved supercritical water oxidation processes.
复制标题
DOI：
10.1016/j.wasman.2016.05.022
复制
发表时间：
2016-10
期刊：
影响因子：
8.1
通讯作者：
Kang-Xuan Liu;Zhi-yuan Zhang;Fu-Shen Zhang
中科院分区：
文献类型：
--
作者：
Kang-Xuan Liu;Zhi-yuan Zhang;Fu-Shen Zhang
这项工作研究了各种超临界水氧化 (SCWO) 系统，即 SCWO1（仅水）、SCWO2（水 + H2O2）和 SCWO3（水 + H2O2/NaOH），用于废弃印刷电路板 (PCB) 的解毒和回收。应用响应面法 (RSM) 来优化最佳 SCWO3 系统的操作条件。最佳脱溴反应条件为：NaOH用量0.21 g，H2O2用量9.04 mL，时间39.7 min，最大脱溴效率95.14%。方差分析表明，影响脱溴效率的因素顺序为：NaOH > H2O2 > 时间。机理研究表明，超临界水中 NaOH 的解离离子通过消除反应和亲核取代促进了溴化环氧树脂 (BER) 的脱溴。 H2O2产生的HO2自由基点可以诱导苯酚环氧化打开（BERs的中间体），苯酚环被彻底降解形成碳氢化合物、CO2、H2O和NaBr。此外，OH−和SiO2之间的碱-硅反应引起玻璃纤维的相变，同时转化为钙长石和钠长石。废PCB在H2O2/NaOH改进的SCWO系统中被充分降解为有用产品，同时转化为功能材料。这些发现有助于废PCB的高效回收。
This work investigated various supercritical water oxidation (SCWO) systems, i.e. SCWO1 (only water), SCWO2 (water + H2O2) and SCWO3 (water + H2O2/NaOH), for waste printed circuit boards (PCBs) detoxification and recycling. Response surface methodology (RSM) was applied to optimize the operating conditions of the optimal SCWO3 systems. The optimal reaction conditions for debromination were found to be the NaOH of 0.21 g, the H2O2volume of 9.04 mL, the time of 39.7 min, maximum debromination efficiency of 95.14%. Variance analysis indicated that the factors influencing debromination efficiency was in the sequence of NaOH > H2O2> time. Mechanism studies indicated that the dissociated ions from NaOH in supercritical water promoted the debromination of brominated epoxy resins (BERs) through an elimination reaction and nucleophilic substitution. HO2radical dot, produced by H2O2could induce the oxidation of phenol ring to open (intermediates of BERs), which were thoroughly degraded to form hydrocarbons, CO2, H2O and NaBr. In addition, the alkali-silica reaction between OH−and SiO2induced the phase transformation of glass fibers, which were simultaneously converted into anorthite and albite. Waste PCBs in H2O2/NaOH improved SCWO system were fully degraded into useful products and simultaneously transformed into functional materials. These findings are helpful for efficient recycling of waste PCBs.