Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, PR China.
Chemosphere. 2020 Feb;240:124867. doi: 10.1016/j.chemosphere.2019.124867. Epub 2019 Sep 14.
Phase transfer catalysts (PTCs) have been shown to be effective in lowering the limitation of mass transfer between aqueous oxidant MnO and NAPLs in in-situ chemical oxidation (ISCO) technologies for remediation of NAPLs. This work researched the effects of pentyltriphenylphosphonium bromide (PTPP, used as the representative PTC) for the enhancement of TCE oxidation, the extent of different treatment effects contributions and generalizability of phase transfer. Experimental results revealed that MnO exchanged with Br in PTPP by ion exchange mechanism and then transferred to NAPL phase due to biphasic nature of PTPP-MnO. PTPP enhanced TCE dissolution in aqueous phase but had no significant effect on TCE solubilization. Enhanced TCE dissolution gradually weakened after 2.0 h and disappeared after 5.5 h, while the percentage of MnO in phase transfer was 14.8% at 7.5 h, which indicated that dissolution acceleration was only effective at initial stage of reaction (0-2.5 h). Therefore, persistent phase transfer process played the leading role in TCE remediation enhancement. Moreover, for different NAPL phase, more effective phase transfer could be achieved in NAPLs with higher solubility and weaker hydrophobicity. The best-fit polynomial relationship (R = 0.992) existed between the percentage amount of MnO transferred and the solubility of NAPL.
相转移催化剂 (PTCs) 已被证明可有效降低原位化学氧化 (ISCO) 技术中 MnO 氧化剂与 NAPLs 之间传质的限制，从而修复 NAPLs。本工作研究了五正丁基三苯基溴化膦 (PTPP，用作代表性 PTC) 对增强 TCE 氧化的影响、不同处理效果的贡献程度以及相转移的普遍性。实验结果表明，MnO 通过离子交换机制与 PTPP 中的 Br 交换，然后由于 PTPP-MnO 的两相性质而转移到 NAPL 相中。PTPP 增强了 TCE 在水相中的溶解，但对 TCE 的增溶没有显著影响。增强的 TCE 溶解逐渐在 2.0 h 后减弱，并在 5.5 h 后消失，而在 7.5 h 时，相转移中的 MnO 百分比为 14.8%，这表明溶解加速仅在反应的初始阶段（0-2.5 h）有效。因此，持续的相转移过程在增强 TCE 修复方面起着主导作用。此外，对于不同的 NAPL 相，在具有更高溶解度和较弱疏水性的 NAPLs 中可以实现更有效的相转移。转移的 MnO 百分比与 NAPL 溶解度之间存在最佳拟合多项式关系 (R=0.992)。
