膨润土负载纳米铁镍同步修复地下水中三氯乙烯和六价铬复合污染

邓日欣; 罗伟嘉; 韩奕彤; 李志雄; 陈家玮

doi:10.15898/j.cnki.11-2131/td.201801280013

膨润土负载纳米铁镍同步修复地下水中三氯乙烯和六价铬复合污染

Simultaneous Removal of TCE and Cr(Ⅵ) in Groundwater by Using Bentonite-supported Nanoscale Fe/Ni

摘要

摘要: 纳米零价铁原位注射修复地下水污染是近年发展的新技术，以往研究多侧重于单一目标污染物的去除效果及作用机理，但是地下水多种污染物共存问题不容忽视。本文针对典型污染物三氯乙烯TCE和六价铬Cr（Ⅵ），运用合成的活性高、稳定性强的膨润土负载纳米铁镍（B-Fe/Ni）开展修复实验，研究B-Fe/Ni对TCE和Cr（Ⅵ）共存复合污染的修复效果及其作用机制。通过一步法合成B-Fe/Ni，对TCE和不同浓度Cr（Ⅵ）混合污染的去除进行试验研究，对反应前后的样品B-Fe/Ni进行表征，并跟踪反应过程中TCE和Cr（Ⅵ）的浓度变化。结果表明：B-Fe/Ni同步去除水中TCE和Cr（Ⅵ）快速高效，50 mg/L Cr（Ⅵ）在2 h内能被B-Fe/Ni（1 g/L）完全去除而不受共存TCE（0.1 mmol/L）的影响，然而TCE降解速率会随共存Cr（Ⅵ）的浓度（0、10、30、50 mg/L）增大而降低。经透射电镜-电子能谱及X射线光电子能谱表征验证，这是由于B-Fe/Ni与Cr（Ⅵ）快速反应，生成部分Fe-Cr共沉淀会覆盖B-Fe/Ni表面的活性位点，抑制了TCE的降解，但通过分析TCE降解产物可知，B-Fe/Ni同样能对TCE完全脱氯。因此，B-Fe/Ni适用于地下水复合污染修复，实际应用时需考虑多种污染物共存的相互影响，选择适宜试剂用量和注射方式，这对纳米零价铁修复技术的发展具有重要理论意义和应用参考价值。

Abstract:
BACKGROUNDThe injection of nanoscale zero valent iron particles (nZVI) into groundwater has been recently developed as an in-situ groundwater remediation technology. Most researches focused on how to remove a single type pollutant and the related mechanism. However, cases on the coexisting multiple pollutants in groundwater should not be ignored.
OBJECTIVESTo synthesize the bentonite-supported nanoscale Fe/Ni bimetals(B-Fe/Ni), in order to remove typical pollutants of trichloroethylene (TCE) and hexavalent chromiumCr(Ⅵ) which exhibit high reactivity and are more stable to remediate contaminated water. Also, to assess the performance of B-Fe/Ni on the removal of coexisting TCE and Cr(Ⅵ) and to determine the reaction mechanism.
METHODSB-Fe/Ni was synthesized by one-step method and the batch experiments were conducted on the removal of TCE coexisted with different concentration of Cr(Ⅵ) by B-Fe/Ni. The samples of B-Fe/Ni were characterized before and after the reaction, and the contents of TCE and Cr(Ⅵ) were also monitored.
RESULTSB-Fe/Ni can efficiently remediate Cr(Ⅵ) and TCE in water. B-Fe/Ni (1 g/L) could completely remove Cr(Ⅵ) (50 mg/L) in 2 h in the presence of coexisting TCE (0.1 mmol/L). However, the degradation rate of TCE by B-Fe/Ni was decreased with increased initial concentration of Cr(Ⅵ) (0, 10, 30, 50 mg/L). According to TEM-EDS and XPS for B-Fe/Ni before and after reaction, it is shown that Fe-Cr co-precipitation from the fast interaction of B-Fe/Ni with Cr(Ⅵ) occupied the reactive sites on the surface of B-Fe/Ni, mitigating the degradation of TCE. According to the final products of TCE degradation, it is shown that TCE was completely dechlorinated.
CONCLUSIONSB-Fe/Ni is suitable for the remediation of groundwater combined pollution. In practical applications, it is necessary to consider the mutual influence of multiple pollutants and select the appropriate reagent dosage and injection method. The proposed method has important theoretical significance and application for the development of ZVI repair technology.

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