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SiO2-coated zero-valent iron nanocomposites for aqueous nitrobenzene reduction in groundwater: Performance, reduction mechanism and the effects of hydrogeochemical constituents

Nanoscale zero-valent iron (nZVI) surface modification provides an effective way for in-situ remediation of nitrobenzene (NB) contaminated groundwater. However, it may bring some problems such as secondary pollution and ecotoxicity; moreover, the activity of modified nZVI was also vulnerable to the hydrogeochemical constituents of groundwater (e.g. pH, common ions). SiO2-coating technology is a promising approach to reduce secondary pollution, enhance the biocompatibility and improve the insensitivity of nZVI to the changes of the surrounding environment during contamination degradation process. In this study, the SiO2-coated nZVI composites were prepared and characterized; the microscopic mechanism and performance of NB reduction by SiO2-coated nZVI composites were studied; the effects of hydrogeochemical constituents of groundwater (e.g. pH, common ions) on NB reduction were investigated. The results indicated that SiO2-coating technology provided permeable mesh structure, which could facilitate aqueous NB to contact and react with the internal nZVI; in the reaction process, nitrosobenzene and azoxybenzene were detected as the intermediate and the maximum degradation capacity for thoroughly converting aqueous NB to aniline (AN) was approximately 366.3?mg/g, which was 3.75 times higher than that of bare nZVI. Furthermore, the synthesized composite showed no significantly reactivity restriction in the alkaline (pH, 5?7) groundwater environment; Na+, K+, Cl?, NO3- and SO42- had no effect on the activity of the synthesized composite; Ca2+ and Mg2+ exhibited an inhibitory effect and HCO3- had an enhancement effect on the conversion of NB to AN. Overall, this study demonstrated the superiority of SiO2-coated nZVI composites and provided useful information for the future application in groundwater remediation.

» Author: Haojie Lu, Jun Dong, Mengyue Zhang, Wenhua Hu, Chunyu Wen, Chaoge Yang, Yue Wu

» Reference: 10.1016/j.colsurfa.2018.08.081

» Publication Date: 05/12/2018

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This project has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° [609149].

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